WorldWideScience

Sample records for secondary electron emission

  1. Secondary electron emission from insulators

    International Nuclear Information System (INIS)

    Kanaya, K.; Ono, S.; Ishigaki, F.

    1978-01-01

    The high yield of secondary electron emission from insulators due to electron bombardment may be the result of an increase of the depth of escape. The free-electron scattering theory is applied to the high energy of primary beams, but cannot be applied to the low energy of secondary escaping beams because of the large energy gap of the insulators. The plasmon loss with the valence electron is considered when the secondary electrons escape. Based on the energy retardation power formula of the penetration and energy loss of an electron probe into solid targets, secondary electron emissions from insulators are calculated from the assumptions that the distribution of the secondary electrons due to both incident and back-scattered electrons within the target is isotropic and that it follows the absorption law of the Lenard type. The universal yield-energy curve of the secondary electron emission, which is deduced as a function of three parameters such as ionisation potential, valence electron and the back-scattered coefficient in addition to the free-electron density effect, is found to be in good agreement with the experimental results. (author)

  2. Secondary electron emission from textured surfaces

    Science.gov (United States)

    Huerta, C. E.; Patino, M. I.; Wirz, R. E.

    2018-04-01

    In this work, a Monte Carlo model is used to investigate electron induced secondary electron emission for varying effects of complex surfaces by using simple geometric constructs. Geometries used in the model include: vertical fibers for velvet-like surfaces, tapered pillars for carpet-like surfaces, and a cage-like configuration of interlaced horizontal and vertical fibers for nano-structured fuzz. The model accurately captures the secondary electron emission yield dependence on incidence angle. The model shows that unlike other structured surfaces previously studied, tungsten fuzz exhibits secondary electron emission yield that is independent of primary electron incidence angle, due to the prevalence of horizontally-oriented fibers in the fuzz geometry. This is confirmed with new data presented herein of the secondary electron emission yield of tungsten fuzz at incidence angles from 0-60°.

  3. Secondary emission electron gun using external primaries

    Science.gov (United States)

    Srinivasan-Rao, Triveni [Shoreham, NY; Ben-Zvi, Ilan [Setauket, NY

    2009-10-13

    An electron gun for generating an electron beam is provided, which includes a secondary emitter. The secondary emitter includes a non-contaminating negative-electron-affinity (NEA) material and emitting surface. The gun includes an accelerating region which accelerates the secondaries from the emitting surface. The secondaries are emitted in response to a primary beam generated external to the accelerating region. The accelerating region may include a superconducting radio frequency (RF) cavity, and the gun may be operated in a continuous wave (CW) mode. The secondary emitter includes hydrogenated diamond. A uniform electrically conductive layer is superposed on the emitter to replenish the extracted current, preventing charging of the emitter. An encapsulated secondary emission enhanced cathode device, useful in a superconducting RF cavity, includes a housing for maintaining vacuum, a cathode, e.g., a photocathode, and the non-contaminating NEA secondary emitter with the uniform electrically conductive layer superposed thereon.

  4. Secondary electron emission in nanostructured porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Ruano, G D; Ferron, J; Koropecki, R R, E-mail: gdruano@ceride.gov.a [INTEC-UNL-CONICET, Gueemes 3450 - 3000 Santa Fe (Argentina)

    2009-05-01

    We studied the reversible reduction induced by ion bombardment of the secondary electron emission (SEE) yield. This effect has been modelled as due to changes in dynamically sustained dipoles related with ions and electrons penetration ranges. Such charge configuration precludes the escape of electrons from the nanoporous silicon, making the SEE dependent on the flux of impinging ions. Since this dipolar momentum depends on the electric conduction of the porous medium, by controlled oxidation of the nanoporous structure we change the conduction features of the sample, studying the impact on the SEE reduction effect. Li ion bombardment was also used with the intention of changing the parameters determining the effect. FT-IR and Auger electron spectroscopy were used to characterize the oxidation degree of the samples at different depth scales

  5. Secondary electron emission with molecular projectiles

    International Nuclear Information System (INIS)

    Kroneberger, K.; Rothard, H.; Koschar, P.; Lorenzen, P.; Kemmler, J.; Keller, N.; Maier, R.; Groeneveld, K.O.; Clouvas, A.; Veje, E.

    1990-01-01

    The authors present results for the secondary electron emission (SEE) from thin foil targets, induced by both molecular ions and their atomic constituents as projectiles. The Sternglass theory for kinetic SEE states a proportionality between γ and the electronic stopping power, S e , which has been verified in various experiments. With comparing secondary electron (SE) yields induced by molecular projectiles to those induced by monoatomic projectiles, it is therefore possible to test models for the energy loss of molecular or cluster projectiles. Since the atomic constituents of the molecule are repelled from each other due to Coulomb explosion (superimposed by multiple scattering) while traversing the solid, it is interesting to measure the residual mutual influence on SEE and S e with increasing internuclear separation. This can only be achieved with thin foils, where (as in the present case) the SE-yields from the exit surface can be measured separately. The authors measured the SE-yields from the entrance (γ B ) and exit (γ F ) surfaces of thin C- and Al-foils (150 to 1,000 angstrom) with CO + , C + and O + (15 to 85 keV/u) and H 2 + and H + (0.3 to 1.2 MeV/u). The molecular effect defined as the ratio R(γ) between the yields induced by molecular projectiles and the sum of those induced by their atomic constituents was calculated. The energy dependence of R(γ) can be well represented by the calculated energy loss ratio of di-proton-clusters by Brandt. This supports Brandt's model for the energy loss of clusters

  6. Noise in secondary electron emission: the low yield case

    Czech Academy of Sciences Publication Activity Database

    Frank, Luděk

    2005-01-01

    Roč. 54, č. 4 (2005), s. 361-365 ISSN 0022-0744 R&D Projects: GA AV ČR(CZ) IAA1065304 Keywords : secondary electrons * noise * SEM image noise * secondary emission noise * statistics of secondary electrons * non-Poisson factor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.720, year: 2005

  7. Secondary electron emission from metals and semi-conductor compounds

    International Nuclear Information System (INIS)

    Ono, Susumu; Kanaya, Koichi

    1979-01-01

    Attempt was made to present the sufficient solution of the secondary electron yield of metals and semiconductor compounds except insulators, applying the free electron scattering theory to the absorption of secondary electrons generated within a solid target. The paper is divided into the sections describing absorption coefficient and escape depth, quantitative characteristics of secondary yield, angular distribution of secondary electron emission, effect of incident angle to secondary yield, secondary electron yield transmitted, and lateral distribution of secondary electron emission, besides introduction and conclusion. The conclusions are as follows. Based on the exponential power law for screened atomic potential, secondary electron emission due to both primary and backscattered electrons penetrating into metallic elements and semi-conductive compounds is expressed in terms of the ionization loss in the first collision for escaping secondary electrons. The maximum yield and the corresponding primary energy can both consistently be derived as the functions of three parameters: atomic number, first ionization energy and backscattering coefficient. The yield-energy curve as a function of the incident energy and the backscattering coefficient is in good agreement with the experimental results. The energy dependence of the yield in thin films and the lateral distribution of secondary yield are derived as the functions of the backscattering coefficient and the primary energy. (Wakatsuki, Y.)

  8. Experimental study on secondary electron emission characteristics of Cu

    Science.gov (United States)

    Liu, Shenghua; Liu, Yudong; Wang, Pengcheng; Liu, Weibin; Pei, Guoxi; Zeng, Lei; Sun, Xiaoyang

    2018-02-01

    Secondary electron emission (SEE) of a surface is the origin of the multipacting effect which could seriously deteriorate beam quality and even perturb the normal operation of particle accelerators. Experimental measurements on secondary electron yield (SEY) for different materials and coatings have been developed in many accelerator laboratories. In fact, the SEY is just one parameter of secondary electron emission characteristics which include spatial and energy distribution of emitted electrons. A novel experimental apparatus was set up in China Spallation Neutron Source, and an innovative method was applied to obtain the whole characteristics of SEE. Taking Cu as the sample, secondary electron yield, its dependence on beam injection angle, and the spatial and energy distribution of secondary electrons were achieved with this measurement device. The method for spatial distribution measurement was first proposed and verified experimentally. This contribution also tries to give all the experimental results a reasonable theoretical analysis and explanation.

  9. Secondary electron emission studied by secondary electron energy loss coincidence spectroscopy (SE2ELCS)

    International Nuclear Information System (INIS)

    Khalid, R.

    2013-01-01

    Emission of secondary electrons is of importance in many branches of fundamental and applied science. It is widely applied in the electron microscope for the investigation of the structure and electronic state of solid surfaces and particle detection in electron multiplier devices, and generally it is related to the energy dissipation of energetic particles moving inside a solid. The process of secondary electron emission is a complex physical phenomenon, difficult to measure experimentally and treat theoretically with satisfactory accuracy. The secondary electron spectrum measured with single electron spectroscopy does not provide detailed information of the energy loss processes responsible for the emission of secondary electrons. This information can be accessed when two correlated electron pairs are measured in coincidence and the pair consists of a backscattered electron after a given energy loss and a resulting emitted secondary electron. To investigate the mechanisms responsible for the emission of secondary electrons, a reflection (e,2e) coincidence spectrometer named Secondary Electron Electron Energy Loss Coincidence Spectrometer (SE2ELCS) has been developed in the framework of this thesis which allows one to uncover the relation between the features in the spectra which are due to energy losses and true secondary electron emission structures. The correlated electron pairs are measured with a hemispherical mirror analyzer (HMA) and a time of flight analyzer (TOF) by employing a continuous electron beam. An effort has been made to increase the coincidence count rate by increasing the effective solid angle of the TOF analyzer and optimizing the experimental parameters to get optimum energy resolution. Double differential coincidence spectra for a number of materials namely, nearly free electron metals (Al, Si), noble metals (Ag, Au, Cu, W) and highly oriented pyrolytic graphite (HOPG) have been measured using this coincidence spectrometer. The

  10. Sheath structure transition controlled by secondary electron emission

    Science.gov (United States)

    Schweigert, I. V.; Langendorf, S. J.; Walker, M. L. R.; Keidar, M.

    2015-04-01

    In particle-in-cell Monte Carlo collision (PIC MCC) simulations and in an experiment we study sheath formation over an emissive floating Al2O3 plate in a direct current discharge plasma at argon gas pressure 10-4 Torr. The discharge glow is maintained by the beam electrons emitted from a negatively biased hot cathode. We observe three types of sheaths near the floating emissive plate and the transition between them is driven by changing the negative bias. The Debye sheath appears at lower voltages, when secondary electron emission is negligible. With increasing applied voltage, secondary electron emission switches on and a first transition to a new sheath type, beam electron emission (BEE), takes place. For the first time we find this specific regime of sheath operation near the floating emissive surface. In this regime, the potential drop over the plate sheath is about four times larger than the temperature of plasma electrons. The virtual cathode appears near the emissive plate and its modification helps to maintain the BEE regime within some voltage range. Further increase of the applied voltage U initiates the second smooth transition to the plasma electron emission sheath regime and the ratio Δφs/Te tends to unity with increasing U. The oscillatory behavior of the emissive sheath is analyzed in PIC MCC simulations. A plasmoid of slow electrons is formed near the plate and transported to the bulk plasma periodically with a frequency of about 25 kHz.

  11. Probabilistic model for the simulation of secondary electron emission

    Directory of Open Access Journals (Sweden)

    M. A. Furman

    2002-12-01

    Full Text Available We provide a detailed description of a model and its computational algorithm for the secondary electron emission process. The model is based on a broad phenomenological fit to data for the secondary-emission yield and the emitted-energy spectrum. We provide two sets of values for the parameters by fitting our model to two particular data sets, one for copper and the other one for stainless steel.

  12. Secondary electron emission characteristics of oxide electrodes in flat electron emission lamp

    Directory of Open Access Journals (Sweden)

    Chang-Lin Chiang

    2016-01-01

    Full Text Available The present study concerns with the secondary electron emission coefficient, γ, of the cathode materials used in the newly developed flat electron emission lamp (FEEL devices, which essentially integrates the concept of using cathode for fluorescent lamp and anode for cathode ray tube (CRT to obtain uniform planar lighting. Three different cathode materials, namely fluorine-doped tin oxide (FTO, aluminum oxide coated FTO (Al2O3/FTO and magnesium oxide coated FTO (MgO/FTO were prepared to investigate how the variations of γ and working gases influence the performance of FEEL devices, especially in lowering the breakdown voltage and pressure of the working gases. The results indicate that the MgO/FTO bilayer cathode exhibited a relatively larger effective secondary electron emission coefficient, resulting in significant reduction of breakdown voltage to about 3kV and allowing the device to be operated at the lower pressure to generate the higher lighting efficiency.

  13. Secondary electron emission characteristics of oxide electrodes in flat electron emission lamp

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Chang-Lin, E-mail: CLChiang@itri.org.tw; Li, Chia-Hung [Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Road, Chutung 310, Taiwan (China); Department of Electrophysics, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan (China); Zeng, Hui-Kai [Department of Electronic Engineering, Chung Yuan Christian University, 200 Chung Pei Road, Chung Li 320, Taiwan (China); Li, Jung-Yu, E-mail: JY-Lee@itri.org.tw; Chen, Shih-Pu; Lin, Yi-Ping [Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Road, Chutung 310, Taiwan (China); Hsieh, Tai-Chiung; Juang, Jenh-Yih, E-mail: jyjuang@cc.nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan (China)

    2016-01-15

    The present study concerns with the secondary electron emission coefficient, γ, of the cathode materials used in the newly developed flat electron emission lamp (FEEL) devices, which essentially integrates the concept of using cathode for fluorescent lamp and anode for cathode ray tube (CRT) to obtain uniform planar lighting. Three different cathode materials, namely fluorine-doped tin oxide (FTO), aluminum oxide coated FTO (Al{sub 2}O{sub 3}/FTO) and magnesium oxide coated FTO (MgO/FTO) were prepared to investigate how the variations of γ and working gases influence the performance of FEEL devices, especially in lowering the breakdown voltage and pressure of the working gases. The results indicate that the MgO/FTO bilayer cathode exhibited a relatively larger effective secondary electron emission coefficient, resulting in significant reduction of breakdown voltage to about 3kV and allowing the device to be operated at the lower pressure to generate the higher lighting efficiency.

  14. Secondary electron emission yield on poled silica based thick films

    DEFF Research Database (Denmark)

    Braga, D.; Poumellec, B.; Cannas, V.

    2004-01-01

    Studies on the distribution of the electric field produced by a thermal poling process in a layer of Ge-doped silica on silicon substrate, by using secondary electron emission yield (SEEY) measurements () are presented. Comparing 0 between poled and unpoled areas, the SEEY at the origin of electr...

  15. Secondary Electron Emission from Dust and Its Effect on Charging

    Science.gov (United States)

    Saikia, B. K.; Kakati, B.; Kausik, S. S.; Bandyopadhyay, M.

    2011-11-01

    Hydrogen plasma is produced in a plasma chamber by striking discharge between incandescent tungsten filaments and the permanent magnetic cage [1], which is grounded. The magnetic cage has a full line cusped magnetic field geometry used to confine the plasma elements. A cylindrical Langmuir probe is used to study the plasma parameters in various discharge conditions. The charge accumulated on the dust particles is calculated using the capacitance model and the dust current is measured by the combination of a Faraday cup and an electrometer at different discharge conditions. It is found Secondary electron emission from dust having low emission yield effects the charging of dust particles in presence of high energetic electrons.

  16. Secondary Electron Emission from Dust and Its Effect on Charging

    International Nuclear Information System (INIS)

    Saikia, B. K.; Kakati, B.; Kausik, S. S.; Bandyopadhyay, M.

    2011-01-01

    Hydrogen plasma is produced in a plasma chamber by striking discharge between incandescent tungsten filaments and the permanent magnetic cage [1], which is grounded. The magnetic cage has a full line cusped magnetic field geometry used to confine the plasma elements. A cylindrical Langmuir probe is used to study the plasma parameters in various discharge conditions. The charge accumulated on the dust particles is calculated using the capacitance model and the dust current is measured by the combination of a Faraday cup and an electrometer at different discharge conditions. It is found Secondary electron emission from dust having low emission yield effects the charging of dust particles in presence of high energetic electrons.

  17. Simulation and analysis of secondary emission microwave electron gun

    International Nuclear Information System (INIS)

    He Wencan; Pei Yuanji; Jin Kai; Wu Congfeng

    2001-01-01

    The development of high-current, short-duration pulses of electrons has been a challenging problem for many year. Micro-pulse-gun (MPG) is a novel concept that employs the resonant amplification of an electron current by secondary electron emission in a RE cavity. Using the computation code URMEL-T, several kinds of RF cavities under the frequency of 2856 MHz were calculated and optimized, the magnetic and electric field distribution in them were got. Through particle-in-cell (PIC) simulation, the self-bunching process in a MPG was proved, the relationship between the cavity length and selected phase and the relationship between the peak electric field and selected phase were got. With cathode material of high secondary emission coefficient, the MPG can produce high current densities (1132-5303 A/cm 2 ) and short pulses (3.15-10 ps)

  18. Modified Sternglass theory for the emission of secondary electrons by fast-electron impact

    International Nuclear Information System (INIS)

    Suszcynsky, D.M.; Borovsky, J.E.

    1992-01-01

    The Sternglass theory [Sternglass, Phys. Rev. 108, 1 (1957)] for fast-ion-induced secondary-electron emission from metals has been modified to predict the secondary-electron yield from metals impacted by energetic (several keV to about 200 keV) electrons. The primary modification of the theory accounts for the contribution of the backscattered electrons to the production of secondary electrons based on a knowledge of the backscattered-electron energy distribution. The modified theory is in reasonable agreement with recent experimental data from gold targets in the 6--30-keV electron energy range

  19. Secondary electron emission from lithium and lithium compounds

    Energy Technology Data Exchange (ETDEWEB)

    Capece, A. M., E-mail: capecea@tcnj.edu [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Department of Physics, The College of New Jersey, Ewing, New Jersey 08628 (United States); Patino, M. I.; Raitses, Y. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Koel, B. E. [Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540 (United States)

    2016-07-04

    In this work, measurements of electron-induced secondary electron emission (SEE) yields of lithium as a function of composition are presented. The results are particularly relevant for magnetic fusion devices such as tokamaks, field-reversed configurations, and stellarators that consider Li as a plasma-facing material for improved plasma confinement. SEE can reduce the sheath potential at the wall and cool electrons at the plasma edge, resulting in large power losses. These effects become significant as the SEE coefficient, γ{sub e}, approaches one, making it imperative to maintain a low yield surface. This work demonstrates that the yield from Li strongly depends on chemical composition and substantially increases after exposure to oxygen and water vapor. The total yield was measured using a retarding field analyzer in ultrahigh vacuum for primary electron energies of 20–600 eV. The effect of Li composition was determined by introducing controlled amounts of O{sub 2} and H{sub 2}O vapor while monitoring film composition with Auger electron spectroscopy and temperature programmed desorption. The results show that the energy at which γ{sub e} = 1 decreases with oxygen content and is 145 eV for a Li film that is 17% oxidized and drops to less than 25 eV for a fully oxidized film. This work has important implications for laboratory plasmas operating under realistic vacuum conditions in which oxidation significantly alters the electron emission properties of Li walls.

  20. Secondary electron emission from lithium and lithium compounds

    International Nuclear Information System (INIS)

    Capece, A. M.; Patino, M. I.; Raitses, Y.; Koel, B. E.

    2016-01-01

    In this work, measurements of electron-induced secondary electron emission (SEE) yields of lithium as a function of composition are presented. The results are particularly relevant for magnetic fusion devices such as tokamaks, field-reversed configurations, and stellarators that consider Li as a plasma-facing material for improved plasma confinement. SEE can reduce the sheath potential at the wall and cool electrons at the plasma edge, resulting in large power losses. These effects become significant as the SEE coefficient, γ e , approaches one, making it imperative to maintain a low yield surface. This work demonstrates that the yield from Li strongly depends on chemical composition and substantially increases after exposure to oxygen and water vapor. The total yield was measured using a retarding field analyzer in ultrahigh vacuum for primary electron energies of 20–600 eV. The effect of Li composition was determined by introducing controlled amounts of O 2 and H 2 O vapor while monitoring film composition with Auger electron spectroscopy and temperature programmed desorption. The results show that the energy at which γ e  = 1 decreases with oxygen content and is 145 eV for a Li film that is 17% oxidized and drops to less than 25 eV for a fully oxidized film. This work has important implications for laboratory plasmas operating under realistic vacuum conditions in which oxidation significantly alters the electron emission properties of Li walls.

  1. Secondary Electron Emission Yields from PEP-II Accelerator Materials

    International Nuclear Information System (INIS)

    Kirby, Robert E.

    2000-01-01

    The PEP-II B-Factory at SLAC operates with aluminum alloy and copper vacuum chambers, having design positron and electron beam currents of 2 and 1 A, respectively. Titanium nitride coating of the aluminum vacuum chamber in the arcs of the positron ring is needed in order to reduce undesirable electron-cloud effects. The total secondary electron emission yield of TiN-coated aluminum alloy has been measured after samples of beam chamber material were exposed to air and again after electron-beam bombardment, as a function of incident electron beam angle and energy. The results may be used to simulate and better understand electron-cloud effects under actual operating conditions. We also present yield measurements for other accelerator materials because new surface effects are expected to arise as beam currents increase. Copper, in particular, is growing in popularity for its good thermal conductivity and self-radiation-shielding properties. The effect of electron bombardment, ''conditioning'', on the yield of TiN and copper is shown

  2. Secondary Electron Emission Beam Loss Monitor for LHC

    CERN Document Server

    Dehning, B; Holzer, E B; Kramer, Daniel

    2008-01-01

    Beam Loss Monitoring (BLM) system is a vital part of the active protection of the LHC accelerators' elements. It should provide the number of particles lost from the primary hadron beam by measuring the radiation field induced by their interaction with matter surrounding the beam pipe. The LHC BLM system will use ionization chambers as standard detectors but in the areas where very high dose rates are expected, the Secondary Emission Monitor (SEM) chambers will be employed because of their high linearity, low sensitivity and fast response. The SEM needs a high vacuum for proper operation and has to be functional for up to 20 years, therefore all the components were designed according to the UHV requirements and a getter pump was included. The SEM electrodes are made of Ti because of its Secondary Emission Yield (SEY) stability. The sensitivity of the SEM was modeled in Geant4 via the Photo-Absorption Ionization module together with custom parameterization of the very low energy secondary electron production. ...

  3. Secondary electron emission and its role in the space environment

    Science.gov (United States)

    Němeček, Z.; Pavlů, J.; Richterová, I.; Šafránková, J.; Vaverka, J.

    2018-01-01

    The role of dust in the space environment is of increasing interest in recent years and also the fast development of fusion devices with a magnetic confinement brought new issues in the plasma-surface interaction. Among other processes, secondary electron emission plays an important role for dust charging in interplanetary space and its importance increases at and above the surfaces of airless bodies like planets, moons, comets or asteroids. A similar situation can be found in many industrial applications where the dust is a final product or an unintentional impurity. The present paper reviews the progress in laboratory investigations of the secondary emission process as well as an evolution of the modeling of the interaction of energetic electrons with dust grains of different materials and sizes. The results of the model are discussed in view of latest laboratory simulations and they are finally applied on the estimation of an interaction of the solar wind and magnetospheric plasmas with the dust attached to or levitating above the lunar surface.

  4. Secondary electron emission anisotropy in oblique incidence of electrons on the (100) Mo

    International Nuclear Information System (INIS)

    Gomoyunova, M.V.; Zaslavskij, S.L.; Pronin, I.I.

    1978-01-01

    Studied was the influence of azimuthal plane of incidence of primary particles with energies of 0.5-1.5 keV on the secondary electron emission of the (100) Mo face at the constant polar angle of 45 deg. The measurements were carried out in vacuum of (2-4)x10 -10 torr by modulation technique. It is shown that anisotropy is peculiar to the secondary electron emission of all energies. The anisotropy of emission has two maxima; the high-energy maximum connected with reflected primary electrons and situated near the elastically reflected electrons and weaker pronounced the low-energy one which is found at energies of 100-200 eV and is conditioned by truly secondary electrons. It is shown that the anisotropy, characterizing secondary electrons responsible for the appearance of structure in spectrum, particularly the Auger electrons and the electrons suffering ionizing energy losses, exceeds the anisotropy of continuous spectrum electrons possessing the same energy. The electron diffraction dynamic theory, based on the conception of the united wave field of electrons, has been used to explain the regularities stated

  5. Secondary emission of negative ions and electrons resulting from electronic sputtering of cesium salts

    International Nuclear Information System (INIS)

    Allali, H.; Nsouli, B.; Thomas, J.P.

    1993-04-01

    Secondary ion emission of negative ions and electrons from alkali salts bombarded with high energy (9 MeV) Ar +++ is discussed. Quite different features are observed according to the nature of the salt investigated (halide or oxygenated). In the case of cesium, the electron emission from halides is characterized by intense electron showers (several hundred electrons) with narrow distributions in intensity and orientation. Conversely, for oxygenated salts, these distributions are broader, much less intense (one order of magnitude), and the ion emission exhibits an dissymmetry, which has never been observed for inorganics. This last result is interpreted in terms of radiolysis of the oxygenated salt, a process well documented for gamma-ray irradiation, but not yet reported in secondary ion emission. (author) 17 refs.; 10 figs

  6. Secondary electron emission induced by channeled relativistic electrons in a (1 1 0) Si crystal

    International Nuclear Information System (INIS)

    Korotchenko, K.B.; Kunashenko, Yu P.; Tukhfatullin, T.A.

    2012-01-01

    A new effect that accompanies electrons channeled in a crystal is considered. This phenomenon was previously predicted was called channeling secondary electron emission (CSEE). The exact CSEE cross-section on the basis of using the exact Bloch wave function of electron channeled in a crystal is obtained. The detailed investigation of CSEE cross-section is performed. It is shown that angular distribution of electrons emitted due to CSEE has a complex form.

  7. Secondary electron emission yield in the limit of low electron energy

    CERN Document Server

    Andronov, A.N.; Kaganovich, I.D.; Startsev, E.A.; Raitses, Y.; Demidov, V.I.

    2013-04-22

    Secondary electron emission (SEE) from solids plays an important role in many areas of science and technology.1 In recent years, there has been renewed interest in the experimental and theoretical studies of SEE. A recent study proposed that the reflectivity of very low energy electrons from solid surface approaches unity in the limit of zero electron energy2,3,4, If this was indeed the case, this effect would have profound implications on the formation of electron clouds in particle accelerators,2-4 plasma measurements with electrostatic Langmuir probes, and operation of Hall plasma thrusters for spacecraft propulsion5,6. It appears that, the proposed high electron reflectivity at low electron energies contradicts to numerous previous experimental studies of the secondary electron emission7. The goal of this note is to discuss possible causes of these contradictions.

  8. Secondary Electron Emission from Plasma Processed Accelerating Cavity Grade Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Basovic, Milos [Old Dominion Univ., Norfolk, VA (United States)

    2016-05-01

    Advances in the particle accelerator technology have enabled numerous fundamental discoveries in 20th century physics. Extensive interdisciplinary research has always supported further development of accelerator technology in efforts of reaching each new energy frontier. Accelerating cavities, which are used to transfer energy to accelerated charged particles, have been one of the main focuses of research and development in the particle accelerator field. Over the last fifty years, in the race to break energy barriers, there has been constant improvement of the maximum stable accelerating field achieved in accelerating cavities. Every increase in the maximum attainable accelerating fields allowed for higher energy upgrades of existing accelerators and more compact designs of new accelerators. Each new and improved technology was faced with ever emerging limiting factors. With the standard high accelerating gradients of more than 25 MV/m, free electrons inside the cavities get accelerated by the field, gaining enough energy to produce more electrons in their interactions with the walls of the cavity. The electron production is exponential and the electron energy transfer to the walls of a cavity can trigger detrimental processes, limiting the performance of the cavity. The root cause of the free electron number gain is a phenomenon called Secondary Electron Emission (SEE). Even though the phenomenon has been known and studied over a century, there are still no effective means of controlling it. The ratio between the electrons emitted from the surface and the impacting electrons is defined as the Secondary Electron Yield (SEY). A SEY ratio larger than 1 designates an increase in the total number of electrons. In the design of accelerator cavities, the goal is to reduce the SEY to be as low as possible using any form of surface manipulation. In this dissertation, an experimental setup was developed and used to study the SEY of various sample surfaces that were treated

  9. Secondary electron emission from plasma processed accelerating cavity grade niobium

    Science.gov (United States)

    Basovic, Milos

    Advances in the particle accelerator technology have enabled numerous fundamental discoveries in 20th century physics. Extensive interdisciplinary research has always supported further development of accelerator technology in efforts of reaching each new energy frontier. Accelerating cavities, which are used to transfer energy to accelerated charged particles, have been one of the main focuses of research and development in the particle accelerator field. Over the last fifty years, in the race to break energy barriers, there has been constant improvement of the maximum stable accelerating field achieved in accelerating cavities. Every increase in the maximum attainable accelerating fields allowed for higher energy upgrades of existing accelerators and more compact designs of new accelerators. Each new and improved technology was faced with ever emerging limiting factors. With the standard high accelerating gradients of more than 25 MV/m, free electrons inside the cavities get accelerated by the field, gaining enough energy to produce more electrons in their interactions with the walls of the cavity. The electron production is exponential and the electron energy transfer to the walls of a cavity can trigger detrimental processes, limiting the performance of the cavity. The root cause of the free electron number gain is a phenomenon called Secondary Electron Emission (SEE). Even though the phenomenon has been known and studied over a century, there are still no effective means of controlling it. The ratio between the electrons emitted from the surface and the impacting electrons is defined as the Secondary Electron Yield (SEY). A SEY ratio larger than 1 designates an increase in the total number of electrons. In the design of accelerator cavities, the goal is to reduce the SEY to be as low as possible using any form of surface manipulation. In this dissertation, an experimental setup was developed and used to study the SEY of various sample surfaces that were treated

  10. Effect of secondary electron emission on the Jeans instability in a dusty plasma

    International Nuclear Information System (INIS)

    Sarkar, Susmita; Roy, Banamali; Maity, Saumyen; Khan, Manoranjan; Gupta, M. R.

    2007-01-01

    In this paper the effect of secondary electron emission on Jeans instability in a dusty plasma has been investigated. Due to secondary electron emission, dust grains may have two stable equilibrium states out of which one is negative and the other is positive. Here both cases have been considered separately. It has been shown that secondary electron emission enhances Jeans instability when equilibrium dust charge is negative. It has also been shown that growth rate of Jeans instability reduces with increasing secondary electron emission when equilibrium dust charge is positive

  11. Measurements of the Secondary Electron Emission of Some Insulators

    CERN Document Server

    Bozhko, Y.; Hilleret, N.

    2013-01-01

    Charging up the surface of an insulator after beam impact can lead either to reverse sign of field between the surface and collector of electrons for case of thick sample or appearance of very high internal field for thin films. Both situations discard correct measurements of secondary electron emission (SEE) and can be avoided via reducing the beam dose. The single pulse method with pulse duration of order of tens microseconds has been used. The beam pulsing was carried out by means of an analog switch introduced in deflection plate circuit which toggles its output between "beam on" and "beam off" voltages depending on level of a digital pulse. The error in measuring the beam current for insulators with high value of SEE was significantly reduced due to the use for this purpose a titanium sample having low value of the SEE with DC method applied. Results obtained for some not coated insulators show considerable increase of the SEE after baking out at 3500C what could be explained by the change of work functi...

  12. Ionizing device comprising a microchannel electron multiplier with secondary electron emission

    International Nuclear Information System (INIS)

    Chalmeton, Vincent.

    1974-01-01

    The present invention relates to a ionizing device comprising a microchannel electron multiplier involving secondary electron emission as a means of ionization. A system of electrodes is used to accelerate said electrons, ionize the gas and extract the ions from thus created plasma. Said ionizer is suitable for bombarding the target in neutron sources (target of the type of nickel molybdenum coated with tritiated titanium or with a tritium deuterium mixture) [fr

  13. Transport Theory for Kinetic Emission of Secondary Electrons from Solids

    DEFF Research Database (Denmark)

    Schou, Jørgen

    1980-01-01

    a solid is derived. To find the former, existing computations for ion slowing down and experimental and theoretical ones for electron bombardment can be utilized. The energy and angular distribution of the secondary electrons and the secondary electron yield are both expressed as products of the deposited...... in the keV region is largely taken into account. The predicted energy and angular distribution agree with absolute spectra for incident electrons, whereas the agreement with absolute spectra for incident protons is less satisfactory. Extrapolation of the energy distribution down to the vacuum level gives...

  14. Mechanism of enhancement of controllable secondary-electron emission from fast single electrons

    International Nuclear Information System (INIS)

    Lorikyan, M.P.; Kavalov, R.L.; Trofimchuk, N.N.; Arvanov, A.N.; Gavalyan, V.G.

    For porous KCl films (density approximately 2 percent, thickness 50-400 μm), the controllable secondary electron emission (CSEE) from fast single electrons with energies of 0.7-2 MeV was studied. An electric field E of approximately 10 4 -10 5 V/cm was set up inside the porous films and the emission curves anti sigma = f(E) and the energy spectra of the secondary electrons were measured. The mean emission coefficient anti sigma increases with increasing E, reaching a value of anti sigma approximately equal to 230. Internal enhancement of CSEE under the action of the E field is explained by a process similar to the Townsend semi-self-maintained discharge in gases. The mean free path L/sub e/ of the secondary electrons estimated on the basis of this mechanism of CSEE enhancement is in good agreement with the L/sub e/ value obtained independently from the energy spectra of the secondary electrons. The report examines the effect of the first critical potential U/sub il/ and of the electron affinity of the dielectric α on the formation of CSEE from a porous dielectric film. The possibility of using such films in particle detectors is discussed

  15. Characteristics of a cold cathode electron source combined with secondary electron emission in a FED

    International Nuclear Information System (INIS)

    Lei Wei; Zhang Xiaobing; Zhou Xuedong; Zhu Zuoya; Lou Chaogang; Zhao Hongping

    2005-01-01

    In electron beam devices, the voltage applied to the cathode (w.r.t. grid voltage) provides the initial energy for the electrons. Based on the type of electron emission, the electron sources are (mainly) classified into thermionic cathodes and cold cathodes. The power consumption of a cold cathode is smaller than that of a thermionic cathode. The delay time of the electron emission from a cold cathode following the voltage rise is also smaller. In cathode ray tubes, field emission display (=FED) panels and other devices, the electron current emitted from the cathode needs to be modulated. Since the strong electric field, which is required to extract electrons from the cold cathode, accelerates the electrons to a high velocity near the gate electrode, the required voltage swing for the current modulation is also high. The design of the driving circuit becomes quite difficult and expensive for a high driving voltage. In this paper, an insulator plate with holes is placed in front of a cold cathode. When the primary electrons hit the surface of the insulator tunnels, secondary electrons are generated. In this paper, the characteristics of the secondary electrons emitted from the gate structure are studied. Because the energies of the secondary electrons are smaller than that of the primary electron, the driving voltage for the current modulation is decreased by the introduction of the insulator tunnels, resulting in an improved energy uniformity of the electron beam. Triode structures with inclined insulator tunnels and with double insulator plates are also fabricated and lead to further improvements in the energy uniformity. The improved energy uniformity predicted by the simulation calculations is demonstrated by the improved brightness uniformity in the screen display images

  16. Secondary Electron Emission Materials for Transmission Dynodes in Novel Photomultipliers: A Review

    Directory of Open Access Journals (Sweden)

    Shu Xia Tao

    2016-12-01

    Full Text Available Secondary electron emission materials are reviewed with the aim of providing guidelines for the future development of novel transmission dynodes. Materials with reflection secondary electron yield higher than three and transmission secondary electron yield higher than one are tabulated for easy reference. Generations of transmission dynodes are listed in the order of the invention time with a special focus on the most recent atomic-layer-deposition synthesized transmission dynodes. Based on the knowledge gained from the survey of secondary election emission materials with high secondary electron yield, an outlook of possible improvements upon the state-of-the-art transmission dynodes is provided.

  17. Monte Carlo calculation of secondary electron emission from carbon-surface by obliquely incident particles

    International Nuclear Information System (INIS)

    Ohya, Kaoru; Kawata, Jun; Mori, Ichiro

    1990-01-01

    Incidence angle dependences of secondary electron emission from a carbon surface by low energy electron and hydrogen atom are calculated using Monte Carlo simulations on the kinetic emission model. The calculation shows very small increase or rather decrease of the secondary electron yield with oblique incidence. It is explained in terms of not only multiple elastic collisions of incident particles with the carbon atoms but also small penetration depth of the particles comparable with the escape depth of secondary electrons. In addition, the two types of secondary electron emission are distinguished by using the secondary electron yield statistics; one is the emission due to trapped particles in the carbon, and the other is that due to backscattered particles. The high-yield component of the statistics on oblique incidence is more suppressed than those on normal incidence. (author)

  18. Effect of Secondary Electron Emission on Electron Cross-Field Current in E×B Discharges

    Energy Technology Data Exchange (ETDEWEB)

    Yevgeny Raitses, Igor D. Kaganovich, Alexander Khrabrov, Dmytro Sydorenko, Nathaniel J. Fisch and Andrei Smolyakov

    2011-02-10

    This paper reviews and discusses recent experimental, theoretical, and numerical studies of plasma-wall interaction in a weakly collisional magnetized plasma bounded with channel walls made from different materials. A lowpressure ExB plasma discharge of the Hall thruster was used to characterize the electron current across the magnetic field and its dependence on the applied voltage and electron-induced secondary electron emission (SEE) from the channel wall. The presence of a depleted, anisotropic electron energy distribution function with beams of secondary electrons was predicted to explain the enhancement of the electron cross-field current observed in experiments. Without the SEE, the electron crossfield transport can be reduced from anomalously high to nearly classical collisional level. The suppression of SEE was achieved using an engineered carbon velvet material for the channel walls. Both theoretically and experimentally, it is shown that the electron emission from the walls can limit the maximum achievable electric field in the magnetized plasma. With nonemitting walls, the maximum electric field in the thruster can approach a fundamental limit for a quasineutral plasma.

  19. Effect of Secondary Electron Emission on Electron Cross-Field Current in E x B Discharges

    International Nuclear Information System (INIS)

    Raitses, Yevgeny; Kaganovich, Igor D.; Khrabrov, Alexander; Sydorenko, Dmytro; Fisch, Nathaniel J.; Smolyakov, Andrei

    2011-01-01

    This paper reviews and discusses recent experimental, theoretical, and numerical studies of plasma-wall interaction in a weakly collisional magnetized plasma bounded with channel walls made from different materials. A lowpressure ExB plasma discharge of the Hall thruster was used to characterize the electron current across the magnetic field and its dependence on the applied voltage and electron-induced secondary electron emission (SEE) from the channel wall. The presence of a depleted, anisotropic electron energy distribution function with beams of secondary electrons was predicted to explain the enhancement of the electron cross-field current observed in experiments. Without the SEE, the electron crossfield transport can be reduced from anomalously high to nearly classical collisional level. The suppression of SEE was achieved using an engineered carbon velvet material for the channel walls. Both theoretically and experimentally, it is shown that the electron emission from the walls can limit the maximum achievable electric field in the magnetized plasma. With nonemitting walls, the maximum electric field in the thruster can approach a fundamental limit for a quasineutral plasma.

  20. Monte Carlo simulations of secondary electron emission due to ion beam milling

    Energy Technology Data Exchange (ETDEWEB)

    Mahady, Kyle [Univ. of Tennessee, Knoxville, TN (United States); Tan, Shida [Intel Corp., Santa Clara, CA (United States); Greenzweig, Yuval [Intel Israel Ltd., Haifa (Israel); Livengood, Richard [Intel Corp., Santa Clara, CA (United States); Raveh, Amir [Intel Israel Ltd., Haifa (Israel); Fowlkes, Jason D. [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Rack, Philip [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-07-01

    We present a Monte Carlo simulation study of secondary electron emission resulting from focused ion beam milling of a copper target. The basis of this study is a simulation code which simulates ion induced excitation and emission of secondary electrons, in addition to simulating focused ion beam sputtering and milling. This combination of features permits the simulation of the interaction between secondary electron emission, and the evolving target geometry as the ion beam sputters material. Previous ion induced SE Monte Carlo simulation methods have been restricted to predefined target geometries, while the dynamic target in the presented simulations makes this study relevant to image formation in ion microscopy, and chemically assisted ion beam etching, where the relationship between sputtering, and its effects on secondary electron emission, is important. We focus on a copper target, and validate our simulation against experimental data for a range of: noble gas ions, ion energies, ion/substrate angles and the energy distribution of the secondary electrons. We then provide a detailed account of the emission of secondary electrons resulting from ion beam milling; we quantify both the evolution of the yield as high aspect ratio valleys are milled, as well as the emission of electrons within these valleys that do not escape the target, but which are important to the secondary electron contribution to chemically assisted ion induced etching.

  1. Secondary electron emission from 0.5--2.5-MeV protons and deuterons

    International Nuclear Information System (INIS)

    Thornton, T.A.; Anno, J.N.

    1977-01-01

    Measurement of the secondary electron currents leaving Al, V, Fe, 316 stainless steel, Nb, and Mo foils undergoing 0.5--2.5-MeV proton and deuteron bombardment were made to determine the secondary electron emission ratios for these ions. The measured secondary electron yields were of the order of 1.0, with the deuterons producing generally higher yields than the protons

  2. On the regularities of gamma-ray initiated emission of really-secondary electrons

    International Nuclear Information System (INIS)

    Grudskij, M.Ya.; Roldugin, N.N.; Smirnov, V.V.

    1982-01-01

    Emission regularities of the really-secondary electrons from metals are discussed on the basis of experimental data on electron emission characteristics under gamma radiation of incident quanta produced for a wide energy range (Esub(γ)=0.03+-2 MeV) and atomic numbers of target materials (Z=13+-79). Comparison with published experimental and calculated data is performed. It is shown that yield of the really-secondary electrons into vacuum from the target surface bombarded with a normally incident collimated beam of gamma radiation calculating on energy unit absorbed in the yield zone of the really-secondary electrons is determined only with the target material emittivity and can be calculated if spatial-energy distributions and the number of secondary fast electrons emitted out of the target are known

  3. Secondary electron images obtained with a standard photoelectron emission microscope set-up

    International Nuclear Information System (INIS)

    Benka, Oswald; Zeppenfeld, Peter

    2005-01-01

    The first results of secondary electron images excited by 3-4.3 keV electrons are presented. The images are obtained with a standard FOCUS-PEEM set-up equipped with an imaging energy filter (IEF). The electron gun was mounted on a standard PEEM entrance flange at an angle of 25 deg. with respect to the sample surface. A low extraction voltage of 500 V was used to minimize the deflection of the electron beam by the PEEM extraction electrode. The secondary electron images are compared to photoelectron images excited by a standard 4.9 eV UV lamp. In the case of a Cu pattern on a Si substrate it is found that the lateral resolution without the IEF is about the same for electron and photon excitation but that the relative electron emission intensities are very different. The use of the IEF reduces the lateral resolution. Images for secondary electron energies between eV 1 and eV 2 were obtained by setting the IEF to -V 1 and -V 2 ∼-(V 1 +5V) potentials and taking the difference of both images. Images up to 100 eV electron energies were recorded. The material contrast obtained in these difference images is discussed in terms of a secondary electron and photoelectron emission model and secondary electron energy spectra measured with a LEED-Auger spectrometer

  4. Heavy-ion induced secondary electron emission from Mg, Al, and Si partially covered with oxygen

    International Nuclear Information System (INIS)

    Weng, J; Veje, E.

    1984-01-01

    We have bombarded Mg, Al, and Si with 80 keV Ar + ions and measured the secondary electron emission yields at projectile incidence angles from 0 0 to 85 0 , with oxygen present at the target as well as under UHV conditions. The total secondary electron emission yields are found to depend fairly much on the amount of oxygen present. The three elements studied show relatively large individual variations. For all three elements, and with as well as without oxygen present, the relative secondary electron emission yield is observed to vary as 1/cos v, where v is the angle of incidence of the projectiles. This seems to indicate that the secondary electron production is initiated uniformly along the projectile path in the solid, in a region close to the surface. The results are discussed, and it is tentatively suggested, that the increase in secondary electron emission, caused by the presence of oxygen, originates from neutralization of sputtered oxygen, which initially is sitting as O 2- ions. (orig.)

  5. LUNAR DUST GRAIN CHARGING BY ELECTRON IMPACT: COMPLEX ROLE OF SECONDARY ELECTRON EMISSIONS IN SPACE ENVIRONMENTS

    International Nuclear Information System (INIS)

    Abbas, M. M.; Craven, P. D.; LeClair, A. C.; Spann, J. F.; Tankosic, D.

    2010-01-01

    Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with radiation from nearby sources, or by electron/ion collisions by sticking or secondary electron emissions (SEEs). The high vacuum environment on the lunar surface leads to some unusual physical and dynamical phenomena involving dust grains with high adhesive characteristics, and levitation and transportation over long distances. Knowledge of the dust grain charges and equilibrium potentials is important for understanding a variety of physical and dynamical processes in the interstellar medium, and heliospheric, interplanetary/planetary, and lunar environments. It has been well recognized that the charging properties of individual micron-/submicron-size dust grains are expected to be substantially different from the corresponding values for bulk materials. In this paper, we present experimental results on the charging of individual 0.2-13 μm size dust grains selected from Apollo 11 and 17 dust samples, and spherical silica particles by exposing them to mono-energetic electron beams in the 10-200 eV energy range. The dust charging process by electron impact involving the SEEs discussed is found to be a complex charging phenomenon with strong particle size dependence. The measurements indicate substantial differences between the polarity and magnitude of the dust charging rates of individual small-size dust grains, and the measurements and model properties of corresponding bulk materials. A more comprehensive plan of measurements of the charging properties of individual dust grains for developing a database for realistic models of dust charging in astrophysical and lunar environments is in progress.

  6. Lunary Dust Grain Charging by Electron Impact: Complex Role of Secondary Electron Emissions in Space Environments

    Science.gov (United States)

    Abbas, M. M.; Tankosic, D.; Crave, P. D.; LeClair, A.; Spann, J. F.

    2010-01-01

    Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with radiation from nearby sources, or by electron/ion collisions by sticking or secondary electron emissions (SEES). The high vacuum environment on the lunar surface leads to some unusual physical and dynamical phenomena involving dust grains with high adhesive characteristics, and levitation and transportation over long distances. Knowledge of the dust grain charges and equilibrium potentials is important for understanding a variety of physical and dynamical processes in the interstellar medium, and heliospheric, interplanetary/ planetary, and lunar environments. It has been well recognized that the charging properties of individual micron-/submicron-size dust grains are expected to be substantially different from the corresponding values for bulk materials. In this paper, we present experimental results on the charging of individual 0.2-13 m size dust grains selected from Apollo 11 and 17 dust samples, and spherical silica particles by exposing them to mono-energetic electron beams in the 10-200 eV energy range. The dust charging process by electron impact involving the SEES discussed is found to be a complex charging phenomenon with strong particle size dependence. The measurements indicate substantial differences between the polarity and magnitude of the dust charging rates of individual small-size dust grains, and the measurements and model properties of corresponding bulk materials. A more comprehensive plan of measurements of the charging properties of individual dust grains for developing a database for realistic models of dust charging in astrophysical and lunar environments is in progress.

  7. High-stable secondary-emission monitor for accelerated electron beam current

    International Nuclear Information System (INIS)

    Prudnikov, I.A.; Saksaganskij, G.L.; Bazhanov, E.B.; Zabrodin, B.V.

    1977-01-01

    A secondary-emission monitor for a 10 to 30 MeV electron beam (beam current is 10 -4 to 10 -2 A) is described. The monitor comprises a measuring electrode unit, titanium discharge-type pump, getter made of porous titanium, all enclosed in a metal casing. The measuring unit comprises three electrodes made of 20 μm aluminium foil. The secondary emission coefficient (5.19%+-0.06% for the electron energy of 20 MeV) is maintained stable for a long time. The monitor detects pulses of up to some nanoseconds duration. It is reliable in operation, and is recommended for a wide practical application

  8. Relations of secondary electron emission to microdosimetry and applications to two-target theory

    International Nuclear Information System (INIS)

    Forsberg, B.J.; Burlin, T.E.

    1978-01-01

    Secondary electron emission has been suggested as a phenomenon that offers considerable potential for microdosimetric studies (Burlin, 1973). This potential is examined further through a theoretical study. Previous work on the stochastic nature of secondary electron emission is reviewed and in particular a Monte Carlo programme of McDonald, Lamki and Delaney (1971, 1973) is developed. Lineal energy distributions are presented for tissue equivalent volumes of about 5nm in three materials for different electron energies. The dose mean of lineal energy and the frequency mean of lineal energy are calculated and these results for volumes with linear dimension of a few nanometers are compared with results of Bengtsson and Lindborg (1974), Braby and Ellett (1971) and Dvorak (1975). Several authors have suggested that some radiobiological effects may result from energy deposition in two different targets. An experimental investigation using proportional counter measurements to simulate two-target theory has been reported. In this paper an alternative technique to twin-proportional counter measurements, based on the secondary electron emission from the two sides of a thin foil is discussed. The extended version of the programme calculates the coincident P(nsub(i),nsub(e)) distribution, that is the number of secondary electrons pair (nsub(i), nsub(e)) is recorded, where nsub(i) is the number of secondary electrons leaving the incident side and nsub(e) is leaving the exit side of the foil simultaneously

  9. Measurement of the secondary electron emission from CVD diamond films using phosphor screen detectors

    Science.gov (United States)

    Vaz, R.; May, P. W.; Fox, N. A.; Harwood, C. J.; Chatterjee, V.; Smith, J. A.; Horsfield, C. J.; Lapington, J. S.; Osbourne, S.

    2015-03-01

    Diamond-based photomultipliers have the potential to provide a significant improvement over existing devices due to diamond's high secondary electron yield and narrow energy distribution of secondary electrons which improves energy resolution creating extremely fast response times. In this paper we describe an experimental apparatus designed to study secondary electron emission from diamond membranes only 400 nm thick, observed in reflection and transmission configurations. The setup consists of a system of calibrated P22 green phosphor screens acting as radiation converters which are used in combination with photomultiplier tubes to acquire secondary emission yield data from the diamond samples. The superior signal voltage sampling of the phosphor screen setup compared with traditional Faraday Cup detection allows the variation in the secondary electron yield across the sample to be visualised, allowing spatial distributions to be obtained. Preliminary reflection and transmission yield data are presented as a function of primary electron energy for selected CVD diamond films and membranes. Reflection data were also obtained from the same sample set using a Faraday Cup detector setup. In general, the curves for secondary electron yield versus primary energy for both measurement setups were comparable. On average a 15-20% lower signal was recorded on our setup compared to the Faraday Cup, which was attributed to the lower photoluminescent efficiency of the P22 phosphor screens when operated at sub-kilovolt bias voltages.

  10. Two-dimensional simulation research of secondary electron emission avalanche discharge on vacuum insulator surface

    Science.gov (United States)

    Cai, Libing; Wang, Jianguo; Zhu, Xiangqin; Wang, Yue; Zhang, Dianhui

    2015-01-01

    Based on the secondary electron emission avalanche (SEEA) model, the SEEA discharge on the vacuum insulator surface is simulated by using a 2D PIC-MCC code developed by ourselves. The evolutions of the number of discharge electrons, insulator surface charge, current, and 2D particle distribution are obtained. The effects of the strength of the applied electric field, secondary electron yield coefficient, rise time of the pulse, length of the insulator on the discharge are investigated. The results show that the number of the SEEA electrons presents a quadratic dependence upon the applied field strength. The SEEA current, which is on the order of Ampere, is directly proportional to the field strength and secondary electron yield coefficient. Finally, the electron-stimulated outgassing is included in the simulation code, and a three-phase discharge curve is presented by the simulation, which agrees with the experimental data.

  11. Two-dimensional simulation research of secondary electron emission avalanche discharge on vacuum insulator surface

    International Nuclear Information System (INIS)

    Cai, Libing; Wang, Jianguo; Zhu, Xiangqin; Wang, Yue; Zhang, Dianhui

    2015-01-01

    Based on the secondary electron emission avalanche (SEEA) model, the SEEA discharge on the vacuum insulator surface is simulated by using a 2D PIC-MCC code developed by ourselves. The evolutions of the number of discharge electrons, insulator surface charge, current, and 2D particle distribution are obtained. The effects of the strength of the applied electric field, secondary electron yield coefficient, rise time of the pulse, length of the insulator on the discharge are investigated. The results show that the number of the SEEA electrons presents a quadratic dependence upon the applied field strength. The SEEA current, which is on the order of Ampere, is directly proportional to the field strength and secondary electron yield coefficient. Finally, the electron-stimulated outgassing is included in the simulation code, and a three-phase discharge curve is presented by the simulation, which agrees with the experimental data

  12. Bistable intrinsic charge fluctuations of a dust grain subject to secondary electron emission in a plasma.

    Science.gov (United States)

    Shotorban, B

    2015-10-01

    A master equation was formulated to study intrinsic charge fluctuations of a grain in a plasma as ions and primary electrons are attached to the grain through collisional collection, and secondary electrons are emitted from the grain. Two different plasmas with Maxwellian and non-Maxwellian distributions were considered. The fluctuations could be bistable in either plasma when the secondary electron emission is present, as two stable macrostates, associated with two stable roots of the charge net current, may exist. Metastablity of fluctuations, manifested by the passage of the grain charge between two macrostates, was shown to be possible.

  13. Observation of reduction of secondary electron emission from helium ion impact due to plasma-generated nanostructured tungsten fuzz

    International Nuclear Information System (INIS)

    Hollmann, E M; Doerner, R P; Nishijima, D; Pigarov, A Yu

    2017-01-01

    Growth of nanostructured fuzz on a tungsten target in a helium plasma is found to cause a significant (∼3×) reduction in ion impact secondary electron emission in a linear plasma device. The ion impact secondary electron emission is separated from the electron impact secondary electron emission by varying the target bias voltage and fitting to expected contributions from electron impact, both thermal and non-thermal; with the non-thermal electron contribution being modeled using Monte-Carlo simulations. The observed (∼3×) reduction is similar in magnitude to the (∼2×) reduction observed in previous work for the effect of tungsten fuzz formation on secondary electron emission due to electron impact. It is hypothesized that the observed reduction results from re-absorption of secondary electrons in the tungsten fuzz. (paper)

  14. Secondary electron emission of sapphire tungsten molybdenum and titanium for Maxwellian incident electrons

    International Nuclear Information System (INIS)

    Saussez-Hublet, M.-C.; Harbour, P.J.

    1980-06-01

    The second electron emission coefficient of various materials, namely titanium, molybdenum, tungsten and sapphire, has been calculated for a Maxwellian energy distribution from data for a normally incident monoenergetic beam of primary electrons. The most significant difference from the monoenergetic case occurs at low energies. In addition the influence of the incident angle of the electrons is discussed. (author)

  15. Secondary electron emission from solid HD and a solid H2-D2 mixture

    DEFF Research Database (Denmark)

    Sørensen, H.; Børgesen, P.; Hao-Ming, Chen

    1983-01-01

    Secondary electron emission from solid HD and a solid 0.6 H2 + 0.4 D2 mixture has been studied for electron and hydrogen ion bombardment at primary energies from 0.5 to 3 keV and 2 to 10 keV/amu, respectively. The yield for solid HD is well explained by a simple stoichiometric model of the low...

  16. Secondary Electron Emission from Solid Hydrogen and Deuterium Resulting from Incidence of keV Electrons and Hydrogen Ions

    DEFF Research Database (Denmark)

    Sørensen, H.

    1977-01-01

    are small, in contrast to what is expected for insulating materials. One explanation is that the secondary electrons lose energy inside the target material by exciting vibrational and rotational states of the molecules, so that the number of electrons that may escape as secondary electrons is rather small....... The losses to molecular states will be largest for hydrogen, so that the SEE coefficients are smallest for solid hydrogen, as was observed. For the incidence of ions, the values of δ for the different molecular ions agree when the number of secondary electrons per incident atom is plotted versus the velocity...... or the stopping power of the incident particles. Measurements were also made for oblique incidence of H+ ions on solid deuterium for angles of incidence up to 75°. A correction could be made for the emission of secondary ions by also measuring the current calorimetrically. At largest energies, the angular...

  17. Secondary electron emission and self-consistent charge transport in semi-insulating samples

    Energy Technology Data Exchange (ETDEWEB)

    Fitting, H.-J. [Institute of Physics, University of Rostock, Universitaetsplatz 3, D-18051 Rostock (Germany); Touzin, M. [Unite Materiaux et Transformations, UMR CNRS 8207, Universite de Lille 1, F-59655 Villeneuve d' Ascq (France)

    2011-08-15

    Electron beam induced self-consistent charge transport and secondary electron emission (SEE) in insulators are described by means of an electron-hole flight-drift model (FDM) now extended by a certain intrinsic conductivity (c) and are implemented by an iterative computer simulation. Ballistic secondary electrons (SE) and holes, their attenuation to drifting charge carriers, and their recombination, trapping, and field- and temperature-dependent detrapping are included. As a main result the time dependent ''true'' secondary electron emission rate {delta}(t) released from the target material and based on ballistic electrons and the spatial distributions of currents j(x,t), charges {rho}(x,t), field F(x,t), and potential V(x,t) are obtained where V{sub 0} = V(0,t) presents the surface potential. The intrinsic electronic conductivity limits the charging process and leads to a conduction sample current to the support. In that case the steady-state total SE yield will be fixed below the unit: i.e., {sigma} {eta} + {delta} < 1.

  18. Disparity of secondary electron emission in ferroelectric domains of YMnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Shaobo; Deng, S. Q.; Yuan, Wenjuan; Yan, Yunjie; Zhu, Jing, E-mail: jzhu@tsinghua.edu.cn [National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, The State Key Laboratory of Ceramics and Fine Processing, Key Laboratory of Advanced Materials (MOE), Tsinghua University, Beijing 100084 (China); Li, J.; Li, J. Q. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-07-20

    The applications of multiferroic materials require our understanding about the behaviors of domains with different polarization directions. Taking advantage of the scanning electron microscope, we investigate the polar surface of single crystal YMnO{sub 3} sample in secondary electron (SE) mode. By slowing down the scanning speed of electron beam, the negative surface potential of YMnO{sub 3} can be realized, and the domain contrast can be correspondingly changed. Under this experimental condition, with the help of a homemade Faraday cup, the difference of intrinsic SE emission coefficients of antiparallel domains is measured to be 0.12 and the downward polarization domains show a larger SE emission ability. Our results indicate that the total SE emission of this material can be altered by changing the ratio of the antiparallel domains, which provide an avenue for device design with this kind of materials.

  19. Monte-Carlo simulations of secondary electron emission from CsI, induced by 1-10 keV X-rays and electrons

    International Nuclear Information System (INIS)

    Akkerman, A.; Gibrekhterman, A.; Breskin, A.; Chechik, R.

    1992-05-01

    A model for electron transport and emission in CsI is proposed. It is based on theoretically calculated microscopic cross-sections for electron interaction with the nuclear and the electronic components of the solid. A Monte Carlo program based on this model was developed to simulate secondary electron emission induced by X-rays and electrons in the energy range of 1 to 10 keV. The calculated secondary emission yields agree with existing experimental data. The model provides all necessary characteristics for the design of radiation detectors based on secondary electron emission. It can be expanded to higher incident energies and other alkali halides. (author)

  20. Secondary emission ion analyzer provided with an electron gun for insulating material analysis

    International Nuclear Information System (INIS)

    Blanchard, Bruno; Carrier, Patrick; Marguerite, J.-L.; Rocco, J.-C.

    1976-01-01

    This invention relates to a secondary emission ion analyser, fitted with an electron gun. It is used in the mass spectrometry analysis of electrically insulating bodies. It has already been suggested to bombard the target with an electron beam in conjunction with the beam of primary particles, in order to reduce the space charge near the target. The object of this invention is the application of this known process to appliances of the ion analyser type with a high electric field near the target. Its main characteristic is the use of an electron gun emitting an electron beam through the extraction lens placed opposite the target. The extraction electric field influences the path of the electrons but the electric and mechanical specifications of the electron gun in the invention are such that the target is correctly sprayed by the electron beam [fr

  1. Improved age-diffusion model for low-energy electron transport in solids. II. Application to secondary emission from aluminum

    International Nuclear Information System (INIS)

    Dubus, A.; Devooght, J.; Dehaes, J.C.

    1987-01-01

    The ''improved age-diffusion'' model for secondary-electron transport is applied to aluminum. Electron cross sections for inelastic collisions with the free-electron gas using the Lindhard dielectric function and for elastic collisions with the randomly distributed ionic cores are used in the calculations. The most important characteristics of backward secondary-electron emission induced by low-energy electrons on polycrystalline Al targets are calculated and compared to experimental results and to Monte Carlo calculations. The model appears to predict the electronic yield, the energy spectra, and the spatial dependence of secondary emission with reasonable accuracy

  2. Construction of electron accelerator for studying secondary emission in dielectric materials

    International Nuclear Information System (INIS)

    Hessel, R.

    1990-01-01

    An acelerator for the generation of low energy electrons (in the 0.4 to 20 keV range) was constructed. The accelerator is equipped with some devices especially designed for the investigation of the electrical properties of electron-irradiated dielectrics. In this work we have employed it for the study of the secondary electron emission of irradiated polymers. Reference is made to a method proposed by H. von Seggern (IEEE Trans. Nucl. Sci. NS-32, p.1503 (1985)] which was intended for the determination of the electron emission yield especially between the two cross-over points in a single run, here called the dynamical method. We have been able to prove that, contrary to expectation, this method does not give correct results over the entire emission curve. Rather it gives yield values which are too low by 25% in the region where the emission exhibits a maximum, due to the interaction between the electron emission process and the positive surface charge of the dielectric. However the method needs not to be dismissed entirely. As it is, it can be used advantageously for the precise determination of the energy of the second cross-over point. In addition, with the same set up, the method could be improved by replacing the continuous irradiation of the sample by a pulsed irradiation, leading to results essentially the same as those shown in the literature. Finally analysing the process of interaction between the positive charge of the dielectric and the mechanism of electron emission in several situations, we were able: I) to determine the maximum value and the average value of the escape depth of the emitted electrons; II) for a sample with a net positive charge, to show that the positive charge resides very near the surface of incidence; III) for a sample with a net negative charge, to show that the positive charge also resides near the surface while the (prevalent) negative charge resides in the bulk of the material. (author)

  3. Experimental Investigation of Charging Properties of Interstellar Type Silica Dust Grains by Secondary Electron Emissions

    Science.gov (United States)

    Tankosic, D.; Abbas, M. M.

    2013-01-01

    The dust charging by electron impact is an important dust charging processes in astrophysical and planetary environments. Incident low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grains, leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available classical theoretical models for calculations of SEE yields are generally applicable for neutral, planar, or bulk surfaces. These models, however, are not valid for calculations of the electron impact charging properties of electrostatically charged micron/submicron-size dust grains in astrophysical environments. Rigorous quantum mechanical models are not yet available, and the SEE yields have to be determined experimentally for development of more accurate models for charging of individual dust grains. At the present time, very limited experimental data are available for charging of individual micron-size dust grains, particularly for low energy electron impact. The experimental results on individual, positively charged, micron-size lunar dust grains levitated carried out by us in a unique facility at NASA-MSFC, based on an electrodynamic balance, indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (Abbas et al, 2010, 2012). In this paper, we discuss SEE charging properties of individual micron-size silica microspheres that are believed to be analogs of a class of interstellar dust grains. The measurements indicate charging of the 0.2m silica particles when exposed to 25 eV electron beams and discharging when exposed to higher energy electron beams. Relatively large size silica particles (5.2-6.82m) generally discharge to lower equilibrium potentials at both electron energies

  4. Charging of Individual Micron-Size Interstellar/Planetary Dust Grains by Secondary Electron Emissions

    Science.gov (United States)

    Tankosic, D.; Abbas, M. M.

    2012-01-01

    Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper, we discuss experimental results on dust charging by electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Currently, very limited experimental data are available for charging of individual micron-size dust grains, particularly by low energy electron impact. Available theoretical models based on the Sternglass equation (Sternglass, 1954) are applicable for neutral, planar, and bulk surfaces only. However, charging properties of individual micron-size dust grains are expected to be different from the values measured on bulk materials. Our recent experimental results on individual, positively charged, micron-size lunar dust grains levitated in an electrodynamic balance facility (at NASA-MSFC) indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Here we discuss the complex nature of SEE charging properties of individual micron-size lunar dust grains and silica microspheres.

  5. On Secondary Electron Emission from Solid H2 and D2

    DEFF Research Database (Denmark)

    Schou, Jørgen; Sørensen, H.

    1978-01-01

    The emission of secondary electrons from solid hydrogen (H2 , D2, T2) is often considered to be of importance for the interaction between a fusion plasma and pellets of solid hydrogens. A set-up was therefore built for studies of interactions between energetic particles and solid hydrogens. Studies...... of secondary electron emission (SEE) from solid H2 and D2 were made for incidence of electrons up to 3 keV and for incidence of ions of hydrogen, deuterium, and helium up to 10 keV. The measurements were made for normal incidence, and in some cases also for oblique incidence. The SEE coefficients for solid H2...... is always 0.65-0.70 times that for solid D2. This difference is attributed to different losses to vibrational states in H2 and D2 for the low energy electrons. Measurements were also made on solid para-H2 with both electrons and hydrogen ions. There was no difference from the results for normal H2, which...

  6. Study of a high power hydrogen beam diagnostic based on secondary electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Sartori, E., E-mail: emanuele.sartori@igi.cnr.it [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy); Department of Management and Engineering, University di Padova strad. S. Nicola 3, 36100 Vicenza (Italy); Panasenkov, A. [NRC, Kurchatov Institute, 1, Kurchatov Sq, Moscow 123182 (Russian Federation); Veltri, P. [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy); INFN-LNL, viale dell’Università n. 2, 35020 Legnaro (Italy); Serianni, G.; Pasqualotto, R. [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy)

    2016-11-15

    In high power neutral beams for fusion, beam uniformity is an important figure of merit. Knowing the transverse power profile is essential during the initial phases of beam source operation, such as those expected for the ITER heating neutral beam (HNB) test facility. To measure it a diagnostic technique is proposed, based on the collection of secondary electrons generated by beam-surface and beam-gas interactions, by an array of positively biased collectors placed behind the calorimeter tubes. This measurement showed in the IREK test stand good proportionality to the primary beam current. To investigate the diagnostic performances in different conditions, we developed a numerical model of secondary electron emission, induced by beam particle impact on the copper tubes, and reproducing the cascade of secondary emission caused by successive electron impacts. The model is first validated against IREK measurements. It is then applied to the HNB case, to assess the locality of the measurement, the proportionality to the beam current density, and the influence of beam plasma.

  7. Low-energy positron and electron diffraction and positron-stimulated secondary electron emission from Cu(100)

    International Nuclear Information System (INIS)

    Weiss, A.H.

    1983-01-01

    The results of two series of experiments are reported. In the first, an electrostatically guided beam of low-energy (40-400 eV) positrons, delta/sub p/ was used to study low-energy positron diffraction (LEPD) from a Cu(100) surface under ultrahigh-vacuum conditions. Low-energy electron diffraction (LEED) data were obtained from the same sample in the same apparatus. Comparison of LEPD and LEED intensity versus energy data with model calculations made using computer programs developed by C.B. Duke and collaborators indicated that: LEPD data is adequately modeled using potentials with no exchange-correlation term. The inelastic mean free path, lambda/sub ee/, is shorter for positrons than for electrons at low (< approx.80 eV). LEED is better than LEPD at making a determination of the first-layer spacing of Cu(100) for the particular data set reported. In the second set of experiments, the same apparatus and sample were used to compare positron- and electron-stimulated secondary-electron emission (PSSEE and ESSEE). The results were found to be consistent with existing models of secondary-electron production for metals. The energy distributions of secondary-electrons had broad low-energy (<10 eV) peaks for both positron and electron stimulation. But the PSEE distribution showed no elastic peak. Measurements of secondary-electron angular distributions, found to be cosine-like in both the PSSEE and ESSEE case, were used to obtain total secondary yield ratios, delta, at four beam energies ranging from 40-400 eV. The secondary yield ratio for primary positrons and the yield for primary electrons, delta/sub e/, were similar at these energies. For 400-eV primary particles the secondary yields were found to be delta/sub p/ = 0.94 +/- 0.12 and delta/sub e/ = 0.94 +/- 0./12, giving a ratio of unity for positron-stimulated secondary yield to electron-stimulated secondary yield

  8. Comparison endpoint study of process plasma and secondary electron beam exciter optical emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stephan Thamban, P. L.; Yun, Stuart; Padron-Wells, Gabriel; Hosch, Jimmy W.; Goeckner, Matthew J. [Department of Mechanical Engineering, University of Texas at Dallas, 800W Campbell Road, Richardson, Texas 75080 (United States); Department of Electrical Engineering, University of Texas at Dallas, 800W Campbell Road, Richardson, Texas 75080 (United States); Verity Instruments, Inc., 2901 Eisenhower Street, Carrollton, Texas 75007 (United States); Department of Mathematical Sciences, University of Texas at Dallas, 800 W Campbell Road, Richardson, Texas 75080 (United States)

    2012-11-15

    Traditionally process plasmas are often studied and monitored by optical emission spectroscopy. Here, the authors compare experimental measurements from a secondary electron beam excitation and direct process plasma excitation to discuss and illustrate its distinctiveness in the study of process plasmas. They present results that show excitations of etch process effluents in a SF{sub 6} discharge and endpoint detection capabilities in dark plasma process conditions. In SF{sub 6} discharges, a band around 300 nm, not visible in process emission, is observed and it can serve as a good indicator of etch product emission during polysilicon etches. Based on prior work reported in literature the authors believe this band is due to SiF{sub 4} gas phase species.

  9. Secondary electron emission from Au by medium energy atomic and molecular ions

    CERN Document Server

    Itoh, A; Obata, F; Hamamoto, Y; Yogo, A

    2002-01-01

    Number distributions of secondary electrons emitted from a Au metal surface have been measured for atomic and molecular ions of H sup + , He sup + , C sup + , N sup + , O sup + , H sup + sub 2 , H sup + sub 3 , HeH sup + , CO sup + and O sup + sub 2 in the energy range 0.3-2.0 MeV. The emission statistics obtained are described fairly well by a Polya function. The Polya parameter b, determining the distribution shape, is found to decrease monotonously with increasing emission yield gamma, revealing a surprising relationship of b gamma approx 1 over the different projectile species and impact energies. This finding supports certainly the electron cascading model. Also we find a strong negative molecular effect for heavier molecular ions, showing a significant reduction of gamma compared to the estimated values using constituent atomic projectile data.

  10. Effect of secondary electron emission on subnanosecond breakdown in high-voltage pulse discharge

    Science.gov (United States)

    Schweigert, I. V.; Alexandrov, A. L.; Gugin, P.; Lavrukhin, M.; Bokhan, P. A.; Zakrevsky, Dm E.

    2017-11-01

    The subnanosecond breakdown in open discharge may be applied for producing superfast high power switches. Such fast breakdown in high-voltage pulse discharge in helium was explored both in experiment and in kinetic simulations. The kinetic model of electron avalanche development was developed using PIC-MCC technique. The model simulates motion of electrons, ions and fast helium atoms, appearing due to ions scattering. It was shown that the mechanism responsible for ultra-fast breakdown development is the electron emission from cathode. The photoemission and emission by ions or fast atoms impact is the main reason of current growth at the early stage of breakdown, but at the final stage, when the voltage on discharge gap drops, the secondary electron emission (SEE) is responsible for subnanosecond time scale of current growth. It was also found that the characteristic time of the current growth τS depends on the SEE yield of the cathode material. Three types of cathode material (titanium, SiC, and CuAlMg-alloy) were tested. It is shown that in discharge with SiC and CuAlMg-alloy cathodes (which have enhanced SEE) the current can increase with a subnanosecond characteristic time as small as τS = 0.4 ns, for the pulse voltage amplitude of 5- 12 kV..

  11. Subnanosecond breakdown development in high-voltage pulse discharge: Effect of secondary electron emission

    Science.gov (United States)

    Alexandrov, A. L.; Schweigert, I. V.; Zakrevskiy, Dm. E.; Bokhan, P. A.; Gugin, P.; Lavrukhin, M.

    2017-10-01

    A subnanosecond breakdown in high-voltage pulse discharge may be a key tool for superfast commutation of high power devices. The breakdown in high-voltage open discharge at mid-high pressure in helium was studied in experiment and in kinetic simulations. The kinetic model of electron avalanche development was constructed, based on PIC-MCC simulations, including dynamics of electrons, ions and fast helium atoms, produced by ions scattering. Special attention was paid to electron emission processes from cathode, such as: photoemission by Doppler-shifted resonant photons, produced in excitation processes involving fast atoms; electron emission by ions and fast atoms bombardment of cathode; the secondary electron emission (SEE) by hot electrons from bulk plasma. The simulations show that the fast atoms accumulation is the main reason of emission growth at the early stage of breakdown, but at the final stage, when the voltage on plasma gap diminishes, namely the SEE is responsible for subnanosecond rate of current growth. It was shown that the characteristic time of the current growth can be controlled by the SEE yield. The influence of SEE yield for three types of cathode material (titanium, SiC, and CuAlMg-alloy) was tested. By changing the pulse voltage amplitude and gas pressure, the area of existence of subnanosecond breakdown is identified. It is shown that in discharge with SiC and CuAlMg-alloy cathodes (which have enhanced SEE) the current can increase with a subnanosecond characteristic time value as small as τs = 0.4 ns, for the pulse voltage amplitude of 5÷12 kV. An increase of gas pressure from 15 Torr to 30 Torr essentially decreases the time of of current front growth, whereas the pulse voltage variation weakly affects the results.

  12. Effect of secondary electron emission on Jean's instability in a complex plasma in the presence of nonthermal ions

    International Nuclear Information System (INIS)

    Sarkar, Susmita; Maity, Saumyen; Banerjee, Soumyajyoti

    2011-01-01

    In this paper, we have investigated the role of secondary electron emission on Jean's instability in a complex plasma in the presence of nonthermal ions. The equilibrium dust surface potential has been considered negative and hence primary and secondary electron temperatures are equal. Such plasma consists of three components: Boltzman distributed electrons, nonthermal ions and negatively charged inertial dust grains. From the linear dispersion relation, we have calculated the real frequency and growth rate of Jean's instability. Numerically, we have shown that for strong ion nonthermality Jean's mode is unstable. Growth of the instability reduces and the real part of the wave frequency increases with increasing secondary electron emission from dust grains. Hence, strong secondary electron emission suppresses Jean's instability in a complex plasma even when ion nonthermality is strong and equilibrium dust charge is negative.

  13. Multi-channel electronics for secondary emission grid profile monitor of TTF linac

    International Nuclear Information System (INIS)

    Reingardt-Nikoulin, P.; Gaidash, V.; Mirzojan, A.; Kocharyan, V.; Noelle, D.

    2004-01-01

    According to the TTF beam experimental program, a measurement f the time dependence of the energy spread within the bunch train should be done by means of a standard device for profile measurements, that is Secondary Emission Grid (SEMG). SEMG on the high-energy TTF beam is placed in the focal plane of the magnet spectrometer. It should measure the total energy spread in the range from 0.1% up to a few percents for any single or any group of electron bunches in the bunch train of TTF Linac. SEMG profile measurements with new high sensitive electronics are described. Beam results of SEMG Monitor test are given for two modifications of an electronic preamplifier

  14. Characteristics of a wire ion plasma source and a secondary emission electron gun

    International Nuclear Information System (INIS)

    Hotta, Eiki; Osawa, Teruya; Urai, Hajime; Suzuki, Mitsuaki; Yasui, Hiroyuki; Tamagawa, Tohru

    1993-01-01

    Electrical characteristics of a wire ion plasma source (WIPS) and a secondary emission electron gun, for which the WIPS is used as an ion source, will be reported. The WIPS is a cold-cathode gaseous discharge device, in which a radial electron trapping permits an extremely low pressure gaseous discharge with very low applied voltages. The time evolutions of temperature and density of afterglow plasma were measured with a double probe. In the case of P 0 = 25 mTorr He and the maximum discharge current of 200 A, the temperature and density of electron were about 20 eV and of the order of 10 18 m -3 , respectively, just after the distinction of discharge. The ion current density measured by a biased ion collector (BIC) on the discharge tube wall was found to reach up to 300 mA/cm 2 . A secondary emission electron gun was set on the discharge tube wall opposite to the BIC. An earthed mesh net is installed at a height of 8 mm just in front of the cathode. The maximum negative bias voltage applied to the cathode is limited to -50 kV by the local breakdown in the gun, which occurred synchronously with the WIPS discharge. The electron beam current was measured by the BIC, in which an aluminum foil with a width of 2 μm was placed on instead of the earthed mesh net. At the cathode voltage of -30 kV, the measured beam current density was 220 mA/cm 2 . The extraporation of the resulted curve indicates that if the cathode voltage is -100 kV, the current density will reach to 1 A/cm 2 . The energy spectrum of the electron beam was measured with a magnetic energy analyzer, which was set in place of the BIC. The energy spread is about 300 eV at the central energy of 40 keV. Thus, they demonstrated the possibility of a high current density secondary emission electron gun, for which a WIPS is used as an ion source

  15. Measurements and Studies of Secondary Electron Emission of Diamond Amplified Photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Wu,Q.

    2008-10-01

    The Diamond Amplified Photocathode (DAP) is a novel approach to generating electrons. By following the primary electron beam, which is generated by traditional electron sources, with an amplifier, the electron beam available to the eventual application is increased by 1 to 2 orders of magnitude in current. Diamond has a very wide band gap of 5.47eV which allows for a good negative electron affinity with simple hydrogenation, diamond can hold more than 2000MV/m field before breakdown. Diamond also provides the best rigidity among all materials. These two characters offer the capability of applying high voltage across very thin diamond film to achieve high SEY and desired emission phase. The diamond amplifier also is capable of handling a large heat load by conduction and sub-nanosecond pulse input. The preparation of the diamond amplifier includes thinning and polishing, cleaning with acid etching, metallization, and hydrogenation. The best mechanical polishing available can provide high purity single crystal diamond films with no less than 100 {micro}m thickness and <15 nm Ra surface roughness. The ideal thickness for 700MHz beam is {approx}30 {micro}m, which requires further thinning with RIE or laser ablation. RIE can achieve atomic layer removal precision and roughness eventually, but the time consumption for this procedure is very significant. Laser ablation proved that with <266nm ps laser beam, the ablation process on the diamond can easily achieve removing a few microns per hour from the surface and <100nm roughness. For amplifier application, laser ablation is an adequate and efficient process to make ultra thin diamond wafers following mechanical polishing. Hydrogenation will terminate the diamond surface with monolayer of hydrogen, and form NEA so that secondary electrons in the conduction band can escape into the vacuum. The method is using hydrogen cracker to strike hydrogen atoms onto the bare diamond surface to form H-C bonds. Two independent

  16. Very High Radiation Detector for the LHC BLM System Based on Secondary Electron Emission

    CERN Document Server

    Dehning, B; Holzer, EB; Kramer, D

    2007-01-01

    Beam Loss Monitoring (BLM) system plays a vital role in the active protection of the LHC accelerators elements. It should provide the number of particles lost from the primary hadron beam by measuring the radiation field induced by their interaction with matter surrounding the beam pipe. The LHC BLM system will use ionization chambers as standard detectors but in the areas where very high dose rates are expected, the Secondary Emission Monitor (SEM) chambers will be employed because of their high linearity, low sensitivity and fast response. The SEM needs a high vacuum for proper operation and has to be functional for up to 20 years, therefore all the components were designed according to the UHV requirements and a getter pump was included. The SEM electrodes are made of Ti because of its Secondary Emission Yield (SEY) stability. The sensitivity of the SEM was modeled in Geant4 via the Photo-Absorption Ionization module together with custom parameterization of the very low energy secondary electron production...

  17. Enhanced flashover strength in polyethylene nanodielectrics by secondary electron emission modification

    Directory of Open Access Journals (Sweden)

    Weiwang Wang

    2016-04-01

    Full Text Available This work studies the correlation between secondary electron emission (SEE characteristics and impulse surface flashover in polyethylene nanodielectrics both theoretically and experimentally, and illustrates the enhancement of flashover voltage in low-density polyethylene (LDPE through incorporating Al2O3 nanoparticles. SEE characteristics play key roles in surface charging and gas desorption during surface flashover. This work demonstrates that the presence of Al2O3 nanoparticles decreases the SEE coefficient of LDPE and enhances the impact energy at the equilibrium state of surface charging. These changes can be explained by the increase of surface roughness and of surface ionization energy, and the strong interaction between nanoparticles and the polymer dielectric matrix. The surface charge and flashover voltage are calculated according to the secondary electron emission avalanche (SEEA model, which reveals that the positive surface charges are reduced near the cathode triple point, while the presence of more nanoparticles in high loading samples enhances the gas desorption. Consequently, the surface flashover performance of LDPE/Al2O3 nanodielectrics is improved.

  18. The influence of secondary electron emission on the floating potential of tokamak-born dust

    International Nuclear Information System (INIS)

    Vaverka, J; Richterová, I; Vyšinka, M; Pavlů, J; Šafránková, J; Němeček, Z

    2014-01-01

    Dust production and its transport into the core plasma is an important issue for magnetic confinement fusion. Dust grains are charged by various processes, such as the collection of plasma particles and electron emissions, and their charge influences the dynamics of the dust. This paper presents the results of calculations of the surface potential of dust grains in a Maxwellian plasma. Our calculations include the charging balance of a secondary electron emission (SEE) from the dust. The numerical model that we have used accounts for the influence of backscattered electrons and takes into account the effects of grain size, material, and it is also able to handle both spherical and non-spherical grains. We discuss the role of the SEE under tokamak conditions and show that the SEE is a leading process for the grains crossing the scrape-off layer from the edge to core plasma. The results of our calculations are relevant for materials related to fusion experiments in ITER. (paper)

  19. Low-energy electron transmission and secondary-electron emission experiments on crystalline and molten long-chain alkanes

    International Nuclear Information System (INIS)

    Ueno, N.; Sugita, K.; Seki, K.; Inokuchi, H.

    1986-01-01

    This paper describes the results of low-energy electron transmission and secondary-electron emission experiments on thin films of long-chain alkanes deposited on metal substrates. The spectral changes due to crystal-melt phase transition were measured in situ in both experiments. The ground-state energy V 0 of the quasifree electron in crystalline state was determined to be 0.5 +- 0.1 eV. The value of V 0 for the molten state was found to be negative. Further, in the crystalline state evidence is found for a direct correspondence between the transmission maxima and the high value of the density of states in the conduction bands

  20. Electronic emission and electron guns

    International Nuclear Information System (INIS)

    Roy, Amitava

    2010-01-01

    This paper reviews the process of electron emission from metal surface. Although electrons move freely in conductors like metals, they normally do not leave the metal without some manipulation. In fact, heating and bombardment are the two primary ways in which electrons are emitted through the use of a heating element behind the cathode (termed thermionic emission) or as a result of bombardment with a beam of electrons, ions, or metastable atoms (termed secondary emission). Another important emission mechanism called Explosive Electron Emission (EEE) is also often used in various High Voltage Pulse Power Systems to generate very high current (few hundreds of kA) pulsed electron beams. The electron gun is the device in that it shoots off a continuous (or pulsed) stream of electrons. A brief idea about the evolution of the electron gun components and their basis of functioning are also discussed. (author)

  1. Electronic excitation effects on secondary ion emission in highly charged ion-solid interaction

    International Nuclear Information System (INIS)

    Sekioka, T.; Terasawa, M.; Mitamura, T.; Stoeckli, M.P.; Lehnert, U.; Fehrenbach, C.

    2001-01-01

    In order to investigate the secondary ion emission from the surface of conductive materials bombarded by highly charged heavy ions, we have done two types of experiments. First, we have measured the yield of the sputtered ions from the surface of solid targets of conductive materials (Al, Si, Ni, Cu) bombarded by Xe q+ (q=15-44) at 300 keV (v p =0.30 a.u) and at 1.0 MeV (v p =0.54 a.u). In view of the secondary ion yields as a function of the potential energy of the projectile, the increase rates below q=35, where the potential energy amounts to 25.5 keV, were rather moderate and showed a prominent increase above q=35. These phenomena were rather strong in the case of the metal targets. Second, we have measured the energy dependence of the yield of the sputtered ions from the surface of solid targets of conductive materials (C, Al) bombarded by Xe q+ (q=30,36,44) between 76 keV (v p =0.15 a.u) and 6.0 MeV (v p =1.3 a.u). A broad enhancement of the secondary ion yield has been found for Al target bombarded by Xe 44+ . From these experimental results, the electronic excitation effects in conductive materials for impact of slow highly charged heavy ions bearing high potential energy is discussed

  2. The role of secondary electrons in some experiments determining fluorescence emission from nitrogen C3Πu levels

    International Nuclear Information System (INIS)

    Blanco, F.; Arqueros, F.

    2005-01-01

    The processes involved in fluorescence emission from C 3 Π u levels of N 2 molecule by electron impact are studied. Secondary electrons are shown to play an important role in typical experiments for the measurement of emission cross sections and fluorescence yields, dominating at high impact energies. A simple model is proposed which accounts for fluorescence measurements in a wide range of experimental conditions, and in particular for some recent results up to 1 GeV energies

  3. Beam profile measurement of ES-200 using secondary electron emission monitor

    Directory of Open Access Journals (Sweden)

    E Ebrahimi Basabi

    2015-09-01

    Full Text Available Up to now, different designs have been introduced for measurement beam profile accelerators. Secondary electron emission monitors (SEM are one of these devices which have been used for this purpose. In this work, a SEM has been constructed to measure beam profile of ES-200 accelerator, a proton electrostatic accelerator which is installed at SBU. Profile grid for both planes designed with 16 wires which are insulated relative to each other. The particles with maximum energy of 200 keV and maximum current of 400 μA are stopped in copper wires. Each of the wires has an individual current-to-voltage amplifier. With a multiplexer, the analogue values are transported to an ADC. The ADCs are read out by a microcontroller and finally profile of beam shows by a user interface program

  4. Charging of Single Micron Sized Dust Grains by Secondary Electron Emission: A Laboratory Study

    Science.gov (United States)

    Spann, James F., Jr.; Venturini, Catherine C.; Comfort, R. H.

    1998-01-01

    We present the details of a new laboratory study whose objective is to experimentally study the interaction of micron sized particles with plasmas and electromagnetic radiation. Specifically, to investigate under what conditions and to what extent do particles of various compositions and sizes become charged, or discharged, while exposed to an electron beam and ultraviolet radiation environment The emphasis is the study of the two charging mechanisms, secondary emission of electrons and photoelectric effect. The experiment uses a technique known as electrodynamic suspension of particles. With this technique, a single charged particle is electrodynamically levitated and then exposed to a controlled environment. Its charge to mass ratio is directly measured. Viscous drag measurements and the light scattering measurements characterize its size and optical characteristics. The environment to which the particle is expose may consist of room temperature and pressure or a rarefied atmosphere where only one major gaseous constituent is present, or, as in this case, a vacuum environment under electron bombardment or UV radiation . In addition, the environment can be cycled as part of the experiment. Therefore, using this technique, a single particle can be repeatedly exposed to a controlled environment and its response measured, or a single particle can be exposed to similar environments with minor differences and its response measured as a function of only the changed environmental conditions.

  5. Secondary electron emission from metals irradiated by 0.4-3 MeV gamma-quanta

    International Nuclear Information System (INIS)

    Grudskij, M.Ya.; Malyshenkov, A.V.; Smirnov, V.V.

    1975-01-01

    Experimental and calculational data were considered on the secondary electron emission outgoing from metal targets of an equilibrium thickness irradiated by gamma-quanta fluxes with the energies from 0.4 to 3 MeV. New experimental data are presented. Characteristics of emission were measured by two methods: by magnetic spectrometers with a transverse magnetic field, and by means of an electrometric device with using radioisotopic gamma-sources of 198 Au, 137 Cs, 60 Co and 24 Na. The dependence of the electron emission on the atomic number of the target material was studied. For this purpose the parameters of emissions outgoing from Al-, Cu-, Cd-, Pb- and Au-targets were measured. The advantages and shortcomings of the known methods of calculating the second electron emission were discussed. The obtained experimental and calculational results on studying electrons were compared with those known from literature, and possible sources of systematic errors were discussed

  6. Investigation of argon ion sputtering on the secondary electron emission from gold samples

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jing; Cui, Wanzhao, E-mail: cuiwanzhao@126.com; Li, Yun; Xie, Guibai; Zhang, Na; Wang, Rui; Hu, Tiancun; Zhang, Hongtai

    2016-09-30

    Highlights: • An “equivalent work function” is presented in this thesis to establish the relationship between SE yield and surface properties. • After sputtering, A decrease of δmax and an increase of E1 were observed with increasing Eion. • Further sputtering at higher energies broaden the SE spectra, and the equivalent work function, ϕ, increase considerably to 12.6 eV. - Abstract: Secondary electron (SE) yield, δ, is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An “equivalent work function” is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called “work function” (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission.

  7. Investigation of argon ion sputtering on the secondary electron emission from gold samples

    International Nuclear Information System (INIS)

    Yang, Jing; Cui, Wanzhao; Li, Yun; Xie, Guibai; Zhang, Na; Wang, Rui; Hu, Tiancun; Zhang, Hongtai

    2016-01-01

    Highlights: • An “equivalent work function” is presented in this thesis to establish the relationship between SE yield and surface properties. • After sputtering, A decrease of δmax and an increase of E1 were observed with increasing Eion. • Further sputtering at higher energies broaden the SE spectra, and the equivalent work function, ϕ, increase considerably to 12.6 eV. - Abstract: Secondary electron (SE) yield, δ, is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An “equivalent work function” is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called “work function” (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission.

  8. Investigation of argon ion sputtering on the secondary electron emission from gold samples

    Science.gov (United States)

    Yang, Jing; Cui, Wanzhao; Li, Yun; Xie, Guibai; Zhang, Na; Wang, Rui; Hu, Tiancun; Zhang, Hongtai

    2016-09-01

    Secondary electron (SE) yield, δ, is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An ;equivalent work function; is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called ;work function; (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission.

  9. Analysis of secondary electron emission for conducting materials using 4-grid LEED/AES optics

    International Nuclear Information System (INIS)

    Patino, M I; Wirz, R E; Raitses, Y; Koel, B E

    2015-01-01

    A facility utilizing 4-grid optics for LEED/AES (low energy electron diffraction/Auger electron spectroscopy) was developed to measure the total secondary electron yield and secondary electron energy distribution function for conducting materials. The facility and experimental procedure were validated with measurements of 50–500 eV primary electrons impacting graphite. The total yield was calculated from measurements of the secondary electron current (i) from the sample and (ii) from the collection assembly, by biasing each surface. Secondary electron yield results from both methods agreed well with each other and were within the spread of previous results for the total yield from graphite. Additionally, measurements of the energy distribution function of secondary electrons from graphite are provided for a wider range of incident electron energies. These results can be used in modeling plasma-wall interactions in plasmas bounded by graphite walls, such as are found in plasma thrusters, and divertors and limiters of magnetic fusion devices. (paper)

  10. An experimental assessment of proposed universal yield curves for secondary electron emission

    International Nuclear Information System (INIS)

    Salehi, M.; Flinn, E.A.

    1980-01-01

    A variety of 'Universal Yield Curves' for the secondary emission process have been proposed. A series of precise measurements of the secondary emission properties of a range of related amorphous semiconducting materials, made under UHV on freshly vacuum-cleaved surfaces, and covering a wide range of primary energies, have recently made possible an accurate assessment of the validity of the various UYC's suggested. It is found that no truly universal curve exists; the atomic number of the target material plays an important part in determining the secondary emission properties. Agarwal's (Proc. Phys. Soc.; 71: 851 (1958)) semi-empirical expression, which takes account of the atomic number and weight, is found to give good agreement for all the materials studied. Further theoretical investigation is required. (author)

  11. Local secondary-electron emission spectra of graphite and gold surfaces obtained using the Scanning Probe Energy Loss Spectrometer (SPELS)

    International Nuclear Information System (INIS)

    Lawton, J J; Pulisciano, A; Palmer, R E

    2009-01-01

    Secondary-electron emission (SEE) spectra have been obtained with the Scanning Probe Energy Loss Spectrometer at a tip-sample distance of only 50 nm. Such short working distances are required for the best theoretical spatial resolution (<10 nm). The SEE spectra of graphite, obtained as a function of tip bias voltage, are shown to correspond to unoccupied states in the electronic band structure. The SEE spectra of thin gold films demonstrate the capability of identifying (carbonaceous) surface contamination with this technique.

  12. Local secondary-electron emission spectra of graphite and gold surfaces obtained using the Scanning Probe Energy Loss Spectrometer (SPELS)

    Energy Technology Data Exchange (ETDEWEB)

    Lawton, J J; Pulisciano, A; Palmer, R E, E-mail: R.E.Palmer@bham.ac.u [Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom)

    2009-11-25

    Secondary-electron emission (SEE) spectra have been obtained with the Scanning Probe Energy Loss Spectrometer at a tip-sample distance of only 50 nm. Such short working distances are required for the best theoretical spatial resolution (<10 nm). The SEE spectra of graphite, obtained as a function of tip bias voltage, are shown to correspond to unoccupied states in the electronic band structure. The SEE spectra of thin gold films demonstrate the capability of identifying (carbonaceous) surface contamination with this technique.

  13. Current control of the electron beam formed in the magnetron gun with a secondary-emission cathode

    International Nuclear Information System (INIS)

    Dovbnya, A.N.; Reshetnyak, N.G.; Zakutin, V.V.; Chertishchev, I.A.; Romas'ko, V.P.; Dovbnyan, N.A.

    2013-01-01

    Data are reported on electron beam generation and beam current control in two types of secondary-emission cathode magnetron guns. The influence of the magnetic field value and field distribution on the formation of the beam and its parameters has been investigated in the electron energy range between 20 and 150 keV. The influence of local magnetic field variations on the cathode and the electron beam characteristics has been studied. The possibility to control the electron beam current in various ways has been demonstrated

  14. Angular Dependence of the Ion-Induced Secondary Electron Emission for He+ and Ga+ Beams

    NARCIS (Netherlands)

    Castaldo, V.; Withagen, J.; Hagen, C.; Kruit, P.; Van Veldhoven, E.

    2011-01-01

    In recent years, novel ion sources have been designed and developed that have enabled focused ion beam machines to go beyond their use as nano-fabrication tools. Secondary electrons are usually taken to form images, for their yield is high and strongly dependent on the surface characteristics, in

  15. Temperature and energy effects on secondary electron emission from SiC ceramics induced by Xe17+ ions.

    Science.gov (United States)

    Zeng, Lixia; Zhou, Xianming; Cheng, Rui; Wang, Xing; Ren, Jieru; Lei, Yu; Ma, Lidong; Zhao, Yongtao; Zhang, Xiaoan; Xu, Zhongfeng

    2017-07-25

    Secondary electron emission yield from the surface of SiC ceramics induced by Xe 17+ ions has been measured as a function of target temperature and incident energy. In the temperature range of 463-659 K, the total yield gradually decreases with increasing target temperature. The decrease is about 57% for 3.2 MeV Xe 17+ impact, and about 62% for 4.0 MeV Xe 17+ impact, which is much larger than the decrease observed previously for ion impact at low charged states. The yield dependence on the temperature is discussed in terms of work function, because both kinetic electron emission and potential electron emission are influenced by work function. In addition, our experimental data show that the total electron yield gradually increases with the kinetic energy of projectile, when the target is at a constant temperature higher than room temperature. This result can be explained by electronic stopping power which plays an important role in kinetic electron emission.

  16. Time-dependent first-principles study of angle-resolved secondary electron emission from atomic sheets

    Science.gov (United States)

    Ueda, Yoshihiro; Suzuki, Yasumitsu; Watanabe, Kazuyuki

    2018-02-01

    Angle-resolved secondary electron emission (ARSEE) spectra were analyzed for two-dimensional atomic sheets using a time-dependent first-principles simulation of electron scattering. We demonstrate that the calculated ARSEE spectra capture the unoccupied band structure of the atomic sheets. The excitation dynamics that lead to SEE have also been revealed by the time-dependent Kohn-Sham decomposition scheme. In the present study, the mechanism for the experimentally observed ARSEE from atomic sheets is elucidated with respect to both energetics and the dynamical aspects of SEE.

  17. Spurious effects of electron emission from the grids of a retarding field analyser on secondary electron emission measurements. Results on a (111) copper single crystal

    International Nuclear Information System (INIS)

    Pillon, J.; Roptin, D.; Cailler, M.

    1976-01-01

    Spurious effects of a four grid retarding field analyzer were studied for low energy secondary electron measurements. Their behavior was investigated and two peaks in the energy spectrum were interpreted as resulting from tertiary electrons from the grids. It was shown that the true secondary electron peak has to be separated from these spurious peaks. The spectrum and the yields sigma and eta obtained for a Cu(111) crystal after a surface cleanness control by Auger spectroscopy are given

  18. Secondary-electron-emission spectroscopy of tungsten: Angular dependence and phenomenology

    DEFF Research Database (Denmark)

    Willis, Roy F.; Christensen, Niels Egede

    1978-01-01

    spectra from (100), (110), and (111) tungsten surfaces has been studied as a function of polar angle 0°≲Θ≲70° along azimuthal directions φ such that the energy- and angle-resolved SEE current jSEE (E, Ω) effectively scans states throughout the 1 / 48th irreducible body-centered-cubic zone. Calculations...... have been carried out in both "reduced" and "extended" K→ space in order to assess the relative contribution of elastic umklapp scattering to the density distribution of contributing states profiles. The results indicate that the overall secondary-electron yield may be represented as the sum...

  19. Energy- and temperature dependences of secondary electron emission of CsI- and CsBr layers doped with Cd

    International Nuclear Information System (INIS)

    Galij, P.V.; Tsal', N.A.

    1983-01-01

    The energy and temperature dependences of the secondary electron emission coefficient (SEEC) of CsI-Cd-, CsBr-Cd-, CsI-CsBr layers have been studied. The effect of bivalent cadmium impurity on the SEEC value is investigated. It is shown that implantation of small amounts of Cd 2+ impurity into the lattice of the initial monocrystals might increase the SEEC values of the layers. Temperature dependences (TD) of SEEC are measured and the possibility of comparing experimental results with the Dekker formula is analyzed. A conclusion is drawn that the Dekker model well describes the TD of SEEC of doped layers at temperatures T < or approximately 100 deg C. At elevated temperatures., along with secondary electron scattering on phonons, one should take into account their scattering on vacancies

  20. Modeling secondary electron emission from nanostructured materials in helium ion microscope

    International Nuclear Information System (INIS)

    Ohya, K.; Yamanaka, T.

    2013-01-01

    Charging of a SiO 2 layer on a Si substrate during helium (He) beam irradiation is investigated at an energy range relevant to a He ion microscope (HIM). A self-consistent calculation is performed to model the transport of the ions and secondary electrons (SEs), the charge accumulation in the layer, and the electric field below and above the surface. The calculated results are compared with those for gallium (Ga) ions at the same energy and 1 keV electrons corresponding to a low-voltage scanning electron microscope (SEM). The charging of thin layers ( 2 step formed on a Si substrate, a sharp increase in the number of SEs is observed, irrespective of whether a material is charged or not. When the He ions are incident on the bottom of the step, the re-entrance of SEs emitted from the substrate into the sidewall is clearly observed, but it causes the sidewall to be charged negatively. At the positions on the SiO 2 layer away from the step edge, the charging voltage becomes positive with increasing number of Ga ions and electrons. However, He ions do not induce such a voltage due to strong relaxation of positive and negative charges in the Si substrate and their recombination in the SiO 2 layer

  1. Quantitative secondary electron detection

    Science.gov (United States)

    Agrawal, Jyoti; Joy, David C.; Nayak, Subuhadarshi

    2018-05-08

    Quantitative Secondary Electron Detection (QSED) using the array of solid state devices (SSD) based electron-counters enable critical dimension metrology measurements in materials such as semiconductors, nanomaterials, and biological samples (FIG. 3). Methods and devices effect a quantitative detection of secondary electrons with the array of solid state detectors comprising a number of solid state detectors. An array senses the number of secondary electrons with a plurality of solid state detectors, counting the number of secondary electrons with a time to digital converter circuit in counter mode.

  2. Ranges, Reflection and Secondary Electron Emission for keV Hydrogen Ions Incident on Solid N2

    DEFF Research Database (Denmark)

    Børgesen, P.; Sørensen, H.; Hao-Ming, Chen

    1983-01-01

    Ranges were measured for 0.67–3.3 keV/amu hydrogen and deuterium ions in solid N2. Comparisons with similar results for N2-gas confirm the previously observed large phase effect in the stopping cross section. Measurements of the secondary electron emission coefficient for bulk solid N2 bombarded...... by 0.67–9 keV/amu ions also seem to support such a phase effect. It is argued that we may also extract information about the charge state of reflected projectiles....

  3. Dependence of secondary electron emission on the incident angle and the energy of primary electrons bombarding bowl-structured beryllium surfaces

    International Nuclear Information System (INIS)

    Kawata, Jun; Ohya, Kaoru.

    1994-01-01

    A Monte Carlo simulation of the secondary electron emission from beryllium is combined with a model of bowl structure for surface roughness, for analyzing the difference between the electron emissions for normal and oblique incidences. At normal incidence, with increasing the roughness parameter H/W, the primary energy E pm at which the maximum electron yield occurs becomes higher, and at more than the E pm , the decrease in the yield is slower; where H and W are the depth and width of the bowl structure, respectively. The dispersion of incident angle to the microscopic surface causes a small increase in the yield at oblique incidence, whereas the blocking of primary electrons from bombarding the bottom of the structure causes an opposite trend. The strong anisotropy in the polar angular distribution with respect to the azimuthal angle is calculated at oblique incidence. (author)

  4. Surface behavior based on ion-induced secondary electron emission from semi-insulating materials in breakdown evolution

    Energy Technology Data Exchange (ETDEWEB)

    Koc, Emrah; Karakoese, Sema [Department of Physics, Faculty of Sciences, Gazi University, 06500 Ankara (Turkey); Salamov, Bahtiyar G. [Department of Physics, Faculty of Sciences, Gazi University, 06500 Ankara (Turkey); Institute of Physics, National Academy of Science, 1143 Baku (Azerbaijan)

    2013-09-15

    This study focuses on analyses of secondary electron emission (SEE) at semiconductor surfaces when the sufficient conditions of space-time distribution occur. Experimental measurements and calculations with the approach of Townsend coefficients, which include the evaluations of ionization coefficient ({alpha}) and SEE coefficient ({gamma}) were performed in high-ohmic InP, GaAs, and Si semiconductor cathodes with argon and air environments in a wide range of E/N (300-10 000 Td). The direct calculations of {gamma} were carried out to determine the behavior of cold-semiconductor cathode current in a wide range of microgaps (45-525 {mu}m). Paschen curves are interpreted in the dependence of large pd range on breakdown voltage through {gamma} and {alpha}/N. Ion-induced secondary electrons exhibit the direct behaviors affecting the timescale of breakdown evolution in the vicinity of the Paschen minimum during the natural bombardment process with ions of semiconductor cathodes. Also, when {alpha}/N rapidly drops and the excitations of gas atoms densely occupy the gas volume, we determined that the photoelectric effect provides a growth for electron emission from semiconductor surfaces at the breakdown stage at the reduced values of E/N. At all pressures, the emission magnitudes of electrons liberated by semiconductor cathodes into vacuum are found as {gamma}{sub InP} > {gamma}{sub GaAs} > {gamma}{sub Si} in breakdown evolution. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Breakdown of a Space Charge Limited Regime of a Sheath in a Weakly Collisional Plasma Bounded by Walls with Secondary Electron Emission

    International Nuclear Information System (INIS)

    Sydorenko, D.; Smolyakov, A.; Kaganovich, I.; Raitses, Y.

    2009-01-01

    A new regime of plasma-wall interaction is identified in particle-in-cell simulations of a hot plasma bounded by walls with secondary electron emission. Such a plasma has a strongly non-Maxwellian electron velocity distribution function and consists of bulk plasma electrons and beams of secondary electrons. In the new regime, the plasma sheath is not in a steady space charge limited state even though the secondary electron emission produced by the plasma bulk electrons is so intense that the corresponding partial emission coefficient exceeds unity. Instead, the plasma-sheath system performs relaxation oscillations by switching quasiperiodically between the space charge limited and non-space-charge limited states.

  6. Variation in emission and energy recovery concerning incident angle in a scheme recovering high energy ions by secondary electrons

    International Nuclear Information System (INIS)

    Wada, Takayuki; Konno, Shota; Nakamoto, Satoshi; Takeno, Hiromasa; Furuyama, Yuichi; Taniike, Akira

    2016-01-01

    As an energy recovery device for fast protons produced in D- 3 He nuclear fusion, secondary electron (SE) direct energy converter (SEDEC) was proposed in addition to traveling wave direct energy converter (TWDEC). Some protons passing through a TWDEC come into an SEDEC, where protons penetrate to a number of foil electrodes and emitted SEs are recovered. Following to a development of SE orbit control by magnetic field, dependence on incident angle of protons was examined to optimize structure of SEDEC. Based on a theoretical expectation, experiments were performed by changing incident angle of protons and variation in emission and energy recovery were measured. Both emission and energy recovery increased as the angle increased, and differences with theoretical expectation are discussed. (author)

  7. 1D numerical simulation of charge trapping in an insulator submitted to an electron beam irradiation. Part I: Computation of the initial secondary electron emission yield

    International Nuclear Information System (INIS)

    Aoufi, A.; Damamme, G.

    2011-01-01

    The aim of this work is to study by numerical simulation a mathematical modelling technique describing charge trapping during initial charge injection in an insulator submitted to electron beam irradiation. A two-fluxes method described by a set of two stationary transport equations is used to split the electron current j e (z) into coupled forward j e+ (z) and backward j e (z) currents and such that j e (z) = j e+ (z) - j e- (z). The sparse algebraic linear system, resulting from the vertex-centered finite-volume discretization scheme is solved by an iterative decoupled fixed point method which involves the direct inversion of a bi-diagonal matrix. The sensitivity of the initial secondary electron emission yield with respect to the energy of incident primary electrons beam, that is penetration depth of the incident beam, or electron cross sections (absorption and diffusion) is investigated by numerical simulations. (authors)

  8. Measurements of the Secondary Electron Emission from Rare Gases at 4.2K

    CERN Document Server

    Bozhko, Y.; Hilleret, N.

    2013-01-01

    Dependence of the secondary electron yield (SEY) from the primary beam incident energy and the coverage has been measured for neon, argon, krypton and xenon condensed on a target at 4.2K. The beam energy ranged between 100 eV and 3 keV, the maximal applied coverage have made up 12000, 4700, 2500 and 1400 monolayers correspondingly for neon, argon, krypton and xenon. The SEY results for these coverages can be considered as belonging only to investigated gases without influence of the target material. The SEY dependencies versus the primary beam energy for all gases comprise only an ascending part and therefore, the maximal measured SEY values have been obtained for the beam energy of 3keV and have made up 62, 73, 60.5 and 52 for neon, argon, krypton and xenon correspondingly. Values of the first cross-over have made up 21 eV for neon, 14 eV for argon, 12.5 eV for krypton and 10.5 eV for xenon. An internal field appearing across a film due to the beam impact can considerably affect the SEY measurements that dem...

  9. Laboratory Measurements on Charging of Individual Micron-Size Apollo-11 Dust Grains by Secondary Electron Emissions

    Science.gov (United States)

    Tankosic, D.; Abbas, M. M.

    2012-01-01

    Observations made during Apollo missions, as well as theoretical models indicate that the lunar surface and dust grains are electrostatically charged, levitated and transported. Lunar dust grains are charged by UV photoelectric emissions on the lunar dayside and by the impact of the solar wind electrons on the nightside. The knowledge of charging properties of individual lunar dust grains is important for developing appropriate theoretical models and mitigating strategies. Currently, very limited experimental data are available for charging of individual micron-size size lunar dust grains in particular by low energy electron impact. However, experimental results based on extensive laboratory measurements on the charging of individual 0.2-13 micron size lunar dust grains by the secondary electron emissions (SEE) have been presented in a recent publication. The SEE process of charging of micron-size dust grains, however, is found to be very complex phenomena with strong particle size dependence. In this paper we present some examples of the complex nature of the SEE properties of positively charged individual lunar dust grains levitated in an electrodynamic balance (EDB), and show that they remain unaffected by the variation of the AC field employed in the above mentioned measurements.

  10. Secondary electron emission of thin carbon foils under the impact of hydrogen atoms, ions and molecular ions, under energies within the MeV range

    International Nuclear Information System (INIS)

    Vidovic, Z.

    1997-06-01

    This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H 0 , H 2 + and H 3 + projectiles in the 0.25-2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. The phenomenological and theoretical descriptions, as well as a summary of the main theoretical models are the subject of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of a thin carbon foil traversed by an energetic projectile is described in the chapter two. In this chapter are also presented the method and algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with the emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H 2 + and H 3 + polyatomic ions. The results are interpreted in terms of collective effects in the interactions of these ions with solids. The role of the proximity of the protons, molecular ion fragments, upon the amplitude of these collective effects is evidenced from the study of the statistics of forward emission. These experiences allowed us to shed light on various aspects of atom and polyatomic ion inter-actions with solid surfaces. (author)

  11. Energy-filtered real- and k-space secondary and energy-loss electron imaging with Dual Emission Electron spectro-Microscope: Cs/Mo(110)

    Energy Technology Data Exchange (ETDEWEB)

    Grzelakowski, Krzysztof P., E-mail: k.grzelakowski@opticon-nanotechnology.com

    2016-05-15

    Since its introduction the importance of complementary k{sub ||}-space (LEED) and real space (LEEM) information in the investigation of surface science phenomena has been widely demonstrated over the last five decades. In this paper we report the application of a novel kind of electron spectromicroscope Dual Emission Electron spectroMicroscope (DEEM) with two independent electron optical channels for reciprocal and real space quasi-simultaneous imaging in investigation of a Cs covered Mo(110) single crystal by using the 800 eV electron beam from an “in-lens” electron gun system developed for the sample illumination. With the DEEM spectromicroscope it is possible to observe dynamic, irreversible processes at surfaces in the energy-filtered real space and in the corresponding energy-filtered k{sub ǁ}-space quasi-simultaneously in two independent imaging columns. The novel concept of the high energy electron beam sample illumination in the cathode lens based microscopes allows chemically selective imaging and analysis under laboratory conditions. - Highlights: • A novel concept of the electron sample illumination with “in-lens” e- gun is realized. • Quasi-simultaneous energy selective observation of the real- and k-space in EELS mode. • Observation of the energy filtered Auger electron diffraction at Cs atoms on Mo(110). • Energy-loss, Auger and secondary electron momentum microscopy is realized.

  12. Deviation from an inverse cosine dependence of kinetic secondary electron emission for angle of incidence at keV energy

    International Nuclear Information System (INIS)

    Ohya, Kaoru; Kawata, Jun; Mori, Ichiro

    1989-01-01

    Incident angle dependence of kinetic secondary electron emission from metals resulting from incidence of keV ions is investigated by computer simulation with the TRIM Monte Carlo program of ion scattering in matter. The results show large deviations from the inverse cosine dependence, which derives from high-energy approximation, because of a series of elastic collisions of incident ions with metal atoms. In the keV energy region, the elastic collisions have two different effects on the angular dependence for relatively high-energy light ions and for low-energy heavy ions: they result in over- and under-inverse-cosine dependences, respectively. The properties are observed even with an experiment of the keV-neutral incidence on a contaminated surface. In addition, the effects of the thin oxide layer and roughness on the surface are examined with simplified models. (author)

  13. Dependence of secondary electron emission on surface charging in sapphire and polycrystalline alumina: Evaluation of the effective cross sections for recombination and trapping

    International Nuclear Information System (INIS)

    Said, K.; Damamme, G.; Si Ahmed, A.; Moya, G.; Kallel, A.

    2014-01-01

    Highlights: • A novel approach for the analysis of the secondary electron emission in connection with the surface density of trapped charges. • Experimental estimation of the effective cross section for electron–hole recombination and electron trapping in defects. • A simplified charge transport and trapping model which corroborates qualitatively the interpretation of the results. - Abstract: The evolution of the secondary electron emission from sapphire and polycrystalline alumina during electron irradiation, achieved in a scanning electron microscope at room temperature, is derived from the measurement of the induced and the secondary electron currents. The semi-logarithmic plot of the secondary electron emission yield versus the surface density of trapped charges displays a plateau followed by a linear variation. For positive charging, the slope of the linear part, whose value is of about 10 −9 cm 2 , is independent of the primary electron energy, the microstructure and the impurities. It is interpreted as an effective microscopic cross section for electron–hole recombination. For negative charging of sapphire, the slope is associated with an effective electron trapping cross section close to 10 −11 cm 2 , which can be assigned to the dominant impurity trap. These effective values reflect the multiple interactions leading to the accumulation of charges. The yield corresponding to the plateau is controlled by the initial density of impurity traps. A charge transport and trapping >model, based on simplifying assumptions, confirms qualitatively these inferences

  14. Secondary Emission Calorimeter Sensor Development

    Science.gov (United States)

    Winn, David R.; Onel, Yasar

    2012-12-01

    In a Secondary Emission electron(SEe) detector module, Secondary Emission electrons (SEe) are generated from an SE surface/cathode, when charged hadronic or electromagnetic particles, particularly shower particles, penetrate an SE sampling module placed between absorber materials (Fe, Cu, Pb, W etc) in calorimeters. The SE cathode is a thin (10-50 nm thick) film (simple metal-oxides, or other higher yield materials) on the surface of a metal plate, which serves as the entrance “window” to a compact vacuum vessel (metal or metal-ceramic); this SE film cathode is analogous to a photocathode, and the SEe are similar to p.e., which are then amplified by dynodes, also is in a PMT. SE sensor modules can make use of electrochemically etched/machined or laser-cut metal mesh dynode sheets, as large as ~30 cm square, to amplify the Secondary Emission Electrons (SEe), much like those that compact metal mesh or mesh dynode PMT's use to amplify p.e.'s. The construction requirements easier than a PMT, since the entire final assembly can be done in air; there are no critical controlled thin film depositions, cesiation or other oxygen-excluded processes or other required vacuum activation, and consequently bake-out can be a refractory temperatures; the module is sealed by normal vacuum techniques (welding or brazing or other high temperature joinings), with a simple final heated vacuum pump-out and tip-off. The modules envisioned are compact, high gain, high speed, exceptionally radiation damage resistant, rugged, and cost effective, and can be fabricated in arbitrary tileable shapes. The SE sensor module anodes can be segmented transversely to sizes appropriate to reconstruct electromagnetic cores with high precision. The GEANT4 and existing calorimeter data estimated calorimeter response performance is between 35-50 Secondary Emission electrons per GeV, in a 1 cm thick Cu absorber calorimeter, with a gain per SEe > 105 per SEe, and an e/pi<1.2. The calorimeter pulse width is

  15. Revealing by secondary electronic emission of internal electric fields in the yttriated zirconia, irradiated by electrons of 1 MeV

    International Nuclear Information System (INIS)

    Blaise, G.; Paris-11 Univ., 91 - Orsay

    2007-01-01

    The defects due to irradiation in a dielectric material present an activity which can generate macroscopic internal electric fields. A method of investigation of these fields, based on the measure of the Secondary Electronic Emission coefficient, has been developed on a scanning electric microscope. This ones contains two low noise detectors which respectively measure the influence current I IC produced by the charges trapping in the material and the current I SB due to secondary and backscattered electrons which come from the sample. The Secondary Emission coefficient is given by σ=I SB /(I SB +I IC ). The charges trapping during an electrons injection leads to a variation of σ for its intrinsic value σ 0 relative to the uncharged material, until the stationary value σ st =1 corresponding to the auto-regulated condition. This variation is due to the development of an internal electric field produced by the accumulation of the charges trapped during injection. In comparing the evolutions of σ of a fresh yttriated zirconia and of an yttriated zirconia irradiated by electrons of 1 MeV with a dose rate of 10 18 e/cm 2 , it has been revealed that an internal field (due to irradiation) of about 0.5*10 6 V/m exists at a depth of the micron order. This field, directed towards the outside of the material surface, is attributed to the F + defects and to the T centers produced by the impact of the electrons of 1 MeV. In carrying out annealings until 1000 K, a progressive disappearance of this field is observed in the temperature range of 400-600 K, directly due to the F + defects and T centers recovery, as it has been observed by ESR. An internal field three times weaker than the preceding ones has been revealed at a few nm under the surface. Its disappearance from a temperature of 1000 K suggests that it is due to the redistribution of the chemical species into the surface, during the irradiation with electrons of 1 MeV. (O.M.)

  16. Assessing the role of secondary electron emission on the characteristics of 6-cavity magnetrons with transparent cathode through particle-in-cell simulations

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Hao; Joshi, Ravi P., E-mail: rjoshi@odu.edu [Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529-0246 (United States); Prasad, Sarita; Schamiloglu, Edl [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131-0001 (United States); Ludeking, Lars [ATK Mission Systems, 8560 Cinderbed Road, Suite 700, Newington, Virginia 22122 (United States)

    2014-05-21

    Effects of secondary electron emission (SEE) on the performance of a 6-cavity relativistic magnetron with transparent cathodes are probed through particle-in-cell simulations. Appropriate relations for the secondary electron yield have been developed and used. For comparisons, separate simulations have been performed with- and without electron cascading. Simulation results seem to indicate SEE to be detrimental to the power output due to deviations in the starting trajectories of secondary electrons, and the reduced fraction with synchronized rotational velocity. A higher reduction in output power is predicted with electron cascading, though mode competition was not seen at the 0.65 T field. A possible solution to mitigating SEE in magnetrons for high power microwave applications would be to alter the surface properties of emitting electrodes through irradiation, which can lead to graphitic film formation.

  17. Secondary ion emission

    International Nuclear Information System (INIS)

    Krohn, V.E.

    1976-01-01

    The Saha-Langmuir equation that describes the equilibrium emission process, surface ionization, has also been used to describe ion yields observed in the non-equilibrium emission process, sputtering. In describing sputtering, it is probably best to include the potential due to an image charge in the expression for negative as well as positive ion yield and to treat the work function and the temperature as parameters having limited physical significance. Arguments are presented to suggest that sputtered material is not emitted from a plasma. (Auth.)

  18. Secondary electron emission influenced by oxidation on the aluminum surface: the roles of the chemisorbed oxygen and the oxide layer

    Science.gov (United States)

    Li, Jiangtao; Hoekstra, Bart; Wang, Zhen-Bin; Qiu, Jie; Pu, Yi-Kang

    2018-04-01

    A relationship between the apparent secondary electron yield ({γ }{{se}}) and the oxygen coverage/oxide layer thickness on an aluminum cathode is obtained in an experiment under a controlled environment. The apparent secondary electron yield ({γ }{{se}}) is deduced from the breakdown voltage between two parallel plate electrodes in a 360 mTorr argon environment using a simple Townsend breakdown model with the assumption that the variation of the apparent secondary electron yield is dominated by the variation of the argon ion induced processes. The oxygen coverage/oxide layer thickness on the aluminum cathode is measured by a semi in situ x-ray photoemission spectroscopy equipment which is directly attached to the discharge chamber. It is found that three phases exist: (1) in the monomonolayer regime, as the oxygen coverage increases from 0 to 0.3, {γ }{{se}} decreases by nearly 40 % , (2) as the oxygen coverage increases from 0.3 to 1, {γ }{{se}} keeps nearly constant, (3) as the oxide layer thickness increases from about 0.3 nm to about 1.1 nm, {γ }{{se}} increases by 150 % . We propose that, in the submonolayer regime, the chemisorbed oxygen on the aluminum surface causes the decrease of {γ }{{se}} by creating a local potential barrier, which reduces the Auger neutralization rate and the energy gained by the Auger electrons. In the multilayer regime, as the oxide layer grows in thickness, there are three proposed mechanisms which cause the increase of {γ }{{se}}: (1) the work function decreases; (2) resonance neutralization and Auger de-excitation may exist. This is served as another channel for secondary electron production; (3) the kinetic energy of Auger electrons is increased on average, leading to a higher probability for electrons to overcome the surface potential barrier.

  19. Study of the Effects of the Electric Field on Charging Measurements on Individual Micron-size Dust Grains by Secondary Electron Emissions

    Science.gov (United States)

    Tankosic, D.; Abbas, M. M.

    2013-01-01

    The dust charging by electron impact is an important dust charging process in Astrophysical, Planetary, and the Lunar environments. Low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available theoretical models for the calculation of SEE yield applicable for neutral, planar or bulk surfaces are generally based on Sternglass Equation. However, viable models for charging of individual dust grains do not exist at the present time. Therefore, the SEE yields have to be obtained by some experimental methods at the present time. We have conducted experimental studies on charging of individual micron size dust grains in simulated space environments using an electrodynamic balance (EDB) facility at NASA-MSFC. The results of our extensive laboratory study of charging of individual micron-size dust grains by low energy electron impact indicate that the SEE by electron impact is a very complex process expected to be substantially different from the bulk materials. It was found that the incident electrons may lead to positive or negative charging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration. In this paper we give a more elaborate discussion about the possible effects of the AC field in the EDB on dust charging measurements by comparing the secondary electron emission time-period (tau (sub em) (s/e)) with the time-period (tau (sub ac) (ms)) of the AC field cycle in the EDB that we have briefly addressed in our previous publication.

  20. Ionization, charge exchange, and secondary electron emission in the extractor of an LBL/LLL neutral beam source

    International Nuclear Information System (INIS)

    Fink, J.H.; McDowell, C.E.

    1975-01-01

    Using a computer code, bombardment of the electrodes resulting from ionization, charge-exchange, and back-ion emission from the neutralizer cell is studied in the positive-ion extractor region of a Lawrence Berkeley Laboratory/Lawrence Livermore Laboratory (LBL/LLL) neutral beam source. Ion and electron trajectories are presented, grid dissipations estimated, and proposals made for future designs

  1. Complex Role of Secondary Electron Emissions in Dust Grain Charging in Space Environments: Measurements on Apollo 11 and 17 Dust Grains

    Science.gov (United States)

    Abbas, M. M.; Tankosic, D.; Spann, J. F.; LeClair, A. C.

    2010-01-01

    Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with radiation from nearby sources, or by electron/ion collisions by sticking or secondary electron emissions. Knowledge of the dust grain charges and equilibrium potentials is important for understanding of a variety of physical and dynamical processes in the interstellar medium (ISM), and heliospheric, interplanetary, planetary, and lunar environments. The high vacuum environment on the lunar surface leads to some unusual physical and dynamical phenomena involving dust grains with high adhesive characteristics, and levitation and transportation over long distances. It has been well recognized that the charging properties of individual micron/submicron size dust grains are expected to be substantially different from the corresponding values for bulk materials and theoretical models. In this paper we present experimental results on charging of individual dust grains selected from Apollo 11 and Apollo 17 dust samples by exposing them to mono-energetic electron beams in the 10- 400 eV energy range. The charging rates of positively and negatively charged particles of approximately 0.2 to 13 microns diameters are discussed in terms of the secondary electron emission (SEE) process, which is found to be a complex charging process at electron energies as low as 10-25 eV, with strong particle size dependence. The measurements indicate substantial differences between dust charging properties of individual small size dust grains and of bulk materials.

  2. Net current measurements and secondary electron emission characteristics of the Voyager plasma science experiment and their impact on data interpretation

    Science.gov (United States)

    Mcnutt, Ralph L., Jr.

    1988-01-01

    The Voyager Plasma Science (PLS) instrument is capable of returning integral (DC) current measurements, similar in some respects to measurements made with a Langmuir probe or a retarding potential analyzer, although there are significant differences. The integral measurements were made during a calibration sequence in the solar wind, during Cruise Science Maneuvers, and within the magnetospheres of Jupiter and Saturn by Voyager 1. After the failure of the PLS experiment following the Saturn encounter, that instrument was placed in the DC return mode returning possibly usable data from early 1981 through early 1985. The DC return measurements are difficult to interpret and are above threshold values only for relatively large fluxes; the determination of the measured current level is dependent on the operating temperature of the preamplifiers which further complicates the interpretation. Nevertheless, these measurements can be used to determine the efficiency of the suppressor grid at preventing the loss of secondary electrons off the collector plate. Some DC return measurements have been invaluable in aiding in the interpretation of some electron plasma measurements not previously understood. It is found that electron spectra can be significantly modified by the presence of second generation secondary electrons produced by either first generation secondaries or photoelectrons on the support ring of the negative high voltage modulator grid within the instrument housing.

  3. Ion-induced secondary electron emission, optical and hydration resistant behavior of MgO, Mg–Mo–O and Mg–Ce–O thin films

    International Nuclear Information System (INIS)

    Kumar, Ashok; Thota, Subhash; Deva, Dinesh; Kumar, Jitendra

    2014-01-01

    Optical transmittance, hydration resistance and secondary electron emission characteristics of e-beam evaporated pure and Mo- or Ce-containing MgO thin films have been investigated. While the increased grain size and pyramidal columnar morphology following incorporation of molybdenum and cerium in MgO are responsible for the excellent discharge characteristics, emergence of neutral {100} and {110} MgO surfaces preferentially give rise to high optical transmittance (∼ 92–100%) and stability against hydration. Further, addition of Mo (or Ce) in MgO causes significant increase in defect density which, in turn, enhances the photoluminescence (PL) emission from 5-, 4- and 3-coordination sites. The changes lead to lowering of the breakdown voltage and hence improvement in the secondary electron emission (SEE) efficiency. These facts have been supported by ion-induced SEE yield (γ) deduced from the a.c. breakdown voltage observed, taking neon as a discharge gas, and determined semi-empirically as well with Hagstrum's theory based on Auger neutralization process using (i) band offset parameters and surface band gap data derived from X-ray photoelectron spectroscopy signal and (ii) information of defect energy levels obtained from photoluminescence (PL) measurements. The experimental values of neon ion-induced SEE yield (γ) are found to be 0.35, 0.42 and 0.39 for MgO, Mg–Mo–O (x = 0.035) and Mg–Ce–O (x = 0.01) thin films, respectively. - Highlights: • Higher hydration resistance • Increased photoluminescence emission • Higher secondary electron emission

  4. Secondary-electron-emission losses in multistage depressed collectors and traveling-wave-tube efficiency improvements with carbon collector electrode surfaces

    Science.gov (United States)

    Ramins, P.; Ebihara, B. T.

    1986-01-01

    Secondary-electron-emission losses in multistage depressed collectors (MDC's) and their effects on overall traveling-wave-tube (TWT) efficiency were investigated. Two representative TWT's and several computer-modeled MDC's were used. The experimental techniques provide the measurement of both the TWT overall and the collector efficiencies. The TWT-MDC performance was optimized and measured over a wide range of operating conditions, with geometrically identical collectors, which utilized different electrode surface materials. Comparisons of the performance of copper electrodes to that of various forms of carbon, including pyrolytic and iisotropic graphites, were stressed. The results indicate that: (1) a significant improvement in the TWT overall efficiency was obtained in all cases by the use of carbon, rather than copper electrodes, and (2) that the extent of this efficiency enhancement depended on the characteristics of the TWT, the TWT operating point, the MDC design, and collector voltages. Ion textured graphite was found to be particularly effective in minimizing the secondary-electron-emission losses. Experimental and analytical results, however, indicate that it is at least as important to provide a maximum amount of electrostatic suppression of secondary electrons by proper MDC design. Such suppression, which is obtained by ensuring that a substantial suppressing electric field exists over the regions of the electrodes where most of the current is incident, was found to be very effective. Experimental results indicate that, with proper MDC design and the use of electrode surfaces with low secondary-electron yield, degradation of the collector efficiency can be limited to a few percent.

  5. A novel electrostatic ion-energy spectrometer by the use of a proposed ``self-collection'' method for secondary-electron emission from a metal collector

    Science.gov (United States)

    Hirata, M.; Nagashima, S.; Cho, T.; Kohagura, J.; Yoshida, M.; Ito, H.; Numakura, T.; Minami, R.; Kondoh, T.; Nakashima, Y.; Yatsu, K.; Miyoshi, S.

    2003-03-01

    For the purpose of end-loss-ion energy analyses in open-field plasmas, a newly developed electrostatic ion-energy spectrometer is proposed on the basis of a "self-collection" principle for secondary-electron emission from a metal collector. The ion-energy spectrometer is designed with multiple grids for analyzing incident ion energies, and a set of parallelly placed metal plates with respect to lines of ambient magnetic forces in an open-ended device. One of the most important characteristic properties of this spectrometer is the use of our proposed principle of a "self-collection" mechanism due to E×B drifts for secondary electrons emitted from the grounded metal-plate collector by the use of no further additional magnetic systems except the ambient open-ended fields B. The proof-of-principle and characterization experiments are carried out by the use of a test-ion-beam line along with an additional use of a Helmholtz coil system for the formation of open magnetic fields similar to those in the GAMMA 10 end region. The applications of the developed ion-energy spectrometer for end-loss-ion diagnostics in the GAMMA 10 plasma experiments are demonstrated under the conditions with simultaneous incidence of energetic electrons produced by electron-cyclotron heatings for end-loss-plugging potential formation, since these electrons have contributed to disturb these ion signals from conventional end-loss-ion detectors.

  6. Introduction to the physics of electron emission

    CERN Document Server

    Jensen, Kevin L

    2018-01-01

    Electron emission is both a fundamental phenomenon and an enabling component that lies at the very heart of modern science and technology. Written by a recognized authority in the field, with expertise in both electron emission physics and electron beam physics, An Introduction to Electron Emission provides an in-depth look at the physics behind thermal, field, photo, and secondary electron emission mechanisms, how that physics affects the beams that result through space charge and emittance growth, and explores the physics behind their utilization in an array of applications. The book addresses mathematical and numerical methods underlying electron emission, describing where the equations originated, how they are related, and how they may be correctly used to model actual sources for devices using electron beams. Writing for the beam physics and solid state communities, the author explores applications of electron emission methodology to solid state, statistical, and quantum mechanical ideas and concepts r...

  7. Field emission electronics

    CERN Document Server

    Egorov, Nikolay

    2017-01-01

    This book is dedicated to field emission electronics, a promising field at the interface between “classic” vacuum electronics and nanotechnology. In addition to theoretical models, it includes detailed descriptions of experimental and research techniques and production technologies for different types of field emitters based on various construction principles. It particularly focuses on research into and production of field cathodes and electron guns using recently developed nanomaterials and carbon nanotubes. Further, it discusses the applications of field emission cathodes in new technologies such as light sources, flat screens, microwave and X-ray devices.

  8. Secondary emission monitor (SEM) grids.

    CERN Multimedia

    Patrice Loïez

    2002-01-01

    A great variety of Secondary Emission Monitors (SEM) are used all over the PS Complex. At other accelerators they are also called wire-grids, harps, etc. They are used to measure beam density profiles (from which beam size and emittance can be derived) in single-pass locations (not on circulating beams). Top left: two individual wire-planes. Top right: a combination of a horizontal and a vertical wire plane. Bottom left: a ribbon grid in its frame, with connecting wires. Bottom right: a SEM-grid with its insertion/retraction mechanism.

  9. Simulation of secondary emission calorimeter for future colliders

    Science.gov (United States)

    Yetkin, E. A.; Yetkin, T.; Ozok, F.; Iren, E.; Erduran, M. N.

    2018-03-01

    We present updated results from a simulation study of a conceptual sampling electromagnetic calorimeter based on secondary electron emission process. We implemented the secondary electron emission process in Geant4 as a user physics list and produced the energy spectrum and yield of secondary electrons. The energy resolution of the SEE calorimeter was σ/E = (41%) GeV1/2/√E and the response linearity to electromagnetic showers was to within 1.5%. The simulation results were also compared with a traditional scintillator calorimeter.

  10. Sub-band gap photo-enhanced secondary electron emission from high-purity single-crystal chemical-vapor-deposited diamond

    International Nuclear Information System (INIS)

    Yater, J. E.; Shaw, J. L.; Pate, B. B.; Feygelson, T. I.

    2016-01-01

    Secondary-electron-emission (SEE) current measured from high-purity, single-crystal (100) chemical-vapor-deposited diamond is found to increase when sub-band gap (3.06 eV) photons are incident on the hydrogenated surface. Although the light does not produce photoemission directly, the SEE current increases by more than a factor of 2 before saturating with increasing laser power. In energy distribution curves (EDCs), the emission peak shows a corresponding increase in intensity with increasing laser power. However, the emission-onset energy in the EDCs remains constant, indicating that the bands are pinned at the surface. On the other hand, changes are observed on the high-energy side of the distribution as the laser power increases, with a well-defined shoulder becoming more pronounced. From an analysis of this feature in the EDCs, it is deduced that upward band bending is present in the near-surface region during the SEE measurements and this band bending suppresses the SEE yield. However, sub-band gap photon illumination reduces the band bending and thereby increases the SEE current. Because the bands are pinned at the surface, we conclude that the changes in the band levels occur below the surface in the electron transport region. Sample heating produces similar effects as observed with sub-band gap photon illumination, namely, an increase in SEE current and a reduction in band bending. However, the upward band bending is not fully removed by either increasing laser power or temperature, and a minimum band bending of ∼0.8 eV is established in both cases. The sub-band gap photo-excitation mechanism is under further investigation, although it appears likely at present that defect or gap states play a role in the photo-enhanced SEE process. In the meantime, the study demonstrates the ability of visible light to modify the electronic properties of diamond and enhance the emission capabilities, which may have potential impact for diamond-based vacuum electron

  11. Study of secondary electronic emission in some piezo-electric materials: application to ultrasonic visualization; Etude de l'emission electronique secondaire de quelques materiaux piezoelectriques: application a la visualisation ultrasonore

    Energy Technology Data Exchange (ETDEWEB)

    Marini, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    Methods allowing the visualization of acoustic images appear at the moment to be of great interest in the field of non-destructive testing as well as in that of underwater detection. In order to carry out certain calculations on the operation of an ultrasonic camera, it has been necessary to study the secondary electron emission of some piezoelectric materials liable to be incorporated into the equipment. The secondary electron emission of insulators is a rather complex phenomenon; in order to find a rational explanation for the observations made, a theory has been developed for the energy spectrum of the emitted electrons. The experimental results of this work have then been used to build an ultrasonic visualization installation. Some examples of acoustic images which have been visualized are also presented. (author) [French] Les methodes qui permettent de visualiser des images acoustiques trouvent a l'heure actuelle un grand interet dans le domaine du controle non destructif comme dans celui de la detection sous-marine. De maniere a effectuer certains calculs sur le fonctionnement d'une camera ultrasons, il a ete necessaire d'etudier l'emission electronique secondaire de quelques materiaux piezoelectriques susceptibles d'etre utilises dans sa construction. L'emission electronique secondaire des isolants est un phenomene assez complexe et de maniere a trouver des explications coherentes aux observations effectuees, une theorie du spectre energetique des electrons emis a ete elaboree. Une installation de visualisation ultrasonore a alors ete realisee a partir des donnees experimentales de cette etude. Quelques exemples d'images acoustiques visualisees par cette methode sont egalement presentees. (auteur)

  12. Study of secondary electronic emission in some piezo-electric materials: application to ultrasonic visualization; Etude de l'emission electronique secondaire de quelques materiaux piezoelectriques: application a la visualisation ultrasonore

    Energy Technology Data Exchange (ETDEWEB)

    Marini, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    Methods allowing the visualization of acoustic images appear at the moment to be of great interest in the field of non-destructive testing as well as in that of underwater detection. In order to carry out certain calculations on the operation of an ultrasonic camera, it has been necessary to study the secondary electron emission of some piezoelectric materials liable to be incorporated into the equipment. The secondary electron emission of insulators is a rather complex phenomenon; in order to find a rational explanation for the observations made, a theory has been developed for the energy spectrum of the emitted electrons. The experimental results of this work have then been used to build an ultrasonic visualization installation. Some examples of acoustic images which have been visualized are also presented. (author) [French] Les methodes qui permettent de visualiser des images acoustiques trouvent a l'heure actuelle un grand interet dans le domaine du controle non destructif comme dans celui de la detection sous-marine. De maniere a effectuer certains calculs sur le fonctionnement d'une camera ultrasons, il a ete necessaire d'etudier l'emission electronique secondaire de quelques materiaux piezoelectriques susceptibles d'etre utilises dans sa construction. L'emission electronique secondaire des isolants est un phenomene assez complexe et de maniere a trouver des explications coherentes aux observations effectuees, une theorie du spectre energetique des electrons emis a ete elaboree. Une installation de visualisation ultrasonore a alors ete realisee a partir des donnees experimentales de cette etude. Quelques exemples d'images acoustiques visualisees par cette methode sont egalement presentees. (auteur)

  13. Simulation study of radial dose due to the irradiation of a swift heavy ion aiming to advance the treatment planning system for heavy particle cancer therapy: The effect of emission angles of secondary electrons

    Energy Technology Data Exchange (ETDEWEB)

    Moribayashi, Kengo, E-mail: moribayashi.kengo@jaea.go.jp

    2015-12-15

    A radial dose simulation model has been proposed in order to advance the treatment planning system for heavy particle cancer therapy. Here, the radial dose is the dose due to the irradiation of a heavy ion as a function of distances from this ion path. The model proposed here may overcome weak points of paradigms that are employed to produce the conventional radial dose distributions. To provide the radial dose with higher accuracy, this paper has discussed the relationship between the emission angles of secondary electrons and the radial dose. It is found that the effect of emission angles becomes stronger on the radial dose with increasing energies of the secondary electrons.

  14. Influence of Wall-Current-Compensation and Secondary-Electron-Emission on the Plasma Parameters and on the Performance of Electron Cyclotron Resonance Ion Sources

    International Nuclear Information System (INIS)

    Schachter, L.; Dobrescu, S.; Stiebing, K.E.

    2005-01-01

    Axial and radial diffusion processes determine the confinement time in an ECRIS. It has been demonstrated that a biased disk redirects the ion- and electron currents in the source in such a way that the source performance is improved. This effect is due to a partial cancellation of the compensating currents in the conductive walls of the plasma chamber.In this contribution we present an experiment, where these currents were effectively suppressed by using a metal-dielectric (MD) disk instead of the standard metallic disk in the Frankfurt 14-GHz-ECRIS. Lower values of the plasma potential and higher average charge states in the presence of the MD disk as compared to the case of the standard disk indicate that, due to the insulating properties of its dielectric layer the MD disk obviously blocks compensating wall currents better than applying bias to the metallic standard disk.A comparison with results from experiments with a MD liner in the source, covering essentially the complete radial walls of the plasma chamber, clearly demonstrates that the beneficial effect of the liner on the performance of the ECRIS is much stronger than that observed with the MD-disk. In accord with our earlier interpretation, it has to be concluded that the 'liner-effect' is not just the effect of blocking the compensating wall currents but rather has to be ascribed to the unique property of the thin MD liner as a strong secondary electron emitter under bombardment by charged particles

  15. Ion-impact secondary emission in negative corona with photoionization

    Directory of Open Access Journals (Sweden)

    B. X. Lu

    2017-03-01

    Full Text Available A corona discharge measurement system and simulation model are presented to investigate the effects of photoionization and ion-impact secondary emission process in negative corona discharge. The simulation results obtained is shown good agreement with experimental observations. Distribution of electron density along the symmetry axis at three critical moments is shown and the role of photoionization in negative corona discharge is clearly explained. Moreover, the current pulses are also presented under different secondary emission coefficients and the effect of the secondary emission coefficient is discussed.

  16. Study of secondary electron emission from thin carbon targets with swift charged particles: heavy ions, hydrogen ions; Etude experimentale de l`emission electronique secondaire de cibles minces de carbone sous l`impact de projectiles rapides: ions lourds, ions hydrogene (atomiques, moleculaires ou sous forme d`agregats)

    Energy Technology Data Exchange (ETDEWEB)

    Billebaud, A

    1995-07-12

    The main subject of this work is the study of electron emission from the two surfaces of thin solid targets bombarded with swift charged particles. The slowing down of swift ions in matter is mainly due to inelastic interaction with target electrons (ionization, excitation): the energy transfer to target electrons is responsible for the secondary electron emission process. The phenomenological and theoretical descriptions of this phenomena are the subject of the first chapter. We focused on secondary electron emission induced by different kind of projectiles on thin carbon foils. In chapter two we describe hydrogen cluster induced electron emission measurement between 40 and 120 keV/proton. These projectiles, composed of several atoms, allowed us to study and highlight collective effects of the electron emission process. We extended our study of electron emission to molecular (H{sub 2}{sup +}, H{sub 3}{sup +}) and composite (H{sup -}, H{sup 0}) projectiles at higher energies (<= 2 MeV): we have designed an experimental set-up devoted to electron emission statistics measurements which allowed us to study, among others things, the role of projectile electrons in secondary electron emission. This experiment is described in the third chapter. Finally, the fourth chapter describes new measurements of electron emission induced by energetic (13 MeV/u) and highly charged argon ion provided by the medium energy beam line (SME) of GANIL (Caen), which have been analyzed in the framework of a semi-empirical model of secondary electron emission. This set of experiments brings new results on composite projectile interaction with matter, and on the consequences of high energy deposition in solids. (author).

  17. Secondary electron emission from a thin carbon foil induced by H+, He2+ and Li3+ at fixed velocity of 1 MeV/u

    International Nuclear Information System (INIS)

    Ogawa, H.; Sorai, K.; Amano, S.; Ishii, K.; Kaneko, T.

    2013-01-01

    The statistical distributions of the number of forward- and backward-emitted secondary electrons (SE’s) from a thin carbon foil have been measured simultaneously in coincidence with foil-transmitted H + , He 2+ and Li 3+ ions of 1 MeV/u in order to examine the forward–backward correlation of the SE emission (refer to as ‘FB correlation’ hereafter). With these projectiles, we have also measured the energy spectrum of SEs emitted from another carbon foil of similar thickness in the direction around 0° with respect to the incident beams. From the emission statistics data, it is found that both of the inclusive forward and backward SE yields divided by the square of the projectile atomic number (Z p ) decrease with increasing Z p . This trend is qualitatively consistent with previous works by other authors. On the other hand, it has been certified from the energy spectra that the yields of binary electron scale well with Z p 2 . As for the FB correlation, the forward- or backward-emitted SE yield decreases gradually with increasing the number of SEs emitted in the opposite directions. This so-called ‘negative FB correlation’ appears to be pronounced for He 2+ and Li 3+ ions compared with that for H + ions. Since low energy internal SEs do not contribute to the FB correlation, the observed Z p -dependent FB correlation seems to be consistent with the well Z p 2 -scaled production of high energy internal SEs and the decrease of the inclusive forward and backward SE yields with respect to this scaling

  18. Secondary electron images obtained with a standard PEEM set up

    International Nuclear Information System (INIS)

    Benka, O.; Zeppenfeld, P.

    2004-01-01

    Secondary electron images excited by 3 to 4.3 keV electrons are obtained with a standard photoelectron electron emission microscope (PEEM) set up equipped with an imaging energy filter (IEF). The electron gun was mounted on a standard PEEM entrance flange at an angle of 25 o with respect to the sample surface. A low extraction voltage of 500 V was used to minimize the deflection of the electron beam by the PEEM extraction electrode. The secondary electron images are compared to photoelectron images excited by a standard 4.9 eV UV lamp. In the case of a Cu pattern on a Si substrate it is found that the lateral resolution without the IEF is about the same for electron and photon excitation but that the relative electron emission intensities are very different. The use of the IEF-reduces the lateral resolution. Images for secondary electron energies between eV 1 and eV 2 were obtained by setting the IEF to -V 1 and -V 2 ∼ -(V 1 + 5V) potentials and taking the difference of both images. Images up to 100 eV electron energies were recorded. The lateral resolution is in the range of μm. The material contrast obtained in these difference images are discussed in terms of a secondary electron and photoelectron emission model and secondary electron energy spectra measured with a LEED-Auger spectrometer. (author)

  19. Ionic secondary emission SIMS principles and instrumentation

    International Nuclear Information System (INIS)

    Darque-Ceretti, E.; Migeon, H.N.; Aucouturier, M.

    1998-01-01

    The ionic analysis by secondary emission (SIMS) is one of material analysis based on the ions bombardment. That is micro-analysis method in taking into account that the dimensions of the analysed volume are under the micrometer. This paper details in a first part some ionic secondary emission principle to introduce a description of the instrumentation: microprobe, ions production, spectrometers. (A.L.B.)

  20. Development of secondary emission detectors

    International Nuclear Information System (INIS)

    Janouin, Serge.

    1981-11-01

    The complete experimental system used to manufacture targets is presented together with the equipment employed to study the main target and the multiplying targets. The results obtained with the following multiplying targets are given: Alumina + Al; Alumina + Al + nonporous lithium fluoride; Alumina + Al + porous lithium fluoride. Electron production and transport phenomena are analyzed [fr

  1. Secondary electron emission of thin carbon foils under the impact of hydrogen atoms, ions and molecular ions, under energies within the MeV range; Multiplicite des electrons secondaires emis par des cibles minces de carbone sous l'impact de projectiles H0, H2+, H3+ d'energie de l'ordre du MeV

    Energy Technology Data Exchange (ETDEWEB)

    Vidovic, Z

    1997-06-15

    This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H{sup 0}, H{sub 2}{sup +} and H{sub 3}{sup +} projectiles in the 0.25-2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. The phenomenological and theoretical descriptions, as well as a summary of the main theoretical models are the subject of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of a thin carbon foil traversed by an energetic projectile is described in the chapter two. In this chapter are also presented the method and algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with the emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H{sub 2}{sup +} and H{sub 3}{sup +} polyatomic ions. The results are interpreted in terms of collective effects in the interactions of these ions with solids. The role of the proximity of the protons, molecular ion fragments, upon the amplitude of these collective effects is evidenced from the study of the statistics of forward emission. These experiences allowed us to shed light on various aspects of atom and polyatomic ion inter-actions with solid surfaces. (author)

  2. Secondary electron emission of thin carbon foils under the impact of hydrogen atoms, ions and molecular ions, under energies within the MeV range; Multiplicite des electrons secondaires emis par des cibles minces de carbone sous l'impact de projectiles H0, H2+, H3+ d'energie de l'ordre du MeV

    Energy Technology Data Exchange (ETDEWEB)

    Vidovic, Z

    1997-06-15

    This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H{sup 0}, H{sub 2}{sup +} and H{sub 3}{sup +} projectiles in the 0.25-2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. The phenomenological and theoretical descriptions, as well as a summary of the main theoretical models are the subject of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of a thin carbon foil traversed by an energetic projectile is described in the chapter two. In this chapter are also presented the method and algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with the emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H{sub 2}{sup +} and H{sub 3}{sup +} polyatomic ions. The results are interpreted in terms of collective effects in the interactions of these ions with solids. The role of the proximity of the protons, molecular ion fragments, upon the amplitude of these collective effects is evidenced from the study of the statistics of forward emission. These experiences allowed us to shed light on various aspects of atom and polyatomic ion inter-actions with solid surfaces. (author)

  3. Directional Secondary Emission of a Semiconductor Microcavity

    DEFF Research Database (Denmark)

    Langbein, Wolfgang; Jensen, Jacob Riis; Hvam, Jørn Märcher

    2000-01-01

    We investigate the time-resolved secondary emission of a homogeneously broadened microcavity after resonant excitation. The sample consists of a 25nm GaAs single quantum well (QW) in the center of a wedged ¥ë cavity with AlAs/AlGaAs Bragg reflectors, grown by molecular beam epitaxy. At zero detun...

  4. Properties of electronic emissions of semiconductors III-IV in a status of negative electron affinity

    International Nuclear Information System (INIS)

    Piaget, Claude

    1977-01-01

    This research thesis reports the use of various properties (electron emission, photo emission, secondary electron emission) to highlight the relationships between various solid properties (optical, electronic, structural properties), surfaces (clean or covered with adsorbates such as caesium and oxygen) and emission properties (quantum efficiency, energy distribution, and so on). The first part addresses applications, performance, physical properties and technological processes, and also problems related to the physics and chemistry of surfaces and adsorption layers. The second part reports a study of the main electron transport properties in emitters displaying a negative electron affinity, for example GaP. Some aspects of electron excitation by ultra-violet radiations and high energy electrons are studied from UV photo-emission properties and secondary electron emission. Then GaAs and similar pseudo-binary compounds are studied

  5. Secondary emission coefficient dependence on the angle of incidence of primary electrons on CsI and LiF layers. [0. 9 to 3 keV, mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Shabel' nikova, A E; Yasnopol' skii, N L

    1976-08-01

    The angular dependence was studied of the secondary emission coefficient sigma for CsI and LiF dielectrics which have large sigma in conditions of normal incidence of primary electrons. Measurements were taken down to the angle of 85 deg for energies of primary electrons between 0.9 and 3 keV. In the whole range of angles a nonmonotonic angular dependence sigma is observed. The dependence shows itself particularly clearly for CsI at large energies of primary electrons. Such a behaviour is due to the decrease in the depth of yield of inelastically reflected electrons and to the increase in the inelastic reflection coefficient of the substance.

  6. Secondary electron emission and glow discharge properties of 12CaO·7Al2O3 electride for fluorescent lamp applications

    International Nuclear Information System (INIS)

    Watanabe, Satoru; Watanabe, Toshinari; Ito, Kazuhiro; Miyakawa, Naomichi; Ito, Setsuro; Hosono, Hideo; Mikoshiba, Shigeo

    2011-01-01

    12CaO·7Al 2 O 3 electride, a sub-nanoporous compound having a work function of 2.4 eV, was examined as a candidate cathode material in fluorescent lamps. The electron emission yield was higher and the discharge voltage was lower for 12CaO·7Al 2 O 3 than for existing cathode materials such as Ni, Mo or W; therefore, the energy consumption of the fluorescent lamps can be improved using 12CaO·7Al 2 O 3 cathodes. Prototype glow-discharge lamps using 12CaO·7Al 2 O 3 were constructed and exhibited reasonable durability.

  7. Secondary electron emission and glow discharge properties of 12CaO·7Al2O3 electride for fluorescent lamp applications.

    Science.gov (United States)

    Watanabe, Satoru; Watanabe, Toshinari; Ito, Kazuhiro; Miyakawa, Naomichi; Ito, Setsuro; Hosono, Hideo; Mikoshiba, Shigeo

    2011-06-01

    12CaO·7Al 2 O 3 electride, a sub-nanoporous compound having a work function of 2.4 eV, was examined as a candidate cathode material in fluorescent lamps. The electron emission yield was higher and the discharge voltage was lower for 12CaO·7Al 2 O 3 than for existing cathode materials such as Ni, Mo or W; therefore, the energy consumption of the fluorescent lamps can be improved using 12CaO·7Al 2 O 3 cathodes. Prototype glow-discharge lamps using 12CaO·7Al 2 O 3 were constructed and exhibited reasonable durability.

  8. Electron emission from pseudospark cathodes

    International Nuclear Information System (INIS)

    Anders, A.; Anders, S.; Gundersen, M.A.

    1994-01-01

    The pseudospark cathode has the remarkable property of macroscopically homogeneous electron emission at very high current density (>1 kA/cm 2 ) over a large area (some cm 2 ). The model of electron emission presented here is based on the assumption that the pseudospark microscopically utilizes explosive arc processes, as distinct from earlier models of ''anomalous emission in superdense glow discharges.'' Explosive emission similar to vacuum are cathode spots occurs rapidly when the field strength is sufficiently high. The plasma remains macroscopically homogeneous since the virtual plasma anode adapts to the cathode morphology so that the current is carried by a large number of homogeneously distributed cathode spots which are similar to ''type 1'' and ''type 2'' spots of vacuum arc discharges. The net cathode erosion is greatly reduced relative to ''spark gap-type'' emission. At very high current levels, a transition to highly erosive spot types occurs, and this ''arcing'' leads to a significant reduction in device lifetime. Assuming vacuum-arc-like cathode spots, the observed current density and time constants can be easily explained. The observed cathode erosion rate and pattern, recent fast-camera data, laser-induced fluorescence, and spectroscopic measurements support this approach. A new hypothesis is presented explaining current quenching at relatively low currents. From the point of view of electron emission, the ''superdense glow'' or ''superemissive phase'' of pseudosparks represents an arc and not a glow discharge even if no filamentation or ''arcing'' is observed

  9. Experimental study on the secondary emission (atomic and molecular ions, aggregates, electrons) induced by the bombardment of surfaces by means of energetic heavy ions (∼ MeV/u). Effects of the charge state of the projectiles

    International Nuclear Information System (INIS)

    Monart, B.

    1988-05-01

    The ionic and electronic emissions, induced by the sputtering of solid targets (organic and inorganic) with 1 MeV/u projectiles. The time-of-flight spectrometry is applied to the secondary emission analysis. The projectile velocity, the angle of attack (between the beam and the target), and the projectile's incident charge state, are taken into account. It is shown that the secondary emission depends on the charge of the incident ion and on the charge state changement in the material's bulk. A model, applying the theoretical calculations concerning the charge in the material's bulk, is proposed. The existence of an interaction depth, for the incident ion and the material, which depends on the secondary ions type and on the incident ion charge, is suggested. The calculated depth is about 200 angstroms for the aggregates ejected from a CsI target, sputtered with 14 Kr 18+ . The H + yield (coming from ∼ 10 angstroms) is used as a projectile charge probe, at the material surface. The experimental method allows, for the first time, the obtention of the equilibrium charge state in the condensed matter. The same method is applied to determine the non-equilibrium charges in the bulk of thin materials. The results show that, after leaving the material, the projectile presents a post-ionization state [fr

  10. Ion induced high energy electron emission from copper

    International Nuclear Information System (INIS)

    Ruano, G.; Ferron, J.

    2008-01-01

    We present measurements of secondary electron emission from Cu induced by low energy bombardment (1-5 keV) of noble gas (He + , Ne + and Ar + ) and Li + ions. We identify different potential and kinetic mechanisms and find the presence of high energetic secondary electrons for a couple of ion-target combinations. In order to understand the presence of these fast electrons we need to consider the Fermi shuttle mechanism and the different ion neutralization efficiencies.

  11. Unified model of secondary electron cascades in diamond

    International Nuclear Information System (INIS)

    Ziaja, Beata; London, Richard A.; Hajdu, Janos

    2005-01-01

    In this article we present a detailed and unified theoretical treatment of secondary electron cascades that follow the absorption of x-ray photons. A Monte Carlo model has been constructed that treats in detail the evolution of electron cascades induced by photoelectrons and by Auger electrons following inner shell ionizations. Detailed calculations are presented for cascades initiated by electron energies between 0.1 and 10 keV. The present article expands our earlier work [B. Ziaja, D. van der Spoel, A. Szoeke, and J. Hajdu, Phys. Rev. B 64, 214104 (2001), Phys. Rev. B 66, 024116 (2002)] by extending the primary energy range, by improving the treatment of secondary electrons, especially at low electron energies, by including ionization by holes, and by taking into account their coupling to the crystal lattice. The calculations describe the three-dimensional evolution of the electron cloud, and monitor the equivalent instantaneous temperature of the free electron gas as the system cools. The dissipation of the impact energy proceeds predominantly through the production of secondary electrons whose energies are comparable to the binding energies of the valence (40-50 eV) and of the core electrons (300 eV). The electron cloud generated by a 10 keV electron is strongly anisotropic in the early phases of the cascade (t≤1 fs). At later times, the sample is dominated by low energy electrons, and these are scattered more isotropically by atoms in the sample. Our results for the total number of secondary electrons agree with available experimental data, and show that the emission of secondary electrons approaches saturation within about 100 fs following the primary impact

  12. Secondary electron emission and glow discharge properties of 12CaOcenterdot7Al2O3 electride for fluorescent lamp applications

    Directory of Open Access Journals (Sweden)

    Satoru Watanabe, Toshinari Watanabe, Kazuhiro Ito, Naomichi Miyakawa, Setsuro Ito, Hideo Hosono and Shigeo Mikoshiba

    2011-01-01

    Full Text Available 12CaOcenterdot7Al2O3 electride, a sub-nanoporous compound having a work function of 2.4 eV, was examined as a candidate cathode material in fluorescent lamps. The electron emission yield was higher and the discharge voltage was lower for 12CaOcenterdot7Al2O3 than for existing cathode materials such as Ni, Mo or W; therefore, the energy consumption of the fluorescent lamps can be improved using 12CaOcenterdot7Al2O3 cathodes. Prototype glow-discharge lamps using 12CaOcenterdot7Al2O3 were constructed and exhibited reasonable durability.

  13. Basic aspects of secondary electron distributions

    International Nuclear Information System (INIS)

    Kim, Y.K.

    1975-07-01

    Graphical methods proposed by Platzman and by Fano are applied to the analysis of the basic features observed in secondary electron spectra. These methods are useful not only in checking the consistency of experimental data, but also in extrapolating the spectra to the range of primary- and secondary-electron energies not covered by experiments. Illustrative examples are presented for He, Ne, and NO. (U.S.)

  14. Ultrafast secondary emission x-ray imaging detectors

    International Nuclear Information System (INIS)

    Akkerman, A.; Gibrekhterman, A.; Majewski, S.

    1991-07-01

    Fast high accuracy, x-ray imaging at high photon flux can be achieved when coupling thin solid convertors to gaseous electron multipliers, operating at low gas pressures. Secondary electron emitted from the convertor foil are multiplied in several successive amplification elements. The obvious advantage of solid x-ray detectors, as compared to gaseous conversion, are the production of parallax-free images and the fast (subnanoseconds) response. These x-ray detectors have many potential applications in basic and applied research. Of particular interest is the possibility of an efficient and ultrafast high resolution imaging of transition radiation,with a reduced dE/dx background. We present experimental results on the operation of the secondary emission x-ray (SEX) detectors, their detection efficiency, localization and time resolution. The experimental work is accompanied by mathematical modelling and computer simulation of transition radiation detectors based on CsI transition radiation convertors. (author)

  15. Beam-ripple monitor with secondary electrons

    International Nuclear Information System (INIS)

    Sato, Shinji; Kanazawa, Mitsutaka; Noda, Koji; Takada, Eiichi; Komiyama, Akihito; Ichinohe, Ken-ichi; Sano, Yoshinobu

    1997-01-01

    To replace the scintillation-ripple monitor, we have developed a new monitor with a smaller destructive effect on the beam. In this monitor, we use secondary electrons emitted from an aluminum foil with a thickness of 2 μm. The signals of secondary electrons are amplified by an electron multiplier having a maximum gain of 10 6 . By using the new monitor, we could clearly observe the beam ripple with a beam intensity of 3.6x10 8 pps (particle per second). This monitor can also be used as an intensity monitor in the range of 10 4 - 10 9 pps. (author)

  16. Negative secondary ion emission from oxidized surfaces

    International Nuclear Information System (INIS)

    Gnaser, H.; Kernforschungsanlage Juelich G.m.b.H.

    1984-01-01

    The emission of negative secondary ions from 23 elements was studied for 10 keV O 2 + and 10 keV In + impact at an angle of incidence of 45 0 . Partial oxidation of the sample surfaces was achieved by oxygen bombardment and/or by working at a high oxygen partial pressure. It was found that the emission of oxide ions shows an element-characteristic pattern. For the majority of the elements investigated these features are largely invariant against changes of the surface concentration of oxygen. For the others admission of oxygen strongly changes the relative intensities of oxide ions: a strong increase of MO 3 - signals (M stands for the respective element) is accompanied by a decrease of MO - and M - intensities. Different primary species frequently induce changes of both the relative and the absolute negative ion intensities. Carbon - in contrast to all other elements - does not show any detectable oxide ion emission but rather intense cluster ions Csub(n) - (detected up to n=12) whose intensities oscillate in dependence on n. (orig./RK)

  17. Electron emission from materials at low excitation energies

    International Nuclear Information System (INIS)

    Urma, N.; Kijek, M.; Millar, J.J.

    1996-01-01

    Full text: An experimental system has been designed and developed with the purpose of measuring the total electron emission yield from materials at low energy excitation. In the first instance the reliability of the system was checked by measuring the total electron emission yield for a well defined surface (aluminium 99.45%). The obtained data was in the expected range given by the literature, and consequently the system will be used further for measuring the total electron yield for a range of materials with interest in the instrumentation industry. We intend to measure the total electron emission yield under electron bombardment as a function of incident electron energy up to 1200 eV, angle of incidence, state of the surface and environment to which the surface has been exposed. Dependence of emission on total electron irradiated dose is also of interest. For many practical application of the 'Secondary Electron Emission', the total electron yield is desired to be as large as possible. The above phenomenon has practical applicability in electron multiplier tube and Scanning electron microscopy - when by means of the variation of the yield of the emitted electrons one may produce visible images of small sample areas. The electron multiplier tube, is a device which utilises the above effect to detect and amplify both single particles and low currents streams of charged particles. The majority of electron tubes use electrons with low energy, hundreds of eV. Not a lot has been published in the literature about this regime and also about the emission when the impinging electrons have small energy, up to 1 KeV. The information obtained from the experimental measurements concerning the total electron emission yield is used to asses the investigated materials as a potential electron emitting surfaces or dynodes in an electron multiplier tube

  18. Detection of fission fragments by secondary emission; Detection des fragments de fission par emission secondaire

    Energy Technology Data Exchange (ETDEWEB)

    Audias, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    This fission fragment detecting apparatus is based on the principle that fragments traversing a thin foil will cause emission of secondary electrons. These electrons are then accelerated (10 kV) and directly detected by means of a plastic scintillator and associated photomultiplier. Some of the advantages of such a detector are, its rapidity, its discriminating power between alpha particles and fission fragments, its small energy loss in detecting the fragments and the relatively great amount of fissionable material which it can contain. This paper is subdivided as follows: a) theoretical considerations b) constructional details of apparatus and some experimental details and c) a study of the secondary emission effect itself. (author) [French] Le detecteur de fragments de fission que nous avons realise est base sur le principe de l'emission secondaire produite par les fragments de fission traversant une feuille mince: les electrons secondaires emis sont acceleres a des tensions telles (de l'ordre de 10 kV), qu'ils soient directement detectables par un scintillateur plastique associe a un photomultiplicateur. L'interet d'un tel detecteur reside: dans sa rapidite, sa tres bonne discrimination alpha, fission, la possibilite de detecter les fragments de fission avec une perte d'energie pouvant rester relativement faible, et la possibilite d'introduire des quantites de matiere fissile plus importantes que dans les autres types de detecteurs. Ce travail comporte: -) un apercu bibliographique de la theorie du phenomene, -) realisation et mise au point du detecteur avec etude experimentale de quelques parametres intervenant dans l'emission secondaire, -) etude de l'emission secondaire (sur la face d'emergence des fragments de fission) en fonction de l'energie du fragment et en fonction de l'epaisseur de matiere traversee avant emission secondaire, et -) une etude comparative de l'emission secondaire sur la face d'incidence et sur la face d'emergence des fragments de

  19. Secondary emission scintillation counter for microdosimetry at the nanometer level

    International Nuclear Information System (INIS)

    Goldhagen, P.

    1987-01-01

    The secondary emission scintillation (SES) counter is a device designed to count the positive ions of charged-particle tracks in gas volumes simulating sites in tissue with diameters of the order of 1 nanometer. Based on suggestions by H.H. Rossi and A.M. Kellerer, the basic idea of the device was developed by A. Kosiara, M. Biavati, and R.D. Colvett in the late 1970s. The device was substantially modified in 1982, but work on it was suspended before the new version could be tested, in order to devote full-time effort to rebuilding RARAF. Work resumed on the SES counter in 1986. A diagram of the prototype SES counter now being tested is shown. A weak electric field in the cylindrical collection region of the device drifts ions from a track to a small region (less than 1 mm) of high electric field where they are accelerated by several kilovolts onto a dynode, producing secondary electrons. The secondary electrons are then accelerated onto a plastic scintillator, and the resulting light is detected by a photomultiplier. The passage of a charged particle is established by a solid state detector, which triggers electronics detecting coincidences and measuring the timing and amplitude of pulses from the photomultiplier

  20. Secondary Aluminum Production: National Emission Standards for Hazardous Air Pollutants

    Science.gov (United States)

    National emission standards for hazardous air pollutants (NESHAP) for new and existing sources at secondary aluminum production facilities. Includes rule history, summary, federal register citations and implementation information.

  1. ROLE OF DIAMOND SECONDARY EMITTERS IN HIGH BRIGHTNESS ELECTRON SOURCES

    International Nuclear Information System (INIS)

    2005-01-01

    In this paper we explore the possibility of using diamond secondary emitter in a high average current electron injector to amplify the current from the photocathode and to isolate the cathode and the injector from each other to increase the life time of the cathode and preserve the performance of the injector. Secondary electron yield of 225 and current density of 0.8 a/cm 2 have been measured in the transmission mode from type 2 a natural diamond. Although the diamond will be heated during normal operation in the injector, calculations indicate that by cryogenically cooling the diamond, the temperature gradient along the diamond can be maintained within the acceptable range. The electron energy and temporal distributions are expected to be narrow from this device resulting in high brightness beams. Plans are underway to measure the SEY in emission mode, fabricate photocathode-diamond capsule and test diamond and capsule in superconducting RF injector

  2. Carbon buildup monitoring using RBS: Correlation with secondary electrons

    International Nuclear Information System (INIS)

    Aguilera, E.F.; Rosales, P.; Martinez-Quiroz, E.; Murillo, G.; Fernandez, M.C.

    2006-01-01

    The RBS technique is applied to solve the problem of on-line monitoring of the carbon deposited on a thin backed foil under ion bombardment. An iterative method is used to reliably extract quantities such as number of projectiles and target thickness in spite of beam energy changes and detector unstabilities. Experimental values for secondary electron yields are also deduced. Results are reported for the thickness variation of thin carbon foils bombarded with carbon ions of energies between 8.95 and 13 MeV. A linear correlation of this variation is found with both, the ion fluence at target and the number of secondary electrons emitted. The correlation exists even though a wide range of beam currents, beam energies and bombarding times was used during the experiment. The measured electron yields show evidence for a change in the emission process between the original foils and the deposited layer, possibly due to a texture change

  3. Electron emission mechanism of carbon fiber cathode

    International Nuclear Information System (INIS)

    Liu Lie; Li Limin; Wen Jianchun; Wan Hong

    2005-01-01

    Models of electron emission mechanism are established concerning metal and carbon fiber cathodes. Correctness of the electron emission mechanism was proved according to micro-photos and electron scanning photos of cathodes respectively. The experimental results and analysis show that the surface flashover induces the electron emission of carbon fiber cathode and there are electron emission phenomena from the top of the carbon and also from its side surface. In addition, compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fiber cathode is slower and the pulse duration of output microwave can be widened by using the carbon fiber cathode. (authors)

  4. Surface characterization by energy distribution measurements of secondary electrons and of ion-induced electrons

    International Nuclear Information System (INIS)

    Bauer, H.E.; Seiler, H.

    1988-01-01

    Instruments for surface microanalysis (e.g. scanning electron or ion microprobes, emission electron or ion microscopes) use the current of emitted secondary electrons or of emitted ion-induced electrons for imaging of the analysed surface. These currents, integrating over all energies of the emitted low energy electrons, are however, not well suited to surface analytical purposes. On the contrary, the energy distribution of these electrons is extremely surface-sensitive with respect to shape, size, width, most probable energy, and cut-off energy. The energy distribution measurements were performed with a cylindrical mirror analyser and converted into N(E), if necessary. Presented are energy spectra of electrons released by electrons and argon ions of some contaminated and sputter cleaned metals, the change of the secondary electron energy distribution from oxidized aluminium to clean aluminium, and the change of the cut-off energy due to work function change of oxidized aluminium, and of a silver layer on a platinum sample. The energy distribution of the secondary electrons often shows detailed structures, probably due to low-energy Auger electrons, and is broader than the energy distribution of ion-induced electrons of the same object point. (author)

  5. Electronic Reporting of Air Emissions

    Science.gov (United States)

    EPA regulations require affected sources to perform emissions source tests, conduct continuous emissions monitoring, and submit compliance and emissions reports. This site provides technical resources and access for providing such submissions.

  6. Measurement of photoemission and secondary emission from laboratory dust grains

    Science.gov (United States)

    Hazelton, Robert C.; Yadlowsky, Edward J.; Settersten, Thomas B.; Spanjers, Gregory G.; Moschella, John J.

    1995-01-01

    The overall goal of this project is experimentally determine the emission properties of dust grains in order to provide theorists and modelers with an accurate data base to use in codes that predict the charging of grains in various plasma environments encountered in the magnetospheres of the planets. In general these modelers use values which have been measured on planar, bulk samples of the materials in question. The large enhancements expected due to the small size of grains can have a dramatic impact upon the predictions and the ultimate utility of these predictions. The first experimental measurement of energy resolved profiles of the secondary electron emission coefficient, 6, of sub-micron diameter particles has been accomplished. Bismuth particles in the size range of .022 to .165 micrometers were generated in a moderate pressure vacuum oven (average size is a function of oven temperature and pressure) and introduced into a high vacuum chamber where they interacted with a high energy electron beam (0.4 to 20 keV). Large enhancements in emission were observed with a peak value, delta(sub max) = 4. 5 measured for the ensemble of particles with a mean size of .022 micrometers. This is in contrast to the published value, delta(sub max) = 1.2, for bulk bismuth. The observed profiles are in general agreement with recent theoretical predictions made by Chow et al. at UCSD.

  7. Electron cyclotron emission from the PLT tokamak

    International Nuclear Information System (INIS)

    Hosea, J.; Arunasalam, V.; Cano, R.

    1977-07-01

    Experimental measurements of electron cyclotron emission from the PLT tokamak plasma reveal that black-body emission occurs at the fundamental frequency. Such emission, not possible by direct thermal excitation of electromagnetic waves, is herein attributed to thermal excitation of electrostatic (Bernstein) waves which then mode convert into electromagnetic waves. The local feature of the electrostatic wave generation permits spatially and time resolved measurements of electron temperature as for the second harmonic emission

  8. Ion induced high energy electron emission from copper

    Energy Technology Data Exchange (ETDEWEB)

    Ruano, G. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina)], E-mail: gdruano@ceride.gov.ar; Ferron, J. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina); Departamento de Ingenieria de Materiales, Facultad de Ingenieria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina)

    2008-11-15

    We present measurements of secondary electron emission from Cu induced by low energy bombardment (1-5 keV) of noble gas (He{sup +}, Ne{sup +} and Ar{sup +}) and Li{sup +} ions. We identify different potential and kinetic mechanisms and find the presence of high energetic secondary electrons for a couple of ion-target combinations. In order to understand the presence of these fast electrons we need to consider the Fermi shuttle mechanism and the different ion neutralization efficiencies.

  9. Methods for measurement of electron emission yield under low energy electron-irradiation by collector method and Kelvin probe method

    Energy Technology Data Exchange (ETDEWEB)

    Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie [Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse, France and Fondation STAE, 4 allee Emile Monso, BP 84234-31432, Toulouse Cedex 4 (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France)

    2010-09-15

    Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40{+-}1 eV.

  10. Methods for measurement of electron emission yield under low energy electron-irradiation by collector method and Kelvin probe method

    International Nuclear Information System (INIS)

    Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie

    2010-01-01

    Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40±1 eV.

  11. Jean’s instability in a complex plasma in presence of secondary electrons and nonthermal ions

    International Nuclear Information System (INIS)

    Sarkar, Susmita; Maity Saumyen

    2013-01-01

    In this paper we have investigated the effect of secondary electron emission and nonthermality of ion velocity distribution simultaneously on Jean’s instability in a complex plasma in presence of negatively charged dust grains. Primary and secondary electron temperatures are assumed to be equal. Thus plasma under consideration consists of Boltzmann distributed electrons, nonthermal ions and negatively charged dust grains. The dust grain component is modeled by continuity and momentum equations. From the linear dispersion relation we have calculated the real frequency and growth rate of the Jean’s mode. Numerically it is found that for lower values of the nonthermal parameter Jean’s instability is higher for higher secondary electron emission whereas the effect of secondary electron emission on Jean’s instability becomes insignificant for higher values of the nonthermal parameter. (author)

  12. Study of the secondary electron emission during bombardment of metal targets by positive D{sup +} and D{sub 2}{sup +} ions (1960); Etude de l'emission secondaire d'electrons au cours du bombardement de cibles metalliques par des ions positifs D{sup +} et D{sub 2}{sup +} (1960)

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires; Prelec, K [Institut Rudjer Boskovic, Zagreb (Croatia)

    1960-07-01

    The secondary electron yield {gamma}-bar due to primary positive ions D{sup +} and D{sup +}{sub 2} has been measured in the 70 keV to 300 keV ion energy range. Several metallic targets have been used. The variation of this yield with the angle of incidence is proportional to sec {theta} where {theta} is the angle between the beam of primary ions and the normal to the target surface. The values {gamma}-bar decrease for increasing energy ions. At a given energy all the targets tried gave approximately the same electron yield. (author) [French] Le facteur d'emission secondaire a ete mesure pour des ions positifs D{sup +} et D{sup +}{sub 2} ayant une energie comprise entre 70 keV et 300 keV, sur differentes cibles metalliques. La variation de ce facteur avec l'angle d'incidence suit une loi de la forme {gamma}{sub 0} sec {theta}, {theta} etant l'angle entre le faisceau et la normale a la cible. Les valeurs de {gamma}-bar trouvees decroissent lorsque l'energie des ions incidents augmente, mais sont assez voisines les unes des autres, a une energie donnee, pour les differentes cibles essayees. (auteur)

  13. Electron cyclotron emission imaging in tokamak plasmas

    NARCIS (Netherlands)

    Munsat, T.; Domier, C.W.; Kong, X. Y.; Liang, T. R.; N C Luhmann Jr.,; Tobias, B. J.; Lee, W.; Park, H. K.; Yun, G.; Classen, I.G.J.; Donne, A. J. H.

    2010-01-01

    We discuss the recent history and latest developments of the electron cyclotron emission imaging diagnostic technique, wherein electron temperature is measured in magnetically confined plasmas with two-dimensional spatial resolution. The key enabling technologies for this technique are the

  14. An experimental assessment of methods used to compute secondary electron emission yield for tungsten and molybdenum electrodes based on exposure to Alcator C-Mod scrape-off layer plasmas

    Science.gov (United States)

    McCarthy, W.; LaBombard, B.; Brunner, D.; Kuang, A. Q.

    2018-03-01

    Plasma potentials computed from Langmuir probe data rely on a method to account for secondary electron emission (SEE) from the electrodes. However, significant variations exist among published models for SEE and the reported experimental parameters used to evaluate them. As a means to critically assess SEE computation methods, two of four tungsten electrodes on a Langmuir-Mach probe head were replaced with molybdenum and exposed to Alcator C-Mod boundary plasmas where electron temperatures exceed 50 eV and SEE becomes significant. In this situation, plasma potentials computed for either material should be identical—the SEE evaluation method should properly account for the differences in SEE yields. Of the six methods used to compute SEE, two are found to produce consistent results (Sternglass model with Bronstein experimental parameters and Young-Dekker model with Bronstein experimental parameters). In contrast, the method previously used for C-Mod data analysis (Sternglass model with Kollath parameters) was found to be inconsistent. We have since adopted Young-Dekker-Bronstein as the preferred method.

  15. Derivation of a semi-empirical formula for the quantum efficiency of forward secondary electron emission from γ-irradiated metals. 2

    International Nuclear Information System (INIS)

    Nakamura, Masamoto; Katoh, Yoh

    1994-01-01

    An empirical formula for the quantum efficiency of electrons irradiated with 60 Co γ-rays was reported in a previous paper, but its physical meaning was not made clear. Then, a simple model was assumed, from which a formula for calculating the efficiency was theoretically derived. Some parameters in the formula were determined so that the calculated results might fit the experimental data. The above empirical formula was shown to be the same as the formula physically derived this time. Results from the semiempirical formula and experimental data for Al and Pb sample were in agreement within the limits of 5%. (author)

  16. Comparison of the secondary electrons produced by proton and electron beams in water

    Energy Technology Data Exchange (ETDEWEB)

    Kia, Mohammad Reza, E-mail: m-r-kia@aut.ac.ir; Noshad, Houshyar [Department of Energy Engineering and Physics, Amirkabir University of Technology (Tehran Polytechnic), P.O. Box 15875-4413, Hafez Avenue, Tehran (Iran, Islamic Republic of)

    2016-05-15

    The secondary electrons produced in water by electron and proton beams are compared with each other. The total ionization cross section (TICS) for an electron impact in water is obtained by using the binary-encounter-Bethe model. Hence, an empirical equation based on two adjustable fitting parameters is presented to determine the TICS for proton impact in media. In order to calculate the projectile trajectory, a set of stochastic differential equations based on the inelastic collision, elastic scattering, and bremsstrahlung emission are used. In accordance with the projectile trajectory, the depth dose deposition, electron energy loss distribution in a certain depth, and secondary electrons produced in water are calculated. The obtained results for the depth dose deposition and energy loss distribution in certain depth for electron and proton beams with various incident energies in media are in excellent agreement with the reported experimental data. The difference between the profiles for the depth dose deposition and production of secondary electrons for a proton beam can be ignored approximately. But, these profiles for an electron beam are completely different due to the effect of elastic scattering on electron trajectory.

  17. Secondary emissions during fiber laser cutting of nuclear material

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, A., E-mail: beatriz.mendes.lopez@gmail.com [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); Assunção, E. [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); European Federation for Welding, Joining and Cutting, Porto Salvo 2740-120 (Portugal); Pires, I. [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); Quintino, L. [IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa (Portugal); European Federation for Welding, Joining and Cutting, Porto Salvo 2740-120 (Portugal)

    2017-04-15

    The laser process has been studied for dismantling work for more than 10 years, however there is almost no data available concerning secondary emissions generated during the process. These emissions are inevitable during the laser cutting process and can have detrimental effects in human health and in the equipment. In terms of safety, for nuclear decommissioning, is crucial to point out ways of controlling the emissions of the process. This paper gives indications about the parameters to be used in order to reduce these secondary emissions and about the influence of these parameters on the particles size distribution. In general, for producing minimal dross and fume emissions the beam focus should be placed on the surface of the material. The higher percentage of secondary emissions which present higher diameter, increases approximately linearly with the stand-off distance and with the use of low air pressure.

  18. Electron emission at the rail surface

    International Nuclear Information System (INIS)

    Thornhill, L.; Battech, J.

    1991-01-01

    In this paper the authors examine the processes by which current is transferred from the cathode rail to the plasma armature in an arc-driven railgun. Three electron emission mechanisms are considered, namely thermionic emission, field-enhanced thermionic emission (or Schottky emission), and photoemission. The author's calculations show that the dominant electron emission mechanism depends, to a great extent, on the work function of the rail surface, the rail surface temperature, the electric field at the rail surface, and the effective radiation temperature of the plasma. For conditions that are considered to be typical of a railgun armature, Schottky emission is the dominant electron emission mechanism, providing current densities on the order of 10 9 A/m 2

  19. Secondary emission detectors for fixed target experiments at Fermilab

    International Nuclear Information System (INIS)

    Drucker, R.; Ford, R.; Tassotto, G.

    1998-02-01

    A description of a Secondary Emission Electron Detector (SEED) is given. The SEEDs provide accurate profiles and positions at small wire spacing (125-500 mm) in a high energy, high rate environment that exceeds the capabilities of traditional segmented wire ion chambers (SWICs). This device has been designed and constructed to monitor beam position and profile of two fixed target beamlines, namely, KTeV (FNAL E-799, E-832) with an average beam sigma at target of 0.22 mm and NuTeV (FNAL E-815) with a sigma = 0.6 mm. KTeV took beam at an intensity of up to 5E12 800 GeV protons over a 20 sec spill and NuTeV received 1E13 800 GeV protons in five pings/spill

  20. Fragment ion and electron emission from C sub 6 sub 0 by fast heavy ion impact

    CERN Document Server

    Mizuno, T; Itoh, A; Tsuchida, H; Nakai, Y

    2003-01-01

    Correlation between electron emission and fragmentation of C sub 6 sub 0 was studied using 847keV Si sup + ions. Mass distribution of fragment ions, number distribution of secondary electrons, and final charge distribution of outgoing projectiles were successfully measured by means of a triple coincidence time-of-flight method. Strong correlation was observed for electron emission and fragmentation.

  1. Nanopillar arrays on semiconductor membranes as electron emission amplifiers.

    Science.gov (United States)

    Qin, Hua; Kim, Hyun-Seok; Blick, Robert H

    2008-03-05

    A new transmission-type electron multiplier was fabricated from silicon-on-insulator (SOI) material by integrating an array of one-dimensional (1D) silicon nanopillars onto a two-dimensional (2D) silicon membrane. Primary electrons are injected into the nanopillar-membrane (NPM) system from the flat surface of the membrane, while electron emission from the nanopillars is probed by an anode. The secondary electron yield (SEY) from the nanopillars in the current device is found to be about 1.8 times that of the plain silicon membrane. This gain in electron number is slightly enhanced by the electric field applied from the anode. Further optimization of the dimensions of the NPM and an application of field emission promise an even higher gain for detector applications and allow for probing of electronic/mechanical excitations in an NPM system stimulated by incident particles or radiation.

  2. Analysis of emissions from prebunched electron beams

    Directory of Open Access Journals (Sweden)

    Jia Qika

    2017-07-01

    Full Text Available The emissions of the prebunched electron beam, including the coherent spontaneous emission and the self-amplified stimulated emission, are analyzed by using one-dimensional FEL theory. Neglecting the interaction of the electrons and the radiation field, the formula of the coherent spontaneous emission is given, the power of which is proportional to the square of the initial bunching factor and of the undulator length. For the general emission case of the prebunched electron beam, the evolution equation of the optical field is deducted. Then the analytical expression of the emission power is obtained for the resonant case; it is applicable to the regions from the low gain to the high gain. It is found that when the undulator length is shorter than four gain lengths, the emission is just the coherent spontaneous emission, and conversely, it is the self-amplified stimulated emission growing exponentially. For the nonresonant prebunched electron beam, the variations of the emission intensity with the detuning parameter for different interaction length are presented. The radiation field characters of the prebunched electron beam are discussed and compared with that of the seeded FEL amplifier.

  3. Effect of Cs and Li atom adsorption on MgO: Secondary emission and work function

    International Nuclear Information System (INIS)

    Bagraev, N.T.; Borisov, V.L.

    1980-01-01

    Adsorption of Cs and Li atoms on the surface of single crystal magnesium oxide films has been investigated using Auger, LEED and contact difference techniques. A decreased work function for a single crystal MgO film grown on the Mo (100) face was observed to be accompanied by an increased secondary electron emission yield shown to be due to a larger escape depth for secondary electrons. LEED showed well ordered layers of adsorbed Cs on the MgO film surface. A model to explain the behaviour of Cs atoms on the film surface is proposed. It is shown that the stability of the Cs coating is not dependent on a prolonged bombardment of the film by incident electron beams of high current density. Depositing and implanting of thin single crystal MgO films with Li were found to result in an increased secondary electron emission yield, with Li adsorption on the MgO film surface being disordered. (orig.)

  4. Thermalization of secondary electrons under AMSGEMP conditions

    International Nuclear Information System (INIS)

    Bloomberg, H.W.; Pine, V.W.

    1984-01-01

    A Monte Carlo algorithm is used to determine the time behavior of source secondary electrons for ranges of the electric field to pressure ratio E/p of interest in AMSGEMP. The algorithm contains a very detailed cross section set describing electron interactions with the background gas. The authors show that the delay in the attainment of the peak time independent ionization frequency (or ionization coefficient) may result in negligible ionization over times of interest. In any case the behavior is shown to behave much differently than in examples where limited cross section sets, common in currently employed predictive codes, are employed. In particular, the importance of momentum transfer is indicated. A critique of the scaling implications of the phenomena is made

  5. A multiwire secondary emission profile monitor for small emittance beams

    International Nuclear Information System (INIS)

    Chehab, R.; Bonnard, J.; Humbert, G.; Leblond, B.; Saury, J.L.

    1985-01-01

    A secondary emission monitor using two multiwire grids separated by a positively biased collector has been constructed and tested with a 1 GeV electron beam at the Orsay Linac. The monitor installed just before the electron-positron converter has 8 gold-plated-tungsten wires of 0.1 mm diameter equally spaced 0.2 mm apart in each plane. Each wire is connected with an integrator using a low-bias current operational amplifier. The wire planes and the collector are moved into the beam by a stepping motor : that allows beam-position verification. We measured narrow profiles for 1 Amp peak current pulses of 30 nanoseconds width. Profiles are displayed on a scope and allow emittance determination by the three gradient method. Such a monitor is very useful to control the electron beam position and dimensions on the converter, because the positron source dimensions are rather bigger than those of the incident beam and the geometrical acceptance of the positron Linac is limited

  6. Studies of electron cyclotron emission on text

    International Nuclear Information System (INIS)

    Gandy, R.F.

    1990-07-01

    The Auburn University electron cyclotron emission (ECE) system has made many significant contributions to the TEXT experimental program during the past five years. Contributions include electron temperature information used in the following areas of study: electron cyclotron heating (ECH), pellet injection, and impurity/energy transport. Details of the role which the Auburn ECE system has played will now be discussed

  7. Electron Emission from Ultra-Large Area MOS Electron Emitters

    DEFF Research Database (Denmark)

    Thomsen, Lasse Bjørchmar; Nielsen, Gunver; Vendelbo, Søren Bastholm

    2009-01-01

    Ultralarge metal-oxide-semiconductor (MOS) devices with an active oxide area of 1 cm2 have been fabricated for use as electron emitters. The MOS structures consist of a Si substrate, a SiO2 tunnel barrier (~5 nm), a Ti wetting layer (3–10 Å), and a Au top layer (5–60 nm). Electron emission from...... layer is varied from 3 to 10 Å which changes the emission efficiency by more than one order of magnitude. The apparent mean free path of ~5 eV electrons in Au is found to be 52 Å. Deposition of Cs on the Au film increased the electron emission efficiency to 4.3% at 4 V by lowering the work function....... Electron emission under high pressures (up to 2 bars) of Ar was observed. ©2009 American Vacuum Society...

  8. Monte Carlo simulation of positron induced secondary electrons in thin carbon foils

    International Nuclear Information System (INIS)

    Cai, L H; Yang, B; Ling, C C; Beling, C D; Fung, S

    2011-01-01

    Emission of secondary electrons induced by the passage of low energy positrons through thin carbon foils was studied by the Monte Carlo method. The positron and electron elastic cross sections were calculated by partial wave analysis. The inelastic positron-valence-electron was described by the energy loss function obtained from dielectric theory. The positron-core-electron interaction was modelled by the Gryzinski's excitation function. Positron transport inside the carbon foil was simulated in detail. Secondary electrons created by positrons and high energy secondary electrons through inelastic interactions were tracked through the foil. The positron transmission coefficient and secondary electron yielded in forward and backward geometry are calculated and dependences on positron energy and carbon foil thickness are discussed.

  9. Superthermal electron distribution measurements from polarized electron cyclotron emission

    International Nuclear Information System (INIS)

    Luce, T.C.; Efthimion, P.C.; Fisch, N.J.

    1988-06-01

    Measurements of the superthermal electron distribution can be made by observing the polarized electron cyclotron emission. The emission is viewed along a constant magnetic field surface. This simplifies the resonance condition and gives a direct correlation between emission frequency and kinetic energy of the emitting electron. A transformation technique is formulated which determines the anisotropy of the distribution and number density of superthermals at each energy measured. The steady-state distribution during lower hybrid current drive and examples of the superthermal dynamics as the runaway conditions is varied are presented for discharges in the PLT tokamak. 15 refs., 8 figs

  10. Stimulated secondary emission from semiconductor microcavities

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Mizeikis, V.; Langbein, Wolfgang Werner

    2001-01-01

    We find strong influence of final-state stimulation on the time-resolved light emission dynamics from semiconductor microcavities after pulsed excitation allowing angle-resonant polariton-polariton scattering on the lower-polariton branch. The polariton dynamics can be controlled by injection...

  11. Electron cyclotron emission from thermal plasmas

    International Nuclear Information System (INIS)

    Fidone, I.; Granata, G.

    1978-02-01

    Electron cyclotron radiation from a warm inhomogeneous plasma is investigated. A direct calculation of the emissive power of a plasma slab is performed using Rytov's method and the result is compared with the solution of the transfer equation. It is found that, for arbitrary directions of emission, the two results differ, which reflects the fact that Kirchhoff's law is not generally obeyed

  12. Helium ion beam induced electron emission from insulating silicon nitride films under charging conditions

    Science.gov (United States)

    Petrov, Yu. V.; Anikeva, A. E.; Vyvenko, O. F.

    2018-06-01

    Secondary electron emission from thin silicon nitride films of different thicknesses on silicon excited by helium ions with energies from 15 to 35 keV was investigated in the helium ion microscope. Secondary electron yield measured with Everhart-Thornley detector decreased with the irradiation time because of the charging of insulating films tending to zero or reaching a non-zero value for relatively thick or thin films, respectively. The finiteness of secondary electron yield value, which was found to be proportional to electronic energy losses of the helium ion in silicon substrate, can be explained by the electron emission excited from the substrate by the helium ions. The method of measurement of secondary electron energy distribution from insulators was suggested, and secondary electron energy distribution from silicon nitride was obtained.

  13. The trajectories of secondary electrons in the scanning electron microscope.

    Science.gov (United States)

    Konvalina, Ivo; Müllerová, Ilona

    2006-01-01

    Three-dimensional simulations of the trajectories of secondary electrons (SE) in the scanning electron microscope have been performed for plenty of real configurations of the specimen chamber, including all its basic components. The primary purpose was to evaluate the collection efficiency of the Everhart-Thornley detector of SE and to reveal fundamental rules for tailoring the set-ups in which efficient signal acquisition can be expected. Intuitive realizations about the easiness of attracting the SEs towards the biased front grid of the detector have shown themselves likely as false, and all grounded objects in the chamber have been proven to influence the spatial distribution of the signal-extracting field. The role of the magnetic field penetrating from inside the objective lens is shown to play an ambiguous role regarding possible support for the signal collection.

  14. Oblique electron cyclotron emission for electron distribution studies (invited)

    International Nuclear Information System (INIS)

    Preische, S.; Efthimion, P.C.; Kaye, S.M.

    1997-01-01

    Electron cyclotron emission (ECE) at an oblique angle to the magnetic field provides a means of probing the electron distribution function both in energy and physical space through changes in and constraints on the relativistic electron cyclotron resonance condition. Diagnostics based on this Doppler shifted resonance are able to study a variety of electron distributions through changes in the location of the resonance in physical or energy space accomplished by changes in the viewing angle and frequency, and the magnetic field. For the case of observation across a changing magnetic field, such as across the tokamak midplane, the constraint on the resonance condition for real solutions to the dispersion relation can constrain the physical location of optically thin emission. A new Oblique ECE diagnostic was installed and operated on the PBX-M tokamak for the study of energetic electrons during lower hybrid current drive. It has a view 33 degree with respect to perpendicular in the tokamak midplane, receives second harmonic X-mode emission, and is constrained to receive single pass emission by SiC viewing dumps on the tokamak walls. Spatial localization of optically thin emission from superthermal electrons (50 endash 100 keV) was obtained by observation of emission upshifted from a thermal cyclotron harmonic. The localized measurements of the electron energy distribution and the superthermal density profile made by this diagnostic demonstrate its potential to study the spatial transport of energetic electrons on fast magnetohydrodynamic time scales or anomalous diffusion time scales. Oblique ECE can also be used to study electron distributions that may have a slight deviation from a Maxwellian by localizing the emission in energy space. (Abstract Truncated)

  15. Electron beam brightness with field immersed emission

    International Nuclear Information System (INIS)

    Boyd, J.K.; Neil, V.K.

    1985-01-01

    The beam quality or brightness of an electron beam produced with field immersed emission is studied with two models. First, an envelope formulation is used to determine the scaling of brightness with current, magnetic field and cathode radius, and examine the equilibrium beam radius. Second, the DPC computer code is used to calculate the brightness of two electron beam sources

  16. Photons emission processes in electron scattering

    International Nuclear Information System (INIS)

    Soto Vargas, C.W.

    1996-01-01

    The investigations involving the scattering sections arising in virtual an real photon emission processes of electron and positron scattering by an atomic nucleus, have the need for thorough and complete calculations of the virtual photon spectrum and then introduce the distorted wave formulation, which is mathematically involved an numerically elaborated, but accessible to its use in experimental electron scattering facilities. (author) [es

  17. Emission sources in scanning electron microscopy

    International Nuclear Information System (INIS)

    Malkusch, W.

    1990-01-01

    Since the beginning of the commercial scanning electron microscopy, there are two kinds of emission sources generally used for generation of the electron beam. The first group covers the cathodes heated directly and indirectly (tungsten hair-needle cathodes and lanthanum hexaboride single crystals, LaB 6 cathode). The other group is the field emission cathodes. The advantages of the thermal sources are their low vacuum requirement and their high beam current which is necessary for the application of microanalysis units. Disadvantages are the short life and the low resolution. Advantages of the field emission cathode unambiguously are the possibilities of the very high resolution, especially in the case of low acceleration voltages. Disadvantages are the necessary ultra-high vacuum and the low beam current. An alternative source is the thermally induced ZrO/W field emission cathode which works stably as compared to the cold field emission and does not need periodic flashing for emitter tip cleaning. (orig.) [de

  18. SECONDARY EMISSION FROM NON-SPHERICAL DUST GRAINS WITH ROUGH SURFACES: APPLICATION TO LUNAR DUST

    International Nuclear Information System (INIS)

    Richterová, I.; Němeček, Z.; Beránek, M.; Šafránková, J.; Pavlů, J.

    2012-01-01

    Electrons impinging on a target can release secondary electrons and/or they can be scattered out of the target. It is well established that the number of escaping electrons per primary electron depends on the target composition and dimensions, the energy, and incidence angle of the primary electrons, but there are suggestions that the target's shape and surface roughness also influence the secondary emission. We present a further modification of the model of secondary electron emission from dust grains which is applied to non-spherical grains and grains with defined surface roughness. It is shown that the non-spherical grains give rise to a larger secondary electron yield, whereas the surface roughness leads to a decrease in the yield. Moreover, these effects can be distinguished: the shape effect is prominent for high primary energies, whereas the surface roughness predominantly affects the yield at the low-energy range. The calculations use the Lunar Highlands Type NU-LHT-2M simulant as a grain material and the results are compared with previously published laboratory and in situ measurements.

  19. Study of thin insulating films using secondary ion emission

    International Nuclear Information System (INIS)

    Hilleret, Noel

    1973-01-01

    Secondary ion emission from insulating films was investigated using a CASTAING-SLODZIAN ion analyzer. Various different aspects of the problem were studied: charge flow across a silica film; the mobilization of sodium during ion bombardment; consequences of the introduction of oxygen on the emission of secondary ions from some solids; determination of the various characteristics of secondary ion emission from silica, silicon nitride and silicon. An example of measurements made using this type of operation is presented: profiles (concentration as a function of depth) of boron introduced by diffusion or implantation in thin films of silica on silicon or silicon nitride. Such measurements have applications in microelectronics. The same method of operation was extended to other types of insulating film, and in particular, to the metallurgical study of passivation films formed on the surface of stainless steels. (author) [fr

  20. Fundamental properties of secondary negative ion emission by sputtering

    International Nuclear Information System (INIS)

    Shimizu, Toshiki; Tsuji, Hiroshi; Ishikawa, Junzo

    1989-01-01

    The report describes some results obtained from preliminary experiments on secondary negative ion emission from a cesiated surface by Xe-ion beam sputtering, which give the production probability. A measuring system is constructed for secondary negative ion emission. The system consists of a microwave ion source with a lens, a sputtering target holder with a heater, a cesium oven, a limiting aperture with a substrate for deposition, a negative-ion extractor and lens, and a ExB type mass separator. Observations are made on the dependence of negative ion current on cesium supply, dependence of negative ion current on target temperature, and negative ion production probability. The cesium supply and the target temperature are found to strongly influence the negative ion emission. By controlling these factors, the optimum condition for secondary negative ion emission is achieved with a minimum surface work function. The production probability of the negative ion is found to be very high, about 20% for carbon. Therefore, the secondary negative ion emission is considered a useful and highly efficient method to obtain high current ion beams. The constant in the Rasser's theoretical equation is experimentally determined to be 4.1 x 10 -4 eV sec/m. (N.K.)

  1. Secondary electrons detectors for beam tracking: micromegas and wire chamber

    International Nuclear Information System (INIS)

    Pancin, J; Chaminade, T; Drouart, A; Kebbiri, M; Riallot, M; Fernandez, B; Naqvi, F

    2009-01-01

    SPIRAL2 or FAIR will be able to deliver beams of radioactive isotopes of low energy (less than 10 MeV/n). The emittance of these new beams will impose the use of beam tracking detectors to reconstruct the exact impact position of the nuclei on the experimental target. However, due to their thickness, the classical detectors will generate a lot of energy and angular straggling. A possible alternative is the SED principle (Secondary Electron Detector). It consists of an emissive foil placed in beam and a detector for the secondary electrons ejected by the passing of the nuclei through the foil. An R and D program has been initiated at CEA Saclay to study the possibility to use low pressure gaseous detectors as SED for beam tracking. Some SED have been already used on the VAMOS spectrometer at GANIL since 2004. We have constructed new detectors on this model to measure their performances in time and spatial resolution, and counting rate. Other detector types are also under study. For the first time, a test with different micromegas detectors at 4 Torr has been realized. A comparison on the time resolution has been performed between wire chamber and micromegas at very low pressure. The use of micromegas could be promising to improve the counting rate capability and the robustness of beam tracking detectors.

  2. Process and device of elementary and chemical analysis of a sample through a spectral analysis of the secondary electron energies

    International Nuclear Information System (INIS)

    Le Gressus, Claude; Massignon, Daniel; Sopizet, Rene.

    1975-01-01

    The present invention relates to a method of chemical and elementary analysis of samples through a spectral analysis of secondary electrons (Auger electrons) emitted from said sample under a primary monokinetic electron beam concentrated on its surface. Said method is characterized in that the intensity of the primary monokinetic electron beam emitted from an electron gun is modulated at a frequency ω; and in that the secondary electrons of energy E emitted from the sample are then collected. A reference voltage corresponding to the modulation in intensity of the primary electron beam is applied at the input of a phase sensitive detector together with a voltage proportional to the intensity of the flux of said collected secondary electrons to obtain at the output of said detector a voltage proportional to the number of the secondary electrons of energy E. The secondary emission energy spectrum of the sample is then plotted [fr

  3. Electron injection in diodes with field emission

    International Nuclear Information System (INIS)

    Denavit, J.; Strobel, G.L.

    1986-01-01

    This paper presents self-consistent steady-state solutions of the space charge, transmitted current, and return currents in diodes with electron injection from the cathode and unlimited field emission of electrons and ions from both electrodes. Time-dependent particle simulations of the diode operation confirm the analytical results and show how these steady states are reached. The results are applicable to thermionic diodes and to photodiodes

  4. Field electron emission from branched nanotubes film

    International Nuclear Information System (INIS)

    Zeng Baoqing; Tian Shikai; Yang Zhonghai

    2005-01-01

    We describe the preparation and analyses of films composed of branched carbon nanotubes (CNTs). The CNTs were grown on a Ni catalyst film using chemical vapor deposition from a gas containing acetylene. From scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses, the branched structure of the CNTs was determined; the field emission characteristics in a vacuum chamber indicated a lower turn on field for branched CNTs than normal CNTs

  5. Simultaneous study of sputtering and secondary ion emission of binary Fe-based alloys

    International Nuclear Information System (INIS)

    Riadel, M.M.; Nenadovic, T.; Perovic, B.

    1976-01-01

    The sputtering and secondary ion emission of binary Fe-based alloys of simple phase diagrams have been studied simultaneously. A series FeNi and FeCr alloys in the concentration range of 0-100% have been bombarded by 4 keV Kr + ions in a secondary ion mass spectrometer. The composition of the secondary ions has been analysed and also a fraction of the sputtered material has been collected and analysed by electron microprobe. The surface topography of the etched samples has been studied by scanning electron microscope. The relative sputtering coefficients of the metals have been determined, and the preferential sputtering of the alloying component of lower S have been proved. The etching pictures of samples are in correlation with the sputtering rates. Also the degree of secondary ionization has been calculated from the simultaneously measured ion emission and sputtering data. α + shows the change in the concentration range of the melting point minimum. This fact emphasizes the connection between the physico-chemical properties of alloys and their secondary emission process. From the dependence of the emitted homo- and hetero-cluster ions, conclusions could be shown concerning the production mechanism of small metallic aggregates

  6. Secondary electron ion source neutron generator

    Science.gov (United States)

    Brainard, John P.; McCollister, Daryl R.

    1998-01-01

    A neutron generator employing an electron emitter, an ion source bombarded by the electrons from the electron emitter, a plasma containment zone, and a target situated between the plasma containment zone and the electron emitter. The target contains occluded deuterium, tritium, or a mixture thereof

  7. Disruption generated secondary runaway electrons in present day tokamaks

    International Nuclear Information System (INIS)

    Pankratov, I.M.; Jaspers, R.

    2000-01-01

    An analysis of the runaway electron secondary generation during disruptions in present day tokamaks (JET, JT-60U, TEXTOR) was made. It was shown that even for tokamaks with the plasma current I approx 100 kA the secondary generation may dominate the runaway production during disruptions. In the same time in tokamaks with I approx 1 MA the runaway electron secondary generation during disruptions may be suppressed

  8. Electron field emission for ultrananocrystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Krauss, A. R.; Auciello, O.; Ding, M. Q.; Gruen, D. M.; Huang, Y.; Zhirnov, V. V.; Givargizov, E. I.; Breskin, A.; Chechen, R.; Shefer, E. (and others)

    2001-03-01

    Ultrananocrystalline diamond (UNCD) films 0.1--2.4 {mu}m thick were conformally deposited on sharp single Si microtip emitters, using microwave CH{sub 4}--Ar plasma-enhanced chemical vapor deposition in combination with a dielectrophoretic seeding process. Field-emission studies exhibited stable, extremely high (60--100 {mu}A/tip) emission current, with little variation in threshold fields as a function of film thickness or Si tip radius. The electron emission properties of high aspect ratio Si microtips, coated with diamond using the hot filament chemical vapor deposition (HFCVD) process were found to be very different from those of the UNCD-coated tips. For the HFCVD process, there is a strong dependence of the emission threshold on both the diamond coating thickness and Si tip radius. Quantum photoyield measurements of the UNCD films revealed that these films have an enhanced density of states within the bulk diamond band gap that is correlated with a reduction in the threshold field for electron emission. In addition, scanning tunneling microscopy studies indicate that the emission sites from UNCD films are related to minima or inflection points in the surface topography, and not to surface asperities. These data, in conjunction with tight binding pseudopotential calculations, indicate that grain boundaries play a critical role in the electron emission properties of UNCD films, such that these boundaries: (a) provide a conducting path from the substrate to the diamond--vacuum interface, (b) produce a geometric enhancement in the local electric field via internal structures, rather than surface topography, and (c) produce an enhancement in the local density of states within the bulk diamond band gap.

  9. Collision dynamics probed by convoy electron emission

    International Nuclear Information System (INIS)

    Seliger, M.; Burgdoerfer, J.; Toekesi, K.; Reinhold, C.O.; Takabayashi, Y.; Ito, T.; Komaki, K.; Azuma, T.; Yamazaki, Y.; RIKEN, Saitama

    2002-01-01

    The description of the collision mechanisms was examined by the emission of convoy electrons as a result of the transport of an Ar 17+ ion with an energy of 390 MeV/amu through self-supporting amorphous carbon foils of thickness varying from 25 to 9190 μg/cm 2 . A classical trajectory Monte Carlo (CTMC) simulation of the random walk of the electron initially attached to the relativistic hydrogenic Argon ion was performed. Measurements were made of the final kinetic energy of the emitted convoy electrons at the Heavy Ion Medical Accelerator in Chiba (HIMAC). (R.P.)

  10. An experimental study of electron transfer and emission during particle-surface interactions

    International Nuclear Information System (INIS)

    McGrath, C.T.

    2000-09-01

    A new coincidence technique has been developed and used to study the secondary electron emission that arises during the interaction of ions with surfaces. This coincidence technique allows the secondary electron emission statistics due to the impact of singly, doubly and multiply charged ions on surfaces to be measured in coincidence with reflected particles, in specific charge states and with specific post-collision trajectories. This system has been used to study the impact of 8 keV H + ions on polycrystalline copper and aluminium targets. Under these conditions the potential emission contribution is negligible and the electron emission is almost entirely due to kinetic emission processes. The sub-surface contribution to the observed electron emission has been isolated using two newly developed models. These models provide valuable information about the depth and amount of surface penetration and on the probability for subsequent electron transport to the surface. The impact of 2 - 100 keV Xe q+ (q = 1 - 10) ions on polycrystalline copper has also been studied using this system. From the subsequent data the potential and kinetic contributions to secondary electron emission have been separated using a previously established model for potential emission. The resulting kinetic emission yield increases with increasing ion impact energy, consistent with current concepts on quasimolecular ionisation. For ions impacting at large incident angles evidence for sub-surface emission has also been observed. The degree of penetration increases with ion impact energy, consistent with current concepts on this effect. The formation of H - ions from incident H + ions has also been studied by measuring the secondary electron emission statistics in coincidence with reflected particles in specific final charge states. This preliminary data is consistent with a two-step process of Auger neutralisation followed by resonant electron capture to the affinity level. However this mechanism

  11. Electron emission from molybdenum under ion bombardment

    International Nuclear Information System (INIS)

    Ferron, J.; Alonso, E.V.; Baragiola, R.A.; Oliva-Florio, A.

    1981-01-01

    Measurements are reported of electron emission yields of clean molybdenum surfaces under bombardment with H + , H 2 + , D + , D 2 + , He + , N + , N 2 + , O + , O 2 + , Ne + , Ar + , Kr + and Xe + in the wide energy range 0.7-60.2 keV. The clean surfaces were produced by inert gas sputtering under ultrahigh vacuum. The results are compared with those predicted by a core-level excitation model. The disagreement found when using correct values for the energy levels of Mo is traced to wrong assumptions in the model. A substantially improved agreement with experiment is obtained using a model in which electron emission results from the excitation of valence electrons from the target by the projectiles and fast recoiling target atoms. (author)

  12. Secondary electron/reflected particle coincidence studies during slow highly charged ion-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    McGrath, C.T.; Szilagyi, Z.; Shah, M.B.; McCullough, R.W. [Queen' s Univ., Belfast, Northern Ireland (United Kingdom); Woolsey, J.M. [Stirling Univ. (United Kingdom). DBMS; Trassl, R.; Salzborn, E. [Giessen Univ. (Germany). Inst. fuer Kernphysik

    2001-07-01

    We have measured the secondary electron emission statistics (ES) for 5 keV N{sup q+} (q = 1-4) ions incident at 10 on polycrystalline aluminium, in coincidence with specularly reflected N{sup 0}. In this arrangement the kinetic contribution to secondary electron emission is minimised. The experimental data shows that the coincident electron yield, {gamma}, increases linearly with incident ion charge state. The kinetic emission contribution has also been determined from this data. The ES due to 2 and 4 keV He{sup 2+} impact on polycrystalline aluminium in coincidence with specularly reflected He{sup +} and He{sup 0} have also been determined. The process He{sup 2+} {yields} He{sup 0} yields a larger {gamma} value than the process He{sup 2+} {yields} He{sup +}. (orig.)

  13. Secondary electrons as probe of preequilibrium stopping power of ions penetrating solids

    International Nuclear Information System (INIS)

    Kroneberger, K.; Rothard, H.; Koschar, P.; Lorenzen, P.; Groeneveld, K.O.; Clouvas, A.; Veje, E.; Kemmler, J.

    1990-01-01

    The passage of ions through solid media is accompanied by the emission of low energy secondary electrons. At high ion velocities v p (i.e. v p > 10 7 cm/s) the kinetic emission of electrons as a result of direct Coulomb interaction between the ion and the target electron is the dominant initial production mechanism. The energy lost by the ion and, thus, transferred to the electrons is known as electronic stopping power in the solid. Elastic and inelastic interactions of primary, liberated electrons on their way through the bulk and the surface of the solid modify strongly their original energy and angular distribution and, in particular, leads to the transfer of their energy to further, i.e. secondary electrons (SE), such that the main part of the deposited energy of the ion is eventually over transferred to SE. It is, therefore, suggestive to assume a proportionality between the electronic stopping power S sm-bullet of the ion and the total SE yield g, i.e. the number of electrons ejected per ion. Following Sternglass the authors consider schematically for kinetic SE emission contributions from two extreme cases: (a) SEs produced mostly isotropically with large impact parameter, associated with an escape depth L SE from the solid; (b) SEs produced mostly unisotropically in forward direction with small impact parameter (δ-electrons), associated with a transport length L δ

  14. Field electron emission spectrometer combined with field ion/electron microscope as a field emission laboratory

    International Nuclear Information System (INIS)

    Shkuratov, S.I.; Ivanov, S.N.; Shilimanov, S.N.

    1996-01-01

    The facility, combining the field ion microscope, field electron emission microscope and field electron emission spectrometer, is described. Combination of three methodologies makes it possible to carry out the complete cycle of emission studies. Atom-plane and clean surface of the studied samples is prepared by means of field evaporation of the material atom layers without any thermal and radiation impact. This enables the study of atom and electron structure of clean surface of the wide range materials, the study whereof through the field emission methods was previously rather difficult. The temperature of the samples under study changes from 75 up to 2500 K. The energy resolution of the electron analyzer equals 30 MeV. 19 refs., 10 figs

  15. Simulation study of secondary electron images in scanning ion microscopy

    CERN Document Server

    Ohya, K

    2003-01-01

    The target atomic number, Z sub 2 , dependence of secondary electron yield is simulated by applying a Monte Carlo code for 17 species of metals bombarded by Ga ions and electrons in order to study the contrast difference between scanning ion microscopes (SIM) and scanning electron microscopes (SEM). In addition to the remarkable reversal of the Z sub 2 dependence between the Ga ion and electron bombardment, a fine structure, which is correlated to the density of the conduction band electrons in the metal, is calculated for both. The brightness changes of the secondary electron images in SIM and SEM are simulated using Au and Al surfaces adjacent to each other. The results indicate that the image contrast in SIM is much more sensitive to the material species and is clearer than that for SEM. The origin of the difference between SIM and SEM comes from the difference in the lateral distribution of secondary electrons excited within the escape depth.

  16. Secondary-electron cascade in attosecond photoelectron spectroscopy from metals

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2009-01-01

    an analytical model based on an approximate solution to Boltzmann's transport equation to account for the amount and energy distribution of these secondary electrons. Our theory is in good agreement with the electron spectrum found in a recent attosecond streaking experiment. To suppress the background and gain......Attosecond spectroscopy is currently restricted to photon energies around 100 eV. We show that under these conditions, electron-electron scatterings, as the photoelectrons leave the metal, give rise to a tail of secondary electrons with lower energies and hence a significant background. We develop...

  17. Experiments on secondary ion emission with multicharged keV ion bombardement

    International Nuclear Information System (INIS)

    Della Negra, S.; Depauw, J.; Joret, H.; Le Beyec, Y.; Schweikert, E.A.

    1987-01-01

    An electron cyclotron resonance ion source was used to study the influence of the incident charge state of keV ions on secondary ion emission. The experiments were run with 18 keV Arn+ (1 < n < 11) beams produced by a minimafios source. Various types of targets were bombarded by the ion beam and the sputtered ionized species were identified by time of flight mass spectrometry. The experimental arrangement is detailed and preliminary results are indicated

  18. Electron transport effects in ion induced electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Dubus, A. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium)]. E-mail: adubus@ulb.ac.be; Pauly, N. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium); Roesler, M. [Karl-Pokern-Str. 12, D-12587 Berlin (Germany)

    2007-03-15

    Ion induced electron emission (IIEE) is usually described as a three-step process, i.e. electron excitation by the incident projectile, electron transport (and multiplication) and electron escape through the potential barrier at the surface. In many cases, the first step of the process has been carefully described. The second step of the process, i.e. electron transport and multiplication, has often been treated in a very rough way, a simple decreasing exponential law being sometimes used. It is precisely the aim of the present work to show the importance of a correct description of electron transport and multiplication in a theoretical calculation of IIEE. A short overview of the electron transport models developed for IIEE is given in this work. The so-called 'Infinite medium slowing-down model' often used in recent works is evaluated by means of Monte Carlo simulations. In particular, the importance of considering correctly the semi-infinite character of the medium and the boundary condition at the vacuum-medium interface is discussed. Quantities like the electron escape depth are also briefly discussed. This evaluation has been performed in the particular case of protons (25keV

  19. Rough surface mitigates electron and gas emission

    International Nuclear Information System (INIS)

    Molvik, A.

    2004-01-01

    Heavy-ion beams impinging on surfaces near grazing incidence (to simulate the loss of halo ions) generate copious amounts of electrons and gas that can degrade the beam. We measured emission coefficients of η e (le) 130 and η 0 ∼ 10 4 respectively, with 1 MeV K + incident on stainless steel. Electron emission scales as η e ∝ 1/cos(θ), where θ is the ion angle of incidence relative to normal. If we were to roughen a surface by blasting it with glass beads, then ions that were near grazing incidence (90 o ) on smooth surface would strike the rims of the micro-craters at angles closer to normal incidence. This should reduce the electron emission: the factor of 10 reduction, Fig. 1(a), implies an average angle of incidence of 62 o . Gas desorption varies more slowly with θ (Fig. 1(b)) decreasing a factor of ∼2, and along with the electron emission is independent of the angle of incidence on a rough surface. In a quadrupole magnet, electrons emitted by lost primary ions are trapped near the wall by the magnetic field, but grazing incidence ions can backscatter and strike the wall a second time at an azimuth where magnetic field lines intercept the beam. Then, electrons can exist throughout the beam (see the simulations of Cohen, HIF News 1-2/04). The SRIM (TRIM) Monte Carlo code predicts that 60-70% of 1 MeV K + ions backscatter when incident at 88-89 o from normal on a smooth surface. The scattered ions are mostly within ∼10 o of the initial direction but a few scatter by up to 90 o . Ion scattering decreases rapidly away from grazing incidence, Fig. 1(c ). At 62 deg. the predicted ion backscattering (from a rough surface) is 3%, down a factor of 20 from the peak, which should significantly reduce electrons in the beam from lost halo ions. These results are published in Phys. Rev. ST - Accelerators and Beams

  20. Magnetic insulation of secondary electrons in plasma source ion implantation

    International Nuclear Information System (INIS)

    Rej, D.J.; Wood, B.P.; Faehl, R.J.; Fleischmann, H.H.

    1993-01-01

    The uncontrolled loss of accelerated secondary electrons in plasma source ion implantation (PSII) can significantly reduce system efficiency and poses a potential x-ray hazard. This loss might be reduced by a magnetic field applied near the workpiece. The concept of magnetically-insulated PSII is proposed, in which secondary electrons are trapped to form a virtual cathode layer near the workpiece surface where the local electric field is essentially eliminated. Subsequent electrons that are emitted can then be reabsorbed by the workpiece. Estimates of anomalous electron transport from microinstabilities are made. Insight into the process is gained with multi-dimensional particle-in-cell simulations

  1. Electron Cyclotron Maser Emissions from Evolving Fast Electron Beams

    Science.gov (United States)

    Tang, J. F.; Wu, D. J.; Chen, L.; Zhao, G. Q.; Tan, C. M.

    2016-05-01

    Fast electron beams (FEBs) are common products of solar active phenomena. Solar radio bursts are an important diagnostic tool for understanding FEBs and the solar plasma environment in which they propagate along solar magnetic fields. In particular, the evolution of the energy spectrum and velocity distribution of FEBs due to the interaction with the ambient plasma and field during propagation can significantly influence the efficiency and properties of their emissions. In this paper, we discuss the possible evolution of the energy spectrum and velocity distribution of FEBs due to energy loss processes and the pitch-angle effect caused by magnetic field inhomogeneity, and we analyze the effects of the evolution on electron-cyclotron maser (ECM) emission, which is one of the most important mechanisms for producing solar radio bursts by FEBs. Our results show that the growth rates all decrease with the energy loss factor Q, but increase with the magnetic mirror ratio σ as well as with the steepness index δ. Moreover, the evolution of FEBs can also significantly influence the fastest growing mode and the fastest growing phase angle. This leads to the change of the polarization sense of the ECM emission. In particular, our results also reveal that an FEB that undergoes different evolution processes will generate different types of ECM emission. We believe the present results to be very helpful for a more comprehensive understanding of the dynamic spectra of solar radio bursts.

  2. ELECTRON CYCLOTRON MASER EMISSIONS FROM EVOLVING FAST ELECTRON BEAMS

    International Nuclear Information System (INIS)

    Tang, J. F.; Wu, D. J.; Chen, L.; Zhao, G. Q.; Tan, C. M.

    2016-01-01

    Fast electron beams (FEBs) are common products of solar active phenomena. Solar radio bursts are an important diagnostic tool for understanding FEBs and the solar plasma environment in which they propagate along solar magnetic fields. In particular, the evolution of the energy spectrum and velocity distribution of FEBs due to the interaction with the ambient plasma and field during propagation can significantly influence the efficiency and properties of their emissions. In this paper, we discuss the possible evolution of the energy spectrum and velocity distribution of FEBs due to energy loss processes and the pitch-angle effect caused by magnetic field inhomogeneity, and we analyze the effects of the evolution on electron-cyclotron maser (ECM) emission, which is one of the most important mechanisms for producing solar radio bursts by FEBs. Our results show that the growth rates all decrease with the energy loss factor Q , but increase with the magnetic mirror ratio σ as well as with the steepness index δ . Moreover, the evolution of FEBs can also significantly influence the fastest growing mode and the fastest growing phase angle. This leads to the change of the polarization sense of the ECM emission. In particular, our results also reveal that an FEB that undergoes different evolution processes will generate different types of ECM emission. We believe the present results to be very helpful for a more comprehensive understanding of the dynamic spectra of solar radio bursts.

  3. Ferroelectric Electron Emission Principles and Technology

    CERN Document Server

    Riege, H

    1997-01-01

    The spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a non-ferroelectric state or vice versa. If spontaneous polarization changes are induced with fast heat, mechanical pressure, laser or electric field pulses on a submicrosecond time scale, strong uncompensated surface charge densities and related polarization fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric sample. Hence, electron guns can be built with extraction-field-free ferroelectric cathodes, which may be easily separated from the high-field regions of post-accelerating gap structures. The intensity, the energy, the temporal and spatial distribution, and the repetitition rate of the emitted electron beams can be controlled within wide limits via the excitation pulses and external focusing and accelerating electromagnetic fields. The technological advantages an...

  4. Effect of Weakly Nonthermal Ion Velocity Distribution on Jeans Instability in a Complex Plasma in Presence of Secondary Electrons

    International Nuclear Information System (INIS)

    Sarkar, S.; Maity, S.

    2013-01-01

    In this paper we have investigated the effect of weak nonthermality of ion velocity distribution on Jean’s instability in a complex plasma in presence of secondary electrons and negatively charged dust grains. The primary and secondary electron temperatures are assumed equal. Thus plasma under consideration consists of three components: Boltzman distributed electrons, non-thermal ions and negatively charged inertial dust grains. From the linear dispersion relation we have calculated the real frequency and growth rate of the Jean’s mode. Numerically we have found that secondary electron emission destabilizes Jean’s mode when ion nonthermality is weak. (author)

  5. TFTR vertically viewing electron cyclotron emission diagnostic

    International Nuclear Information System (INIS)

    Taylor, G.

    1990-01-01

    The Tokamak Fusion Test Reactor (TFTR) Michelson interferometer has a spectral coverage of 75--540 GHz, allowing measurement of the first four electron cyclotron harmonics. Until recently the instrument has been configured to view the TFTR plasma on the horizontal midplane, primarily in order to measure the electron temperature profile. Electron cyclotron emission (ECE) extraordinary mode spectra from TFTR Supershot plasmas exhibit a pronounced, spectrally narrow feature below the second harmonic. A similar feature is seen with the ECE radiometer diagnostic below the electron cyclotron fundamental frequency in the ordinary mode. Analysis of the ECE spectra indicates the possibility of a non-Maxwellian 40--80 keV tail on the electron distribution in or near the core. During 1990 three vertical views with silicon carbide viewing targets will be installed to provide a direct measurement of the electron energy distribution at major radii of 2.54, 2.78, and 3.09 m with an energy resolution of approximately 20% at 100 keV. To provide the maximum flexibility, the optical components for the vertical views will be remotely controlled to allow the Michelson interferometer to be reconfigured to either the midplane horizontal view or one of the three vertical views between plasma shots

  6. The practical model of electron emission in the radioisotope battery by fast ions

    International Nuclear Information System (INIS)

    Erokhine, N.S.; Balebanov, V.M.

    2003-01-01

    Under the theoretical analysis of secondary-emission radioisotope source of current the estimate of energy spectrum F(E) of secondary electrons with energy E emitted from films is the important problem. This characteristic knowledge allows, in particular, studying the volt-ampere function, the dependence of electric power deposited in the load on the system parameters and so on. Since the rigorous calculations of energy spectrum F(E) are the complicated enough and labour-intensive there is necessity to elaborate the practical model which allows by the simple computer routine on the basis of generalized data (both experimental measurements and theoretical calculations) on the stopping powers and mean free path of suprathermal electrons to perform reliable express-estimates of the energy spectrum F(E) and the volt-ampere function I(V) for the concrete materials of battery emitter films. This paper devoted to description of of the practical model to calculate electron emission characteristics under the passage of fast ion fluxes from the radioisotope source through the battery emitter. The analytical approximations for the stopping power of emitter materials, the electron inelastic mean free path, the ion production of fast electrons and the probability for them to arrive the film surface are taken into account. In the cases of copper and gold films, the secondary electron escaping depth, the position of energy spectrum peak are considered in the dependence on surface potential barrier magnitude U. According to our calculations the energy spectrum peak shifted to higher electron energy under the U growth. The model described may be used for express estimates and computer simulations of fast alpha-particles and suprathermal electrons interactions with the solid state plasma of battery emitter films, to study the electron emission layer characteristics including the secondary electron escaping depth, to find the optimum conditions for excitation of nonequilibrium

  7. Spontaneous and stimulated emission induced by an electron, electron bunch, and electron beam in a plasma

    International Nuclear Information System (INIS)

    Kuzelev, M V; Rukhadze, A A

    2008-01-01

    Two fundamental mechanisms - the Cherenkov effect and anomalous Doppler effect - underlying the emission by an electron during its superluminal motion in medium are considered. Cherenkov emission induced by a single electron and a small electron bunch is spontaneous. In the course of spontaneous Cherenkov emission, the translational motion of an electron is slowed down and the radiation energy grows linearly with time. As the number of radiating electrons increases, Cherenkov emission becomes stimulated. Stimulated Cherenkov emission represents a resonance beam instability. This emission process is accompanied by longitudinal electron bunching in the beam or by the breaking of an electron bunch into smaller bunches, in which case the radiation energy grows exponentially with time. In terms of the longitudinal size L e of the electron bunch there is a transition region λ e 0 -1 between the spontaneous and stimulated Cherenkov effects, where λ is the average radiation wavelength, and δ 0 is the dimensionless (in units of the radiation frequency) growth rate of the Cherenkov beam instability. The range to the left of this region is dominated by spontaneous emission, whereas the range to the right of this region is dominated by stimulated emission. In contrast to the Vavilov-Cherenkov effect, the anomalous Doppler effect should always (even for a single electron) be considered as stimulated, because it can only be explained by accounting for the reverse action of the radiation field on the moving electron. During stimulated emission in conditions where anomalous Doppler effect shows itself, an electron is slowed down and spins up; in this case, the radiation energy grows exponentially with time. (reviews of topical problems)

  8. Engineered Surfaces to Control Secondary Electron Yield for Multipactor Suppression

    Science.gov (United States)

    2017-09-14

    Air Force Institute of Technology AFIT Scholar Theses and Dissertations 9-14-2017 Engineered Surfaces to Control Secondary Electron Yield for...Multipactor Suppression James M. Sattler Follow this and additional works at: https://scholar.afit.edu/etd Part of the Electrical and Electronics Commons... TECHNOLOGY Wright-Patterson Air Force Base, Ohio DISTRIBUTION STATEMENT A. APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

  9. Application of secondary ion emission to impurity control in tokamaks

    International Nuclear Information System (INIS)

    Krauss, A.R.; Gruen, D.M.

    1979-01-01

    The extent to which high Z impurities enter the plasma of a magnetic confinement fusion device depends on the kinetic energy, angle of emission, and very importantly, the charge state of the ejected material. We have been studying both the fundamental process of secondary ion emission and possible techniques for producing surfaces which give rise to high ion fractions during sputtering, with a view to assessing the potential of this approach to impurity control in tokamaks. By carefully choosing materials exposed to fusion plasmas and by properly modifying the surface it may be possible to insure that nearly all the impurities are ejected as ions. As long as certain gas blanket configurations are avoided and especially if a divertor is used, it should then be possible to remove the impurities before they reach the plasma. The relative merits of a variety of materials are considered with regard to this application

  10. Transport of secondary electrons and reactive species in ion tracks

    Science.gov (United States)

    Surdutovich, Eugene; Solov'yov, Andrey V.

    2015-08-01

    The transport of reactive species brought about by ions traversing tissue-like medium is analysed analytically. Secondary electrons ejected by ions are capable of ionizing other molecules; the transport of these generations of electrons is studied using the random walk approximation until these electrons remain ballistic. Then, the distribution of solvated electrons produced as a result of interaction of low-energy electrons with water molecules is obtained. The radial distribution of energy loss by ions and secondary electrons to the medium yields the initial radial dose distribution, which can be used as initial conditions for the predicted shock waves. The formation, diffusion, and chemical evolution of hydroxyl radicals in liquid water are studied as well. COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy.

  11. On the spectrum of the secondary auroral electrons

    International Nuclear Information System (INIS)

    Fung, S.F.; Hoffman, R.A.

    1988-01-01

    We present the results from a statistical study of the spectral characteristics of the (power law portion) secondary electrons associated with inverted-V electron precipitation events. A total of 106 inverted-V events observed at low altitudes ( - /sup γ/ with an averaged γ = 1.85. This spectral parameter is relatively insensitive to the variation of locations of the inverted-V events, but it depends on the primary beam parameters. We compare our results with the predictions and assess the applicabilities of the current theories on the generation of the low-energy auroral power law secondary electrons. Our analysis shows that collisional processes are the dominant source of the secondary electrons. copyright American Geophysical Union 1988

  12. Electron emission during multicharged ion-metal surface interactions

    International Nuclear Information System (INIS)

    Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Hughes, I.G.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M.; Meyer, F.W.

    1992-01-01

    The electron emission during multicharged ion-metal surface interactions will be discussed. The interactions lead to the emission of a significant number of electrons. Most of these electrons have energies below 30 eV. For incident ions with innershell vacancies the emission of Auger electrons that fill these vacancies has been found to occur mainly below the surface. We will present recently measured electron energy distributions which will be used to discuss the mechanisms that lead to the emission of Auger and of low-energy electrons

  13. Correlation of CVD Diamond Electron Emission with Film Properties

    Science.gov (United States)

    Bozeman, S. P.; Baumann, P. K.; Ward, B. L.; Nemanich, R. J.; Dreifus, D. L.

    1996-03-01

    Electron field emission from metals is affected by surface morphology and the properties of any dielectric coating. Recent results have demonstrated low field electron emission from p-type diamond, and photoemission measurements have identified surface treatments that result in a negative electron affinity (NEA). In this study, the field emission from diamond is correlated with surface treatment, surface roughness, and film properties (doping and defects). Electron emission measurements are reported on diamond films synthesized by plasma CVD. Ultraviolet photoemission spectroscopy indicates that the CVD films exhibit a NEA after exposure to hydrogen plasma. Field emission current-voltage measurements indicate "threshold voltages" ranging from approximately 20 to 100 V/micron.

  14. Electron emission from individual indium arsenide semiconductor nanowires

    NARCIS (Netherlands)

    Heeres, E.C.; Bakkers, E.P.A.M.; Roest, A.L.; Kaiser, M.A.; Oosterkamp, T.H.; Jonge, de N.

    2007-01-01

    A procedure was developed to mount individual semiconductor indium arsenide nanowires onto tungsten support tips to serve as electron field-emission sources. The electron emission properties of the single nanowires were precisely determined by measuring the emission pattern, current-voltage curve,

  15. Predamage threshold electron emission from insulator and semiconductor surfaces

    International Nuclear Information System (INIS)

    Siekhaus, W.J.; Kinney, J.H.; Milam, D.

    1985-01-01

    Predamage electron emission shows a dependence on fluence, bandgap and wavelength consistent with multiphoton excitation across the bandgap and inconsistent with avalanche ionization and thermionic emission models. The electron emission scales with pulselength as 1/√T. 6 references, 8 figures, 1 table

  16. Secondary electron measurement and XPS characterization of NEG coatings

    International Nuclear Information System (INIS)

    Sharma, R. K.; Sinha, Atul K.; Gupta, Nidhi; Nuwad, J.; Jagannath,; Gadkari, S. C.; Singh, M. R.; Gupta, S. K.

    2014-01-01

    Ternary alloy coatings of IVB and VB materials provide many of benefits over traditional material surfaces such as creation of extreme high vacuum(XHV), lower secondary electron yield(SEY), low photon desorption coefficient. XHV (pressure −10 mbar) is very useful to the study of surfaces of the material in as it is form, high energy particle accelerators(LHC, Photon Factories), synchrotrons (ESRF, Ellectra) etc.. Low secondary electron yield leads to very low multi-pacting utilizes to increase beam life time. In this paper preparation of the coatings and a study of secondary electron yield measurement after heating at different temperatures has been shown also results of their surface characterization based on shift in binding energy has been produced using the surface techniques XPS. Stoichiometry of the film was measured by Energy dispersive x-ray analysis (EDX)

  17. Electron cyclotron emission spectroscopy on thermonuclear plasmas

    International Nuclear Information System (INIS)

    Tubbing, B.J.D.

    1987-01-01

    Analysis of electron cyclotron emission (ECE) enables one to infer the radial profile of the electron temperature in tokamaks. The Dutch FOM institute for plasma physics has designed, built, installed and operated a grating polychromator for ECE measurements at JET. This thesis deals with a few instrumental aspects of this project and with applications of ECE measurements in tokamak physics studies. Ch. 3 and 4 deal with the wave transport in ECE systems. In Ch. 3 a method is developed to infer the mode conversion, which is a source for transmission losses, in a waveguide component from the antenna pattern of its exit aperture. In Ch. 4 the design and manufacture of the waveguide transition system to the grating polychromator are described. In Ch. 5 a method is reported for calibration of the spectrometers, based on the use of a microwave source which simulates a large area blackbody of very high temperature. The feasibility of the method is tested by applying it to two different ECE systems. In Ch. 6 a study of heat pulse propagation in tokamak plasma's, based on measurement of the electron temperature with the grating polychromator, is presented. 105 refs.; 48 figs.; 8 tabs

  18. Structure of the spin polarization spectrum of secondary electrons emitted from nickel

    International Nuclear Information System (INIS)

    Helman, J.S.

    1985-01-01

    The main features of the structure observed in the energy resolved spin polarization of secondary electrons emitted from Ni are interpreted in terms of surface and bulk plasmon assisted emission. The model also predicts a measureable shift of the main polarization peak of about 0.3 eV to lower energies as the temperature is raised from room temperature to closely below the Curie temperature. (Author) [pt

  19. Secondary emission from a CuBe target due to bombardment with parent and fragment ions of ammonia and phosphine

    International Nuclear Information System (INIS)

    Maerk, T.D.

    1977-01-01

    The secondary electron emission of the first dynode of a CuBe alloy sixteen dynode electron multiplier has been studied in the course of electron impact ionization studies of ammonia and phosphine. Relative secondary electron emission coefficients have been obtained for the singly and doubly charged parent and fragment ions of ammonia, ammonia-d 3 , phosphine and phosphine-d 3 for kinetic energies of 5,25 and 10,5 keV. It has been found, that in general deuterated ions have smaller γ coefficients, that ammonia ions have larger γ coefficients than corresponding phosphine ions, and that the γ coefficients increase with the complexity of the ion under study. (Auth.)

  20. Measurement of secondary emissions during laser cutting of steel equipments

    Energy Technology Data Exchange (ETDEWEB)

    Pilot, Guy [Institut de Radioprotection et de Surete Nucleaire, BP 68, 91192 Gif-sur-Yvette Cedex (France)], E-mail: guy.pilot@irsn.fr; Fauvel, Sylvain [Institut de Radioprotection et de Surete Nucleaire, BP 68, 91192 Gif-sur-Yvette Cedex (France); Gosse, Xavier [AREVA NC, Centre de Marcoule, 30200 Bagnols-sur-Ceze Cedex (France); Dinechin, Guillaume de [Commissariat a l' Energie Atomique, DEN/DM2S/SEMT, Saclay, Bat. 611, 91191 Gif-sur-Yvette Cedex (France); Vernhet, Didier [Commissariat a l' Energie Atomique, DEN/VRH/UMODD, Centre de Valrho, BP 17171, 20207 Bagnols-sur-Ceze Cedex (France)

    2008-08-15

    In order to dismantle some equipments of an obsolete reprocessing plant in Marcoule, studies were carried out by IRSN (Institut de Radioprotection et de Surete Nucleaire)/DSU/SERAC in cooperation with CEA (power laser group) on the laser cutting of steel structures, on the request of AREVA NC/Marcoule (UP1 dismantling project manager) and CEA/UMODD (UP1 dismantling owner). These studies were aimed at: {center_dot}quantifying and characterizing the secondary emissions produced by Nd-YAG laser cutting of Uranus 65 steel pieces and examining the influence of different parameters, {center_dot}qualifying a prefiltration technique and particularly an electrostatic precipitator, {center_dot}comparing the Nd-YAG laser used with other cutting tools previously studied especially on aerosol production and aerosol size distribution.

  1. Modeling Secondary Organic Aerosol Formation From Emissions of Combustion Sources

    Science.gov (United States)

    Jathar, Shantanu Hemant

    Atmospheric aerosols exert a large influence on the Earth's climate and cause adverse public health effects, reduced visibility and material degradation. Secondary organic aerosol (SOA), defined as the aerosol mass arising from the oxidation products of gas-phase organic species, accounts for a significant fraction of the submicron atmospheric aerosol mass. Yet, there are large uncertainties surrounding the sources, atmospheric evolution and properties of SOA. This thesis combines laboratory experiments, extensive data analysis and global modeling to investigate the contribution of semi-volatile and intermediate volatility organic compounds (SVOC and IVOC) from combustion sources to SOA formation. The goals are to quantify the contribution of these emissions to ambient PM and to evaluate and improve models to simulate its formation. To create a database for model development and evaluation, a series of smog chamber experiments were conducted on evaporated fuel, which served as surrogates for real-world combustion emissions. Diesel formed the most SOA followed by conventional jet fuel / jet fuel derived from natural gas, gasoline and jet fuel derived from coal. The variability in SOA formation from actual combustion emissions can be partially explained by the composition of the fuel. Several models were developed and tested along with existing models using SOA data from smog chamber experiments conducted using evaporated fuel (this work, gasoline, fischertropschs, jet fuel, diesels) and published data on dilute combustion emissions (aircraft, on- and off-road gasoline, on- and off-road diesel, wood burning, biomass burning). For all of the SOA data, existing models under-predicted SOA formation if SVOC/IVOC were not included. For the evaporated fuel experiments, when SVOC/IVOC were included predictions using the existing SOA model were brought to within a factor of two of measurements with minor adjustments to model parameterizations. Further, a volatility

  2. Field Emission Scanning Electron Microscope (FESEM) Facility in BTI

    International Nuclear Information System (INIS)

    Cik Rohaida Che Hak; Foo, C.T.; Nor Azillah Fatimah Othman

    2015-01-01

    Field Emission Scanning Electron Microscope (FE-SEM) provides ultra-high resolution imaging at low accelerating voltages and small working distances. The GeminisSEM 500, a new FESEM imaging facility will be installed soon in MTEC, BTI. It provides resolution of the images is as low as 0.6 nm at 15 kV and 1.2 nm at 1 kV, allowing examination of the top surface of nano powders, nano film and nano fiber in the wide range of applications such as mineralogy, ceramics, polymer, metallurgy, electronic devices, chemistry, physics and life sciences. This system is equipped with several detectors to detect various signals such as secondary electrons (SE) detector for topographic information and back-scattered electrons (BSE) detector for materials composition contrast. Energy dispersive x-ray spectroscopy (EDS) with detector energy resolution of < 129 eV and detection limit in the range of 1000-3000 ppm coupled with FE-SEM is used to determine the chemical composition of micro-features including boron (B) to uranium (U). Wavelength dispersive x-ray spectroscopy (WDS) which has detector resolution of 2-20 eV and detection limit of 30-300 ppm coupled with FE-SEM is used to detect elements that cannot be resolved with EDS. The ultra-high resolution imaging combined with the high sensitivity WDS helps to resolve the thorium and rare earth elemental analysis. (author)

  3. Secondary emission yield at low-primary energies of magnetic materials for anti-multipactor applications

    CERN Document Server

    Aguilera, L; Olano, L; Casas, A; Morales, P; Vázquez, M; Galán, L; Caspers, F; Costa-Pinto, P; Taborelli, M; Raboso, D

    2014-01-01

    Secondary electron emission processes under electron bombardment are central to many effects at surfaces and interfaces, and to many in vacuum high power RF electronic devices where multipactor can be very intense [1,2]. Ferrite materials are usually used in microwave components used in space telecommunication systems, as circulators, phase-shifters, switches, and isolators. The physics of the multipactor phenomenon existing in microwave devices based on ferrite materials is an important issue and it is urgent to be researched [3]. One difficulty in the analysis of the multipactor effect in RF components containing ferrite lies on the fact that this material is an anysotropic magnetic medium controlled by an applied permanent magnetic field, which is used to magnetize the ferrite material. SEY and other properties (structure, magnetic behaviour,...) of soft-magnetic materials were studied in this work. MnZn soft ferrites magnets are suitable in the situation of frequency < 3MHz, low loss and high μi. Comp...

  4. Detection of secondary electrons with pixelated hybrid semiconductor detectors

    International Nuclear Information System (INIS)

    Gebert, Ulrike Sonja

    2011-01-01

    Within the scope of this thesis, secondary electrons were detected with a pixelated semiconductor detector named Timepix. The Timepix detector consists of electronics and a sensor made from a semiconductor material. The connection of sensor and electronics is done for each pixel individually using bump bonds. Electrons with energies above 3 keV can be detected with the sensor. One electron produces a certain amount of electron-hole pairs according to its energy. The charge then drifts along an electric field to the pixel electronics, where it induces an electric signal. Even without a sensor it is possible to detect an electric signal from approximately 1000 electrons directly in the pixel electronics. Two different detector systems to detect secondary electrons using the Timepix detector were investigated during this thesis. First of all, a hybrid photon detector (HPD) was used to detect single photoelectrons. The HPD consists of a vacuum vessel with an entrance window and a cesium iodine photocathode at the inner surface of the window. Photoelectrons are released from the photocathode by incident light and are accelerated in an electric field towards the Timepix detector, where the point of interaction and the arrival time of the electron is determined. With a proximity focusing setup, a time resolution of 12 ns (with an acceleration voltage of 20 kV between photocathode and Timepix detector) was obtained. The HPD examined in this thesis showed a strong dependence of the dark rate form the acceleration voltage and the pressure in the vacuum vessel. At a pressure of few 10 -5 mbar and an acceleration voltage of 20 kV, the dark rate was about 800 Hz per mm 2 area of the read out photocathode. One possibility to reduce the dark rate is to identify ion feedback events. With a slightly modified setup it was possible to reduce the dark rate to 0.5 Hz/mm 2 . To achieve this, a new photocathode was mounted in a shorter distance to the detector. The measurements where

  5. Determination of the secondary electron equilibrium using an extrapolation chamber

    International Nuclear Information System (INIS)

    Marshall, E.T.; Vaziri, K.; Krueger, F.P.; Cossairt, J.D.

    1996-09-01

    To ensure that the external personnel dosimetry program conducted by U. S. Department of Energy (DOE) contractors is of the highest quality, the DOE established the Department of Energy Laboratory Accreditation Program or DOELAP. The contractor's dosimetry program is assessed against the criteria set forth for dosimeter performance and the associated quality assurance and calibration programs. Although personnel dosimeters are not processed or calibrated by Fermilab, a proactive quality assurance program is in place to ensure accurate monitoring. This program includes quarterly blind testing of the dosimeters used by personnel. During the on-site assessment conducted of Fermilab's external dosimetry program during May 1994, an observation with regard to equipment maintenance and calibration was made: ''calibration personnel should probably review the electron secondary equilibrium needs at various irradiation distances from the 137 Cs irradiation systems'' The majority of the secondary electrons are generated through interactions of the beam with the collimator. Secondary electrons increase the low energy component of the radiation field, increasing the shallow doses measured. For dosimetric purposes, this increase needs to be defined so appropriate corrections to calculations or modifications to the facility can be made. Prompted by this observation, a study was designed to investigate the electron secondary equilibrium in the facility used for the blind testing by determining the dose equivalent as a function of depth in a tissue-equivalent medium. This presentation summarizes the methodology utilized and results of the investigation

  6. Electron emission from solids induced by swift heavy ions

    International Nuclear Information System (INIS)

    Xiao Guoqing

    2000-01-01

    The recent progresses in experimental and theoretical studies of the collision between swift heavy ion and solids as well as electron emission induced by swift heavy ion in solids were briefly reviewed. Three models, Coulomb explosion, thermal spike and repulsive long-lived states, for interpreting the atomic displacements stimulated by the electronic energy loss were discussed. The experimental setup and methods for measuring the electron emission from solids were described. The signification deviation from a proportionality between total electron emission yields and electronic stopping power was found. Auger-electron and convoy-electron spectra are thought to be a probe for investigating the microscopic production mechanisms of the electronic irradiation-damage. Electron temperature and track potential at the center of nuclear tracks in C and polypropylene foils induced by 5 MeV/u heavy ions, which are related to the electronic excitation density in metals and insulators respectively, were extracted by measuring the high resolution electron spectra

  7. Observations of localised dielectric excitations, secondary events and ionisation damage by scanning transmission electron microscopy

    International Nuclear Information System (INIS)

    Howie, A.

    1988-01-01

    In the scanning transmission electron microscope (STEM) a high intensity /approximately/0.5nm diameter, probe of 100 keV electrons is formed. This can be positioned to collect energy loss spectra from surfaces, interfaces, small spheres or other particles at controlled values of impact parameter or can be scanned across the object (usually a thin film) to produce high resolution images formed from a variety of signals - small angle or large angle (Z contrast) elastic scattering, inelastic scattering (both valence and core losses), secondary electron emission and x-ray or optical photon emission. The high spatial resolution achievable in a variety of simple structures raises many unsolved theoretical problems concerning the generation, propagation and decay of excitations in inhomogeneous media. These range from quite well posed problems in the mathematical physics of dielectric excitation to problems of plasmon propagation and rather more exotic and less well understood problems of radiation damage. 15 refs., 4 figs

  8. Ultrafast Plasmonic Electron Emission from Ag Nanolayers with Different Roughness

    Czech Academy of Sciences Publication Activity Database

    Márton, I.; Ayadi, V.; Rácz, P.; Stefaniuk, T.; Wróbel, Piotr; Földi, P.; Dombi, P.

    2016-01-01

    Roč. 11, č. 3 (2016), s. 811-816 ISSN 1557-1955 Institutional support: RVO:67985882 Keywords : Nanoparticles * Ultrafast phenomena * Electron emission Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.139, year: 2016

  9. Secondary Electrons as an Energy Source for Life.

    Science.gov (United States)

    Stelmach, Kamil B; Neveu, Marc; Vick-Majors, Trista J; Mickol, Rebecca L; Chou, Luoth; Webster, Kevin D; Tilley, Matt; Zacchei, Federica; Escudero, Cristina; Flores Martinez, Claudio L; Labrado, Amanda; Fernández, Enrique J G

    2018-01-01

    Life on Earth is found in a wide range of environments as long as the basic requirements of a liquid solvent, a nutrient source, and free energy are met. Previous hypotheses have speculated how extraterrestrial microbial life may function, among them that particle radiation might power living cells indirectly through radiolytic products. On Earth, so-called electrophilic organisms can harness electron flow from an extracellular cathode to build biomolecules. Here, we describe two hypothetical mechanisms, termed "direct electrophy" and "indirect electrophy" or "fluorosynthesis," by which organisms could harness extracellular free electrons to synthesize organic matter, thus expanding the ensemble of potential habitats in which extraterrestrial organisms might be found in the Solar System and beyond. The first mechanism involves the direct flow of secondary electrons from particle radiation to a microbial cell to power the organism. The second involves the indirect utilization of impinging secondary electrons and a fluorescing molecule, either biotic or abiotic in origin, to drive photosynthesis. Both mechanisms involve the attenuation of an incoming particle's energy to create low-energy secondary electrons. The validity of the hypotheses is assessed through simple calculations showing the biomass density attainable from the energy supplied. Also discussed are potential survival strategies that could be used by organisms living in possible habitats with a plentiful supply of secondary electrons, such as near the surface of an icy moon. While we acknowledge that the only definitive test for the hypothesis is to collect specimens, we also describe experiments or terrestrial observations that could support or nullify the hypotheses. Key Words: Radiation-Electrophiles-Subsurface life. Astrobiology 18, 73-85.

  10. Secondary Electrons as an Energy Source for Life

    Science.gov (United States)

    Stelmach, Kamil B.; Neveu, Marc; Vick-Majors, Trista J.; Mickol, Rebecca L.; Chou, Luoth; Webster, Kevin D.; Tilley, Matt; Zacchei, Federica; Escudero, Cristina; Flores Martinez, Claudio L.; Labrado, Amanda; Fernández, Enrique J. G.

    2018-01-01

    Life on Earth is found in a wide range of environments as long as the basic requirements of a liquid solvent, a nutrient source, and free energy are met. Previous hypotheses have speculated how extraterrestrial microbial life may function, among them that particle radiation might power living cells indirectly through radiolytic products. On Earth, so-called electrophilic organisms can harness electron flow from an extracellular cathode to build biomolecules. Here, we describe two hypothetical mechanisms, termed "direct electrophy" and "indirect electrophy" or "fluorosynthesis," by which organisms could harness extracellular free electrons to synthesize organic matter, thus expanding the ensemble of potential habitats in which extraterrestrial organisms might be found in the Solar System and beyond. The first mechanism involves the direct flow of secondary electrons from particle radiation to a microbial cell to power the organism. The second involves the indirect utilization of impinging secondary electrons and a fluorescing molecule, either biotic or abiotic in origin, to drive photosynthesis. Both mechanisms involve the attenuation of an incoming particle's energy to create low-energy secondary electrons. The validity of the hypotheses is assessed through simple calculations showing the biomass density attainable from the energy supplied. Also discussed are potential survival strategies that could be used by organisms living in possible habitats with a plentiful supply of secondary electrons, such as near the surface of an icy moon. While we acknowledge that the only definitive test for the hypothesis is to collect specimens, we also describe experiments or terrestrial observations that could support or nullify the hypotheses.

  11. EVIDENCE FOR SECONDARY EMISSION AS THE ORIGIN OF HARD SPECTRA IN TeV BLAZARS

    International Nuclear Information System (INIS)

    Zheng, Y. G.; Kang, T.

    2013-01-01

    We develop a model for the possible origin of hard, very high energy (VHE) spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside it contribute to the observed high-energy γ-ray emission. That is, the primary photons are produced through the synchrotron self-Compton process, and the secondary photons are produced through high-energy proton interactions with background photons along the line of sight. We apply the model to a characteristic case of VHE γ-ray emission in the distant blazar 1ES 1101-232. Assuming suitable electron and proton spectra, we obtain excellent fits to the observed spectra of this blazar. This indicated that the surprisingly low attenuation of the high-energy γ-rays, especially the shape of the VHE γ-ray tail of the observed spectra, can be explained by secondary γ-rays produced in interactions of cosmic-ray protons with background photons in intergalactic space.

  12. Secondary organic aerosol formation from road vehicle emissions

    Science.gov (United States)

    Pieber, Simone M.; Platt, Stephen M.; El Haddad, Imad; Zardini, Alessandro A.; Suarez-Bertoa, Ricardo; Slowik, Jay G.; Huang, Ru-Jin; Hellebust, Stig; Temime-Roussel, Brice; Marchand, Nicolas; Drinovec, Luca; Mocnik, Grisa; Baltensperger, Urs; Astorga, Covadogna; Prévôt, André S. H.

    2014-05-01

    Organic aerosol particles (OA) are a major fraction of the submicron particulate matter. OA consists of directly emitted primary (POA) and secondary OA (SOA). SOA is formed in-situ in the atmosphere via the reaction of volatile organic precursors. The partitioning of SOA species depends not only on the exposure to oxidants, but for instance also on temperature, relative humidity (RH), and the absorptive mass chemical composition (presence of inorganics) and concentration. Vehicle exhaust is a known source of POA and likely contributes to SOA formation in urban areas [1;2]. This has recently been estimated by (i) analyzing ambient data from urban areas combined with fuel consumption data [3], (ii) by examining the chemical composition of raw fuels [4], or (iii) smog chamber studies [5, 6]. Contradictory and thus somewhat controversial results in the relative quantity of SOA from diesel vs. gasoline vehicle exhaust were observed. In order to elucidate the impact of variable ambient conditions on the potential SOA formation of vehicle exhaust, and its relation to the emitted gas phase species, we studied SOA formed from the exhaust of passenger cars and trucks as a function of fuel and engine type (gasoline, diesel) at different temperatures (T 22 vs. -7oC) and RH (40 vs. 90%), as well as with different levels of inorganic salt concentrations. The exhaust was sampled at the tailpipe during regulatory driving cycles on chassis dynamometers, diluted (200 - 400x) and introduced into the PSI mobile smog chamber [6], where the emissions were subjected to simulated atmospheric ageing. Particle phase instruments (HR-ToF-AMS, aethalometers, CPC, SMPS) and gas phase instruments (PTR-TOF-MS, CO, CO2, CH4, THC, NH3 and other gases) were used online during the experiments. We found that gasoline emissions, because of cold starts, were generally larger than diesel, especially during cold temperatures driving cycles. Gasoline vehicles also showed the highest SOA formation

  13. Dismantling of Evaporators by Laser Cutting Measurement of Secondary Emissions

    International Nuclear Information System (INIS)

    Pilot, Guy; Fauvel, Sylvain; Gosse, Xavier; De Dinechin, Guillaume

    2006-01-01

    In order to dismantle the evaporators of an obsolete reprocessing plant in Marcoule, studies were carried out by IRSN (Institut de Radioprotection et de Surete Nucleaire) / DSU/SERAC in cooperation with CEA (power laser group) on the laser cutting of steel structures, on the request of COGEMA (now AREVA NC) /Marcoule (UP1 dismantling project manager) and CEA/UMODD (UP1 dismantling owner). The aim of these studies was: - to quantify and to characterize the secondary emissions produced by Nd-YAG laser cutting of Uranus 65 steel pieces representative of UP1 evaporator elements and to examine the influence of different parameters, - to qualify a pre-filtration technique and particularly an electrostatic precipitator, - to compare the Nd-YAG used with other cutting tools previously studied. The experiments, which took place in a 35 m 3 ventilated cutting cell, allow to underline the following points: for the Uranus 65 steel, the sedimented dross, the deposits on the walls of the cutting cell and the aerosols drawn in the ventilation exhaust duct (∼ 275 m 3 /h), represent respectively between 92% and 99%, between 0.01% and 0.25% and between 1% and 8% of the total collected mass, the attached slag varies much from one configuration to the other and can sometimes amount to a relatively important fraction of the total mass, the kerves vary from 2 mm up to 7 mm for the Uranus 65 steel plates (thickness: 13.8 mm for the single plate and 12.8 + 3.5 mm for the double plate), the exhausted aerosol mass per cut length (g/m) decreases with the cutting speed, varies neither with the stand-off nor with the gas pressure, is dependent upon the gas nature (for the double plate), increases with the laser power, is strongly affected by the nature of the steel (stainless steel or mild steel) and is independent upon the plate position, the size distribution of aerosols is multimodal with a main mode often around 0.45 μm, the electrostatic precipitator has been a satisfactory prefilter

  14. Reflection of the energy structure of a tungsten monocrystal nearsurface area in the secondary electron spectrum

    International Nuclear Information System (INIS)

    Artamonov, O.M.; Smirnov, O.M.; Terekhov, A.N.

    1982-01-01

    Formation of secondary electron energy spectrum during emission from the crystal layer near the surface has been considered, at that layer energy structure can be different from volumetric energy structure. Its thickness depends on the predominant mechanism of electron scattering and is determined by corresponding phenomenological parameters. It is shown that the structure in the secondary electron spectrum appears in the case when energy structure of emitting monocrystal layer can not be described in the approximation of almost free electron gas and, as experimental investigations show, approaches energy zone structure of its volume. It is also show that in the case when the energy structure of the emitting layer is satisfactorily described with the model of almost free electron gas, the SE spectrum is characterized with traditional cascade minimum. Experimental investigation of SE energy distribution was carried out for the W monocrystalline face (110). It was established that distinct structure in the SE spectrum appears only after electrochemical polishing of the specimen surface. It is related to the appearance of ''far'' order in the monocrystal emission layer on initially disturbed tungsten surface during such treatment. Disturbance of tungsten monocrystal surface structure on its oxidation in O 2 atmosphere results in the appearance of the cascade maximum and disappearance of distinct peculiarities in the SE spectrum

  15. Multi-technique application of a double reflection electron emission microscope

    International Nuclear Information System (INIS)

    Jian-liang, J.; Bao-gui, S.; Guo-jun, Z

    2002-01-01

    Full text: In this paper the results acquired with the most recently developed double reflection electron emission microscope applied in different imaging modes are presented. The novel illumination system is based on a (100)-oriented single crystalline W wire electron microreflector and an electron gun placed in the back focal plane of the immersion objective. After being elastically reflected from the W tip surface, the primary electrons of energy ranging from 1 to 6 keV are decelerated to the desired impact energy in the range 0 to 200 eV for mirror electron microscopy (MEM), low energy electron emission microscopy (LEEM) and low energy electron diffraction (LEED) modes or to 5 keV for the secondary electron imaging mode. Photoelectron emission microscopy (PEEM), MEM, LEEM, secondary images of Pd/Si(111) and a set of selected area LEED patterns of the W(100) surface taken at energies ranging from 5 to 40 eV are presented for the first time. Copyright (2002) Australian Society for Electron Microscopy Inc

  16. Development of a secondary electron energy analyzer for a transmission electron microscope.

    Science.gov (United States)

    Magara, Hideyuki; Tomita, Takeshi; Kondo, Yukihito; Sato, Takafumi; Akase, Zentaro; Shindo, Daisuke

    2018-04-01

    A secondary electron (SE) energy analyzer was developed for a transmission electron microscope. The analyzer comprises a microchannel plate (MCP) for detecting electrons, a coil for collecting SEs emitted from the specimen, a tube for reducing the number of backscattered electrons incident on the MCP, and a retarding mesh for selecting the energy of SEs incident on the MCP. The detection of the SEs associated with charging phenomena around a charged specimen was attempted by performing electron holography and SE spectroscopy using the energy analyzer. The results suggest that it is possible to obtain the energy spectra of SEs using the analyzer and the charging states of a specimen by electron holography simultaneously.

  17. Axial ion-electron emission microscopy of IC radiation hardness

    Science.gov (United States)

    Doyle, B. L.; Vizkelethy, G.; Walsh, D. S.; Swenson, D.

    2002-05-01

    A new system for performing radiation effects microscopy (REM) has been developed at Sandia National Laboratory in Albuquerque. This system combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional Tandem Van de Graaff-Pelletron to velocities of 1.9 MeV/amu. The electronic stopping power for heavy ions is near a maximum at this velocity, and their range is ˜20 μm in Si. These ions therefore represent the most ionizing form of radiation in nature, and are nearly ideal for performing single event effects testing of integrated circuits. Unfortunately, the energy definition of the RFQ-boosted ions is rather poor (˜ a few %), which makes problematic the focussing of such ions to the submicron spots required for REM. To circumvent this problem, we have invented ion electron emission microscopy (IEEM). One can perform REM with the IEEM system without focussing or scanning the ion beam. This is because the position on the sample where each ion strikes is determined by projecting ion-induced secondary electrons at high magnification onto a single electron position sensitive detector. This position signal is then correlated with each REM event. The IEEM system is now mounted along the beam line in an axial geometry so that the ions pass right through the electron detector (which is annular), and all of the electrostatic lenses used for projection. The beam then strikes the sample at normal incidence which results in maximum ion penetration and removes a parallax problem experienced in an earlier system. Details of both the RFQ-booster and the new axial IEEM system are given together with some of the initial results of performing REM on Sandia-manufactured radiation hardened integrated circuits.

  18. Secondary electron interactions in materials with environmental and radiological interest

    International Nuclear Information System (INIS)

    Garcia, G.; Blanco, F.; Pablos, J.L. de; Perez, J.M.; Williart, A.

    2003-01-01

    Important environmental and radiological applications require energy deposition models including the interactions between secondary electrons and the atoms or molecules of the medium. In this work we propose a method to obtain reliable cross-section data to be used in these models by combining total and ionization cross-section measurements with simple calculations of the differential and integral elastic cross-sections. The energy loss spectra obtained in this experiment have been also used to drive stopping power of the considered materials for electrons. Some examples of results for atomic (Xe) and molecular (CF 4 ) targets are presented and discussed in this paper. (author)

  19. In-situ measurements of the secondary electron yield in an accelerator environment: Instrumentation and methods

    International Nuclear Information System (INIS)

    Hartung, W.H.; Asner, D.M.; Conway, J.V.; Dennett, C.A.; Greenwald, S.; Kim, J.-S.; Li, Y.; Moore, T.P.; Omanovic, V.; Palmer, M.A.; Strohman, C.R.

    2015-01-01

    The performance of a particle accelerator can be limited by the build-up of an electron cloud (EC) in the vacuum chamber. Secondary electron emission from the chamber walls can contribute to EC growth. An apparatus for in-situ measurements of the secondary electron yield (SEY) in the Cornell Electron Storage Ring (CESR) was developed in connection with EC studies for the CESR Test Accelerator program. The CESR in-situ system, in operation since 2010, allows for SEY measurements as a function of incident electron energy and angle on samples that are exposed to the accelerator environment, typically 5.3 GeV counter-rotating beams of electrons and positrons. The system was designed for periodic measurements to observe beam conditioning of the SEY with discrimination between exposure to direct photons from synchrotron radiation versus scattered photons and cloud electrons. The samples can be exchanged without venting the CESR vacuum chamber. Measurements have been done on metal surfaces and EC-mitigation coatings. The in-situ SEY apparatus and improvements to the measurement tools and techniques are described

  20. In-situ measurements of the secondary electron yield in an accelerator environment: Instrumentation and methods

    Energy Technology Data Exchange (ETDEWEB)

    Hartung, W.H., E-mail: wh29@cornell.edu; Asner, D.M.; Conway, J.V.; Dennett, C.A.; Greenwald, S.; Kim, J.-S.; Li, Y.; Moore, T.P.; Omanovic, V.; Palmer, M.A.; Strohman, C.R.

    2015-05-21

    The performance of a particle accelerator can be limited by the build-up of an electron cloud (EC) in the vacuum chamber. Secondary electron emission from the chamber walls can contribute to EC growth. An apparatus for in-situ measurements of the secondary electron yield (SEY) in the Cornell Electron Storage Ring (CESR) was developed in connection with EC studies for the CESR Test Accelerator program. The CESR in-situ system, in operation since 2010, allows for SEY measurements as a function of incident electron energy and angle on samples that are exposed to the accelerator environment, typically 5.3 GeV counter-rotating beams of electrons and positrons. The system was designed for periodic measurements to observe beam conditioning of the SEY with discrimination between exposure to direct photons from synchrotron radiation versus scattered photons and cloud electrons. The samples can be exchanged without venting the CESR vacuum chamber. Measurements have been done on metal surfaces and EC-mitigation coatings. The in-situ SEY apparatus and improvements to the measurement tools and techniques are described.

  1. A study on the secondary electrons in a clinical electron beam

    International Nuclear Information System (INIS)

    Krithivas, G.; Rao, S.N.

    1989-01-01

    The central axis dose of a 12 MeV clinical electron beam is investigated in terms of an axial component due to primary electrons in the central ray and a lateral component due to secondary electrons originating from multiple scattering of electrons in the off-axis rays. To this effect secondary electron fluence measurements in a polystyrene medium irradiated with a collimated beam are made with a sensitive diode detector. This leads to a construction of secondary electron depth-dose profiles for beam sizes of diameters ranging from 1.7 to 17.4 cm. The results indicate that the lateral electrons account for 25% of the dose in the therapeutic region. For these electrons, the depth of dose maximum is correlated with diffusion depth and maximum lateral excursion in the medium. Dose component due to backscatter electrons at depths is also investigated using a thin-window parallel-plate ion chamber. The role of lateral and backscatter electrons in characterising central axis per cent depth-dose is discussed. (author)

  2. Monte Carlo simulation of kinetic electron emission from metal due to impact of heavy ions

    International Nuclear Information System (INIS)

    Kawata, J.; Ohya, K.

    1999-01-01

    A Monte Carlo simulation is performed for study of the dependence of kinetic electron emission on nuclear charge of projectile Z 1 , using the nonlinear response theory with the density-functional (DF) formalism to calculate electron excitation cross section. The kinetic yield, energy distribution, excitation depth distribution and emission statistics of emitted electrons showed clear Z 1 oscillations, however, the Z 1 oscillations of them are different from that of the inelastic stopping power, in particular for high Z 1 , due to large elastic energy loss of the ions and secondary cascade process of primary excited electrons within the solid. For high Z 1 , the linear relationship does not exist between them and the inelastic stopping power, although they are closely related to it. The emission of high-energy primary electrons excited by the ion within shallow depth without experiencing the secondary cascade process, results in the Z 1 dependence in the energy distribution, excitation depth distribution and emission statistics of emitted electrons

  3. Stimulated emission of photoexcited polarized electrons from GaAs

    International Nuclear Information System (INIS)

    Derbenev, Ya.S.; Melikyan, R.A.

    1986-01-01

    The influence of electric field on the emission of photoexcited polarized electrons is investigated. The thermalization of excited electrons is shown to be prevented at the field intensity in semiconductor of about 3 kV/cm. As a consequence the quantum yield grows up to unity. With the increase of the output energy of electrons the effective operation time of photocathode also increases

  4. Negative ion emission at field electron emission from amorphous (alpha-C:H) carbon

    CERN Document Server

    Bernatskij, D P; Ivanov-Omskij, V I; Pavlov, V G; Zvonareva, T K

    2001-01-01

    The study on the electrons field emission from the plane cathode surface on the basis of the amorphous carbon film (alpha-C:H) is carried out. The methodology, making it possible to accomplish simultaneously the registration of the emission currents and visually observe the distribution of the emission centers on the plane emitter surface is developed. The analysis of the oscillograms indicated that apart from the proper electron constituent the negative ions of hydrogen (H sup - and H sub 2 sup -), carbon (C sup -) and hydrocarbon (CH sub n sup -) are observed. The ions emission is connected with the processes of formation and degradation of the local emission centers

  5. The future of the SIRAD SEE facility Ion-Electron Emission Microscopy

    CERN Document Server

    Wyss, J; Kaminski, A; Magalini, A; Nigro, M; Pantano, D; Sedhykh, S

    2002-01-01

    The SIRAD facility is dedicated to radiation damage studies on semiconductor detectors, electronic devices and systems, using proton and ion beams delivered by a 15 MV tandem accelerator. It is routinely used by groups involved in detector development for elementary particle physics, electronic device physics and space applications. In particular, Single Event Effect studies are very important to the latter two activities. Presently, the facility can only characterize the global sensitivity of a device or system to single ion impacts. To map out the sensitivity of a device with micrometric resolution, following an idea developed at SANDIA, we will implement an Ion-Electron Emission Microscope (IEEM) to reconstruct the X,Y and time coordinates of an impacting energetic ion by imaging the secondary electrons emitted by the sample using a standard emission electron microscope and position sensitive detector system. After describing typical Single Event Effect activities at SIRAD we will discuss the basic princip...

  6. Secondary-electron-bremsstrahlung imaging for proton therapy

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Mitsutaka; Nagao, Yuto [Takasaki Advanced Radiation Research Institute, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-Machi, Takasaki, Gunma (Japan); Ando, Koki; Yamamoto, Seiichi [Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, 1-1-20 Daiko-Minami, Higashi-Ku, Nagoya, Aichi (Japan); Toshito, Toshiyuki [Department of Proton Therapy Physics, Nagoya Proton Therapy Center, Nagoya City West Medical Center, 1-1-1 Hirate-cho, Kita-Ku, Nagoya, Aichi (Japan); Kataoka, Jun [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo (Japan); Kawachi, Naoki [Takasaki Advanced Radiation Research Institute, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki-Machi, Takasaki, Gunma (Japan)

    2016-10-11

    A feasibility study on an imaging technique of a therapeutic proton-beam trajectory using a gamma camera by measuring secondary electron bremsstrahlung (SEB) was performed by means of Monte Carlo simulations and a beam-irradiation experiment. From the simulation and experimental results, it was found that a significant amount of SEB yield exists between the beam-injection surface and the range position along the beam axis and the beam trajectory is clearly imaged by the SEB yield. It is concluded that the SEB imaging is a promising technique for monitoring of therapeutic proton-beam trajectories.

  7. New secondary batteries utilizing electronically conductive polymer cathodes

    Science.gov (United States)

    Martin, Charles R.; White, Ralph E.

    1989-01-01

    The objectives of this project are to characterize the transport properties in electronically conductive polymers and to assess the utility of these films as cathodes in lithium/polymer secondary batteries. During this research period, progress has been made in a literature survey of the historical background, methods of preparation, the physical and chemical properties, and potential technological applications of polythiophene. Progress has also been made in the characterization of polypyrrole flat films and fibrillar films. Cyclic voltammetry and potential step chronocoulometry were used to gain information on peak currents and potentials switching reaction rates, charge capacity, and charge retention. Battery charge/discharge studies were also performed.

  8. Determination of secondary electron yields from low pressure breakdown

    International Nuclear Information System (INIS)

    Maric, D; Zivanov, S.; Strinic, A.; Malovic, G.; Djuric, M.; Petrovic, Z. Lj.

    2000-01-01

    In order to model accurately the secondary yields in gas breakdown and collisional plasmas both the numerous processes discussed in related experiments must be included and also proper determination of γ (E/n) must be provided. In addition to the application of the correct ionization rate it is also essential to include the nonequilibrium region where electrons gain energy and achieve hydrodynamics equilibrium. For lower values of E/n, greater values of γ than those based on the literature data for αn(E/n) have been found, possibly due to existence of the photoelectric effects

  9. Ion-induced electron emission from clean metals

    International Nuclear Information System (INIS)

    Baragiola, R.A.; Alonso, E.V.; Ferron, J.; Oliva-Florio, A.; Universidad Nacional de Cuyo, San Carlos de Bariloche

    1979-01-01

    We report recent experimental work on electron emission from clean polycrystalline metal surfaces under ion bombardment. We critically discuss existing theories and point out the presently unsolved problems. (orig.)

  10. Electron emission induced modifications in amorphous tetrahedral diamondlike carbon

    International Nuclear Information System (INIS)

    Mercer, T.W.; DiNardo, N.J.; Rothman, J.B.; Siegal, M.P.; Friedmann, T.A.; Martinez-Miranda, L.J.

    1998-01-01

    The cold-cathode electron emission properties of amorphous tetrahedral diamondlike carbon are promising for flat-panel display and vacuum microelectronics technologies. The onset of electron emission is, typically, preceded by open-quotes conditioningclose quotes where the material is stressed by an applied electric field. To simulate conditioning and assess its effect, we combined the spatially localized field and current of a scanning tunneling microscope tip with high-spatial-resolution characterization. Scanning force microscopy shows that conditioning alters surface morphology and electronic structure. Spatially resolved electron-energy-loss spectroscopy indicates that the predominant bonding configuration changes from predominantly fourfold to threefold coordination. copyright 1998 American Institute of Physics

  11. Delta-electron emission in fast heavy ion atom collisions

    International Nuclear Information System (INIS)

    Schmidt-Boecking, H.; Ramm, U.; Berg, H.; Kelbch, C.; Feng Jiazhen; Hagmann, S.; Kraft, G.; Ullrich, J.

    1991-01-01

    The δ-electron emission processes occuring in fast heavy ion atom collisons are explained qualitatively. The different spectral structures of electron emission arising from either the target or the projectile are explained in terms of simple models of the kinetics of momentum transfer induced by the COULOMB forces. In collisions of very heavy ions with matter, high nuclear COULOMB forces are created. These forces lead to a strong polarization of the electronic states of the participated electrons. The effects of this polarization are discussed. (orig.)

  12. Dependence of secondary ion emission current on the composition of beryllium-nickel alloys

    International Nuclear Information System (INIS)

    Pistryak, V.M.; Kozlov, V.F.; Tikhinskij, G.F.; Fogel', Ya.M.

    1976-01-01

    The dependence is studied of the secondary ions emission current on the composition of beryllium-nickel alloys. It is established that appearance of intermetallide phases in the Be-Ni alloys has no effect on the linear character of the secondary ions Ni + and Be + of emission current. The phase transformation from the solid solution to the compound Ni 5 Be 21 with a change in the alloys concentration is fixed by appearance of the secondary ion NiBe + emission. The limited solubility of nickel in solid beryllium at a temperature close to room temperature is determined to be equal to 1.3+-0.27 at%

  13. Electron cyclotron emission measurement in Tore Supra

    International Nuclear Information System (INIS)

    Javon, C.

    1991-06-01

    Electron cyclotron radiation from Tore-Supra is measured with Michelson and Fabry-Perot interferometers. Calibration methods, essential for this diagnostic, are developed allowing the determination of electron temperature in the plasma. In particular the feasibility of Fabry-Perot interferometer calibration by an original method is demonstrated. A simulation code is developed for modelling non-thermal electron population in these discharges using measurements in non-inductive current generation regime [fr

  14. Spin-dependent electron emission from metals in the neutralization of He+ ions

    International Nuclear Information System (INIS)

    Alducin, M.; Roesler, M.; Juaristi, J.I.; Muino, R. Diez; Echenique, P.M.

    2005-01-01

    We calculate the spin-polarization of electrons emitted in the neutralization of He + ions interacting with metals. All stages of the emission process are included: the spin-dependent perturbation induced by the projectile, the excitation of electrons in Auger neutralization processes, the creation of a cascade of secondaries, and the escape of the electrons through the surface potential barrier. The model allows us to explain in quantitative terms the measured spin-polarization of the yield in the interaction of spin-polarized He + ions with paramagnetic surfaces, and to disentangle the role played by each of the involved mechanisms. We show that electron-electron scattering processes at the surface determine the spin-polarization of the total yield. High energy emitted electrons are the ones providing direct information on the He + ion neutralization process and on the electronic properties of the surface

  15. Secondary electron spectroscopy and Auger microscopy at high spatial resolution. Application to scanning electron microscopy

    International Nuclear Information System (INIS)

    Le Gressus, Claude; Massignon, Daniel; Sopizet, Rene

    1979-01-01

    Secondary electron spectroscopy (SES), Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS) are combined with ultra high vacuum scanning microscopy (SEM) for surface analysis at high spatial resolution. Reliability tests for the optical column for the vacuum and for the spectrometer are discussed. Furthermore the sensitivity threshold in AES which is compatible with a non destructive surface analysis at high spatial resolution is evaluated. This combination of all spectroscopies is used in the study of the beam damage correlated with the well known secondary electron image (SEI) darkening still observed in ultra high vacuum. The darkening is explained as a bulk decontamination of the sample rather than as a surface contamination from the residual vacuum gas [fr

  16. Modelling of non-thermal electron cyclotron emission during ECRH

    International Nuclear Information System (INIS)

    Tribaldos, V.; Krivenski, V.

    1990-01-01

    The existence of suprathermal electrons during Electron Cyclotron Resonance Heating experiments in tokamaks is today a well established fact. At low densities the creation of large non-thermal electron tails affects the temperature profile measurements obtained by 2 nd harmonic, X-mode, low-field side, electron cyclotron emission. At higher densities suprathermal electrons can be detected by high-field side emission. In electron cyclotron current drive experiments a high energy suprathermal tail, asymmetric in v, is observed. Non-Maxwellian electron distribution functions are also typically observed during lower-hybrid current drive experiments. Fast electrons have been observed during ionic heating by neutral beams as well. Two distinct approaches are currently used in the interpretation of the experimental results: simple analytical models which reproduce some of the expected non-Maxwellian characteristics of the electron distribution function are employed to get a qualitative picture of the phenomena; sophisticated numerical Fokker-Planck calculations give the electron distribution function from which the emission spectra are computed. No algorithm is known to solve the inverse problem, i.e. to compute the electron distribution function from the emitted spectra. The proposed methods all relay on the basic assumption that the electron distribution function has a given functional dependence on a limited number of free parameters, which are then 'measured' by best fitting the experimental results. Here we discuss the legitimacy of this procedure. (author) 7 refs., 5 figs

  17. Application of Boltzmann equation to electron transmission and seconary electron emission

    International Nuclear Information System (INIS)

    Lanteri, H.; Bindi, R.; Rostaing, P.

    1979-01-01

    A method is presented for numerical treatment of integro-differential equation, based upon finite difference techniques. This method allows to formulate in a satisfactory manner the Boltzmann's equation applied to backscattering, transmission and secondary emission of metallic targets, avoiding must of the restrictive hypothesis, used until now in these models. For aluminium, the calculated energy spectra, angular distribution, transmission and backscattering coefficients, and secondary emission yield, are found to be in good agreement with experiment [fr

  18. The incidence angle influence on the structure of secondary-emission characteristics of single crystals

    International Nuclear Information System (INIS)

    Gasanov, E.R.; Aliyev, B.Z.

    2012-01-01

    Full text : The dependences of Wand MO single crystals in different atom planes have been studied in this work. It is revealed that maximums are added to each dependency and also minimums of first and second degree. This fact is explained by diffraction dynamic theory. It is established that electron diffraction oriented not perpendicularly to crystal surface is the reason of appearance of second order structure on studied secondary-emission characteristics. In the present work being the continuation and development of SEE investigations of high-melting metal single crystals begun earlier by authors, the structure dependence of SEE main characteristics of angle has been studied. This angle has been chosen because as it is mentioned before the bad repeatability in different experiments for it is observed

  19. Electron-beam-induced-current and active secondary-electron voltage-contrast with aberration-corrected electron probes

    Energy Technology Data Exchange (ETDEWEB)

    Han, Myung-Geun, E-mail: mghan@bnl.gov [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Garlow, Joseph A. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Materials Science and Engineering Department, Stony Brook University, Stony Brook, NY 11794 (United States); Marshall, Matthew S.J.; Tiano, Amanda L. [Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Wong, Stanislaus S. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Cheong, Sang-Wook [Department of Physics and Astronomy, Rutgers Center for Emergent Materials, Rutgers University, Piscataway, NJ 08854 (United States); Walker, Frederick J.; Ahn, Charles H. [Department of Applied Physics and Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520 (United States); Zhu, Yimei [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2017-05-15

    Highlights: • Electron-beam-induced-current (EBIC) and active secondary-electron voltage-contrast (SE-VC) are demonstrated in STEM mode combined with in situ electrical biasing in a TEM. • Electrostatic potential maps in ferroelectric thin films, multiferroic nanowires, and single crystals obtained by off-axis electron holography were compared with EBIC and SE-VC data. • Simultaneous EBIC and active SE-VC performed with atomic resolution STEM are demonstrated. - Abstract: The ability to map out electrostatic potentials in materials is critical for the development and the design of nanoscale electronic and spintronic devices in modern industry. Electron holography has been an important tool for revealing electric and magnetic field distributions in microelectronics and magnetic-based memory devices, however, its utility is hindered by several practical constraints, such as charging artifacts and limitations in sensitivity and in field of view. In this article, we report electron-beam-induced-current (EBIC) and secondary-electron voltage-contrast (SE-VC) with an aberration-corrected electron probe in a transmission electron microscope (TEM), as complementary techniques to electron holography, to measure electric fields and surface potentials, respectively. These two techniques were applied to ferroelectric thin films, multiferroic nanowires, and single crystals. Electrostatic potential maps obtained by off-axis electron holography were compared with EBIC and SE-VC to show that these techniques can be used as a complementary approach to validate quantitative results obtained from electron holography analysis.

  20. Electrically induced spontaneous emission in open electronic system

    Science.gov (United States)

    Wang, Rulin; Zhang, Yu; Yam, Chiyung; Computation Algorithms Division (CSRC) Team; Theoretical; Computational Chemistry (HKU) Collaboration

    A quantum mechanical approach is formulated for simulation of electroluminescence process in open electronic system. Based on nonequilibrium Green's function quantum transport equations and combining with photon-electron interaction, this method is used to describe electrically induced spontaneous emission caused by electron-hole recombination. The accuracy and reliability of simulation depends critically on correct description of the electronic band structure and the electron occupancy in the system. In this work, instead of considering electron-hole recombination in discrete states in the previous work, we take continuous states into account to simulate the spontaneous emission in open electronic system, and discover that the polarization of emitted photon is closely related to its propagation direction. Numerical studies have been performed to silicon nanowire-based P-N junction with different bias voltage.

  1. Monte Carlo modeling of ion beam induced secondary electrons

    Energy Technology Data Exchange (ETDEWEB)

    Huh, U., E-mail: uhuh@vols.utk.edu [Biochemistry & Cellular & Molecular Biology, University of Tennessee, Knoxville, TN 37996-0840 (United States); Cho, W. [Electrical and Computer Engineering, University of Tennessee, Knoxville, TN 37996-2100 (United States); Joy, D.C. [Biochemistry & Cellular & Molecular Biology, University of Tennessee, Knoxville, TN 37996-0840 (United States); Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2016-09-15

    Ion induced secondary electrons (iSE) can produce high-resolution images ranging from a few eV to 100 keV over a wide range of materials. The interpretation of such images requires knowledge of the secondary electron yields (iSE δ) for each of the elements and materials present and as a function of the incident beam energy. Experimental data for helium ions are currently limited to 40 elements and six compounds while other ions are not well represented. To overcome this limitation, we propose a simple procedure based on the comprehensive work of Berger et al. Here we show that between the energy range of 10–100 keV the Berger et al. data for elements and compounds can be accurately represented by a single universal curve. The agreement between the limited experimental data that is available and the predictive model is good, and has been found to provide reliable yield data for a wide range of elements and compounds. - Highlights: • The Universal ASTAR Yield Curve was derived from data recently published by NIST. • IONiSE incorporated with the Curve will predict iSE yield for elements and compounds. • This approach can also handle other ion beams by changing basic scattering profile.

  2. Electron collision effects on the bremsstrahlung emission in Lorentzian plasmas

    International Nuclear Information System (INIS)

    Jung, Young-Dae; Kato, Daiji

    2009-06-01

    The electron-electron collision effects on the electron-ion bemsstranhlung process are investigated in warm Lorentzian plasmas. The effective electron-ion interaction potential is obtained by including the far-field terms caused by the electron-electron collisions with the effective Debye length in Lorentzian plasmas. The bremsstranhlung radiation cross section is obtained as a function of the electron energy, photon energy, collision frequency, spectral index, and Debye length using the Born approximation for the initial and final states of the projectile electron. It is shown that the non-Maxwellian character suppresses the bremsstrahlung radiation cross section. It is also shown that the electron-electron collision effect enhances the bremsstrahlung emission spectrum. In addition, the bremsstrahlung radiation cross section decreases with an increase of the plasma temperature. (author)

  3. Backscattered electron emission after proton impact on carbon and gold films: Experiments and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Hespeels, F.; Heuskin, A.C. [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium); Scifoni, E. [TIFPA-INFN, Trento Institute for Fundamental Physics and Applications, Via Sommarive 14, I-38123 Trento (Italy); GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Kraemer, M. [GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Lucas, S., E-mail: stephane.lucas@unamur.be [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium)

    2017-06-15

    This work aims at measuring the proton induced secondary electron energy spectra from nanometer thin films. Backscattered electron energy spectra were measured within an energy range from 0 to 600 eV using a Retarding Field Analyser (RFA). This paper presents energy spectra obtained for proton (0.5 MeV; 1 MeV; 1.5 MeV; 2 MeV) irradiation of thin carbon films (50 and 100 nm thick) and thin gold film (200 nm). These experimental spectra were compared with Monte Carlo simulations based on TRAX code and Geant4 simulation toolkit. Good agreement between experimental, TRAX and Geant4 results were observed for the carbon target. For the gold target, we report major differences between both Monte Carlo environments. Limitation of Geant4 models for low energy electron emission was highlighted. On the contrary, TRAX simulations present encouraging results for the modeling of low-energy electron emission from gold target.

  4. Electron emission regulator for an x-ray tube filament

    International Nuclear Information System (INIS)

    Daniels, H.E.; Randall, H.G.

    1982-01-01

    An x-ray tube ma regulator has an scr phase shift voltage regulator supplying the primary winding of a transformer whose secondary is coupled to the x-ray tube filament. Prior to initiation of an x-ray exposure, the filament is preheated to a temperature corresponding substantially to the electron emissivity needed for obtaining the desired tube ma during an exposure. During the preexposure interval, the phase shift regulator is controlled by a signal corresponding to the sum of signals representative of the voltage applied to the filament transformer, the desired filament voltage and the space charge compensation needed for the selected x-ray tube anode to cathode voltage. When an exposure is initiated, control of the voltage regulator is switched to a circuit that responds to the tube current by controlling the amount of phase shift and, hence, the voltage supplied to the transformer. Transformer leakage current compensation is provided during the exposure interval with a circuit that includes an element whose impedance is varied in accordance with the anode-to-cathode voltage setting so the element drains off tube current as required to cancel the effect of leakage current variations

  5. Secondary ion formation during electronic and nuclear sputtering of germanium

    Science.gov (United States)

    Breuer, L.; Ernst, P.; Herder, M.; Meinerzhagen, F.; Bender, M.; Severin, D.; Wucher, A.

    2018-06-01

    Using a time-of-flight mass spectrometer attached to the UNILAC beamline located at the GSI Helmholtz Centre for Heavy Ion Research, we investigate the formation of secondary ions sputtered from a germanium surface under irradiation by swift heavy ions (SHI) such as 5 MeV/u Au by simultaneously recording the mass spectra of the ejected secondary ions and their neutral counterparts. In these experiments, the sputtered neutral material is post-ionized via single photon absorption from a pulsed, intensive VUV laser. After post-ionization, the instrument cannot distinguish between secondary ions and post-ionized neutrals, so that both signals can be directly compared in order to investigate the ionization probability of different sputtered species. In order to facilitate an in-situ comparison with typical nuclear sputtering conditions, the system is also equipped with a conventional rare gas ion source delivering a 5 keV argon ion beam. For a dynamically sputter cleaned surface, it is found that the ionization probability of Ge atoms and Gen clusters ejected under electronic sputtering conditions is by more than an order of magnitude higher than that measured for keV sputtered particles. In addition, the mass spectra obtained under SHI irradiation show prominent signals of GenOm clusters, which are predominantly detected as positive or negative secondary ions. From the m-distribution for a given Ge nuclearity n, one can deduce that the sputtered material must originate from a germanium oxide matrix with approximate GeO stoichiometry, probably due to residual native oxide patches even at the dynamically cleaned surface. The results clearly demonstrate a fundamental difference between the ejection and ionization mechanisms in both cases, which is interpreted in terms of corresponding model calculations.

  6. Surfing Silicon Nanofacets for Cold Cathode Electron Emission Sites.

    Science.gov (United States)

    Basu, Tanmoy; Kumar, Mohit; Saini, Mahesh; Ghatak, Jay; Satpati, Biswarup; Som, Tapobrata

    2017-11-08

    Point sources exhibit low threshold electron emission due to local field enhancement at the tip. In the case of silicon, however, the realization of tip emitters has been hampered by unwanted oxidation, limiting the number of emission sites and the overall current. In contrast to this, here, we report the fascinating low threshold (∼0.67 V μm -1 ) cold cathode electron emission from silicon nanofacets (Si-NFs). The ensembles of nanofacets fabricated at different time scales, under low energy ion impacts, yield tunable field emission with a Fowler-Nordheim tunneling field in the range of 0.67-4.75 V μm -1 . The local probe surface microscopy-based tunneling current mapping in conjunction with Kelvin probe force microscopy measurements revealed that the valleys and a part of the sidewalls of the nanofacets contribute more to the field emission process. The observed lowest turn-on field is attributed to the absence of native oxide on the sidewalls of the smallest facets as well as their lowest work function. In addition, first-principle density functional theory-based simulation revealed a crystal orientation-dependent work function of Si, which corroborates well with our experimental observations. The present study demonstrates a novel way to address the origin of the cold cathode electron emission sites from Si-NFs fabricated at room temperature. In principle, the present methodology can be extended to probe the cold cathode electron emission sites from any nanostructured material.

  7. Discussion of the origin of secondary photon and secondary ion emission during energetic particle irradiation of solids. I. The collision cascade

    International Nuclear Information System (INIS)

    Wright, R.B.; Gruen, D.M.

    1980-01-01

    Secondary photon and secondary ion emission during energetic particle irradiation of solid surfaces is assumed to arise due to excitation and de-excitation of sputtered particles originating from a collision cascade induced by the incident projectile. The excitation is postulated to occur by two alternative mechanisms: path (a), where excitation occurs at or very near the surface of the solid due to atom--atom or atom--electron collisions; and path (b), where excitation occurs as the sputtered particle leaves the solid, but is still under its influence so that electron exchange processes are permitted. Once the excited and/or ionized sputtered particle is formed nonradiative de-excitation processes are then included in the discussion which allow the excited and/or ionized particle to be de-excited and/or neutralized. The result of these nonradiative de-excitation processes is shown to provide a possible channel for the formation of new excited ''daughters'' by the de-excitation of the initial excited ''parent''. Depending on the initial excitation probability of the parent the new excited daughters are shown to contribute to various energy regions of the excited and/or ionized secondary particle energy distribution. A mathematical formalism is developed based on the neutral sputtered atom energy and velocity distributions assuming a collision cascade origin for these sputtered particles. By including various models for the excitation probability, and the survival probability for excited particles once formed to not undergo nonradiative de-excitation the resulting energy and velocity distributions of the sputtered excited and/or ionized secondary particles are calculated. These distributions are found to be a function of the emission angle depending on the model assumed for the initial excitation. From this formalism the total excited secondary particle yield may be calculated

  8. Electron field emission characteristics of carbon nanotube on tungsten tip

    International Nuclear Information System (INIS)

    Phan Ngoc Hong; Bui Hung Thang; Nguyen Tuan Hong; Phan Ngoc Minh; Lee, Soonil

    2009-01-01

    Electron field emission characteristic of carbon nanotubes on tungsten tip was investigated in 2x10 -6 Torr vacuum. The measurement results showed that the CNTs/W tip could emit electron at 0.7 V/μm (nearly 10 times lower than that of the W tip itself) and reach up to 26 μA at the electric field of 1 V/μm. The emission characteristic follows the Fowler-Nordheim mechanism. Analysis of the emission characteristic showed that the CNTs/W tip has a very high value of field enhancement factor (β = 4.1 x 10 4 cm -1 ) that is much higher than that of the tungsten tip itself. The results confirmed the excellent field emission behavior of the CNTs materials and the CNTs/W tip is a prospective candidate for advanced electron field emitter.

  9. Potential applications of electron emission membranes in medicine

    Energy Technology Data Exchange (ETDEWEB)

    Bilevych, Yevgen [Fraunhofer Institute for Reliability and Microintegration (IZM), Berlin (Germany); University of Bonn, Bonn (Germany); Brunner, Stefan E. [Delft University of Technology, Delft (Netherlands); Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Vienna (Austria); Chan, Hong Wah; Charbon, Edoardo [Delft University of Technology, Delft (Netherlands); Graaf, Harry van der, E-mail: vdgraaf@nikhef.nl [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Hagen, Cornelis W. [Delft University of Technology, Delft (Netherlands); Nützel, Gert; Pinto, Serge D. [Photonis, Roden (Netherlands); Prodanović, Violeta [Delft University of Technology, Delft (Netherlands); Rotman, Daan [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); University of Amsterdam, Amsterdam (Netherlands); Santagata, Fabio [State Key Lab for Solid State Lighti Changzhou base, F7 R& D HUB 1, Science and Education Town, Changzhou 213161, Jangsu Province (China); Sarro, Lina; Schaart, Dennis R. [Delft University of Technology, Delft (Netherlands); Sinsheimer, John; Smedley, John [Brookhaven National Laboratory, Upton, NY (United States); Tao, Shuxia; Theulings, Anne M.M.G. [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands)

    2016-02-11

    With a miniaturised stack of transmission dynodes, a noise free amplifier is being developed for the detection of single free electrons, with excellent time- and 2D spatial resolution and efficiency. With this generic technology, a new family of detectors for individual elementary particles may become possible. Potential applications of such electron emission membranes in medicine are discussed.

  10. Development of Field-Emission Electron Gun from Carbon Nanotubes

    CERN Document Server

    Hozumi, Y

    2004-01-01

    Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2

  11. Electron emission from tungsten surface induced by neon ions

    International Nuclear Information System (INIS)

    Xu, Zhongfeng; Zeng, Lixia; Zhao, Yongtao; Liu, Xueliang; Xiao, Guoqing; Li, Fuli; Cheng, Rui; Zhang, Xiaoan; Ren, Jieru; Zhou, Xianming; Wang, Xing; Lei, Yu; Li, Yongfeng; Yu, Yang

    2014-01-01

    The electron emission from W surface induced by Ne q+ has been measured. For the same charge state, the electron yield gradually increases with the projectile velocity. Meanwhile, the effect of the potential energy of projectile has been found obviously. Our results give the critical condition for ''trampoline effect''

  12. Electron emission from tungsten surface induced by neon ions

    Science.gov (United States)

    Xu, Zhongfeng; Zeng, Lixia; Zhao, Yongtao; Cheng, Rui; Zhang, Xiaoan; Ren, Jieru; Zhou, Xianming; Wang, Xing; Lei, Yu; Li, Yongfeng; Yu, Yang; Liu, Xueliang; Xiao, Guoqing; Li, Fuli

    2014-04-01

    The electron emission from W surface induced by Neq+ has been measured. For the same charge state, the electron yield gradually increases with the projectile velocity. Meanwhile, the effect of the potential energy of projectile has been found obviously. Our results give the critical condition for "trampoline effect".

  13. Wave packet study of the secondary emission of negatively charged, monoatomic ions from sputtered metals

    Energy Technology Data Exchange (ETDEWEB)

    Sindona, A. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy) and Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy)]. E-mail: sindona@fis.unical.it; Riccardi, P. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy); Maletta, S. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Rudi, S.A. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy); Falcone, G. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy)

    2007-05-15

    Secondary emission of Ag{sup -} and Au{sup -} particles, following the sputtering of clean Ag(1 0 0) and Au(1 0 0) targets, respectively, is studied with a Crank-Nicholson wave-packet propagation method. A one-electron pseudo-potential is used to describe the plane metal surface, with a projected band gap, the ejected ion, whose charge state is investigated, and its nearest-neighbor substrate ion, put in motion by the collision cascade generated by the primary ion beam. Time-dependent Schroedinger equation is solved backwards in time to determine the evolution of the affinity orbital of the negative particles from an instant when they are unperturbed, at distances of the order of {approx}10{sup 2} a.u. from the surface, to the instant of ejection. The probability that a band electron will be eventually detected in affinity state of the ejected particle is, thus, calculated and compared with the result of another method based on the spectral decomposition of the one-electron Hamiltonian.

  14. Tunneling-Electron-Induced Light Emission from Single Gold Nanoclusters.

    Science.gov (United States)

    Yu, Arthur; Li, Shaowei; Czap, Gregory; Ho, W

    2016-09-14

    The coupling of tunneling electrons with the tip-nanocluster-substrate junction plasmon was investigated by monitoring light emission in a scanning tunneling microscope (STM). Gold atoms were evaporated onto the ∼5 Å thick Al2O3 thin film grown on the NiAl (110) surface where they formed nanoclusters 3-7 nm wide. Scanning tunneling spectroscopy (STS) of these nanoclusters revealed quantum-confined electronic states. Spatially resolved photon imaging showed localized emission hot spots. Size dependent study and light emission from nanocluster dimers further support the viewpoint that coupling of tunneling electrons to the junction plasmon is the main radiative mechanism. These results showed the potential of the STM to reveal the electronic and optical properties of nanoscale metallic systems in the confined geometry of the tunnel junction.

  15. Electron emission from Inconel under ion bombardment

    International Nuclear Information System (INIS)

    Alonso, E.V.; Baragiola, R.A.; Ferron, J.; Oliva-Florio, A.

    1979-01-01

    Electron yields from clean and oxidized Inconel 625 surfaces have been measured for H + ,H 2 + ,He + ,O + and Ar + ions at normal incidence in the energy range 1.5 to 40 keV. These measurements have been made under ultrahigh vacuum and the samples were freed of surface contaminants by bombarding with high doses of either 20 keV H 2 + or 30 keV Ar + ions. Differences in yields of oxidized versus clean surfaces are explained in terms of differences in the probability that electrons internally excited escape upon reaching the surface. (author)

  16. Schemes of Superradiant Emission from Electron Beams and "Spin-Flip Emission of Radiation"

    CERN Document Server

    Gover, A

    2005-01-01

    A unified analysis for Superradiant emission from bunched electron beams in various kinds of radiation scheme is presented. Radiation schemes that can be described by the formulation include Pre-bunched FEL (PB-FEL), Coherent Synchrotron Radiation (CSR), Smith-Purcell Radiation, Cerenkov-Radiation, Transition-Radiation and more. The theory is based on mode excitation formulation - either discrete or continuous (the latter - in open structures). The discrete mode formulation permits simple evaluation of the spatially coherent power and spectral power of the source. These figures of merit of the radiation source are useful for characterizing and comparing the performance of different radiation schemes. When the bunched electron beam emits superradiantly, these parameters scale like the square of the number of electrons, orders of magnitude more than spontaneous emission. The formulation applies to emission from single electron bunches, periodically bunched beams, or emission from a finite number of bunches in a...

  17. 77 FR 16987 - National Emission Standards for Hazardous Air Pollutants: Secondary Aluminum Production

    Science.gov (United States)

    2012-03-23

    ... National Emission Standards for Hazardous Air Pollutants: Secondary Aluminum Production AGENCY... for secondary aluminum production (77 FR 8576). The EPA is extending the deadline for written comments... from the Aluminum Association. The Aluminum Association has requested the extension in order to allow...

  18. Application of scandium oxide in an electron emission material

    International Nuclear Information System (INIS)

    Suqiu, Y.; Zhizheng, Z.; Yongde, W.

    1985-01-01

    Modern microwave devices impose a number of harsh requirements on the cathodes. For instance, they require cathodes having low working temperature, high emissive current density, slow evaporation rate of the emissive-active material, long lifetime, quick heating and so on. The commercial B-cathode is no longer able to meet these requirements completely. A scandate cathode may be a promising one for use in these devices. Adding rare-earth elements in the electron emission material has been reported in many papers. Based on a B-cathode we add a little amount of scandium oxide (about 3%) into emission material to manufacture a scandate cathode. The emission property of such a cathode has been improved greatly. If the composition is controlled correctly, the emission level of such a cathode may be five times more as high as the B-cathode

  19. Research on nonlinearity effect of secondary electron multiplier

    International Nuclear Information System (INIS)

    Wei Xingjian; Liao Junsheng; Deng Dachao; Yu Chunrong; Yuan Li

    2007-01-01

    The nonlinearity of secondary electron multiplier (SEM) of a thermal ionization mass spectrometer has been researched by using UTB-500 uranium isotope reference material and multi-collecting technique. The results show that the nonlinearity effect of SEM exists in the whole ion counting range, and there is an extreme point of the nonlinearity when the ion counting rate is about 20000 cps. The deviation between measured value of the extreme point and the reference value of the reference sample can be up to 3%, and the nonlinearity obeys logarithm linearity law on both sides of extreme point. A kind of mathematics model of nonlinearity calibration has been put forward. Using this model, the nonlinearity of SEM of TIMS can be calibrated. (authors)

  20. Low Secondary Electron Yield Carbon Coatings for Electron Cloud Mitigation in Modern Particle Accelerators

    CERN Document Server

    Yin Vallgren, Christina; Taborelli, Mauro

    2011-01-01

    In order to upgrade the Large Hadron Collider (LHC) performance to be oriented towards higher energies and higher intensities in the future, a series of improvements of the existing LHC injectors is planned to take place over the next few years. Electron cloud effects are expected to be enhanced and play a central role in limiting the performance of the machines of the CERN complex. Electron cloud phenomena in beam pipes are based on electron multiplication and can be sufficiently suppressed if the Secondary Electron Yield (SEY) of the surface of the beam pipes is lower than unity. The goal of this work is to find and study a thin film coating with reliably low initial Secondary Electron Yield (SEY), which does not require bake-out or conditioning in situ with photons, is robust again air exposure and can easily be applied in the beam pipes of accelerators. In this work, amorphous carbon (a-C) thin films have been prepared by DC magnetron sputtering for electron cloud mitigation and antimultipactor applicatio...

  1. Surface-electronic-state effects in electron emission from the Be(0001) surface

    International Nuclear Information System (INIS)

    Archubi, C. D.; Gravielle, M. S.; Silkin, V. M.

    2011-01-01

    We study the electron emission produced by swift protons impinging grazingly on a Be(0001) surface. The process is described within a collisional formalism using the band-structure-based (BSB) approximation to represent the electron-surface interaction. The BSB model provides an accurate description of the electronic band structure of the solid and the surface-induced potential. Within this approach we derive both bulk and surface electronic states, with these latter characterized by a strong localization at the crystal surface. We found that such surface electronic states play an important role in double-differential energy- and angle-resolved electron emission probabilities, producing noticeable structures in the electron emission spectra.

  2. Surface-electronic-state effects in electron emission from the Be(0001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Archubi, C. D. [Instituto de Astronomia y Fisica del Espacio, casilla de correo 67, sucursal 28, C1428EGA, Buenos Aires (Argentina); Gravielle, M. S. [Instituto de Astronomia y Fisica del Espacio, casilla de correo 67, sucursal 28, C1428EGA, Buenos Aires (Argentina); Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Silkin, V. M. [Donostia International Physics Center, E-20018 San Sebastian (Spain); Departamento de Fisica de Materiales, Facultad de Ciencias Quimicas, Universidad del Pais Vasco, Apartado 1072, E-20080 San Sebastian (Spain); IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao (Spain)

    2011-07-15

    We study the electron emission produced by swift protons impinging grazingly on a Be(0001) surface. The process is described within a collisional formalism using the band-structure-based (BSB) approximation to represent the electron-surface interaction. The BSB model provides an accurate description of the electronic band structure of the solid and the surface-induced potential. Within this approach we derive both bulk and surface electronic states, with these latter characterized by a strong localization at the crystal surface. We found that such surface electronic states play an important role in double-differential energy- and angle-resolved electron emission probabilities, producing noticeable structures in the electron emission spectra.

  3. Electron beam induced emission from carbon plasmas

    International Nuclear Information System (INIS)

    Whetstone, S.; Kammash, T.

    1989-01-01

    Plasma use as a lasing medium has many potential advantages over conventional techniques including increased power levels and greater wavelength ranges. The basic concept is to heat and then rapidly cool a plasma forcing inversion through bottleneck creation between the recombination reaction populating a given energy level and the subsequent decay processes. Much effort has been devoted to plasmas heated by lasers and pinch devices. The authors are concerned here with electron beam heated plasmas focusing on the CIV 5g-4f transition occurring at 2530 Angstroms. These studies were initiated to provide theoretical support for experiments being performed at the University of Michigan using the Michigan Electron Long-Pulse Beam Accelerator (MELBA)

  4. Field electron emission from dense array of microneedles of tungsten

    International Nuclear Information System (INIS)

    Okuyama, F.; Aoyagi, M.; Kitai, T.; Ishikawa, K.

    1978-01-01

    Characteristics of field electron emission from the dense array of microneedles of tungsten prepared on a 10-μm tungsten filament were measured at an environmental pressure of approx.1 x 10 -8 Torr (1.33 x 10 -6 Pa). Electron emission was not uniform over the filament surface, but the variation of emission current with applied voltage explicitly obeyed the Fowler-Nordheim relationship. At an emission current of approx.10 -4 A, a vacuum arc was induced that led to a permanent change in current-voltage characteristic. Current fluctuation was dependent on emitter temperature and applied voltage, and the lowest fluctuation of about 4% was routinely obtained at approx.550 K and at applied voltages several percent lower than the arc-inducing voltage. Macroscopic current density amounted to approx.20-80 mA/cm 2 at the best stability

  5. PLASMA EMISSION BY COUNTER-STREAMING ELECTRON BEAMS

    Energy Technology Data Exchange (ETDEWEB)

    Ziebell, L. F.; Petruzzellis, L. T.; Gaelzer, R. [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD (United States); Pavan, J., E-mail: luiz.ziebell@ufrgs.br, E-mail: yoonp@umd.edu, E-mail: joel.pavan@ufpel.edu.br [Instituto de Física e Matemática, UFPel, Pelotas, RS (Brazil)

    2016-02-10

    The radiation emission mechanism responsible for both type-II and type-III solar radio bursts is commonly accepted as plasma emission. Recently Ganse et al. suggested that type-II radio bursts may be enhanced when the electron foreshock geometry of a coronal mass ejection contains a double hump structure. They reasoned that the counter-streaming electron beams that exist between the double shocks may enhance the nonlinear coalescence interaction, thereby giving rise to more efficient generation of radiation. Ganse et al. employed a particle-in-cell simulation to study such a scenario. The present paper revisits the same problem with EM weak turbulence theory, and show that the fundamental (F) emission is not greatly affected by the presence of counter-streaming beams, but the harmonic (H) emission becomes somewhat more effective when the two beams are present. The present finding is thus complementary to the work by Ganse et al.

  6. Multiplicity of secondary electrons emitted by carbon thin targets by impact of H0, H2+ and H3+ projectiles at MeV energies

    International Nuclear Information System (INIS)

    Vidovic, Zvonimir

    1997-01-01

    This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H 0 , H 2 + and H 3 + projectiles in the 0.25 - 2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. Phenomenological and theoretical descriptions as well as a summary of the main theoretical models are the subjects of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of the thin carbon foils crossed by an energetic projectile is described in the chapter two. In this chapter there are also presented the method and the algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H 0 atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H 2 + and H 3 + polyatomic ions. The results are interpreted in terms of collective effects in the interactions of the ions with solids. The role of the proximity of the protons, molecular ions fragments, upon the amplitude of these collected effects is evidenced from the study of the statistics of forward emission. The experiments allowed us to shed light on various aspects of atom and polyatomic ion interactions with solid surfaces. (author)

  7. The secondary electron yield of noble metal surfaces

    Directory of Open Access Journals (Sweden)

    L. A. Gonzalez

    2017-11-01

    Full Text Available Secondary electron yield (SEY curves in the 0-1000 eV range were measured on polycrystalline Ag, Au and Cu samples. The metals were examined as introduced in the ultra-high vacuum chamber and after having been cleaned by Ar+ ion sputtering. The comparison between the curves measured on the clean samples and in the presence of contaminants, due to the permanence in atmosphere, confirmed that the SEY behavior is strongly influenced by the chemical state of the metal surface. We show that when using very slow primary electrons the sample work function can be determined with high accuracy from the SEY curves. Moreover we prove that SEY is highly sensitive to the presence of adsorbates even at submonolayer coverage. Results showing the effect of small quantities of CO adsorbed on copper are presented. Our findings demonstrate that SEY, besides being an indispensable mean to qualify technical materials in many technological fields, can be also used as a flexible and advantageous diagnostics to probe surfaces and interfaces.

  8. Calculations of secondary electron yield of graphene coated copper for vacuum electronic applications

    Directory of Open Access Journals (Sweden)

    H. K. A. Nguyen

    2018-01-01

    Full Text Available The suppression of secondary electron yield (SEY which can possibly lead to multipactor is an important goal for several applications. Though some techniques have focused on geometric modifications to lower the SEY, the use of graphene coatings as thin as a few monolayers is a promising new development that deserves attention either as a standalone technique or in concert with geometric alterations. Here we report on Monte Carlo based numerical studies of SEY on graphene coated copper with comparisons to recent experimental data. Our predicted values are generally in good agreement with reported measurements. Suppression of the secondary electron yield by as much as 50 percent (over copper with graphene coating is predicted at energies below 125 eV, and bodes well for multipactor suppression in radio frequency applications.

  9. Emission from Crystals Irradiated with a Beam of Runaway Electrons

    Science.gov (United States)

    Buranchenko, A. G.; Tarasenko, V. F.; Beloplotov, D. V.; Baksht, E. Kh.

    2018-01-01

    An investigation of the spectral and amplitude-temporal characteristics of emission from different crystals, promising in terms of their application as detectors of runaway electrons, is performed. This emission is excited by subnanosecond electron beams generated in a gas diode. It is found out that at the electron energies of tens-hundreds of kiloelectronvolts, the main contribution into the emission from CsI, ZnS, type IIa artificial and natural diamonds, sapphire, CaF2, ZrO2, Ga2O3, CaCO3, CdS, and ZnSe crystals comes from the cathodoluminescence; the radiation pulse duration depends on the crystal used and sufficiently exceeds the Cherenkov radiation pulse duration. It is demonstrated that the latter radiation exhibits low intensity and can be detected in the short-wave region of the spectrum in the cases where a monochromator and a high-sensitivity photomultiplier tube (PMT) are used.

  10. The Effect of Gas Ion Bombardment on the Secondary Electron Yield of TiN, TiCN and TiZrV Coatings For Suppressing Collective Electron Effects in Storage Rings

    International Nuclear Information System (INIS)

    Le Pimpec, F.; Kirby, R.E.; King, F.K.; Pivi, M.

    2006-01-01

    In many accelerator storage rings running positively charged beams, ionization of residual gas and secondary electron emission (SEE) in the beam pipe will give rise to an electron cloud which can cause beam blow-up or loss of the circulating beam. A preventative measure that suppresses electron cloud formation is to ensure that the vacuum wall has a low secondary emission yield (SEY). The SEY of thin films of TiN, sputter deposited Non-Evaporable Getters and a novel TiCN alloy were measured under a variety of conditions, including the effect of re-contamination from residual gas

  11. Study of luminous emissions associated to electron emissions in radiofrequency cavities

    International Nuclear Information System (INIS)

    Maissa, S.

    1996-01-01

    This study investigates luminous emissions simultaneously to electron emissions and examines their features in order to better understand the field electron emission phenomenon. A RF cavity, operating at room temperature and in pulsed mode, joined to a sophisticated experimental apparatus has been especially developed. The electron and luminous emissions are investigated on cleaned or with metallic, graphitic and dielectric particles contaminated RF surfaces in order to study their influence on these phenomena. During the surface processing, unstable luminous spots glowing during one RF pulse are detected. Their apparition is promoted in the vicinity of the metallic particles or scratches. Two hypotheses could explain their origin: the presence of micro-plasmas associated to electronic explosive emission during processing or the thermal radiation of the melted metal during this emission. Stable luminous spots glowing during several RF pulses are also detected and appear to increase on RF surfaces contaminated with dielectric particles, leading to strong and explosive luminous emissions. Two interpretations are considered: the initiation of surface breakdowns on the dielectric particles or the heating by the RF field at temperatures sufficiently intense to provoke their thermal radiation then their explosion. Finally a superconducting cavity has been adapted to observe luminous spots, which differ from the former ones bu their star shape and could be associated to micro-plasmas, revealed by the starbursts observed on superconducting cavity walls. (author)

  12. Direct and Recoil-Induced Electron Emission from Ion-Bombarded Solids

    DEFF Research Database (Denmark)

    Holmen, G.; Svensson, B.; Schou, Jørgen

    1979-01-01

    The kinetic emission of secondary electrons from ion-bombarded solid surfaces is split into two contributions, a direct one caused by ionizing collisions between the bombarding ion and target atoms, and an indirect one originating from ionizing collisions undergone by recoil atoms with other target...... atoms. The direct contribution, which has been treated by several authors in previous studies, shows a behavior that is determined primarily by the electronic stopping power of the bombarding ion, while the indirect contribution is nonproportionally related to the nuclear stopping power. This latter...

  13. Mechanisms of dust grain charging in plasma with allowance for electron emission processes

    Energy Technology Data Exchange (ETDEWEB)

    Mol’kov, S. I.; Savin, V. N., E-mail: moped@onego.ru [Petrozavodsk State University (Russian Federation)

    2017-02-15

    The process of dust grain charging is described with allowance for secondary, ion-induced, photoelectric, and thermal electron emission from the grain surface. The roughness of the grain surface is taken into account. An intermediate charging regime involving ion–atom collisions and electron ionization in the perturbed plasma region is analyzed using the moment equations and Poisson’s equation. A calculation method is proposed that allows one to take into account the influence of all the above effects and determine the radius of the plasma region perturbed by the dust grain.

  14. Electron field emission from boron doped microcrystalline diamond

    International Nuclear Information System (INIS)

    Roos, M.; Baranauskas, V.; Fontana, M.; Ceragioli, H.J.; Peterlevitz, A.C.; Mallik, K.; Degasperi, F.T.

    2007-01-01

    Field emission properties of hot filament chemical vapor deposited boron doped polycrystalline diamond have been studied. Doping level (N B ) of different samples has been varied by the B/C concentration in the gas feed during the growth process and doping saturation has been observed for high B/C ratios. Threshold field (E th ) for electron emission as function of B/C concentration has been measured, and the influences of grain boundaries, doping level and surface morphology on field emission properties have been investigated. Carrier transport through conductive grains and local emission properties of surface sites have been figured out to be two independent limiting effects in respect of field emission. Emitter current densities of 500 nA cm -2 were obtained using electric fields less than 8 V/μm

  15. ETRAN, Electron Transport and Gamma Transport with Secondary Radiation in Slab by Monte-Carlo

    International Nuclear Information System (INIS)

    1992-01-01

    photon will be produced in a single short step. Allowance is made for such a contingency by sampling the frequency of Bremsstrahlung production events from a Poisson distribution. The energy of the secondary Bremsstrahlung photons is subtracted from the energy of the electrons producing them. Thus photon emission contributes to the energy-loss straggling of the electrons. The photons are started out at a random position in the short step in a direction relative to that of the primary electron specified by the sampled intrinsic Bremsstrahlung emission angle. For problems in which the production of the thick-target Bremsstrahlung is of prime interest, there is an option to increase the rate of occurrence of Bremsstrahlung events artificially by a specified factor. The production of secondary characteristic x-rays in each short step is sampled with the use of the k-ionization cross sections of Arthurs and Moiseiwitsch and Kolbenstvedt. The programme is arranged so as to treat simultaneously many slab targets with different thicknesses. Boundary crossings (transmission and reflection) usually occur in the middle of a short step. The energy with which the electron crosses the border is determined by subtracting from the energy at the beginning of the step an energy loss sampled from the Landau- Blunck-Leisegang distribution for the fraction of the step taken to the boundary. The direction at the time of crossing is determined by changing the direction of motion at the beginning of the short step involved, using a deflection sampled from an exponential approximation to the Goudsmit-Saunderson distribution for the fraction of the short step to the boundary. The target is subdivided into many thin sub-layers of equal thickness, and the energy deposited in each sublayer is recorded for each sampled track

  16. Field emission from a new type of electron source

    International Nuclear Information System (INIS)

    Mousa, M.S.

    1987-01-01

    A new type of field emission electron source has been developed. In this paper, the construction, characteristics and behaviour of tungsten micropoint emitters coated with a sub-micron layer of hydrocarbon using a TEM with poor ( ∼ 1 0 -3 torr) vacuum conditions are described. The hydrocarbon coating has been verified using the X-Ray energy dispersive analysis technique of a SEM. The technical capabilities and potential of the new type of electron source are compared with those of other comparable composite micropoint field emitters and other types of electron sources currently in use. The emission properties presented here include I-V characteristics, emission images and electron energy spectra of this type of composite micropoint emitters. The effect on the behaviour and characteristics of baking the coated emitters at temperatures ranging between 140 0 C and 350 0 C is also studied. The behaviour of the emitter has been interpreted in terms of a field-induced hot-electron emission mechanism associated with metal-insulator-vacuum (M-I-V) regime

  17. Density and energy distribution of epithermal secondary electrons in a plasma with fast charged particles

    International Nuclear Information System (INIS)

    Jayakumar, R.; Fleischmann, H.H.

    1989-01-01

    The production of intermediate energy secondary electrons in plasmas through collisions with fast charged particles is investigated. The density and the distribution of the secondary electrons are obtained by calculating the generation, slow down and diffusion rates, using basic Rutherford collision cross sections. It is shown that the total density of secondaries is much smaller than the fast particle density and that the energy distribution has roughly a 1/√E dependence. The higher generation secondary populations are also obtained. (orig.)

  18. Electronic field emission models beyond the Fowler-Nordheim one

    Science.gov (United States)

    Lepetit, Bruno

    2017-12-01

    We propose several quantum mechanical models to describe electronic field emission from first principles. These models allow us to correlate quantitatively the electronic emission current with the electrode surface details at the atomic scale. They all rely on electronic potential energy surfaces obtained from three dimensional density functional theory calculations. They differ by the various quantum mechanical methods (exact or perturbative, time dependent or time independent), which are used to describe tunneling through the electronic potential energy barrier. Comparison of these models between them and with the standard Fowler-Nordheim one in the context of one dimensional tunneling allows us to assess the impact on the accuracy of the computed current of the approximations made in each model. Among these methods, the time dependent perturbative one provides a well-balanced trade-off between accuracy and computational cost.

  19. Effects of Enhanced Eathode Electron Emission on Hall Thruster Operation

    International Nuclear Information System (INIS)

    Raitses, Y.; Smirnov, A.; Fisch, N.J.

    2009-01-01

    Interesting discharge phenomena are observed that have to do with the interaction between the magnetized Hall thruster plasma and the neutralizing cathode. The steadystate parameters of a highly ionized thruster discharge are strongly influenced by the electron supply from the cathode. The enhancement of the cathode electron emission above its self-sustained level affects the discharge current and leads to a dramatic reduction of the plasma divergence and a suppression of large amplitude, low frequency discharge current oscillations usually related to an ionization instability. These effects correlate strongly with the reduction of the voltage drop in the region with the fringing magnetic field between the thruster channel and the cathode. The measured changes of the plasma properties suggest that the electron emission affects the electron cross-field transport in the thruster discharge. These trends are generalized for Hall thrusters of various configurations.

  20. Variability in the primary emissions and secondary gas and particle formation from vehicles using bioethanol mixtures.

    Science.gov (United States)

    Gramsch, E; Papapostolou, V; Reyes, F; Vásquez, Y; Castillo, M; Oyola, P; López, G; Cádiz, A; Ferguson, S; Wolfson, M; Lawrence, J; Koutrakis, P

    2018-04-01

    Bioethanol for use in vehicles is becoming a substantial part of global energy infrastructure because it is renewable and some emissions are reduced. Carbon monoxide (CO) emissions and total hydrocarbons (THC) are reduced, but there is still controversy regarding emissions of nitrogen oxides (NO x ), aldehydes, and ethanol; this may be a concern because all these compounds are precursors of ozone and secondary organic aerosol (SOA). The amount of emissions depends on the ethanol content, but it also may depend on the engine quality and ethanol origin. Thus, a photochemical chamber was used to study secondary gas and aerosol formation from two flex-fueled vehicles using different ethanol blends in gasoline. One vehicle and the fuel used were made in the United States, and the others were made in Brazil. Primary emissions of THC, CO, carbon dioxide (CO 2 ), and nonmethane hydrocarbons (NMHC) from both vehicles decreased as the amount of ethanol in gasoline increased. NO x emissions in the U.S. and Brazilian cars decreased with ethanol content. However, emissions of THC, CO, and NO x from the Brazilian car were markedly higher than those from the U.S. car, showing high variability between vehicle technologies. In the Brazilian car, formation of secondary nitrogen dioxide (NO 2 ) and ozone (O 3 ) was lower for higher ethanol content in the fuel. In the U.S. car, NO 2 and O 3 had a small increase. Secondary particle (particulate matter [PM]) formation in the chamber decreased for both vehicles as the fraction of ethanol in fuel increased, consistent with previous studies. Secondary to primary PM ratios for pure gasoline is 11, also consistent with previous studies. In addition, the time required to form secondary PM is longer for higher ethanol blends. These results indicate that using higher ethanol blends may have a positive impact on air quality. The use of bioethanol can significantly reduce petroleum use and greenhouse gas emissions worldwide. Given the extent of

  1. [Atmospheric emission of PCDD/Fs from secondary aluminum metallurgy industry in the southwest area, China].

    Science.gov (United States)

    Lu, Yi; Zhang, Xiao-Ling; Guo, Zhi-Shun; Jian, Chuan; Zhu, Ming-Ji; Deng, Li; Sun, Jing; Zhang, Qin

    2014-01-01

    Five secondary aluminum metallurgy enterprises in the southwest area of China were measured for emissions of PCDD/Fs. The results indicated that the emission levels of PCDD/Fs (as TEQ) were 0.015-0.16 ng x m(-3), and the average was 0.093 ng x m(-3) from secondary aluminum metallurgy enterprises. Emission factors of PCDD/Fs (as TEQ) from the five secondary aluminum metallurgy enterprises varied between 0.041 and 4.68 microg x t(-1) aluminum, and the average was 2.01 microg x t(-1) aluminum; among them, PCDD/Fs emission factors from the crucible smelting furnace was the highest. Congener distribution of PCDD/F in stack gas from the five secondary aluminum metallurgies was very different from each other. Moreover, the R(PCDF/PCDD) was the lowest in the enterprise which was installed only with bag filters; the R(PCDF/PCDD) were 3.8-12.6 (the average, 7.7) in the others which were installed with water scrubbers. The results above indicated that the mechanism of PCDD/Fs formation was related to the types of exhaust gas treatment device. The results of this study can provide technical support for the formulation of PCDD/Fs emission standards and the best available techniques in the secondary aluminum metallurgy industry.

  2. Comparison of secondary ion emission yields for poly-tyrosine between cluster and heavy ion impacts

    International Nuclear Information System (INIS)

    Hirata, K.; Saitoh, Y.; Chiba, A.; Yamada, K.; Takahashi, Y.; Narumi, K.

    2010-01-01

    Emission yields of secondary ions necessary for the identification of poly-tyrosine were compared for incident ion impacts of energetic cluster ions (0.8 MeV C 8 + , 2.4 MeV C 8 + , and 4.0 MeV C 8 + ) and swift heavy monoatomic molybdenum ions (4.0 MeV Mo + and 14 MeV Mo 4+ ) with similar mass to that of the cluster by time-of-flight secondary ion mass analysis combined with secondary ion electric current measurements. The comparison revealed that (1) secondary ion emission yields per C 8 + impact increase with increasing incident energy within the energy range examined, (2) the 4.0 MeV C 8 + impact provides higher emission yields than the impact of the monoatomic Mo ion with the same incident energy (4.0 MeV Mo + ), and (3) the 2.4 MeV C 8 + impact exhibits comparable emission yields to that for the Mo ion impact with higher incident energy (14 MeV Mo 4+ ). Energetic cluster ion impacts effectively produce the characteristic secondary ions for poly-tyrosine, which is advantageous for highly sensitive amino acid detection in proteins using time-of-flight secondary ion mass analysis.

  3. First results of correlation electron cyclotron emission on Tore Supra

    OpenAIRE

    Udintsev, V. S.; Goniche, M.; Ségul, J.L.; Giruzzi, G.; Molina, D.; Turco, F.; Huysmans, G. T. A.; Maget, P.; Krämer-Flecken, A.

    2006-01-01

    Measurements of electron temperature fluctuations by means of correlation electron cyclotron emission (ECE) diagnostics aid in understanding the nature of the turbulent transport infusion plasmas. On Tore Supra tokamak, a 32-channel heterodyne ECE radiometer has been upgraded to include two channels for temperature fluctuation measurements. The central frequency of the yttrium iron garnet filter on each channel is remotely monitored by a driver, allowing one to shift the observation volume in...

  4. Electron-emission processes in highly charged Ar and Xe ions impinging on highly ordered pyrolytic graphite at energies just above the kinetic threshold

    NARCIS (Netherlands)

    Bodewits, E.; Hoekstra, R.; Dobes, K.; Aumayr, F.

    2014-01-01

    At keV energies, many electronic processes contribute to the emission of secondary electrons in the interaction of highly charged ions on surfaces. To unravel contributions resulting from isolated hollow atoms in front of the surface or embedded in the electron gas of the target, heavy highly

  5. Coherent secondary emission from resonantly excited two-exciton states

    DEFF Research Database (Denmark)

    Birkedal, Dan

    2000-01-01

    The coherent interaction of light and the electronic states of semiconductors near the fundamental bandgap has been a very active topic of research since the advent of ultrafast lasers. While many of the ultrafast nonlinear properties of semiconductors have been well explained within mean field...

  6. Electron cyclotron emission measurements at the stellarator TJ-K

    Energy Technology Data Exchange (ETDEWEB)

    Sichardt, Gabriel; Ramisch, Mirko [Institut fuer Grenzflaechenverfahrenstechnik und Plasmatechnologie, Universitaet Stuttgart (Germany); Koehn, Alf [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)

    2016-07-01

    Electron temperature (T{sub e}) measurements in the magnetised plasmas of the stellarator TJ-K are currently performed by means of Langmuir probes. The use of these probes is restricted to relatively low temperatures and the measurement of temperature profiles requires the acquisition of the local current-voltage characteristics which limits strongly the sampling rate. As an alternative, T{sub e} can be measured using the electron cyclotron emission (ECE) that is generated by the gyration of electrons in magnetised plasmas. Magnetic field gradients in the plasma lead to a spatial distribution of emission frequencies and thus the measured intensity at a given frequency can be related to its point of origin. The T{sub e} dependence of the intensity then leads to a temperature profile along the line of sight for Maxwellian velocity distributions. A diagnostic system for T{sub e} measurements using ECE is currently being set up at TJ-K. When non-thermal electrons are present the emission spectrum changes dramatically. Therefore, the ECE can also be used to investigate the contribution of fast electrons to previously observed toroidal net currents in TJ-K. Simulations are used to examine the role of electron drift orbits in generating these currents.

  7. Secondary Electron Yield on Cryogenic Surfaces as a Function of Physisorbed Gases

    CERN Document Server

    Kuzucan, Asena; Taborelli, Mauro

    2011-01-01

    In LHC the electron cloud induced by photoelectrons, gas ionization and secondary electrons emitted from the beam pipe walls could be a limitation of the performance. The electron cloud induce heat load on the cryogenic system, cause pressure rise, emittance growth and beam instabilities, which in the end will limit the beam’s lifetime. Beam- induced multipacting, which can arise through oscillatory motion of photoelectrons and low-energy secondary electrons bouncing back and forth between opposite walls of the vacuum chamber during successive passage of proton bunches, represent therefore a potential problem for the machine. The secondary electron yield (SEY) is one of the key parameters for the electron cloud build up and multipacting phenomenon. An electron cloud occurs if the metal surface secondary electron yield is high enough for electron multiplication. This parameter has been extensively studied on room temperature samples but uncertainties remain for samples at cryogenic temperature. Indeed, at l...

  8. Effect of electron emission on an ion sheath structure

    International Nuclear Information System (INIS)

    Mishra, M K; Phukan, A; Chakraborty, M

    2014-01-01

    This article reports on the variations of ion sheath structures due to the emission of both hot and cold electrons in the target plasma region of a double plasma device. The ion sheath is produced in front of a negatively biased plate. The plasma is produced by hot filament discharge in the source region, and no discharge is created in the target region of the device. The plate is placed in the target (diffused plasma) region where cold electron emitting filaments are present. These cold electrons are free from maintenance of discharge, which is sustained in the source region. The hot ionizing electrons are present in the source region. Three important parameters are changed by both hot and cold electrons i.e. plasma density, plasma potential and electron temperature. The decrease in plasma potential and the increase in plasma density lead to the contraction of the sheath. (paper)

  9. Perpendicular electron cyclotron emission from hot electrons in TMX-U

    International Nuclear Information System (INIS)

    James, R.A.; Ellis, R.F.; Lasnier, C.J.; Casper, T.A.; Celata, C.M.

    1984-01-01

    Perpendicular electron cyclotron emission (PECE) from the electron cyclotron resonant heating of hot electrons in TMX-U is measured at 30 to 40 and 50 to 75 GHz. This emission is optically thin and is measured at the midplane, f/sub ce/ approx. = 14 GHz, in either end cell. In the west end cell, the emission can be measured at different axial positions thus yielding the temporal history of the hot electron axial profile. These profiles are in excellent agreement with the axial diamagnetic signals. In addition, the PECE signal level correlates well with the diamagnetic signal over a wide range of hot electron densities. Preliminary results from theoretical modeling and comparisons with other diagnostics are also presented

  10. Detectors, sampling, shielding, and electronics for positron emission tomography

    International Nuclear Information System (INIS)

    Derenzo, S.E.

    1981-08-01

    A brief discussion of the important design elements for positron emission tomographs is presented. The conclusions are that the instrumentation can be improved by the use of larger numbers of small, efficient detectors closely packed in many rings, the development of new detector materials, and novel electronic designs to reduce the deadtime and increase maximum event rates

  11. Characteristics of the fast electron emission produced during the ...

    Indian Academy of Sciences (India)

    water adsorption and other characteristics of the fast electron emission ..... that the surface charges which leak away when there is adosrbed water on ... implies that it is a measure of the supply of excited species rather than due to the charge.

  12. Electron emission in collisions of intermediate energy ions with atoms

    International Nuclear Information System (INIS)

    Garibotti, C.R.

    1988-01-01

    The aim of this work, is the analysis of the processes of electronic emission produced in the collisions of small ions (H + , He ++ ) of intermediate energy (50 a 200 KeV/amu) with light gaseous targets. (A.C.A.G.) [pt

  13. Characterization of Carbon Coatings with Low Secondary Electron Yield

    CERN Document Server

    Yin Vallgren, C; Costa Pinto, P; Kuzucan, A; Neupert, H; Taborelli, M

    2011-01-01

    Amorphous carbon (a-C) coatings can reliably be produced with a maximum secondary electron yield (SEY) close to 1 at room temperature. Measurements at low temperature (LHe) are in progress. Analysis by X-ray Photoemission Spectroscopy (XPS) shows a correlation between the lineshape of C1s spectrum in XPS and the maximum SEY of the investigated samples. The initial level of oxygen on the surface of the various samples does not seem to be related to the initial maximum SEY value. However, the increase of the SEY with air exposure time on each individual sample is related to the amount of oxygen containing adsorbates. Storage in different environments has been investigated (static vacuum, aluminium foil, dry nitrogen and desiccators), and shows significant differences in the “aging” behaviour. Aging is very moderate when storing samples wrapped in aluminium foil in air. Samples which have undergone aging due to inappropriate storage can be recovered nearly to the initial value of their SEY by surface treatme...

  14. Electron-electron collision effects on the bremsstrahlung emission in Lorentzian plasmas

    International Nuclear Information System (INIS)

    Jung, Young-Dae; Kato, Daiji

    2009-01-01

    Electron-electron collision effects on the electron-ion bremsstrahlung process are investigated in Lorentzian plasmas. The effective electron-ion interaction potential is obtained by including the far-field terms caused by electron-electron collisions with an effective Debye length in Lorentzian plasmas. The bremsstrahlung radiation cross section is obtained as a function of the electron energy, photon energy, collision frequency, spectral index and Debye length using the Born approximation for the initial and final states of the projectile electron. It is shown that the non-Maxwellian character suppresses the bremsstrahlung radiation cross section. It is also shown that the electron-electron collision effect enhances the bremsstrahlung emission spectrum. In addition, the bremsstrahlung radiation cross section decreases with an increase in the plasma temperature.

  15. Interpretation of secondary electron images obtained using a low vacuum SEM

    International Nuclear Information System (INIS)

    Toth, M.; Thiel, B.L.; Donald, A.M.

    2003-01-01

    Charging of insulators in a variable pressure environment was investigated in the context of secondary electron (SE) image formation. Sample charging and ionized gas molecules present in a low vacuum specimen chamber can give rise to SE image contrast. 'Charge-induced' SE contrast reflects lateral variations in the charge state of a sample caused by electron irradiation during and prior to image acquisition. This contrast corresponds to SE emission current alterations produced by sub-surface charge deposited by the electron beam. 'Ion-induced' contrast results from spatial inhomogeneities in the extent of SE signal inhibition caused by ions in the gaseous environment of a low vacuum scanning electron microscope (SEM). The inhomogeneities are caused by ion focusing onto regions of a sample that correspond to local minima in the magnitude of the surface potential (generated by sub-surface trapped charge), or topographic asperities. The two types of contrast exhibit characteristic dependencies on microscope operating parameters such as scan speed, beam current, gas pressure, detector bias and working distance. These dependencies, explained in terms of the behavior of the gaseous environment and sample charging, can serve as a basis for a correct interpretation of SE images obtained using a low vacuum SEM

  16. A new oxidation flow reactor for measuring secondary aerosol formation of rapidly changing emission sources

    Science.gov (United States)

    Simonen, Pauli; Saukko, Erkka; Karjalainen, Panu; Timonen, Hilkka; Bloss, Matthew; Aakko-Saksa, Päivi; Rönkkö, Topi; Keskinen, Jorma; Dal Maso, Miikka

    2017-04-01

    Oxidation flow reactors (OFRs) or environmental chambers can be used to estimate secondary aerosol formation potential of different emission sources. Emissions from anthropogenic sources, such as vehicles, often vary on short timescales. For example, to identify the vehicle driving conditions that lead to high potential secondary aerosol emissions, rapid oxidation of exhaust is needed. However, the residence times in environmental chambers and in most oxidation flow reactors are too long to study these transient effects ( ˜ 100 s in flow reactors and several hours in environmental chambers). Here, we present a new oxidation flow reactor, TSAR (TUT Secondary Aerosol Reactor), which has a short residence time ( ˜ 40 s) and near-laminar flow conditions. These improvements are achieved by reducing the reactor radius and volume. This allows studying, for example, the effect of vehicle driving conditions on the secondary aerosol formation potential of the exhaust. We show that the flow pattern in TSAR is nearly laminar and particle losses are negligible. The secondary organic aerosol (SOA) produced in TSAR has a similar mass spectrum to the SOA produced in the state-of-the-art reactor, PAM (potential aerosol mass). Both reactors produce the same amount of mass, but TSAR has a higher time resolution. We also show that TSAR is capable of measuring the secondary aerosol formation potential of a vehicle during a transient driving cycle and that the fast response of TSAR reveals how different driving conditions affect the amount of formed secondary aerosol. Thus, TSAR can be used to study rapidly changing emission sources, especially the vehicular emissions during transient driving.

  17. Double differential distributions of electron emission in ion-atom and electron-atom collisions using an electron spectrometer

    International Nuclear Information System (INIS)

    Misra, Deepankar; Thulasiram, K.V.; Fernandes, W.; Kelkar, Aditya H.; Kadhane, U.; Kumar, Ajay; Singh, Yeshpal; Gulyas, L.; Tribedi, Lokesh C.

    2009-01-01

    We study electron emission from atoms and molecules in collisions with fast electrons and heavy ions (C 6+ ). The soft collision electrons (SE), two center electron emission (TCEE), the binary encounter (BE) events and the KLL Auger lines along with the elastically scattered peaks (in electron collisions) are studied using a hemispherical electrostatic electron analyzer. The details of the measurements along with description of the spectrometer and data acquisition system are given. The angular distributions of the low energy (few eV) electrons in soft collisions and the binary encounter electrons at keV energies are compared with quantum mechanical models based on the first Born (B1) and the continuum distorted wave-Eikonal initial state approximation (CDW-EIS).

  18. Gasoline emissions dominate over diesel in formation of secondary organic aerosol mass

    Science.gov (United States)

    Bahreini, R.; Middlebrook, A. M.; de Gouw, J. A.; Warneke, C.; Trainer, M.; Brock, C. A.; Stark, H.; Brown, S. S.; Dube, W. P.; Gilman, J. B.; Hall, K.; Holloway, J. S.; Kuster, W. C.; Perring, A. E.; Prevot, A. S. H.; Schwarz, J. P.; Spackman, J. R.; Szidat, S.; Wagner, N. L.; Weber, R. J.; Zotter, P.; Parrish, D. D.

    2012-03-01

    Although laboratory experiments have shown that organic compounds in both gasoline fuel and diesel engine exhaust can form secondary organic aerosol (SOA), the fractional contribution from gasoline and diesel exhaust emissions to ambient SOA in urban environments is poorly known. Here we use airborne and ground-based measurements of organic aerosol (OA) in the Los Angeles (LA) Basin, California made during May and June 2010 to assess the amount of SOA formed from diesel emissions. Diesel emissions in the LA Basin vary between weekdays and weekends, with 54% lower diesel emissions on weekends. Despite this difference in source contributions, in air masses with similar degrees of photochemical processing, formation of OA is the same on weekends and weekdays, within the measurement uncertainties. This result indicates that the contribution from diesel emissions to SOA formation is zero within our uncertainties. Therefore, substantial reductions of SOA mass on local to global scales will be achieved by reducing gasoline vehicle emissions.

  19. Electron beam injection during active experiments. I - Electromagnetic wave emissions

    Science.gov (United States)

    Winglee, R. M.; Kellogg, P. J.

    1990-01-01

    The wave emissions produced in Echo 7 experiment by active injections of electron beams were investigated to determine the properties of the electromagnetic and electrostatic fields for both the field-aligned and cross-field injection in such experiments and to evaluate the sources of free energy and relative efficiencies for the generation of the VLF and HF emissions. It is shown that, for typical beam energies in active experiments, electromagnetic effects do not substantially change the bulk properties of the beam, spacecraft charging, and plasma particle acceleration. Through simulations, beam-generated whistlers; fundamental z-mode and harmonic x-mode radiation; and electrostatic electron-cyclotron, upper-hybrid, Langmuir, and lower-hybrid waves were identified. The characteristics of the observed wave spectra were found to be sensitive to both the ratio of the electron plasma frequency to the cyclotron frequency and the angle of injection relative to the magnetic field.

  20. Novel simulation method of space charge effects in electron optical systems including emission of electrons

    Czech Academy of Sciences Publication Activity Database

    Zelinka, Jiří; Oral, Martin; Radlička, Tomáš

    2018-01-01

    Roč. 184, JAN (2018), s. 66-76 ISSN 0304-3991 R&D Projects: GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : space charge * self-consistent simulation * aberration polynomial * electron emission Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.843, year: 2016

  1. Electron cyclotron emission measurements on JET: Michelson interferometer, new absolute calibration, and determination of electron temperature

    NARCIS (Netherlands)

    Schmuck, S.; Fessey, J.; Gerbaud, T.; Alper, B.; Beurskens, M. N. A.; de la Luna, E.; Sirinelli, A.; Zerbini, M.

    2012-01-01

    At the fusion experiment JET, a Michelson interferometer is used to measure the spectrum of the electron cyclotron emission in the spectral range 70-500 GHz. The interferometer is absolutely calibrated using the hot/cold technique and, in consequence, the spatial profile of the plasma electron

  2. A new approach to nuclear microscopy: The ion-electron emission microscope

    International Nuclear Information System (INIS)

    Doyle, B.L.; Vizkelethy, G.; Walsh, D.S.; Senftinger, B.; Mellon, M.

    1998-01-01

    A new multidimensional high lateral resolution ion beam analysis technique, Ion-Electron Emission Microscopy or IEEM is described. Using MeV energy ions, IEEM is shown to be capable of Ion Beam Induced Charge Collection (IBICC) measurements in semiconductors. IEEM should also be capable of microscopically and multidimensionally mapping the surface and bulk composition of solids. As such, IIEM has nearly identical capabilities as traditional nuclear microprobe analysis, with the advantage that the ion beam does not have to be focused. The technique is based on determining the position where an individual ion enters the surface of the sample by projection secondary electron emission microscopy. The x-y origination point of a secondary electron, and hence the impact coordinates of the corresponding incident ion, is recorded with a position sensitive detector connected to a standard photoemission electron microscope (PEEM). These signals are then used to establish coincidence with IBICC, atomic, or nuclear reaction induced ion beam analysis signals simultaneously caused by the incident ion

  3. On novel mechanisms of slow ion induced electron emission

    International Nuclear Information System (INIS)

    Eder, H.

    2000-09-01

    The present work has contributed in new ways to the field of slow ion induced electron emission. First, measurements of the total electron yield γ for impact of slow singly and multiply charged ions on atomically clean polycrystalline gold and graphite have been made. The respective yields were determined by current measurements and measurements of the electron number statistics. A new mechanism for kinetic emission (KE) below the so called 'classical threshold' was found and discussed. For a given ion species and impact velocity a slight decrease of the yields was found for ion charge state q = 1 toward 3, but no significant differences in KE yields for higher q values. Comparison of the results from gold and graphite showed overall similar behavior, but for C+ a relatively strong difference was observed and ascribed to more effective electron promotion in the C-C- than in the C-Au system. Secondly, for the very specific system H0 on LiF we investigated single electron excitation processes under grazing incidence conditions. In this way long-range interactions of hydrogen atoms with the ionic crystal surface could be probed. Position- and velocity-dependent electron production rates were found which indicate that an electron promotion mechanism is responsible for the observed electron emission. Thirdly, in order to investigate the importance of plasmon excitation and -decay in slow ion induced electron emission, measurements of electron energy distributions from impact of singly and doubly charged ions on poly- and monocrystalline aluminum surfaces were performed. From the results we conclude that direct plasmon excitation by slow ions occurs due to the potential energy of the projectile in a quasi-resonant fashion. The highest relative plasmon intensities were found for impact of 5 keV Ne+ on Al(111) with 5 % of the total yield. For impact of H + and H 2 + characteristical differences were observed for Al(111) and polycrystalline aluminum. We show that

  4. Secondary organic aerosol production from modern diesel engine emissions

    Directory of Open Access Journals (Sweden)

    S. Samy

    2010-01-01

    Full Text Available Secondary organic aerosol (SOA production was observed at significant levels in a series of modern diesel exhaust (DE aging experiments conducted at the European Outdoor Photoreactor/Simulation Chamber (EUPHORE. The greatest production occurred in DE with toluene addition experiments (>40%, followed by DE with HCHO (for OH radical generation experiments. A small amount of SOA (3% was observed for DE in dark with N2O5 (for NO3 radical production experiments. The analysis for a limited number (54 of polar organic compounds (POC was conducted to assess the composition of modern DE and the formation of photochemical transformation products. Distinct POC formation in light versus dark experiments suggests the role of OH initiated reactions in these chamber atmospheres. A trend of increasing concentrations of dicarboxylic acids in light versus dark experiments was observed when evaluated on a compound group basis. The four toluene addition experiments in this study were performed at different [tol]o/[NOx]o ratios and displayed an average SOA %yield (in relation to toluene of 5.3±1.6%, which is compared to past chamber studies that evaluated the impact of [tol]o/[NOx]o on SOA production in more simplified mixtures.

  5. HIGH-CURRENT COLD CATHODE FIELD EMISSION ARRAY FOR ELECTRON LENS APPLICATION

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-12-28

    During Phase I, the following goals were achieved: (1) design and fabrication of a novel, nano-dimensional CNT field emitter assembly for high current density application, with high durability; (2) fabrication of a ceramic based micro channel plate (MCP) and characterization of its secondary electron emission; and (3) characterizing the CNT/MCP cathode for high field emission and durability. As a result of these achievements, a relatively high current density of ~ 1.2 A/cm2 from a CNT cathode and single channel MCP were measured. The emission current was also extremely stable with a peak-to-peak variation of only 1.8%. The emission current could be further enhanced to meet requirements for electron lens applications by increasing the number of MCP channels. A calculation for maximum possible current density with a 1200 channel/cm2 MCP, placed over a cathode with 1200 uniformly functioning CNTs, would be ~1.46 kA/cm2, neglecting space charge limitations. Clearly this level of emission is far greater than what is needed for the electron lens application, but it does offer a highly comforting margin to account for sub-standard emitters and/or to allow the lesser challenge of building a cathode with fewer channels/cm2. A satisfactory goal for the electron lens application would be a controllable emission of 2-4 mA per channel in an ensemble of 800-1200 uniformly-functioning channels/cm2, and a cathode with overall area of about 1 cm2.

  6. Application of printed nanocrystalline diamond film for electron emission cathode

    International Nuclear Information System (INIS)

    Zhang Xiuxia; Wei Shuyi; Lei Chongmin; Wei Jie; Lu Bingheng; Ding Yucheng; Zhu Changchun

    2011-01-01

    The low-cost and large area screen-printed nano-diamond film (NDF) for electronic emission was fabricated. The edges and corners of nanocrystalline diamond are natural field-emitters. The nano-diamond paste for screen-printing was fabricated of mixing nano-graphite and other inorganic or organic vehicles. Through enough disperse in isopropyl alcohol by ultrasonic nano-diamond paste was screen-printed on the substrates to form NDF. SEM images showed that the surface morphology of NDF was improved, and the nano-diamond emitters were exposed from NDF through the special thermal-sintering technique and post-treatment process. The field emission characteristics of NDF were measured under all conditions with 10 -6 Pa pressure. The results indicated that the field emission stability and emission uniformity of NDF were improved through hydrogen plasma post-treatment process. The turn-on field decreased from 1.60 V/μm to 1.25 V/μm. The screen-printed NDF can be applied to the displays electronic emission cathode for low-cost outdoor in large area.

  7. Electronic emission produced by light projectiles at intermediate energies

    International Nuclear Information System (INIS)

    Bernardi, G.C.

    1989-01-01

    Two aspects of the electronic emission produced by light projectiles of intermediate energies have been studied experimentally. In the first place, measurements of angular distributions in the range from θ = 0 deg -50 deg induced by collisions of 50-200 keV H + incident on He have been realized. It was found that the double differential cross section of electron emission presents a structure focussed in the forward direction and which extends up to relatively large angles. Secondly, the dependence of the double differential cross section on the projectile charge was studied using H + and He 3 2+ projectiles of 50 and 100 keV/amu incident on He. Strong deviations from a constant scaling factor were found for increasing projectile charge. The double differential cross sections and the single differential cross sections as a function of the emission angle, and the ratios of the emissions induced by He 3 2+ and H + at equal incident projectile velocities are compared with the 'Continuum Distorted Wave-Eikonal Initial State' (CDW-EIS) approximation and the 'Classical Trajectory Monte Carlo' (CTMC) method. Both approximations, in which the potential of the projectile exercises a relevant role, reproduce the general aspects of the experimental results. An electron analyzer and the corresponding projectile beam line has been designed and installed; it is characterized by a series of properties which are particularly appropriate for the study of double differential electronic emission in gaseous as well as solid targets. The design permits to assure the conditions to obtain a well localized gaseous target and avoid instrumental distortions of the measured distributions. (Author) [es

  8. Ultrafast spectral interferometry of resonant secondary emission from quantum wells: From Rayleigh scattering to coherent emission from biexcitons

    DEFF Research Database (Denmark)

    Birkedal, Dan; Shah, Jagdeep; Pfeiffer, L. N.

    1999-01-01

    Recent investigations of secondary emission from quantum well excitons following ultrafast resonant excitation have demonstrated an intricate interplay of coherent Rayleigh scattering and incoherent luminescence. We have very recently demonstrated that it is possible to isolate and time resolve...... the coherent field associated with Rayleigh component using ultrafast spectral interferometry or Tadpole, thus, obtaining substantial and new information of the nature of resonant secondary emission. Our observation demonstrates that Rayleigh scattering from static disorder is inherently a non-ergodic process...... invalidating the use of current theories using ensemble averages to describe our observations. Furthermore, we report here a new and hitherto unknown coherent scattering mechanism involving the two-photon coherence associated with the biexciton transition. The process leaves an exciton behind taking up...

  9. Mean secondary electron yield of avalanche electrons in the channels of a microchannel plate detector

    International Nuclear Information System (INIS)

    Funsten, H.O.; Suszcynsky, D.M.; Harper, R.W.

    1996-01-01

    By modeling the statistical evolution of an avalanche created by 20 keV protons impacting the input surface of a z-stack microchannel plate (MCP) detector, the mean secondary electron yield γ C of avalanche electrons propagating through a MCP channel is measured to equal 1.37 for 760 V per MCP in the z stack. This value agrees with other studies that used MCP gain measurements to infer γ C . The technique described here to measure γ C is independent of gain saturation effects and simplifying assumptions used in the segmented dynode model, both of which can introduce errors when inferring γ C through gain measurements. copyright 1996 American Institute of Physics

  10. Field electron emission from pencil-drawn cold cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jiangtao; Yang, Bingjun; Liu, Xiahui; Yang, Juan; Yan, Xingbin, E-mail: xbyan@licp.cas.cn [Laboratory of Clean Energy Chemistry and Materials, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2016-05-09

    Field electron emitters with flat, curved, and linear profiles are fabricated on flexible copy papers by direct pencil-drawing method. This one-step method is free of many restricted conditions such as high-temperature, high vacuum, organic solvents, and multistep. The cold cathodes display good field emission performance and achieve high emission current density of 78 mA/cm{sup 2} at an electric field of 3.73 V/μm. The approach proposed here would bring a rapid, low-cost, and eco-friendly route to fabricate but not limited to flexible field emitter devices.

  11. Polarized electron cyclotron emission in the Tokapole II Tokamak

    International Nuclear Information System (INIS)

    Sengstacke, M.A.; Dexter, R.N.; Prager, S.C.

    1984-06-01

    To examine the effect of wall reflections we have measured the polarization of second harmonic cyclotron emission (at omega = 2 omega/sub ce/) in the Tokapole II tokamak both with and without a microwave absorber installed within the field of view of the receiving antenna. Indeed, the local elimination of wall reflections markedly enhances the polarization, as described in section II. Section III describes observations consistent with right-hand cutoff effects and an attempt to infer the electron temperature from cyclotron emission in an optically thin plasma

  12. Assessment of children environmental exposure to secondary emission of nickel, lead and copper

    Directory of Open Access Journals (Sweden)

    Jerzy Kwapuliński

    2012-12-01

    Full Text Available Introduction: Total rating impact of particulate matter in ground air layer recently takes on particular significance in evaluation of health risk. Indeed particulate matter is of interest to many research centres, however in so far PM related works the probability of adverse health impacts were not taken into account triggered with impact of additional presence of particulate matter from secondary dusting. The aim of the work: The work target was determination of secondary emission of Cu, Ni and Pb measured in streets with high traffic volume in many towns of Silesia Voivodeship. Materials and methods: Dust collected from the distance of about 200 m from busy roads in Upper Silesia cities was analyzed by the method of plasma spectrophotometry. The phenomenon of secondary dusting was defined by few coefficients of: secondary emission, enrichment, contamination and parameter of extra mass of a given metal in widespread air pollution. Results: It was concluded that absorbed dose of Cu and Pb changes depends on the area under study and decreases along with child’s age. Decrease of absorbed age depending doses is explained, so far, by significant increase of body mass in comparison to anatomically conditioned size of respiratory system.Also health risk estimated in relation to children residing in selected areas is diversified.. And it also decreases along with the children growing older. It appears, however, that health risk is determined by the volume of secondary PM emission and to children mostly threatened with Ni belong those who are particularly exposed to secondary emission of this metal. The secondary dusting is particularly dangerous for respiratory system and plays more important role than averaged content of this chemical in the environment.

  13. Laser-assisted electron emission from gated field-emitters

    CERN Document Server

    Ishizuka, H; Yokoo, K; Mimura, H; Shimawaki, H; Hosono, A

    2002-01-01

    Enhancement of electron emission by illumination of gated field-emitters was studied using a 100 mW cw YAG laser at a wavelength of 532 nm, intensities up to 10 sup 7 W/m sup 2 and mechanically chopped with a rise time of 4 mu s. When shining an array of 640 silicon emitters, the emission current responded quickly to on-off of the laser. The increase of the emission current was proportional to the basic emission current at low gate voltages, but it was saturated at approx 3 mu A as the basic current approached 100 mu A with the increase of gate voltage. The emission increase was proportional to the square root of laser power at low gate voltages and to the laser power at elevated gate voltages. For 1- and 3-tip silicon emitters, the rise and fall of the current due to on-off of the laser showed a significant time lag. The magnitude of emission increase was independent of the position of laser spot on the emitter base and reached 2 mu A at a basic current of 5 mu A without showing signs of saturation. The mech...

  14. Electron emission and plasma generation in a modulator electron gun using ferroelectric cathode

    International Nuclear Information System (INIS)

    Chen Shutao; Zheng Shuxin; Zhu Ziqiu; Dong Xianlin; Tang Chuanxiang

    2006-01-01

    Strong electron emission and dense plasma generation have been observed in a modulator electron gun with a Ba 0.67 Sr 0.33 TiO 3 ferroelectric cathode. Parameter of the modulator electron gun and lifetime of the ferroelectric cathode were investigated. It was shown that electron emission from Ba 0.67 Sr 0.33 TiO 3 cathode with a positive triggering pulse is a sort of plasma emission. Electrons were emitted by the co-effect of surface plasma and non-compensated negative polarization charges at the surface of the ferroelectric. The element analyses of the graphite collector after emission process was performed to show the ingredient of the plasma consist of Ba, Ti and Cu heavy cations of the ceramic compound and electrode. It was demonstrated the validity of the Child-Langmuir law by introducing the decrease of vacuum gap and increase of emission area caused by the expansion of the surface plasma

  15. Plasma-Sheath Instability in Hall Thrusters Due to Periodic Modulation of the Energy of Secondary Electrons in Cyclotron Motion

    International Nuclear Information System (INIS)

    Sydorenko, D.; Smolyakov, A.; Kaganovich, I.; Raitses, Y.

    2008-01-01

    Particle-in-cell simulation of Hall thruster plasmas reveals a plasma-sheath instability manifesting itself as a rearrangement of the plasma sheath near the thruster channel walls accompanied by a sudden change of many discharge parameters. The instability develops when the sheath current as a function of the sheath voltage is in the negative conductivity regime. The major part of the sheath current is produced by beams of secondary electrons counter-streaming between the walls. The negative conductivity is the result of nonlinear dependence of beam-induced secondary electron emission on the plasma potential. The intensity of such emission is defined by the beam energy. The energy of the beam in crossed axial electric and radial magnetic fields is a quasi-periodical function of the phase of cyclotron rotation, which depends on the radial profile of the potential and the thruster channel width. There is a discrete set of stability intervals determined by the final phase of the cyclotron rotation of secondary electrons. As a result, a small variation of the thruster channel width may result in abrupt changes of plasma parameters if the plasma state jumps from one stability interval to another

  16. Ultrafast interfeometric investigation of resonant secondary emission from quantum well excitons

    DEFF Research Database (Denmark)

    Birkedal, Dan; Shah, Jagdeep; Pfeiffer, L. N.

    1999-01-01

    Coherent Rayleigh scattering and incoherent luminescence comprise the secondary emission from quantum well exciton following ultrafast resonant excitation. We show that coherent Rayleigh scattering forms a time-dependent speckle pattern and isolate in a single speckle the Rayleigh component from...

  17. Radially localized measurements of superthermal electrons using oblique electron cyclotron emission

    International Nuclear Information System (INIS)

    Preische, S.; Efthimion, P.C.; Kaye, S.M.

    1996-05-01

    It is shown that radial localization of optically tin Electron Cyclotron Emission from superthermal electrons can be imposed by observation of emission upshifted from the thermal cyclotron resonance in the horizontal midplane of a tokamak. A new and unique diagnostic has been proposed and operated to make radially localized measurements of superthermal electrons during Lower Hybrid Current Drive on the PBX-M tokamak. The superthermal electron density profile as well as moments of the electron energy distribution as a function of radius are measured during Lower Hybrid Current Drive. The time evolution of these measurements after the Lower Hybrid power is turned off are given and the observed behavior reflects the collisional isotropization of the energy distribution and radial diffusion of the spatial profile

  18. Momentum distribution dependence of induced electron-cyclotron emission

    International Nuclear Information System (INIS)

    Ziebell, L.F.; Dillenburg, D.

    1983-01-01

    The dependence of the electron-cyclotron wave amplification in an inhomogeneous plasma slab on the electron momentum distribution is investigated. Two types of distributions are considered, both featuring a loss cone and a Maxwellian component. It is shown that the perpendicular emission at the fundamental frequency is in general greatly reduced by the presence of a Maxwellian component and situations occur in which a layer in the slab very effectively absorbs all the radiation amplified elsewhere. The transition from the pure loss cone to the pure Maxwellian case is accompanied by a peculiar behaviour of the dielectric tensor components, which may invalidate the geometrical optics approximation in the calculation of the emission and the commonly held belief that the real part of the refractive index is insensitive to the shape of the momentum distribution function. (Author) [pt

  19. Electron bunchlength measurement from analysis of fluctuations in spontaneous emission

    International Nuclear Information System (INIS)

    Catravas, P.; Leemans, W.P.; Wurtele, J.S.; Zolotorev, M.S.; Babzien, M.; Ben-Zvi, I.; Segalov, Z.; Wang, X.; Yakimenko, V.

    1999-01-01

    A statistical analysis of fluctuations in the spontaneous emission of a single bunch of electrons is shown to provide a new bunchlength diagnostic. This concept, originally proposed by Zolotorev and Stupakov [1], is based on the fact that shot noise from a finite bunch has a correlation length defined by the bunchlength, and therefore has a spiky spectrum. Single shot spectra of wiggler spontaneous emission have been measured at 632 nm from 44 MeV single electron bunches of 1 - 5 ps. The scaling of the spectral fluctuations with frequency resolution and the scaling of the spectral intensity distribution with bunchlength are studied. Bunchlength was extracted in a single shot measurement. Agreement was obtained between the experiment and a theoretical model, and with independent time integrated measurements. copyright 1999 American Institute of Physics

  20. Performance of a carbon nanotube field emission electron gun

    Science.gov (United States)

    Getty, Stephanie A.; King, Todd T.; Bis, Rachael A.; Jones, Hollis H.; Herrero, Federico; Lynch, Bernard A.; Roman, Patrick; Mahaffy, Paul

    2007-04-01

    A cold cathode field emission electron gun (e-gun) based on a patterned carbon nanotube (CNT) film has been fabricated for use in a miniaturized reflectron time-of-flight mass spectrometer (RTOF MS), with future applications in other charged particle spectrometers, and performance of the CNT e-gun has been evaluated. A thermionic electron gun has also been fabricated and evaluated in parallel and its performance is used as a benchmark in the evaluation of our CNT e-gun. Implications for future improvements and integration into the RTOF MS are discussed.

  1. Alcator C vertical viewing electron cyclotron emission diagnostic

    International Nuclear Information System (INIS)

    Kato, K.; Hutchinson, I.H.

    1986-03-01

    Electron cyclotron emission measured vertically through the center of a tokamak plasma yields detailed information about the electron velocity distribution. A diagnostic developed for this purpose on Alcator C tokamak uses specialized focusing optics to obtain a well collimated viewing chord, a compact viewing dump made of pyrex or Macor to reduce the effects of wall reflection and depolarization, and a rapid-scan polarizing Michelson interferometer - InSb detector system for the spectrum measurement; all constrained by the limited access and the compact size of Alcator C. Results of diffraction analysis are used to evaluate the theoretical performance of the optical system

  2. Photon emission by electrons and positrons traversing thin single crystal

    International Nuclear Information System (INIS)

    Ol'chak, A.S.

    1984-01-01

    Radiation emission by planar channeled particles (electrons, positrons) in a thin single crystal of thickness L is considered. It is shown that for L approximately πb/THETAsub(L) (b is the lattice constant, THETA sub(L) the Lindhard angle) besides the main spontaneous channeling maxima there exist auxiliary interference maxima, the positions of all the maxima depending on L. The dependence of the radiation spectral intensity on crystal thickness is discussed

  3. Electron Bernstein Wave Coupling and Emission Measurements on NSTX

    Czech Academy of Sciences Publication Activity Database

    Taylor, G.; Diem, S.J.; Caughman, J.; Efthimion, P.; Harvey, R.W.; LeBlanc, B.P.; Philips, C.K.; Preinhaelter, Josef; Urban, Jakub

    2006-01-01

    Roč. 51, č. 7 (2006), s. 177 ISSN 0003-0503. [Annual Meeting of the Division of Plasma Physics/48th./. Philadelphia, Pennsylvania , 30.10.2006-3.11.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Tokamaks * Electron Bernstein waves * Simulation * MAST * NSTX Subject RIV: BL - Plasma and Gas Discharge Physics http://www.aps.org/meet/DPP06/baps/all_DPP06.pdf

  4. Thermal Electron Bernstein Wave Emission Measurements on NST

    Czech Academy of Sciences Publication Activity Database

    Diem, S.J.; Taylor, G.; Efthimion, P.; LeBlanc, B.P.; Philips, C.K.; Caughman, J.; Wilgen, J.B.; Harvey, R.W.; Preinhaelter, Josef; Urban, Jakub

    2006-01-01

    Roč. 51, č. 7 (2006), s. 134 ISSN 0003-0503. [Annual Meeting of the Division of Plasma Physics/48th./. Philadelphia, Pennsylvania , 30.10.2006-3.11.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : Conversion * Emission * Tokamaks * Electron Bernstein waves * Simulation * MAST * NSTX Subject RIV: BL - Plasma and Gas Discharge Physics http://www.aps.org/meet/DPP06/baps/all_DPP06.pdf

  5. Electron field emission from undoped and doped DLC films

    International Nuclear Information System (INIS)

    Chakhovskoi, A G; Evtukh, A A; Felter, T E; Klyui, N I; Kudzinovsky, S Y; Litovchenko, V G; Litvin, Y M

    1999-01-01

    Electron field emission and electrical conductivity of undoped and nitrogen doped DLC films have been investigated. The films were grown by the PE CVD method from CH(sub 4):H(sub 2) and CH(sub 4):H(sub 2):N(sub 2) gas mixtures, respectively. By varying nitrogen content in the gas mixture over the range 0 to 45%, corresponding concentrations of 0 to 8% (atomic) could be achieved in the films. Three different gas pressures were used in the deposition chamber: 0.2, 0.6 and 0.8 Torr. Emission current measurements were performed at approximately 10(sup -6) Torr using the diode method with emitter-anode spacing set at 20(micro)m. The current - voltage characteristics of the Si field electron emission arrays covered with DLC films show that threshold voltage (V(sub th)) varies in a complex manner with nitrogen content. As a function of nitrogen content, V(sub th) initially increases rapidly, then decreases and finally increases again for the highest concentration. Corresponding Fowler-Nordheim (F-N) plots follow F-N tunneling over a wide range. The F-N plots were used for determination of the work function, threshold voltage, field enhancement factor and effective emission area. For a qualitative explanation of experimental results, we treat the DLC film as a diamond-like (sp(sup 3) bonded) matrix with graphite-like inclusions

  6. Electron emission during multicharged ion-surface interactions

    International Nuclear Information System (INIS)

    Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Meyer, F.W.; Zehner, D.M.

    1990-01-01

    Recent measurements of electron spectra for slow multicharged N ion-surface collisions are presented. The emphasis is on potential emission, i.e. the electron emission related to the neutralization of the ions. When using N ions that carry a K shell vacancy into the collision, characteristic K Auger electron emission from the projectiles is observed, as well as, for specific surfaces, target atom Auger transitions (resulting from vacancy transfer). Measurements of the intensity of these Auger transitions as a function of the time the ions spend above the surface can serve as a useful probe of the timescales characterizing the relevant neutralization processes. This technique is elucidated with the help of some computer simulations. It is shown that neutralization timescales required in the atomic ladder picture, in which neutralization takes place by resonant capture followed by purely intra-atomic Auger transitions, are too long to explain our experimental results. The introduction of additional neutralization/de-excitation mechanisms in the simulations leads to much better agreement with the experiments

  7. Electron emission and work function-Past, present and future

    International Nuclear Information System (INIS)

    Yamamoto, Shigehiko

    2005-01-01

    The history of electron emission is reviewed from a standpoint of the work function and the applications. For years, in the field of thermionic emission, a great deal of efforts have been devoted to search for low work function materials with a high melting temperature, while the reduction of the local change in time of the work function rather than the work function itself has been the main issue of field emission investigations. High brightness and long life are the central targets of the emission material investigations for the scientific instrument application, while high current density and low power consumption are the guiding principles for the display application. In both fields, field emission has recently become dominant in research and development. In all above cases, the main issue in the future research works will be to analyze the work function in atomic level and thereby to understand the mechanism of the work function reduction by atom adsorption, the change in time of the local work function leading to the current fluctuation, and the relationship between microscopic and macroscopic work functions. Our attempt is discussed, where the work function in atomic level is measured by utilizing the STM technique and it is made clear how far the work function in atomic level extends its influence over the neighboring sites. As a result, a simple relationship is established between microscopic and macroscopic work functions

  8. Atomic imaging using secondary electrons in a scanning transmission electron microscope: experimental observations and possible mechanisms.

    Science.gov (United States)

    Inada, H; Su, D; Egerton, R F; Konno, M; Wu, L; Ciston, J; Wall, J; Zhu, Y

    2011-06-01

    We report detailed investigation of high-resolution imaging using secondary electrons (SE) with a sub-nanometer probe in an aberration-corrected transmission electron microscope, Hitachi HD2700C. This instrument also allows us to acquire the corresponding annular dark-field (ADF) images both simultaneously and separately. We demonstrate that atomic SE imaging is achievable for a wide range of elements, from uranium to carbon. Using the ADF images as a reference, we studied the SE image intensity and contrast as functions of applied bias, atomic number, crystal tilt, and thickness to shed light on the origin of the unexpected ultrahigh resolution in SE imaging. We have also demonstrated that the SE signal is sensitive to the terminating species at a crystal surface. A possible mechanism for atomic-scale SE imaging is proposed. The ability to image both the surface and bulk of a sample at atomic-scale is unprecedented, and can have important applications in the field of electron microscopy and materials characterization. Copyright © 2010 Elsevier B.V. All rights reserved.

  9. Electron Emission by N6+ Ions Scattered at a Magnetized Iron Surface

    International Nuclear Information System (INIS)

    Solleder, B.; Lemell, C.; Burgdoerfer, J.; Tokesi, K.

    2006-01-01

    Complete text of publication follows. Magnetized materials are of considerable interest in the electronics industry (hard discs, spintronics, etc.). A detailed understanding of the properties of magnetized surfaces is therefore important to optimize technical applications. In the last decades, different experimental techniques have been developed to probe spin effects in magnetized materials. In this work the spin polarization of electrons emitted during the impact of N 6+ ions on a magnetized Fe surface is investigated. We study potential emission (PE) of electrons as well as secondary electron (SE) production and transport in the target with the help of Monte Carlo (MC) simulations. Spin dependence of electron transfer processes and of transport in the solid are included. Fig. 1 shows the results of our simulation for the energy distribution and spin polarization of emitted electrons in comparison with experimental data of Pfandzelter et al. [1] for the interaction of N 6+ ions with magnetized Fe. Electrons with energies higher than 200 eV are predominantly PE electrons, emitted close to the surface via autoionization (AI), Auger capture (AC) and Auger deexcitation (AD) channels. Low energy electrons are dominated by promoted, autoionized, and secondary electrons. The polarization of above surface electrons is determined by the high of the potential barrier separating projectile and target. At large distances, the barrier drops only slightly below the Fermi edge and enables transitions of electrons from this part of the band structure which has about 50% polarization. These electrons are transferred to high n states feeding promotion and AI processes between high lying states. Electrons emitted by these processes therefore reflect the polarization near the Fermi edge. Close to the surface, the barrier is low enough to allow for electron capture from the entire conduction band. K-Auger electrons are emitted in immediate vicinity of the surface and therefore mirror

  10. Electron-cyclotron maser emission during flares: emission in various modes and temporal variations

    International Nuclear Information System (INIS)

    Winglee, R.M.; Dulk, G.A.

    1986-01-01

    Absorption of radiation at the electron-cyclotron frequency, OMEGA sub e, generated by the electron-cyclotron maser instability was proposed as a possible mechanism for transporting energy and heating of the corona during flares. Radiation from the same instability but at harmonics of OMEGA sub e is believed to be the source of solar microwave spike bursts. The actual mode and frequency of the dominant emission from the maser instability is shown to be dependent on: (1) the plasma temperature, (2) the form of the energetic electron distribution, and (3) on the ratio of the plasma frequency omega sub p to OMEGA sub e. As a result, the emission along a flux tube can vary, with emission at harmonics being favored in regions where omega sub p/OMEGA sub e approx. equal to or greater than 1. Changes in the plasma density and temperature in the source region associated with the flare can also cause the characteristics of the emission to change in time

  11. Modeling of secondary emission processes in the negative ion based electrostatic accelerator of the International Thermonuclear Experimental Reactor

    Directory of Open Access Journals (Sweden)

    G. Fubiani

    2008-01-01

    Full Text Available The negative ion electrostatic accelerator for the neutral beam injector of the International Thermonuclear Experimental Reactor (ITER is designed to deliver a negative deuterium current of 40 A at 1 MeV. Inside the accelerator there are several types of interactions that may create secondary particles. The dominating process originates from the single and double stripping of the accelerated negative ion by collision with the residual molecular deuterium gas (≃29% losses. The resulting secondary particles (positive ions, neutrals, and electrons are accelerated and deflected by the electric and magnetic fields inside the accelerator and may induce more secondaries after a likely impact with the accelerator grids. This chain of reactions is responsible for a non-negligible heat load on the grids and must be understood in detail. In this paper, we will provide a comprehensive summary of the physics involved in the process of secondary emission in a typical ITER-like negative ion electrostatic accelerator together with a precise description of the numerical method and approximations involved. As an example, the multiaperture-multigrid accelerator concept will be discussed.

  12. Photo electron emission microscopy of polarity-patterned materials

    International Nuclear Information System (INIS)

    Yang, W-C; Rodriguez, B J; Gruverman, A; Nemanich, R J

    2005-01-01

    This study presents variable photon energy photo electron emission microscopy (PEEM) of polarity-patterned epitaxial GaN films, and ferroelectric LiNbO 3 (LNO) single crystals and PbZrTiO 3 (PZT) thin films. The photo electrons were excited with spontaneous emission from the tunable UV free electron laser (FEL) at Duke University. We report PEEM observation of polarity contrast and measurement of the photothreshold of each polar region of the materials. For a cleaned GaN film with laterally patterned Ga- and N-face polarities, we found a higher photoelectric yield from the N-face regions compared with the Ga-face regions. Through the photon energy dependent contrast in the PEEM images of the surfaces, we can deduce that the threshold of the N-face region is less than ∼4.9 eV while that of the Ga-face regions is greater than 6.3 eV. In both LNO and PZT, bright emission was detected from the negatively poled domains, indicating that the emission threshold of the negative domain is lower than that of the positive domain. For LNO, the measured photothreshold was ∼4.6 eV at the negative domain and ∼6.2 eV at the positive domain, while for PZT, the threshold of the negative domain was less than 4.3 eV. Moreover, PEEM observation of the PZT surface at elevated temperatures displayed that the domain contrast disappeared near the Curie temperature of ∼300 deg. C. The PEEM polarity contrast of the polar materials is discussed in terms of internal screening from free carriers and defects and the external screening due to adsorbed ions

  13. Photo electron emission microscopy of polarity-patterned materials

    Science.gov (United States)

    Yang, W.-C.; Rodriguez, B. J.; Gruverman, A.; Nemanich, R. J.

    2005-04-01

    This study presents variable photon energy photo electron emission microscopy (PEEM) of polarity-patterned epitaxial GaN films, and ferroelectric LiNbO3 (LNO) single crystals and PbZrTiO3 (PZT) thin films. The photo electrons were excited with spontaneous emission from the tunable UV free electron laser (FEL) at Duke University. We report PEEM observation of polarity contrast and measurement of the photothreshold of each polar region of the materials. For a cleaned GaN film with laterally patterned Ga- and N-face polarities, we found a higher photoelectric yield from the N-face regions compared with the Ga-face regions. Through the photon energy dependent contrast in the PEEM images of the surfaces, we can deduce that the threshold of the N-face region is less than ~4.9 eV while that of the Ga-face regions is greater than 6.3 eV. In both LNO and PZT, bright emission was detected from the negatively poled domains, indicating that the emission threshold of the negative domain is lower than that of the positive domain. For LNO, the measured photothreshold was ~4.6 eV at the negative domain and ~6.2 eV at the positive domain, while for PZT, the threshold of the negative domain was less than 4.3 eV. Moreover, PEEM observation of the PZT surface at elevated temperatures displayed that the domain contrast disappeared near the Curie temperature of ~300 °C. The PEEM polarity contrast of the polar materials is discussed in terms of internal screening from free carriers and defects and the external screening due to adsorbed ions.

  14. Study of luminous emissions associated to electron emissions in radiofrequency cavities; Etude des emissions lumineuses associees aux emissions electroniques dans les cavites hyperfrequences

    Energy Technology Data Exchange (ETDEWEB)

    Maissa, S

    1996-11-26

    This study investigates luminous emissions simultaneously to electron emissions and examines their features in order to better understand the field electron emission phenomenon. A RF cavity, operating at room temperature and in pulsed mode, joined to a sophisticated experimental apparatus has been especially developed. The electron and luminous emissions are investigated on cleaned or with metallic, graphitic and dielectric particles contaminated RF surfaces in order to study their influence on these phenomena. During the surface processing, unstable luminous spots glowing during one RF pulse are detected. Their apparition is promoted in the vicinity of the metallic particles or scratches. Two hypotheses could explain their origin: the presence of micro-plasmas associated to electronic explosive emission during processing or the thermal radiation of the melted metal during this emission. Stable luminous spots glowing during several RF pulses are also detected and appear to increase on RF surfaces contaminated with dielectric particles, leading to strong and explosive luminous emissions. Two interpretations are considered: the initiation of surface breakdowns on the dielectric particles or the heating by the RF field at temperatures sufficiently intense to provoke their thermal radiation then their explosion. Finally a superconducting cavity has been adapted to observe luminous spots, which differ from the former ones bu their star shape and could be associated to micro-plasmas, revealed by the starbursts observed on superconducting cavity walls. (author) 102 refs.

  15. Stochastic Coulomb interactions in space charge limited electron emission

    International Nuclear Information System (INIS)

    Nijkerk, M.D.; Kruit, P.

    2004-01-01

    Emission models that form the basis of self-consistent field computations make use of the approximation that emitted electrons form a smooth space charge jelly. In reality, electrons are discrete particles that are subject to statistical Coulomb interactions. A Monte Carlo simulation tool is used to evaluate the influence of discrete space charge effects on self-consistent calculations of cathode-ray tube optics. We find that interactions in the space charge cloud affect the electron trajectories such that the velocity distribution is Maxwellian, regardless of the current density. Interactions near the emitter effectively conserve the Maxwellian distribution. The surprising result is that the width of the distribution of transversal velocities does not change. The distribution of longitudinal velocities does broaden, as expected from existing theories

  16. Emission spectra of dimethoxybenzenes by controlled electron impact

    International Nuclear Information System (INIS)

    Ogawa, Teiichiro; Imasaka, Totaro; Toyoda, Minoru; Tsuji, Masaharu; Ishibashi, Nobuhiko

    1975-01-01

    The emission spectra of o-, m-, and p-dimethoxybenzenes under controlled electron impact excitation (200 eV) were measured in the 220 - 450 nm region at very low pressures. The photoemissions of the excited parent species and such fragment species as H, CH, CO, and CO + were observed and assigned. The relative intensities of the photoemissions of the parent species were compared with those of the fluorescence spectra (photoexcitation) in an n-hexane solution. The excited parent species, H, and CH were concluded to be produced in one-electron processes; however, the CO + species were assumed to be produced in both one- and two-electron processes, and the relative contributions are evaluated. It was concluded that the rate of the predissociation of o-dimethoxybenzene was faster than those of the other two isomers, and the observed characteristics of o-dimethoxybenzene had something to do with this faster rate. (auth.)

  17. Suppression secondary electrons from target surface under pulsed ion beams bombardment

    International Nuclear Information System (INIS)

    Yang Zhen; Peng Yufei; Long Jidong; Lan Chaohui; Dong Pan; Shi Jinshui

    2012-01-01

    The producing mechanism of secondary electrons from target surface under ion beams bombardment is discussed. Several methods to suppress the secondary electrons in special vacuum devices and their advantages and disadvantages are introduced. The ways of using self-bias and curved surface target are proposed and verified in the experiment. The results show that the secondary electrons can be effectively suppressed when the self-bias is larger than 80 V. The secondary electron yield decreases by using curved surface target instead of flat target. The secondary electron yield calculated from the experimental data is about 0.67, which is slightly larger than the value (0.58) from the literature due to the impurities of the ion beam and target surface. The effect of suppressing the electron countercurrent by the self-bias method is analyzed. The result shows that the self-bias method can not only suppress the secondary electrons from target surface under ion beams bombardment, but also suppress the electron countercurrent resulting from the instability of the pulsed power source. (authors)

  18. Diagnosis of mildly relativistic electron velocity distributions by electron cyclotron emission in the Alcator C tokamak

    International Nuclear Information System (INIS)

    Kato, K.

    1986-09-01

    Mildly relativistic electron velocity distributions are diagnosed from measurements of the first few electron cyclotron emission harmonics in the Alcator C tokamak. The approach employs a vertical viewing chord through the center of the tokamak plasma terminating at a compact, high-performance viewing dump. The cyclotron emission spectra obtained in this way are dominated by frequency downshifts due to the relativistic mass increase, which discriminates the electrons by their total energy. In this way a one-to-one correspondence between the energy and the emission frequency is accomplished in the absence of harmonic superpositions. The distribution, described by f/sub p/, the line-averaged phase space density, and Λ, the anisotropy factor, is determined from the ratio of the optically thin harmonics or polarizations. Diagnosis of spectra in the second and the third harmonic range of frequencies obtained during lower hybrid heating, current drive, and low density ohmic discharges are carried out, using different methods depending on the degree of harmonic superposition present in the spectrum and the availability of more than one ratio measurement. Discussions of transient phenomena, the radiation temperature measurement from the optically thick first harmonic, and the measurements compared to the angular hard x-ray diagnostic results illuminate the capabilities of the vertically viewing electron cyclotron emission diagnostic

  19. New Secondary Batteries Using Electronically Conductive Polymer Cathodes

    Science.gov (United States)

    Martin, Charles R.; White, Ralph E.

    1991-01-01

    A Li/Polypyrrole secondary battery was designed and built, and the effect of controlling the morphology of the polymer on enhancement of counterion diffusion in the polymer phase was explored. The experimental work was done at Colorado State University, while the mathematical modeling of the battery was done at Texas A and M University. Manuscripts and publications resulting from the project are listed.

  20. Effect of electron emission on the charge and shielding of a dust grain in a plasma: A continuum theory

    International Nuclear Information System (INIS)

    D'yachkov, L. G.; Khrapak, A. G.; Khrapak, S. A.

    2008-01-01

    The continuum approximation is used to analyze the effect of electron emission from the surface of a spherical dust grain immersed in a plasma on the grain charge by assuming negligible ionization and recombination in the disturbed plasma region around the grain. A parameter is introduced that quantifies the emission intensity regardless of the emission mechanism (secondary, photoelectric, or thermionic emission). An analytical expression for the grain charge Z d is derived, and a criterion for change in the charge sign is obtained. The case of thermionic emission is examined in some detail. It is shown that the long-distance asymptotic behavior of the grain potential follows the Coulomb law with a negative effective charge Z eff , regardless of the sign of Z d . Thus, the potential changes sign and has a minimum if Z d > 0, which implies that attraction is possible between positively charged dust grains

  1. Low Secondary Electron Yield Carbon Coatings for Electron-cloud Mitigation in Modern Particle Accelerators

    CERN Document Server

    Yin Vallgren, Christina; Calatroni, Sergio; Chiggiato, Paolo; Costa Pinto, Pedro; Marques, Hugo; Neupert, Holger; Taborelli, Mauro; Vollenberg, Wilhelmus; Wevers, Ivo; Yaqub, Kashif

    2010-01-01

    Electron-cloud is one of the main limitations for particle accelerators with positively charged beams of high intensity and short bunch spacing, as the SPS at CERN. The Secondary Electron Yield (SEY) of the inner surface of the vacuum chamber is the main parameter governing the phenomenon. The effect could be eliminated by coating the vacuum chambers with a material of low SEY, which does not require bake-out and is robust against air exposure. For such a purpose amorphous carbon (a-C) coatings were produced by magnetron sputtering of graphite targets. They exhibit maximum SEY between 0.95 and 1.05 after air transfer to the measuring instrument. After 1 month of air exposure the SEY rises by 10 - 20 % of the initial values. Storage in desiccator or by packaging in Al foil makes this increase negligible. The coatings have a similar X-ray photoelectron spectroscopy (XPS) C1s spectrum for a large set of deposition parameters and exhibit an enlarged linewidth compared to HOPG graphite. The static outgassing witho...

  2. Design of Pixellated CMOS Photon Detector for Secondary Electron Detection in the Scanning Electron Microscope

    Directory of Open Access Journals (Sweden)

    Joon Huang Chuah

    2011-01-01

    Full Text Available This paper presents a novel method of detecting secondary electrons generated in the scanning electron microscope (SEM. The method suggests that the photomultiplier tube (PMT, traditionally used in the Everhart-Thornley (ET detector, is to be replaced with a configurable multipixel solid-state photon detector offering the advantages of smaller dimension, lower supply voltage and power requirements, and potentially cheaper product cost. The design of the proposed detector has been implemented using a standard 0.35 μm CMOS technology with optical enhancement. This microchip comprises main circuit constituents of an array of photodiodes connecting to respective noise-optimised transimpedance amplifiers (TIAs, a selector-combiner (SC circuit, and a postamplifier (PA. The design possesses the capability of detecting photons with low input optical power in the range of 1 nW with 100 μm × 100 μm sized photodiodes and achieves a total amplification of 180 dBΩ at the output.

  3. Evaluation of secondary electron filter for removing contaminant electrons from high-energy 6 MV x-ray beam

    International Nuclear Information System (INIS)

    Kumagai, Kozo

    1988-01-01

    When using high energy X-rays, the dose increases at the skin surface and build-up region of beam contamination of secondary electrons coming out from the inner surface of the lineac head. At our radiotherapy department, many cases of external otitis from severe skin reactions, particularly resulting from whole brain irradiation of primary and metastatic brain tumors with a 6 MV X-ray lineac, have been encountered. An investigation was made of the physical aspects of a 6 MV X-ray beam using three electron filters, lead lucite, lead glass and lucite to remove secondary electrons. Transparent materials for filters should be preferable for locating the light field. The following results were obtained: 1) For removing secondary electrons, a lead lucite filter was found best. 2) The lead lucite filter proved most effective for removing secondary electrons from the area of treatment. It reduced the dose of irradiation to the skin surface and build-up region, and furthermore improved the depth dose relative to that without filters. 3) From a clinical standpoint, skin reactions such as external otitis remarkably decreased using a lead lucite filter. 4) It thus appears necessary to use a high energy X-ray with newly designed filters to reduce beam contamination of secondary electrons. (author)

  4. Pitch Angle Scattering of Energetic Electrons by Plasmaspheric Hiss Emissions

    Science.gov (United States)

    Tobita, M.; Omura, Y.; Summers, D.

    2017-12-01

    We study scattering of energetic electrons in pitch angles and kinetic energies through their resonance with plasmaspheric hiss emissions consisting of many coherent discrete whistler-mode wave packets with rising and falling frequencies [1,2,3]. Using test particle simulations, we evaluate the efficiency of scattering, which depends on the inhomogeneity ratio S of whistler mode wave-particle interaction [4]. The value of S is determined by the wave amplitude, frequency sweep rate, and the gradient of the background magnetic field. We first modulate those parameters and observe variations of pitch angles and kinetic energies of electrons with a single wave under various S values so as to obtain basic understanding. We then include many waves into the system to simulate plasmaspheric hiss emissions. As the wave packets propagate away from the magnetic equator, the nonlinear trapping potential at the resonance velocity is deformed, making a channel of gyrophase for untrapped electrons to cross the resonance velocity, and causing modulations in their pitch angles and kinetic energies. We find efficient scattering of pitch angles and kinetic energies because of coherent nonlinear wave-particle interaction, resulting in electron precipitations into the polar atmosphere. We compare the results with the bounce averaged pitch angle diffusion coefficient based on quasi-linear theory, and show that the nonlinear wave model with many coherent packets can cause scattering of resonant electrons much faster than the quasi-linear diffusion process. [1] Summers, D., Omura, Y., Nakamura, S., and C. A. Kletzing (2014), Fine structure of plasmaspheric hiss, J. Geophys. Res., 119, 9134-9149. [2] Omura, Y., Y. Miyashita, M. Yoshikawa, D. Summers, M. Hikishima, Y. Ebihara, and Y. Kubota (2015), Formation process of relativistic electron flux through interaction with chorus emissions in the Earth's inner magnetosphere, J. Geophys. Res. Space Physics, 120, 9545-9562. [3] Nakamura, S., Y

  5. A national day with near zero emissions and its effect on primary and secondary pollutants

    Science.gov (United States)

    Levy, Ilan

    2013-10-01

    Traffic related air pollution is a major health concern in many countries. The potential costs and benefits of different abatement policies are usually estimated by either models, case studies or previously implemented intervention measures. Such estimations have, however, limited ability to predict the effect of a reduction in primary pollutants' emissions on secondary pollutants such as ozone, because of the nonlinear nature of the photochemical reactions. This study examines the short term effects of a drastic change in emissions on a national scale during the Jewish holiday of Day of Atonement (DA) in Israel. During the holiday nearly all anthropogenic emission sources are ceased for a period of 25 h, including all vehicles, commercial, industrial and recreational activities. DAs during the 15 years period of 1998-2012 are analyzed at three sites with respect to primary and secondary air pollutants, and in greater details for 2001. A dramatic decrease in primary pollutants emissions (83-98% in NO) causes an 8 ppbv increase in ozone at the urban core. Downwind (27 km), ozone decreases by only 5 ppbv. Nighttime O3 is shown to increase to 20 ppbv at the urban sites and 30 ppbv downwind. In spite of the striking reduction in emissions, changes in ozone are not greater than what is reported in the literature about less significant events like the ozone weekend effect. Changes in ambient pollution levels observed during DA provide some indication to the possible outcomes of a major change in anthropogenic emissions. These may be considered as the best case scenario for emissions reduction intervention measures and thus aid policy makers in evaluating potential benefits of such measures.

  6. Self-sputtering runaway in high power impulse magnetron sputtering: The role of secondary electrons and multiply charged metal ions

    International Nuclear Information System (INIS)

    Anders, Andre

    2008-01-01

    Self-sputtering runaway in high power impulse magnetron sputtering is closely related to the appearance of multiply charged ions. This conclusion is based on the properties of potential emission of secondary electrons and energy balance considerations. The effect is especially strong for materials whose sputtering yield is marginally greater than unity. The absolute deposition rate increases ∼Q 1/2 , whereas the rate normalized to the average power decreases ∼Q -1/2 , with Q being the mean ion charge state number

  7. Electron temperature fluctuation in the HT-7 tokamak plasma observed by electron cyclotron emission imaging

    International Nuclear Information System (INIS)

    Xiao-Yuan, Xu; Jun, Wang; Yi, Yu; Yi-Zhi, Wen; Chang-Xuan, Yu; Wan-Dong, Liu; Bao-Nian, Wan; Xiang, Gao; Luhmann, N. C.; Domier, C. W.; Wang, Jian; Xia, Z. G.; Shen, Zuowei

    2009-01-01

    The fluctuation of the electron temperature has been measured by using the electron cyclotron emission imaging in the Hefei Tokamak-7 (HT-7) plasma. The electron temperature fluctuation with a broadband spectrum shows that it propagates in the electron diamagnetic drift direction, and the mean poloidal wave-number k-bar θ is calculated to be about 1.58 cm −1 , or k-bar θρ s thickapprox 0.34. It indicates that the fluctuation should come from the electron drift wave turbulence. The linear global scaling of the electron temperature fluctuation with the gradient of electron temperature is consistent with the mixing length scale qualitatively. Evolution of spectrum of the fluctuation during the sawtooth oscillation phases is investigated, and the fluctuation is found to increase with the gradient of electron temperature increasing during most phases of the sawtooth oscillation. The results indicate that the electron temperature gradient is probably the driver of the fluctuation enhancement. The steady heat flux driven by electron temperature fluctuation is estimated and compared with the results from power balance estimation. (fluids, plasmas and electric discharges)

  8. Electron emission from laser irradiating target normal sheath acceleration (TNSA)

    Czech Academy of Sciences Publication Activity Database

    Torrisi, L.; Cutroneo, Mariapompea

    2016-01-01

    Roč. 171, 9-10 (2016), s. 754-765 ISSN 1042-0150. [12th Workshop on European Collaboration for Higher Education and Research in Nuclear Engineering and Radiological Protection. Bologna, Catania, Milan, 30.05.2016-01.06.2016] R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk LM2015056 Institutional support: RVO:61389005 Keywords : electron emission from plasma * TNSA * TOF * SiC * plastic scintillator * Thomson parabola spectrometer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.443, year: 2016

  9. Method of electron emission control in RF guns

    International Nuclear Information System (INIS)

    Khodak, I.V.; Kushnir, V.A.

    2001-01-01

    The electron emission control method for a RF gun is considered.According to the main idea of the method,the additional resonance system is created in a cathode region where the RF field strength could be varied using the external pulse equipment. The additional resonance system is composed of a coaxial cavity coupled with a RF gun cylindrical cavity via an axial hole. Computed results of radiofrequency and electrodynamic performances of such a two-cavity system and results of the RF gun model pilot study are presented in. Results of particle dynamics simulation are described

  10. Method of electron emission control in RF guns

    CERN Document Server

    Khodak, I V

    2001-01-01

    The electron emission control method for a RF gun is considered.According to the main idea of the method,the additional resonance system is created in a cathode region where the RF field strength could be varied using the external pulse equipment. The additional resonance system is composed of a coaxial cavity coupled with a RF gun cylindrical cavity via an axial hole. Computed results of radiofrequency and electrodynamic performances of such a two-cavity system and results of the RF gun model pilot study are presented in. Results of particle dynamics simulation are described.

  11. SLIM (secondary emission monitor for low interception monitoring) an innovative non-destructive beam monitor for the extraction lines of a hadrontherapy centre

    International Nuclear Information System (INIS)

    Gibson, P.N.; Holzwarth, U.; Abbas, K.

    2005-01-01

    Real time monitoring of hadron therapy beam intensity and profile is a critical issue for the optimisation of dose delivery to carcinogenic tissue, patient safety and operation of the accelerator complex. For this purpose an innovative beam monitor, SLIM (Secondary electron emission for Low Interception Monitoring) is being developed in the framework of the EC-funded SUCIMA (Silicon Ultra-fast Cameras for electrons and gamma sources In Medical Application) project. The detector system is based on the secondary emission of electrons by a non-perturbative, sub-micron thick Al foil placed directly in the extracted beam path. The secondary electrons, accelerated by an electrostatic focusing system, are detected by a monolithic silicon position-sensitive sensor, which provides the beam intensity and its position with a precision of 1 mm at 10 kHz frame rate. The results of the laboratory tests of the first system prototype with thermoionic electrons emitted from a hot Tungsten wire are presented together with the measurements performed on a low intensity hadron beam at the Cyclotron of the Joint Research Centre in Ispra. (author)

  12. A solvated electron lithium electrode for secondary batteries

    Science.gov (United States)

    Sammells, A. F.; Semkow, K. W.

    1986-09-01

    Attention is given to a novel method for the achievement of high electro-chemical reversibility in Li-based nonaqueous cells, using a liquid negative electrode that consists of Li dissolved in liquid ammonia as a solvated electron Li electrode. The containment of this liquid negative active material from direct contact to a liquid nonaqueous electrolyte in the positive electrode compartment was realized through the use of a Li-intercalated, electronically conducting ceramic membrane.

  13. Polarization of electron cyclotron emission spectra in LHD

    International Nuclear Information System (INIS)

    Vries, P.C. de; Nagayama, Y.; Kawahata, K.; Inagaki, S.; Sasao, H.; Nagasaki, K.

    1999-07-01

    Electron cyclotron emission (ECE) can be used to determine the electron temperature profile in magnetized plasmas. The complex structure of the magnetic field configuration in the Large Helical Device (LHD), which has a large shear, complicates the analysis of the ECE spectrum. In a sheared magnetic field the propagation of X and O-mode polarization through the plasma are coupled, causing mode conversion and polarization rotation. Mode scrambling is also caused by wall reflections. In this report, this mode conversion in LHD is numerically analyzed. It was found that at low density mode conversion scrambles the ECE spectra. However, at higher density (n eo > 1.0·10 19 m -3 ) the polarization mode is found to rotate with the sheared magnetic field, yielding only a negligible mode conversion. Wall reflections are found to depolarize the ECE spectrum. Notwithstanding the LHD magnetic configuration, it is shown that temperature profiles could be revealed from the ECE spectra. (author)

  14. Angular dependence of secondary ion emission from silicon bombarded with inert gas ions

    International Nuclear Information System (INIS)

    Wittmaack, K.

    1984-01-01

    The emission of positive and negative, atomic and molecular secondary ions sputtered from silicon has been studied under ultrahigh vacuum conditions. The sample was bombarded with 2-12 keV Ar + and Xe + ions at angles of incidence between 0 0 and 60 0 to the surface normal. The angular dependence of the secondary ion intensity as well as the energy spectra of Si + and Si - were found to differ significantly. The effect is attributed mostly do differences in the rate of neutralization. The stability of molecular ions appears to be independent of the charge state. Supporting evidence is provided for the idea that multiply charged secondary ions are due to Auger de-excitation of sputtered atoms in vacuum. (orig.)

  15. Primary emissions and secondary aerosol production potential from woodstoves for residential heating: Influence of the stove technology and combustion efficiency

    Science.gov (United States)

    Bertrand, Amelie; Stefenelli, Giulia; Bruns, Emily A.; Pieber, Simone M.; Temime-Roussel, Brice; Slowik, Jay G.; Prévôt, André S. H.; Wortham, Henri; El Haddad, Imad; Marchand, Nicolas

    2017-11-01

    To reduce the influence of biomass burning on air quality, consumers are encouraged to replace their old woodstove with new and cleaner appliances. While their primary emissions have been extensively investigated, the impact of atmospheric aging on these emissions, including secondary organic aerosol (SOA) formation, remains unknown. Here, using an atmospheric smog chamber, we aim at understanding the chemical nature and quantify the emission factors of the primary organic aerosols (POA) from three types of appliances for residential heating, and to assess the influence of aging thereon. Two, old and modern, logwood stoves and one pellet burner were operated under typical conditions. Emissions from an entire burning cycle (past the start-up operation) were injected, including the smoldering and flaming phases, resulting in highly variable emission factors. The stoves emitted a significant fraction of POA (up to 80%) and black carbon. After ageing, the total mass concentration of organic aerosol (OA) increased on average by a factor of 5. For the pellet stove, flaming conditions were maintained throughout the combustion. The aerosol was dominated by black carbon (over 90% of the primary emission) and amounted to the same quantity of primary aerosol emitted by the old logwood stove. However, after ageing, the OA mass was increased by a factor of 1.7 only, thus rendering OA emissions by the pellet stove almost negligible compared to the other two stoves tested. Therefore, the pellet stove was the most reliable and least polluting appliance out of the three stoves tested. The spectral signatures of the POA and aged emissions by a High Resolution - Time of Flight - Aerosol Mass Spectrometer (Electron Ionization (EI) at 70 eV) were also investigated. The m/z 44 (CO2+) and high molecular weight fragments (m/z 115 (C9H7+), 137 (C8H9O2+), 167 (C9H11O3+) and 181 (C9H9O4+, C14H13+)) correlate with the modified combustion efficiency (MCE) allowing us to discriminate further

  16. Search for Fermi shuttle mechanisms in electron emission from atomic collision sequences

    International Nuclear Information System (INIS)

    Suarez, S.; Jung, M.; Rothard, H.; Schosnig, M.; Maier, R.; Clouvas, A.; Groeneveld, K.O.

    1994-01-01

    In electron spectra induced by slow heavy ion bombardment of solids a high energy tail can be observed, which is suggested to be explained by multiple collision sequences. In order to find those multiple collision effects like the ''Fermi shuttle'' acceleration mechanism we measured doubly differential electron emission cross sections for H + (33.5-700 keV) impact on different targets (He, Ne, C and Au) as a function of projectile energy and electron emission angle. We observed a surprising target dependence of the electron emission within the range of electron energies close to that of the binary encounter electrons for all observed angles of emission. (orig.)

  17. Secondary Emission From Synthetic Opal Infiltrated by Colloidal Gold and Glycine

    International Nuclear Information System (INIS)

    Dovbeshko, G.I.; Fesenko, O.M.; Boyko, V.V.; Romanyuk, V.R.; Gorelik, V.S.; Moiseyenko, V.N.; Sobolev, V.B.; Shvalagin, V.V.

    2012-01-01

    A comparison of the secondary emission (photoluminescence) and Bragg reflection spectra of photonic crystals (PC), namely, synthetic opals, opals infiltrated by colloidal gold, glycine, and a complex of colloidal gold with glycine is performed. The infiltration of colloidal gold and a complex of colloidal gold with glycine into the pores of PC causes a short-wavelength shift (about 5-15 nm) of the Bragg reflection and increases the intensity of this band by 1.5-3 times. In photoluminescence, the infiltration of PC by colloidal gold and colloidal gold with glycine suppresses the PC emission band near 375-450 nm and enhances the shoulder of the stop-zone band of PC in the region of 470-510 nm. The shape of the observed PC emission band connected with defects in synthetic opal is determined by the type of infiltrates and the excitation wavelength. Possible mechanisms of the effects are discussed.

  18. Electron emission from MOS electron emitters with clean and cesium covered gold surface

    DEFF Research Database (Denmark)

    Nielsen, Gunver; Thomsen, Lasse Bjørchmar; Johansson, Martin

    2009-01-01

    MOS (metal-oxide-semiconductor) electron emitters consisting of a Si substrate, a SiO2 tunnel barrier and a Ti (1 nm)/Au(7 nm) top-electrode, with an active area of 1 cm(2) have been produced and studied with surface science techniques under UHV (ultra high vacuum) conditions and their emission...... characteristics have been investigated. It is known, that deposition of an alkali metal on the emitting surface lowers the work function and increases the emission efficiency. For increasing Cs coverages the surface has been characterized by X-ray Photoelectron Spectroscopy (XPS), Ion Scattering Spectroscopy (ISS...

  19. Sheath and heat flow of a two-electron-temperature plasma in the presence of electron emission

    International Nuclear Information System (INIS)

    Sato, Kunihiro; Miyawaki, Fujio

    1992-01-01

    The electrostatic sheath and the heat flow of a two-electron-temperature plasma in the presence of electron emission are investigated analytically. It is shown that the energy flux is markedly enhanced to a value near the electron free-flow energy flux as a result of considerable reduction of the sheath potential due to electron emission if the fraction of hot electrons at the sheath edge is much smaller than one. If the hot- to cold-electron temperature ratio is of the order of ten and the hot electron density is comparable to the cold electron density, the action of the sheath as a thermal insulator is improved as a result of suppression of electron emission due to the space-charge effect of hot electrons. (author)

  20. Formula for average energy required to produce a secondary electron in an insulator

    International Nuclear Information System (INIS)

    Xie Ai-Gen; Zhan Yu; Gao Zhi-Yong; Wu Hong-Yan

    2013-01-01

    Based on a simple classical model specifying that the primary electrons interact with the electrons of a lattice through the Coulomb force and a conclusion that the lattice scattering can be ignored, the formula for the average energy required to produce a secondary electron (in) is obtained. On the basis of the energy band of an insulator and the formula for in, the formula for the average energy required to produce a secondary electron in an insulator (in i ) is deduced as a function of the width of the forbidden band (E g ) and electron affinity χ. Experimental values and the in i values calculated with the formula are compared, and the results validate the theory that explains the relationships among E g , χ, and in i and suggest that the formula for in i is universal on the condition that the primary electrons at any energy hit the insulator. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  1. Electron beam injection during active experiments. 1. Electromagnetic wave emissions

    International Nuclear Information System (INIS)

    Winglee, R.M.; Kellogg, P.J.

    1990-01-01

    During the active injection of an electron beam, a broad spectrum of waves is generated. In this paper examples of spectra from the recent Echo 7 experiment are presented. These results show that the characteristics of the emissions can change substantially with altitude. Two-dimensional (three velocity) relativistic electromagnetic particle simulations are used to investigate the changes in the plasma conditions required to account for the observed spectral variations. It is shown that many of these variations can be accounted for by assuming that the ratio of the electron plasma frequency ω pe to cyclotron frequency Ω e is less than unity at the lower altitudes of about 200 km and near or above unity at apogee of about 300 km. In the former case, whistlers with a cutoff at ω pe , lower hybrid and plasma waves are driven by the parallel beam energy while electromagnetic fundamental z mode and second harmonic x mode and electrostatic upper hybrid waves are driven by the perpendicular beam energy through the master instability. E x B drifts driven by perpendicular electric fields associated with the beam-plasma interaction can also be important in generating maser emission, particularly for field-aligned injection where there is no intrinsic perpendicular beam energy. The power in the electrostatic waves is a few percent of the beam energy and that in the electromagnetic waves a few tenths of a percent. In the latter case, where ω pe /Ω e increases above unity, emission in the fundamental z mode and second harmonic x mode become suppressed

  2. High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

    International Nuclear Information System (INIS)

    Hojati-Talemi, Pejman; Gibson, Mark A.; East, Daniel; Simon, George P.

    2011-01-01

    We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

  3. High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

    Energy Technology Data Exchange (ETDEWEB)

    Hojati-Talemi, Pejman [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia); Mawson Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Gibson, Mark A. [Process Science and Engineering, Commonwealth Scientific and Industrial Research Organisation, Clayton, Vic 3168 (Australia); East, Daniel; Simon, George P. [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia)

    2011-11-07

    We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

  4. Electron Processing at 50 eV of Terphenylthiol Self-Assembled Monolayers: Contributions of Primary and Secondary Electrons.

    Science.gov (United States)

    Houplin, Justine; Dablemont, Céline; Sala, Leo; Lafosse, Anne; Amiaud, Lionel

    2015-12-22

    Aromatic self-assembled monolayers (SAMs) can serve as platforms for development of supramolecular assemblies driven by surface templates. For many applications, electron processing is used to locally reinforce the layer. To achieve better control of the irradiation step, chemical transformations induced by electron impact at 50 eV of terphenylthiol SAMs are studied, with these SAMs serving as model aromatic SAMs. High-resolution electron energy loss spectroscopy (HREELS) and electron-stimulated desorption (ESD) of neutral fragment measurements are combined to investigate electron-induced chemical transformation of the layer. The decrease of the CH stretching HREELS signature is mainly attributed to dehydrogenation, without a noticeable hybridization change of the hydrogenated carbon centers. Its evolution as a function of the irradiation dose gives an estimate of the effective hydrogen content loss cross-section, σ = 2.7-4.7 × 10(-17) cm(2). Electron impact ionization is the major primary mechanism involved, with the impact electronic excitation contributing only marginally. Therefore, special attention is given to the contribution of the low-energy secondary electrons to the induced chemistry. The effective cross-section related to dissociative secondary electron attachment at 6 eV is estimated to be 1 order of magnitude smaller. The 1 eV electrons do not induce significant chemical modification for a 2.5 mC cm(-2) dose, excluding their contribution.

  5. On the Emission of Electrons from Solid H_2 and D_2 by Bombardment with 1-3 keV Electrons up to Very Large Angles of Incidence

    DEFF Research Database (Denmark)

    Schou, Jørgen; Sørensen, H.

    1982-01-01

    at the largest angles. The results agree well with the existing qualitative tendencies described in the literature. The variation with the angle of incidence shows a fair agreement with an estimate based on data for the angular distribution of electrons ejected from ionized hydrogen molecules. In addition......Electron emission, i.e. electron reflection (ER) and secondary electron emission (SEE), was studied for solid H2 and D2 for oblique incidence of 1-3 keV electrons up to an angle of incidence θ of 83°. The ER coefficient η was small at low angles, and rose rapidly with increasing θ above 60......, an ionization cascade treatment leads to an expression for the behavior of the yield of those secondary electrons that are generated directly by the primaries. The agreement with experimental data is good...

  6. Proceedings of eighth joint workshop on electron cyclotron emission and electron cyclotron resonance heating. Vol. 1

    International Nuclear Information System (INIS)

    1993-03-01

    The theory of electron cyclotron resonance phenomena is highly developed. The main theoretical tools are well established, generally accepted and able to give a satisfactory description of the main results obtained in electron cyclotron emission, absorption and current drive experiments. In this workshop some advanced theoretical and numerical tools have been presented (e.g., 3-D Fokker-Planck codes, treatment of the r.f. beam as a whole, description of non-linear and finite-beam effects) together with the proposal for new scenarios for ECE and ECA measurements (e.g., for diagnosing suprathermal populations and their radial transport). (orig.)

  7. Proceedings of eighth joint workshop on electron cyclotron emission and electron cyclotron resonance heating. Vol. 2

    International Nuclear Information System (INIS)

    1993-03-01

    The theory of electron cyclotron resonance phenomena is highly developed. The main theoretical tools are well established, generally accepted and able to give a satisfactory description of the main results obtained in electron cyclotron emission, absorption and current drive experiments. In this workshop some advanced theoretical and numerical tools have been presented (e.g., 3-D Fokker-Planck codes, treatment of the r.f. beam as a whole, description of non-linear and finite-beam effects) together with the proposal for new scenarios for ECE and ECA measurements (e.g., for diagnosing suprathermal populations and their radial transport). (orig.)

  8. The calculation of proton and secondary electron stopping powers in liquid water

    International Nuclear Information System (INIS)

    Marouane, Abdelhak; Inchaouh, Jamal; Ouaskit, Said; Fathi, Ahmed

    2012-01-01

    The stopping power of energetic protons in liquid water has been calculated using a new model based on different theoretical and semi-empirical approaches. In this model, we consider the relativistic corrections along with the electronic and nuclear stopping power. The present work accounts for the different interactions made with electrons and nuclei inside the target. Interactions of the incident particle with the target's electrons dominate in the high energy regime; in the low energy regime, the interactions of the projectile with the target nuclei contribute importantly and are included in the calculation. We also compute the stopping cross sections and the stopping power of secondary electrons ejected from proton and hydrogen ionization impact, and generated by hydrogen electron loss processes. The consideration of secondary electrons' stopping power can contribute to the study of nano-dosimetry. Our results are in good agreement with existing experimental data. This calculation model can be useful for different applications in medical physics and space radiation health, such as hadron therapy for cancer treatment or radiation protection for astronauts. - Highlights: ► We discussed the stopping cross sections at the Bragg peak region of primary and secondary processes. ► We considered the corrections of incident particle energy focusing on the Rudds semi-empirical model. ► We calculated the electronic and nuclear stopping power, and we deduced the total stopping power. ► We calculated the stopping power of the secondary electrons.

  9. Formation of secondary inorganic aerosols by power plant emissions exhausted through cooling towers in Saxony.

    Science.gov (United States)

    Hinneburg, Detlef; Renner, Eberhard; Wolke, Ralf

    2009-01-01

    The fraction of ambient PM10 that is due to the formation of secondary inorganic particulate sulfate and nitrate from the emissions of two large, brown-coal-fired power stations in Saxony (East Germany) is examined. The power stations are equipped with natural-draft cooling towers. The flue gases are directly piped into the cooling towers, thereby receiving an additionally intensified uplift. The exhausted gas-steam mixture contains the gases CO, CO2, NO, NO2, and SO2, the directly emitted primary particles, and additionally, an excess of 'free' sulfate ions in water solution, which, after the desulfurization steps, remain non-neutralized by cations. The precursor gases NO2 and SO2 are capable of forming nitric and sulfuric acid by several pathways. The acids can be neutralized by ammonia and generate secondary particulate matter by heterogeneous condensation on preexisting particles. The simulations are performed by a nested and multi-scale application of the online-coupled model system LM-MUSCAT. The Local Model (LM; recently renamed as COSMO) of the German Weather Service performs the meteorological processes, while the Multi-scale Atmospheric Transport Model (MUSCAT) includes the transport, the gas phase chemistry, as well as the aerosol chemistry (thermodynamic ammonium-sulfate-nitrate-water system). The highest horizontal resolution in the inner region of Saxony is 0.7 km. One summer and one winter episode, each realizing 5 weeks of the year 2002, are simulated twice, with the cooling tower emissions switched on and off, respectively. This procedure serves to identify the direct and indirect influences of the single plumes on the formation and distribution of the secondary inorganic aerosols. Surface traces of the individual tower plumes can be located and distinguished, especially in the well-mixed boundary layer in daytime. At night, the plumes are decoupled from the surface. In no case does the resulting contribution of the cooling tower emissions to PM10

  10. Enhancement of the incoherent scattering plasma lines due to precipitating protons and secondary electrons

    International Nuclear Information System (INIS)

    Bjoernaa, N.; Havnes, O.; Jensen, J.O.; Trulsen, J.

    1982-01-01

    Precipitating protons in the energy range 1-100 keV are regularly present in the auroral ionosphere. These protons will produce enhancements in the intensity of the upshifted plasma line of the incoherently scattered spectrum. Similarly, secondary electrons produced by the precipitating protons give rise to enhanced plasma line intensities. For a quantitative discussion of these effects an experimentally measured proton flux is adapted and the corresponding secondary electron flux calculated. These particle fluxes are then applied in connection with the EISCAT radar facility. Both fluxes give rise to enhancements of the order of 20. It is possible to separate between proton and electron contributions to the enhanced plasma lines for scattering heights above the source region of secondary electrons. (Auth.)

  11. Measurements of secondary emissions from plasma arc and laser cutting in standard experiments

    International Nuclear Information System (INIS)

    Pilot, G.; Noel, J.P.; Leautier, R.; Steiner, H.; Tarroni, G.; Waldie, B.

    1992-01-01

    As part of an inter-facility comparison of secondary emissions from plasma arc and laser-cutting techniques, standard cutting tests have been done by plasma arc underwater and in air, and by laser beam in air. The same team was commissioned to measure the secondary emissions (solid and gaseous) in each contractor's facility with the same measuring rig. 20 mm and 40 mm thick, grade 304 stainless-steel plates were cut by plasma-torch in three different facilities: Heriot Watt University of Edinburgh, Institut fuer Werkstoffkunde of Universitaet Hannover and CEA/CEN Cadarache. 10 mm and in some cases 20 mm thick, grade 304, stainless-steel plates were cut by laser beam in five different facilities: CEA-CEN Fontenay, CEA-CEN Saclay, Institut fuer Werkstoffkunde of Universitaet Hannover and ENEA/Frascati. The results obtained in the standard experiments are rather similar, and the differences that appear can be explained by the various scales of the involved facilities (semi-industrial and laboratory) and by some particularities in the cutting parameters (an additional secondary gas flow of oxygen in plasma cutting at Universitaet Hannover, for example)

  12. Measurements of secondary emissions from plasma arc and laser cutting in standard experiments

    International Nuclear Information System (INIS)

    Pilot, G.; Noel, M.; Leautier, R.; Steiner, H.; Tarroni, G.; Waldie, B.

    1990-01-01

    As part of an inter-facility comparison of secondary emissions from plasma-arc and laser cutting techniques, standard cutting tests have been done by plasma arc underwater and in air and laser beam in air. The same team, CEA/DPT/SPIN, was commissioned to measure the secondary emissions (solid and gaseous) in each contractor's facility with the same measuring rig. 20 mm and 40 mm thick grade 304 stainless steel plates were cut by plasma-torch in three different facilities: Heriot Watt University of Edinburgh, Institute fuer Werkstoffkunde of Hannover and CEA/CEN Cadarache. 10 mm and sometimes 20 mm thick grade 304 stainless steel plates were cut by laser beam in four different facilities: CEA/CEN Fontenay, CEA/CEN Saclay, Institute fuer Werkstoffkunde of Hannover and ENEA/FRASCATI. The results obtained in the standard experiments are rather similar, the differences that appear can be explained by the various scales of the facilities (semi-industrial and laboratory scale) and by some particularity in the cutting parameters (additional secondary gas flow of oxygen in plasma cutting at Hannover for example). Some supplementary experiments show the importance of some cutting parameters. (author)

  13. Unspeciated organic emissions from combustion sources and their influence on the secondary organic aerosol budget in the United States

    Science.gov (United States)

    Secondary organic aerosol (SOA) formed from the atmospheric oxidation of nonmethane organic gases (NMOG) is a major contributor to atmospheric aerosol mass. Emissions and smog chamber experiments were performed to investigate SOA formation from gasoline vehicles, diesel vehicles,...

  14. Control of secondary electrons from ion beam impact using a positive potential electrode

    Energy Technology Data Exchange (ETDEWEB)

    Crowley, T. P., E-mail: tpcrowley@xanthotechnologies.com; Demers, D. R.; Fimognari, P. J. [Xantho Technologies, LLC, Madison, Wisconsin 53705 (United States)

    2016-11-15

    Secondary electrons emitted when an ion beam impacts a detector can amplify the ion beam signal, but also introduce errors if electrons from one detector propagate to another. A potassium ion beam and a detector comprised of ten impact wires, four split-plates, and a pair of biased electrodes were used to demonstrate that a low-voltage, positive electrode can be used to maintain the beneficial amplification effect while greatly reducing the error introduced from the electrons traveling between detector elements.

  15. Silicon-based metallic micro grid for electron field emission

    International Nuclear Information System (INIS)

    Kim, Jaehong; Jeon, Seok-Gy; Kim, Jung-Il; Kim, Geun-Ju; Heo, Duchang; Shin, Dong Hoon; Sun, Yuning; Lee, Cheol Jin

    2012-01-01

    A micro-scale metal grid based on a silicon frame for application to electron field emission devices is introduced and experimentally demonstrated. A silicon lattice containing aperture holes with an area of 80 × 80 µm 2 and a thickness of 10 µm is precisely manufactured by dry etching the silicon on one side of a double-polished silicon wafer and by wet etching the opposite side. Because a silicon lattice is more rigid than a pure metal lattice, a thin layer of Au/Ti deposited on the silicon lattice for voltage application can be more resistant to the geometric stress caused by the applied electric field. The micro-fabrication process, the images of the fabricated grid with 88% geometric transparency and the surface profile measurement after thermal feasibility testing up to 700 °C are presented. (paper)

  16. Ultralarge area MOS tunnel devices for electron emission

    DEFF Research Database (Denmark)

    Thomsen, Lasse Bjørchmar; Nielsen, Gunver; Vendelbo, Søren Bastholm

    2007-01-01

    density. Oxide thicknesses have been extracted by fitting a model based on Fermi-Dirac statistics to the C-V characteristics. By plotting I-V characteristics in a Fowler plot, a measure of the thickness of the oxide can be extracted from the tunnel current. These apparent thicknesses show a high degree......A comparative analysis of metal-oxide-semiconductor (MOS) capacitors by capacitance-voltage (C-V) and current-voltage (I-V) characteristics has been employed to characterize the thickness variations of the oxide on different length scales. Ultralarge area (1 cm(2)) ultrathin (similar to 5 nm oxide......) MOS capacitors have been fabricated to investigate their functionality and the variations in oxide thickness, with the use as future electron emission devices as the goal. I-V characteristics show very low leakage current and excellent agreement to the Fowler-Nordheim expression for the current...

  17. Data acquisition electronics for positron emission mammography (PEM) detectors

    International Nuclear Information System (INIS)

    Martinez, J.D.; Sebastia, A.; Cerda, J.; Esteve, R.; Mora, F.J.; Toledo, J.F.; Benlloch, J.M.; Gimenez, N.; Gimenez, M.; Lerche, Ch. W.; Pavon, N.; Sanchez, F.

    2005-01-01

    Positron emission mammography (PEM) is an innovative technique to increase sensitivity and overcome the main drawbacks of conventional X-ray screening. However, dedicated PET imaging systems demand specific hardware solutions for data acquisition and processing that can take advantage of the reduction in the number of channels. Data acquisition issues can affect PEM scanners performance and they should be exhaustively addressed in order to exploit the increment in the event count rate. This is crucial in order to reduce both the scanning time and the total injected dose. This paper presents the electronics for our PEM camera prototype that enables us to achieve very high-count rates and perform comprehensive online processing. Results about acquisition in our detector for a typical clinical setup are studied using Monte Carlo simulation of hot lesion phantoms

  18. Ballistic electron emission spectroscopy on Ag/Si devices

    Energy Technology Data Exchange (ETDEWEB)

    Bannani, A; Bobisch, C A; Matena, M; Moeller, R [Department of Physics, Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen, 47048 Duisburg (Germany)], E-mail: amin.bannani@uni-due.de

    2008-09-17

    In this work we report on ballistic electron emission spectroscopy (BEES) studies on epitaxial layers of silver grown on silicon surfaces, with either a Si(111)-(7 x 7) or Si(100)-(2 x 1) surface reconstruction. The experiments were done at low temperature and in ultra-high vacuum (UHV). In addition, BEES measurements on polycrystalline Ag films grown on hydrogen-terminated H:Si(111)-(1 x 1) and H:Si(100)-(2 x 1) surfaces were performed. The Schottky barrier heights were evaluated by BEES. The results are compared to the values for the barrier height reported for macroscopic Schottky diodes. We show that the barrier heights for the epitaxial films substantially differ from the values measured on polycrystalline Ag films, suggesting a strong effect of the interface on the barrier height.

  19. Electron cyclotron emission measurements on JET: Michelson interferometer, new absolute calibration, and determination of electron temperature.

    Science.gov (United States)

    Schmuck, S; Fessey, J; Gerbaud, T; Alper, B; Beurskens, M N A; de la Luna, E; Sirinelli, A; Zerbini, M

    2012-12-01

    At the fusion experiment JET, a Michelson interferometer is used to measure the spectrum of the electron cyclotron emission in the spectral range 70-500 GHz. The interferometer is absolutely calibrated using the hot/cold technique and, in consequence, the spatial profile of the plasma electron temperature is determined from the measurements. The current state of the interferometer hardware, the calibration setup, and the analysis technique for calibration and plasma operation are described. A new, full-system, absolute calibration employing continuous data acquisition has been performed recently and the calibration method and results are presented. The noise level in the measurement is very low and as a result the electron cyclotron emission spectrum and thus the spatial profile of the electron temperature are determined to within ±5% and in the most relevant region to within ±2%. The new calibration shows that the absolute response of the system has decreased by about 15% compared to that measured previously and possible reasons for this change are presented. Temperature profiles measured with the Michelson interferometer are compared with profiles measured independently using Thomson scattering diagnostics, which have also been recently refurbished and recalibrated, and agreement within experimental uncertainties is obtained.

  20. Secondary ion emission from cleaned surfaces bombarded by 100 MeV accelerator beams at the GSI Darmstadt

    International Nuclear Information System (INIS)

    Wien, K.; Becker, O.; Guthier, W.; Knippelberg, W.; Koczon, P.

    1988-01-01

    The 1.4 MeV/n beam facility for the UNILAC/GSI has been used to study secondary ion emission from surfaces cleaned under UHV conditions by ion etching or cleaving of crystals. The desorption phenomena observed by means of TOF mass spectrometry can be classified as follows: (1) Clean metal surfaces emit metal ions being ejected by atomic collisions cascades. Electronic excitation of surface states seems to support ionization. (2) The desorption of contaminants adsorbed at the metal surface is strongly correlated with the electronic energy loss of the projectiles - even, if the content of impurities is very low. (3) Ion formation at the epitaxial surface of fluoride crystals as CaF 2 , MgF 2 and NaF is initiated by the electronic excitation of the crystal. At high beam energies the mass spectrum is dominated by a series of cluster ions. These cluster ions disappear below a certain energy deposit threshold, whereas small atomic ions are observed over the whole energy range

  1. New method for characterizing paper coating structures using argon ion beam milling and field emission scanning electron microscopy.

    Science.gov (United States)

    Dahlström, C; Allem, R; Uesaka, T

    2011-02-01

    We have developed a new method for characterizing microstructures of paper coating using argon ion beam milling technique and field emission scanning electron microscopy. The combination of these two techniques produces extremely high-quality images with very few artefacts, which are particularly suited for quantitative analyses of coating structures. A new evaluation method has been developed by using marker-controlled watershed segmentation technique of the secondary electron images. The high-quality secondary electron images with well-defined pores makes it possible to use this semi-automatic segmentation method. One advantage of using secondary electron images instead of backscattered electron images is being able to avoid possible overestimation of the porosity because of the signal depth. A comparison was made between the new method and the conventional method using greyscale histogram thresholding of backscattered electron images. The results showed that the conventional method overestimated the pore area by 20% and detected around 5% more pores than the new method. As examples of the application of the new method, we have investigated the distributions of coating binders, and the relationship between local coating porosity and base sheet structures. The technique revealed, for the first time with direct evidence, the long-suspected coating non-uniformity, i.e. binder migration, and the correlation between coating porosity versus base sheet mass density, in a straightforward way. © 2010 The Authors Journal compilation © 2010 The Royal Microscopical Society.

  2. Analysis of quantum semiconductor heterostructures by ballistic electron emission spectroscopy

    Science.gov (United States)

    Guthrie, Daniel K.

    1998-09-01

    The microelectronics industry is diligently working to achieve the goal of gigascale integration (GSI) by early in the 21st century. For the past twenty-five years, progress toward this goal has been made by continually scaling down device technology. Unfortunately, this trend cannot continue to the point of producing arbitrarily small device sizes. One possible solution to this problem that is currently under intensive study is the relatively new area of quantum devices. Quantum devices represent a new class of microelectronic devices that operate by utilizing the wave-like nature (reflection, refraction, and confinement) of electrons together with the laws of quantum mechanics to construct useful devices. One difficulty associated with these structures is the absence of measurement techniques that can fully characterize carrier transport in such devices. This thesis addresses this need by focusing on the study of carrier transport in quantum semiconductor heterostructures using a relatively new and versatile measurement technique known as ballistic electron emission spectroscopy (BEES). To achieve this goal, a systematic approach that encompasses a set of progressively more complex structures is utilized. First, the simplest BEES structure possible, the metal/semiconductor interface, is thoroughly investigated in order to provide a foundation for measurements on more the complex structures. By modifying the semiclassical model commonly used to describe the experimental BEES spectrum, a very complete and accurate description of the basic structure has been achieved. Next, a very simple semiconductor heterostructure, a Ga1-xAlxAs single-barrier structure, was measured and analyzed. Low-temperature measurements on this structure were used to investigate the band structure and electron-wave interference effects in the Ga1-xAlxAs single barrier structure. These measurements are extended to a simple quantum device by designing, measuring, and analyzing a set of

  3. Analysis of As implantation profiles in silica by nuclear microanalysis and secondary ion emission

    International Nuclear Information System (INIS)

    Dieumegard, D.; Croset, M.; Cohen, C.; Lhoir, A.; Rigo, S.; Chaumont, J.

    1974-01-01

    Results obtained from analysis using, either the method of elastic backscattering of light or semi-heavy ions ( 4 He + , 14 N + ) about one MeV energy, or the secondary ion emission method are compared. The choice of As implanted Si is explained by the following reasons: As is an element relatively heavy in comparison with Si, that allows an analysis to be effected on a few thousands Angstroems depth in silica using elastic backscattering; the silica chosen as substrate being an amorphous material allows channeling phenomena to the avoided during implantation and analysis [fr

  4. Role of secondary emission on discharge dynamics in an atmospheric pressure dielectric barrier discharge

    Energy Technology Data Exchange (ETDEWEB)

    Tay, W. H.; Kausik, S. S.; Yap, S. L.; Wong, C. S., E-mail: cswong@um.edu.my [Plasma Technology Research Centre, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-04-15

    The discharge dynamics in an atmospheric pressure dielectric barrier discharge (DBD) is studied in a DBD reactor consisting of a pair of stainless steel parallel plate electrodes. The DBD discharge has been generated by a 50 Hz ac high voltage power source. The high-speed intensified charge coupled device camera is used to capture the images of filaments occurring in the discharge gap. It is observed that frequent synchronous breakdown of micro discharges occurs across the discharge gap in the case of negative current pulse. The experimental results reveal that secondary emissions from the dielectric surface play a key role in the synchronous breakdown of plasma filaments.

  5. Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Ji; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.

    2013-05-10

    Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of SOA generated from two monoterpenes, limonene and a-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ~100 ppb ammonia vapor in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (~0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for excitation = 420+- 50 nm and emission = 475 +- 38 nm. The window of the strongest fluorescence shifted to excitation = 320 +- 25 nm and emission = 425 +- 38 nm for the a-pinene-derived SOA. Both regions overlap with the excitation-emission matrix (EEM) spectra of some of the fluorophores found in primary biological aerosols. Our study suggests that, despite the low quantum yield, the aged SOA particles should have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

  6. Secondary aerosol formation from stress-induced biogenic emissions and possible climate feedbacks

    Directory of Open Access Journals (Sweden)

    Th. F. Mentel

    2013-09-01

    Full Text Available Atmospheric aerosols impact climate by scattering and absorbing solar radiation and by acting as ice and cloud condensation nuclei. Biogenic secondary organic aerosols (BSOAs comprise an important component of atmospheric aerosols. Biogenic volatile organic compounds (BVOCs emitted by vegetation are the source of BSOAs. Pathogens and insect attacks, heat waves and droughts can induce stress to plants that may impact their BVOC emissions, and hence the yield and type of formed BSOAs, and possibly their climatic effects. This raises questions of whether stress-induced changes in BSOA formation may attenuate or amplify effects of climate change. In this study we assess the potential impact of stress-induced BVOC emissions on BSOA formation for tree species typical for mixed deciduous and Boreal Eurasian forests. We studied the photochemical BSOA formation for plants infested by aphids in a laboratory setup under well-controlled conditions and applied in addition heat and drought stress. The results indicate that stress conditions substantially modify BSOA formation and yield. Stress-induced emissions of sesquiterpenes, methyl salicylate, and C17-BVOCs increase BSOA yields. Mixtures including these compounds exhibit BSOA yields between 17 and 33%, significantly higher than mixtures containing mainly monoterpenes (4–6% yield. Green leaf volatiles suppress SOA formation, presumably by scavenging OH, similar to isoprene. By classifying emission types, stressors and BSOA formation potential, we discuss possible climatic feedbacks regarding aerosol effects. We conclude that stress situations for plants due to climate change should be considered in climate–vegetation feedback mechanisms.

  7. Electron cyclotron emission measurements during 28 GHz electron cyclotron resonance heating in Wendelstein WVII-A stellarator

    International Nuclear Information System (INIS)

    Hartfuss, H.J.; Gasparino, U.; Tutter, M.; Brakel, R.; Cattanei, G.; Dorst, D.; Elsner, A.; Engelhardt, K.; Erckmann, V.; Grieger, G.; Grigull, P.; Hacker, H.; Jaeckel, H.; Jaenicke, R.; Junker, J.; Kick, M.; Kroiss, H.; Kuehner, G.; Maassberg, H.; Mahn, C.; Mueller, G.; Ohlendorf, W.; Rau, F.; Renner, H.; Ringler, H.; Sardei, F.; Weller, A.; Wobig, H.; Wuersching, E.; Zippe, M.; Kasparek, W.; Mueller, G.A.; Raeuchle, E.; Schueller, P.G.; Schwoerer, K.; Thumm, M.

    1987-11-01

    Electron cyclotron emission measurements have been carried out on electron cyclotron resonance heated plasmas in the WENDELSTEIN VII-A Stellarator. Blackbody radiation from the thermalized plasma main body as well as radiation from a small amount of weakly relativistic suprathermal electrons has been detected. In addition sideband emission has been observed near the second harmonic of the heating line source. Harmonic generation and parametric wave decay at the upper hybrid layer may be a reasonable explanation. (orig.)

  8. Electron-cyclotron maser emission during solar and stellar flares

    International Nuclear Information System (INIS)

    Winglee, R.M.

    1985-01-01

    Radio bursts, with high brightness temperature 10 to the 10th power K and high degree of polarization, and the heating of the solar and stellar coronae during flares have been attributed to emission from the semirelativistic maser instability. In plasmas where the electron-plasma frequency, p, omega sub p, and the electron-cyclotron frequency, Omega sub e, are such that omega sup 2 sub p/Omega sup 2 sub e 1, x-mode growth dominates while z-mode growth dominates if omega sup 2 sub p/Omega sup 2 sub e is of order unity. The actual value of omega sup 2 sub p/Omega sup 2 sub e at which x-mode growth dominates is shown to be dependent on the plasma temperature with x-mode growth dominating at higher omega sub p/Omega sub e as the plasma temperature increases. Observations from a set of 20 impulsive flares indicate that the derived conditions for the dominance of x-mode growth are satisfied in about 75 percent of the flares

  9. Low-energy plasma-cathode electron gun with a perforated emission electrode

    Science.gov (United States)

    Burdovitsin, Victor; Kazakov, Andrey; Medovnik, Alexander; Oks, Efim; Tyunkov, Andrey

    2017-11-01

    We describe research of influence of the geometric parameters of perforated electrode on emission parameters of a plasma cathode electron gun generating continuous electron beams at gas pressure 5-6 Pa. It is shown, that the emission current increases with increasing the hole diameters and decreasing the thickness of the perforated emission electrode. Plasma-cathode gun with perforated electron can provide electron extraction with an efficiency of up to 72 %. It is shown, that the current-voltage characteristic of the electron gun with a perforated emission electrode differs from that of similar guns with fine mesh grid electrode. The plasma-cathode electron gun with perforated emission electrode is used for electron beam welding and sintering.

  10. Microstructure-Sensitive Investigation of Fracture Using Acoustic Emission Coupled With Electron Microscopy

    Science.gov (United States)

    Wisner, Brian; Cabal, Mike; Vanniamparambiland, Prashanth A.; Leser, William; Hochhalter, Jacob; Kontsos, Antonios

    2015-01-01

    A novel technique using Scanning Electron Microscopy (SEM) in conjunction with Acoustic Emission (AE) monitoring is proposed to investigate microstructure-sensitive fatigue and fracture of metals. The coupling between quasi in situ microscopy with actual in situ nondestructive evaluation falls into the ICME framework and the idea of quantitative data-driven characterization of material behavior. To validate the use of AE monitoring inside the SEM chamber, Aluminum 2024-B sharp notch specimen were tested both inside and outside the microscope using a small scale mechanical testing device. Subsequently, the same type of specimen was tested inside the SEM chamber. Load data were correlated with both AE information and observations of microcracks around grain boundaries as well as secondary cracks, voids, and slip bands. The preliminary results are in excellent agreement with similar findings at the mesoscale. Extensions of the application of this novel technique are discussed.

  11. Angular distributions of absorbed dose of Bremsstrahlung and secondary electrons induced by 18-, 28- and 38-MeV electron beams in thick targets.

    Science.gov (United States)

    Takada, Masashi; Kosako, Kazuaki; Oishi, Koji; Nakamura, Takashi; Sato, Kouichi; Kamiyama, Takashi; Kiyanagi, Yoshiaki

    2013-03-01

    Angular distributions of absorbed dose of Bremsstrahlung photons and secondary electrons at a wide range of emission angles from 0 to 135°, were experimentally obtained using an ion chamber with a 0.6 cm(3) air volume covered with or without a build-up cap. The Bremsstrahlung photons and electrons were produced by 18-, 28- and 38-MeV electron beams bombarding tungsten, copper, aluminium and carbon targets. The absorbed doses were also calculated from simulated photon and electron energy spectra by multiplying simulated response functions of the ion chambers, simulated with the MCNPX code. Calculated-to-experimental (C/E) dose ratios obtained are from 0.70 to 1.57 for high-Z targets of W and Cu, from 15 to 135° and the C/E range from 0.6 to 1.4 at 0°; however, the values of C/E for low-Z targets of Al and C are from 0.5 to 1.8 from 0 to 135°. Angular distributions at the forward angles decrease with increasing angles; on the other hand, the angular distributions at the backward angles depend on the target species. The dependences of absorbed doses on electron energy and target thickness were compared between the measured and simulated results. The attenuation profiles of absorbed doses of Bremsstrahlung beams at 0, 30 and 135° were also measured.

  12. Polychlorinated dibenzo-p-dioxin and dibenzofuran and polychlorinated biphenyl emissions from different smelting stages in secondary copper metallurgy.

    Science.gov (United States)

    Hu, Jicheng; Zheng, Minghui; Nie, Zhiqiang; Liu, Wenbin; Liu, Guorui; Zhang, Bing; Xiao, Ke

    2013-01-01

    Secondary copper production has received much attention for its high emissions of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) reported in previous studies. These studies focused on the estimation of total PCDD/F and polychlorinated biphenyl (PCB) emissions from secondary copper smelters. However, large variations in PCDD/F and PCB emissions reported in these studies were not analyzed and discussed further. In this study, stack gas samples at different smelting stages (feeding-fusion, oxidation and deoxidization) were collected from four plants to investigate variations in PCDD/F and PCB emissions and characteristics during the secondary copper smelting process. The results indicate that PCDD/F emissions occur mainly at the feeding-fusion stage and these emissions contribute to 54-88% of the total emissions from the secondary copper smelting process. The variation in feed material and operating conditions at different smelting stages leads to the variation in PCDD/F emissions during the secondary copper smelting process. The total PCDD/F and PCB discharge (stack gas emission+fly ash discharge) is consistent with the copper scrap content in the raw material in the secondary copper smelters investigated. On a production basis of 1 ton copper, the total PCDD/F and dl-PCB discharge was 102, 24.8 and 5.88 μg TEQ t(-1) for the three plants that contained 100%, 30% and 0% copper scrap in their raw material feed, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Gas phase emissions from cooking processes and their secondary aerosol production potential

    Science.gov (United States)

    Klein, Felix; Platt, Stephen; Bruns, Emily; Termime-roussel, Brice; Detournay, Anais; Mohr, Claudia; Crippa, Monica; Slowik, Jay; Marchand, Nicolas; Baltensperger, Urs; Prevot, Andre; El Haddad, Imad

    2014-05-01

    Long before the industrial evolution and the era of fossil fuels, high concentrations of aerosol particles were alluded to in heavily populated areas, including ancient Rome and medieval London. Recent radiocarbon measurements (14C) conducted in modern megacities came as a surprise: carbonaceous aerosol (mainly organic aerosol, OA), a predominant fraction of particulate matter (PM), remains overwhelmingly non-fossil despite extensive fossil fuel combustion. Such particles are directly emitted (primary OA, POA) or formed in-situ in the atmosphere (secondary OA, SOA) via photochemical reactions of volatile organic compounds (VOCs). Urban levels of non-fossil OA greatly exceed the levels measured in pristine environments strongly impacted by biogenic emissions, suggesting a contribution from unidentified anthropogenic non-fossil sources to urban OA. Positive matrix factorization (PMF) techniques applied to ambient aerosol mass spectrometer (AMS, Aerodyne) data identify primary cooking emissions (COA) as one of the main sources of primary non-fossil OA in major cities like London (Allan et al., 2010), New York (Sun et al., 2011) and Beijing (Huang et al., 2010). Cooking processes can also emit VOCs that can act as SOA precursors, potentially explaining in part the high levels of oxygenated OA (OOA) identified by the AMS in urban areas. However, at present, the chemical nature of these VOCs and their secondary aerosol production potential (SAPP) remain virtually unknown. The approach adopted here involves laboratory quantification of PM and VOC emission factors from the main primary COA emitting processes and their SAPP. Primary emissions from deep-fat frying, vegetable boiling, vegetable frying and meat cooking for different oils, meats and vegetables were analysed under controlled conditions after ~100 times dilution. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a high resolution proton transfer time-of-flight mass spectrometer (PTR

  14. A line-of-sight electron cyclotron emission receiver for electron cyclotron resonance heating feedback control of tearing modes

    DEFF Research Database (Denmark)

    Oosterbeek, J.W.; Bürger, A.; Westerhof, E.

    2008-01-01

    An electron cyclotron emission (ECE) receiver inside the electron cyclotron resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as a Fabry-Perot interferometer under an angle inside the electron cyclotron wave (ECW) bea...

  15. Primary Emission and the Potential of Secondary Aerosol Formation from Chinese Gasoline Engine Exhaust

    Science.gov (United States)

    Hu, Min; Peng, Jianfei; Qin, Yanhong; Du, Zhuofei; Li, Mengjin; Zheng, Rong; Zheng, Jing; Shang, Dongjie; Lu, Sihua; Wu, Yusheng; Zeng, Limin; Guo, Song; Shao, Min; Wang, Yinhui; Shuai, Shijin

    2017-04-01

    Along with the urbanization and economic growth, vehicle population in China reached 269 million, ranked the second in the world in 2015. Gasoline vehicle is identified to be the main source for urban PM2.5 in China, accounting for 15%-31%. In this study the impact of fuel components on PM2.5 and volatile organic compounds (VOCs) emissions from a gasoline port fuel injection (PFI) engine and a gasoline direct injection (GDI) engine are discussed. Results show that, higher proportion of aromatics, alkenes or sulfur in gasoline fuel will lead to higher PM emissions. The PM from the PFI engine mainly consists of OC and a small amount of EC and inorganic ions, while the PM discharge from the GDI engine mainly consists of EC, OM and a small amount of inorganic ions. Since the GDI engines can reduce fuel consumption and CO2 emissions, and it would become more and more popular in the near future. The characteristics of POM component, emission factors and source profile were investigated from GDI engine, particularly focused on the effect of engine speed, load and the catalyst, which will be very much helpful for source identification as source indicators. Chamber experiments were conducted to quantify the potential of secondary aerosol formation from exhaust of a PFI gasoline engine and China V gasoline fuel. During 4-5 h simulation, equivalent to10 days of atmospheric photo-oxidation in Beijing, the extreme SOA production was 426 ± 85 mg/kg fuel, with high precursors and OH exposure. 14% of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatility organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reduction of emissions of aerosol precursor gases from vehicles is essential to mediate pollution in China.

  16. Quantitative evaluation of emission controls on primary and secondary organic aerosol sources during Beijing 2008 Olympics

    Directory of Open Access Journals (Sweden)

    S. Guo

    2013-08-01

    Full Text Available To assess the primary and secondary sources of fine organic aerosols after the aggressive implementation of air pollution controls during the 2008 Beijing Olympic Games, 12 h PM2.5 values were measured at an urban site at Peking University (PKU and an upwind rural site at Yufa during the CAREBEIJING-2008 (Campaigns of Air quality REsearch in BEIJING and surrounding region summer field campaign. The average PM2.5 concentrations were 72.5 ± 43.6 μg m−3 and 64.3 ± 36.2 μg m−3 (average ± standard deviation, below as the same at PKU and Yufa, respectively, showing the lowest concentrations in recent years. Combining the results from a CMB (chemical mass balance model and secondary organic aerosol (SOA tracer-yield model, five primary and four secondary fine organic aerosol sources were compared with the results from previous studies in Beijing. The relative contribution of mobile sources to PM2.5 concentrations was increased in 2008, with diesel engines contributing 16.2 ± 5.9% and 14.5 ± 4.1% and gasoline vehicles contributing 10.3 ± 8.7% and 7.9 ± 6.2% to organic carbon (OC at PKU and Yufa, respectively. Due to the implementation of emission controls, the absolute OC concentrations from primary sources were reduced during the Olympics, and the contributions from secondary formation of OC represented a larger relative source of fine organic aerosols. Compared with the non-controlled period prior to the Olympics, primary vehicle contributions were reduced by 30% at the urban site and 24% at the rural site. The reductions in coal combustion contributions were 57% at PKU and 7% at Yufa. Our results demonstrate that the emission control measures implemented in 2008 significantly alleviated the primary organic particle pollution in and around Beijing. However, additional studies are needed to provide a more comprehensive assessment of the emission control effectiveness on SOA formation.

  17. Electron Conditioning of Technical Aluminium Surfaces: Effect on the Secondary Electron Yield

    Energy Technology Data Exchange (ETDEWEB)

    Le Pimpec, F.

    2004-12-13

    The effect of electron conditioning on commercially aluminium alloys 1100 and 6063 were investigated. Contrary to the assumption that electron conditioning, if performed long enough, can reduce and stabilize the SEY to low values (< 1.3, value of many pure elements [1] ), the SEY of aluminium did not go lower than 1.8. In fact, it reincreases with continued electron exposure dose.

  18. Emissions of Toxic Carbonyls in an Electronic Cigarette

    Directory of Open Access Journals (Sweden)

    Guthery William

    2016-01-01

    Full Text Available Electronic cigarettes (e-cigs provide a smoke-free alternative for inhalation of nicotine without the vast array of toxic and carcinogenic combustion products produced by tobacco smoke. Elevated levels of toxic carbonyls may be generated during vaporisation; however, it is unclear whether that is indicative of a fault with the device or is due to the applied conditions of the test. A device, designed and built at this facility, was tested to determine the levels of selected toxic carbonyls. The reservoir was filled with approximately 960 mg of an e-liquid formulation containing 1.8% (w/v nicotine. Devices were puffed 200 times in blocks of 40 using a standardised regime consisting of a 55 mL puff volume; 3 s puff duration; 30 s puff interval; square wave puff profile. Confirmatory testing for nicotine and total aerosol delivery resulted in mean (n = 8 values of 10 mg (RSD 12.3% and 716 mg (RSD 11.2%, respectively. Emissions of toxic carbonyls were highly variable yet were between < 0.1% and 22.9% of expected levels from a Kentucky Reference Cigarette (K3R4F puffed 200 times under Health Canada Intense smoking conditions. It has been shown that a device built to a high specification with relatively consistent nicotine and aerosol delivery emits inconsistent levels of carbonyls. The exposure is greatly reduced when compared with lit tobacco products. However, it was observed that as the reservoirs neared depletion then emission levels were significantly higher

  19. Modification of C60/C70+Pd film structure under electric field influence during electron emission

    International Nuclear Information System (INIS)

    Czerwosz, E.; Dluzewski, P.; Kozlowski, M.

    2001-01-01

    We investigated the modification of structure of C 60 /C 70 +Pd films during cold electron emission from these films. Films were obtained by vacuum thermal deposition from two sources and were characterised before and after electron emission measurements by transmission electron microscopy and electron diffraction. Films were composed of nanocrystalline Pd objects dispersed in carbon/fullerenes matrix. I-V characteristics for electron emission were obtained in diode geometry with additionally applied voltage along the film surface. The modification of film structure occurred under applied electric field and the grouping of Pd nano crystals into bigger objects was observed

  20. Photoelectric emission from negative-electron-affinity diamond (111) surfaces: Exciton breakup versus conduction-band emission

    International Nuclear Information System (INIS)

    Bandis, C.; Pate, B.B.

    1995-01-01

    We have recently reported that bound electron-hole pairs (Mott-Wannier excitons) are the dominant source of photoelectron emission from specially prepared [''as-polished'' C(111)-(1x1):H] negative-electron-affinity diamond surfaces for near-band-gap excitation up to 0.5 eV above threshold [C. Bandis and B. B. Pate, Phys. Rev. Lett. 74, 777 (1995)]. It was found that photoexcited excitons transport to the surface, break up, and emit their electron. In this paper, we extend the study of exciton-derived emission to include partial yield (constant final-state) analysis as well as angular distribution measurements of the photoelectric emission. In addition, we find that exciton-derived emission does not always dominate. Photoelectric emission properties of the in situ ''rehydrogenated'' (111)-(1x1):H diamond surface are characteristically different than emission observed from the as-polished (111)-(1x1):H surface. The rehydrogenated surface has additional downward band bending as compared to the as-polished surface. In confirmation of the assignment of photoelectric yield to exciton breakup emission, we find a significant enhancement of the total electron yield when the downward band bending of the hydrogenated surface is increased. The functional form of the observed total electron yield demonstrates that, in contrast to the as-polished surface, conduction-band electrons are a significant component of the observed photoelectric yield from the in situ hydrogenated (111)-(1x1):H surface. Furthermore, electron emission characteristics of the rehydrogenated surface confirms our assignment of a Fan phonon-cascade mechanism for thermalization of excitons

  1. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    Directory of Open Access Journals (Sweden)

    A. Gover

    2006-06-01

    Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.

  2. Self-amplified spontaneous emission free electron laser devices and nonideal electron beam transport

    Directory of Open Access Journals (Sweden)

    L. L. Lazzarino

    2014-11-01

    Full Text Available We have developed, at the SPARC test facility, a procedure for a real time self-amplified spontaneous emission free electron laser (FEL device performance control. We describe an actual FEL, including electron and optical beam transport, through a set of analytical formulas, allowing a fast and reliable on-line “simulation” of the experiment. The system is designed in such a way that the characteristics of the transport elements and the laser intensity are measured and adjusted, via a real time computation, during the experimental run, to obtain an on-line feedback of the laser performances. The detail of the procedure and the relevant experimental results are discussed.

  3. Band rejection filter for measurement of electron cyclotron emission during electron cyclotron heating

    International Nuclear Information System (INIS)

    Iwase, Makoto; Ohkubo, Kunizo; Kubo, Shin; Idei, Hiroshi.

    1996-05-01

    For the measurement of electron cyclotron emission from the high temperature plasma, a band rejection filter in the range of 40-60 GHz is designed to reject the 53.2 GHz signal with large amplitude from the gyrotron for the purpose of plasma electron heating. The filter developed with ten sets of three quarters-wavelength coupled by TE 111 mode of tunable resonant cavity has rejection of 50 dB and 3 dB bandwidth of 500 MHz. The modified model of Tschebysheff type for the prediction of rejection is proposed. It is confirmed that the measured rejection as a function of frequency agrees well with the experimental results for small coupling hole, and also clarified that the rejection ratio increases for the large coupling hole. (author)

  4. Development of wave length-dispersive soft x-ray emission spectrometers for transmission electron microscopes - an introduction of valence electron spectroscopy for transmission electron microscopy

    International Nuclear Information System (INIS)

    Terauchi, Masami; Koike, Masato; Fukushima, Kurio; Kimura, Atsushi

    2010-01-01

    Two types of wavelength-dispersive soft X-ray spectrometers, a high-dispersion type and a conventional one, for transmission electron microscopes were constructed. Those spectrometers were used to study the electronic states of valence electrons (bonding electrons). Both spectrometers extended the acceptable energy regions to higher than 2000 eV. The best energy resolution of 0.08 eV was obtained for an Al L-emission spectrum by using the high-dispersion type spectrometer. By using the spectrometer, C K-emission of carbon allotropes, Cu L-emission of Cu 1-x Zn x alloys and Pt M-emission spectra were presented. The FWHM value of 12 eV was obtained for the Pt Mα-emission peak. The performance of the conventional one was also presented for ZnS and a section specimen of a multilayer device. W-M and Si-K emissions were clearly resolved. Soft X-ray emission spectroscopy based on transmission electron microscopy (TEM) has an advantage for obtaining spectra from a single crystalline specimen with a defined crystal setting. As an example of anisotropic soft X-ray emission, C K-emission spectra of single crystalline graphite with different crystal settings were presented. From the spectra, density of states of π- and σ-bondings were separately derived. These results demonstrated a method to analyse the electronic states of valence electrons of materials in the nanometre scale based on TEM. (author)

  5. Delayed electron emission in strong-field driven tunnelling from a metallic nanotip in the multi-electron regime

    Science.gov (United States)

    Yanagisawa, Hirofumi; Schnepp, Sascha; Hafner, Christian; Hengsberger, Matthias; Kim, Dong Eon; Kling, Matthias F.; Landsman, Alexandra; Gallmann, Lukas; Osterwalder, Jürg

    2016-01-01

    Illuminating a nano-sized metallic tip with ultrashort laser pulses leads to the emission of electrons due to multiphoton excitations. As optical fields become stronger, tunnelling emission directly from the Fermi level becomes prevalent. This can generate coherent electron waves in vacuum leading to a variety of attosecond phenomena. Working at high emission currents where multi-electron effects are significant, we were able to characterize the transition from one regime to the other. Specifically, we found that the onset of laser-driven tunnelling emission is heralded by the appearance of a peculiar delayed emission channel. In this channel, the electrons emitted via laser-driven tunnelling emission are driven back into the metal, and some of the electrons reappear in the vacuum with some delay time after undergoing inelastic scattering and cascading processes inside the metal. Our understanding of these processes gives insights on attosecond tunnelling emission from solids and should prove useful in designing new types of pulsed electron sources. PMID:27786287

  6. Secondary electron yields of carbon-coated and polished stainless steel

    International Nuclear Information System (INIS)

    Ruzic, D.; Moore, R.; Manos, D.; Cohen, S.

    1982-01-01

    To increase the power throughput to a plasma of an existing lower hybrid waveguide, secondary electron production on the walls and subsequent electron multiplication must be reduced. Since carbon has a low secondary electron coefficient (delta), measurements were performed for several UHV compatible carbon coatings (Aquadag/sup X/, vacuum pyrolyzed Glyptal/sup X/, and lamp black deposited by electrophoresis) as a function of primary beam voltage (35 eV to 10 keV), surface roughness (60 through 600 grit mechanical polishing and electropolishing), coating thickness, and angle of incidence (theta). Also measured were uncoated stainless steel, Mo, Cu, Ti, TiC, and ATJ graphite. The yields were obtained by varying the sample bias and measuring the collected current while the samples were in the electron beam of a scanning Auger microprobe. This technique allows delta measurements of Auger characterized surfaces with < or =0.3 mm spatial resolution. Results show delta to have a typical energy dependence, with a peak occurring at 200 to 300 eV for normal incidence, and at higher energy for larger theta. In general, delta increases with theta more for smooth surfaces than for rough ones. Ninety percent of the secondary electrons have energies less than 25 eV. Some carbonized coating and surface treatment combinations give delta/sub max/ = 0.88 +- 0.01 for normal electron beam incidence: a reduction of almost 40% compared to untreated stainless steel

  7. New Electron Cyclotron Emission Diagnostic Based Upon the Electron Bernstein Wave

    International Nuclear Information System (INIS)

    Efthimion, P.C.; Hosea, J.C.; Kaita, R.; Majeski, R.; Taylor, G.

    1999-01-01

    Most magnetically confined plasma devices cannot take advantage of standard Electron Cyclotron Emission (ECE) diagnostics to measure temperature. They either operate at high density relative to their magnetic field or they do not have sufficient density and temperature to reach the blackbody condition. The standard ECE technique measures the electromagnetic waves emanating from the plasma. Here we propose to measure electron Bernstein waves (EBW) to ascertain the local electron temperature in these plasmas. The optical thickness of EBW is extremely high because it is an electrostatic wave with a large k(subscript i). One can reach the blackbody condition with a plasma density approximately equal to 10(superscript 11) cm(superscript -3) and electron temperature approximately equal to 1 eV. This makes it attractive to most plasma devices. One serious issue with using EBW is the wave accessibility. EBW may be accessible by either direct coupling or mode conversion through an extremely narrow layer (approximately 1-2 mm) in low field devices

  8. Detection of secondary electrons with pixelated hybrid semiconductor detectors; Sekundaerelektronennachweis mit pixelierten hybriden Halbleiterdetektoren

    Energy Technology Data Exchange (ETDEWEB)

    Gebert, Ulrike Sonja

    2011-09-14

    Within the scope of this thesis, secondary electrons were detected with a pixelated semiconductor detector named Timepix. The Timepix detector consists of electronics and a sensor made from a semiconductor material. The connection of sensor and electronics is done for each pixel individually using bump bonds. Electrons with energies above 3 keV can be detected with the sensor. One electron produces a certain amount of electron-hole pairs according to its energy. The charge then drifts along an electric field to the pixel electronics, where it induces an electric signal. Even without a sensor it is possible to detect an electric signal from approximately 1000 electrons directly in the pixel electronics. Two different detector systems to detect secondary electrons using the Timepix detector were investigated during this thesis. First of all, a hybrid photon detector (HPD) was used to detect single photoelectrons. The HPD consists of a vacuum vessel with an entrance window and a cesium iodine photocathode at the inner surface of the window. Photoelectrons are released from the photocathode by incident light and are accelerated in an electric field towards the Timepix detector, where the point of interaction and the arrival time of the electron is determined. With a proximity focusing setup, a time resolution of 12 ns (with an acceleration voltage of 20 kV between photocathode and Timepix detector) was obtained. The HPD examined in this thesis showed a strong dependence of the dark rate form the acceleration voltage and the pressure in the vacuum vessel. At a pressure of few 10{sup -5} mbar and an acceleration voltage of 20 kV, the dark rate was about 800 Hz per mm{sup 2} area of the read out photocathode. One possibility to reduce the dark rate is to identify ion feedback events. With a slightly modified setup it was possible to reduce the dark rate to 0.5 Hz/mm{sup 2}. To achieve this, a new photocathode was mounted in a shorter distance to the detector. The

  9. Electron-electron correlation, resonant photoemission and X-ray emission spectra

    International Nuclear Information System (INIS)

    Parlebas, J.C.; Kotani, Akio; Tanaka, Satoshi.

    1991-01-01

    In this short review paper we essentially focus on the high energy spectroscopies which involve second order quantum processes, i.e., resonance photoemission, Auger and X-ray emission spectroscopies, denoted respectively by RXPS, AES and XES. First, we summarize the main 3p-RXPS and AES results obtained in Cu and Ni metals; especially we recall that the satellite near the 3p-threshold in the spectra, which arises from a d-hole pair bound state, needs a careful treatment of the electron-electron correlation. Then we analyze the RXPS spectra in a few Ce compounds (CeO 2 , Ce 2 O 3 and CeF 3 ) involving 3d or 4d core levels and we interpret the spectra consistently with the other spectroscopies, such as core XPS and XAS which are first order quantum processes. Finally within the same one-impurity model and basically with the same sets of parameters, we review a theory for the Ce 5p→3d XES, as well as for the corresponding RXES, where (1) the incident X-ray is tuned to resonate with the 3d→4f transition and (2) the X-ray emission due to the 5p→3d transition is actually observed. The paper ends with a general discussion. (author) 77 refs

  10. Electronic emission and electron spin resonance of irradiated clothes: (cottons, synthetic clothes)

    International Nuclear Information System (INIS)

    El Ajouz Rima, H.

    1984-10-01

    This thesis is devoted to a new method of dosimetry applicable to accidental irradiations. It is based on the use of cotton and synthetic fabric clothes as detectors. It enables absorbed doses and body dose distributions to be estimated after an accidental irradiation. A bibliography on textile fibres used for clothing is presented in the first chapter: origin, structure, industrial treatments, effects of heat, light, ionizing radiations. In the second chapter, electronic emission generated by double stimulation (thermal and optic) is described. This phenomenon reveals changes in the surface state of cotton. Exo-emission was chosen because of its high sensitivity in dosimetry. The third chapter is devoted to the application of electron paramagnetic resonance to the dosimetry of irradiated fabrics. After a brief description of the spectrometer used, the results obtained with commercial cotton fabrics and with a special fabric realized by the Institut Textile de France are described some of these fabrics were subjected to special treatments either before or after irradiation. Synthetic fabrics (polyesters and polypropylene) have also been studied. (author)

  11. Ultrafast electron field emission from gold resonant antennas studied by two terahertz pulse experiments

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew C.

    2015-01-01

    Summary form only given. Ultrafast electron field emission from gold resonant antennas induced by strong terahertz (THz) transient is investigated using two THz pulse experiments. It is shown that UV emission from nitrogen plasma generated by liberated electrons is a good indication of the local...

  12. Electron and photon emissions from gold nanoparticles irradiated by X-ray photons

    Energy Technology Data Exchange (ETDEWEB)

    Casta, R., E-mail: castaromain@gmail.com, E-mail: romain.casta@irsamc.ups-tlse.fr; Champeaux, J.-P.; Moretto-Capelle, P.; Sence, M.; Cafarelli, P. [Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, CNRS, UMR 5589 (France)

    2015-01-15

    In this paper, we develop a totally new probabilistic model for the electron and photon emission of gold nanoparticles irradiated by X-ray photons. This model allows direct applications to recent researches about the radiotherapy enhancement by gold nanoparticles in the context of cancer treatment. Our model uses, in a complete original way, simulated Auger cascade and stopping power to compute electron emission spectra, photon emission spectra and released energy inside the material of gold nanoparticles. It allows us to present new results about the electron and photon emission of gold nanoparticle irradiated by hard X-rays.

  13. Secondary signal imaging (SSI) electron tomography (SSI-ET): A new three-dimensional metrology for mesoscale specimens in transmission electron microscope.

    Science.gov (United States)

    Han, Chang Wan; Ortalan, Volkan

    2015-09-01

    We have demonstrated a new electron tomography technique utilizing the secondary signals (secondary electrons and backscattered electrons) for ultra thick (a few μm) specimens. The Monte Carlo electron scattering simulations reveal that the amount of backscattered electrons generated by 200 and 300keV incident electrons is a monotonic function of the sample thickness and this causes the thickness contrast satisfying the projection requirement for the tomographic reconstruction. Additional contribution of the secondary electrons emitted from the edges of the specimens enhances the visibility of the surface features. The acquired SSI tilt series of the specimen having mesoscopic dimensions are successfully reconstructed verifying that this new technique, so called the secondary signal imaging electron tomography (SSI-ET), can directly be utilized for 3D structural analysis of mesoscale structures. Published by Elsevier Ltd.

  14. Secondary ion emission from ultra-thin oxide layers bombarded by energetic (MeV) heavy ions: depth of origin and layer homogeneity

    International Nuclear Information System (INIS)

    Allali, H.; Nsouli, B.; Thomas, J.P.; Cabaud, B.; Fuchs, G.; Hoareau, A.; Treilleux, M.; Danel, J.S.

    1993-09-01

    The escape depth of the secondary ions resulting from electronic sputtering of fast heavy ions in inorganic thin films has been investigated. Chromium layers deposited onto SiO 2 substrate as well as SiO x layers deposited onto chromium substrate have been characterized by secondary ion emission mass spectrometry (SIMS) in combination with time-of-flight (TOF) mass analysis (also referred as HSF-SIMS). These crossed experiments lead to a value around 1 nm for SiO x layers and 0.5 nm for Cr layers. On the other hand, HSF-SIMS can be used to correlate the intensity of the secondary ion emission to the film coverage rate and (or) the morphology of particular films like those produced by Low Energy Cluster Beam Deposition (LECBD). Using Sb deposits, the non-linear relationship between ion emission and coverage is interpreted in terms of sputtering enhancement in the individual supported clusters. (author) 22 refs., 9 figs., 1 tab

  15. Ion induced electron emission statistics under Agm- cluster bombardment of Ag

    Science.gov (United States)

    Breuers, A.; Penning, R.; Wucher, A.

    2018-05-01

    The electron emission from a polycrystalline silver surface under bombardment with Agm- cluster ions (m = 1, 2, 3) is investigated in terms of ion induced kinetic excitation. The electron yield γ is determined directly by a current measurement method on the one hand and implicitly by the analysis of the electron emission statistics on the other hand. Successful measurements of the electron emission spectra ensure a deeper understanding of the ion induced kinetic electron emission process, with particular emphasis on the effect of the projectile cluster size to the yield as well as to emission statistics. The results allow a quantitative comparison to computer simulations performed for silver atoms and clusters impinging onto a silver surface.

  16. Tunneling emission of electrons from semiconductors' valence bands in high electric fields

    International Nuclear Information System (INIS)

    Kalganov, V. D.; Mileshkina, N. V.; Ostroumova, E. V.

    2006-01-01

    Tunneling emission currents of electrons from semiconductors to vacuum (needle-shaped GaAs photodetectors) and to a metal (silicon metal-insulator-semiconductor diodes with a tunneling-transparent insulator layer) are studied in high and ultrahigh electric fields. It is shown that, in semiconductors with the n-type conductivity, the major contribution to the emission current is made by the tunneling emission of electrons from the valence band of the semiconductor, rather than from the conduction band

  17. Secondary-electron yield from Au induced by highly charged Ta ions

    Czech Academy of Sciences Publication Activity Database

    Krása, Josef; Láska, Leoš; Stöckli, M. P.; Fry, D.

    2001-01-01

    Roč. 173, - (2001), s. 281-286 ISSN 0168-583X R&D Projects: GA AV ČR IAA1010819 Institutional research plan: CEZ:AV0Z1010914 Keywords : highly charged ion-surface interaction * ion-induced electron emission * angle impact effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.041, year: 2001

  18. Incident ion charge state dependence of electron emission during slow multicharged ion-surface interactions

    International Nuclear Information System (INIS)

    Hughes, I.G.; Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M.; Meyer, F.W.

    1992-01-01

    Characteristic variations in the total electron yield γ as a function of crystal azimuthal orientation are reported for slow N 2+ , N 5+ and N 6+ ions incident on a Au(011) single crystal, together with measurements of γ as a function of incident ion velocity. Kinetic electron emission is shown to arise predominantly in close collisions between incident ions and target atoms, and potential electron emission is found to be essentially constant within our present velocity range. The incident ion charge state is shown to play no role in kinetic electron emission. Extremely fast neutralization times of the order of 10 - 15 secs are needed to explain the observations

  19. Single impacts of keV fullerene ions on free standing graphene: Emission of ions and electrons from confined volume

    Energy Technology Data Exchange (ETDEWEB)

    Verkhoturov, Stanislav V.; Geng, Sheng; Schweikert, Emile A., E-mail: schweikert@chem.tamu.edu [Department of Chemistry, Texas A& M University, College Station, Texas 77843-3144 (United States); Czerwinski, Bartlomiej [Institute of Condensed Matter and Nanosciences–Bio and Soft Matter (IMCN/BSMA), Université Catholique de Louvain, 1 Croix du Sud, B-1348 Louvain-la-Neuve (Belgium); Applied Physics, Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå (Sweden); Young, Amanda E. [Materials Characterization Facility, Texas A& M University, College Station, Texas 77843-3122 (United States); Delcorte, Arnaud [Institute of Condensed Matter and Nanosciences–Bio and Soft Matter (IMCN/BSMA), Université Catholique de Louvain, 1 Croix du Sud, B-1348 Louvain-la-Neuve (Belgium)

    2015-10-28

    We present the first data from individual C{sub 60} impacting one to four layer graphene at 25 and 50 keV. Negative secondary ions and electrons emitted in transmission were recorded separately from each impact. The yields for C{sub n}{sup −} clusters are above 10% for n ≤ 4, they oscillate with electron affinities and decrease exponentially with n. The result can be explained with the aid of MD simulation as a post-collision process where sufficient vibrational energy is accumulated around the rim of the impact hole for sputtering of carbon clusters. The ionization probability can be estimated by comparing experimental yields of C{sub n}{sup −} with those of C{sub n}{sup 0} from MD simulation, where it increases exponentially with n. The ionization probability can be approximated with ejecta from a thermally excited (3700 K) rim damped by cluster fragmentation and electron detachment. The experimental electron probability distributions are Poisson-like. On average, three electrons of thermal energies are emitted per impact. The thermal excitation model invoked for C{sub n}{sup −} emission can also explain the emission of electrons. The interaction of C{sub 60} with graphene is fundamentally different from impacts on 3D targets. A key characteristic is the high degree of ionization of the ejecta.

  20. Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

    International Nuclear Information System (INIS)

    Tierno, S. P.; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L.

    2016-01-01

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime

  1. Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Tierno, S. P., E-mail: sp.tierno@upm.es; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L. [Department of Applied Physics, E.T.S.I. Aeronáutica y del Espacio. Universidad Politécnica de Madrid, 28040 Madrid (Spain)

    2016-01-15

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

  2. Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

    Science.gov (United States)

    Tierno, S. P.; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L.

    2016-01-01

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

  3. Formation of secondary organic aerosol coating on black carbon particles near vehicular emissions

    Science.gov (United States)

    Lee, Alex K. Y.; Chen, Chia-Li; Liu, Jun; Price, Derek J.; Betha, Raghu; Russell, Lynn M.; Zhang, Xiaolu; Cappa, Christopher D.

    2017-12-01

    Black carbon (BC) emitted from incomplete combustion can result in significant impacts on air quality and climate. Understanding the mixing state of ambient BC and the chemical characteristics of its associated coatings is particularly important to evaluate BC fate and environmental impacts. In this study, we investigate the formation of organic coatings on BC particles in an urban environment (Fontana, California) under hot and dry conditions using a soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS was operated in a configuration that can exclusively detect refractory BC (rBC) particles and their coatings. Using the -log(NOx / NOy) ratio as a proxy for photochemical age of air masses, substantial formation of secondary organic aerosol (SOA) coatings on rBC particles was observed due to active photochemistry in the afternoon, whereas primary organic aerosol (POA) components were strongly associated with rBC from fresh vehicular emissions in the morning rush hours. There is also evidence that cooking-related organic aerosols were externally mixed from rBC. Positive matrix factorization and elemental analysis illustrate that most of the observed SOA coatings were freshly formed, providing an opportunity to examine SOA coating formation on rBCs near vehicular emissions. Approximately 7-20 wt % of secondary organic and inorganic species were estimated to be internally mixed with rBC on average, implying that rBC is unlikely the major condensation sink of SOA in this study. Comparison of our results to a co-located standard high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) measurement suggests that at least a portion of SOA materials condensed on rBC surfaces were chemically different from oxygenated organic aerosol (OOA) particles that were externally mixed with rBC, although they could both be generated from local photochemistry.

  4. Electron emission from a double-layer metal under femtosecond laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shuchang; Li, Suyu; Jiang, Yuanfei; Chen, Anmin, E-mail: amchen@jlu.edu.cn; Ding, Dajun; Jin, Mingxing, E-mail: mxjin@jlu.edu.cn

    2015-01-01

    In this paper we theoretically investigate electron emission during femtosecond laser ablation of single-layer metal (copper) and double-layer structures. The double-layer structure is composed of a surface layer (copper) and a substrate layer (gold or chromium). The calculated results indicate that the double-layer structure brings a change to the electron emission from the copper surface. Compared with the ablation of a single-layer, a double-layer structure may be helpful to decrease the relaxation time of the electron temperature, and optimize the electron emission by diminishing the tailing phenomenon under the same absorbed laser fluence. With the increase of the absorbed laser fluence, the effect of optimization becomes significant. This study provides a way to optimize the electron emission which can be beneficial to generate laser induced ultrafast electron pulse sources.

  5. Non-equilibrium thermionic electron emission for metals at high temperatures

    Science.gov (United States)

    Domenech-Garret, J. L.; Tierno, S. P.; Conde, L.

    2015-08-01

    Stationary thermionic electron emission currents from heated metals are compared against an analytical expression derived using a non-equilibrium quantum kappa energy distribution for the electrons. The latter depends on the temperature decreasing parameter κ ( T ) , which decreases with increasing temperature and can be estimated from raw experimental data and characterizes the departure of the electron energy spectrum from equilibrium Fermi-Dirac statistics. The calculations accurately predict the measured thermionic emission currents for both high and moderate temperature ranges. The Richardson-Dushman law governs electron emission for large values of kappa or equivalently, moderate metal temperatures. The high energy tail in the electron energy distribution function that develops at higher temperatures or lower kappa values increases the emission currents well over the predictions of the classical expression. This also permits the quantitative estimation of the departure of the metal electrons from the equilibrium Fermi-Dirac statistics.

  6. Secondary electrons monitor for continuous electron energy measurements in UHF linac

    International Nuclear Information System (INIS)

    Zimek, Zbigniew; Bulka, Sylwester; Mirkowski, Jacek; Roman, Karol

    2001-01-01

    Continuous energy measurements have now became obligatory in accelerator facilities devoted to radiation sterilization process. This is one of several accelerator parameters like dose rate, beam current, bean scan parameters, conveyer speed which must be recorded as it is a required condition of accelerator validation procedure. Electron energy measurements are rather simple in direct DC accelerator, where the applied DC voltage is directly related to electron energy. High frequency linacs are not offering such opportunity in electron energy measurements. The analyzing electromagnet is applied in some accelerators but that method can be used only in off line mode before or after irradiation process. The typical solution is to apply the non direct method related to control and measurements certain accelerator parameters like beam current and microwave energy pulse power. The continuous evaluation of electron energy can be performed on the base of calculation and result comparison with calibration curve

  7. Imaging single atoms using secondary electrons with an aberration-corrected electron microscope.

    Science.gov (United States)

    Zhu, Y; Inada, H; Nakamura, K; Wall, J

    2009-10-01

    Aberration correction has embarked on a new frontier in electron microscopy by overcoming the limitations of conventional round lenses, providing sub-angstrom-sized probes. However, improvement of spatial resolution using aberration correction so far has been limited to the use of transmitted electrons both in scanning and stationary mode, with an improvement of 20-40% (refs 3-8). In contrast, advances in the spatial resolution of scanning electron microscopes (SEMs), which are by far the most widely used instrument for surface imaging at the micrometre-nanometre scale, have been stagnant, despite several recent efforts. Here, we report a new SEM, with aberration correction, able to image single atoms by detecting electrons emerging from its surface as a result of interaction with the small probe. The spatial resolution achieved represents a fourfold improvement over the best-reported resolution in any SEM (refs 10-12). Furthermore, we can simultaneously probe the sample through its entire thickness with transmitted electrons. This ability is significant because it permits the selective visualization of bulk atoms and surface ones, beyond a traditional two-dimensional projection in transmission electron microscopy. It has the potential to revolutionize the field of microscopy and imaging, thereby opening the door to a wide range of applications, especially when combined with simultaneous nanoprobe spectroscopy.

  8. Analysis of recent results of electron cyclotron emission measurements on T.F.R

    International Nuclear Information System (INIS)

    1977-05-01

    Recently reported measurements of the electron cyclotron emission from the TFR Tokamak plasma are analyzed and compared to theoretical predictions. The line shape of an optically thick harmonic in a vertical observation is explained by wall reflections, plasma-detector arrangement and reabsorption. Non thermal emission at the electron plasma frequency is related to the presence of a high energy tail in the electron distribution function and might be the cause of the observed reduced runaway creation rate

  9. White light emission and second harmonic generation from secondary group participation (SGP) in a coordination network.

    Science.gov (United States)

    He, Jun; Zeller, Matthias; Hunter, Allen D; Xu, Zhengtao

    2012-01-25

    We describe a white emitting coordination network solid that can be conveniently applied as a thin film onto a commercial UV-LED lamp for practical white lighting applications. The solid state material was discovered in an exercise of exploring molecular building blocks equipped with secondary groups for fine-tuning the structures and properties of coordination nets. Specifically, CH(3)SCH(2)CH(2)S- and (S)-CH(3)(OH)CHCH(2)S- (2-hydroxylpropyl) were each attached as secondary groups to the 2,5- positions of 1,4-benzenedicarboxylic acid (bdc), and the resultant molecules (L1 and L2, respectively) were crystallized with Pb(II) into the topologically similar 3D nets of PbL1 and PbL2, both consisting of interlinked Pb-carboxyl chains. While the CH(3)S- groups in PbL1 are not bonded to the Pb(II) centers, the hydroxy groups in PbL2 participate in coordinating to Pb(II) and thus modify the bonding features around the Pb(II), but only to a slight and subtle degree (e.g., Pb-O distances 2.941-3.116 Å). Interestingly, the subtle change in structure significantly impacts the properties, i.e., while the photoluminescence of PbL1 is yellowish green, PbL2 features bright white emission. Also, the homochiral side group in PbL2 imparts significant second harmonic generation, in spite of its seemingly weak association with the main framework (the NLO-phore). In a broad perspective, this work showcases the idea of secondary group participation (SGP) in the construction of coordination networks, an idea that parallels that of hemilabile ligands in organometallics and points to an effective strategy in developing advanced functions in solid state framework materials. © 2011 American Chemical Society

  10. Measurements of secondary electron cross sections by the pulsed electron beam time-of-flight method. I. Molecular nitrogen

    International Nuclear Information System (INIS)

    Goruganthu, R.R.; Wilson, W.G.; Bonham, R.A.

    1983-01-01

    The secondary electron cross sections for gaseous molecular nitrogen are reported at ejection angles of 30, 45, 60, 75, 90, 105, 120, 135 and 150 0 , for the energy range 1.5 eV to 20 eV and incident electron energy of 1 keV. The pulsed electron beam time-of-flight methd was employed. The results were placed on an absolute scale by normalization to the elastic scattering. They were compared, where possible, with those reported by Opal, Beaty, and Peterson (OBP). The agreement is somewhat better when the OBP data are divided by 0.53 + 0.47 sintheta as suggested by Rudd and DuBois. Fits of our data by Legendre-polynomial expansions are used to estimate the low-energy portion of the cross-section, dsigma/dE. This work suggests that existing experimental cross sections for secondary electron ejection as a function of angle and ejected energy may be no better known than +-40%, especially in the low energy region. 7 references, 14 figures, 2 tables

  11. Swift heavy ion induced electron emission from solids

    International Nuclear Information System (INIS)

    Rothard, Hermann; Gervais, Benoit; Lanzanò, Gaetano; De Filippo, Enrico; Caron, Michel; Beuve, Michael

    2015-01-01

    We briefly summarize the results of numerous experiments performed at GANIL aimed at measuring electron yields and doubly differential yields (energy or velocity spectra at different ejection angles, angular distributions). These studies, supported by theoretical investigations and numerical simulations, contributed decisively to our understanding of the very first step in energy deposition in matter, i.e. ionization and subsequent electron transport through condensed matter. The emitted electron spectrum contains a rich variety of features including binary encounter electrons (BEE), convoy electrons (CE), Auger electrons (AE) and the low-energy peak of “secondary” electrons (SE). (paper)

  12. Formation of secondary organic aerosols from gas-phase emissions of heated cooking oils

    Directory of Open Access Journals (Sweden)

    T. Liu

    2017-06-01

    Full Text Available Cooking emissions can potentially contribute to secondary organic aerosol (SOA but remain poorly understood. In this study, formation of SOA from gas-phase emissions of five heated vegetable oils (i.e., corn, canola, sunflower, peanut and olive oils was investigated in a potential aerosol mass (PAM chamber. Experiments were conducted at 19–20 °C and 65–70 % relative humidity (RH. The characterization instruments included a scanning mobility particle sizer (SMPS and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS. The efficiency of SOA production, in ascending order, was peanut oil, olive oil, canola oil, corn oil and sunflower oil. The major SOA precursors from heated cooking oils were related to the content of monounsaturated fat and omega-6 fatty acids in cooking oils. The average production rate of SOA, after aging at an OH exposure of 1. 7 × 1011 molecules cm−3 s, was 1. 35 ± 0. 30 µg min−1, 3 orders of magnitude lower compared with emission rates of fine particulate matter (PM2. 5 from heated cooking oils in previous studies. The mass spectra of cooking SOA highly resemble field-derived COA (cooking-related organic aerosol in ambient air, with R2 ranging from 0.74 to 0.88. The average carbon oxidation state (OSc of SOA was −1.51 to −0.81, falling in the range between ambient hydrocarbon-like organic aerosol (HOA and semi-volatile oxygenated organic aerosol (SV-OOA, indicating that SOA in these experiments was lightly oxidized.

  13. Secondary organic aerosol from sesquiterpene and monoterpene emissions in the United States.

    Science.gov (United States)

    Sakulyanontvittaya, Tanarit; Guenther, Alex; Helmig, Detlev; Milford, Jana; Wiedinmyer, Christine

    2008-12-01

    Emissions of volatile organic compounds (VOC) from vegetation are believed to be a major source of secondary organic aerosol (SOA), which in turn comprises a large fraction of fine particulate matter in many areas. Sesquiterpenes are a class of biogenic VOC with high chemical reactivity and SOA yields. Sesquiterpenes have only recently been quantified in emissions from a wide variety of plants. In this study, a new sesquiterpene emission inventory is used to provide input to the Models-3 Community Multiscale Air Quality (CMAQ) model. CMAQ is used to estimate the contribution of sesquiterpenes and monoterpenes to SOA concentrations over the contiguous United States. The gas-particle partitioning module of CMAQ was modified to include condensable products of sesquiterpene oxidation and to update values of the enthalpy of vaporization. The resulting model predicts July monthly average surface concentrations of total SOA in the eastern U.S. ranging from about 0.2-0.8 microg m(-3). This is roughly double the amount of SOA produced in this region when sesquiterpenes are not included. Even with sesquiterpenes included, however, the model significantly underpredicts surface concentrations of particle-phase organic matter compared to observed values. Treating all SOA as capable of undergoing polymerization increases predicted monthly average surface concentrations in July to 0.4-1.2 microg m(-3), in closer agreement with observations. Using the original enthalpy of vaporization value in CMAQ in place of the values estimated from the recent literature results in predicted SOA concentrations of about 0.3-1.3 microg m(-3).

  14. Test beam results of a low-pressure micro-strip gas chamber with a secondary-electron emitter

    International Nuclear Information System (INIS)

    Kwan, S.; Anderson, D.F.; Zimmerman, J.; Sbarra, C.; Salomon, M.

    1994-10-01

    We present recent results, from a beam test, on the angular dependence of the efficiency and the distribution of the signals on the anode strips of a low-pressure microstrip gas chamber with a thick CsI layer as a secondary-electron emitter. New results of CVD diamond films as secondary-electron emitters are discussed

  15. Nitrogen plasma formation through terahertz-induced ultrafast electron field emission

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew

    2015-01-01

    Electron microscopy and electron diffraction techniques rely on electron sources. Those sources require strong electric fields to extract electrons from metals, either by the photoelectric effect, driven by multiphoton absorption of strong laser fields, or in the static field emission regime....... Terahertz (THz) radiation, commonly understood to be nonionizing due to its low photon energy, is here shown to produce electron field emission. We demonstrate that a carrier-envelope phase-stable single-cycle optical field at THz frequencies interacting with a metallic microantenna can generate...... and accelerate ultrashort and ultrabright electron bunches into free space, and we use these electrons to excite and ionize ambient nitrogen molecules near the antenna. The associated UV emission from the gas forms a novel THz wave detector, which, in contrast with conventional photon-counting or heat...

  16. Z1 dependence of ion-induced electron emission from aluminum

    International Nuclear Information System (INIS)

    Alonso, E.V.; Baragiola, R.A.; Ferron, J.; Jakas, M.M.; Oliva-Florio, A.

    1980-01-01

    We have measured the electron emission yields γ of clean aluminum under bombardment with H + , H 2 + , D + , D 2 + , He + , B + , C + , N + , N 2 + , O + , O 2 + , F + , Ne + , S + , Cl + , Ar + , Kr + , and Xe + in the energy range 1.2--50 keV. The clean surfaces were prepared by in situ evaporation of high-purity Al under ultra-high-vacuum conditions. It is found that kinetic electron emission yields γ/sub k/, obtained after subtracting from the measured γ a contribution due to potential emission, are roughly proportional to the electronic stopping powers, for projectiles lighter than Al. For heavier projectiles there is a sizable contribution to electron emission from collisions involving rapidly recoiling target atoms, which increases with the mass of the projectile, and which dominates the threshold and near-threshold behavior of kinetic emission. The results, together with recently reported data on Auger electron emission from ion-bombarded Al show that the mechanism proposed by Parilis and Kishinevskii of inner-shell excitation and subsequent Auger decay is negligible for light ions and probably small for heavy ions on Al and in our energy range. We thus conclude that kinetic electron emission under bombardment by low-energy ions results mainly from the escape of excited valence electrons

  17. Method of synthesizing small-diameter carbon nanotubes with electron field emission properties

    Science.gov (United States)

    Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)

    2009-01-01

    Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.

  18. Proceedings of the 12. Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Heating

    International Nuclear Information System (INIS)

    Giruzzi, Gerardo

    2003-01-01

    The 12. Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Heating was held in Aix-en-Provence (France) from 13 to 16 May 2002. The meeting was hosted by the Association Euratom-CEA sur la Fusion (CEA/Cadarache, France), with additional financial support from: - Region Provence-Alpes Cote d'Azur - The City of Aix-en-Provence - Communaute de l'Agglomeration du Pays d'Aix - Thales Electron Devices (France) - Alstom Magnets and Superconductors (France) - Spinner GmbH (Germany). The members of the local organizing committee were: G. Giruzzi, M. Lennholm, R. Magne and V. Poli, from CEA/Cadarache. The composition of the International Programme Committee was the following: M. Bornatici (Italy), A. Costley (ITER), E. de la Luna (Spain), G. Giruzzi (France), W. Kasparek (Germany), B. Lloyd (UK), J. Lohr (USA), K. Sakamoto (Japan). The subjects of the meeting were classified in four main topics: Electron Cyclotron Theory; Electron Cyclotron Emission; Electron Cyclotron Heating and Current Drive Experiments; Electron Cyclotron Technology. The results presented in these topics have been summarised in the closing session by E. Westerhof, A. Kraemer-Flecken, T. Goodman and G. Bosia, respectively. The workshop was attended by 85 participants from 18 countries, providing 10 invited talks, 30 oral presentations and 50 posters. The success of the workshop is mainly due to the amount and quality of their work and of their presentations. The generosity of the sponsors, the selection and advice work of the International Programme Committee, as well as the contribution of the chairmen and of the summary speakers should also be warmly acknowledged. The papers in this collection have been reproduced directly from the authors' manuscripts, provided either as camera-ready texts or as pdf files. The constraints on the papers lengths and formats have been kept to a minimum, on purpose. This series of workshops has now reached a good level of maturity, with well established

  19. A method to measure the suprathermal density distribution by electron cyclotron emission

    International Nuclear Information System (INIS)

    Tutter, M.

    1986-05-01

    Electron cyclotron emission spectra of suprathermal electrons in a thermal main plasma are calculated. It is shown that for direction of observation oblique to the magnetic field, which decays in direction to the receiver, one may obtain information on the spatial density distribution of the suprathermal electrons from those spectra. (orig.)

  20. Field emission from individual multiwalled carbon nanotubes prepared in an electron microscope

    NARCIS (Netherlands)

    de Jonge, N.; van Druten, N.J.

    2003-01-01

    Individual multiwalled carbon nanotube field emitters were prepared in a scanning electron microscope. The angular current density, energy spectra, and the emission stability of the field-emitted electrons were measured. An estimate of the electron source brightness was extracted from the

  1. Kinetic electron emission from metal surfaces induced by impact of slow ions

    Czech Academy of Sciences Publication Activity Database

    Šroubek, Zdeněk; Lorinčík, Jan

    -, č. 625 (2014), s. 7-9 ISSN 0039-6028 R&D Projects: GA MŠk(CZ) ME10086 Institutional support: RVO:67985882 Keywords : Ion induced kinetic electron emission * Electronic excitation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.925, year: 2014

  2. Secondary-electron-production cross sections for electron-impact ionization of helium

    International Nuclear Information System (INIS)

    Goruganthu, R.R.; Bonham, R.A.

    1986-01-01

    Measurements of the double-differential cross sections (DDCS) as a function of the ejected energy, angle, and primary energy for electron-impact ionization of helium are reported at incident energies of 200, 500, 1000, and 2000 eV. The ejection angle is varied from 30 0 to 150 0 in steps of 15 0 . The cross sections were obtained by use of a crossed-beam apparatus with an effusive gas source and a pulsed electron beam. Scattered and ejected electrons were energy analyzed by time-of-flight analysis from 2 eV to the primary energy as a function of the ejection angle. The relative measurements were normalized by matching the experimental elastic differential cross sections to absolute measurements at selected angles. Comparisons of the DDCS with available literature values revealed significant differences. At 2000 eV impact energy, first-Born-approximation calculations of the DDCS were found to be in agreement with the present data for ejected energies between 2 and 40 eV. At large angles and lower incident energies the Born calculation results are lower than the present DDCS. The DDCS were fitted with a Legendre-polynomial expansion as a function of ejection angle for fixed ejected and primary energies. The energy distributions of ejected electrons derived from these fits are presented and used to calculate the total ionization cross section

  3. Study of the secondary negative ion emission of copper and several of its alloys by impact with Cs+ ions

    International Nuclear Information System (INIS)

    Vallerand, P.; Baril, M.

    1977-01-01

    Secondary ion emission studies have been undertaken using Cs + as the primary ion beam. A good vacuum (ca. 10 -8 torr) is needed to eliminate contamination by residual gases. Negative ion emission of pure copper is compared with its alloys. The thermodynamic equilibrium model of Andersen is discussed. For low element concentrations, the experimental data show enhancement in negative emission of P, Al, Fe, Sn, Ni, and attenuation for Zn, Pb. The order of magnitude of ionic efficiency S - for copper is evaluated at 10 -4 . (Auth.)

  4. Surface potential measurement of negative-ion-implanted insulators by analysing secondary electron energy distribution

    International Nuclear Information System (INIS)

    Toyota, Yoshitaka; Tsuji, Hiroshi; Nagumo, Syoji; Gotoh, Yasuhito; Ishikawa, Junzo; Sakai, Shigeki.

    1994-01-01

    The negative ion implantation method we have proposed is a noble technique which can reduce surface charging of isolated electrodes by a large margin. In this paper, the way to specify the surface potential of negative-ion-implanted insulators by the secondary electron energy analysis is described. The secondary electron energy distribution is obtained by a retarding field type energy analyzer. The result shows that the surface potential of fused quartz by negative-ion implantation (C - with the energy of 10 keV to 40 keV) is negatively charged by only several volts. This surface potential is extremely low compared with that by positive-ion implantation. Therefore, the negative-ion implantation is a very effective method for charge-up free implantation without charge compensation. (author)

  5. Reduction of Secondary Electron Yied (SEY) Figures on Smooth Metallic Surfaces by Means of Magnetic Roughness

    CERN Document Server

    Montero, I; Caspers, F; Mensi, M; Taborelli, M

    2013-01-01

    High secondary electron yield of metallic surfaces used in accelerator and also in space applications is of general concern. In addition to several well-known coating preparation techniques and microscopic or macroscopic mechanical roughness (grooves) which may significantly increase microwave losses the concept of magnetic surface roughness has been proposed recently to lower the effective secondary electron yield (SEY). In this concept a smooth and very good conducting surface with low microwave losses is maintained, but underneath this surface a large number of tiny permanent magnets are located to build a rough magnetic equipotential structure. In this paper we present and discuss measurement of the SEY and the improvement in terms of SEY for different parameter ranges.

  6. Characterization of secondary electron collection for energy recovery from high energy ions with a magnetic field

    International Nuclear Information System (INIS)

    Hagihara, Shota; Wada, Takayuki; Nakamoto, Satoshi; Takeno, Hiromasa; Yasaka, Yasuyoshi; Furuyama, Yuichi; Taniike, Akira

    2015-01-01

    A traveling wave direct energy converter (TWDEC) is expected to be used as an energy recovery device for fast protons produced during the D- 3 He nuclear fusion reaction. Some protons, however, are not fully decelerated and pass through the device. A secondary electron direct energy converter (SEDEC) was proposed as an additional device to recover the protons passing through a TWDEC. In our previous study, magnetic field was applied for efficient secondary electron (SE) collection, but the SEs were reflected close to the collector due to the magnetic mirror effect and the collection was degraded. Herein, a new arrangement of magnets is proposed to be set away from the collector, and experiments in various conditions are performed. An appropriate arrangement away from the collector resulted in the improvement of SE collection. (author)

  7. A photomultiplier-based secondary electron imaging system for a nuclear microprobe

    International Nuclear Information System (INIS)

    Alves, L.C.; Breese, M.B.H.; Silva, M.F. da; Soares, J.C.

    2002-01-01

    The ability to define, or recognise particular regions of interest or surface features is vital to the analysis and interpretation of spatially-resolved images collected with a nuclear microprobe. However, good topographic image contrast is difficult to accomplish using PIXE or RBS images due to their inherent insensitivity to topography, lack of elemental variation or poor statistics. Topographic image contrast is commonly obtained in scanning electron microscopy (SEM) by detecting a large flux of secondary electrons produced by the focused keV electron beam. Similar systems have not been widely used on nuclear microprobes due to ion beam intensity fluctuations, which limit the minimum resolvable contrast and present a major limitation for this technique. This paper describes a secondary electron imaging system which has been developed on the Lisbon microprobe. It is based on a scintillator, a photomultiplier operated in a pulsed mode, a pulse shaping electronic chain and ADC, and requires no changes to the existing data acquisition system. Examples of the images obtained from materials such as patterned SiGe wafers and hydrogen-implanted silicon are given, and compared with SEM or optical images

  8. Electron field emission from screen-printed graphene/DWCNT composite films

    International Nuclear Information System (INIS)

    Xu, Jinzhuo; Pan, Rong; Chen, Yiwei; Piao, Xianqin; Qian, Min; Feng, Tao; Sun, Zhuo

    2013-01-01

    Highlights: ► The field emission performance improved significantly when adding graphene into DWCNTs as the emission material. ► We set up a model of pure DWCNT films and graphene/DWCNT composite films. ► We discussed the contact barrier between emission films and electric substrates by considering the Fermi energies of silver, DWCNT and graphene. - Abstract: The electron field emission properties of graphene/double-walled carbon nanotube (DWCNT) composite films prepared by screen printing have been systematically studied. Comparing with the pure DWCNT films and pure graphene films, a significant enhancement of electron emission performance of the composite films are observed, such as lower turn-on field, higher emission current density, higher field enhancement factor, and long-term stability. The optimized composite films with 20% weight ratio of graphene show the best electron emission performance with a low turn-on field of 0.62 V μm −1 (at 1 μA cm −2 ) and a high field enhancement factor β of 13,000. A model of the graphene/DWCNT composite films is proposed, which indicate that a certain amount of graphene will contribute the electron transmission in the silver substrate/composite films interface and in the interior of composite films, and finally improve the electron emission performance of the graphene/DWCNT composite films.

  9. Study of electronic field emission from large surfaces under static operating conditions and hyper-frequency

    International Nuclear Information System (INIS)

    Luong, M.

    1997-09-01

    The enhanced electronic field emission from large area metallic surfaces lowers performances of industrial devices that have to sustain high electric field under vacuum. Despite of numerous investigations in the past, the mechanisms of such an emission have never been well clarified. Recently, research in our laboratory has pointed out the importance played by conducting sites (particles and protrusions). A refined geometrical model, called superposed protrusions model has been proposed to explain the enhanced emission by local field enhancement. As a logical continuation, the present work aims at testing this model and, in the same time, investigating the means to suppress the emission where it is undesirable. Thus, we have showed: the cause of current fluctuations in a continuous field regime (DC), the identity of emission characteristics (β, A e ) in both radiofrequency (RF) and DC regimes, the effectiveness of a thermal treatment by extern high density electronic bombardment, the effectiveness of a mechanical treatment by high pressure rinsing with ultra pure water, the mechanisms and limits of an in situ RF processing. Furthermore, the electronic emission from insulating particles has also been studied concurrently with a spectral analysis of the associated luminous emission. Finally, the refined geometrical model for conducting sites is reinforced while another model is proposed for some insulating sites. Several emission suppressing treatments has been explored and validated. At last, the characteristic of a RF pulsed field emitted electron beam has been checked for the first time as a possible application of such a field emission. (author)

  10. Development of fountain detectors for spectroscopy of secondary electron in SEM

    Energy Technology Data Exchange (ETDEWEB)

    Agemura, Toshihide [University of Tsukuba (Japan); Iwai, Hideo [National Institute for Materials Science, Tsukuba (Japan); Sekiguchi, Takashi [University of Tsukuba (Japan); National Institute for Materials Science, Tsukuba (Japan)

    2017-07-15

    To image the variation of surface potential in semiconductors, energy selective secondary electron detector, named fountain detector (FD), was developed. Two types of grids, planar and spherical, were designed and the superiority of latter was demonstrated. The p-n junction of 4H-SiC was observed using spherical FD and the image was much clear than that using conventional detector. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Photon emission induced by impact of electrons on molecules

    International Nuclear Information System (INIS)

    Sprang, H.A. van.

    1980-01-01

    The author discusses both the history and the present state of emission spectroscopy and presents several previously published papers giving experimental data on some diatomic molecules and for chloro-fluoro methanes. (G.T.H.)

  12. Accumulation of selected elements in the pharyngeal tonsils of children as a result of secondary dust emission

    Directory of Open Access Journals (Sweden)

    Maria Gerycka

    2014-09-01

    Full Text Available Background. The aim of the study was to determine the influence of secondary dust and car emission on the intoxication of adenoids. Material and methods. The amount of Pb, Be, Ba, Ca, Mg and Sr in pharyngeal tonsils of children living in Tychy (n 86, and in Chorzów (n 76 as well as the amount of the selected elements in suspended dust was determined by the ICP – AES method. The biological material had previously been subjected to mineralization using of nitric acid (V spectrally pure Merck. Results. Secondary emission as a potential additional source of trace elements in tonsils is described by secondary emission coefficient and by the additional weight of the metal present in general air pollution. Conclusions. The degree of accumulation of analyzed elements in the adenoid tissue mostly depends on the content of these elements in soluble form in suspended dust in the ground layer of air, as a result of secondary and car emissions.

  13. Investigation of pyroelectric electron emission from monodomain lithium niobate single crystals

    International Nuclear Information System (INIS)

    Bourim, El Mostafa; Moon, Chang-Wook; Lee, Seung-Woon; Kyeong Yoo, In

    2006-01-01

    The behaviors of thermally stimulated electron emission from pyroelectric monodomain lithium niobate single crystal (LiNbO 3 ) were investigated by utilizing a Si p-n junction photodiode as electron detector and a receptive electron beam resist (E-beam resist) as electron collector. In high vacuum (10 -6 Torr), the pyroelectric electron emission (PEE) was found to depend on the exposed emitting polar crystal surface (+Z face or -Z face) and was significantly influenced by the emitter-electron receiver gap distances. Thus, the PEE from +Z face was detected during heating and was activated, in small gaps ( 2 mm) the emission was simply mastered by field emission effect. Whereas, The PEE from -Z face was detected during cooling and was solely due to the field ionization effect. Therewith, for small gaps ( 2 mm) PEE was governed by field ionization generating a soft and continuous plasma ambient atmosphere. Significant decrease of electron emission current was observed from +Z face after successive thermal cycles. A fast and fully emission recovery was established after a brief exposure of crystal to a poor air vacuum of 10 -1 Torr

  14. Effect of velocity variation on secondary-ion-emission probability: Quantum stationary approach

    International Nuclear Information System (INIS)

    Goldberg, E.C.; Ferron, J.; Passeggi, M.C.G.

    1989-01-01

    The ion-velocity dependence of the ionization probability for an atom ejected from a surface is examined by using a quantum approach in which the coupled motion between electrons and the outgoing nucleus is followed along the whole trajectory by solving the stationary Schroedinger equation. We choose a very-small-cluster-model system in which the motion of the atom is restricted to one dimension, and with energy potential curves corresponding to the involved channels varying appreciably with the atom position. We found an exponential dependence on the inverse of the asymptotic ion velocity for high emission energies, and a smoother behavior with slight oscillations at low energies. These results are compared with those obtained within a dynamical-trajectory approximation using either a constant velocity equal to the asymptotic ionic value, or expressions for the velocity derived from the eikonal approximation and from the classical limit of the current vector. Both approaches give similar results provided the velocity is allowed to adjust self-consistently to potential energies and transition-amplitude variations. Strong oscillations are observed in the low-emission-energy range either if the transitions are neglected, or a constant velocity along the whole path is assumed for the ejected particle

  15. SU-E-J-149: Secondary Emission Detection for Improved Proton Relative Stopping Power Identification

    Energy Technology Data Exchange (ETDEWEB)

    Saunders, J; Musall, B; Erickson, A [Georgia Institute of Technology, Atlanta, GA (Georgia)

    2015-06-15

    Purpose: This research investigates application of secondary prompt gamma (PG) emission spectra, resulting from nuclear reactions induced by protons, to characterize tissue composition along the particle path. The objective of utilizing the intensity of discrete high-energy peaks of PG is to improve the accuracy of relative stopping power (RSP) values available for proton therapy treatment planning on a patient specific basis and to reduce uncertainty in dose depth calculations. Methods: In this research, MCNP6 was used to simulate PG emission spectra generated from proton induced nuclear reactions in medium of varying composition of carbon, oxygen, calcium and nitrogen, the predominant elements found in human tissue. The relative peak intensities at discrete energies predicted by MCNP6 were compared to the corresponding atomic composition of the medium. Results: The results have shown a good general agreement with experimentally measured values reported by other investigators. Unexpected divergence from experimental spectra was noted in the peak intensities for some cases depending on the source of the cross-section data when using compiled proton table libraries vs. physics models built into MCNP6. While the use of proton cross-section libraries is generally recommended when available, these libraries lack data for several less abundant isotopes. This limits the range of their applicability and forces the simulations to rely on physics models for reactions with natural atomic compositions. Conclusion: Current end-of-range proton imaging provides an average RSP for the total estimated track length. The accurate identification of tissue composition along the incident particle path using PG detection and characterization allows for improved determination of the tissue RSP on the local level. While this would allow for more accurate depth calculations resulting in tighter treatment margins, precise understanding of proton beam behavior in tissue of various

  16. Secondary-electron-production cross sections for electron-impact ionization of molecular nitrogen

    International Nuclear Information System (INIS)

    Goruganthu, R.R.; Wilson, W.G.; Bonham, R.A.

    1987-01-01

    Measurements of the double-differential cross section (DDCS), as a function of the ejected energy, angle, and primary energy for electron-impact ionization of molecular nitrogen are reported at incident energies of 200, 500, 1000, and 2000 eV. The ejection angle was varied from 30 0 to 150 0 in steps of 15 0 . The cross sections were obtained by use of a crossed-beam apparatus with an effusive gas source and a pulsed electron beam. Scattered and ejected electrons were energy analyzed by time-of-flight analysis from below 2 eV to the primary energy. The relative measurements were placed on an absolute scale by matching the experimental elastic differential cross sections to absolute measurements at each primary energy. Comparisons of the DDCS with previous reported values revealed significant differences. The DDCS were fitted to a Legendre polynomial expansion as a function of the ejection angle. Platzman plot analysis was carried out on the energy distributions determined from the fit coefficients. The total ionization cross sections at these primary energies were deduced from this plot. An autoionization feature at 2.3 eV was observed for the first time in measurements of this nature and has been assigned as due to a Rydberg state converging to the B 2 Σ/sub u/ + ionic state which decays to the X 2 Σ/sub g/ + ground state of N 2 + . An analysis of the autoionization lines observed in the present work in the range 0.4--2.5 eV is also presented

  17. Secondary mineralization in carious lesions of human dentin. Electron-probe, electron microscope, and electron diffraction studies

    Energy Technology Data Exchange (ETDEWEB)

    Ogiwara, H [Tokyo Dental Coll. (Japan)

    1975-02-01

    Dentinal carious lesions having a remineralized surface layer were studied by means electron-probe microanalysis, electron microscopy, electron diffraction. As the results of electron-probe study, F, Mg, and Na were found to be distributed mainly in the remineralized surface layer and S in the decalcified region where decreases in Ca, P, and Mg concentration were usually observed. The decrease in Mg concentration always started earlier than that of Ca and P concentration. Electron microscope and electron diffraction studies revealed that apatic crystals in the remineralized surface layer were much larger than those in the intact dentin. Although they were less conspicuous, crystals in the decalcified region also were larger than those in the intact region. Dentinal tubules, occluded by many crystals, were frequently seen during the observations. Crystals in the tubules varied in morphology, showing granular, needle, rhomboid, and tabular shapes. By means of electron diffraction, the granular- or needle-shaped crystals were identified as apatite and the rhomboid-shaped crystals as whitlockite. Some of the tabular-shaped crystals appeared to be cotacalcium phosphate.

  18. Emission properties of aluminium-lithium alloy

    International Nuclear Information System (INIS)

    Bondarenko, G.G.; Shishkov, A.V.

    1995-01-01

    High secondary emission properties at comparatively low operation temperatures were obtained when investigating aluminum-lithium alloy Al - 2.2 mass % Li. The maximal value of the coefficient of secondary electron emission for alloy, activated under optimal conditions, is achieved at comparatively low energy of primary electrons, equal to 600 eV. Low value of the first critical potential (15 ± 2 eV) was obtained. It is important for operation of secondary emission cathodes. 12 refs.; 4 figs

  19. Generalized formula for electron emission taking account of the polaron effect

    Science.gov (United States)

    Barengolts, Yu A.; Beril, S. I.; Barengolts, S. A.

    2018-01-01

    A generalized formula is derived for the electron emission current as a function of temperature, field, and electron work function in a metal-dielectric system that takes account of the quantum nature of the image forces. In deriving the formula, the Fermi-Dirac distribution for electrons in a metal and the quantum potential of the image obtained in the context of electron polaron theory are used.

  20. Ion emission from laser-produced plasmas with two electron temperatures

    International Nuclear Information System (INIS)

    Wickens, L.M.; Allen, J.E.; Rumsby, P.T.

    1978-01-01

    An analytic theory for the expansion of a laser-produced plasma with two electron temperatures is presented. It is shown that from the ion-emission velocity spectrum such relevant parameters as the hot- to -cold-electron density ratio, the absolute hot- and cold-electron temperatures, and a sensitive measure of hot- and cold-electron temperature ratio can be deduced. A comparison with experimental results is presented