WorldWideScience

Sample records for polarized electron probes

  1. The Utilization of Spin Polarized Photoelectron Spectroscopy as a Probe of Electron Correlation with an Ultimate Goal of Pu

    International Nuclear Information System (INIS)

    Tobin, James; Yu, Sung; Chung, Brandon; Morton, Simon; Komesu, Takashi; Waddill, George

    2008-01-01

    We are developing the technique of spin-polarized photoelectron spectroscopy as a probe of electron correlation with the ultimate goal of resolving the Pu electronic structure controversy. Over the last several years, we have demonstrated the utility of spin polarized photoelectron spectroscopy for determining the fine details of the electronic structure in complex systems such as those shown in the paper.

  2. Polarization-dependent pump-probe studies in atomic fine-structure levels: towards the production of spin-polarized electrons

    International Nuclear Information System (INIS)

    Sokell, E.; Zamith, S.; Bouchene, M.A.; Girard, B.

    2000-01-01

    The precession of orbital and spin angular momentum vectors has been observed in a pump-probe study of the 4P fine-structure states of atomic potassium. A femtosecond pump pulse prepared a coherent superposition of the two fine-structure components. A time-delayed probe pulse then ionized the system after it had been allowed to evolve freely. Oscillations recorded in the ion signal reflect the evolution of the orientation of the orbital and spin angular momentum due to spin-orbit coupling. This interpretation gives physical insight into the cause of the half-period phase shift observed when the relative polarizations of the laser pulses were changed from parallel to perpendicular. Finally, it is shown that these changes in the orientation of the spin momentum vector of the system can be utilized to produce highly spin-polarized free electrons on the femtosecond scale. (author)

  3. Probing the 4p electron-spin polarization in NiO

    International Nuclear Information System (INIS)

    Neubeck, W.; Vettier, C.; Bergevin, F. de; Yakhou, F.; Mannix, D.; Bengone, O.; Alouani, M.; Barbier, A.

    2001-01-01

    K-edge resonant x-ray magnetic scattering experiments have been performed on antiferromagnetic NiO. The observation of two resonances at the K edge allows the construction of models to compare the electronic properties of NiO and the observed resonant magnetic x-ray scattering. From the polarization analysis of the scattered beam, a quadrupolar transition (1s-3d) and a dipolar transition (1s-4p) are identified. While the quadrupolar transition can be modeled using an atomic picture for the 3d electrons, the dipolar transition is associated to a broadband structure of p electrons and its energy profile is compared to electronic band-structure calculations

  4. Molecular frame photoemission: a probe of electronic/nuclear photo-dynamics and polarization state of the ionizing light

    International Nuclear Information System (INIS)

    Veyrinas, Kevin

    2015-01-01

    This is thesis is dedicated to the study and the use of the remarkable properties of the molecular frame photoelectron angular distribution (MFPAD). This observable is a very sensitive probe of both the photoionization (PI) processes in small molecules, through the determination of the magnitudes and relative phases of the dipole matrix elements, and the polarization state of the ionizing light, which is entirely encoded in the MFPAD in terms of the Stokes parameters (s1, s2, s3). MFPAD measurements take advantage of dissociative photoionization (DPI) processes by combining an electron-ion 3D momentum spectroscopy technique with the use of different radiation facilities: SOLEIL synchrotron (DESIRS and PLEIADES beamlines) and the XUV PLFA beamline (SLIC, LIDyL Attophysics group, CEA Saclay) based on the interaction of a strong laser field with a gaseous target called high harmonic generation (HHG). The first part of the thesis is devoted to the complete characterization of the polarization state of an incoming radiation. In this context, an original 'molecular polarimetry' method is introduced and demonstrated by comparison with a VUV optical polarimeter available on the DESIRS beamline. Using this method to determine the full polarization ellipse of HHG radiation generated in different conditions on the XUV PLFA facility leads to original results that include the challenging disentanglement of the circular and unpolarized components of the studied radiation. The second part deals with the study of DPI of the H 2 , D 2 and HD molecules induced by circularly polarized light at resonance with the doubly excited states Q1 and Q2. In this energy region (30-35 eV) where direct ionization, autoionization and dissociation compete on a femtosecond timescale, the photonic excitation gives rise to complex ultrafast electronic and nuclear coupled dynamics. The remarkable asymmetries observed in the circular dichroism in the molecular frame, compared to quantum

  5. Polarization dependence in ELNES: Influence of probe convergence, collector aperture and electron beam incidence angle

    International Nuclear Information System (INIS)

    Le Bosse, J.C.; Epicier, T.; Jouffrey, B.

    2006-01-01

    The differential scattering cross section in electron energy loss near edge spectroscopy (ELNES) generally depends on the orientation of the Q wave vector transferred from the incident electron to an atomic core electron. In the case where the excited atom belongs to a threefold, fourfold or sixfold main rotation axis, the dipole cross section depends on the angle of Q with respect to this axis. In this paper, we restrict to this situation called dichroism. Furthermore, if we take into account the relativistic effects due to the high incident electron velocity, this dipole cross section also depends on the angle of Q with respect to the electron beam axis. It is due to these dependences that the shape of measured electron energy loss spectra varies with the electron beam incidence, the collector aperture, the incident beam convergence and the incident electron energy. The existence of a particular beam incidence angle for which the scattering cross section becomes independent of collection and beam convergence semi-angles is clearly underscored. Conversely, it is shown that EELS spectra do not depend on the beam incidence angle for a set of particular values of collection and convergence semi-angles. Particularly, in the case of a parallel incident beam, there is a collection semi-angle (often called magic angle) for which the cross section becomes independent of the beam orientation. This magic angle depends on the incident beam kinetic energy. If the incident electron velocity V is small compared with the light velocity c, this magic angle is about 3.975θ E (θ E is the scattering angle). It decreases to 0 when V approaches c. These results are illustrated in the case of the K boron edge in the boron nitride

  6. Polarized electron sources

    International Nuclear Information System (INIS)

    Prepost, R.

    1994-01-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented

  7. Polarized electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Prepost, R. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented.

  8. Physics with polarized electron beams

    International Nuclear Information System (INIS)

    Swartz, M.L.

    1988-01-01

    As a distinct field, elementary particle physics is now approximately forty years old. In all that time, only a few of the thousands of experiments that have been performed have made use of spin polarized particle beams (with apologies to those who have studied neutrino interactions, polarized beam are defined to refer to the case in which the experimenter has control over the polarization direction). If the discussion is restricted to spin polarized electron beams, the number of experiments becomes countable with the fingers of one hand (with several to spare). There are two reasons for this lack of interest. The first is that spin polarized beams are difficult to produce, accelerate, and transport. The second reason is that any physical process that can occur during the collision of a polarized particle with another (polarized or not) can also occur during the collision of unpolarized particles. One might ask then, why has any effort been expended on the subject. The answer, at least in the case of polarized electron beams, is that electron accelerators and storage rings have in recent years achieved sufficient energy to begin to probe the weak interaction directly. The weak interaction distinguishes between left- and right-handed fermionic currents. Left-handed particles interact in a fundamentally different way than their right-handed counterparts. If the experimenter wishes to explore or exploit this difference, he (or she) must either prepare the spin state of the incident particles or analyze the spin state of outgoing particles. For reasons of genearlity and improved statistical precision, the former is usually preferable to the latter. The first of these lectures will review some of the techniques necessary for the production, transport, and monitoring of polarized electron (or positron) beams. The second lecture will survey some of the physics possibilities of polarized electron-positron collisions

  9. Direct Probes of Linearly Polarized Gluons inside Unpolarized Hadrons

    NARCIS (Netherlands)

    Boer, D.; Brodsky, S. J.; Mulders, P.J.G.; Pisano, C.

    2011-01-01

    We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos2 asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized

  10. Physics with polarized electron beams

    International Nuclear Information System (INIS)

    Swartz, M.L.

    1988-06-01

    As a distinct field, elementary particle physics is now approximately forty years old. In all that time, only a few of the thousands of experiments that have been performed have made use of spin polarized particle beams. There are two reasons for this lack of interest. The first is that spin polarized beams are difficult to produce, accelerate, and transport. The second reason is that any physical process that can occur during the collision of a polarized particle with another (polarized or not) can also occur during the collision of unpolarized particles. One might ask then, why has any effort been expended on the subject? The answer, at least in the case of polarized electron beams, is that electron accelerators and storage rings have in recent years achieved sufficient energy to begin to probe the weak interaction directly. The weak interaction distinguishes between left- and right-handed fermionic currents. Left-handed particles interact in a fundamentally different way than their right-handed counterparts. If the experimenter wishes to explore or exploit this difference, he (or she) must either prepare the spin state of the incident particles or analyze the spin state of outgoing particles. For reasons, of generality and improved statistical precision, the former is usually preferable to the latter. The first of these lectures will review some of the techniques necessary for the production, transport, and monitoring of polarized electron (or positron) beams. The second lecture will survey some of the physics possibilities of polarized electron--positron collisions. 33 refs., 26 figs., 5 tabs

  11. Polarized electron sources

    International Nuclear Information System (INIS)

    Clendenin, J.E.

    1995-05-01

    Polarized electron sources for high energy accelerators took a significant step forward with the introduction of a new laser-driven photocathode source for the SLC in 1992. With an electron beam polarization of >80% and with ∼99% uptime during continuous operation, this source is a key factor in the success of the current SLC high-energy physics program. The SLC source performance is used to illustrate both the capabilities and the limitations of solid-state sources. The beam requirements for future colliders are similar to that of the SLC with the addition in most cases of multiple-bunch operation. A design for the next generation accelerator source that can improve the operational characteristics and at least minimize some of the inherent limitations of present sources is presented. Finally, the possibilities for producing highly polarized electron beams for high-duty-factor accelerators are discussed

  12. Source of spin polarized electrons

    International Nuclear Information System (INIS)

    Pierce, D.T.; Meier, F.A.; Siegmann, H.C.

    1976-01-01

    A method is described of producing intense beams of polarized free electrons in which a semiconductor with a spin orbit split valence band and negative electron affinity is used as a photocathode and irradiated with circularly polarized light

  13. Polarized electrons at Jefferson laboratory

    International Nuclear Information System (INIS)

    Sinclair, C.K.

    1998-01-01

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously. Initial operational experience with the polarized source will be presented. copyright 1998 American Institute of Physics

  14. Polarized Electrons at Jefferson Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, C.K.

    1997-12-31

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously.initial operational experience with the polarized source will be presented.

  15. Using polarized positrons to probe physics beyond the standard model

    Science.gov (United States)

    Furletova, Yulia; Mantry, Sonny

    2018-05-01

    A high intensity polarized positron beam, as part of the JLAB 12 GeV program and the proposed electron-ion collider (EIC), can provide a unique opportunity for testing the Standard Model (SM) and probing for new physics. The combination of high luminosity with polarized electrons and positrons incident on protons and deuterons can isolate important effects and distinguish between possible new physics scenarios in a manner that will complement current experimental efforts. A comparison of cross sections between polarized electron and positron beams will allow for an extraction of the poorly known weak neutral current coupling combination 2C3u - C3d and would complement the proposed plan for a precision extraction of the combination 2C2u - Cd at the EIC. Precision measurements of these neutral weak couplings would constrain new physics scenarios including Leptoquarks, R-parity violating supersymmetry, and electron and quark compositeness. The dependence of the charged current cross section on the longitudinal polarization of the positron beam will provide an independent probe to test the chiral structure of the electroweak interactions. A polarized positron can probe charged lepton flavor violation (CLFV) through a search for e+ → τ+ transitions in a manner that is independent and complementary to the proposed e- → τ- search at the EIC. A positron beam incident on an electron in a stationary nuclear target will also allow for a dark-photon (A') search via the annihilation process e+ + e- → A' + γ.

  16. Electronic state of PuCoGa5 and NpCoGa5 as probed by polarized neutrons.

    Science.gov (United States)

    Hiess, A; Stunault, A; Colineau, E; Rebizant, J; Wastin, F; Caciuffo, R; Lander, G H

    2008-02-22

    By using single crystals and polarized neutrons, we have measured the orbital and spin components of the microscopic magnetization in the paramagnetic state of NpCoGa(5) and PuCoGa(5). The microscopic magnetization of NpCoGa(5) agrees with that observed in bulk susceptibility measurements and the magnetic moment has spin and orbital contributions as expected for intermediate coupling. In contrast, for PuCoGa(5), which is a superconductor with a high transition temperature, the microscopic magnetization in the paramagnetic state is small, temperature-independent, and significantly below the value found with bulk techniques at low temperatures. The orbital moment dominates the magnetization.

  17. The SLAC polarized electron source

    International Nuclear Information System (INIS)

    Clendenin, J.E.; Alley, R.; Frisch, J.; Kotseroglou, T.; Mulhollan, G.; Schultz, D.; Tang, H.; Turner, J.; Yeremian, A.D.

    1997-08-01

    Since 1992, the SLAC 3-km linac has operated exclusively with polarized electrons. The polarized electron source is highly reliable, remotely operated and monitored, and able to produce a variety of electron bunch profiles for high-energy physics experiments. The source and its operating characteristics are described. Some implications drawn from the operating experience are discussed

  18. Probing of flowing electron plasmas

    International Nuclear Information System (INIS)

    Himura, H.; Nakashima, C.; Saito, H.; Yoshida, Z.

    2001-01-01

    Probing of streaming electron plasmas with finite temperature is studied. For the first time, a current-voltage characteristic of an electric probe is measured in electron plasmas. Due to the fast flow of the electron plasmas, the characteristic curve spreads out significantly and exhibits a long tail. This feature can be explained calculating the currents collected to the probe. In flowing electron plasmas, the distribution function observed in the laboratory frame is non-Maxwellian even if the plasmas come to a state of thermal equilibrium. Another significant feature of the characteristic is that it determines a floating potential where the current equals zero, despite there being very few ions in the electron plasma. A high impedance probe, which is popularly used to determine the space potential of electron plasmas, outputs the potential. The method is available only for plasmas with density much smaller than the Brillouin limit

  19. High energy polarized electron beams

    International Nuclear Information System (INIS)

    Rossmanith, R.

    1987-01-01

    In nearly all high energy electron storage rings the effect of beam polarization by synchrotron radiation has been measured. The buildup time for polarization in storage rings is of the order of 10 6 to 10 7 revolutions; the spins must remain aligned over this time in order to avoid depolarization. Even extremely small spin deviations per revolution can add up and cause depolarization. The injection and the acceleration of polarized electrons in linacs is much easier. Although some improvements are still necessary, reliable polarized electron sources with sufficiently high intensity and polarization are available. With the linac-type machines SLC at Stanford and CEBAF in Virginia, experiments with polarized electrons will be possible

  20. The SLAC polarized electron source

    International Nuclear Information System (INIS)

    Tang, H.; Alley, R.; Frisch, J.

    1995-06-01

    The SLAC polarized electron source employs a photocathode DC high voltage gun with a loadlock and a YAG pumped Ti:sapphire laser system for colliding beam experiments or a flash lamp pumped Ti:sapphire laser for fixed target experiments. It uses a thin, strained GaAs(100) photocathode, and is capable of producing a pulsed beam with a polarization of ≥80% and a peak current exceeding 10 A. Its operating efficiency has reached 99%. The physics and technology of producing high polarization electron beams from a GaAs photocathode will be reviewed. The prospects of realizing a polarized electron source for future linear colliders will also be discussed

  1. Polarized Electrons for Linear Colliders

    International Nuclear Information System (INIS)

    Clendenin, J.

    2004-01-01

    Future electron-positron linear colliders require a highly polarized electron beam with a pulse structure that depends primarily on whether the acceleration utilizes warm or superconducting rf structures. The International Linear Collider (ILC) will use cold structures for the main linac. It is shown that a dc-biased polarized photoelectron source such as successfully used for the SLC can meet the charge requirements for the ILC micropulse with a polarization approaching 90%

  2. Probing Anomalous WW γ and WWZ Couplings with Polarized Electron Beam at the LHeC and FCC-Ep Collider

    CERN Document Server

    Turk Cakir, I; Tasci, A T; Cakir, O

    2016-01-01

    We study the anomalous WWγ and WWZ couplings by calculating total cross sections of two processes at the LHeC with electron beam energy Ee=140 GeV and the proton beam energy Ep=7 TeV, and at the FCC-ep collider with the polarized electron beam energy Ee=80 GeV and the proton beam energy Ep=50 TeV. At the LHeC with electron beam polarization, we obtain the results for the difference of upper and lower bounds as (0.975, 0.118) and (0.285, 0.009) for the anomalous (∆κγ, λγ) and (∆κz, λz) couplings, respectively. As for FCC-ep collider, these bounds are obtained as (1.101, 0.065) and (0.320, 0.002) at an integrated luminosity of Lint=100 fb-1.

  3. Probing CPT violation with CMB polarization measurements

    Energy Technology Data Exchange (ETDEWEB)

    Xia Junqing, E-mail: xia@sissa.i [Scuola Internazionale Superiore di Studi Avanzati, Via Beirut 2-4, I-34014 Trieste (Italy); Li Hong; Zhang Xinmin [Institute of High Energy Physics, Chinese Academy of Science, P.O. Box 918-4, Beijing 100049 (China); Theoretical Physics Center for Science Facilities (TPCSF), Chinese Academy of Science (China)

    2010-04-12

    The electrodynamics modified by the Chern-Simons term L{sub cs}approxp{sub m}uA{sub n}uF-tilde{sup m}u{sup n}u with a non-vanishing p{sub m}u violates the Charge-Parity-Time Reversal symmetry (CPT) and rotates the linear polarizations of the propagating Cosmic Microwave Background (CMB) photons. In this Letter we measure the rotation angle DELTAalpha by performing a global analysis on the current CMB polarization measurements from the five-year Wilkinson Microwave Anisotropy Probe (WMAP5), BOOMERanG 2003 (B03), BICEP and QUaD using a Markov Chain Monte Carlo method. Neglecting the systematic errors of these experiments, we find that the results from WMAP5, B03 and BICEP all are consistent and their combination gives DELTAalpha=-2.62+-0.87deg (68% C.L.), indicating a 3sigma detection of the CPT violation. The QUaD data alone gives DELTAalpha=0.59+-0.42deg (68% C.L.) which has an opposite sign for the central value and smaller error bar compared to that obtained from WMAP5, B03 and BICEP. When combining all the polarization data together, we find DELTAalpha=0.09+-0.36deg (68% C.L.) which significantly improves the previous constraint on DELTAalpha and test the validity of the fundamental CPT symmetry at a higher level.

  4. High current polarized electron source

    Science.gov (United States)

    Suleiman, R.; Adderley, P.; Grames, J.; Hansknecht, J.; Poelker, M.; Stutzman, M.

    2018-05-01

    Jefferson Lab operates two DC high voltage GaAs photoguns with compact inverted insulators. One photogun provides the polarized electron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) up to 200 µA. The other gun is used for high average current photocathode lifetime studies at a dedicated test facility up to 4 mA of polarized beam and 10 mA of un-polarized beam. GaAs-based photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed facilities that must operate in excess of tens of mA of polarized average current. This contribution describes techniques to maintain good vacuum while delivering high beam currents, and techniques that minimize damage due to ion bombardment, the dominant mechanism that reduces photocathode yield. Advantages of higher DC voltage include reduced space-charge emittance growth and the potential for better photocathode lifetime. Highlights of R&D to improve the performance of polarized electron sources and prolong the lifetime of strained-superlattice GaAs are presented.

  5. High Intensity Polarized Electron Sources

    International Nuclear Information System (INIS)

    Poelker, Benard; Adderley, Philip; Brittian, Joshua; Clark, J.; Grames, Joseph; Hansknecht, John; McCarter, James; Stutzman, Marcy; Suleiman, Riad; Surles-law, Kenneth

    2008-01-01

    During the 1990s, at numerous facilities world wide, extensive RandD devoted to constructing reliable GaAs photoguns helped ensure successful accelerator-based nuclear and high-energy physics programs using spin polarized electron beams. Today, polarized electron source technology is considered mature, with most GaAs photoguns meeting accelerator and experiment beam specifications in a relatively trouble-free manner. Proposals for new collider facilities however, require electron beams with parameters beyond today's state-of-the-art and serve to renew interest in conducting polarized electron source RandD. And at CEBAF/Jefferson Lab, there is an immediate pressing need to prepare for new experiments that require considerably more beam current than before. One experiment in particular?Q-weak, a parity violation experiment that will look for physics beyond the Standard Model?requires 180 uA average current at polarization >80% for a duration of one year, with run-averaged helicity correlate

  6. The SLC polarized electron source

    International Nuclear Information System (INIS)

    Clendenin, J.E.

    1990-10-01

    A polarized electron source consisting of a 3-electrode photocathode gun and a flashlamp-pumped dye laser has been designed and built for the SLC and is currently undergoing commissioning. The source is described, and the operating configuration is discussed. The present status of the source and future plans are briefly indicated. 7 refs., 4 figs

  7. Probing Xe electronic structure by two-color HHG

    International Nuclear Information System (INIS)

    Faccialà, D; Ciriolo, A G; De Silvestri, S; Devetta, M; Negro, M; Stagira, S; Vozzi, C; Pabst, S; Bruner, B D; Dudovich, N; Soifer, H

    2015-01-01

    The aim of this study is probing the multi-electron behavior in xenon by two-color driven high harmonic generation. By changing the relative polarization of the two colors we were able to study different aspects of the multi-electron response. (paper)

  8. Polarization in free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Papadichev, V.A. [Lebedev Physical Institute, Moscow (Russian Federation)

    1995-12-31

    Polarization of electromagnetic radiation is required very often in numerous scientific and industrial applications: studying of crystals, molecules and intermolecular interaction high-temperature superconductivity, semiconductors and their transitions, polymers and liquid crystals. Using polarized radiation allows to obtain important data (otherwise inaccessible) in astrophysics, meteorology and oceanology. It is promising in chemistry and biology for selective influence on definite parts of molecules in chain synthesis reactions, precise control of various processes at cell and subcell levels, genetic engineering etc. Though polarization methods are well elaborated in optics, they can fail in far-infrared, vacuum-ultraviolet and X-ray regions because of lack of suitable non-absorbing materials and damaging of optical elements at high specific power levels. Therefore, it is of some interest to analyse polarization of untreated FEL radiation obtained with various types of undulators, with and without axial magnetic field. The polarization is studied using solutions for electron orbits in various cases: plane or helical undulator with or without axial magnetic field, two plane undulators, a combination of right- and left-handed helical undulators with equal periods, but different field amplitudes. Some examples of how a desired polarization (elliptical circular or linear) can be obtained or changed quickly, which is necessary in many experiments, are given.

  9. A 282 GHz Probe for Dynamic Nuclear Polarization

    DEFF Research Database (Denmark)

    Rybalko, Oleksandr; Bowen, Sean; Zhurbenko, Vitaliy

    Introduction In DNP, microwave irradiation of a sample facilitates the transfer of spin polarization from electrons tonuclei. One of the way to improve the DNP enhancement is to transfer microwave power from the mm-wave source tothe sample more effectively. Several methods and techniques to effic......Introduction In DNP, microwave irradiation of a sample facilitates the transfer of spin polarization from electrons tonuclei. One of the way to improve the DNP enhancement is to transfer microwave power from the mm-wave source tothe sample more effectively. Several methods and techniques......: microwave can with RF coil; the rest of the probe consists of a waveguide, sample tube and coaxial transmission line. The probe is designed to study cylindrical samples with diameter - 9 mm, and height – 2-20 mm. An RF coil which is housed in cylindrical Macor coil form (dielectric with ε=5.64 and tangent δ...... is 0.0025) surrounds the sample. The RF coil has a saddle form and was madeout of two current loops run on opposite sides of a cylinder (in parallel). Material of the coil is copper wire with diameterequal to 0.7 mm. Coil dimensions are: diameter - 13 mm; height - 22.0 mm. The self resonant frequency...

  10. Electron interactions with polar molecules

    International Nuclear Information System (INIS)

    Garrett, W.R.

    1981-01-01

    A description is given of a number of the features of discrete and continuous spectra of electrons interacting with polar molecules. Attention is focused on the extent to which theoretical predictions concerning cross sections, resonances, and bound states are strongly influenced by the various approximations that are so ubiquitous in the treatment of such problems. Similarly, threshold scattering and photodetachment processes are examined for the case of weakly bound dipole states whose higher members overlap the continuum

  11. Polarization of fluorescence: a probe of molecular autoionization

    International Nuclear Information System (INIS)

    Leroi, G.E.; Dehmer, J.L.; Parr, A.C.; Poliakoff, E.D.

    1983-01-01

    The polarization of fluorescence from excited-state molecular photoions provides a direct probe of the photoionization dynamics and the symmetry signatures of autoionizing resonances. Measurements on CO 2 and CS 2 are presented as examples

  12. POLARIZED BEAMS: 1 - Longitudinal electron spin polarization at HERA

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1994-09-15

    Wednesday 4 May marked a turning point in the art of the manipulation of spins in electron storage rings: longitudinal electron spin polarization (with the spins oriented along the electrons' direction of motion) was established in the electron ring of HERA, the electronproton collider at DESY in Hamburg. A polarization level of about 55% was obtained and polarizations of over 60% were reproducibly obtained in the following days. The beam energy was 27.52 GeV, corresponding to half integer spin tune of 62.5.

  13. LINEARLY POLARIZED PROBES OF SURFACE CHIRALITY

    NARCIS (Netherlands)

    VERBIEST, T; KAURANEN, M; MAKI, JJ; TEERENSTRA, MN; SCHOUTEN, AJ; NOLTE, RJM; PERSOONS, A

    1995-01-01

    We present a new nonlinear optical technique to study surface chirality. We demonstrate experimentally that the efficiency of second-harmonic generation from isotropic chiral surfaces is different for excitation with fundamental light that is +45 degrees and -45 degrees linearly polarized with

  14. Development of spin polarized electron beam

    International Nuclear Information System (INIS)

    Nakanishi, Tsutomu

    2001-01-01

    Physical structure of the polarized electron beam production is explained in this paper. Nagoya University group has been improving the quality of beam. The present state of quality and the development objects are described. The new results of the polarized electron reported in 'RES-2000 Workshop' in October 2000, are introduced. The established ground of GaAs type polarized electron beam source, observation of the negative electron affinity (NEA) surface, some problems of NEA surface of high energy polarized electron beam such as the life, time response, the surface charge limited phenomena of NEA surface are explained. The interested reports in the RES-2000 Workshop consisted of observation by SPLEEM (Spin Low Energy Electron Microscope), Spin-STM and Spin-resolved Photoelectron Spectroscopy. To increase the performance of the polarized electron source, we will develop low emittance and large current. (S.Y.)

  15. Polarization Characteristics Inferred From the Radio Receiver Instrument on the Enhanced Polar Outflow Probe

    Science.gov (United States)

    Danskin, Donald W.; Hussey, Glenn C.; Gillies, Robert G.; James, H. Gordon; Fairbairn, David T.; Yau, Andrew W.

    2018-02-01

    The Radio Receiver Instrument (RRI) on the CAScade, Smallsat, and Ionospheric Polar Explorer/enhanced Polar Outflow Probe (CASSIOPE/e-POP) satellite was used to receive continuous wave and binary phase shift keyed transmissions from a high-frequency transmitter located in Ottawa, ON, Canada during April 2016 to investigate how the ionosphere affects the polarization characteristics of transionospheric high-frequency radio waves. The spacecraft orientation was continuously slewed to maintain the dipole orientation in a plane perpendicular to the direction toward the transmitter, enabling the first in situ planar polarization determination for continuous wave and binary phase shift keyed modulated radio waves from space at times when the wave frequency is at least 1.58 times the plasma frequency. The Stokes parameters and polarization characteristics were derived from the measured data and interpreted using an existing ray tracing model. For the southern part of the passes, the power was observed to oscillate between the two dipoles of RRI, which was attributed to Faraday rotation of the radio waves. For the first time, a reversal in the rate of change of orientation angle was observed where the minimum in modeled Faraday rotation occurred. The reversal point was poleward of the point of closest approach between the satellite and transmitter; this was explained by the variations of total electron content and component of magnetic field along the direction of propagation. The received signals show both quasi-longitudinal (QL) and quasi-transverse characteristics. South of the transmitter the QL regime is dominant. Around the reversal point, a combination of QL and quasi-transverse nature was observed.

  16. Polarization experiments with hadronic and electromagnetic probes

    International Nuclear Information System (INIS)

    Punjabi, V.

    1993-01-01

    The following research activities were carried out during the past year Calibration of focal plane polarimeter POMME up to 2.4 GeV at Saturne National Laboratory (LNS) in Saclay. Measurement of tensor analyzing power T 20 and polarization transfer κ 0 at Saturne up to 2.1 GeV in elastic backward dp scattering rvec dp → rvec pd. Measurement of tensor analyzing power T 20 at synchrophasotron in Dubha up to 4.4 Gev in elastic backward dp scattering rvec dp → pd. Resubmission of conditionally Approved G EP proposal 89-14 at CEBAF. Start construction of focal plane polarimeter (FPP) for CEBAF hall A hadron spectrometer. The planned work for the next year includes: Construction of FPP for CEBAF hall A hadron spectrometer; measurement of polarization transfer κ 0 and tensor analyzing power T 20 in elastic backward dp scattering at Saturne; measurements of tensor analyzing power in 1 H( 6 Li,d)X, 1 H( 6 Li,α)X, 1 H( 6 Li,t)X and 1 H( 6 Li, 3 He)X reactions at Saturne; and study of polarization transfer in 2 H(rvec e,e'rvec p)n reaction at Bates

  17. Spin polarized electrons in surface science

    International Nuclear Information System (INIS)

    Siegmann, H.C.

    1983-01-01

    The potentialities of spin-polarised electron beams as a probe of surface magnetic properties are outlined. Elastic as well as inelastic scattering of electrons from solid surfaces are considered. (G.Q.)

  18. Physics results with polarized electrons at SLAC

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1996-03-01

    Polarized electron beams can play an important role in the dynamics of interactions at high energies. Polarized electron beams at SLAC have been an important part of the physics program since 1970, when they were first proposed for use in testing the spin structure of the proton. Since 1992, the SLAC linear accelerator and the SLC have operated solely with polarized electrons, providing data for tests of QCD in studies of the spin structure of the nucleon and tests of the electroweak sector of the Standard Model. In the following sections, the performance of the source is summarized, and some of the recent results using the polarized beams are discussed

  19. Probing Quark-Gluon Interactions with Transverse Polarized Scattering

    International Nuclear Information System (INIS)

    Rondon, Oscar A.

    2011-01-01

    Transverse polarized inelastic scattering extends the power of the electromagnetic interaction as a probe of nucleon dynamics beyond the leading order regime explored with longitudinally polarized DIS. In transverse polarized scattering, the twist-3 g 2 spin structure function contributes at the same order as the longitudinal, twist-2, g 1 , so interactions between quarks and gluons can be studied, opening a window on the mechanisms of confinement. This talk reports the results of Jefferson Lab's Resonances Spin Structure experiment measurement of g 2 and the d 2 twist-3 quark matrix element at a four-momentum transfer of 1.3 GeV 2 .

  20. Near-field circular polarization probed by chiral polyfluorene

    NARCIS (Netherlands)

    Savoini, M.; Biagioni, P.; Lakhwani, G.; Meskers, S.C.J.; Duò, L.; Finazzi, M.

    2009-01-01

    We demonstrate that a high degree of circular polarization can be delivered to the near field (NF) of an aperture at the apex of hollow-pyramid probes for scanning optical microscopy. This result is achieved by analyzing the dichroic properties of an annealed thin polymer film containing a chiral

  1. Spin polarization of electrons in quantum wires

    OpenAIRE

    Vasilchenko, A. A.

    2013-01-01

    The total energy of a quasi-one-dimensional electron system is calculated using density functional theory. It is shown that spontaneous ferromagnetic state in quantum wire occurs at low one-dimensional electron density. The critical electron density below which electrons are in spin-polarized state is estimated analytically.

  2. Versatile spin-polarized electron source

    Science.gov (United States)

    Jozwiak, Chris; Park, Cheol -Hwan; Gotlieb, Kenneth; Louie, Steven G.; Hussain, Zahid; Lanzara, Alessandra

    2015-09-22

    One or more embodiments relate generally to the field of photoelectron spin and, more specifically, to a method and system for creating a controllable spin-polarized electron source. One preferred embodiment of the invention generally comprises: method for creating a controllable spin-polarized electron source comprising the following steps: providing one or more materials, the one or more materials having at least one surface and a material layer adjacent to said surface, wherein said surface comprises highly spin-polarized surface electrons, wherein the direction and spin of the surface electrons are locked together; providing at least one incident light capable of stimulating photoemission of said surface electrons; wherein the photon polarization of said incident light is tunable; and inducing photoemission of the surface electron states.

  3. Probing plasmonic nanostructures by photons and electrons

    DEFF Research Database (Denmark)

    Kneipp, Katrin; Kneipp, Harald; Kneipp, Janina

    2015-01-01

    We discuss recent developments for studying plasmonic metal nanostructures. Exploiting photons and electrons opens up new capabilities to probe the complete plasmon spectrum including bright and dark modes and related local optical fields at subnanometer spatial resolution. This comprehensive cha...

  4. Titanium pigmentation. An electron probe microanalysis study

    International Nuclear Information System (INIS)

    Dupre, A.; Touron, P.; Daste, J.; Lassere, J.; Bonafe, J.L.; Viraben, R.

    1985-01-01

    A patient had an unusual pigmentary disease induced by titanium dioxide. The use of a topical cream containing titanium dioxide caused a xanthomalike appearance on the patient's penis. Electron probe microanalysis was valuable in establishing the cause of this balanitis

  5. Physics with polarized electrons and targets

    International Nuclear Information System (INIS)

    Donnelly, T.W.

    1984-01-01

    With the advent of electron stretcher or storage rings electron scattering from polarized targets becomes a general new tool for nuclear structure studies. Without such facilities it is necessary to have very dense polarized targets for use with the typical (less or approximately equal 50 μA) electron beams available and very few measurements of this type have been attempted. On the other hand, with electron rings the effective circulating current can be greatly increased. In this case much thinner internal targets may be used while still maintaining the same luminosity as in external beam experiments. In ancticipation of such new experimental capabilities we have re-developed the theoretical basis for discussions of electron scattering from polarized targets using either unpolarized or polarized electron beams. This work takes the formalism of unpolarized (e,e') and extends it in a straightforward way to include general polarizations of electrons, target nuclei, recoil nuclei or any combinations of these polarizations. In the present context it is only possible to provide a brief summary of the general form of the cross section and to present a few illustrative examples of the nuclear structure information that may be extracted from such polarization measurements

  6. Direct Probing of Polarization Charge at Nanoscale Level

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Owoong [Sungkyunkwan Univ., Suwon (Republic of Korea). School of Advanced Materials and Engineering; Seol, Daehee [Sungkyunkwan Univ., Suwon (Republic of Korea). School of Advanced Materials and Engineering; Lee, Dongkyu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Han, Hee [Korea Research Inst. of Standards and Science (KRISS), Daejeon (South Korea); Lindfors-Vrejoiu, Ionela [Univ. of Cologne (Germany). Physics Inst.; Lee, Woo [Korea Research Inst. of Standards and Science (KRISS), Daejeon (South Korea); Jesse, Stephen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences; Lee, Ho Nyung [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Kalinin, Sergei V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences; Alexe, Marin [Univ. of Warwick, Coventry (United Kingdom). Dept. of Physics; Kim, Yunseok [Sungkyunkwan Univ., Suwon (Republic of Korea). School of Advanced Materials and Engineering

    2017-11-14

    Ferroelectric materials possess spontaneous polarization that can be used for multiple applications. Owing to a long-term development of reducing the sizes of devices, the preparation of ferroelectric materials and devices is entering the nanometer-scale regime. In order to evaluate the ferroelectricity, there is a need to investigate the polarization charge at the nanoscale. Nonetheless, it is generally accepted that the detection of polarization charges using a conventional conductive atomic force microscopy (CAFM) without a top electrode is not feasible because the nanometer-scale radius of an atomic force microscopy (AFM) tip yields a very low signal-to-noise ratio. But, the detection is unrelated to the radius of an AFM tip and, in fact, a matter of the switched area. In this work, the direct probing of the polarization charge at the nanoscale is demonstrated using the positive-up-negative-down method based on the conventional CAFM approach without additional corrections or circuits to reduce the parasitic capacitance. The polarization charge densities of 73.7 and 119.0 µC cm-2 are successfully probed in ferroelectric nanocapacitors and thin films, respectively. The results we obtained show the feasibility of the evaluation of polarization charge at the nanoscale and provide a new guideline for evaluating the ferroelectricity at the nanoscale.

  7. Polarized positrons in Jefferson lab electron ion collider (JLEIC)

    Science.gov (United States)

    Lin, Fanglei; Grames, Joe; Guo, Jiquan; Morozov, Vasiliy; Zhang, Yuhong

    2018-05-01

    The Jefferson Lab Electron Ion Collider (JLEIC) is designed to provide collisions of electron and ion beams with high luminosity and high polarization to reach new frontier in exploration of nuclear structure. The luminosity, exceeding 1033 cm-2s-1 in a broad range of the center-of-mass (CM) energy and maximum luminosity above 1034 cm-2s-1, is achieved by high-rate collisions of short small-emittance low-charge bunches with proper cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3He) and electron can be easily preserved, manipulated and maintained by taking advantage of the unique figure-8 shape rings. With a growing physics interest, polarized positron-ion collisions are considered to be carried out in the JLEIC to offer an additional probe to study the substructure of nucleons and nuclei. However, the creation of polarized positrons with sufficient intensity is particularly challenging. We propose a dedicated scheme to generate polarized positrons. Rather than trying to accumulate "hot" positrons after conversion, we will accumulate "cold" electrons before conversion. Charge accumulation additionally provides a novel means to convert high repetition rate (>100 MHz) electron beam from the gun to a low repetition rate (<100 MHz) positron beam for broad applications. In this paper, we will address the scheme, provide preliminary estimated parameters and explain the key areas to reach the desired goal.

  8. Polarity analysis of GaN nanorods by photo-assisted Kelvin probe force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Jiandong; Neumann, Richard; Wang, Xue; Li, Shunfeng; Fuendling, Soenke; Merzsch, Stephan; Al-Suleiman, Mohamed A.M.; Soekmen, Uensal; Wehmann, Hergo-H.; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany)

    2011-07-15

    Polarity dependence (N-polar (000-1) and Ga-polar (0001)) of surface photovoltage of epitaxially grown, vertically aligned GaN nanorods has been investigated by photo-assisted Kelvin probe force microscopy (KPFM). Commercial GaN substrates with known polarities are taken as reference samples. The polarity of GaN substrates can be well distinguished by the change in surface photovoltage upon UV illumination in air ambient. These different behaviors of Ga- and N-polar surfaces are attributed to the polarity-related surface-bound charges and photochemical reactivity. GaN nanorods were grown on patterned SiO{sub 2}/sapphire templates by metal-organic vapor phase epitaxy (MOVPE). In order to analyze the bottom surface of the grown GaN nanorods, a technique known from high power electronics and joining techniques is applied to remove the substrate. The top and bottom surfaces of the GaN nanorods are identified to be N-polar and Ga-polar according to the KPFM results, respectively. Our experiments demonstrate that KPFM is a simple and suitable method capable to identify the polarity of GaN nanorods. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Photoemission of Bi_{2}Se_{3} with Circularly Polarized Light: Probe of Spin Polarization or Means for Spin Manipulation?

    Directory of Open Access Journals (Sweden)

    J. Sánchez-Barriga

    2014-03-01

    Full Text Available Topological insulators are characterized by Dirac-cone surface states with electron spins locked perpendicular to their linear momenta. Recent theoretical and experimental work implied that this specific spin texture should enable control of photoelectron spins by circularly polarized light. However, these reports questioned the so far accepted interpretation of spin-resolved photoelectron spectroscopy. We solve this puzzle and show that vacuum ultraviolet photons (50–70 eV with linear or circular polarization indeed probe the initial-state spin texture of Bi_{2}Se_{3} while circularly polarized 6-eV low-energy photons flip the electron spins out of plane and reverse their spin polarization, with its sign determined by the light helicity. Our photoemission calculations, taking into account the interplay between the varying probing depth, dipole-selection rules, and spin-dependent scattering effects involving initial and final states, explain these findings and reveal proper conditions for light-induced spin manipulation. Our results pave the way for future applications of topological insulators in optospintronic devices.

  10. Latest on polarization in electron storage rings

    International Nuclear Information System (INIS)

    Chao, A.W.

    1983-01-01

    The field of beam polarization in electron storage rings is making rapid progress in recent several years. This report is an attempt to summarize some of these developments concerning how to produce and maintain a high level of beam polarization. Emphasized will be the ideas and current thoughts people have on what should and could be done on electron rings being designed at present such as HERA, LEP and TRISTAN. 23 references

  11. Spin-polarized scanning electron microscopy

    International Nuclear Information System (INIS)

    Kohashi, Teruo

    2014-01-01

    Spin-Polarized Scanning Electron Microscopy (Spin SEM) is one way for observing magnetic domain structures taking advantage of the spin polarization of the secondary electrons emitted from a ferromagnetic sample. This principle brings us several excellent capabilities such as high-spatial resolution better than 10 nm, and analysis of magnetization direction in three dimensions. In this paper, the principle and the structure of the spin SEM is briefly introduced, and some examples of the spin SEM measurements are shown. (author)

  12. EPIC - an electron-polarized ion collider

    International Nuclear Information System (INIS)

    Cameron, J.M.

    1999-01-01

    As discussed earlier in this workshop, we have been studying at the Indiana University Cyclotron Facility (IUCF) for some time the potential of a facility-the Light Ion Spin Synchrotron (LISS)- focusing on reactions induced by polarized nucleons at ∼ 1 to 20 GeV. The technology would extrapolate from what we have learned using our existing Cooler ring using internal polarized targets. Indeed, these techniques are most viable at higher energies where the loss of the stored beam is due to the nuclear reactions which are of interest and not that of multiple Coulomb scattering which dominate in our present energy range. However, while the internal targets are not exactly fixed, they certainly do not contribute to the available energy in the center of momentum frame. Consequently, the energy and momentum which can be effective explored are 6 GeV and 3 GeV/c respectively, about the same range that we expect to explore using electromagnetic probes using the enhanced Thomas Jefferson National Accelerator Laboratory electron beam. Looking at the structure of hadrons, as we currently understand it, one can divide it into four size scales. The LISS facility would permit studies of the manifestation of the nucleon substructure but generally would not get to scales where one would only have incoherent interactions at the partonic level. Following in a path already trodden by our European colleagues, we have recently started to look at the possibility of adding an electronic collider option to our plans. This would significantly increase the kinematic range, with 25 GeV protons and 4 GeV electrons (one gets over 20 GeV in the center of mass-equivalent to about 200 GeV on a fixed proton target). The accessible range provides coverage up to Q 2 = 20 GeV/ c 2 and down to x ∼ 10 -2 (here x = Q 2 /2Mv, the usual Bjorken scaling variable). As the energy of both beams would be variable, one can cover the whole range between HERMES and CERN/FNAL muon beams. Examples of the range of

  13. Polarized electrons, trions, and nuclei in charged quantum dots

    Science.gov (United States)

    Bracker, A. S.; Tischler, J. G.; Korenev, V. L.; Gammon, D.

    2003-07-01

    We have investigated spin polarization in GaAs quantum dots. Excitons and trions are polarized directly by optical excitation and studied through polarization of photoluminescence. Electrons and nuclei are polarized indirectly through subsequent relaxation processes. Polarized electrons are identified by the Hanle effect for exciton and trion photoluminescence, while polarized nuclei are identified through the Overhauser effect in individual charged quantum dots.

  14. STANFORD: Highly polarized SLC electron beams

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Full text: Using specialized photocathodes made with 'strained' gallium arsenide, physicists at the Stanford Linear Accelerator Center (SLAC) have generated electron beams with polarizations in excess of 60 percent a year ahead of schedule. Together with recent luminosity increases, this breakthrough will have a major impact on the physics output of the Stanford Linear Collider (SLC). Beam polarization was almost tripled using photocathodes in which a gallium arsenide layer was grown epitaxially over a substrate of gallium arsenide phosphide. The mismatch between these two layers deforms the crystal structure and removes a degeneracy in the valence band structure, permitting selective optical pumping of one unique spin state. Whereas conventional gallium arsenide photocathodes are limited to 50 percent polarization because of this degeneracy (and realistic cathodes fall substantially below this theoretical limit), such strained crystal lattices have the potential to yield polarizations close to 100 percent. Polarization enhancement with strained lattices was first demonstrated in 1991 by a SLAC/Wisconsin/ Berkeley group (May 1991, page 6) with a 71 percent polarization in a laboratory experiment. More recently this group has achieved polarization in excess of 90 percent, reported last November at the Nagoya Spin Symposium. (In a complementary development, a Japanese KEK/ Nagoya/KEK obtains polarized beams using a 'superlattice' - May 1991, page 4.) The 1993 SLC run, the strained gallium arsenide photocathode technique's debut in an operating particle accelerator, has proved to be a resounding, unqualified success - as have physics experiments on the Z particles produced by the highly polarized beam. A conservative approach was called for, due to concerns about possible charge saturation effects. A relatively thick (0.3 micron) gallium arsenide layer was used for the photocathode in the SLC polarized electron source. With a titanium

  15. Performance of the SLC polarized electron source with high polarization

    International Nuclear Information System (INIS)

    Clendenin, J.E.; Alley, R.K.; Aoyagi, H.

    1993-04-01

    For the 1992 operating cycle of the SLAC Linear Collider (SLC), the polarized electron source (PES) during its maiden run successfully met the pulse intensity and overall efficiency requirements of the SLC. However, the polarization of the bulk GaAs cathode was low (∼27%) and the pulse-to-pulse stability was marginal. We have shown that adequate charge for the SLC can be extracted from a strained layer cathode having P e ∼80% even though the quantum efficiency (QE) is - beam stability. The performance of the PES during the 1993 SLC operating cycle with these and other improvements is discussed

  16. A polarized look at nucleons: Laser electron gamma source

    International Nuclear Information System (INIS)

    1991-01-01

    As the title suggests we are going to look at reactions induced on nucleons by polarized photons. The results I am going to show today are from the Laser Electron Gamma Source, or ''LEGS'' facility, at Brookhaven National Laboratory. At LEGS, gamma ray beams are produced by backscattering laser light from relativistic electrons. I will only summarize the main characteristics of this facility, and leave an in depth description to Dr. Schaerf who will discuss LEGS and other similar backscattering facilities on Wednesday. Reactions with polarized photons inevitably reflect interference terms that for the most part remain hidden in spin-averaged unpolarized measurements. This provides a tool for probing interactions that depend upon spin. In particular, we are going to look today at two cases where the polarization is used to probe the tensor interaction. First, we will examine the tensor force between a proton-neutron pair in deuterium. Secondly, we will examine the tensor force between quarks in a proton that produces a small E2 component that is mixed with the predominantly M1 excitation of the delta resonance.The magnitude of this E2 components provides a sensitive probe of the structure of the Nucleon

  17. CMBPol Mission Concept Study: Probing Inflation with CMB Polarization

    CERN Document Server

    Baumann, Daniel; Adshead, Peter; Amblard, Alexandre; Ashoorioon, Amjad; Bartolo, Nicola; Bean, Rachel; Beltran, Maria; de Bernardis, Francesco; Bird, Simeon; Chen, Xingang; Chung, Daniel Jun Hun; Colombo, Loris; Cooray, Asantha R.; Creminelli, Paolo; Dodelson, Scott; Dunkley, Joanna; Dvorkin, Cora; Easther, Richard; Finelli, Fabio; Flauger, Raphael; Hertzberg, Mark P.; Jones-Smith, Katherine; Kachru, Shamit; Kadota, Kenji; Khoury, Justin; Kinney, William H.; Komatsu, Eiichiro; Krauss, Lawrence M.; Lesgourgues, Julien; Liddle, Andrew R.; Liguori, Michele; Lim, Eugene A.; Linde, Andrei D.; Matarrese, Sabino; Mathur, Harsh; McAllister, Liam; Melchiorri, Alessandro; Nicolis, Alberto; Pagano, Luca; Peiris, Hiranya V.; Peloso, Marco; Pogosian, Levon; Pierpaoli, Elena; Riotto, Antonio; Seljak, Uros; Senatore, Leonardo; Shandera, Sarah E.; Silverstein, Eva; Smith, Tristan; Vaudrevange, Pascal M.; Verde, Licia; Wandelt, Ben; Wands, David; Watson, Scott; Wyman, Mark; Yadav, Amit; Valkenburg, Wessel; Zaldarriaga, Matias

    2009-01-01

    We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes of the physics of inflation. We focus on the prospects for using CMB measurements to differentiate various inflationary mechanisms. In particular, a detection of primordial B-mode polarization would demonstrate that inflation occurred at a very high energy scale, and that the inflaton traversed a super-Planckian distance in field space. We explain how such a detection or constraint would illuminate aspects of physics at the Planck scale. Moreover, CMB measurements can constrain the scale-dependence and non-Gaussianity of the primordial fluctuations and limit the possibility of a significant isocurvature contribution. Each such limit provides crucial information on the underlying inflationary dynamics. Finally, we quantify these considerations by presenting forecasts for the sensitivities of a future satellite experiment to the inflationary parameters.

  18. The Polarized Electron Source at ELSA

    International Nuclear Information System (INIS)

    Drachenfels, Wolther von; Frommberger, Frank; Gowin, Michael; Hillert, Wolfgang; Hoffmann, Markus; Neff, Bernhold

    2003-01-01

    At the electron stretcher accelerator ELSA in Bonn a pulsed 50 kV inverted gun of polarized electrons has been in operation since February 2000. A strained-layer superlattice crystal is used to deliver a beam with a polarization of about 80 %. A flashlamp-pumped Ti-Sapphire laser with a pulse repetition rate of 50 Hz serves as source of light. The gun is operated in space charge limitation. The current can be chosen by varying the distance between cathode and anode. With 1 μs pulses of 100 mA the source was particularly used together with a polarized target for a GDH sum rule experiment. The high photocathode lifetime allows continuous operation at 100 mA typically for periods of about two weeks without maintenance. So far no change of the crystal was necessary

  19. Principal and experimental study of source of polarized electrons

    International Nuclear Information System (INIS)

    Shang Rencheng; Gao Junfang; Xiao Yuan; Pang Wenning; Deng Jingkang

    1999-01-01

    The getting of polarized electrons was briefly introduced, that is the source of polarized electrons. The measurement of polarization in future, the application of polarized electrons in atomic and molecular physics, condensed physics, biological physics, nuclear and particle physics were discussed

  20. Developments in quantitative electron probe microanalysis

    International Nuclear Information System (INIS)

    Tixier, R.

    1977-01-01

    A study of the range of validity of the formulae for corrections used with massive specimen analysis is made. The method used is original; we have shown that it was possible to use a property of invariability of corrected intensity ratios for standards. This invariance property provides a test for the self consistency of the theory. The theoretical and experimental conditions required for quantitative electron probe microanalysis of thin transmission electron microscope specimens are examined. The correction formulae for atomic number, absorption and fluorescence effects are calculated. Several examples of experimental results are given, relative to the quantitative analysis of intermetallic precipitates and carbides in steels. Advances in applications of electron probe instruments related to the use of computer and the present development of fully automated instruments are reviewed. The necessary statistics for measurements of X ray count data are studied. Estimation procedure and tests are developed. These methods are used to perform a statistical check of electron probe microanalysis measurements and to reject rogue values. An estimator of the confidence interval of the apparent concentration is derived. Formulae were also obtained to optimize the counting time in order to obtain the best precision in a minimum amount of time [fr

  1. STANFORD: Producing highly polarized electrons (2)

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    Electron spin polarization above 70% by photoemission from a specially prepared semiconductor has been achieved by T. Maruyama and E. Garwin of the Stanford Linear Accelerator Center (SLAC), R. Prepost and G. Zapalac of Wisconsin, and J. Walker and S. Smith of Berkeley

  2. KEK/NAGOYA/SLAC: Highly polarized electrons

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    In the push by the Japanese KEK Laboratory, in collaboration with university groups and overseas laboratories, to develop new techniques for the future Japan electronpositron collider (JLC), a recent achievement is a significant increase in the efficient yield of highly polarized electrons

  3. Electronic system for Langmuir probe measurements

    Czech Academy of Sciences Publication Activity Database

    Mitov, M.; Bankova, A.; Dimitrova, M.; Ivanova, P.; Tutulkov, K.; Djermanova, N.; Dejarnac, Renaud; Stöckel, Jan; Popov, Tsv.K.

    2012-01-01

    Roč. 356, č. 1 (2012), s. 012008 ISSN 1742-6588. [InternationalSummerSchoolonVacuum,Electron, and IonTechnologies(VEIT2011)/17./. Sunny Beach, 19.09.2011-23.09.2011] Institutional research plan: CEZ:AV0Z20430508 Keywords : Plasma * tokamak * diagnostics * electric probe Subject RIV: BL - Plasma and Gas Discharge Physics http://iopscience.iop.org/1742-6596/356/1/012008/pdf/1742-6596_356_1_012008.pdf

  4. Electronic probe microanalyzer. Annual report 1963

    International Nuclear Information System (INIS)

    Kirianenko, Alexis; Maurice, Francoise; Seguin, Remy; Zemskoff, Anne; Adda, Yves

    1964-09-01

    This annual report presents the highlights of the fifth year of operation of the CEA Saclay's electronic probe microanalyzer. It provides a list of the analyses performed during the year with some illustrations and mentions the improvements given to the apparatus and its new analysing possibilities (crystallographic analysis using divergent X beams, 'electronic' image formation with respect to the atomic number). Highlights in the development of this analytical technique are presented as well as a new device designed by R. Castaing: the secondary ion emission microanalyser. A list of all laboratories equipped with the French microanalyser is provided

  5. d-PET-controlled “off-on” Polarity-sensitive Probes for Reporting Local Hydrophilicity within Lysosomes

    Science.gov (United States)

    Zhu, Hao; Fan, Jiangli; Mu, Huiying; Zhu, Tao; Zhang, Zhen; Du, Jianjun; Peng, Xiaojun

    2016-10-01

    Polarity-sensitive fluorescent probes are powerful chemical tools for studying biomolecular structures and activities both in vitro and in vivo. However, the lack of “off-on” polarity-sensing probes has limited the accurate monitoring of biological processes that involve an increase in local hydrophilicity. Here, we design and synthesize a series of “off-on” polarity-sensitive fluorescent probes BP series consisting of the difluoroboron dippyomethene (BODIPY) fluorophore connected to a quaternary ammonium moiety via different carbon linkers. All these probes showed low fluorescence quantum yields in nonpolar solution but became highly fluorescent in polar media. BP-2, which contains a two-carbon linker and a trimethyl quaternary ammonium, displayed a fluorescence intensity and quantum yield that were both linearly correlated with solvent polarity. In addition, BP-2 exhibited high sensitivity and selectivity for polarity over other environmental factors and a variety of biologically relevant species. BP-2 can be synthesized readily via an unusual Mannich reaction followed by methylation. Using electrochemistry combined with theoretical calculations, we demonstrated that the “off-on” sensing behavior of BP-2 is primarily due to the polarity-dependent donor-excited photoinduced electron transfer (d-PET) effect. Live-cell imaging established that BP-2 enables the detection of local hydrophilicity within lysosomes under conditions of lysosomal dysfunction.

  6. The polarized electron beam at ELSA

    International Nuclear Information System (INIS)

    Hoffmann, M.; Drachenfels, W. von; Frommberger, F.; Gowin, M.; Hillert, W.; Husmann, D.; Keil, J.; Helbing, K.; Michel, T.; Naumann, J.; Speckner, T.; Zeitler, G.

    2001-01-01

    The future medium energy physics program at the electron stretcher accelerator ELSA of Bonn University mainly relies on experiments using polarized electrons in the energy range from 1 to 3.2 GeV. To provide a polarized beam with high polarization and sufficient intensity a dedicated source has been developed and set into operation. To prevent depolarization during acceleration in the circular accelerators several depolarizing resonances have to be corrected for. Intrinsic resonances are compensated using two pulsed betatron tune jump quadrupoles. The influence of imperfection resonances is successfully reduced applying a dynamic closed orbit correction in combination with an empirical harmonic correction on the energy ramp. In order to minimize beam depolarization, both types of resonances and the correction techniques have been studied in detail. It turned out that the polarization in ELSA can be conserved up to 2.5 GeV and partially up to 3.2 GeV which is demonstrated by measurements using a Moeller polarimeter installed in the external GDH1-beamline

  7. Electron scattering with polarized targets at TESLA

    International Nuclear Information System (INIS)

    Anselmino, M.; Aschenauer, E.C.; Belostotski, S.

    2000-11-01

    Measurements of polarized electron-nucleon scattering can be realized at the TESLA linear collider facility with projected luminosities that are about two orders of magnitude higher than those expected of other experiments at comparable energies. Longitudinally polarized electrons, accelerated as a small fraction of the total current in the e + arm of TESLA, can be directed onto a solid state target that may be either longitudinally or transversely polarized. A large variety of polarized parton distribution and fragmentation functions can be determined with unprecedented accuracy, many of them for the first time. A main goal of the experiment is the precise measurement of the x- and Q 2 -dependence of the experimentally totally unknown quark transversity distributions that will complete the information on the nucleon's quark spin structure as relevant for high energy processes. Comparing their Q 2 -evolution to that of the corresponding helicity distributions constitutes an important precision test of the predictive power of QCD in the spin sector. Measuring transversity distributions and tensor charges allows access to the hitherto unmeasured chirally odd operators in QCD which are of great importance to understand the role of chiral symmetry. The possibilities of using unpolarized targets and of experiments with a real photon beam turn TESLA-N into a versatile next-generation facility at the intersection of particle and nuclear physics. (orig.)

  8. Electron Beam Polarization Measurement Using Touschek Lifetime Technique

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Changchun; /Duke U., DFELL; Li, Jingyi; /Duke U., DFELL; Mikhailov, Stepan; /Duke U., DFELL; Popov, Victor; /Duke U., DFELL; Wu, Wenzhong; /Duke U., DFELL; Wu, Ying; /Duke U., DFELL; Chao, Alex; /SLAC; Xu, Hong-liang; /Hefei, NSRL; Zhang, Jian-feng; /Hefei, NSRL

    2012-08-24

    Electron beam loss due to intra-beam scattering, the Touschek effect, in a storage ring depends on the electron beam polarization. The polarization of an electron beam can be determined from the difference in the Touschek lifetime compared with an unpolarized beam. In this paper, we report on a systematic experimental procedure recently developed at Duke FEL laboratory to study the radiative polarization of a stored electron beam. Using this technique, we have successfully observed the radiative polarization build-up of an electron beam in the Duke storage ring, and determined the equilibrium degree of polarization and the time constant of the polarization build-up process.

  9. Bates GaAs polarized electron source

    International Nuclear Information System (INIS)

    Schaefer, H.R.; Cates, G.; Michaels, R.; Hughes, V.W.; Lubell, M.S.; Souder, P.A.

    1983-05-01

    In order to pursue measurements of parity violating effects of the neutral weak current, we have developed a polarized electron source suitable for installation at the MIT-Bates Linear Accelerator. The source is designed to provide a high peak-current pulsed beam that has a approx. 1% duty factor and that is extremely stable under helicity reversal. 34 references, 6 figures, 1 table

  10. The polarized electron gun for the SLC

    International Nuclear Information System (INIS)

    Schultz, D.C.; Clendenin, J.; Frisch, J.; Hoyt, E.; Klaisner, L.; Woods, M.; Wright, D.; Zolotorev, M.

    1992-03-01

    A new polarized electron gun for use on the SLC at SLAC has been built and tested. It is a diode gun with a laser driven GaAs photocathode. It is designed to provide short (2ns) pulses of 10 A at 160 kV at 120 Hz. The design features of the gun and results from a testing program on a new and dedicated beam line are presented. Early results from operation on the SLC will also be shown

  11. SLC polarized beam source electron optics design

    International Nuclear Information System (INIS)

    Eppley, K.R.; Lavine, T.L.; Early, R.A.; Herrmannsfeldt, W.B.; Miller, R.H.; Schultz, D.C.; Spencer, C.M.; Yeremian, A.D.

    1991-05-01

    This paper describes the design of the beam-line from the polarized electron gun to the linac injector in the Stanford Linear Collider (SLC). The polarized electron source is a GaAs photocathode, requiring 10 -11 -Torr-range pressure for adequate quantum efficiency and longevity. The photocathode is illuminated by 3-nsec-long laser pulses. The quality of the optics for the 160-kV beam is crucial since electron-stimulated gas desorption from beam loss in excess of 0.1% of the 20-nC pulses may poison the photocathode. Our design for the transport line consists of a differential pumping region isolated by a pair of valves. Focusing is provided by a pair of Helmholtz coils and by several iron-encased solenoidal lenses. Our optics design is based on beam transport simulations using 2 1/2-D particle-in-cell codes to model the gun and to solve the fully-relativistic time-dependent equations of motion in three dimensions for electrons in the presence of azimuthally symmetric electromagnetic fields. 6 refs., 6 figs

  12. 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

  13. Spin-polarized scanning-tunneling probe for helical Luttinger liquids.

    Science.gov (United States)

    Das, Sourin; Rao, Sumathi

    2011-06-10

    We propose a three-terminal spin-polarized STM setup for probing the helical nature of the Luttinger liquid edge state that appears in the quantum spin Hall system. We show that the three-terminal tunneling conductance depends on the angle (θ) between the magnetization direction of the tip and the local orientation of the electron spin on the edge while the two terminal conductance is independent of this angle. We demonstrate that chiral injection of an electron into the helical Luttinger liquid (when θ is zero or π) is associated with fractionalization of the spin of the injected electron in addition to the fractionalization of its charge. We also point out a spin current amplification effect induced by the spin fractionalization.

  14. Scanning probe methods applied to molecular electronics

    Energy Technology Data Exchange (ETDEWEB)

    Pavlicek, Niko

    2013-08-01

    Scanning probe methods on insulating films offer a rich toolbox to study electronic, structural and spin properties of individual molecules. This work discusses three issues in the field of molecular and organic electronics. An STM head to be operated in high magnetic fields has been designed and built up. The STM head is very compact and rigid relying on a robust coarse approach mechanism. This will facilitate investigations of the spin properties of individual molecules in the future. Combined STM/AFM studies revealed a reversible molecular switch based on two stable configurations of DBTH molecules on ultrathin NaCl films. AFM experiments visualize the molecular structure in both states. Our experiments allowed to unambiguously determine the pathway of the switch. Finally, tunneling into and out of the frontier molecular orbitals of pentacene molecules has been investigated on different insulating films. These experiments show that the local symmetry of initial and final electron wave function are decisive for the ratio between elastic and vibration-assisted tunneling. The results can be generalized to electron transport in organic materials.

  15. Measurement of electron beam polarization at the SLC

    International Nuclear Information System (INIS)

    Steiner, H.; California Univ., Berkeley

    1988-01-01

    One of the unique features of the SLC is its capability to accelerate longitudinally polarized electrons. The SLC polarization group has been performed to implement the polarization program at the SLC. Technically the polarization project consists of three main parts: (1) a polarized source, (2) spin-rotating superconducting solenoid magnets to be used to manipulate the direction of the electron spin, and (3) the polarimeters needed to monitor and measure the electron beam polarization. It is this last topic that will concern us here. Two types of polarimeters will be used - Compton and Moeller. (orig./HSI)

  16. Polarized electronic sources for future e+/e- linear colliders

    International Nuclear Information System (INIS)

    Tang, H.; Alley, R.K.; Clendenin, J.E.

    1997-05-01

    Polarized electron beams will play a crucial role in maximizing the physics potential for future e + /e - linear colliders. We will review the SLC polarized electron source (PES), present a design for a conventional PES for the Next Linear Collider (NLC), and discuss the physics issues of a polarized RF gun

  17. Polarized Light Sources for photocathode electron guns at SLAC

    International Nuclear Information System (INIS)

    Woods, M.; Frisch, J.; Witte, K.; Zolotorev, M.

    1992-12-01

    We describe current and future Polarized Light Sources at SLAC for use with photocathode electron guns to produce polarized electron beams. The SLAC experiments SLD and E142 are considered, and are used to define the required parameters for the Polarized Light Sources

  18. Electron and nuclear spin system polarization in semiconductors by light

    Energy Technology Data Exchange (ETDEWEB)

    Zakharchenya, B; Flejsher, V

    1981-02-01

    Discussed are the principles of optical electron spin orientation, dynamic polarization and cooling of nuclear spin systems in optical electron orientation, and behavioural characteristics of bound electron and nuclear spin systems of a semiconductor in the optical orientation situation.

  19. Measurement of electron beam polarization at the SLC

    International Nuclear Information System (INIS)

    Steiner, H.

    1987-03-01

    The polarimeters needed to monitor and measure electron beam polarization at the Stanford Linear Collider are discussed. Two types of polarimeters, are to be used. The first is based on the spin dependent elastic scattering of photons from high energy electrons. The second utilizes the spin dependence of elastic electron-electron scattering. The plans of the SLC polarization group to measure and monitor electron beam polarization are discussed. A brief discussion of the physics and the demands it imposes on beam polarization measurements is presented. The Compton polarimeter and the essential characteristics of two Moeller polarimeters are presented

  20. Optically pumped electron spin polarized targets for use in the production of polarized ion beams

    International Nuclear Information System (INIS)

    Anderson, L.W.

    1979-01-01

    The production of relatively dense electron spin polarized alkali metal vapor targets by optical pumping with intense cw dye lasers is discussed. The target density and electron spin polarization depend on the dye laser intensity and bandwidth, the magnetic field at the target, and the electron spin depolarization time. For example in a magnetic field of 1.5 x 10 3 G, and using 1 W dye laser with a bandwidth of 10 10 Hz one can construct an electron spin polarized Na vapor target with a target thickness of 1.6 x 10 13 atoms/cm 2 and an average electron spin polarization of about 90% even though the Na atoms are completely depolarized at every wall collision. Possible uses of the electron spin polarized targets for the production of intense beams of polarized H - or 3 He - ions are discussed. (orig.)

  1. Standardless quantification methods in electron probe microanalysis

    Energy Technology Data Exchange (ETDEWEB)

    Trincavelli, Jorge, E-mail: trincavelli@famaf.unc.edu.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Medina Allende s/n, Ciudad Universitaria, 5000 Córdoba (Argentina); Limandri, Silvina, E-mail: s.limandri@conicet.gov.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Instituto de Física Enrique Gaviola, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Medina Allende s/n, Ciudad Universitaria, 5000 Córdoba (Argentina); Bonetto, Rita, E-mail: bonetto@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas Dr. Jorge Ronco, Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, Facultad de Ciencias Exactas, de la Universidad Nacional de La Plata, Calle 47 N° 257, 1900 La Plata (Argentina)

    2014-11-01

    The elemental composition of a solid sample can be determined by electron probe microanalysis with or without the use of standards. The standardless algorithms are quite faster than the methods that require standards; they are useful when a suitable set of standards is not available or for rough samples, and also they help to solve the problem of current variation, for example, in equipments with cold field emission gun. Due to significant advances in the accuracy achieved during the last years, product of the successive efforts made to improve the description of generation, absorption and detection of X-rays, the standardless methods have increasingly become an interesting option for the user. Nevertheless, up to now, algorithms that use standards are still more precise than standardless methods. It is important to remark, that care must be taken with results provided by standardless methods that normalize the calculated concentration values to 100%, unless an estimate of the errors is reported. In this work, a comprehensive discussion of the key features of the main standardless quantification methods, as well as the level of accuracy achieved by them is presented. - Highlights: • Standardless methods are a good alternative when no suitable standards are available. • Their accuracy reaches 10% for 95% of the analyses when traces are excluded. • Some of them are suitable for the analysis of rough samples.

  2. Feasibility studies of a polarized positron source based on the Bremsstrahlung of polarized electrons

    International Nuclear Information System (INIS)

    Dumas, J.

    2011-09-01

    The nuclear and high-energy physics communities have shown a growing interest in the availability of high current, highly-polarized positron beams. A sufficiently energetic polarized photon or lepton incident on a target may generate, via Bremsstrahlung and pair creation within a solid target foil, electron-positron pairs that should carry some fraction of the initial polarization. Recent advances in high current (> 1 mA) spin polarized electron sources at Jefferson Lab offer the perspective of creating polarized positrons from a low energy electron beam. This thesis discusses polarization transfer from electrons to positrons in the perspective of the design optimization of a polarized positron source. The PEPPo experiment, aiming at a measurement of the positron polarization from a low energy (< 10 MeV) highly spin polarized electron beam is discussed. A successful demonstration of this technique would provide an alternative scheme for the production of low energy polarized positrons and useful information for the optimization of the design of polarized positron sources in the sub-GeV energy range. (author)

  3. Molecular electron recollision dynamics in intense circularly polarized laser pulses

    Science.gov (United States)

    Bandrauk, André D.; Yuan, Kai-Jun

    2018-04-01

    Extreme UV and x-ray table top light sources based on high-order harmonic generation (HHG) are focused now on circular polarization for the generation of circularly polarized attosecond pulses as new tools for controlling electron dynamics, such as charge transfer and migration and the generation of attosecond quantum electron currents for ultrafast magneto-optics. A fundamental electron dynamical process in HHG is laser induced electron recollision with the parent ion, well established theoretically and experimentally for linear polarization. We discuss molecular electron recollision dynamics in circular polarization by theoretical analysis and numerical simulation. The control of the polarization of HHG with circularly polarized ionizing pulses is examined and it is shown that bichromatic circularly polarized pulses enhance recollision dynamics, rendering HHG more efficient, especially in molecules because of their nonspherical symmetry. The polarization of the harmonics is found to be dependent on the compatibility of the rotational symmetry of the net electric field created by combinations of bichromatic circularly polarized pulses with the dynamical symmetry of molecules. We show how the field and molecule symmetry influences the electron recollision trajectories by a time-frequency analysis of harmonics. The results, in principle, offer new unique controllable tools in the study of attosecond molecular electron dynamics.

  4. Electron Cyclotron Waves Polarization in the TJII Stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Cappa, A.; Martinez-Fernandez, J.; Wagner, D.

    2013-05-01

    This report describes the theoretical calculations related with the electron cyclotron (EC) waves polarization control in the TJII stellarator. Two main aspects will be distinguished: the determination of the vacuum polarization that the wave must exhibit if a given propagation mode in a cold plasma is desired and the calculation of the behavior of the grooved polarizers and other transmission systems used to launch the vacuum wave with the required polarization. (Author) 13 refs.

  5. Scattering of polarized low-energy electrons by ferromagnetic metals

    International Nuclear Information System (INIS)

    Helman, J.S.

    1981-01-01

    A source of spin polarized electrons with remarkable characteristics based on negative electron affinity (NEA) GaAs has recently been developed. It constitutes a unique tool to investigate spin dependent interactions in electron scattering processes. The characteristics and working principles of the source are briefly described. Some theoretical aspects of the scattering of polarized low-energy electrons by ferromagnetic metals are discussed. Finally, the results of the first polarized low-energy electron diffraction experiment using the NEA GaAs source are reviewed; they give information about the surface magnetization of ferromagnetic Ni (110). (Author) [pt

  6. Variations of the electron concentration in the polar ionosphere

    International Nuclear Information System (INIS)

    Chasovitin, Yu.K.; Shushkova, V.B.

    1980-01-01

    The possibility of constructing an empirical model of electron concentration in the polar ionosphere is considered. The results of rocket measurements carried out at Fort Churchill and on the Hays island at 70-210 km heights are used to analyse the distribution of electron concentration in the non-illuminated sector of the auroral oval, in the subauroral ionosphere and in the polar cap. Taking account of magnetospheric-ionospheric relationships and the geomagnetic environment, certain regularities in the distribution of electron concentration in the polar field, which may serve as a basis for constructing an empirical model of the polar ionosphere have been identified

  7. Latest polarization and beam characterization results of the Orsay polarized electron source

    International Nuclear Information System (INIS)

    Arianer, J.; Cohen, S.; Essabaa, S.; Frascaria, R.; Zerhouni, O.

    1995-01-01

    The Orsay polarized electron source based on the chemi-ionization of aligned He(2 3 S 1 ) atoms and CO 2 molecules is briefly described. The latest results concerning electron polarization and beam emittance are presented. The present development status is also discussed. (K.A.)

  8. Generation of valley-polarized electron beam in bilayer graphene

    International Nuclear Information System (INIS)

    Park, Changsoo

    2015-01-01

    We propose a method to produce valley-polarized electron beams using a bilayer graphene npn junction. By analyzing the transmission properties of electrons through the junction with zigzag interface in the presence of trigonal warping, we observe that there exist a range of incident energies and barrier heights in which transmitted electrons are well polarized and collimated. From this observation and by performing numerical simulations, it is demonstrated that valley-dependent electronic currents with nearly perfect polarization can be generated. We also show that the peak-to-peak separation angle between the polarized currents is tunable either by incident energy or by barrier height each of which is controlled by using top and back gate voltages. The results can be used for constructing an electron beam splitter to produce valley-polarized currents

  9. Generation of valley-polarized electron beam in bilayer graphene

    Science.gov (United States)

    Park, Changsoo

    2015-12-01

    We propose a method to produce valley-polarized electron beams using a bilayer graphene npn junction. By analyzing the transmission properties of electrons through the junction with zigzag interface in the presence of trigonal warping, we observe that there exist a range of incident energies and barrier heights in which transmitted electrons are well polarized and collimated. From this observation and by performing numerical simulations, it is demonstrated that valley-dependent electronic currents with nearly perfect polarization can be generated. We also show that the peak-to-peak separation angle between the polarized currents is tunable either by incident energy or by barrier height each of which is controlled by using top and back gate voltages. The results can be used for constructing an electron beam splitter to produce valley-polarized currents.

  10. Characterization of a microfocused circularly polarized x-ray probe

    International Nuclear Information System (INIS)

    Pollmann, J.; Srajer, G.; Maser, J.; Lang, J. C.; Nelson, C. S.; Venkataraman, C. T.; Isaacs, E. D.

    2000-01-01

    We report on the development of a circularly polarized x-ray microprobe in the intermediate energy range from 5 to 10 keV. In this experiment linearly polarized synchrotron radiation was circularly polarized by means of a Bragg-diffracting diamond phase retarder and subsequently focused down to a spot size of about 4x2 μm 2 by a Fresnel zone plate. The properties of the microprobe were characterized, and the technique was applied to the two-dimensional mapping of magnetic domains in HoFe 2 . (c) 2000 American Institute of Physics

  11. Imaging differential polarization microscope with electronic readout

    International Nuclear Information System (INIS)

    Mickols, W.; Tinoco, I.; Katz, J.E.; Maestre, M.F.; Bustamante, C.

    1985-01-01

    A differential polarization microscope forms two images: one of the transmitted intensity and the other due to the change in intensity between images formed when different polarizations of light are used. The interpretation of these images for linear dichroism and circular dichroism are described. The design constraints on the data acquisition systems and the polarization modulation are described. The advantage of imaging several biological systems which contain optically anisotropic structures are described

  12. Probing the f(R) formalism through gravitational wave polarizations

    International Nuclear Information System (INIS)

    Alves, M.E.S.; Miranda, O.D.; Araujo, J.C.N. de

    2009-01-01

    The direct observation of gravitational waves (GW) in the near future, and the corresponding determination of the number of independent polarizations, is a powerful tool to test general relativity and alternative theories of gravity. In the present work we use the Newman-Penrose formalism to characterize GWs in quadratic gravity and in a particular class of f(R) Lagrangians. We find that both quadratic gravity and the f(R) theory belong to the most general invariant class of GWs, i.e., they can present up to six independent polarizations of GWs. For a particular combination of the parameters, we find that quadratic gravity can present up to five polarizations states. On the other hand, if we use the Palatini approach for f(R) theories, GWs present only the usual two transverse-traceless polarizations such as in general relativity. Thus, we conclude that the observation of GWs can strongly constrain the suitable formalism for these theories.

  13. Polarization Studies for the eRHIC Electron Storage Ring

    Energy Technology Data Exchange (ETDEWEB)

    Gianfelice-Wendt, Eliana [Fermilab; Tepikian, S. [Brookhaven

    2018-04-01

    A hadron/lepton collider with polarized beams has been under consideration by the scientific community since some years, in the U.S. and Europe. Among the various proposals, those by JLAB and BNL with polarized electron and proton beams are currently under closer study in the U.S. Experimenters call for the simultaneous storage of electron bunches with both spin helicity. In the BNL based Ring-Ring design, electrons are stored at top energy in a ring to be accommodated in the existing RHIC tunnel. The transversely polarized electron beam is injected into the storage ring at variable energies, between 5 and 18 GeV. Polarization is brought into the longitudinal direction at the IP by a couple of spin rotators. In this paper results of first studies of the attainable beam polarization level and lifetime in the storage ring at 18 GeV are presented.

  14. Spin polarized electron tunneling and magnetoresistance in molecular junctions.

    Science.gov (United States)

    Szulczewski, Greg

    2012-01-01

    This chapter reviews tunneling of spin-polarized electrons through molecules positioned between ferromagnetic electrodes, which gives rise to tunneling magnetoresistance. Such measurements yield important insight into the factors governing spin-polarized electron injection into organic semiconductors, thereby offering the possibility to manipulate the quantum-mechanical spin degrees of freedom for charge carriers in optical/electrical devices. In the first section of the chapter a brief description of the Jullière model of spin-dependent electron tunneling is reviewed. Next, a brief description of device fabrication and characterization is presented. The bulk of the review highlights experimental studies on spin-polarized electron tunneling and magnetoresistance in molecular junctions. In addition, some experiments describing spin-polarized scanning tunneling microscopy/spectroscopy on single molecules are mentioned. Finally, some general conclusions and prospectus on the impact of spin-polarized tunneling in molecular junctions are offered.

  15. The S-DALINAC polarized electron injector SPIN

    Energy Technology Data Exchange (ETDEWEB)

    Eckardt, Christian; Bahlo, Thore; Bangert, Phillip; Barday, Roman; Bonnes, Uwe; Brunken, Marco; Burandt, Christoph; Eichhorn, Ralf; Enders, Joachim; Espig, Martin; Platz, Markus; Poltoratska, Yuliya; Roth, Markus; Schneider, Fabian; Wagner, Markus; Weber, Antje; Zwicker, Benjamin [Institut fuer Kernphysik, Technische Universitaet, Darmstadt (Germany); Ackermann, Wolfgang; Mueller, Wolfgang F.O.; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder, Technische Universitaet, Darmstadt (Germany); Aulenbacher, Kurt [Institut fuer Kernphysik, Johannes Gutenberg-Universitaet, Mainz (Germany)

    2011-07-01

    A source of polarized electrons has been installed at the superconducting 130 MeV Darmstadt electron linac S-DALINAC. Polarized electrons are generated by irradiating a GaAs cathode with pulsed Ti:Sapphire and diode lasers and preaccelerated to 100 keV. A Wien filter and 100 keV Mott polarimeter are used for spin manipulation and polarization measurement and various beam diagnostic elements are installed. To measure the beam polarization downstream of the superconducting injector linac a 5-10 MeV Mott polarimeter and a Compton-transmission polarimeter have been developed. We report on the status of the polarized electron source and foreseen experiments.

  16. Photoassisted Kelvin probe force microscopy at GaN surfaces: The role of polarity

    Science.gov (United States)

    Wei, J. D.; Li, S. F.; Atamuratov, A.; Wehmann, H.-H.; Waag, A.

    2010-10-01

    The behavior of GaN surfaces during photoassisted Kelvin probe force microscopy is demonstrated to be strongly dependant on surface polarity. The surface photovoltage of GaN surfaces illuminated with above-band gap light is analyzed as a function of time and light intensity. Distinct differences between Ga-polar and N-polar surfaces could be identified, attributed to photoinduced chemisorption of oxygen during illumination. These differences can be used for a contactless, nondestructive, and easy-performable analysis of the polarity of GaN surfaces.

  17. Remote operation of a fully shielded electron probe microanalyser

    International Nuclear Information System (INIS)

    Rowe, J.; Sparry, R.P.

    1977-11-01

    A 'Microscan 5' Cambridge Instrument Company electron probe micro-analyser has been equipped with full shielding to enable high radioactive materials to be examined. The transfer of controls for remote operation are described. (author)

  18. Polarization as a probe of high energy physics

    International Nuclear Information System (INIS)

    Moravcsik, M.J.

    1985-07-01

    An outline is given of the particular physical and mathematical point of view taken with respect to the exploration of polarization phenomena in particle physics, and some of the results are discussed. The quantum mechanical formalism is provided in terms of the reaction matrix and spin tensors. The applications of the optimal formalism to polarization phenomena and the results obtained from it are discussed. The four principal applications discussed are: testing of symmetry laws, determination of amplitudes from experimental data, testing of specific existing theoretical models, and searching for clues of dynamics in the situations in which knowledge of the particle dynamics is nonexistent or unreliable. 44 refs., 21 figs

  19. THE MAGNETIC FIELD IN TAURUS PROBED BY INFRARED POLARIZATION

    International Nuclear Information System (INIS)

    Chapman, Nicholas L.; Goldsmith, Paul F.; Pineda, Jorge L.; Li Di; Clemens, D. P.; Krco, Marko

    2011-01-01

    We present maps of the plane-of-sky magnetic field within two regions of the Taurus molecular cloud: one in the dense core L1495/B213 filament and the other in a diffuse region to the west. The field is measured from the polarization of background starlight seen through the cloud. In total, we measured 287 high-quality near-infrared polarization vectors in these regions. In L1495/B213, the percent polarization increases with column density up to A V ∼ 9 mag, the limits of our data. The radiative torques model for grain alignment can explain this behavior, but models that invoke turbulence are inconsistent with the data. We also combine our data with published optical and near-infrared polarization measurements in Taurus. Using this large sample, we estimate the strength of the plane-of-sky component of the magnetic field in nine subregions. This estimation is done with two different techniques that use the observed dispersion in polarization angles. Our values range from 5 to 82 μG and tend to be higher in denser regions. In all subregions, the critical index of the mass-to-magnetic flux ratio is sub-unity, implying that Taurus is magnetically supported on large scales (∼2 pc). Within the region observed, the B213 filament takes a sharp turn to the north and the direction of the magnetic field also takes a sharp turn, switching from being perpendicular to the filament to becoming parallel. This behavior can be understood if we are observing the rim of a bubble. We argue that it has resulted from a supernova remnant associated with a recently discovered nearby gamma-ray pulsar.

  20. Electron spin polarization effects in low energy electron diffraction, ion neutralization and metastable atom deexcitation at solid surfaces. Progress report No. 4, 1 January-31 December 1984

    International Nuclear Information System (INIS)

    1984-01-01

    In the present contract year, a GaAs polarized electron source has been used to undertake a polarized LEED study of order-disorder transformations at Cu 3 Au (100) and (111) surfaces. A polarized LEED study of Cu (100) has also been initiated. A polarized MDS study of Ni(110) surface magnetism has been completed. Spin dependences in the Auger electron yield were observed that provide a measure of the surface magnetism and were used to probe the dependence of surface magnetism on temperature and adsorbate coverage. A similar study using a ferromagnetic glass is now underway. A Mott polarization analyzer, constructed to measure the ESP of the ejected electrons, is also being installed on the apparatus. Such measurements provide direct information concerning the dynamics of secondary electron ejection and the details of adsorbate-substrate bonding

  1. On the possibility of obtaining high-energy polarized electrons on Yerevan synchrotron

    International Nuclear Information System (INIS)

    Melikyan, R.A.

    1975-01-01

    A possibility of producing high-energy polarized electrons on the Yerevan synchrotron is discussed. A review of a number of low-energy polarized electron sources and of some of experiments with high-energy polarized electrons is given

  2. Optical Polarization as a Probe of the Local Interstellar Medium

    Science.gov (United States)

    Tinbergen, J.

    1984-01-01

    The use of interstellar polarization as a tool for measuring interstellar dust is discussed. Problems resulting from dust and magnetic field configurations becoming mixed up are discussed, as is the availability of sufficiently bright stars to obtain the photons needed for precision measurements. It is proposed that: (1) on the scale of several hundred parsec, there is a preferential magnetic field direction, as evidenced by observations at the Galactic poles and selected longitudes in the Galactic plane; (2) the local (r 50 pc) region is devoid of dust, as evidenced by the mean square degree of polarization as a function of distance; and, less certainly, that (3) at a distance of less than 5 pc, there is a patch of dust which may be of interest in connection with cloud models.

  3. Electron and nuclear spin system polarization in semiconductors by light

    International Nuclear Information System (INIS)

    Zakharchenya, B.; Flejsher, V.

    1981-01-01

    Discussed are the principles of optical electron spin orientation, dynamic polarization and cooling of nuclear spin systems in optical electron orientation, and behavioural characteristics of bound electron and nuclear spin systems of a semiconductor in the optical orientation situation. (J.P.)

  4. 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

  5. Measurement of Quarkonium polarization to probe QCD at the LHC

    International Nuclear Information System (INIS)

    Knünz, V.

    2015-01-01

    With the first proton-proton collisions in the Large Hadron Collider (LHC) at CERN in 2010, a new era in high energy physics has been initiated. The data collected by the various experiments open up the possibility to study standard model processes with high precision, in new areas of phase space. The LHC provides excellent conditions for studies of quarkonium production, due to the high quarkonium production rates given the high center-of-mass energy and high instantaneous luminosity of the colliding proton beams. Studies of the production of heavy quarkonium mesons - bound states of a heavy quark and its respective antiquark - are very important to improve our understanding of hadron formation. Until quite recently, experimental and phenomenological efforts have not resulted in a satisfactory overall picture of quarkonium production cross sections and quarkonium polarizations. The Compact Muon Solenoid (CMS) detector is ideally suited to study quarkonium production in the experimentally very clean dimuon decay channel, up to considerably higher values of transverse momentum than accessible in previous experiments. The scope of this thesis is to describe in detail the measurements of the polarizations of the Upsilon(nS) bottomonium states and (in less detail) of the Psi(nS) charmonium states, based on a dimuon data sample collected with the CMS detector in proton-proton collisions at a center-of-mass energy of 7 TeV. Surprisingly, no significant polarizations were found in any of the studied quarkonium states, in none of the studied reference frames, nor in a frame-independent analysis. From an experimental point of view, these results, together with recent results from other experiments, clarify the confusing picture originating from previous measurements, which were plagued by experimental ambiguities and inconsistencies. The currently most favored approach to model and understand quarkonium production is non-relativistic quantum chromodynamics (NRQCD), a QCD

  6. Progress on a cryogenically cooled RF gun polarized electron source

    Energy Technology Data Exchange (ETDEWEB)

    Fliller, R.P., III; Edwards, H.; /Fermilab

    2006-08-01

    RF guns have proven useful in multiple accelerator applications. An RF gun capable of producing polarized electrons is an attractive electron source for the ILC or an electron-ion collider. Producing such a gun has proven elusive. The NEA GaAs photocathode needed for polarized electron production is damaged by the vacuum environment in an RF gun. Electron and ion back bombardment can also damage the cathode. These problems must be mitigated before producing an RF gun polarized electron source. In this paper we report continuing efforts to improve the vacuum environment in a normal conducting RF gun by cooling it with liquid nitrogen after a high temperature vacuum bake out. We also report on a design of a cathode preparation chamber to produce bulk GaAs photocathodes for testing in such a gun. Future directions are also discussed.

  7. Pygmy resonances probed with electron scattering

    International Nuclear Information System (INIS)

    Bertulani, C.A.

    2007-01-01

    Pygmy resonances in light nuclei excited in electron scattering are discussed. These collective modes will be explored in future electron-ion colliders such as ELISe/FAIR (spokesperson: Haik Simon - GSI). Response functions for direct breakup are explored with few-body and hydrodynamical models, including the dependence upon final state interactions

  8. Operating experience with the polarized electron gun at SLAC

    International Nuclear Information System (INIS)

    Alguard, M.J.; Baum, G.; Clendenin, J.E.; Hughes, V.W.; Lubell, M.S.; Miller, R.H.; Raith, W.; Schuler, K.P.; Sodja, J.

    1977-03-01

    During the two years of operation of the SLAC Polarized Electron Gun (PEGGY), the electron intensity delivered to the target has increased from 7 x 10 7 e - /pulse to 1 x 10 9 e - /pulse. The polarization is 0.85 with no measurable degradation caused by acceleration through the linear accelerator. The predominant cause of downtime is replenishment of lithium, which now averages 43 hours. The lifetime of a lithium load is about 175 hours

  9. Polarized electron sources for linear colliders

    International Nuclear Information System (INIS)

    Clendenin, J.E.; Ecklund, S.D.; Miller, R.H.; Schultz, D.C.; Sheppard, J.C.

    1992-07-01

    Linear colliders require high peak current beams with low duty factors. Several methods to produce polarized e - beams for accelerators have been developed. The SLC, the first linear collider, utilizes a photocathode gun with a GaAs cathode. Although photocathode sources are probably the only practical alternative for the next generation of linear colliders, several problems remain to be solved, including high voltage breakdown which poisons the cathode, charge limitations that are associated with the condition of the semiconductor cathode, and a relatively low polarization of ≤5O%. Methods to solve or at least greatly reduce the impact of each of these problems are at hand

  10. Tantalum surface oxidation: Bond relaxation, energy entrapment, and electron polarization

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yongling [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Bo, Maolin [Yangtze Normal University, College of Mechanical and Electrical Engineering, Chongqing 408100 (China); Wang, Yan [School of Information and Electronic Engineering, Hunan University of Science and Technology, Hunan 411201 (China); Liu, Yonghui [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Sun, Chang Q. [NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Huang, Yongli, E-mail: huangyongli@xtu.edu.cn [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China)

    2017-02-28

    Graphical abstract: The bond, electron and energy relaxation result in core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Highlights: • Increasing the oxygen coverage lowers the adsorption energy associated with lattice reconstruction. • Electrons transfer from Ta surface atoms to sp-hydrated oxygen, creating dipole moment that decreases the work function. • Oxygen chemisorption modified valence density-of-state (DOS) for Ta with four excessive DOS features: O−Ta bonding, O{sup 2−} lone pairs, Ta+ electron holes, and the lone-pair polarized Ta dipoles. • The bond, electron and energy relaxation between surface undercoordinated atoms are responsible for core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Abstract: A combination of photoelectron spectrometric analysis and density functional theory calculations has enabled reconciliation of the bond-energy-electron relaxation for the Ta(100, 110, 111) surfaces chemisorbed with oxygen at different coverages. Results show that increasing oxygen coverage lowers the adsorption energy associated with lattice reconstruction. Valence electrons transfer from Ta surface atoms to oxygen to create four excessive DOS features in terms of O−Ta bonding, lone pairs of oxygen, Ta{sup +} electron holes, and polarized Ta dipoles. Oxidation proceeds in the following dynamics: oxygen gets electrons from two neighboring Ta atoms left behind Ta{sup +}; the sp{sup 3}-orbital hybridization takes place with additional two electron lone pairs, the lone pairs polarize the other two Ta neighbors becoming dipoles. X-ray photoelectron spectral analysis results in the 4f binding energy of an isolated Ta atom and its shift upon bond formation and oxidation. Exercises provide not only a promising numerical approach for the quantitative information about the bond and electronic behavior but also consistent

  11. Tantalum surface oxidation: Bond relaxation, energy entrapment, and electron polarization

    International Nuclear Information System (INIS)

    Guo, Yongling; Bo, Maolin; Wang, Yan; Liu, Yonghui; Sun, Chang Q.; Huang, Yongli

    2017-01-01

    Graphical abstract: The bond, electron and energy relaxation result in core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Highlights: • Increasing the oxygen coverage lowers the adsorption energy associated with lattice reconstruction. • Electrons transfer from Ta surface atoms to sp-hydrated oxygen, creating dipole moment that decreases the work function. • Oxygen chemisorption modified valence density-of-state (DOS) for Ta with four excessive DOS features: O−Ta bonding, O"2"− lone pairs, Ta+ electron holes, and the lone-pair polarized Ta dipoles. • The bond, electron and energy relaxation between surface undercoordinated atoms are responsible for core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Abstract: A combination of photoelectron spectrometric analysis and density functional theory calculations has enabled reconciliation of the bond-energy-electron relaxation for the Ta(100, 110, 111) surfaces chemisorbed with oxygen at different coverages. Results show that increasing oxygen coverage lowers the adsorption energy associated with lattice reconstruction. Valence electrons transfer from Ta surface atoms to oxygen to create four excessive DOS features in terms of O−Ta bonding, lone pairs of oxygen, Ta"+ electron holes, and polarized Ta dipoles. Oxidation proceeds in the following dynamics: oxygen gets electrons from two neighboring Ta atoms left behind Ta"+; the sp"3-orbital hybridization takes place with additional two electron lone pairs, the lone pairs polarize the other two Ta neighbors becoming dipoles. X-ray photoelectron spectral analysis results in the 4f binding energy of an isolated Ta atom and its shift upon bond formation and oxidation. Exercises provide not only a promising numerical approach for the quantitative information about the bond and electronic behavior but also consistent insight into the

  12. Electronic control system for irradiation probes

    International Nuclear Information System (INIS)

    Gluza, E.; Neumann, J.; Zahalka, F.

    1980-01-01

    The EROS-78 system for the supply and power control of six heating sections of the irradiation probe of the CHOUCA type placed in the reactor vessel is described. The system allows temperature control at the location of the heat sensor with an accuracy of +-1% of the rated value within the region of 100 to 1000 degC. The equipment is provided with its own quartz controlled clock. The temperature is picked up by a chromel-alumel jacket thermocouple. The power input of the heating elements is thyristor controlled. (J.B.)

  13. 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.)

  14. Electron distribution in polar heterojunctions within a realistic model

    Energy Technology Data Exchange (ETDEWEB)

    Tien, Nguyen Thanh, E-mail: thanhtienctu@gmail.com [College of Natural Science, Can Tho University, 3-2 Road, Can Tho City (Viet Nam); Thao, Dinh Nhu [Center for Theoretical and Computational Physics, College of Education, Hue University, 34 Le Loi Street, Hue City (Viet Nam); Thao, Pham Thi Bich [College of Natural Science, Can Tho University, 3-2 Road, Can Tho City (Viet Nam); Quang, Doan Nhat [Institute of Physics, Vietnamese Academy of Science and Technology, 10 Dao Tan Street, Hanoi (Viet Nam)

    2015-12-15

    We present a theoretical study of the electron distribution, i.e., two-dimensional electron gas (2DEG) in polar heterojunctions (HJs) within a realistic model. The 2DEG is confined along the growth direction by a triangular quantum well with a finite potential barrier and a bent band figured by all confinement sources. Therein, interface polarization charges take a double role: they induce a confining potential and, furthermore, they can make some change in other confinements, e.g., in the Hartree potential from ionized impurities and 2DEG. Confinement by positive interface polarization charges is necessary for the ground state of 2DEG existing at a high sheet density. The 2DEG bulk density is found to be increased in the barrier, so that the scattering occurring in this layer (from interface polarization charges and alloy disorder) becomes paramount in a polar modulation-doped HJ.

  15. Polarized positrons and electrons at the linear collider

    International Nuclear Information System (INIS)

    Moortgat-Pick, G.; Abe, T.; Alexander, G.; Ananthanarayan, B.; Babich, A.A.; Bharadwaj, V.; Barber, D.; Bartl, A.; Brachmann, A.; Chen, S.; Clarke, J.; Clendenin, J.E.; Dainton, J.; Desch, K.; Diehl, M.; Dobos, B.; Dorland, T.; Dreiner, H.K.; Eberl, H.; Ellis, J.

    2008-01-01

    The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization

  16. Study of polarization properties of fiber-optics probes with use of a binary phase plate.

    Science.gov (United States)

    Alferov, S V; Khonina, S N; Karpeev, S V

    2014-04-01

    We conduct a theoretical and experimental study of the distribution of the electric field components in the sharp focal domain when rotating a zone plate with a π-phase jump placed in the focused beam. Comparing the theoretical and experimental results for several kinds of near-field probes, an analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and an increase of the probe's energy throughput.

  17. Parity violating asymmetries in polarized electron scattering

    International Nuclear Information System (INIS)

    Derman, E.; Marciano, W.J.

    1979-01-01

    We discuss parity violating asymmetries between the scattering of right and left-handed electrons on a variety of targets. Implications for gauge theories from recent SLAC results on deep-inelastic electron-deuterium and electron-proton scattering are examined. A derivation of the asymmetry for electron-electron scattering is given, its advantages are pointed out, and the feasibility of such a measurement is discussed. Other proposed or contemplated asymmetry experiments are reviewed and the necessity of including the Collins-Wilczek-Zee hadronic axial isoscalar current contribution in asymmetry predictions is noted

  18. Probing the magnetsophere with artificial electron beams

    International Nuclear Information System (INIS)

    Winckler, J.R.

    1981-01-01

    An analysis is conducted of the University of Minnesota Electron Echo experiments, which so far have included five sounding rocket experiments. The concept of the Echo experiment is to inject electron beam pulses from a rocket into the ionosphere at altitudes in the range from 100 to 300 km. The electrons move to the conjugate hemisphere following magnetic field lines and return on neighboring field lines to the neighborhood of the rocket where the pulses may be detected and analyzed. Attention is given to the detection and analysis of echoes, the structure of echoes, and the Echo V experiment. The Echo V experiment showed clearly that detection of remote echo beams by atmospheric fluorescence using low light level TV system is not a viable technique. A future experiment is to use throw-away detectors for direct remote echo detection

  19. Measurement of Quarkonium Polarization to Probe QCD at the LHC

    CERN Document Server

    Knunz, Valentin Karl; Strauss, Josef

    2015-01-01

    With the first proton-proton collisions in the Large Hadron Collider (LHC) at CERNin 2010, a new era in high energy physics has been initiated. The data collected bythe various experiments open up the possibility to study standard model processes withhigh precision, in new areas of phase space. The LHC provides excellent conditions forstudies of quarkonium production, due to the high quarkonium production rates giventhe high center-of-mass energy and high instantaneous luminosity of the colliding protonbeams. Studies of the production of heavy quarkonium mesons – bound states of a heavyquark and its respective antiquark – are very important to improve our understanding ofhadron formation. Until quite recently, experimental and phenomenological efforts havenot resulted in a satisfactory overall picture of quarkonium production cross sections andquarkonium polarizations.The Compact Muon Solenoid (CMS) detector is ideally suited to study quarkoniumproduction in the experimentally very clean dimuon decay ch...

  20. A sensitive fluorescent probe for the polar solvation dynamics at protein-surfactant interfaces.

    Science.gov (United States)

    Singh, Priya; Choudhury, Susobhan; Singha, Subhankar; Jun, Yongwoong; Chakraborty, Sandipan; Sengupta, Jhimli; Das, Ranjan; Ahn, Kyo-Han; Pal, Samir Kumar

    2017-05-17

    Relaxation dynamics at the surface of biologically important macromolecules is important taking into account their functionality in molecular recognition. Over the years it has been shown that the solvation dynamics of a fluorescent probe at biomolecular surfaces and interfaces account for the relaxation dynamics of polar residues and associated water molecules. However, the sensitivity of the dynamics depends largely on the localization and exposure of the probe. For noncovalent fluorescent probes, localization at the region of interest in addition to surface exposure is an added challenge compared to the covalently attached probes at the biological interfaces. Here we have used a synthesized donor-acceptor type dipolar fluorophore, 6-acetyl-(2-((4-hydroxycyclohexyl)(methyl)amino)naphthalene) (ACYMAN), for the investigation of the solvation dynamics of a model protein-surfactant interface. A significant structural rearrangement of a model histone protein (H1) upon interaction with anionic surfactant sodium dodecyl sulphate (SDS) as revealed from the circular dichroism (CD) studies is nicely corroborated in the solvation dynamics of the probe at the interface. The polarization gated fluorescence anisotropy of the probe compared to that at the SDS micellar surface clearly reveals the localization of the probe at the protein-surfactant interface. We have also compared the sensitivity of ACYMAN with other solvation probes including coumarin 500 (C500) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM). In comparison to ACYMAN, both C500 and DCM fail to probe the interfacial solvation dynamics of a model protein-surfactant interface. While C500 is found to be delocalized from the protein-surfactant interface, DCM becomes destabilized upon the formation of the interface (protein-surfactant complex). The timescales obtained from this novel probe have also been compared with other femtosecond resolved studies and molecular dynamics simulations.

  1. Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers.

    Science.gov (United States)

    Kumar, Krishan; Moudgil, R K

    2012-10-17

    We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

  2. Polarized target physics at the Bonn electron accelerators

    International Nuclear Information System (INIS)

    Meyer, W.

    1988-12-01

    At the BONN 2.5 GeV electron synchrotron experiments with polarized nucleon targets have a long tradition. Starting with measurements of the target asymmetry in single pion photoproduction off polarized protons, resp. neutrons, the experiments have been concentrated on photodisintegration measurements of polarized deuterons. Parallel to these activities a considerable progress in the field of the target technology, e.g. cryogenics and target materials, has been made, by which all the measurements have profitted enormously. Especially the development of the new target material ammonia has allowed the first use of a polarized deuteron (ND 3 ) target in an intense electron beam. The construction of a frozen spin target, which will be used in combination with a tagged polarized photon beam, makes a new generation of polarized target experiments in photon induced reactions possible. Together with electron scattering off polarized deuterons and neutrons they will be a main activity in the physics program at the new stretcher accelerator ELSA in BONN. (orig.)

  3. Development of spin-polarized transmission electron microscope

    International Nuclear Information System (INIS)

    Kuwahara, M; Saitoh, K; Tanaka, N; Takeda, Y; Ujihara, T; Asano, H; Nakanishi, T

    2011-01-01

    In order to study spin related phenomena in nano-size materials, spin-polarized electron source (PES) has been employed for the incident beam in transmission electron microscope (TEM). The PES has been designed and constructed with optimizing for spin-polarized TEM. The illuminating system of TEM is also designed to focus the spin-polarized electron beam emitted from a semiconductor photocathode with a negative electron affinity (NEA) surface. The beam energy is set to below 40 keV which is lower energy type as a TEM, because the spin interaction with condensed matters is very small corresponding with a Coulomb interaction. The polarized electron gun has realized in an extra high vacuum (XHV) condition and high field gradient of 4 MV/m on a surface of photocathode. Furthermore, it demonstrated that 40-keV polarized electron beam was operated with a sub-milli second pulse mode by using the backside excitation type photocathode. This high performance PES will make it possible to observe dynamically a magnetic field images with high contrast and highspeed temporal imaging in TEM.

  4. Formation of Electron Strings in Narrow Band Polar Semiconductors

    Science.gov (United States)

    Kusmartsev, F. V.

    2000-01-01

    We show that linear electron strings may arise in polar semiconductors. A single string consists of M spinless fermions trapped by an extended polarization well of a cigar shape. Inside the string the particles are free although they interact with each other via Coulomb forces. The strings arise as a result of an electronic phase separation associated with an instability of small adiabatic polarons. We have found the length of the string which depends on dielectric constants of semiconductors. The appearance of these electron strings may have an impact on the effect of stripe formation observed in a variety of high- Tc experiments.

  5. Statistics techniques applied to electron probe microanalysis

    International Nuclear Information System (INIS)

    Brizuela, H.; Del Giorgio, M.; Budde, C.; Briozzo, C.; Riveros, J.

    1987-01-01

    A description of Montroll-West's general theory for a tridimensional random walk of a particle with internal degrees of freedom is given, connecting this problem with the master equation solution. The possibility of its application to EPMA is discussed. Numerical solutions are given for thick or collimated beams at several energies interacting with samples of different shape and size. Spatial distribution of particles within the sample -for a stationary state- is analized, as well as the electron backscattering coefficient. (Author) [es

  6. Experiments with polarized electron beams at SLAC

    International Nuclear Information System (INIS)

    Cooper, P.

    1977-01-01

    Elastic and deep inelastic scattering of electrons on protons are studied. Cross sections for elastic scattering are plotted, and the parity nonconservation and neutral currents are diagramed for the deep inelastic scattering

  7. Production of spin-polarized unstable nuclei by using polarized electron capture process

    International Nuclear Information System (INIS)

    Shimizu, S.

    1998-01-01

    Measurements of emitted radiation from spin polarized nuclei are used to get information on electromagnetic moment of ground state unstable nuclei together with spin or parity state of excited states of their decayed (daughter) nuclei. These data are known to be useful for experimental investigation into the structure of unstable nuclei far from the stability line. The present study aims to establish a general method applicable to 11 Be and 16 N nuclei. To produce spin polarization, a new method in which the electron spin polarization of Rb is firstly produced by laser pumping, then the electron is transferred to the unstable nuclear beam (RNB) when they passes through the Rb vapor is proposed. Finally the polarized RNB will be implanted into superfluid helium to remain with a long spin-relaxation time. Future experimental set up for the above measurement adopted in the available radioactive nuclear beam facilities is briefly described. (Ohno, S.)

  8. Probing electron correlation and nuclear dynamics in Momentum Space

    International Nuclear Information System (INIS)

    Deleuze, M S; Hajgato, B; Morini, F; Knippenberg, S

    2010-01-01

    Orbital imaging experiments employing Electron Momentum Spectroscopy are subject to many complications, such as distorted wave effects, conformational mobility in the electronic ground state, ultra-fast nuclear dynamics in the final state, or a dispersion of the ionization intensity over electronically excited (shake-up) configurations of the cation. The purpose of the present contribution is to illustrate how a proper treatment of these complications enables us to probe in momentum space the consequences of electron correlation and nuclear dynamics in neutral and cationic states.

  9. Spin dynamics of electrons in strong fields studied via bremsstrahlung from a polarized electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Tashenov, Stanislav [Royal Institute of Technology, Stockholm (Sweden); Stockholm University (Sweden); Physikalisches Institut, Universitaet Heidelberg (Germany); Baeck, Torbjoern; Cederwall, Bo; Khaplanov, Anton; Schaessburger, Kai-Uwe [Royal Institute of Technology, Stockholm (Sweden); Barday, Roman; Enders, Joachim; Poltoratska, Yuliya [Institut fuer Kernphysik, Technische Universitaet, Darmstadt (Germany); Surzhykov, Andrey [Physikalisches Institut, Universitaet Heidelberg (Germany); GSI, Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany)

    2011-07-01

    Linear polarization of the photons emitted in the process of the atomic field electron bremsstrahlung has been studied at the newly developed 100 keV polarized electron source of TU Darmstadt. A correlation between the initial orientation of the electron spin and the degree and the angle of photon linear polarization has been measured for the first time. For this purpose a hard x-ray Compton polarimeter consisting of a segmented high purity germanium detector and an external passive photon scattering target have been applied. Linear polarization sensitive Compton and Rayleigh photon scattering distributions have been sampled by the segmented detector. The observed polarization correlation reveals a precession of the electron spin as it moves in the field of the nucleus. The full-relativistic calculations for the case of radiative recombination into a Rydberg series limit have been corroborated by the measurement. The results of this experiment suggest a new method for electron beam polarimetry.

  10. Fiber-optic polarization diversity detection for rotary probe optical coherence tomography.

    Science.gov (United States)

    Lee, Anthony M D; Pahlevaninezhad, Hamid; Yang, Victor X D; Lam, Stephen; MacAulay, Calum; Lane, Pierre

    2014-06-15

    We report a polarization diversity detection scheme for optical coherence tomography with a new, custom, miniaturized fiber coupler with single mode (SM) fiber inputs and polarization maintaining (PM) fiber outputs. The SM fiber inputs obviate matching the optical lengths of the X and Y OCT polarization channels prior to interference and the PM fiber outputs ensure defined X and Y axes after interference. Advantages for this scheme include easier alignment, lower cost, and easier miniaturization compared to designs with free-space bulk optical components. We demonstrate the utility of the detection system to mitigate the effects of rapidly changing polarization states when imaging with rotating fiber optic probes in Intralipid suspension and during in vivo imaging of human airways.

  11. Scattering of polarized electrons from polarized targets: Coincidence reactions and prescriptions for polarized half-off-shell single-nucleon cross sections

    International Nuclear Information System (INIS)

    Caballero, J.A.; Massachusetts Inst. of Tech., Cambridge, MA; Donnelly, T.W.; Massachusetts Inst. of Tech., Cambridge, MA; Poulis, G.I.; Massachusetts Inst. of Tech., Cambridge, MA

    1993-01-01

    Coincidence reactions of the type vector A( vector e, e'N)B involving the scattering of polarized electrons from polarized targets are discussed within the context of the plane-wave impulse approximation. Prescriptions are developed for polarized half-off single-nucleon cross sections; the different prescriptions are compared for typical quasi-free kinematics. Illustrative results are presented for coincidence polarized electron scattering from typical polarized nuclei. (orig.)

  12. Quantitative energy-dispersive electron probe X-ray microanalysis ...

    Indian Academy of Sciences (India)

    Abstract. An energy-dispersive electron probe X-ray microanalysis (ED-EPMA) technique us- ing an energy-dispersive X-ray detector with an ultra-thin window, designated as low-Z particle. EPMA, has been developed. The low-Z particle EPMA allows the quantitative determination of concentrations of low-Z elements such ...

  13. Polarization and magnetization of electronic matter

    International Nuclear Information System (INIS)

    Beck, G.

    1979-01-01

    The behaviour of a system of spin-electrons in a weak external electric or magnetic field is studied. Already in the case of a single free electron classical and quantum theory lead to different results concerning the Lorentz transformation of the magnetic moment (Thomas factor of spin-orbit coupling). The separation of the current into a convection and a spin part can be performed in a covariant way. While the convection current is responsible for the diamagnetism of a system, the spin current accounts for paramagnetic behaviour. After a Lorentz transformation of a diamagnetic system paraelectric components appear, while a paramagnetic system, after rransformation, exhibits dia-electric properties, epsilon 1) after a Lorentz transformation shows diamagnetic components, while a diaelectric system would acquire paramagnetic behaviour. Quantum electrodynamics leads to the result, that Dirac's electron vacuum behaves like a paramagnetic medium. It follows from this result, that the electron vacuum in a weak external electric field represents a diaelectric system. (Author) [pt

  14. Parity violation in polarized electron scattering

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1980-10-01

    The weak forces are responsible for the decay of radioactive nuclei, and it was in these decay processes where parity non-conservation was first observed. Beta decay occurs through emission of e + or e - particles, indicating that the weak force can carry charge of both signs, and it was natural to speculate on the existence of a neutral component of the weak force. Even though weak neutral forces had not been observed it was conjectured that a neutral component of weak decay could exist, and Zel'dovich in 1957 suggested that parity violating effects may be observable in electron scattering and in atomic spectra. More than twenty years have passed since the early conjectures, and a great deal has been learned. Progress in quantum field theory led to the development of the SU(2) x U(1) gauge theory of weak and electromagnetic interactions and provided a renormalizable theory with a minimum of additional assumptions. Gauge theories predicted the existence of a new force, the neutral current interaction. This new interaction was first seen in 1973 in the Gargamelle bubble chamber at CERN. Today the neutral currents are accepted as well established, and it is the details of the neutral current structure that occupy attention. In particular the role that electrons play cannot be tested readily in neutrino beams (recent neutrino-electron scattering experiments are, however, rapidly improving this situation) and therefore interest in electron-hadron neutral current effects has been high. Parity violation is a unique signature of weak currents, and measurements of its size are a particularly important and sensitive means for determining the neutral current structure

  15. Using electron irradiation to probe iron-based superconductors

    Science.gov (United States)

    Cho, Kyuil; Kończykowski, M.; Teknowijoyo, S.; Tanatar, M. A.; Prozorov, R.

    2018-06-01

    High-energy electron irradiation at low temperatures is an efficient and controlled way to create vacancy–interstitial Frenkel pairs in a crystal lattice, thereby inducing nonmagnetic point-like scattering centers. In combination with London penetration depth and resistivity measurements, the electron irradiation was used as a phase-sensitive probe to study the superconducting order parameter in iron-based superconductors (FeSCs), lending strong support to sign-changing s ± pairing. Here, we review the key results of the effect of electron irradiation in FeSCs.

  16. A versatile atomic number correction for electron-probe microanalysis

    International Nuclear Information System (INIS)

    Love, G.; Cox, M.G.; Scott, V.D.

    1978-01-01

    A new atomic number correction is proposed for quantitative electron-probe microanalysis. Analytical expressions for the stopping power S and back-scatter R factors are derived which take into account atomic number of the target, incident electron energy and overvoltage; the latter expression is established using Monte Carlo calculations. The correct procedures for evaluating S and R for multi-element specimens are described. The new method, which overcomes some limitations inherent in earlier atomic number corrections, may readily be used where specimens are inclined to the electron beam. (author)

  17. Constraints on CPT violation from Wilkinson Microwave Anisotropy Probe three year polarization data: A wavelet analysis

    International Nuclear Information System (INIS)

    Cabella, Paolo; Silk, Joseph; Natoli, Paolo

    2007-01-01

    We perform a wavelet analysis of the temperature and polarization maps of the cosmic microwave background (CMB) delivered by the Wilkinson Microwave Anisotropy Probe experiment in search for a parity-violating signal. Such a signal could be seeded by new physics beyond the standard model, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the linear polarization direction of a CMB photon may get rotated during its cosmological journey, a phenomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset of the Wilkinson Microwave Anisotropy Probe and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a nonzero rotation. By using wavelet transforms we set a tighter limit on the CMB photon rotation angle Δα=-2.5±3.0 (Δα=-2.5±6.0) at the one (two) σ level, consistent with a null detection

  18. Polarized Parton Distributions at an Electron-Ion Collider

    CERN Document Server

    Ball, Richard D.; Guffanti, Alberto; Nocera, Emanuele R.; Ridolfi, Giovanni; Rojo, Juan

    2014-01-01

    We study the potential impact of inclusive deep-inelastic scattering data from a future electron-ion collider (EIC) on longitudinally polarized parton distribution (PDFs). We perform a PDF determination using the NNPDF methodology, based on sets of deep-inelastic EIC pseudodata, for different realistic choices of the electron and proton beam energies. We compare the results to our current polarized PDF set, NNPDFpol1.0, based on a fit to fixed-target inclusive DIS data. We show that the uncertainties on the first moments of the polarized quark singlet and gluon distributions are substantially reduced in comparison to NNPDFpol1.0, but also that more measurements may be needed to ultimately pin down the size of the gluon contribution to the nucleon spin.

  19. 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)

  20. Design and performance verification of a wideband scalable dual-polarized probe for spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Kim, Oleksiy S.; Nielsen, Jeppe Majlund

    2012-01-01

    A wideband scalable dual-polarized probe designed by the Electromagnetic Systems group at the Technical University of Denmark is presented. The design was scaled and two probes were manufactured for the frequency bands 1-3 GHz and 0.4-1.2 GHz. The results of the acceptance tests of the 0.4-1.2 GHz...... probe are briefly discussed. Since these probes represent so-called higher-order antennas, applicability of the recently developed higher-order probe correction technique [3] for these probes was investigated. Extensive tests were carried out for two representative antennas under test using...

  1. Role of polarization in probing anomalous gauge interactions of the Higgs boson

    International Nuclear Information System (INIS)

    Biswal, Sudhansu S.; Godbole, Rohini M.; Choudhury, Debajyoti; Mamta

    2009-01-01

    We explore the use of polarized e + /e - beams and/or the information on final state decay lepton polarizations in probing the interaction of the Higgs boson with a pair of vector bosons. A model independent analysis of the process e + e - →ffH, where f is any light fermion, is carried out through the construction of observables having identical properties under the discrete symmetry transformations as different individual anomalous interactions. This allows us to probe an individual anomalous term independent of the others. We find that initial state beam polarization can significantly improve the sensitivity to CP-odd couplings of the Z boson with the Higgs boson (ZZH). Moreover, an ability to isolate events with a particular τ helicity, with even 40% efficiency, can improve sensitivities to certain ZZH couplings by as much as a factor of 3. In addition, the contamination from the ZZH vertex contributions present in the measurement of the trilinear Higgs-W (WWH) couplings can be reduced to a great extent by employing polarized beams. The effects of initial state radiation and beamstrahlung, which can be relevant for higher values of the beam energy are also included in the analysis.

  2. Polarized electron-muon neutrino scattering to electron and neutrino in noncommutative space

    Directory of Open Access Journals (Sweden)

    MM Ettefaghi

    2011-06-01

    Full Text Available For neutrino scattering from polarized electron, the weak interaction term in the cross section is significantly suppressed by the polarized term. The magnetic moment term does not receive any correction from the electron polarization. Hence, the study of the magnetic moment of neutrinos through scattering from the polarized electron leads to a stronger bound on the neutrino magnetic moment compared with the unpolarized case. On the other hand, neutrinos which are electrically neutral can couple directly with photons in Noncommutative (NC QED. In this paper, we calculate the NC QED corrections on this scattering are calculated. The phase difference between the NC term and the polarized weak interaction term is π/2. Therefore, the NC term does not destroy the above suppression.

  3. Chloride ingress profiles measured by electron probe micro analysis

    DEFF Research Database (Denmark)

    Jensen, Ole mejlhede; Coats, Alison M.; Glasser, Fred P.

    1996-01-01

    Traditional techniques for measuring chloride ingress profiles do not apply well to high performance cement paste systems; the geometric resolution of the traditional measuring techniques is too low. In this paper measurements by Electron Probe Micro Analysis (EPMA) are presented. EPMA is demonst......Traditional techniques for measuring chloride ingress profiles do not apply well to high performance cement paste systems; the geometric resolution of the traditional measuring techniques is too low. In this paper measurements by Electron Probe Micro Analysis (EPMA) are presented. EPMA...... is demonstated to determine chloride ingress in cement paste on a micrometer scale. Potential chloride ingress routes such as cracks or the paste-aggregate interface may also be characterized by EPMA. Copyright (C) 1996 Elsevier Science Ltd...

  4. 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

  5. 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.

  6. Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

  7. 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

  8. Optical studies of polarized-electron-noble-gas collisions

    International Nuclear Information System (INIS)

    Gay, T.I.; Furst, J.E.; Geesmann, H.; Khakoo, M.A.; Madison, D.H.; Wijayaratna, W.M.K.P.; Bartschat, K.

    1992-01-01

    We have measured the Stoke's parameters of light emitted following impact excitation of He and Xe by transversely-polarized electrons. For He, the 2 3 S-3 3 P, 389 nm transition was studied in an effort to systematically develop a highly accurate optical electron polarimeter. The 6 3 P 2 -6 3 D 3 , 882 nm transition in Xe was used to assess the importance of spin-dependent forces on the continuum electron for this target. We attempted (and failed) to made the first optical observations of Mott scattering. (Author)

  9. Polarized light scattering as a probe for changes in chromosome structure

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, Daniel Benjamin [Univ. of California, Berkeley, CA (United States)

    1993-10-01

    Measurements and calculations of polarized light scattering are applied to chromosomes. Calculations of the Mueller matrix, which completely describes how the polarization state of light is altered upon scattering, are developed for helical structures related to that of chromosomes. Measurements of the Mueller matrix are presented for octopus sperm heads, and dinoflagellates. Comparisons of theory and experiment are made. A working theory of polarized light scattering from helices is developed. The use of the first Born approximation vs the coupled dipole approximation are investigated. A comparison of continuous, calculated in this work, and discrete models is also discussed. By comparing light scattering measurements with theoretical predictions the average orientation of DNA in an octopus sperm head is determined. Calculations are made for the Mueller matrix of DNA plectonemic helices at UV, visible and X-ray wavelengths. Finally evidence is presented that the chromosomes of dinoflagellates are responsible for observed differential scattering of circularly-polarized light. This differential scattering is found to vary in a manner that is possibly correlated to the cell cycle of the dinoflagellates. It is concluded that by properly choosing the wavelength probe polarized light scattering can provide a useful tool to study chromosome structure.

  10. First results from SLD with polarized electron beam at SLC

    International Nuclear Information System (INIS)

    Fero, M.J.

    1992-12-01

    The SLAC Linear Collider (SLC) has been modified to collide a longitudinally polarized electron beam with the unpolarized positron beam. We review the beginning of polarized beam running at the SLC, and report on the measurement of the left-right cross section asymmetry (A LR ) made with a sample of 10,224 Z decays collected over the course of the 1992 run. The average beam polarization for this set of Z decays was 22.4 ± 0.6%(syst.). A LR was measured to be 0.100 ± 0.044(stat.) ± 0.004(syst.). From this measurement, the weak mixing angle defined at the Z boson pole is determined to be sin 2 θ eff W = 0.2378 ± 0.0056 ± 0.0005

  11. Study of deep inelastic scattering of polarized electrons off polarized deuterons

    International Nuclear Information System (INIS)

    Kuriki, M.

    1996-03-01

    This thesis describes a 29GeV electron - nucleon scattering experiment carried out at Stanford Linear Accelerator Center (SLAC). Highly polarized electrons are scattered off a polarized ND 3 target. Scattered electrons are detected by two spectrometers located in End Station A (ESA) at angles of 4.5 degrees and 7 degrees with respect to the beam axis. We have measured the spin structure function g 1 of deuteron over the range of 0.029 2 2 . This integral indicates a discrepancy of more than three standard deviations from the prediction of the Ellis-Jaffe sum rule, 0.068±0.005 at Q 2 = 3.0(GeV/c) 2 while our result of g 1 d in good agreement with SMC results. Combined with g 1 of the proton, the measurement of ∫ 0 1 (g 1 d -g 1 n ) is 0.169±0.008. We also obtained the strong coupling constant at Q 2 = 3.0(GeV/c) 2 to be 0.417 -0.110 +0.086 , using the power correction for the sum rule up to third order of α s . This result is in agreement with the strong coupling constant α s (Q 2 ) = 3.0(GeV/c 2 ) obtained from various experiments. Using our deuteron results and the axial vector couplings of hyperon decays, the total quark polarization along the nucleon spin is found to be 0.286±.055, implying that quarks carry only 30% of the nucleon spin. The strange sea quark polarization is also determined to be -0.101 ± .023. These measurements are in agreement with other experiments and provide the world's most precise measurement of these quark polarizations. 80 refs., 151 figs., 23 tabs

  12. Electron spin polarization in high-energy storage rings

    International Nuclear Information System (INIS)

    Mane, S.R.

    1987-01-01

    In a high energy storage ring, a single photon emission has relatively little effect on the orbital motion, but it can produce a relatively large change in the electron spin state. Hence the unperturbed orbital motion can be satisfactorily described using classical mechanics, but the spin must be treated quantum mechanically. The electron motion is therefore treated semi-classically in this thesis. It is explained how to diagonalize the unperturbed Hamiltonian to the leading order in Planck's constant. The effects of perturbations are then included, and the relevant time-scales and ensemble averages are elucidated. The Derbenev-Kondratenko formula for the equilibrium degree of polarization is rederived. Mathematical details of the rederivation are given. Since the original authors used a different formalism, a proof is offered of the equivalence between their method and the one used in this thesis. An algorithm is also presented to evaluate the equilibrium polarization. It has a number of new features, which enable the polarization to be calculated to a higher degree of approximation than has hitherto been possible. This facilitates the calculation of so-called spin resonances, which are points at which the polarization almost vanishes. A computer program has been written to implement the above algorithm, in the approximation of linear orbital dynamics, and sample results are presented

  13. Quasi 2D electronic states with high spin-polarization in centrosymmetric MoS2 bulk crystals

    Science.gov (United States)

    Gehlmann, Mathias; Aguilera, Irene; Bihlmayer, Gustav; Młyńczak, Ewa; Eschbach, Markus; Döring, Sven; Gospodarič, Pika; Cramm, Stefan; Kardynał, Beata; Plucinski, Lukasz; Blügel, Stefan; Schneider, Claus M.

    2016-06-01

    Time reversal dictates that nonmagnetic, centrosymmetric crystals cannot be spin-polarized as a whole. However, it has been recently shown that the electronic structure in these crystals can in fact show regions of high spin-polarization, as long as it is probed locally in real and in reciprocal space. In this article we present the first observation of this type of compensated polarization in MoS2 bulk crystals. Using spin- and angle-resolved photoemission spectroscopy (ARPES), we directly observed a spin-polarization of more than 65% for distinct valleys in the electronic band structure. By additionally evaluating the probing depth of our method, we find that these valence band states at the point in the Brillouin zone are close to fully polarized for the individual atomic trilayers of MoS2, which is confirmed by our density functional theory calculations. Furthermore, we show that this spin-layer locking leads to the observation of highly spin-polarized bands in ARPES since these states are almost completely confined within two dimensions. Our findings prove that these highly desired properties of MoS2 can be accessed without thinning it down to the monolayer limit.

  14. Electric Charge Accumulation in Polar and Non-Polar Polymers under Electron Beam Irradiation

    Science.gov (United States)

    Nagasawa, Kenichiro; Honjoh, Masato; Takada, Tatsuo; Miyake, Hiroaki; Tanaka, Yasuhiro

    The electric charge accumulation under an electron beam irradiation (40 keV and 60 keV) was measured by using the pressure wave propagation (PWP) method in the dielectric insulation materials, such as polar polymeric films (polycarbonate (PC), polyethylene-naphthalate (PEN), polyimide (PI), and polyethylene-terephthalate (PET)) and non-polar polymeric films (polystyrene (PS), polypropylene (PP), polyethylene (PE) and polytetrafluoroethylene (PTFE)). The PE and PTFE (non-polar polymers) showed the properties of large amount of electric charge accumulation over 50 C/m3 and long saturation time over 80 minutes. The PP and PS (non-polar polymer) showed the properties of middle amount of charge accumulation about 20 C/m3 and middle saturation time about 1 to 20 minutes. The PC, PEN, PI and PET (polar polymers) showed the properties of small amount of charge accumulation about 5 to 20 C/m3 and within short saturation time about 1.0 minutes. This paper summarizes the relationship between the properties of charge accumulation and chemical structural formula, and compares between the electro static potential distribution with negative charged polymer and its chemical structural formula.

  15. Electric charge accumulation in polar and non-polar polymers under electron beam irradiation

    International Nuclear Information System (INIS)

    Nagasawa, Kenichiro; Honjoh, Masato; Takada, Tatsuo; Miyake, Hiroaki; Tanaka, Yasuhiro

    2010-01-01

    The electric charge accumulation under an electron beam irradiation (40 keV and 60 keV) was measured by using the pressure wave propagation (PWP) method in the dielectric insulation materials, such as polar polymeric films (polycarbonate (PC), polyethylene-naphthalate (PEN), polyimide (PI), and polyethylene-terephthalate (PET)) and non-polar polymeric films (polystyrene (PS), polypropylene (PP), polyethylene (PE) and polytetrafluoroethylene (PTFE)). The PE and PTFE (non-polar polymers) showed the properties of large amount of electric charge accumulation over 50 C/m 3 and long saturation time over 80 minutes. The PP and PS (non-polar polymer) showed the properties of middle amount of charge accumulation about 20 C/m 3 and middle saturation time about 1 to 20 minutes. The PC, PEN, PI and PET (polar polymers) showed the properties of small amount of charge accumulation about 5 to 20 C/m 3 and within short saturation time about 1.0 minutes. This paper summarizes the relationship between the properties of charge accumulation and chemical structural formula, and compares between the electro static potential distribution with negative charged polymer and its chemical structural formula. (author)

  16. Probing spin-polarized tunneling at high bias and temperature with a magnetic tunnel transistor

    NARCIS (Netherlands)

    Park, B.G.; Banerjee, T.; Min, B.C.; Sanderink, Johannes G.M.; Lodder, J.C.; Jansen, R.

    2005-01-01

    The magnetic tunnel transistor (MTT) is a three terminal hybrid device that consists of a tunnel emitter, a ferromagnetic (FM) base, and a semiconductor collector. In the MTT with a FM emitter and a single FM base, spin-polarized hot electrons are injected into the base by tunneling. After

  17. Polarized electrons and the origin of optical activity

    International Nuclear Information System (INIS)

    Bonner, W.A.; Dort, M.A. Van; Yearian, M.R.; Zeman, H.D.; Li, G.C.; Stanford Univ., Calif.

    1976-01-01

    The history of experiments bearing on the origin of optical acitivity in nature by parity non-conservation during the β-decay of radioactive isotopes is briefly reviewed. Following this, we present a more detailed description of our recent published and unpublished data and calculations regarding the generation of optical activity in DL-leucine by means of artificially produced longitudinally polarized electrons from a linear accelerator

  18. Parity nonconservation in polarized electron scattering at high energies

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1979-10-01

    Recent observations of parity violation in inelastic scattering of electrons at high energy is discussed with reference to the process e(polarized) + D(unpolarized) → e + X. The kinetics of this process, the idealized case of scattering from free quark targets, experimental techniques and results, and relations to atomic physics of parity violation in bismuth and thallium atoms with a model independent analysis. 17 references

  19. Polarization Measurements in elastic electron-deuteron scattering

    International Nuclear Information System (INIS)

    Garcon, M.

    1989-01-01

    The deuteron electromagnetic form factors, are recalled. The experiment, recently performed in the Bates accelerator (M.I.T.), is described. The aim of the experiment is the measurement of the tensor polarization of the backscattered deuteron, in the elastic electron-deuteron scattering, up to q = 4.6 f/m. Different experimental methods, concerning the determination of this observable, are compared. Several improvement possibilities in this field are suggested

  20. THE ELECTRON ION COLLIDER. A HIGH LUMINOSITY PROBE OF THE PARTONIC SUBSTRUCTURE OF NUCLEONS AND NUCLEI.

    Energy Technology Data Exchange (ETDEWEB)

    EDITED BY M.S. DAVIS

    2002-02-01

    By the end of this decade, the advancement of current and planned research into the fundamental structure of matter will require a new facility, the Electron Ion Collider (EIC). The EIC will collide high-energy beams of polarized electrons from polarized protons and neutrons, and unpolarized beams of electrons off atomic nuclei with unprecedented intensity. Research at the EIC will lead to a detailed understanding of the structure of the proton, neutron, and atomic nuclei as described by Quantum Chromo-Dynamics (QCD), the accepted theory of the strong interaction. The EIC will establish quantitative answers to important questions by delivering dramatically increased precision over existing and planned experiments and by providing completely new experimental capabilities. Indeed, the EIC will probe QCD in a manner not possible previously. This document presents the scientific case for the design, construction and operation of the EIC. While realization of the EIC requires a significant advance in the development of efficient means of producing powerful beams of energetic electrons, an important consideration for choosing the site of the EIC is the planned upgrade to the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The upgrade planned for RHIC will fully meet the requirements for the ion beam for the EIC, providing a distinct advantage in terms of cost, schedule and the final operation.

  1. Polarization entanglement of sum-frequency photons: A tool to probe the Markovian limit

    Science.gov (United States)

    Volkov, Victor; Chelli, Riccardo

    2015-06-01

    The article addresses the possibility of entanglement-specific infrared-visible sum-frequency generation spectroscopy. In the case of an anisotropic interface, it is possible to employ SSS and PSS polarizations to detect responses not only specific to χY Y Y and χX Y Y nonlinearities, but also to higher-order χ(Y Y Y )(X Y Y ) and χ(X Y Y )(Y Y Y ) nonlinearities. Using quantum mechanical studies of the rhenium complex [Re (OH) 3(CO) 3] as a molecular model, we demonstrate that if such complexes would form an anisotropic orientational distribution at a surface, under the considered geometry and the polarization settings, we may prepare quantum correlated C =O vibrational states to emit polarization-entangled photons. Accordingly, we explore the possibility of a polarization-measurement protocol to extract spectral signatures of the entangled states. The response would be informative on intramolecular interactions. As a result, we discuss the possible practical implications in probing dynamics at interfaces, and different opportunities in the preparation of entangled vibrational states of quantified fidelity.

  2. Sparse sampling and reconstruction for electron and scanning probe microscope imaging

    Science.gov (United States)

    Anderson, Hyrum; Helms, Jovana; Wheeler, Jason W.; Larson, Kurt W.; Rohrer, Brandon R.

    2015-07-28

    Systems and methods for conducting electron or scanning probe microscopy are provided herein. In a general embodiment, the systems and methods for conducting electron or scanning probe microscopy with an undersampled data set include: driving an electron beam or probe to scan across a sample and visit a subset of pixel locations of the sample that are randomly or pseudo-randomly designated; determining actual pixel locations on the sample that are visited by the electron beam or probe; and processing data collected by detectors from the visits of the electron beam or probe at the actual pixel locations and recovering a reconstructed image of the sample.

  3. Quantification of multielement-multilayer-samples in electron probe analysis

    International Nuclear Information System (INIS)

    Pfeiffer, A.

    1995-03-01

    The following dissertation presents the theoretical basis of analytical correction models and Monte Carlo simulations in the field of electron probe microanalysis to describe the excitation conditions of x-rays in a multilayer-multielement-sample. In this connection analyzing programs have been developed to make a quantitative investigation of heterogeneous samples possible. In the work the mathematical methods and formulas, which are mainly based on empirical and semiempirical findings, are described and their validity is discussed in detail. Especially the improvements of the 'multiple reflections'-model by August are compared with the Φ(ρz)-models by Pouchou, Merlet and Bastin. The calculations of depth distribution functions for characteristics and continuous fluorescence excitation result in a consistent and completeΦ(ρz)-model. This allows to analyze layered structures in great detail. Because of the increasing importance in electron probe microanalysis and as a reference method a Monte Carlo model is described. With this model electron trajectories and excitation conditions in arbitrary two dimensional geometries can be calculated. The validity of the analytical model is proven with a comprehensive comparison of results of new calculations to published data. To show an application of the programs and models in routine use in the industrial research and development, a quantitative analysis of a Co/Si system is made. In the conclusion of this dissertation some reflections upon investigations, which are based on this work and which should be made in future are outlined. (author)

  4. Spin polarized electron source technology transferred from HE accelerators to electron microscopes

    International Nuclear Information System (INIS)

    Nakanishi, Tsutomu

    2009-01-01

    For many years, we have developed a technology of spin-polarized-electron-source (PES) for a future linear collider project (ILC). Various new techniques for achieving high polarization, high quantum efficiency, high current density, sub-nanosecond multi-bunch generation etc. were developed. Two fundamental technologies; reduction of dark current and preparation of extremely high vacuum environment to protect the Negative Electron Affinity (NEA) surface have been also developed. Using these PES technologies and a new transmission type photocathode, we recently succeeded in producing the high brightness and high polarization electron beam for the low energy electron microscope (LEEM). Our Spin-LEEM system enables the world-first dynamic observation of surface magnetic domain formed by evaporation on the metal substrate with ∼ 20 nm space resolutions. (author)

  5. Probing Nanoscale Electronic and Magnetic Interaction with Scanning Tunneling Spectroscopy

    DEFF Research Database (Denmark)

    Bork, Jakob

    tunneling microscope (STM). Especially at low temperatures the Kondo resonance is used to probe magnetic interaction with ferromagnetic islands and between two atoms. The latter showing a crossover between Kondo screened atoms and antiferromagnetically coupled atoms close to the quantum critical point....... This is related to research in correlated electron materials such as studies of phase transitions in heavy fermion compounds and magnetic interaction in spintronic research. The capping of cobalt islands on Cu(111) with silver is investigated with STM and photoemission spectroscopy. It is shown that at low...

  6. Characteristics of short distance field of a source radiating at electronic frequencies in a ionospheric plasma. Applications to density and electron temperature measurement by mutual impedance probe

    International Nuclear Information System (INIS)

    Debrie, R.

    1983-06-01

    Realization of a new type of radio-frequency probe, the mutual-impedance probe (or the quadrupole probe) is developed. Theoretical results obtained with a cold plasma description of the ionized medium with static magnetic field. Transfer impedance between two dipoles in an homogeneous hot and isotope plasma is then calculated. In equatorial ionosphere, measurements made by the H.F. quadrupole probe, in the Veronique rocket, during the Cisaspe experiment, have been interpreted with this hot plasma theory. The influence of a plasma drift with respect to the emitter dipole is analyzed. The influence of a static magnetic field in hot and homogeneous plasma, on the frequency response curve of the mutual impedance is studied. For, in ionospheric plasmas of auroral and polar zones, the earth magnetic field is no more negligible and gives to the plasma dielectric, strongly anisotropic, properties well described by the microscopic theory in hot magnetoplasma. The space time fast evolution of characteristics of plasma encountered in space experiments has been shown up with a new method of measurement the self-oscillating quadrupole probe. The work synthesis is put in a concrete form on the polar satellite Aureol-3 the first results of which are presented. This satellite allows a precise study of ionosphere auroral zones. At last, it is shown that methods developed for electron density and temperature measurements can be transposed in low frequency. In this case, measurements with quadrupole probe allow to get the ion average mass by lower hybrid frequency excitation [fr

  7. Electron-Spin Filters Would Offer Spin Polarization Greater than 1

    Science.gov (United States)

    Ting, David Z.

    2009-01-01

    A proposal has been made to develop devices that would generate spin-polarized electron currents characterized by polarization ratios having magnitudes in excess of 1. Heretofore, such devices (denoted, variously, as spin injectors, spin polarizers, and spin filters) have typically offered polarization ratios having magnitudes in the approximate range of 0.01 to 0.1. The proposed devices could be useful as efficient sources of spin-polarized electron currents for research on spintronics and development of practical spintronic devices.

  8. Optimization of Actinide Quantification by Electron Probe Microanalysis

    International Nuclear Information System (INIS)

    Moy, A.; Merlet, C.; Llovet, X.; Dugne, O.

    2013-06-01

    Conventional quantitative electron probe microanalysis of actinides requires the use of reference standard samples. However, for such elements, standards are generally not available. To overcome this difficulty, standard-less methods of analysis are used, in which the x-ray intensity emitted by the standard is calculated. To be reliable, such calculations require accurate knowledge of physical data such as the x-ray production cross section. However, experimental data of this quantity are not always available for actinide elements. In the present work, experimental L and M x-ray production cross sections were measured for elements uranium and lead. Measurements were performed with two electron microprobes using wavelength-dispersive spectrometers using thin self-supporting targets. Experimental results are compared with calculated cross sections obtained from different analytical formulae, and, whenever possible, with experimental data obtained from the literature. (authors)

  9. Electron correlations in narrow energy bands: modified polar model approach

    Directory of Open Access Journals (Sweden)

    L. Didukh

    2008-09-01

    Full Text Available The electron correlations in narrow energy bands are examined within the framework of the modified form of polar model. This model permits to analyze the effect of strong Coulomb correlation, inter-atomic exchange and correlated hopping of electrons and explain some peculiarities of the properties of narrow-band materials, namely the metal-insulator transition with an increase of temperature, nonlinear concentration dependence of Curie temperature and peculiarities of transport properties of electronic subsystem. Using a variant of generalized Hartree-Fock approximation, the single-electron Green's function and quasi-particle energy spectrum of the model are calculated. Metal-insulator transition with the change of temperature is investigated in a system with correlated hopping. Processes of ferromagnetic ordering stabilization in the system with various forms of electronic DOS are studied. The static conductivity and effective spin-dependent masses of current carriers are calculated as a function of electron concentration at various DOS forms. The correlated hopping is shown to cause the electron-hole asymmetry of transport and ferromagnetic properties of narrow band materials.

  10. On some methods to produce high-energy polarized electron beams by means of proton synchrotrons

    International Nuclear Information System (INIS)

    Bessonov, E.G.; Vazdik, Ya.A.

    1980-01-01

    Some methods of production of high-energy polarized electron beams by means of proton synchrotrons are considered. These methods are based on transfer by protons of a part of their energy to the polarized electrons of a thin target placed inside the working volume of the synchrotron. It is suggested to use as a polarized electron target a magnetized crystalline iron in which proton channeling is realized, polarized atomic beams and the polarized plasma. It is shown that by this method one can produce polarized electron beams with energy approximately 100 GeV, energy spread +- 5 % and intensity approximately 10 7 electron/c, polarization approximately 30% and with intensity approximately 10 4 -10 5 electron/c, polarization approximately 100% [ru

  11. Electron probe analysis of biological fluids: Possibilities and limitations

    International Nuclear Information System (INIS)

    Roinel, N.

    1984-01-01

    Physical methods of investigation have become essential to investigations at the cellular or subcellular level. Nuclear magnetic resonance is the most recent and striking example, since it is not only a tool for fundamental physicists and organic chemists, but also an extraordinary powerful imaging tool for physicians. The absorption properties of X rays were used immediately after their discovery to image the bones of skeletons. Later, X rays were also found to be extremely efficient in the measurement of the elemental content of microvolumes irradiated by electron probes. The electron probe analyzer (EPA) was immediately adopted by numerous laboratories of metallurgy, geology, and mineral sciences. In the last fifteen years, since the use of this instrument was suggested for liquid analysis, and a preparative technique was developed, the EPA has been used by an increasing number of biological laboratories for measuring the concentrations of the elements contained in subnanoliter volumes of biological fluids. The so-called microdroplet technique has become a routine laboratory method, the only one able to measure the concentrations of an unlimited number of elements in a single 0.1-nl sample. This explains its use in fields as various as renal, reproductive, digestive, and plant physiology, zoology, etc. Several review papers discuss these applications. The possibilities and limitations of the technique are discussed below

  12. Standardless quantification by parameter optimization in electron probe microanalysis

    International Nuclear Information System (INIS)

    Limandri, Silvina P.; Bonetto, Rita D.; Josa, Víctor Galván; Carreras, Alejo C.; Trincavelli, Jorge C.

    2012-01-01

    A method for standardless quantification by parameter optimization in electron probe microanalysis is presented. The method consists in minimizing the quadratic differences between an experimental spectrum and an analytical function proposed to describe it, by optimizing the parameters involved in the analytical prediction. This algorithm, implemented in the software POEMA (Parameter Optimization in Electron Probe Microanalysis), allows the determination of the elemental concentrations, along with their uncertainties. The method was tested in a set of 159 elemental constituents corresponding to 36 spectra of standards (mostly minerals) that include trace elements. The results were compared with those obtained with the commercial software GENESIS Spectrum® for standardless quantification. The quantifications performed with the method proposed here are better in the 74% of the cases studied. In addition, the performance of the method proposed is compared with the first principles standardless analysis procedure DTSA for a different data set, which excludes trace elements. The relative deviations with respect to the nominal concentrations are lower than 0.04, 0.08 and 0.35 for the 66% of the cases for POEMA, GENESIS and DTSA, respectively. - Highlights: ► A method for standardless quantification in EPMA is presented. ► It gives better results than the commercial software GENESIS Spectrum. ► It gives better results than the software DTSA. ► It allows the determination of the conductive coating thickness. ► It gives an estimation for the concentration uncertainties.

  13. Large acceptance magnetic spectrometers for polarized deep inelastic electron scattering

    International Nuclear Information System (INIS)

    Petratos, G.G.; Eisele, R.L.; Gearhart, R.A.; Hughes, E.W.; Young, C.C.

    1991-10-01

    The design of two magnetic spectrometers for the measurement of the spin-dependent structure function g 1 n of the neutron and a test of the Bjorken sum rule is described. The measurement will consist of scattering 23 GeV polarized electrons off a polarized 3 He target and detecting scattered electrons of 7 to 18 GeV at 4.5 degree and 7 degree. Each spectrometer is based on two large aperture dipole magnets bending in opposite directions. This ''reverse'' deflection design doubles the solid angle as compared to the conventional design of same direction bends used in previous experiments. Proper choice of the deflection angles and the distance between the two dipoles in each spectrometer allows background photons from radiative processes to reach the detectors only after at least two bounces off the spectrometer vacuum walls, resulting in an expected tolerable background. Each spectrometer is equipped with a pair of Cerenkov detectors, a pair of scintillation hodoscopes and a lead-glass shower calorimeter providing electron and pion identification with angular and momentum resolutions sufficient for the experimental measurement. 7 refs., 8 figs., 1 tab

  14. Exciton versus Free Carrier Photogeneration in Organometal Trihalide Perovskites Probed by Broadband Ultrafast Polarization Memory Dynamics

    Science.gov (United States)

    Sheng, ChuanXiang; Zhang, Chuang; Zhai, Yaxin; Mielczarek, Kamil; Wang, Weiwei; Ma, Wanli; Zakhidov, Anvar; Vardeny, Z. Valy

    2015-03-01

    We studied the ultrafast transient response of photoexcitations in two hybrid organic-inorganic perovskite films used for high efficiency photovoltaic cells, namely, CH3NH3PbI3 and CH3NH3PbI1.1Br1.9 using polarized broadband pump-probe spectroscopy in the spectral range of 0.3-2.7 eV with 300 fs time resolution. For CH3NH3PbI3 with above-gap excitation we found both photogenerated carriers and excitons, but only carriers are photogenerated with below-gap excitation. In contrast, mainly excitons are photogenerated in CH3NH3PbI1.1Br1.9 . Surprisingly, we also discovered in CH3NH3PbI3 , but not in CH3NH3PbI1.1Br1.9 , transient photoinduced polarization memory for both excitons and photocarriers, which is also reflected in the steady state photoluminescence. From the polarization memory dynamics we obtained the excitons diffusion constant in CH3NH3PbI3 , D ≈0.01 cm2 s-1 .

  15. ProbeZT: Simulation of transport coefficients of molecular electronic junctions under environmental effects using Büttiker's probes

    Science.gov (United States)

    Korol, Roman; Kilgour, Michael; Segal, Dvira

    2018-03-01

    We present our in-house quantum transport package, ProbeZT. This program provides linear response coefficients: electrical and electronic thermal conductances, as well as the thermopower of molecular junctions in which electrons interact with the surrounding thermal environment. Calculations are performed based on the Büttiker probe method, which introduces decoherence, energy exchange and dissipation effects phenomenologically using virtual electrode terminals called probes. The program can realize different types of probes, each introducing various environmental effects, including elastic and inelastic scattering of electrons. The molecular system is described by an arbitrary tight-binding Hamiltonian, allowing the study of different geometries beyond simple one-dimensional wires. Applications of the program to study the thermoelectric performance of molecular junctions are illustrated. The program also has a built-in functionality to simulate electron transport in double-stranded DNA molecules based on a tight-binding (ladder) description of the junction.

  16. DVCS in the fragmentation region of polarized electron

    International Nuclear Information System (INIS)

    Akushevich, I.; Kuraev, E.A.; Nikolaev, N.N.

    2000-01-01

    For the kinematical region when a hard photon is emitted predominantly close to the direction of motion of a longitudinally polarized initial electron and relatively small momentum transfer to a proton we calculate the azimuthal asymmetry of a photon emission. It arises from the interference of the Bethe-Heitler amplitude and those which are described by a heavy photon impact factor. The azimuthal asymmetry does not decrease in the limit of infinite cms energy. The lowest order expression for the impact factor of a heavy photon is presented

  17. Measurement of Deuteron Tensor Polarization in Elastic Electron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Gustafsson, Kenneth K. [Univ. of Maryland, College Park, MD (United States)

    2000-01-01

    Nuclear physics traces it roots back to the very beginning of the last century. The concept of the nuclear atom was introduced by Rutherford around 1910. The discovery of the neutron Chadwick in 1932 gave us the concept of two nucleons: the proton and the neutron. The Jlab electron accelerator with its intermediate energy high current continuous wave beam combined with the Hall C high resolution electron spectrometer and a deutron recoil polarimeter provided experiment E94018 with the opportunity to study the deuteron electomagnetic structure, in particular to measure the tensor polarization observable t20, at high four momentum transfers than ever before. This dissertation presents results of JLab experiment E94018.

  18. Standardless quantification by parameter optimization in electron probe microanalysis

    Energy Technology Data Exchange (ETDEWEB)

    Limandri, Silvina P. [Instituto de Fisica Enrique Gaviola (IFEG), CONICET (Argentina); Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Medina Allende s/n, (5016) Cordoba (Argentina); Bonetto, Rita D. [Centro de Investigacion y Desarrollo en Ciencias Aplicadas Dr. Jorge Ronco (CINDECA), CONICET, 47 Street 257, (1900) La Plata (Argentina); Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1 and 47 Streets (1900) La Plata (Argentina); Josa, Victor Galvan; Carreras, Alejo C. [Instituto de Fisica Enrique Gaviola (IFEG), CONICET (Argentina); Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Medina Allende s/n, (5016) Cordoba (Argentina); Trincavelli, Jorge C., E-mail: trincavelli@famaf.unc.edu.ar [Instituto de Fisica Enrique Gaviola (IFEG), CONICET (Argentina); Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Medina Allende s/n, (5016) Cordoba (Argentina)

    2012-11-15

    A method for standardless quantification by parameter optimization in electron probe microanalysis is presented. The method consists in minimizing the quadratic differences between an experimental spectrum and an analytical function proposed to describe it, by optimizing the parameters involved in the analytical prediction. This algorithm, implemented in the software POEMA (Parameter Optimization in Electron Probe Microanalysis), allows the determination of the elemental concentrations, along with their uncertainties. The method was tested in a set of 159 elemental constituents corresponding to 36 spectra of standards (mostly minerals) that include trace elements. The results were compared with those obtained with the commercial software GENESIS Spectrum Registered-Sign for standardless quantification. The quantifications performed with the method proposed here are better in the 74% of the cases studied. In addition, the performance of the method proposed is compared with the first principles standardless analysis procedure DTSA for a different data set, which excludes trace elements. The relative deviations with respect to the nominal concentrations are lower than 0.04, 0.08 and 0.35 for the 66% of the cases for POEMA, GENESIS and DTSA, respectively. - Highlights: Black-Right-Pointing-Pointer A method for standardless quantification in EPMA is presented. Black-Right-Pointing-Pointer It gives better results than the commercial software GENESIS Spectrum. Black-Right-Pointing-Pointer It gives better results than the software DTSA. Black-Right-Pointing-Pointer It allows the determination of the conductive coating thickness. Black-Right-Pointing-Pointer It gives an estimation for the concentration uncertainties.

  19. Subauroral Polarization Streams (SAPS) Duration as Determined From Van Allen Probe Successive Electric Drift Measurements

    Science.gov (United States)

    Lejosne, Solène; Mozer, F. S.

    2017-09-01

    We examine a characteristic feature of the magnetosphere-ionosphere coupling, namely, the persistent and latitudinally narrow bands of rapid westward ion drifts called the subauroral polarization streams (SAPS). Despite countless works on SAPS, information relative to their durations is lacking. Here we report on the first statistical analysis of more than 200 near-equatorial SAPS observations based on more than 2 years of Van Allen Probe electric drift measurements. First, we present results relative to SAPS radial locations and amplitudes. Then, we introduce two different ways to estimate SAPS durations. In both cases, SAPS activity is estimated to last for about 9 h on average. However, our estimates for SAPS duration are limited either by the relatively long orbital periods of the spacecraft or by the relatively small number of observations involved. Fifty percent of the events fit within the time interval [0;18] hours.

  20. On the over-collection of electrons by high voltage probes in space

    International Nuclear Information System (INIS)

    Cooke, D.L.; Katz, I.; Jongeward, G.; Mandell, M.

    1988-01-01

    It has been two decades since Parker and Murphy proposed a theory to place a rigorous upper bound on the current to an electron collecting probe in space, due to the influence of the geomagnetic field. Any greater current is then thought to involve some form of anomalous cross field transport to explain over-collection. Over-collection is commonly observed and is usually explained by invoking turbulence as a source of collisions. Although the turbulence hypothesis has some theoretical basis, no compelling kinetic theory or model has been put forth. Another possible explanation for over-collection is the ionization of the neutral gas within the charge sheath. Recently, in support of the SPEAR I rocket experiment, the three dimensional code POLAR has been used to model electron collection in a low earth orbit plasma. SPEAR I was a sounding rocket experiment that exposed to the space plasma, a pair of 10cm spherical probes biased to 44kV positive. The POLAR runs included single sphere, two sphere, and two sphere plus rocket modes. The single sphere model did not predict collection in excess of the Parker-Murphy limit. Models of two sphere collection, and of the entire experiment do however show that increased collection is possible as a result of asymetries introduced by geometry and a negative rocket body potential. These models were in close agreement with the experiment. In addition to the symmetry factor, sheath ionization is reviewed. A discussion of the role and kinetic nature of collisionless turbulence is presented

  1. Electric field measurements on Cluster: comparing the double-probe and electron drift techniques

    Directory of Open Access Journals (Sweden)

    A. I. Eriksson

    2006-03-01

    Full Text Available The four Cluster satellites each carry two instruments designed for measuring the electric field: a double-probe instrument (EFW and an electron drift instrument (EDI. We compare data from the two instruments in a representative sample of plasma regions. The complementary merits and weaknesses of the two techniques are illustrated. EDI operations are confined to regions of magnetic fields above 30 nT and where wave activity and keV electron fluxes are not too high, while EFW can provide data everywhere, and can go far higher in sampling frequency than EDI. On the other hand, the EDI technique is immune to variations in the low energy plasma, while EFW sometimes detects significant nongeophysical electric fields, particularly in regions with drifting plasma, with ion energy (in eV below the spacecraft potential (in volts. We show that the polar cap is a particularly intricate region for the double-probe technique, where large nongeophysical fields regularly contaminate EFW measurments of the DC electric field. We present a model explaining this in terms of enhanced cold plasma wake effects appearing when the ion flow energy is higher than the thermal energy but below the spacecraft potential multiplied by the ion charge. We suggest that these conditions, which are typical of the polar wind and occur sporadically in other regions containing a significant low energy ion population, cause a large cold plasma wake behind the spacecraft, resulting in spurious electric fields in EFW data. This interpretation is supported by an analysis of the direction of the spurious electric field, and by showing that use of active potential control alleviates the situation.

  2. Sample Preparation for Electron Probe Microanalysis—Pushing the Limits

    Science.gov (United States)

    Geller, Joseph D.; Engle, Paul D.

    2002-01-01

    There are two fundamental considerations in preparing samples for electron probe microanalysis (EPMA). The first one may seem obvious, but we often find it is overlooked. That is, the sample analyzed should be representative of the population from which it comes. The second is a direct result of the assumptions in the calculations used to convert x-ray intensity ratios, between the sample and standard, to concentrations. Samples originate from a wide range of sources. During their journey to being excited under the electron beam for the production of x rays there are many possibilities for sample alteration. Handling can contaminate samples by adding extraneous matter. In preparation, the various abrasives used in sizing the sample by sawing, grinding and polishing can embed themselves. The most accurate composition of a contaminated sample is, at best, not representative of the original sample; it is misleading. Our laboratory performs EPMA analysis on customer submitted samples and prepares over 250 different calibration standards including pure elements, compounds, alloys, glasses and minerals. This large variety of samples does not lend itself to mass production techniques, including automatic polishing. Our manual preparation techniques are designed individually for each sample. The use of automated preparation equipment does not lend itself to this environment, and is not included in this manuscript. The final step in quantitative electron probe microanalysis is the conversion of x-ray intensities ratios, known as the “k-ratios,” to composition (in mass fraction or atomic percent) and/or film thickness. Of the many assumptions made in the ZAF (where these letters stand for atomic number, absorption and fluorescence) corrections the localized geometry between the sample and electron beam, or takeoff angle, must be accurately known. Small angular errors can lead to significant errors in the final results. The sample preparation technique then becomes very

  3. Sample Preparation for Electron Probe Microanalysis-Pushing the Limits.

    Science.gov (United States)

    Geller, Joseph D; Engle, Paul D

    2002-01-01

    There are two fundamental considerations in preparing samples for electron probe microanalysis (EPMA). The first one may seem obvious, but we often find it is overlooked. That is, the sample analyzed should be representative of the population from which it comes. The second is a direct result of the assumptions in the calculations used to convert x-ray intensity ratios, between the sample and standard, to concentrations. Samples originate from a wide range of sources. During their journey to being excited under the electron beam for the production of x rays there are many possibilities for sample alteration. Handling can contaminate samples by adding extraneous matter. In preparation, the various abrasives used in sizing the sample by sawing, grinding and polishing can embed themselves. The most accurate composition of a contaminated sample is, at best, not representative of the original sample; it is misleading. Our laboratory performs EPMA analysis on customer submitted samples and prepares over 250 different calibration standards including pure elements, compounds, alloys, glasses and minerals. This large variety of samples does not lend itself to mass production techniques, including automatic polishing. Our manual preparation techniques are designed individually for each sample. The use of automated preparation equipment does not lend itself to this environment, and is not included in this manuscript. The final step in quantitative electron probe microanalysis is the conversion of x-ray intensities ratios, known as the "k-ratios," to composition (in mass fraction or atomic percent) and/or film thickness. Of the many assumptions made in the ZAF (where these letters stand for atomic number, absorption and fluorescence) corrections the localized geometry between the sample and electron beam, or takeoff angle, must be accurately known. Small angular errors can lead to significant errors in the final results. The sample preparation technique then becomes very

  4. Probing Intermolecular Electron Delocalization in Dimer Radical Anions by Vibrational Spectroscopy

    International Nuclear Information System (INIS)

    Mani, Tomoyasu; Brookhaven National Laboratory; Grills, David C.

    2017-01-01

    Delocalization of charges is one of the factors controlling charge transport in conjugated molecules. It is considered to play an important role in the performance of a wide range of molecular technologies, including organic solar cells and organic electronics. Dimerization reactions are well-suited as a model to investigate intermolecular spatial delocalization of charges. And while dimerization reactions of radical cations are well investigated, studies on radical anions are still scarce. Upon dimerization of radical anions with neutral counterparts, an electron is considered to delocalize over the two molecules. By using time-resolved infrared (TRIR) detection coupled with pulse radiolysis, we show that radical anions of 4-n-hexyl-4'-cyanobiphenyl (6CB) undergo such dimerization reactions, with an electron equally delocalized over the two molecules. We have recently demonstrated that nitrile ν(C≡N) vibrations respond to the degree of electron localization of nitrile-substituted anions: we can quantify the changes in the electronic charges from the neutral to the anion states in the nitriles by monitoring the ν(C≡N) IR shifts. In the first part of this article, we show that the sensitivity of the ν(C≡N) IR shifts does not depend on solvent polarity. In the second part, we describe how probing the shifts of the nitrile IR vibrational band unambiguously confirms the formation of dimer radical anions, with K dim = 3 × 10 4 M –1 . IR findings are corroborated by electronic absorption spectroscopy and electronic structure calculations. We find that the presence of a hexyl chain and the formation of π–π interactions are both crucial for dimerization of radical anions of 6CB with neutral 6CB. Our study provides clear evidence of spatial delocalization of electrons over two molecular fragments.

  5. Electron ionization and spin polarization control of Fe atom adsorbed graphene irradiated by a femtosecond laser

    International Nuclear Information System (INIS)

    Yu, Dong; Jiang, Lan; Wang, Feng; Li, Xin; Qu, Liangti; Lu, Yongfeng

    2015-01-01

    We investigate the structural properties and ionized spin electrons of an Fe–graphene system, in which the time-dependent density functional theory (TDDFT) within the generalized gradient approximation is used. The electron dynamics, including electron ionization and ionized electron spin polarization, is described for Fe atom adsorbed graphene under femtosecond laser irradiation. The theoretical results show that the electron ionization and ionized electron spin polarization are sensitive to the laser parameters, such as the incident angle and the peak intensity. The spin polarization presents the maximum value under certain laser parameters, which may be used as a source of spin-polarized electrons. - Highlights: • The structural properties of Fe–graphene system are investigated. • The electron dynamics of Fe–graphene system under laser irradiation are described. • The Fe–graphene system may be used as a source of spin-polarized electrons

  6. Frequency-agile gyrotron for electron decoupling and pulsed dynamic nuclear polarization

    Science.gov (United States)

    Scott, Faith J.; Saliba, Edward P.; Albert, Brice J.; Alaniva, Nicholas; Sesti, Erika L.; Gao, Chukun; Golota, Natalie C.; Choi, Eric J.; Jagtap, Anil P.; Wittmann, Johannes J.; Eckardt, Michael; Harneit, Wolfgang; Corzilius, Björn; Th. Sigurdsson, Snorri; Barnes, Alexander B.

    2018-04-01

    We describe a frequency-agile gyrotron which can generate frequency-chirped microwave pulses. An arbitrary waveform generator (AWG) within the NMR spectrometer controls the microwave frequency, enabling synchronized pulsed control of both electron and nuclear spins. We demonstrate that the acceleration of emitted electrons, and thus the microwave frequency, can be quickly changed by varying the anode voltage. This strategy results in much faster frequency response than can be achieved by changing the potential of the electron emitter, and does not require a custom triode electron gun. The gyrotron frequency can be swept with a rate of 20 MHz/μs over a 670 MHz bandwidth in a static magnetic field. We have already implemented time-domain electron decoupling with dynamic nuclear polarization (DNP) magic angle spinning (MAS) with this device. In this contribution, we show frequency-swept DNP enhancement profiles recorded without changing the NMR magnet or probe. The profile of endofullerenes exhibits a DNP profile with a <10 MHz linewidth, indicating that the device also has sufficient frequency stability, and therefore phase stability, to implement pulsed DNP mechanisms such as the frequency-swept solid effect. We describe schematics of the mechanical and vacuum construction of the device which includes a novel flanged sapphire window assembly. Finally, we discuss how commercially available continuous-wave gyrotrons can potentially be converted into similar frequency-agile high-power microwave sources.

  7. Electron emission in the Auger neutralization of a spin-polarized He+ ion embedded in a free electron gas

    International Nuclear Information System (INIS)

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

    2005-01-01

    Results are presented for the energy distribution and spin polarization of the electrons excited during the Auger neutralization of a spin polarized He + ion embedded in a paramagnetic free electron gas. The screening of the He + ion is calculated using density functional theory within the local spin density approximation. The Auger rates, the energy distribution and the spin polarization of the excited electrons are obtained using the Fermi golden rule. The transport of the electrons is calculated within the Boltzmann transport equation formalism. The spin-polarization of the initially excited electrons is very high (>70%) and parallel to that of the electron bound to the He + ion. Nevertheless, the emitted electrons show a much lower degree of polarization, mainly in the low energy range, due to the creation of the unpolarized cascade of secondaries in the transport process

  8. Study of the Polarization Strategy for Electron Cyclotron Heating Systems on HL-2M

    Science.gov (United States)

    Zhang, F.; Huang, M.; Xia, D. H.; Song, S. D.; Wang, J. Q.; Huang, B.; Wang, H.

    2016-06-01

    As important components integrated in transmission lines of electron cyclotron heating systems, polarizers are mainly used to obtain the desired polarization for highly efficient coupling between electron cyclotron waves and plasma. The polarization strategy for 105-GHz electron cyclotron heating systems of HL-2M tokamak is studied in this paper. Considering the polarizers need high efficiency, stability, and low loss to realize any polarization states, two sinusoidal-grooved polarizers, which include a linear polarizer and an elliptical polarizer, are designed with the coordinate transformation method. The parameters, the period p and the depth d, of two sinusoidal-grooved polarizers are optimized by a phase difference analysis method to achieve an almost arbitrary polarization. Finally, the optimized polarizers are manufactured and their polarization characteristics are tested with a low-power test platform. The experimental results agree well with the numerical calculations, indicating that the designed polarizers can meet the polarization requirements of the electron cyclotron heating systems of HL-2M tokamak.

  9. Weak magnetism of Aurivillius-type multiferroic thin films probed by polarized neutron reflectivity

    Science.gov (United States)

    Zhai, Xiaofang; Grutter, Alexander J.; Yun, Yu; Cui, Zhangzhang; Lu, Yalin

    2018-04-01

    Unambiguous magnetic characterization of room-temperature multiferroic materials remains challenging due in part to the difficulty of distinguishing their very weak ferromagnetism from magnetic impurity phases and other contaminants. In this study, we used polarized neutron reflectivity to probe the magnetization of B i6FeCoT i3O18 and LaB i5FeCoT i3O18 in their epitaxial thin films while eliminating a variety of impurity contributions. Our results show that LaB i5FeCoT i3O18 exhibits a magnetization of about 0.016 ±0.027 μB/Fe -Co pair at room temperature, while the B i6FeCoT i3O18 thin film only exhibits a weak magnetic moment below room temperature, with a saturation magnetization of 0.049 ±0.015 μB/Fe -Co pair at 50 K. This polarized-neutron-reflectivity study places an upper magnetization limit on the matrix material of the magnetically doped Aurivillius oxides and helps to clarify the true mechanism behind the room-temperature magnetic performance.

  10. A Molecular Probe for the Detection of Polar Lipids in Live Cells.

    Science.gov (United States)

    Bader, Christie A; Shandala, Tetyana; Carter, Elizabeth A; Ivask, Angela; Guinan, Taryn; Hickey, Shane M; Werrett, Melissa V; Wright, Phillip J; Simpson, Peter V; Stagni, Stefano; Voelcker, Nicolas H; Lay, Peter A; Massi, Massimiliano; Plush, Sally E; Brooks, Douglas A

    2016-01-01

    Lipids have an important role in many aspects of cell biology, including membrane architecture/compartment formation, intracellular traffic, signalling, hormone regulation, inflammation, energy storage and metabolism. Lipid biology is therefore integrally involved in major human diseases, including metabolic disorders, neurodegenerative diseases, obesity, heart disease, immune disorders and cancers, which commonly display altered lipid transport and metabolism. However, the investigation of these important cellular processes has been limited by the availability of specific tools to visualise lipids in live cells. Here we describe the potential for ReZolve-L1™ to localise to intracellular compartments containing polar lipids, such as for example sphingomyelin and phosphatidylethanolamine. In live Drosophila fat body tissue from third instar larvae, ReZolve-L1™ interacted mainly with lipid droplets, including the core region of these organelles. The presence of polar lipids in the core of these lipid droplets was confirmed by Raman mapping and while this was consistent with the distribution of ReZolve-L1™ it did not exclude that the molecular probe might be detecting other lipid species. In response to complete starvation conditions, ReZolve-L1™ was detected mainly in Atg8-GFP autophagic compartments, and showed reduced staining in the lipid droplets of fat body cells. The induction of autophagy by Tor inhibition also increased ReZolve-L1™ detection in autophagic compartments, whereas Atg9 knock down impaired autophagosome formation and altered the distribution of ReZolve-L1™. Finally, during Drosophila metamorphosis fat body tissues showed increased ReZolve-L1™ staining in autophagic compartments at two hours post puparium formation, when compared to earlier developmental time points. We concluded that ReZolve-L1™ is a new live cell imaging tool, which can be used as an imaging reagent for the detection of polar lipids in different intracellular

  11. Probing quantum coherence in single-atom electron spin resonance

    Science.gov (United States)

    Willke, Philip; Paul, William; Natterer, Fabian D.; Yang, Kai; Bae, Yujeong; Choi, Taeyoung; Fernández-Rossier, Joaquin; Heinrich, Andreas J.; Lutz, Christoper P.

    2018-01-01

    Spin resonance of individual spin centers allows applications ranging from quantum information technology to atomic-scale magnetometry. To protect the quantum properties of a spin, control over its local environment, including energy relaxation and decoherence processes, is crucial. However, in most existing architectures, the environment remains fixed by the crystal structure and electrical contacts. Recently, spin-polarized scanning tunneling microscopy (STM), in combination with electron spin resonance (ESR), allowed the study of single adatoms and inter-atomic coupling with an unprecedented combination of spatial and energy resolution. We elucidate and control the interplay of an Fe single spin with its atomic-scale environment by precisely tuning the phase coherence time T2 using the STM tip as a variable electrode. We find that the decoherence rate is the sum of two main contributions. The first scales linearly with tunnel current and shows that, on average, every tunneling electron causes one dephasing event. The second, effective even without current, arises from thermally activated spin-flip processes of tip spins. Understanding these interactions allows us to maximize T2 and improve the energy resolution. It also allows us to maximize the amplitude of the ESR signal, which supports measurements even at elevated temperatures as high as 4 K. Thus, ESR-STM allows control of quantum coherence in individual, electrically accessible spins. PMID:29464211

  12. Acceleration of polarized electrons in the Bonn electron-accelerator facility ELSA

    International Nuclear Information System (INIS)

    Hoffmann, M.

    2001-12-01

    The future medium energy physics program at the electron stretcher accelerator ELSA of Bonn University mainly relies on experiments using polarized electrons in the energy range from 1 to 3.2 GeV. To prevent depolarization during acceleration in the circular accelerators several depolarizing resonances have to be corrected for. Intrinsic resonances are compensated using two pulsed betatron tune jump quadrupoles. The influence of imperfection resonances is successfully reduced applying a dynamic closed orbit correction in combination with an empirical harmonic correction on the energy ramp. Both types of resonances and the correction techniques have been studied in detail. The imperfection resonances were used to calibrate the energy of the stretcher ring with high accuracy. A new technique to extract the beam with horizontal oriented polarization was successfully installed. For all energies a polarized electron beam with more than 50% polarization can now be supplied to the experiments at ELSA, which is demonstrated by measurements using a Moeller polarimeter installed in the external beamline. (orig.)

  13. Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor

    Science.gov (United States)

    Kinoshita, Yuto; Kida, Noriaki; Miyamoto, Tatsuya; Kanou, Manabu; Sasagawa, Takao; Okamoto, Hiroshi

    2018-04-01

    The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate the spin-polarized electrons on the subpicosecond timescale. Here, we report one such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after the resonant excitation of the interband transition between the Rashba-type spin-splitting energy bands with a femtosecond laser pulse circularly polarized. The phase of the emitted terahertz waves is reversed by switching the circular polarization. This suggests that the observed terahertz radiation originates from the subpicosecond spin-polarized photocurrents, which are generated by the asymmetric depopulation of the Dirac state. Our result provides a way for the current-induced terahertz radiation and its phase control by the circular polarization of incident light without external electric fields.

  14. Electronic predistortion for compensation of polarization-mode dispersion

    Science.gov (United States)

    Hellerbrand, Stephan; Hanik, Norbert; Weiershausen, W.

    2009-01-01

    One of the major impairments in high-speed optical transmission links is Polarization-Mode Dispersion (PMD). We propose the method of electronic predistortion (EPD) for the mitigation of PMD. This approach has already been successfully applied for the compensation of Chromatic Dispersion (CD) and Fiber-Nonlinearities. The advantage of this method is that impairments can efficiently be mitigated without the need for coherent reception. The proposed scheme is based on the possibility to control the optical field at the transmitter by using two complex modulators for the modulation of two orthogonally polarized optical signals. If the physical origin of PMD is exactly known then the ideal predistorted field and the corresponding electrical driving signals can be computed accurately. In practice, however, this information is not available. Therefore it is shown how to determine appropriate driving signals for a set of measured PMD parameters. Measurements will be communicated through a feedback channel in practice. We suggest a possible strategy for application of this technique in scenarios, in which the adaptation speed is intrinsically limited due to the round-trip delay. Numerical simulations reveal that the use of EPD can significantly increase the tolerance towards PMD in comparison to a system without compensation.

  15. What do we learn from polarization measurements in deep-inelastic electron-nucleon scattering

    International Nuclear Information System (INIS)

    Anselmino, M.

    1979-01-01

    We examine what can be learned from deep-inelastic electron-nucleon scattering with polarized initial electrons and measurement of the polarization of the final electrons. A direct evaluation of the separate structure functions W 1 and W 2 is shown to be possible

  16. Parity violation in inelastic scattering of polarized electrons

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1978-10-01

    Parity nonconservation was observed in the inelastic scattering of longitudinally polarized electrons from an unpolarized deuterium target at 19.4 and 22.2 GeV. An asymmetry A = (sigma/sub R/ - sigma/sub L)/(sigma/sub R/ + sigma/sub L/) = (-9.5 +- 1.6) x 10 -5 Q 2 , Q 2 in (GeV/c) 2 was found for values of Q 2 near 1.4. The statistical and systematic errors are each about 9 percent of the measured asymmetry. This result is consistent with predictions from the standard Weinberg--Salam SU(2) x U(1) model. Using the simple quark-parton model of the nucleon, the value sin 2 theta/sub W/ = 0.20 +- 0.03 is obtained. 21 references

  17. High voltage processing of the SLC polarized electron gun

    International Nuclear Information System (INIS)

    Saez, P.; Clendenin, J.; Garden, C.; Hoyt, E.; Klaisner, L.; Prescott, C.; Schultz, D.; Tang, H.

    1993-04-01

    The SLC polarized electron gun operates at 120 kV with very low dark current to maintain the ultra high vacuum (UHV). This strict requirement protects the extremely sensitive photocathode from contaminants caused by high voltage (HV) activity. Thorough HV processing is thus required x-ray sensitive photographic film, a nanoammeter in series with gun power supply, a radiation meter, a sensitive residual gas analyzer and surface x-ray spectrometry were used to study areas in the gun where HV activity occurred. By reducing the electric field gradients, carefully preparing the HV surfaces and adhering to very strict clean assembly procedures, we found it possible to process the gun so as to reduce both the dark current at operating voltage and the probability of HV discharge. These HV preparation and processing techniques are described

  18. B meson physics with polarized electron beams at the SLC

    International Nuclear Information System (INIS)

    Atwood, W.B.

    1988-09-01

    The expected large cross-section for e + e - → Z 0 and subsequent decay to b/bar b/ quarks makes the Z 0 an attractive place to pursue B meson physics. In addition, the big Electroweak asymmetries, thought to exist in Z 0 decays to b/bar b/ quarks with polarized electron beams, provide an outstanding handle for observation of such effects as B 0 -/bar B/ 0 mixing. In this paper, the feasibility of such measurements is investigated and, with relatively small samples of Z 0 's (a few hundred thousand), both B/sub d/ and B/sub s/ meson mixing are shown to be measurable. The subject of CP violation in neutral B mesons is discussed last, but presently such measurements seem to be out of reach. 7 refs., 6 figs., 3 tabs

  19. Quantum mechanical force field for water with explicit electronic polarization.

    Science.gov (United States)

    Han, Jaebeom; Mazack, Michael J M; Zhang, Peng; Truhlar, Donald G; Gao, Jiali

    2013-08-07

    A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensed-phase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen- and hydrogen-containing compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a three-point charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with three-point-charge potential) model, is suitable for modeling both gas-phase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 × 10(6) self-consistent-field calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as across

  20. Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization.

    Science.gov (United States)

    Lin, Qisheng; Miller, Gordon J

    2018-01-16

    Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e - /atom show a plethora of unprecedented and fascinating structural motifs and bonding features. Therefore, establishing simple structure-bonding-property relationships is especially challenging for this compound class because commonly accepted valence electron counting rules are inappropriate. During our efforts to find quasicrystals and crystalline approximants by valence electron tuning near 2.0 e - /atom, we observed that compositions close to those of quasicrystals are exceptional sources for unprecedented valence electron-poor polar intermetallics, e.g., Ca 4 Au 10 In 3 containing (Au 10 In 3 ) wavy layers, Li 14.7 Mg 36.8 Cu 21.5 Ga 66 adopting a type IV clathrate framework, and Sc 4 Mg x Cu 15-x Ga 7.5 that is incommensurately modulated. In particular, exploratory syntheses of AAu 3 T (A = Ca, Sr, Ba and T = Ge, Sn) phases led to interesting bonding features for Au, such as columns, layers, and lonsdaleite-type tetrahedral frameworks. Overall, the breadth of Au-rich polar intermetallics originates, in part, from significant relativistics effect on the valence electrons of Au, effects which result in greater 6s/5d orbital mixing, a small effective metallic radius, and an enhanced Mulliken electronegativity, all leading to ultimate enhanced binding with nearly all metals including itself. Two other successful strategies to mine electron-poor polar intermetallics include lithiation and "cation-rich" phases. Along these lines, we have studied lithiated Zn-rich compounds in which structural

  1. Electron polar cap and the boundary of open geomagnetic field lines.

    Science.gov (United States)

    Evans, L. C.; Stone, E. C.

    1972-01-01

    A total of 333 observations of the boundary of the polar access region for electrons (energies greater than 530 keV) provides a comprehensive map of the electron polar cap. The boundary of the electron polar cap, which should occur at the latitude separating open and closed field lines, is consistent with previously reported closed field line limits determined from trapped-particle data. The boundary, which is sharply defined, seems to occur at one of three discrete latitudes. Although the electron flux is generally uniform across the polar cap, a limited region of reduced access is observed about 10% of the time.

  2. Antiferromagnetic Spin Coupling between Rare Earth Adatoms and Iron Islands Probed by Spin-Polarized Tunneling.

    Science.gov (United States)

    Coffey, David; Diez-Ferrer, José Luis; Serrate, David; Ciria, Miguel; de la Fuente, César; Arnaudas, José Ignacio

    2015-09-03

    High-density magnetic storage or quantum computing could be achieved using small magnets with large magnetic anisotropy, a requirement that rare-earth iron alloys fulfill in bulk. This compelling property demands a thorough investigation of the magnetism in low dimensional rare-earth iron structures. Here, we report on the magnetic coupling between 4f single atoms and a 3d magnetic nanoisland. Thulium and lutetium adatoms deposited on iron monolayer islands pseudomorphically grown on W(110) have been investigated at low temperature with scanning tunneling microscopy and spectroscopy. The spin-polarized current indicates that both kind of adatoms have in-plane magnetic moments, which couple antiferromagnetically with their underlying iron islands. Our first-principles calculations explain the observed behavior, predicting an antiparallel coupling of the induced 5d electrons magnetic moment of the lanthanides with the 3d magnetic moment of iron, as well as their in-plane orientation, and pointing to a non-contribution of 4f electrons to the spin-polarized tunneling processes in rare earths.

  3. Reproducibility of the cutoff probe for the measurement of electron density

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Oh, W. Y. [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); You, S. J., E-mail: sjyou@cnu.ac.kr [Department of Physics, Chungnam National University, Daejeon 305-701 (Korea, Republic of); Kwon, J. H.; You, K. H.; Seo, B. H.; Kim, J. H., E-mail: jhkim86@kriss.re.kr [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); Yoon, J.-S. [Plasma Technology Research Center, National Fusion Research Institute, Gunsan 573-540 (Korea, Republic of)

    2016-06-15

    Since a plasma processing control based on plasma diagnostics attracted considerable attention in industry, the reproducibility of the diagnostics using in this application has become a great interest. Because the cutoff probe is one of the potential candidates for this application, knowing the reproducibility of the cutoff probe measurement becomes quit important in the cutoff probe application research. To test the reproducibility of the cutoff probe measurement, in this paper, a comparative study among the different cutoff probe measurements was performed. The comparative study revealed remarkable result: the cutoff probe has a great reproducibility for the electron density measurement, i.e., there are little differences among measurements by different probes made by different experimenters. The discussion including the reason for the result was addressed via this paper by using a basic measurement principle of cutoff probe and a comparative experiment with Langmuir probe.

  4. Reproducibility of the cutoff probe for the measurement of electron density

    International Nuclear Information System (INIS)

    Kim, D. W.; Oh, W. Y.; You, S. J.; Kwon, J. H.; You, K. H.; Seo, B. H.; Kim, J. H.; Yoon, J.-S.

    2016-01-01

    Since a plasma processing control based on plasma diagnostics attracted considerable attention in industry, the reproducibility of the diagnostics using in this application has become a great interest. Because the cutoff probe is one of the potential candidates for this application, knowing the reproducibility of the cutoff probe measurement becomes quit important in the cutoff probe application research. To test the reproducibility of the cutoff probe measurement, in this paper, a comparative study among the different cutoff probe measurements was performed. The comparative study revealed remarkable result: the cutoff probe has a great reproducibility for the electron density measurement, i.e., there are little differences among measurements by different probes made by different experimenters. The discussion including the reason for the result was addressed via this paper by using a basic measurement principle of cutoff probe and a comparative experiment with Langmuir probe.

  5. The ELSA laser beamline for electron polarization measurements via Compton backscattering

    Energy Technology Data Exchange (ETDEWEB)

    Switka, Michael; Hinterkeuser, Florian; Koop, Rebecca; Hillert, Wolfgang [Electron Stretcher Facility ELSA, Physics Institute of Bonn University (Germany)

    2016-07-01

    The Electron Stretcher Facility ELSA provides a spin polarized electron beam with energies of 0.5 - 3.2 GeV for double polarization hadron physics experiments. As of 2015, the laser beamline of the polarimeter based on Compton backscattering restarted operation. It consists of a cw disk laser with design total beam power of 40 W and features two polarized 515 nm photon beams colliding head-on with the stored electron beam in ELSA. The polarization measurement is based on the vertical profile asymmetry of the back-scattered photons, which is dependent on the polarization degree of the stored electron beam. After recent laser repairs, beamline and detector modifications, the properties of the beamline have been determined and first measurements of the electron polarization degree were conducted. The beamline performance and first measurements are presented.

  6. Polarized Electron Beams for Nuclear Physics at the MIT Bates Accelerator Center

    CERN Document Server

    Farkhondeh, Manouchehr; Franklin, Wilbur; Ihloff, Ernie; McAllister, Brian; Milner, Richard; North, William; Tschalär, C; Tsentalovich, Evgeni; Wang, Defa; Wang, Dong; Wang, Fuhua; Zolfaghari, Abbasali; Zwart, Townsend; van der Laan, Jan

    2005-01-01

    The MIT Bates Accelerator Center is delivering highly polarized electron beams to its South Hall Ring for use in Nuclear Physics Experiments. Circulating electron currents in excess of 200 mA with polarization of 70% are scattered from a highly polarized, but very thin atomic beam source deuterium target. At the electron source a compact diode laser creates photoemission of quasi-CW mA pulses of polarized electrons at low duty factors from a strained GaAs photocathode. Refurbished RF transmitters provide power to the 2856 MHz linac, accelerating the beam to 850 MeV in two passes before injection into the South Hall Ring. In the ring a Siberian snake serves to maintain a high degree of longitudinal polarization at the BLAST scattering target. A Compton laser back-scattering polarimeter measures the electron beam polarization with a statistical acuracy of 6% every 15 minutes.

  7. Optimization of the transverse electron polarization of HERA at 26.7 GeV

    International Nuclear Information System (INIS)

    Grosshauser, C.

    1994-08-01

    The methods applied for the optimization of the transverse electron polarization were presented in the following and the measurements performed by this extensively described. By these measurements could be shown that in pure electron-beam operation a degree of polarization of P similar 67% can be reached. A adjustment of the electron storage ring determined by this allows also under luminosity conditions without further optimization an only fewly deminuished transverse electron polarization. The measured polarization values where thereby over several hours stable and could also after months be reproduced. An interference of the polarization by electron-proton collisions could not be stated in the framework of the measurements. In an optimization of the electron polarization performed during the luminosity operation polarization values of P similar 67% could be reached. Thereby could be stated that an optimization of the electron polarization can be perforemd parallel to the data taking of the experiments H1 and ZEUS without fearing of extensive interferences for the measurement conditions of the experiments. By means of the resonance depolarization, which was at HERA for the first time successfully applied, the electron energy was determined with a maximal error of similar 3 MeV and an energy calibration of the HERA electron storage ring performed. At this energy calibration a mean deviation of the nominal energy from the energy values, which were determined by means of the depolarization measurements, of similar 35 MeV resulted. By the different studies on the transverse electron polarization and by the production of the worldwide first longitudinally polarized electron beam in a storage ring, in which a degree of polarization of P long ≥55% was observed, could be shown that a data taking of the experiment HERMES can be pursued parallel to the experiments H1 and ZEUS in the electron storage ring HERA

  8. Quantitative electron probe microanalysis of boron in binary borides

    International Nuclear Information System (INIS)

    Bastin, G.F.; Heijligers, H.J.M.

    1986-01-01

    Quantitative electron probe microanalysis has been performed in 27 binary borides in the range of 4-30 keV, both for the metals as well as for Boron. The procedures along which accurate intensity measurements for B-K α must be carried out are discussed in detail. A total of 196 k-ratios with respect to elemental standards for the metal X-ray lines and 180 k-ratios for B-K α relative to elemental Boron have been obtained. These data have been used to arrive at an improved parameterization for the φ(ρz) approach in matrix correction. The resulting new program (BAS861) was compared to 5 other current correction programs. At the same occasion the available set of mass absorption coefficients for Boron was tested on its consistency and better values suggested where necessary. Finally it is shown that the modified version of the Gaussian φ(ρz) approach (BAS861 program) is highly successful in the matrix correction for B-K α : a relative root-mean-square value of 6.30% was obtained. (Auth.)

  9. 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.

  10. Bulk electron spin polarization generated by the spin Hall current

    OpenAIRE

    Korenev, V. L.

    2005-01-01

    It is shown that the spin Hall current generates a non-equilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known equilibrium polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

  11. Bulk electron spin polarization generated by the spin Hall current

    Science.gov (United States)

    Korenev, V. L.

    2006-07-01

    It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

  12. Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

    Science.gov (United States)

    Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

    . Faraday Discuss., 133 (2006), 393-401 [7] Snow T.P. and Bierbaum V.M.: Ion chemistry in the interstellar medium. Ann. Rev. Analyt. Chem. 1 (2008), 229-259. [8] Nuevo M., Meierhenrich U.J., Muñoz Caro G.M., Dartois E., d'Hendecourt L., Deboffle D., n Auger G., Blanot D., Bredehüft J.H. and Nahon L.: The effects of circularly polarized light on amino acid enantiomers produced by the UV irradiation of interstellar ice analogs. AA 457 (2006), 741-751 [9] Shimamura I and Takayanagi K. (eds): Electron-Molecule Collisions. Plenum Press, New York, USA (1984) [10] Hamann T., Bühler E., Swiderek P.: Low-energy-electron-induced hydroamination of an alkene. Angew Chem Int Ed Engl. 48(25) (2009), 4643-4645.

  13. The effect of driven electron-phonon coupling on the electronic conductance of a polar nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Mardaani, Mohammad, E-mail: mohammad-m@sci.sku.ac.ir; Rabani, Hassan, E-mail: rabani-h@sci.sku.ac.ir [Department of Physics, Faculty of Science, Shahrekord University, P. O. Box 115, Shahrekord (Iran, Islamic Republic of); Nanotechnology Research Center, Shahrekord University, 8818634141 Shahrekord (Iran, Islamic Republic of); Esmaili, Esmat; Shariati, Ashrafalsadat [Department of Physics, Faculty of Science, Shahrekord University, P. O. Box 115, Shahrekord (Iran, Islamic Republic of)

    2015-08-07

    A semi-classical model is proposed to explore the effect of electron-phonon coupling on the coherent electronic transport of a polar chain which is confined between two rigid leads in the presence of an external electric field. To this end, we construct the model by means of Green's function technique within the nearest neighbor tight-binding and harmonic approximations. For a time-periodic electric field, the atomic displacements from the equilibrium positions are obtained precisely. The result is then used to compute the electronic transport properties of the chain within the Peierls-type model. The numerical results indicate that the conductance of the system shows interesting behavior in some special frequencies. For each special frequency, there is an electronic quasi-state in which the scattering of electrons by vibrating atoms reaches maximum. The system electronic conductance decreases dramatically at the strong electron-phonon couplings and low electron energies. In the presence of damping forces, the electron-phonon interaction has a less significant effect on the conductance.

  14. The effect of driven electron-phonon coupling on the electronic conductance of a polar nanowire

    International Nuclear Information System (INIS)

    Mardaani, Mohammad; Rabani, Hassan; Esmaili, Esmat; Shariati, Ashrafalsadat

    2015-01-01

    A semi-classical model is proposed to explore the effect of electron-phonon coupling on the coherent electronic transport of a polar chain which is confined between two rigid leads in the presence of an external electric field. To this end, we construct the model by means of Green's function technique within the nearest neighbor tight-binding and harmonic approximations. For a time-periodic electric field, the atomic displacements from the equilibrium positions are obtained precisely. The result is then used to compute the electronic transport properties of the chain within the Peierls-type model. The numerical results indicate that the conductance of the system shows interesting behavior in some special frequencies. For each special frequency, there is an electronic quasi-state in which the scattering of electrons by vibrating atoms reaches maximum. The system electronic conductance decreases dramatically at the strong electron-phonon couplings and low electron energies. In the presence of damping forces, the electron-phonon interaction has a less significant effect on the conductance

  15. 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.

  16. Low Emittance Guns for the ILC Polarized Electron Beam

    International Nuclear Information System (INIS)

    Clendenin, J. E.; Brachmann, A.; Ioakeimidi, K.; Kirby, R. E.; Maruyama, T.; Miller, R. H.; Wang, J. W.; Zhou, F.

    2007-01-01

    Polarized electron beams generated by DC guns are routinely available at several accelerators including JLAB, Mainz and SLAC. These guns operate with a cathode bias on the order of -100 kV. To minimize space charge effects, relatively long bunches are generated at the gun and then compressed longitudinally external to the gun just before and during initial acceleration. For linear colliders, this compression is accomplished using a combination of rf bunchers. For the basic design of the International Linear Collider (ILC), a 120 kV DC photocathode gun is used to produce a series of nanosecond bunches that are each compressed by two sub-harmonic bunchers (SHBs) followed by an L-band buncher and capture section. The longitudinal bunching process results in a significantly higher emittance than produced by the gun alone. While high-energy experiments using polarized beams are not generally sensitive to the source emittance, there are several benefits to a lower source emittance including a simpler more efficient injector system and a lower radiation load during transport especially at bends as at the damping ring. For the ILC, the SHBs could be eliminated if the voltage of the gun is raised sufficiently. Simulations using the General Particle Tracer (GPT) package indicate that a cathode bias voltage of ≥200 kV should allow both SHBs to be operated at 433 or even 650 MHz, while ≥500 kV would be required to eliminate the SHBs altogether. Simulations can be used to determine the minimum emittance possible if the injector is designed for a given increased voltage. A possible alternative to the DC gun is an rf gun. Emittance compensation, routinely used with rf guns, is discussed for higher-voltage DC guns

  17. Low Emittance Guns for the ILC Polarized Electron Beam

    International Nuclear Information System (INIS)

    Clendenin, J.E.; Brachmann, A.; Ioakeimidi, K.; Kirby, R.E.; Maruyama, T.; Miller, R.H.; Wang, J.W.; Zhou, F.; SLAC

    2006-01-01

    Polarized electron beams generated by DC guns are routinely available at several accelerators including JLAB, Mainz and SLAC. These guns operate with a cathode bias on the order of -100 kV. To minimize space charge effects, relatively long bunches are generated at the gun and then compressed longitudinally external to the gun just before and during initial acceleration. For linear colliders, this compression is accomplished using a combination of rf bunchers. For the basic design of the International Linear Collider (ILC), a 120 kV DC photocathode gun is used to produce a series of nanosecond bunches that are each compressed by two sub-harmonic bunchers (SHBs) followed by an L-band buncher and capture section. The longitudinal bunching process results in a significantly higher emittance than produced by the gun alone. While high-energy experiments using polarized beams are not generally sensitive to the source emittance, there are several benefits to a lower source emittance including a simpler more efficient injector system and a lower radiation load during transport especially at bends as at the damping ring. For the ILC, the SHBs could be eliminated if the voltage of the gun is raised sufficiently. Simulations using the General Particle Tracer (GPT) package indicate that a cathode bias voltage of (ge)200 kV should allow both SHBs to be operated at 433 or even 650 MHz, while (ge)500 kV would be required to eliminate the SHBs altogether. Simulations can be used to determine the minimum emittance possible if the injector is designed for a given increased voltage. A possible alternative to the DC gun is an rf gun. Emittance compensation, routinely used with rf guns, is discussed for higher-voltage DC guns

  18. Theory of Inclusive Scattering of Polarized Electrons by Polarized $^{3}$He and the Neutron Form Factors

    OpenAIRE

    Atti, C. Ciofi degli; Pace, E.; Salmé, G.

    1993-01-01

    The theory of inclusive lepton scattering of polarized leptons by polarized J = 1/2 hadrons is presented and the origin of different expressions for the polarized nuclear response function appearing in the literature is explained. The sensitivity of the longitudinal asymmetry upon the neutron form factors is investigated.

  19. Plasma potential measurements in the edge region of the ISTTOK plasma, using electron emissive probes

    International Nuclear Information System (INIS)

    Ionita, C.; Balan, P.; Schrittwieser, R.; Cabral, J.A.; Fernandes, H.; Figueiredo, H. F.C.; Varandas, C.

    2001-01-01

    We have recently started to use electron-emissive probes for direct measurements of the plasma potential and its fluctuations in the edge region of the plasma ring in the tokamak ISTTOK in Lisbon, Portugal. This method is based on the fact that the electron emission current of such a probe is able to compensate electron temperature variations and electron drifts, which can occur in the edge plasma region of magnetized fusion devices, and which are making measurements with cold probes prone to errors. In this contribution we present some of the first results of our investigations in ISTTOK.(author)

  20. The 50 kV inverted source of polarized electrons at ELSA

    International Nuclear Information System (INIS)

    Hillert, Wolfgang; Gowin, Michael; Neff, Berhold

    2001-01-01

    The future medium energy physics program at the electron stretcher accelerator ELSA of Bonn University mainly relies on experiments requiring a beam of polarized electrons and a polarized target. To provide a polarized beam with high polarization and sufficient intensity a pulsed 50 kV inverted gun of polarized electrons has been set into operation. The gun is operated in space charge limitation, producing a peak current of 100 mA in rectangular 1μs long electron pulses. Photocathode lifetime during operation is higher than 3000 hours. Using a Be-InGaAs/Be-AlGaAs superlattice photocathode a polarization of 80% and a corresponding quantum efficiency of 0.4% could be obtained

  1. Status report of the Darmstadt polarized electron source at the S-DALINAC

    Energy Technology Data Exchange (ETDEWEB)

    Poltoratska, Yuliya; Barday, Roman; Bonnes, Uwe; Brunken, Marco; Eichhorn, Ralf; Eckardt, Christian; Enders, Joachim; Ingenhaag, Christoph; Goeoek, Alf; Platz, Markus; Roth, Markus; Wagner, Markus [Institut fuer Kernphysik, Technische Universitaet, Darmstadt (Germany); Mueller, Wolfgang F.O.; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder, Technische Universitaet, Darmstadt (Germany)

    2009-07-01

    The injection section of the superconducting Darmstadt electron linear accelerator S-DALINAC will soon be extended with a source of polarized electrons SPIN. The set-up consists of a 100 keV GaAs polarized gun and associated beamline including a Chopper-Prebuncher system to affect the time structure of the emitted beam, a laser system to produce polarized light with the required wavelength and an assembly for polarisation manipulation and measurement. We report on the status of the entire construction and review recent results on operation parameters. An outlook on the upcoming installation of the polarized electron source at the S-DALINAC is given.

  2. Monte Carlo study of electron relaxation in graphene with spin polarized, degenerate electron gas in presence of electron-electron scattering

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2017-12-01

    The Monte Carlo simulation method is applied to study the relaxation of excited electrons in monolayer graphene. The presence of spin polarized background electrons population, with density corresponding to highly degenerate conditions is assumed. Formulas of electron-electron scattering rates, which properly account for electrons presence in two energetically degenerate, inequivalent valleys in this material are presented. The electron relaxation process can be divided into two phases: thermalization and cooling, which can be clearly distinguished when examining the standard deviation of electron energy distribution. The influence of the exchange effect in interactions between electrons with parallel spins is shown to be important only in transient conditions, especially during the thermalization phase.

  3. Spin asymmetry in proton-proton collisions as a probe of sea and gluon polarization in a proton

    International Nuclear Information System (INIS)

    Cheng, H.; Lai, S.

    1990-01-01

    Quark and gluon spin densities in a proton are phenomenologically parametrized based on the European Muon Collaboration (EMC) data and on some plausible theoretical arguments. Four different characteristic values of gluon and sea polarizations suggested by various theoretical conjectures are considered. The sea polarization in a proton is probed by measuring the spin-spin asymmetry A LL DY in the Drell-Yan process, while the helicity asymmetry A LL γ in direct photon production at high p T is employed to test the gluon spin content. Helicity asymmetries in both processes are quite sizable. A LL DY is positive and of order 10 -1 if the sea is polarized opposite to the proton spin, as suggested by the EMC data. However, even in the absence of the sea polarization at the EMC energies, we find A LL DY to be large and negative. Experimental measurements of A LL DY and A LL γ together will not only provide a clean probe of sea and gluon polarizations, but also test whether the combination Δs-(α s /4π)ΔG inferred from the EMC data is valid, i.e., whether gluons contribute to the spin-dependent structure function g 1 p (x,Q 2 ) via the triangular anomaly

  4. Circular polarization of gravitational waves from non-rotating supernova cores: a new probe into the pre-explosion hydrodynamics

    Science.gov (United States)

    Hayama, Kazuhiro; Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya

    2018-06-01

    We present an analysis of the circular polarization of gravitational waves (GWs) using results from three-dimensional (3D), general relativistic (GR) core-collapse simulations of a non-rotating 15 M⊙ star. For the signal detection, we perform a coherent network analysis taking into account the four interferometers of LIGO Hanford, LIGO Livingston, VIRGO, and KAGRA. We focus on the Stokes V parameter, which directly characterizes the asymmetry of the GW circular polarization. We find that the amplitude of the GW polarization becomes bigger for our 3D-GR model that exhibits strong activity of the standing accretion shock instability (SASI). Our results suggest that the SASI-induced accretion flows to the proto-neutron star (PNS) lead to a characteristic, low-frequency modulation (100-200 Hz) in both the waveform and the GW circular polarization. By estimating the signal-to-noise ratio of the GW polarization, we demonstrate that the detection horizon of the circular polarization extends by more than a factor of several times farther comparing to that of the GW amplitude. Our results suggest that the GW circular polarization, if detected, could provide a new probe into the pre-explosion hydrodynamics such as the SASI activity and the g-mode oscillation of the PNS.

  5. Circular polarization of gravitational waves from non-rotating supernova cores: a new probe into the pre-explosion hydrodynamics

    Science.gov (United States)

    Hayama, Kazuhiro; Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya

    2018-04-01

    We present an analysis of the circular polarization of gravitational-waves (GWs) using results from three-dimensional (3D), general relativistic (GR) core-collapse simulations of a non-rotating 15M⊙ star. For the signal detection, we perform a coherent network analysis taking into account the four interferometers of LIGO Hanford, LIGO Livingston, VIRGO, and KAGRA. We focus on the Stokes V parameter, which directly characterizes the asymmetry of the GW circular polarization. We find that the amplitude of the GW polarization becomes bigger for our 3D-GR model that exhibits strong activity of the standing accretion shock instability (SASI). Our results suggest that the SASI-induced accretion flows to the proto-neutron star (PNS) lead to a characteristic, low-frequency modulation (100 ˜ 200 Hz) in both the waveform and the GW circular polarization. By estimating the signal-to-noise ratio of the GW polarization, we demonstrate that the detection horizon of the circular polarization extends by more than a factor of several times farther comparing to that of the GW amplitude. Our results suggest that the GW circular polarization, if detected, could provide a new probe into the pre-explosion hydrodynamics such as the SASI activity and the g-mode oscillation of the PNS.

  6. The production and extraction of polarized electrons from an optically pumped helium discharge

    International Nuclear Information System (INIS)

    Vandiver, R.J.; Schearer, L.D.; Gay, T.J.

    1992-01-01

    Polarized electrons are produced from interactions involving nearly 100% polarized helium 2 3 S 1 metastable atoms in a weak electrical discharge. The high metastable polarizations are obtained through the use of recently developed, high-power lasers tunable to the relevant helium transitions near 1083 nm and the development of a crossed beam pumping technique. The dominant interactions involving the 2 3 S 1 atoms and electrons are spin preserving; hence the electrons of the discharge attain a high polarization. The authors have extracted a well collimated electron beam with over 20 μA of current from the discharge. An optical polarimeter will be used to determine the polarization of the extracted electrons

  7. Sensing lymphoma cells based on a cell-penetrating/apoptosis-inducing/electron-transfer peptide probe

    International Nuclear Information System (INIS)

    Sugawara, Kazuharu; Shinohara, Hiroki; Kadoya, Toshihiko; Kuramitz, Hideki

    2016-01-01

    To electrochemically sense lymphoma cells (U937), we fabricated a multifunctional peptide probe that consists of cell-penetrating/apoptosis-inducing/electron-transfer peptides. Electron-transfer peptides derive from cysteine residue combined with the C-terminals of four tyrosine residues (Y_4). A peptide whereby Y_4C is bound to the C-terminals of protegrin 1 (RGGRLCYCRRRFCVCVGR-NH_2) is known to be an apoptosis-inducing agent against U937 cells, and is referred to as a peptide-1 probe. An oxidation response of the peptide-1 probe has been observed due to a phenolic hydroxyl group, and this response is decreased by the uptake of the peptide probe into the cells. To improve the cell membrane permeability against U937 cells, the RGGR at the N-terminals of the peptide-1 probe was replaced by RRRR (peptide-2 probe). In contrast, RNRCKGTDVQAWY_4C (peptide-3 probe), which recognizes ovalbumin, was constructed as a control. Compared with the other probes, the change in the peak current of the peptide-2 probe was the greatest at low concentrations and occurred in a short amount of time. Therefore, the cell membrane permeability of the peptide-2 probe was increased based on the arginine residues and the apoptosis-inducing peptides. The peak current was linear and ranged from 100 to 1000 cells/ml. The relative standard deviation of 600 cells/ml was 5.0% (n = 5). Furthermore, the membrane permeability of the peptide probes was confirmed using fluorescent dye. - Highlights: • We constructed a multifunctional peptide probe for the electrochemical sensing of lymphoma cells. • The peptide probe consists of cell-penetrating/apoptosis-inducing/electron-transfer peptides. • The electrode response of the peptide probe changes due to selective uptake into the cells.

  8. Sensing lymphoma cells based on a cell-penetrating/apoptosis-inducing/electron-transfer peptide probe

    Energy Technology Data Exchange (ETDEWEB)

    Sugawara, Kazuharu, E-mail: kzsuga@maebashi-it.ac.jp [Maebashi Institute of Technology, Gunma 371-0816 (Japan); Shinohara, Hiroki; Kadoya, Toshihiko [Maebashi Institute of Technology, Gunma 371-0816 (Japan); Kuramitz, Hideki [Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering for Research, University of Toyama, Toyama 930-8555 (Japan)

    2016-06-14

    To electrochemically sense lymphoma cells (U937), we fabricated a multifunctional peptide probe that consists of cell-penetrating/apoptosis-inducing/electron-transfer peptides. Electron-transfer peptides derive from cysteine residue combined with the C-terminals of four tyrosine residues (Y{sub 4}). A peptide whereby Y{sub 4}C is bound to the C-terminals of protegrin 1 (RGGRLCYCRRRFCVCVGR-NH{sub 2}) is known to be an apoptosis-inducing agent against U937 cells, and is referred to as a peptide-1 probe. An oxidation response of the peptide-1 probe has been observed due to a phenolic hydroxyl group, and this response is decreased by the uptake of the peptide probe into the cells. To improve the cell membrane permeability against U937 cells, the RGGR at the N-terminals of the peptide-1 probe was replaced by RRRR (peptide-2 probe). In contrast, RNRCKGTDVQAWY{sub 4}C (peptide-3 probe), which recognizes ovalbumin, was constructed as a control. Compared with the other probes, the change in the peak current of the peptide-2 probe was the greatest at low concentrations and occurred in a short amount of time. Therefore, the cell membrane permeability of the peptide-2 probe was increased based on the arginine residues and the apoptosis-inducing peptides. The peak current was linear and ranged from 100 to 1000 cells/ml. The relative standard deviation of 600 cells/ml was 5.0% (n = 5). Furthermore, the membrane permeability of the peptide probes was confirmed using fluorescent dye. - Highlights: • We constructed a multifunctional peptide probe for the electrochemical sensing of lymphoma cells. • The peptide probe consists of cell-penetrating/apoptosis-inducing/electron-transfer peptides. • The electrode response of the peptide probe changes due to selective uptake into the cells.

  9. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    International Nuclear Information System (INIS)

    Helm, Toni

    2013-01-01

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd 2-x Ce x CuO 4 (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  10. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    Energy Technology Data Exchange (ETDEWEB)

    Helm, Toni

    2013-09-18

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd{sub 2-x}Ce{sub x}CuO{sub 4} (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  11. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    Energy Technology Data Exchange (ETDEWEB)

    Helm, Toni

    2013-09-18

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd{sub 2-x}Ce{sub x}CuO{sub 4} (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  12. Radiation self-polarization of electrons moving in a magnetic field. [Vector spin operator, relaxation time

    Energy Technology Data Exchange (ETDEWEB)

    Bagrov, V G; Dorofeev, O F; Sokolov, A A; Ternov, I M; Khalilov, V R [Moskovskij Gosudarstvennyj Univ. (USSR)

    1975-03-11

    When electrons move in a magnetic field, synchrotron radiation gives rise to transitions accompanied by the electron spin reorientation. In this case, it is essential that the transition probability depends on the spin orientation; as a result electron polarization takes place with the spin orientation being predominantly opposite to the direction of the magnetic field. This effect has been called ''radiative self-polarization of electrons''. The present work is concerned with the question how the choice of the spin operator will affect the self-polarization degree and relaxation time. The problem has been solved for a vector spin operator.

  13. Measurement of plasma potential and electron temperature by ball-pen probes in RFX-MOD

    International Nuclear Information System (INIS)

    Brotankova, J.; Adamek, J.; Stockel, J.; Martines, E.; Spolaore, M.; Cavazzana, R.; Serianni, G.; Vianello, N.; Zuin, M.

    2009-01-01

    The ball-pen probe (BPP) is an innovative electric probe for direct measurements of the plasma potential. This probe was developed in IPP Prague and it is based on the Katsumata probe concept. Combined measurements of the plasma potential by a BPP and floating potential by a Langmuir probe provide also the value of the electron temperature. First test of the BPP on the RFX-mod reversed field pinch in Padova has been performed in November 2006. The BPP head, made of boron nitride, is equipped with four graphite collectors, which are positioned at four different radial positions h inside four shafts hollow into the probe head. The radial profile of the plasma potential and also the electron temperature were measured

  14. Pyrene-Containing ortho-Oligo(phenylene)ethynylene Foldamer as a Ratiometric Probe Based on Circularly Polarized Luminescence.

    Science.gov (United States)

    Reiné, Pablo; Justicia, Jose; Morcillo, Sara P; Abbate, Sergio; Vaz, Belen; Ribagorda, María; Orte, Ángel; Álvarez de Cienfuegos, Luis; Longhi, Giovanna; Campaña, Araceli G; Miguel, Delia; Cuerva, Juan M

    2018-04-20

    In this manuscript, we report the first synthesis of an organic monomolecular emitter, which behaves as a circularly polarized luminescence (CPL)-based ratiometric probe. The enantiopure helical ortho-oligo(phenylene)ethynylene ( o-OPE) core has been prepared by a new and efficient macrocyclization reaction. The combination of such o-OPE helical skeleton and a pyrene couple leads to two different CPL emission features in a single structure whose ratio linearly responds to silver(I) concentration.

  15. Generation of intense spin-polarized electron beams at the electron accelerator facility ELSA

    International Nuclear Information System (INIS)

    Heiliger, Dominik

    2014-08-01

    The inverted source of polarized electrons at the electron accelerator ELSA in Bonn routinely provides a pulsed and low energetic beam of polarized electrons (100 mA, 48 keV) by irradiating a GaAs strained-layer superlattice photocathode with laser light. Due to the beam energy of 48 keV the beam transport to the linear accelerator is strongly space charge dominated and the actual beam current has an impact on the beam dynamics. Thus, the optics of the transfer line to the linear accelerator must be optimized with respect to the chosen beam intensity. An intensity upgrade including numerical simulations of the beam transport as well as a generation and a transport of a beam current of nearly 200 mA was successfully operated. In order to enhance the reliability and uptime of the source, a new extreme high vacuum load lock system was installed and commissioned. It consists of an activation chamber for heat cleaning of the photocathodes and activation with cesium and oxygen, a storage in which different types of photocathodes can be stored and a loading chamber in which an atomic hydrogen source is used to remove nearly any remaining surface oxidation. The new cleaning procedure with atomic hydrogen was investigated regarding its potential to restore the initial quantum efficiency of the photocathode after many activations.

  16. Dynamic simulation of charging processes in polar dielectrics irradiated by the electron bunches of middle level energy

    International Nuclear Information System (INIS)

    Maslovskaya, A.G.

    2011-01-01

    Nowadays the scanning electron microscopy techniques are widely used practically in condenser matter physics to study properties and structure of solids. The electron probe of scanning electron microscope is not merely a passive indicator of the geometrical or potential profile of the sample surface, but also the source producing ionizing, electric and thermal action on the sample. The application of raster electron methods to polar materials, responding to electric and heat exposures of the electron bunches allows us to get a response and create new modes of image formation. Let assume, that a sample surface of dielectric is irradiated by thin focused electron bunches of middle level energy (with order 1÷50 keV). When electrons bombard the dielectric sample the accumulation of absorbed electrons occurs. As a result generated charged areas can irregular drift the initial bunches. Charging effect occurs at any magnifications and any actual probe current. This work considers the results of dynamic simulation of charging process in polar dielectrics under the investigation with the scanning electron microscope. The purpose of present study is design and model implementation of three-dimensional dynamic model of charge relaxation in polar materials irradiated by electron bunches of middle level energy. The mathematical problem definition is given by the system of the continuity equation and Poisson equation. Final system of equations was modified in terms of intrinsic radiation-induced conductivity in sample as well as cylindrical symmetry of the problem. The simulation is based on numerical method solving of boundary problem for partial derivative equation system. In addition the initial electron distribution is determined by Monte-Carlo method using the programming implementation. To solve this problem we used the computational methods of solution of nonstationary mathematical physics problem such as finite difference method and finite element method realized with

  17. Molecular frame photoemission by a comb of elliptical high-order harmonics: a sensitive probe of both photodynamics and harmonic complete polarization state.

    Science.gov (United States)

    Veyrinas, K; Gruson, V; Weber, S J; Barreau, L; Ruchon, T; Hergott, J-F; Houver, J-C; Lucchese, R R; Salières, P; Dowek, D

    2016-12-16

    Due to the intimate anisotropic interaction between an XUV light field and a molecule resulting in photoionization (PI), molecular frame photoelectron angular distributions (MFPADs) are most sensitive probes of both electronic/nuclear dynamics and the polarization state of the ionizing light field. Consequently, they encode the complex dipole matrix elements describing the dynamics of the PI transition, as well as the three normalized Stokes parameters s 1 , s 2 , s 3 characterizing the complete polarization state of the light, operating as molecular polarimetry. The remarkable development of advanced light sources delivering attosecond XUV pulses opens the perspective to visualize the primary steps of photochemical dynamics in time-resolved studies, at the natural attosecond to few femtosecond time-scales of electron dynamics and fast nuclear motion. It is thus timely to investigate the feasibility of measurement of MFPADs when PI is induced e.g., by an attosecond pulse train (APT) corresponding to a comb of discrete high-order harmonics. In the work presented here, we report MFPAD studies based on coincident electron-ion 3D momentum imaging in the context of ultrafast molecular dynamics investigated at the PLFA facility (CEA-SLIC), with two perspectives: (i) using APTs generated in atoms/molecules as a source for MFPAD-resolved PI studies, and (ii) taking advantage of molecular polarimetry to perform a complete polarization analysis of the harmonic emission of molecules, a major challenge of high harmonic spectroscopy. Recent results illustrating both aspects are reported for APTs generated in unaligned SF 6 molecules by an elliptically polarized infrared driving field. The observed fingerprints of the elliptically polarized harmonics include the first direct determination of the complete s 1 , s 2 , s 3 Stokes vector, equivalent to (ψ, ε, P), the orientation and the signed ellipticity of the polarization ellipse, and the degree of polarization P. They are

  18. Berry phase and shot noise for spin-polarized and entangled electrons

    International Nuclear Information System (INIS)

    Wang Pei; Tang Weihua; Lu Dinghui; Jiang Lixia; Zhao Xuean

    2007-01-01

    Shot noise for entangled and spin-polarized states in a four-probe geometric setup has been studied by adding two rotating magnetic fields in an incoming channel. Our results show that the noise power oscillates as the magnetic fields vary. The singlet, entangled triplet and polarized states can be distinguished by adjusting the magnetic fields. The Berry phase can be derived by measuring the shot noise power

  19. TESLA-N electron scattering with polarized targets at TESLA

    International Nuclear Information System (INIS)

    Korotokov, V.

    2001-01-01

    Measurements of polarized eN scattering can be realized at the TESLA linear collider facility at DESY with luminosities that are about two orders of magnitude higher than those expected for other experiments at comparable energies. A large variety of polarized parton distribution and fragmentation functions can be determined with unprecedented accuracy, many of them for the first time

  20. Spin polarization of electrons in a magnetic impurity doped ...

    Indian Academy of Sciences (India)

    Abstract. A theoretical model is presented in this paper for degree of spin polarization in a light emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different ...

  1. Spin polarization of electrons in a magnetic impurity doped ...

    Indian Academy of Sciences (India)

    A theoretical model is presented in this paper for degree of spin polarization in alight emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different temperatures and ...

  2. Blinded Comparison between an In-Air Reverberation Method and an Electronic Probe Tester in the Detection of Ultrasound Probe Faults.

    Science.gov (United States)

    Dudley, Nicholas J; Woolley, Darren J

    2017-12-01

    The aim of this study was to perform a blinded trial, comparing the results of a visual inspection of the in-air reverberation pattern with the results of an electronic probe tester in detecting ultrasound probe faults. Sixty-two probes were tested. A total of 28 faults were found, 3 only by in-air reverberation assessment and 2 only by the electronic probe tester. The electronic probe tester provided additional information regarding the location of the fault in 74% of the cases in which both methods detected a fault. It is possible to detect the majority of probe faults by visual inspection and in-air reverberation assessment. The latter provides an excellent first-line test, easily performed on a daily basis by equipment users. An electronic probe tester is required if detailed evaluation of faults is necessary. Copyright © 2017 World Federation for Ultrasound in Medicine and Biology. All rights reserved.

  3. Optically Polarized Conduction-Band Electrons in Tungsten Observed by Spin-Polarized Photoemission

    DEFF Research Database (Denmark)

    Zürcher, P.; Meier, F.; Christensen, N. E.

    1979-01-01

    Along the (100) direction of tungsten, interband transitions induced by circularly polarized light of energy 1.5 eV......Along the (100) direction of tungsten, interband transitions induced by circularly polarized light of energy 1.5 eV...

  4. Proceedings of the Workshop on future of nuclear physics in Europe with polarized electrons and photons

    International Nuclear Information System (INIS)

    Didelez, J.P.; Tamas, G.

    1990-01-01

    In the proceedings of the workshop, held at the Institut de Physique Nucleaire in Orsay, France, full texts of 20 contributions are presented. The two main topics were polarized electrons and polarized photons. It has been reported that significant processes have been made recently in the science and technology of polarized electron sources, polarized targets and polarimeters. The relevant tools are therefore now available to complete extensive experimental programs. The 20 papers are indexed and abstracted separately for the INIS database. (R.P.)

  5. Spider: Probing the Early Universe with a Large-Scale CMB Polarization Survey

    Science.gov (United States)

    Jones, William

    The standard dark-matter and dark-energy dominated cosmological model (LCDM) has proven to be remarkably successful in describing the current state and past evolution of the Universe. However, there remain significant uncertainties regarding the physical mechanisms that established the initial conditions upon which the LCDM predictions rely. Theories of cosmic genesis - the extremely high energy mechanisms that established these conditions - should be expected to provide a natural description of the nearly flat geometry of the Universe, the existence of super-horizon density correlations, and the adiabatic, Gaussian and nearly scale-invariant nature of the observed primordial density perturbations. The primary objective of Spider is to subject models of the early Universe to observational test, probing fundamental physics at energy scales far beyond the reach of terrestrial particle accelerators. The main scientific result will be to characterize, or place stringent upper limits on the level of the odd-parity polarization of the CMB. In the context of the inflationary paradigm, Spider will confirm or exclude the predictions of the simplest single-field inflationary models near the Lyth bound, characterized by tensor to scalar ratios r 0.03. While viable alternatives to the inflationary paradigm are an active and important area of investigation, including string cosmologies and cyclic models, early Universe models described by inflationary periods are now widely accepted as the underlying cause behind much of what we observe in cosmology today. Nevertheless, we know very little about the mechanism that would drive inflation or the energy scale at which it occurred, and the paradigm faces significant questions about the viability of the framework as a scientific theory. Fortunately, inflationary paradigms and alternative theories offer distinct predictions regarding the statistical properties of the Cosmic Microwave Background radiation. Spider will use measurements

  6. Electronic transport at semiconductor surfaces - from point-contact transistor to micro-four-point probes

    DEFF Research Database (Denmark)

    Hasegawa, S.; Grey, Francois

    2002-01-01

    show that this type of conduction is measurable using new types of experimental probes, such as the multi-tip scanning tunnelling microscope and the micro-four-point probe. The resulting electronic transport properties are intriguing, and suggest that semiconductor surfaces should be considered...

  7. 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.

  8. 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.

  9. Proceedings of the workshop on photocathodes for polarized electron sources for accelerators

    International Nuclear Information System (INIS)

    Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D.

    1994-04-01

    Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode

  10. Proceedings of the workshop on photocathodes for polarized electron sources for accelerators. Revision

    Energy Technology Data Exchange (ETDEWEB)

    Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D. [eds.

    1994-04-01

    Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode.

  11. Photo-Induced Electron Spin Polarization in a Narrow Band Gap Semiconductor Nanostructure

    International Nuclear Information System (INIS)

    Peter, A. John; Lee, Chang Woo

    2012-01-01

    Photo-induced spin dependent electron transmission through a narrow gap InSb/InGa x Sb 1−x semiconductor symmetric well is theoretically studied using transfer matrix formulism. The transparency of electron transmission is calculated as a function of electron energy for different concentrations of gallium. Enhanced spin-polarized photon assisted resonant tunnelling in the heterostructure due to Dresselhaus and Rashba spin-orbit coupling induced splitting of the resonant level and compressed spin-polarization are observed. Our results show that Dresselhaus spin-orbit coupling is dominant for the photon effect and the computed polarization efficiency increases with the photon effect and the gallium concentration

  12. Fractal model of polarization switching kinetics in ferroelectrics under nonequilibrium conditions of electron irradiation

    Science.gov (United States)

    Maslovskaya, A. G.; Barabash, T. K.

    2018-03-01

    The paper presents the results of the fractal and multifractal analysis of polarization switching current in ferroelectrics under electron irradiation, which allows statistical memory effects to be estimated at dynamics of domain structure. The mathematical model of formation of electron beam-induced polarization current in ferroelectrics was suggested taking into account the fractal nature of domain structure dynamics. In order to realize the model the computational scheme was constructed using the numerical solution approximation of fractional differential equation. Evidences of electron beam-induced polarization switching process in ferroelectrics were specified at a variation of control model parameters.

  13. An L-Band Polarized Electron PWT Photoinjector for the International Linear Collider (ILC)

    CERN Document Server

    Yu, David; Chen Ping; Lundquist, Martin; Luo, Yan; Smirnov, Alexei Yu

    2005-01-01

    A multi-cell, standing-wave, L-band, p-mode, plane-wave-transformer (PWT) photoinjector with an integrated photocathode in a novel linac structure is proposed by DULY Research Inc. as a polarized electron source. The PWT photoinjector is capable of operation in ultra high vacuum and moderate field gradient. Expected performance of an L-band polarized electron PWT injector operating under the parameters for the International Linear Collider is presented. The projected normalized transverse rms emittance is an order of magnitude lower than that produced with a polarized electron dc gun followed by subharmonic bunchers.

  14. Accurate measurement of the electron beam polarization in JLab Hall A using Compton polarimetry

    International Nuclear Information System (INIS)

    Escoffier, S.; Bertin, P.Y.; Brossard, M.; Burtin, E.; Cavata, C.; Colombel, N.; Jager, C.W. de; Delbart, A.; Lhuillier, D.; Marie, F.; Mitchell, J.; Neyret, D.; Pussieux, T.

    2005-01-01

    A major advance in accurate electron beam polarization measurement has been achieved at Jlab Hall A with a Compton polarimeter based on a Fabry-Perot cavity photon beam amplifier. At an electron energy of 4.6GeV and a beam current of 40μA, a total relative uncertainty of 1.5% is typically achieved within 40min of data taking. Under the same conditions monitoring of the polarization is accurate at a level of 1%. These unprecedented results make Compton polarimetry an essential tool for modern parity-violation experiments, which require very accurate electron beam polarization measurements

  15. Intense source of spin-polarized electrons using laser-induced optical pumping

    International Nuclear Information System (INIS)

    Gray, L.G.; Giberson, K.W.; Cheng, C.; Keiffer, R.S.; Dunning, F.B.; Walters, G.K.

    1983-01-01

    A source of spin-polarized electrons based on a laser-pumped flowing helium afterglow is described. He(2 3 S) atoms contained in the afterglow are optically pumped using circularly polarized 1.08-μm (2 3 S→2 3 P) radiation provided by a NaF (F 2+ )( color-center laser. Spin angular momentum conservation in subsequent chemi-ionization reactions with CO 2 produces polarized electrons that are extracted from the afterglow. At low currents, < or approx. =1 μA, polarizations of approx.70%--80% are achieved. At higher currents the polarization decreases, falling to approx.40% at 50 μA. The spin polarization can be simply reversed (P→-P) and the source is suitable for use in the majority of low-energy spin-dependent scattering experiments proposed to date

  16. The HERMES polarized hydrogen and deuterium gas target in the HERA electron storage ring

    International Nuclear Information System (INIS)

    Airapetian, A.; Akopov, N.; Akopov, Z.

    2005-01-01

    The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in use since 1996 with the polarized electron beam of HERA at DESY to study the spin structure of the nucleon. Polarized atoms from a Stern-Gerlach Atomic Beam Source are injected into a storage cell internal to the HERA electron ring. Atoms diffusing from the center of the storage cell into a side tube are analyzed to determine the atomic fraction and the atomic polarizations. The atoms have a nuclear polarization, the axis of which is defined by an external magnetic holding field. The holding field was longitudinal during 1996-2000, and was changed to transverse in 2001. The design of the target is described, the method for analyzing the target polarization is outlined, and the performance of the target in the various running periods is presented

  17. The HERMES polarized hydrogen and deuterium gas target in the HERA electron storage ring

    International Nuclear Information System (INIS)

    Airapetian, A.; Akopov, N.; Akopov, Z.; Peking University, Beijing

    2004-08-01

    The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in use since 1996 with the polarized electron beam of HERA at DESY to study the spin structure of the nucleon. Polarized atoms from a Stern-Gerlach Atomic Beam Source are injected into a storage cell internal to the HERA electron ring. Atoms diffusing from the center of the storage cell into a side tube are analyzed to determine the atomic fraction and the atomic polarizations. The atoms have a nuclear polarization, the axis of which is defined by an external magnetic holding field. The holding field was longitudinal during 1996-2000, and was changed to transverse in 2001. The design of the target is described, the method for analyzing the target polarization is outlined, and the performance of the target in the various running periods is presented. (orig.)

  18. Evaluation of radiative spin polarization in an electron storage ring

    Energy Technology Data Exchange (ETDEWEB)

    Chao, A W [Stanford Linear Accelerator Center, CA (USA)

    1981-02-15

    We have developed a matrix formalism that provides an accurate way of evaluating the degree of spin polarization built up through the process of synchrotron radiation under a wide variety of storage ring operation conditions.

  19. Observation of strongly forbidden solid effect dynamic nuclear polarization transitions via electron-electron double resonance detected NMR

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Albert A.; Corzilius, Björn; Haze, Olesya; Swager, Timothy M.; Griffin, Robert G., E-mail: rgg@mit.edu [Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2013-12-07

    We present electron paramagnetic resonance experiments for which solid effect dynamic nuclear polarization transitions were observed indirectly via polarization loss on the electron. This use of indirect observation allows characterization of the dynamic nuclear polarization (DNP) process close to the electron. Frequency profiles of the electron-detected solid effect obtained using trityl radical showed intense saturation of the electron at the usual solid effect condition, which involves a single electron and nucleus. However, higher order solid effect transitions involving two, three, or four nuclei were also observed with surprising intensity, although these transitions did not lead to bulk nuclear polarization—suggesting that higher order transitions are important primarily in the transfer of polarization to nuclei nearby the electron. Similar results were obtained for the SA-BDPA radical where strong electron-nuclear couplings produced splittings in the spectrum of the indirectly observed solid effect conditions. Observation of high order solid effect transitions supports recent studies of the solid effect, and suggests that a multi-spin solid effect mechanism may play a major role in polarization transfer via DNP.

  20. NMR Probe for Electrons in Semiconductor Mesoscopic Structures

    Indian Academy of Sciences (India)

    2009-11-14

    Nov 14, 2009 ... Strongly correlated electron systems: Overview ... Mutual interaction of electrons dominates their kinetic energies giving rise to ... transport properties. .... Low energy spin-flip excitations of a spin chain with lattice constant 1/n ...

  1. Astronomy in Denver: Probing Interstellar Circular Polarization with Polvis, a Full Stokes Single Shot Polarimeter

    Science.gov (United States)

    Wolfe, Tristan; Stencel, Robert E.

    2018-06-01

    Measurements of optical circular polarization (Stokes V) introduced by dust grains in the ISM are important for two main reasons. First of all, the polarization itself contains information about the metallic versus dielectric composition of the dust grains themselves (H. C. van de Hulst 1957, textbook). Additionally, circular polarization can help constrain the interstellar component of the polarization of any source that may have intrinsic polarization, which needs to be calibrated for astrophysical study. Though interstellar circular polarization has been observed (P. G. Martin 1972, MNRAS 159), most broadband measurements of ISM polarization include linear polarization only (Stokes Q and U), due to the relatively low circular polarization signal and the added instrumentation complexity of including V-measurement capability. Prior circular polarization measurements have also received very little follow-up in the past several decades, even as polarimeters have become more accurate due to advances in technology. The University of Denver is pursuing these studies with POLVIS, a prototype polarimeter that utilizes a stress-engineered optic ("SEO", A. K. Spilman and T. G. Brown 2007, Applied Optics IP 46) to produce polarization-dependent PSFs (A. M. Beckley and T. G. Brown 2010, Proc SPIE 7570). These PSFs are analyzed to provide simultaneous Stokes I, Q, U, and V measurements, in a single beam and single image, along the line-of-sight to point source-like objects. Polvis is the first polarimeter to apply these optics and measurement techniques for astronomical observations. We present the first results of this instrument in B, V, and R wavebands, providing a fresh look at full Stokes interstellar polarization. Importantly, this set of efforts will constrain the ISM contribution to the polarization with respect to intrinsic stellar components. The authors are grateful to the estate of William Herschel Womble for the support of astronomy at the University of Denver

  2. Spin structure function measurements with polarized protons and electrons at HERA

    International Nuclear Information System (INIS)

    Ball, R.D.; Deshpande, A.; Forte, S.; Hughes, V.W.; Lichtenstadt, J.; Ridolfi, G.

    1995-01-01

    Useful insights into the spin structure functions of the nucleon can be achieved by measurements of spin-dependent asymmetries in inclusive scattering of high energy polarized electrons by high energy polarized protons at HERA. Such an experiment would be a natural extension of the polarized lepton-nucleon scattering experiments presently carried out at CERN and SLAC. We present here estimates of possible data in the extended kinematic range of HERA and associated statistical errors. (orig.)

  3. Chemically induced dynamic electron polarization. Pulse radiolysis of aqueous solutions of alcohols

    International Nuclear Information System (INIS)

    Trifunac, A.D.; Thurnauer, M.C.

    1975-01-01

    The radical pair model of chemically induced dynamic electron polarization (CIDEP) is experimentally verified. Aqueous solutions of alcohols were irradiated with 3 MeV electrons and observed with time resolved electron paramagnetic resonance (EPR) spectroscopy. Relative line intensities of the polarized EPR spectra of radicals from methanol and especially ethylene glycol, alone and in the presence of radicals from compounds containing halogens, illustrates the polarization dependence on the g-factor differences between the radical pair components. The observation of the relative polarization enhancement in the various lines of the multiline EPR spectra illustrates the polarization dependence on the hyperfine terms. Intrinsic enhancements are calculated and are shown to be proportional to the observed enhancement, showing that the radical pair model of CIDEP is qualitatively correct

  4. In situ electrical probing and bias-mediated manipulation of dielectric nanotubes in a high-resolution transmission electron microscope

    International Nuclear Information System (INIS)

    Golberg, D.; Mitome, M.; Kurashima, K.; Zhi, C.Y.; Tang, C.C.; Bando, Y.; Lourie, O.

    2006-01-01

    Boron nitride nanotubes filled with magnesium oxides [MgO, MgO 2 ] and/or hydroxide [Mg(OH) 2 ] are electrically probed and delicately manipulated inside a 300 kV JEOL-3000F high-resolution transmission analytical electron microscope equipped with a side-entry 'Nanofactory Instruments' piezoholder. At a low bias the nanotubes demonstrate truly insulating behavior. At a high bias of ±30 V they show reversible breakdown current of several dozens of nA. Under 300 kV electron beam irradiation the nanotubes are positively charged that allows us to perform on-demand manipulation with them through tuning of polarity and/or value of a bias voltage on a gold counterelectrode from -140 to +140 V, owing to the prominent electrostatic nanotube-electrode interactions

  5. Development of a high average current polarized electron source with long cathode operational lifetime

    Energy Technology Data Exchange (ETDEWEB)

    C. K. Sinclair; P. A. Adderley; B. M. Dunham; J. C. Hansknecht; P. Hartmann; M. Poelker; J. S. Price; P. M. Rutt; W. J. Schneider; M. Steigerwald

    2007-02-01

    Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) require highly polarized electron beams, often at high average current. Spin-polarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and have often deteriorated fairly quickly in ultrahigh vacuum even without electron beam delivery. At Jefferson Lab, we have developed a polarized electron source in which the photocathodes degrade exceptionally slowly without electron emission, and in which ion back bombardment is the predominant mechanism limiting the operational lifetime of the cathodes during electron emission. We have reproducibly obtained cathode 1/e dark lifetimes over two years, and 1/e charge density and charge lifetimes during electron beam delivery of over 2?105???C/cm2 and 200 C, respectively. This source is able to support uninterrupted high average current polarized beam delivery to three experimental halls simultaneously for many months at a time. Many of the techniques we report here are directly applicable to the development of GaAs photoemission electron guns to deliver high average current, high brightness unpolarized beams.

  6. Spin-polarized scanning tunneling microscopy with quantitative insights into magnetic probes.

    Science.gov (United States)

    Phark, Soo-Hyon; Sander, Dirk

    2017-01-01

    Spin-polarized scanning tunneling microscopy and spectroscopy (spin-STM/S) have been successfully applied to magnetic characterizations of individual nanostructures. Spin-STM/S is often performed in magnetic fields of up to some Tesla, which may strongly influence the tip state. In spite of the pivotal role of the tip in spin-STM/S, the contribution of the tip to the differential conductance d I /d V signal in an external field has rarely been investigated in detail. In this review, an advanced analysis of spin-STM/S data measured on magnetic nanoislands, which relies on a quantitative magnetic characterization of tips, is discussed. Taking advantage of the uniaxial out-of-plane magnetic anisotropy of Co bilayer nanoisland on Cu(111), in-field spin-STM on this system has enabled a quantitative determination, and thereby, a categorization of the magnetic states of the tips. The resulting in-depth and conclusive analysis of magnetic characterization of the tip opens new venues for a clear-cut sub-nanometer scale spin ordering and spin-dependent electronic structure of the non-collinear magnetic state in bilayer high Fe nanoislands on Cu(111).

  7. Characterizing nanoscale scanning probes using electron microscopy: A novel fixture and a practical guide

    Energy Technology Data Exchange (ETDEWEB)

    Jacobs, Tevis D. B., E-mail: tjacobs@pitt.edu [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 3700 O’Hara St., Pittsburgh, Pennsylvania 15208 (United States); Wabiszewski, Graham E.; Goodman, Alexander J.; Carpick, Robert W., E-mail: carpick@seas.upenn.edu [Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 220 S. 33rd St., Philadelphia, Pennsylvania 19104 (United States)

    2016-01-15

    The nanoscale geometry of probe tips used for atomic force microscopy (AFM) measurements determines the lateral resolution, contributes to the strength of the tip-surface interaction, and can be a significant source of uncertainty in the quantitative analysis of results. While inverse imaging of the probe tip has been used successfully to determine probe tip geometry, direct observation of the tip profile using electron microscopy (EM) confers several advantages: it provides direct (rather than indirect) imaging, requires fewer algorithmic parameters, and does not require bringing the tip into contact with a sample. In the past, EM-based observation of the probe tip has been achieved using ad hoc mounting methods that are constrained by low throughput, the risk of contamination, and repeatability issues. We report on a probe fixture designed for use in a commercial transmission electron microscope that enables repeatable mounting of multiple AFM probes as well as a reference grid for beam alignment. This communication describes the design, fabrication, and advantages of this probe fixture, including full technical drawings for machining. Further, best practices are discussed for repeatable, non-destructive probe imaging. Finally, examples of the fixture’s use are described, including characterization of common commercial AFM probes in their out-of-the-box condition.

  8. Progress in measurement and understanding of beam polarization in electron positron storage rings

    International Nuclear Information System (INIS)

    Barber, D.P.; Bremer, H.D.; Kewisch, J.; Lewin, H.C.; Limberg, T.; Mais, H.; Ripken, G.; Rossmanith, R.; Schmidt, R.

    1983-07-01

    A report is presented on the status of attempts to obtain and measure spin polarization in electron-positron storage rings. Experimental results are presented and their relationship to predictions of calculations discussed. Examples of methods for decoupling orbital and spin motion and thus improving polarization are discussed. (orig.)

  9. Performance of a Polarized Deuterium Internal Target in a Medium-Energy Electron Storage Ring.

    NARCIS (Netherlands)

    Zhou, Z.L.; Ferro Luzzi, M.M.E.; van den Brand, J.F.J.; Bulten, H.J.; Alarcon, R.; van Bommel, R.; Botto, T.; Bouwhuis, M.; Buchholz, M.; Choi, S.; Comfort, J.; Doets, M.; Dolfini, S.; Ent, R.; Gaulard, C.; de Jager, C.W.; Lang, J.; de Lange, D.J.; Miller, M.A.; Passchier, E.; Passchier, I.; Poolman, H.R.; Six, E.; Steijger, J.J.M.; Unal, O.; de Vries, H.

    1996-01-01

    A polarized deuterium target internal to a medium-energy electron storage ring is described in the context of spindependent (e, e′d) and (e ,e′p) experiments. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage cell target. A Breit-Rabi polarimeter was used

  10. Non-perturbative calculation of equilibrium polarization of stored electron beams

    International Nuclear Information System (INIS)

    Yokoya, Kaoru.

    1992-05-01

    Stored electron/positron beams polarize spontaneously owing to the spin-flip synchrotron radiation. In the existing computer codes, the degree of the equilibrium polarization has been calculated using perturbation expansions in terms of the orbital oscillation amplitudes. In this paper a new numerical method is presented which does not employ the perturbation expansion. (author)

  11. The HERA polarimeter and the first observation of electron spin polarization at HERA

    International Nuclear Information System (INIS)

    Barber, D.P.; Bremer, H.D.; Boege, M.; Brinkmann, R.; Gianfelice-Wendt, E.; Kaiser, H.; Klanner, R.; Lewin, H.C.; Meyners, N.; Vogel, W.; Brueckner, W.; Buescher, C.; Dueren, M.; Gaul, H.G.; Muecklich, A.; Neunreither, F.; Rith, K.; Scholz, C.; Steffens, E.; Veltri, M.; Wander, W.; Zapfe, K.; Zetsche, F.; Chapman, M.; Milner, R.; Coulter, K.; Delheij, P.P.J.; Haeusser, O.; Henderson, R.; Levy, P.; Vetterli, M.; Gressmann, H.; Janke, T.; Micheel, B.; Westphal, D.; Kaiser, R.; Losev, L.; Nowak, W.D.

    1992-10-01

    Electron spin polarizations of about 8% were observed at HERA in November 1991. In runs during 1992 utilizing special orbit corrections, polarization values close to 60% have been achieved. In this paper the polarimeter, the machine conditions, the data analysis, the first results and plans for future measurements are described. (orig.)

  12. Nuclear-polarization correction to the bound-electron g factor in heavy hydrogenlike ions

    OpenAIRE

    Nefiodov, A. V.; Plunien, G.; Soff, G.

    2002-01-01

    The influence of nuclear polarization on the bound-electron $g$ factor in heavy hydrogenlike ions is investigated. Numerical calculations are performed for the K- and L-shell electrons taking into account the dominant virtual nuclear excitations. This determines the ultimate limit for tests of QED utilizing measurements of the bound-electron $g$ factor in highly charged ions.

  13. Nuclear-polarization correction to the bound-electron g factor in heavy hydrogenlike ions.

    Science.gov (United States)

    Nefiodov, A V; Plunien, G; Soff, G

    2002-08-19

    The influence of nuclear polarization on the bound-electron g factor in heavy hydrogenlike ions is investigated. Numerical calculations are performed for the K- and L-shell electrons taking into account the dominant virtual nuclear excitations. This determines the ultimate limit for tests of QED utilizing measurements of the bound-electron g factor in highly charged ions.

  14. Surface chemistry and electronic structure of nonpolar and polar GaN films

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Monu; Krishna, T.C. Shibin; Aggarwal, Neha; Gupta, Govind, E-mail: govind@nplindia.org

    2015-08-01

    Highlights: • Surface chemistry and electronic structure of polar and nonpolar GaN is reported. • Influence of polarization on electron affinity of p & np GaN films is investigated. • Correlation between surface morphology and polarity has been deduced. - Abstract: Photoemission and microscopic analysis of nonpolar (a-GaN/r-Sapphire) and polar (c-GaN/c-Sapphire) epitaxial gallium nitride (GaN) films grown via RF-Molecular Beam Epitaxy is reported. The effect of polarization on surface properties like surface states, electronic structure, chemical bonding and morphology has been investigated and correlated. It was observed that polarization lead to shifts in core level (CL) as well as valence band (VB) spectra. Angle dependent X-ray Photoelectron Spectroscopic analysis revealed higher surface oxide in polar GaN film compared to nonpolar GaN film. On varying the take off angle (TOA) from 0° to 60°, the Ga−O/Ga−N ratio varied from 0.11–0.23 for nonpolar and 0.17–0.36 for polar GaN film. The nonpolar film exhibited N-face polarity while Ga-face polarity was perceived in polar GaN film due to the inherent polarization effect. Polarization charge compensated surface states were observed on the polar GaN film and resulted in downward band bending. Ultraviolet photoelectron spectroscopic measurements revealed electron affinity and ionization energy of 3.4 ± 0.1 eV and 6.8 ± 0.1 eV for nonpolar GaN film and 3.8 ± 0.1 eV and 7.2 ± 0.1 eV for polar GaN film respectively. Field Emission Scanning Electron Microscopy measurements divulged smooth morphology with pits on polar GaN film. The nonpolar film on the other hand showed pyramidal structures having facets all over the surface.

  15. Current-induced spin polarization in a spin-polarized two-dimensional electron gas with spin-orbit coupling

    International Nuclear Information System (INIS)

    Wang, C.M.; Pang, M.Q.; Liu, S.Y.; Lei, X.L.

    2010-01-01

    The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.

  16. Precision gamma-ray polarimetry applied to studies of bremsstrahlung produced by polarized electrons

    Energy Technology Data Exchange (ETDEWEB)

    Kovtun, Oleksiy

    2015-12-16

    The thesis reports on the measurement of bremsstrahlung linear polarization produced in collisions of longitudinally and transversely polarized electrons with gold atoms. The experiment was performed at the Mainzer Microtron MAMI in the Institut fuer Kernphysik of Johannes Gutenberg-Universitaet Mainz, Germany. Spin-oriented electrons with 2.15 MeV kinetic energy collided with a thin golden target and produced bremsstrahlung. Linear polarization of the emitted photons was measured by means of Compton polarimetry applied to a segmented high-purity germanium detector. Experimental results reveal a strong correlation between the electron spin orientation and bremsstrahlung linear polarization. This indicates a dominant role of the electron spin in atomic-field bremsstrahlung and Coulomb scattering.

  17. Status report of the S-DALINAC polarized electron injector SPIN at Darmstadt

    Energy Technology Data Exchange (ETDEWEB)

    Eckardt, Christian; Bahlo, Thore; Bangert, Phillip; Barday, Roman; Bonnes, Uwe; Brunken, Marco; Eichhorn, Ralf; Enders, Joachim; Platz, Markus; Poltoratska, Yuliya; Roth, Markus; Schneider, Fabian; Wagner, Markus; Weber, Antje; Zwicker, Benjamin [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Ackermann, Wolfgang; Mueller, Wolfgang F.O.; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder, Technische Universitaet Darmstadt (Germany)

    2010-07-01

    At the superconducting 130 MeV Darmstadt electron linac S-DALINAC a source of polarized electrons is being installed. Polarized electrons are produced by photoemission from a negative electron affinity strained superlattice GaAs cathode and preaccelerated to 100 keV. With a Wien filter and Mott polarimeter in the beam line the polarization is manipulated and measured. For beam diagnostics wire scanners, fluorescent screens and a coaxial Faraday cup are included. To measure the beam polarization at higher energies, a 5-10 MeV Mott polarimeter and a 50-130 MeV Moeller polarimeter as well as a Compton transmission polarimeter will be installed. We report on the status of the implementation and show plans for future development and experiments.

  18. Spin physics with polarized electrons at the SLC [Stanford Linear Collider

    International Nuclear Information System (INIS)

    Moffeit, K.C.

    1990-11-01

    The Stanford Linear Collider was designed to accommodate polarized electron beams. A gallium arsenide-based photon emission source will provide a beam of longitudinally polarized electrons of about 40 percent polarization. A system of bend magnets and a superconducting solenoid will be used to rotate the spins so that the polarization is preserved while the 1.21 GeV electrons are stored in the damping ring. Another set of bend magnets and two superconducting solenoids orient the spin vectors so that longitudinal polarization of the electrons is achieved at the collision point with the unpolarized positions. A system to monitor the polarization based on Moeller and Compton scattering will be used. Spin physics with longitudinally polarized electrons uses the measurement of the left-right asymmetry to provide tests of the Standard Model. The uncertainty in the measurement is precise enough to be sensitive to the effects of particles which can not be produced directly in the machines we have today. 5 refs

  19. 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.

  20. Permanent and induced dipole requirements in ab initio calculations of electron affinities of polar molecules

    International Nuclear Information System (INIS)

    Garrett, W.R.

    1979-01-01

    Through the use of a molecular pseudopotential method, we determine the a approximate magnitudes of errors that result when electron affinity determinations of polar negative ions are made through ab initio calculations in which the use of a given basis set yields inappropriate values for permanent and induced dipole moments of the neutral molecule. These results should prove useful in assessing the adequacy of basis sets in ab initio calculations of molecular electron affinities for simple linear polar molecules

  1. Observation of electron polarization above 80% in photoemission from strained III-V compounds

    International Nuclear Information System (INIS)

    Garwin, E.L.; Maruyama, T.; Prepost, R.; Zapalac, G.H.

    1992-02-01

    Spin-polarized electron photoemission has been investigated for strained III--V compounds; (1) strained In x Ga 1-x As epitaxially grown on a GaAs substrate, and (2) strained GaAs grown on a GaAs 1-x P x buffer layer. The lattice mismatched heterostructure results in a highly strained epitaxial layer, and electron spin polarization as high as 90% has been observed

  2. MAGNETIC STRUCTURES IN GAMMA-RAY BURST JETS PROBED BY GAMMA-RAY POLARIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Yonetoku, Daisuke; Murakami, Toshio; Morihara, Yoshiyuki; Takahashi, Takuya; Wakashima, Yudai; Yonemochi, Hajime; Sakashita, Tomonori; Fujimoto, Hirofumi; Kodama, Yoshiki [College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192 (Japan); Gunji, Shuichi; Toukairin, Noriyuki [Department of Physics, Faculty of Science, Yamagata University, 1-4-12, Koshirakawa, Yamagata, Yamagata 990-8560 (Japan); Mihara, Tatehiro [Cosmic Radiation Laboratory, RIKEN, 2-1, Hirosawa, Wako City, Saitama 351-0198 (Japan); Toma, Kenji, E-mail: yonetoku@astro.s.kanazawa-u.ac.jp [Department of Earth and Space Science, Osaka University, Toyonaka 560-0043 (Japan)

    2012-10-10

    We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB 110301A and GRB 110721A, observed with the gamma-ray burst polarimeter (GAP) on borad the IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of {Pi} = 70 {+-} 22% with statistical significance of 3.7{sigma} for GRB 110301A, and {Pi} = 84{sup +16}{sub -28}% with 3.3{sigma} confidence level for GRB 110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB 100826A, which showed a significant change of polarization angle, as reported in Yonetoku et al. Synchrotron emission model can be consistent with the data of the three GRBs, while the photospheric quasi-thermal emission model is not favored. We suggest that magnetic field structures in the emission region are globally ordered fields advected from the central engine.

  3. Characterization of microenvironment polarity and solvent accessibility of polysilsesquioxane xerogels by the fluorescent probe technique

    Energy Technology Data Exchange (ETDEWEB)

    Shea, K.J.; Zhu, H.D. [Univ., of California, Irvine, CA (United States). Dept. of Chemistry; Loy, D.A. [Sandia National Labs., Albuquerque, NM (United States)

    1995-05-01

    Poly (1, 4 bis(triethoxysilyl)benzene) (PTESB), a representative of a new type of organic-inorganic hybrid polysilsesquioxane material, was characterized by fluorescence spectroscopy for both microenvironmental polarity and solvent accessibility. A dansyl fluorescent molecule was incorporated into the bulk as well as onto the surface of both PTESB and silica materials. Information about the microenvironment polarity and accessibility of PTESB to various organic solvents was determined and compared to that of silica gel. This study found that both the bulk and surface of PTESB are less polar than that of the silica material. The silica material is accessible to polar solvents and water, while YMB is accessible to polar solvents but not to water. The hydrophobicity of PTESB differentiates these new materials from silica gel.

  4. Probing the Accretion Geometry of Black Holes with X-Ray Polarization

    Science.gov (United States)

    Schnitman, Jeremy D.

    2011-01-01

    In the coming years, new space missions will be able to measure X-ray polarization at levels of 1% or better in the approx.1-10 keV energy band. In particular, X-ray polarization is an ideal tool for determining the nature of black hole (BH) accretion disks surrounded by hot coronae. Using a Monte Carlo radiation transport code in full general relativity, we calculate the spectra and polarization features of these BH systems. At low energies, the signal is dominated by the thermal flux coming directly from the optically thick disk. At higher energies, the thermal seed photons have been inverse-Compton scattered by the corona, often reflecting back off the disk before reaching the observer, giving a distinctive polarization signature. By measuring the degree and angle of this X-ray polarization, we can infer the BH inclination, the emission geometry of the accretion flow, and also determine the spin of the black hole.

  5. Probing Novel Properties of Nucleons and Nuclei via Parity Violating Electron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mercado, Luis [Univ. of Massachusetts, Amherst, MA (United States)

    2012-05-01

    This thesis reports on two experiments conducted by the HAPPEx (Hall A Proton Parity Experiment) collaboration at the Thomas Jefferson National Accelerator Facility. For both, the weak neutral current interaction (WNC, mediated by the Z0 boson) is used to probe novel properties of hadronic targets. The WNC interaction amplitude is extracted by measuring the parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons o unpolarized target hadrons. HAPPEx-III, conducted in the Fall of 2009, used a liquid hydrogen target at a momentum transfer of Q2 = 0.62 GeV2. The measured asymmetry was used to set new constraints on the contribution of strange quark form factors (GsE,M ) to the nucleon electromagnetic form factors. A value of APV = -23.803±} 0.778 (stat)± 0.359 (syst) ppm resulted in GsE + 0.517GsM = 0.003± 0.010 (stat)± 0.004 (syst)± 0.009 (FF). PREx, conducted in the Spring of 2010, used a polarized electron beam on a 208Pb target at a momentum transfer of Q2 = 0.009 GeV2. This parity-violating asymmetry can be used to obtain a clean measurement of the root-mean-square radius of the neutrons in the 208Pb nucleus. The Z0 boson couples mainly to neutrons; the neutron weak charge is much larger than that of the proton. The value of this asymmetry is at the sub-ppm level and has a projected experimental fractional precision of 3%. We will describe the accelerator setup used to set controls on helicity-correlated beam asymmetries and the analysis methods for finding the raw asymmetry for HAPPEx-III. We will also discuss in some detail the preparations to meet the experimental challenges associated with measuring such a small asymmetry with the degree of precision required for PREx.

  6. Coherent polarization radiation of relativistic electrons in crystals

    International Nuclear Information System (INIS)

    Morokhovskii, V.L.

    2014-01-01

    A brief narration about the history of those heated arguments and discussions around the nature of so-called parametric X-radiation, which were concluded by the recognition of the discovery the phenomenon of coherent polarization bremsstrahlung of relativistic charged particles in crystals. Some important information and comments, which stay over of notice of specialists till now are reported.

  7. Polarization asymmetries in photoproduction of electron-positron pairs

    International Nuclear Information System (INIS)

    Vescan, T.

    1980-01-01

    The inclusive reaction γN→e + e - + ... is examined taking into account the polarization of the photon, nucleon and leptons. The results apply also to the exclusive reaction γN→e + e - N by taking the elastic limit of the structure functions. (author)

  8. Radiative corrections to chargino production in electron-positron collisions with polarized beams

    International Nuclear Information System (INIS)

    Diaz, Marco A.; King, Stephen F.; Ross, Douglas A.

    2001-01-01

    We study radiative corrections to chargino production at linear colliders with polarized electron beams. We calculate the one-loop corrected cross sections for polarized electon beams due to three families of quarks and squarks, working in the {ovr MS} scheme, extending our previous calculation of the unpolarized cross section with one-loop corrections due to the third family of quarks and squarks. In some cases we find rather large corrections to the tree-level cross sections. For example, for the case of right-handed polarized electrons and large tanβ the corrections can be of order 30%, allowing sensitivity to the squark mass parameters

  9. Anomalous property of coherent bremsstrahlung linear polarization of relativistic electrons in a crystal

    International Nuclear Information System (INIS)

    Lapko, V.P.; Nasonov, N.N.; Truten', V.I.

    1993-01-01

    Polarization and spectral-and-angular properties of γ-radiation of the relativistic electron flux moving in a crystal under uncorrelated collisions with crystal atomic chains, are studied theoretically. Direction of linear polarization of radiation is shown to vary with energy of emitted photon. Reasons of occurrence of this effect are discussed. The results of numerical calculations demonstrating the possibility to form an intensive source of polarized γ-quanta on the basis of coherent radiation of relativistic electrons during low-angular scattering at crystal atom chains, are given

  10. Polarization effects in radiative recombination of an electron with a highly charged ion

    International Nuclear Information System (INIS)

    Klasnikov, A.E.; Shabaev, V.M.; Artemyev, A.N.; Kovtun, A.V.; Stoehlker, T.

    2005-01-01

    The radiative recombination of an unpolarized electron with a polarized highly charged H-like ion in its ground state is studied. The absolute and relative values of the electron spin-flip contribution to the cross section of the process for various scattering angles and photon polarizations are calculated. It is shown that, in addition to the forward and backward directions, there are some other scattering angles of the emitted photon, where, at a fixed linear photon polarization, the spin-flip transition gives a dominant contribution to the differential cross section

  11. The effects of electron spiraling on the anisotropy and polarization of photon emission from an electron beam ion trap

    International Nuclear Information System (INIS)

    Savin, D.W.; Gu, M.F.; Beiersdorfer, P.

    1998-01-01

    We present a theoretical formalism for calculating the anisotropy and polarization of photon emission due to a spiraling beam of electrons in an electron beam ion trap (EBIT). We present measurements of the polarization for the Fe XXIV 4p 2 P 3/2 → 2s 2 S 1/2 X-ray transition due to electron impact excitation. We discuss these results, together with previously reported EBIT polarization measurements, in the light of electron spiraling. We find that spiraling effects cannot yet be discerned in these measurements. This is important for many EBIT measurements concerned with X-ray line intensity measurements. While the amount of spiraling is not accurately known, neglecting its effects introduces an error typically no larger than that given by counting statistics. (author)

  12. N-polar GaN epitaxy and high electron mobility transistors

    International Nuclear Information System (INIS)

    Wong, Man Hoi; Keller, Stacia; Dasgupta, Nidhi Sansaptak; Denninghoff, Daniel J; Kolluri, Seshadri; Brown, David F; Lu, Jing; Fichtenbaum, Nicholas A; Ahmadi, Elaheh; DenBaars, Steven P; Speck, James S; Mishra, Umesh K; Singisetti, Uttam; Chini, Alessandro; Rajan, Siddharth

    2013-01-01

    This paper reviews the progress of N-polar (0001-bar) GaN high frequency electronics that aims at addressing the device scaling challenges faced by GaN high electron mobility transistors (HEMTs) for radio-frequency and mixed-signal applications. Device quality (Al, In, Ga)N materials for N-polar heterostructures are developed using molecular beam epitaxy and metalorganic chemical vapor deposition. The principles of polarization engineering for designing N-polar HEMT structures will be outlined. The performance, scaling behavior and challenges of microwave power devices as well as highly-scaled depletion- and enhancement-mode devices employing advanced technologies including self-aligned processes, n+ (In,Ga)N ohmic contact regrowth and high aspect ratio T-gates will be discussed. Recent research results on integrating N-polar GaN with Si for prospective novel applications will also be summarized. (invited review)

  13. DMSP optical and electron measurements in the vicinity of polar cap arcs

    International Nuclear Information System (INIS)

    Hardy, D.A.; Burke, W.J.; Gussenhoven, M.S.

    1982-01-01

    We have completed an extensive analysis of the electron and optical data from the DMSP satellites for an external period of polar cap arc occurrences on December 12, 1977. The polar cap arcs are observed in three distinct intervals in a period of quieting after a time of intense substorm activity. The observation of polar cap arcs is associated with the admittance of large and variable fluxes of low-energy electrons into a major portion of both the northern and southern hemisphere polar caps. These fluxes fall into the following categories: First, nearly Maxwellian distributions of electrons with temperatures between 50 eV and 200 eV and number densities varying from 0.03/cm 3 to 4/cm 3 . The highest densities are found at the poleward boundary of the diffuse aurorae and near the visible polar cap arcs. The lowest densities are associated with the polar rain. Second, distributions of electrons peaked between 50 eV and 200 eV. These distributions result from accelertion of the cold Maxwellian distribution through a potential of 50 to 200 V without any heating of the electrons. Third, distributions of electrons displaying two populations; an intense low-energy component with a temperature of approx.20 eV and a much weaker high-energy component with a temperature of 180 eV. We interpret such distributions as evidence of direct admittance of magnetosheath electrons into the polar cap. Fourth,, distributions of electrons peaked at approx.1 keV. These distributions produce the visible arcs. They result from the acceleration of a two-component electron population with temperatures of 100 and 350 eV through a potential drop of approx.750 V

  14. Electron ring diagnostics with magnetic probes during roll-out and acceleration

    International Nuclear Information System (INIS)

    Schumacher, U.; Ulrich, M.

    1976-03-01

    Different methods using magnetic field probes to determine the properties of electron rings during their compression, roll-out and acceleration are presented. The results of the measurements of the electron number and the axial velocity and acceleration of the rings, as obtained with the various diagnostic devices, are discussed and compared. (orig.) [de

  15. Electron-spin polarization in tunnel junctions with ferromagnetic EuS barriers

    International Nuclear Information System (INIS)

    Hao, X.; Moodera, J.S.; Meservey, R.

    1989-01-01

    The authors report here spin-polarized tunneling experiments using non-ferromagnetic electrodes and ferromagnetic EuS barriers. Because of the conduction band in EuS splits into spin-up and spin-down subbands when the temperature is below 16.7 K, the Curie temperature of EuS, the tunnel barrier for electrons with different spin directions is different, therefore giving rise to tunnel current polarization. The spin-filter effect, as it may be called, was observed earlier, directly or indirectly, by several groups: Esaki et al. made a tunneling study on junctions having EuS and EuSe barriers; Thompson et al. studied Schottky barrier tunneling between In and doped EuS; Muller et al. and Kisker et al. performed electron field emission experiments on EuS-coated tungsten tips. The field emission experiments gave a maximum polarization of (89 + 7)% for the emitted electrons. Although the previous tunneling studies did not directly show electron polarization, their results were explained by the same spin- filter effect. This work uses the spin-polarized tunneling technique to show directly that tunnel current is indeed polarized and polarization can be as high as 85%

  16. Measurement of electron beam polarization produced by photoemission from bulk GaAs using twisted light

    Science.gov (United States)

    Clayburn, Nathan; Dreiling, Joan; McCarter, James; Ryan, Dominic; Poelker, Matt; Gay, Timothy

    2012-06-01

    GaAs photocathodes produce spin polarized electron beams when illuminated with circularly polarized light with photon energy approximately equal to the bandgap energy [1, 2]. A typical polarization value obtained with bulk GaAs and conventional circularly polarized light is 35%. This study investigated the spin polarization of electron beams emitted from GaAs illuminated with ``twisted light,'' an expression that describes a beam of light having orbital angular momentum (OAM). In the experiment, 790nm laser light was focused to a near diffraction-limited spot size on the surface of the GaAs photocathode to determine if OAM might couple to valence band electron spin mediated by the GaAs lattice. Our polarization measurements using a compact retarding-field micro-Mott polarimeter [3] have established an upper bound on the polarization of the emitted electron beam of 2.5%. [4pt] [1] D.T. Pierce, F. Meier, P. Zurcher, Appl. Phys. Lett. 26 670 (1975).[0pt] [2] C.K. Sinclair, et al., PRSTAB 10 023501 (2007).[0pt] [3] J.L. McCarter, M.L. Stutzman, K.W. Trantham, T.G. Anderson, A.M. Cook, and T.J. Gay Nucl. Instrum. and Meth. A (2010).

  17. Reconstruction of the electron energy distribution function from probe characteristics at intermediate and high pressures

    International Nuclear Information System (INIS)

    Arslanbekov, R.R.; Kolokolov, N.B.; Kudryavtsev, A.A.; Khromov, N.A.

    1991-01-01

    Gorbunov et al. have developed a kinetic theory of the electron current drawn by a probe, which substantially extends the region of applicability of the probe method for determining the electron energy distribution function, enabling probes to be used for intermediate and high pressures (up to p ≤ 0.5 atm for monatomic gases). They showed that for λ var-epsilon >> a + d (where a is the probe radius, d is the sheath thickness, and λ var-epsilon is the electron energy relaxation length) the current density j e (V) drawn by the probe is related to the unperturbed distribution function by an integral equation involving the distribution function. The kernal of the integral equation can be written as a function of the diffusion parameter. In the present paper the method of quadrature sums is employed in order to obtain the electron energy distribution function from probe characteristics at intermediate and high pressures. This technique enables them to recover the distribution function from the integral equation when the diffusion parameter has an arbitrary energy dependence ψ 0 (var-epsilon) in any given energy range. The effectiveness of the method is demonstrated by application to both model problems and experimental data

  18. The Role of polarized positrons and electrons in revealing fundamental interactions at the linear collider

    CERN Document Server

    Moortgat-Pick, G.; Alexander, G.; Ananthanarayan, B.; Babich, A.A.; Bharadwaj, V.; Barber, D.; Bartl, A.; Brachmann, A.; Chen, S.; Clarke, J.; Clendenin, J.E.; Dainton, J.; Desch, K.; Diehl, M.; Dobos, B.; Dorland, Tyler McMillan; Dreiner, H.K.; Eberl, H.; Ellis, John R.; Flottmann, K.; Fraas, H.; Franco-Sollova, F.; Franke, F.; Freitas, A.; Goodson, J.; Gray, J.; Han, A.; Heinemeyer, S.; Hesselbach, S.; Hirose, T.; Hohenwarter-Sodek, K.; Juste, A.; Kalinowski, J.; Kernreiter, T.; Kittel, O.; Kraml, S.; Langenfeld, U.; Majerotto, W.; Martinez, A.; Martyn, H.U.; Mikhailichenko, A.; Milstene, C.; Menges, W.; Meyners, N.; Monig, K.; Moffeit, K.; Moretti, S.; Nachtmann, O.; Nagel, F.; Nakanishi, T.; Nauenberg, U.; Nowak, H.; Omori, T.; Osland, P.; Pankov, A.A.; Paver, N.; Pitthan, R.; Poschl, R.; Porod, W.; Proulx, J.; Richardson, P.; Riemann, S.; Rindani, S.D.; Rizzo, T.G.; Schalicke, A.; Schuler, P.; Schwanenberger, C.; Scott, D.; Sheppard, J.; Singh, R.K.; Sopczak, A.; Spiesberger, H.; Stahl, A.; Steiner, H.; Wagner, A.; Weber, A.M.; Weiglein, G.; Wilson, G.W.; Woods, M.; Zerwas, P.; Zhang, J.; Zomer, F.

    2008-01-01

    The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

  19. The Role of polarized positrons and electrons in revealing fundamental interactions at the linear collider

    Energy Technology Data Exchange (ETDEWEB)

    Moortgat-Pick, G.; /CERN /Durham U., IPPP; Abe, T.; Alexander, G.; Ananthanarayan, B.; Babich, A.A.; Bharadwaj, V.; Barber, D.; Bartl, A.; Brachmann, A.; Chen, S.; Clarke,; Clendenin, J.E.; Dainton, J.; Desch, K.; Diehl, M.; Dobos, B.; Dorland, T.; Eberl, H.; Ellis, John R.; Flottman, K.; Frass, H.; /CERN /Durham U., IPPP /Colorado U. /Tel-Aviv

    2005-07-01

    The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

  20. Revealing Fundamental Interactions: the Role of Polarized Positrons and Electrons at the Linear Collider

    Energy Technology Data Exchange (ETDEWEB)

    Moortgat-Pick, G.; /CERN /Durham U., IPPP; Abe, T.; Alexander, G.; Ananthanarayan, B.; Babich, A.A.; Bharadwaj, V.; Barber, D.; Bartl, A.; Brachmann, A.; Chen, S.; Clarke,; Clendenin, J.E.; Dainton, J.; Desch, K.; Diehl, M.; Dobos, B.; Dorland, T.; Eberl, H.; Ellis, John R.; Flottman, K.; Frass, H.; /CERN /Durham U., IPPP /Colorado U. /Tel-Aviv

    2005-07-06

    The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

  1. Revealing Fundamental Interactions: the Role of Polarized Positrons and Electrons at the Linear Collider

    International Nuclear Information System (INIS)

    Moortgat-Pick, G.; CERN, Durham U. IPPP; Abe, T.; Alexander, G.; Ananthanarayan, B.; Babich, A.A.; Bharadwaj, V.; Barber, D.; Bartl, A.; Brachmann, A.; Chen, S.; Clarke, J.; Clendenin, J.E.; Dainton, J.; Desch, K.; Diehl, M.; Dobos, B.; Dorland, T.; Eberl, H.; Ellis, John R.; Flottman, K.; Frass, H.

    2005-01-01

    The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization

  2. Simulation of Probe Position-Dependent Electron Energy-Loss Fine Structure

    Energy Technology Data Exchange (ETDEWEB)

    Oxley, M. P.; Kapetanakis, M. D.; Prange, Micah P.; Varela, M.; Pennycook, Stephen J.; Pantelides, Sokrates T.

    2014-03-31

    We present a theoretical framework for calculating probe-position-dependent electron energy-loss near-edge structure for the scanning transmission electron microscope by combining density functional theory with dynamical scattering theory. We show how simpler approaches to calculating near-edge structure fail to include the fundamental physics needed to understand the evolution of near-edge structure as a function of probe position and investigate the dependence of near-edge structure on probe size. It is within this framework that density functional theory should be presented, in order to ensure that variations of near-edge structure are truly due to local electronic structure and how much from the diffraction and focusing of the electron beam.

  3. Polarization as a probe to the production mechanisms of charmonium in πN collisions

    International Nuclear Information System (INIS)

    Tang, W.K.; Brodsky, S.J.; Vaenttinen, M.; Hoyer, P.

    1994-07-01

    Measurements of the polarization of J/ψ produced in pion-nucleus collisions are in disagreement with leading twist QCD prediction where J/ψ is observed to have negligible polarization whereas theory predicts substantial polarization. The authors argue that this discrepancy cannot be due to poorly known structure functions nor the relative production rates of J/ψ and χ j . The disagreement between theory and experiment suggests important higher twist corrections, as has earlier been surmised from the anomalous non-factorized nuclear A-dependence of the J/ψ cross section

  4. PHIPS-HALO: the airborne particle habit imaging and polar scattering probe - Part 2: Characterization and first results

    Science.gov (United States)

    Schnaiter, Martin; Järvinen, Emma; Abdelmonem, Ahmed; Leisner, Thomas

    2018-01-01

    The novel aircraft optical cloud probe PHIPS-HALO has been developed to establish clarity regarding the fundamental link between the microphysical properties of single atmospheric ice particles and their appropriated angular light scattering function. After final improvements were implemented in the polar nephelometer part and the acquisition software of PHIPS-HALO, the instrument was comprehensively characterized in the laboratory and was deployed in two aircraft missions targeting cirrus and Arctic mixed-phase clouds. This work demonstrates the proper function of the instrument under aircraft conditions and highlights the uniqueness, quality, and limitations of the data that can be expected from PHIPS-HALO in cloud-related aircraft missions.

  5. On measurement of top polarization as a probe of $t \\bar t$ production mechanisms at the LHC

    CERN Document Server

    Godbole, Rohini M; Rindani, Saurabh D; Singh, Ritesh K

    2010-01-01

    In this note we demonstrate the use of top polarization in the study of $t \\bar t$ resonances at the LHC, in the possible case where the dynamics implies a non-zero top polarization. As a probe of top polarization we construct an asymmetry in the decay-lepton azimuthal angle distribution (corresponding to the sign of $\\cos\\phi_\\ell$) in the laboratory. The asymmetry is non-vanishing even for a symmetric collider like the LHC, where a positive $z$ axis is not uniquely defined. The angular distribution of the leptons has the advantage of being a faithful top-spin analyzer, unaffected by possible anomalous $tbW$ couplings, to linear order. We study, for purposes of demonstration, the case of a $Z'$ as might exist in the little Higgs models. We identify kinematic cuts which ensure that our asymmetry reflects the polarization in sign and magnitude. We investigate possibilities at the LHC with two energy options: $\\sqrt{s} = 14$ TeV and $\\sqrt{s} = 7$ TeV, as well as at the Tevatron. At the LHC the model predicts n...

  6. Creating intense polarized electron beam via laser stripping and spin-orbit interaction

    International Nuclear Information System (INIS)

    Danilov, V.; Ptitsyn, V.; Gorlov, T.

    2010-01-01

    The recent advance in laser field make it possible to excite and strip electrons with definite spin from hydrogen atoms. The sources of hydrogen atoms with orders of magnitude higher currents (than that of the conventional polarized electron cathods) can be obtained from H - sources with good monochromatization. With one electron of H - stripped by a laser, the remained electron is excited to upper state (2P 3/2 and 2P 1/2 ) by a circular polarization laser light from FEL. Then, it is excited to a high quantum number (n=7) with mostly one spin direction due to energy level split of the states with a definite direction of spin and angular momentum in an applied magnetic field and then it is stripped by a strong electric field of an RF cavity. This paper presents combination of lasers and fields to get high polarization and high current electron source.

  7. Probing the ionization wave packet and recollision dynamics with an elliptically polarized strong laser field in the nondipole regime

    Science.gov (United States)

    Maurer, J.; Willenberg, B.; Daněk, J.; Mayer, B. W.; Phillips, C. R.; Gallmann, L.; Klaiber, M.; Hatsagortsyan, K. Z.; Keitel, C. H.; Keller, U.

    2018-01-01

    We explore ionization and rescattering in strong mid-infrared laser fields in the nondipole regime over the full range of polarization ellipticity. In three-dimensional photoelectron momentum distributions (3D PMDs) measured with velocity map imaging spectroscopy, we observe the appearance of a sharp ridge structure along the major polarization axis. Within a certain range of ellipticity, the electrons in this ridge are clearly separated from the two lobes that commonly appear in the PMD with elliptically polarized laser fields. In contrast to the well-known lobes of direct electrons, the sharp ridge is created by Coulomb focusing of the softly recolliding electrons. These ridge electrons are directly related to a counterintuitive shift of the PMD peak opposite to the laser beam propagation direction when the dipole approximation breaks down. The ellipticity-dependent 3D PMDs give access to different ionization and recollision dynamics with appropriate filters in the momentum space. For example, we can extract information about the spread of the initial wave packet and the Coulomb momentum transfer of the rescattering electrons.

  8. CP-even and CP-odd transverse polarization of the electron in muon decay

    International Nuclear Information System (INIS)

    Kuznetsov, A.

    1981-01-01

    A model of the weak interaction which contains intermediate vector bosons of the most general form and which admits CP violation in muon decay is used to calculate the CP-even and CP-odd transverse polarization of the μ-decay electrons with inclusion of radiative corrections. It is shown that these corrections are important only at the beginning of the spectrum, and their contribution reduces the observed effects of the transverse polarization. The transverse polarization grows appreciably at electron energies close to the maximum energy and at small emission angles. It is expedient to search for the CP-even and CP-odd transverse polarization of the electrons at energies E/sub e/ = 0.975E/sup max//sub e/ and emission angles theta = 25--35 0

  9. CP-even and CP-odd transverse polarization of the electron in the muon decay

    International Nuclear Information System (INIS)

    Kuznetsov, A.V.

    1981-01-01

    In the most general weak interaction model with intermediate vector bosons, allowing CP breaking in the muon decay, CP- even and CP-odd transverse polarization of the μ-decay electrons is calculated taking into account the radiative corrections. It is shown that such corrections are essential only at the beginning of the spectrum reducing the observed transverse polarization effects. When the electron energy is close to its maximum and the emission angles are small, the transverse polarization considerably grows. Search for CP-even and CP-odd transverse polarization of the electrons should be carried out at energies Esub(e) approximately equal to O.975 Esub(e)sup(max) and emission angles THETA approximately equal to 25+35 deg [ru

  10. Searches for the Anomalous FCNC Top-Higgs Couplings with Polarized Electron Beam at the LHeC

    Directory of Open Access Journals (Sweden)

    XiaoJuan Wang

    2017-01-01

    Full Text Available We study the single top and Higgs associated production e-p→νet-→νehq-(h→bb- in the top-Higgs FCNC couplings at the LHeC with the electron beam energy of Ee=60 GeV and Ee=120 GeV and combination of a 7 TeV and 50 TeV proton beam. With the possibility of e-beam polarization (pe=0, ±0.6, we distinct the cut-based method and the multivariate analysis- (MVA- based method and compare with the current experimental and theoretical limits. It is shown that the branching ratio Br(t→uh can be probed to 0.113 (0.093%, 0.071 (0.057%, 0.030 (0.022%, and 0.024 (0.019% with the cut-based (MVA-based analysis at (Ep, Ee = (7 TeV, 60 GeV, (Ep, Ee = (7 TeV, 120 GeV, (Ep, Ee = (50 TeV, 60 GeV, and (Ep, Ee = (50 TeV, 120 GeV beam energy and 1σ level. With the possibility of e-beam polarization, the expected limits can be probed down to 0.090 (0.073%, 0.056 (0.045%, 0.024 (0.018%, and 0.019 (0.015%, respectively.

  11. Probing membrane protein structure using water polarization transfer solid-state NMR.

    Science.gov (United States)

    Williams, Jonathan K; Hong, Mei

    2014-10-01

    Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected (1)H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane domain of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins. Copyright © 2014 Elsevier Inc. All

  12. LHCb: Probing photon polarization in Bs->phi gamma decay at LHCb

    CERN Multimedia

    Shchutska, L

    2008-01-01

    The radiative decay Bs->phi gamma is one of the benchmark channels in the physics programme of the LHCb experiment. It provides the possibility to test the Standard Model through the indirect measurement of the photon polarization in b->s gamma transition. The statistical uncertainty in the wrong polarization fraction of photons is estimated to be ~0.2 with the 2 fb^{-1} of integrated luminosity.

  13. Electron spin polarization in realistic trajectories around the magnetic node of two counter-propagating, circularly polarized, ultra-intense lasers

    Science.gov (United States)

    Del Sorbo, D.; Seipt, D.; Thomas, A. G. R.; Ridgers, C. P.

    2018-06-01

    It has recently been suggested that two counter-propagating, circularly polarized, ultra-intense lasers can induce a strong electron spin polarization at the magnetic node of the electromagnetic field that they setup (Del Sorbo et al 2017 Phys. Rev. A 96 043407). We confirm these results by considering a more sophisticated description that integrates over realistic trajectories. The electron dynamics is weakly affected by the variation of power radiated due to the spin polarization. The degree of spin polarization differs by approximately 5% if considering electrons initially at rest or already in a circular orbit. The instability of trajectories at the magnetic node induces a spin precession associated with the electron migration that establishes an upper temporal limit to the polarization of the electron population of about one laser period.

  14. Spin-polarized electron tunneling across a Si delta-doped GaMnAs/n-GaAs interface

    DEFF Research Database (Denmark)

    Andresen, S.E.; Sørensen, B.S.; Lindelof, P.E.

    2003-01-01

    Spin-polarized electron coupling across a Si delta-doped GaMnAs/n-GaAs interface was investigated. The injection of spin-polarized electrons was detected as circular polarized emission from a GaInAs/GaAs quantum well light emitting diode. The angular momentum selection rules were simplified...

  15. Electron-probe microanalysis: x-ray spectroscopy

    International Nuclear Information System (INIS)

    1987-01-01

    The main principles on X-ray, energy and wave length dispersive spectroscopy are reviewed. In order to allow the choice of the best operating conditions, the importance of the regulation and control systems is underlined. Emission theory, X-rays nature and its interaction with matter and electrons in the matter is shown. The structure, operating procedures and necessary electronics (single channel - analysis chain) automatic-control system for the threshold-energies discrimination and the energy distribution visualization) associated to the wavelength dispersive spectroscopy are described. The focusing control, resolution, influence of chemical bonds and multilayer-structure monochromators relaled to wavelength dispersive spectroscopy are studied. Concerning the energy-dispersive spectroscopy, the detector, preamplifier, amplifier, analog-digital converter, as well as the utilization and control of the spectrometer are described. Problems and instrumental progress on energy-dispersive spectroscopy related to the electronic-noise control, charge collection and light-elements detection are discussed [fr

  16. First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO

    CERN Document Server

    Collin, B; Essabaa, S; Frascaria, R; Gacougnolle, R; Kunne, Ronald Alexander; Aulenbacher, K; Tioukine, V

    2004-01-01

    The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developped a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting decay of the excited states produces the emission of a circularly polarized radiation line at 811.5 nm which is observed and analyzed.

  17. The coupling of condensed matter excitations to electron probes

    International Nuclear Information System (INIS)

    Ritchie, R.H.

    1988-01-01

    Aspects of coupling of a classical electron with bulk and surface excitations in condensed matter have been sketched. Some considerations of a self-energy approach to the complete quantal treatment of this coupling have been given. 19 refs., 3 figs

  18. Polar 5, a Norwegian US electron accelerator sounding rocket

    International Nuclear Information System (INIS)

    Jacobsen, T.A.; Maehlum, B.N.; Troeim, J.

    1976-01-01

    A technical description of a mother daughter experiment including an electron gun is given. The payload was launched by a Nike/Tomahawk rocket from Andenes, North-Norway near 2030 local time on February 1, 1976. A few preliminary observations obtained by the HF-wave propagation experiment, the retarding potential analyzer and the energetic electron counters are be presented

  19. Spin-polarized transport in a two-dimensional electron gas with interdigital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.-M.; Nitta, Junsaku; Jensen, Ane

    2001-01-01

    Ferromagnetic contacts on a high-mobility, two-dimensional electron gas (2DEG) in a narrow gap semiconductor with strong spin-orbit interaction are used to investigate spin-polarized electron transport. We demonstrate the use of magnetized contacts to preferentially inject and detect specific spi...

  20. Structural and electronic properties of polar MnO ultrathin film grown on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Asish K., E-mail: asish.kundu@saha.ac.in; Menon, Krishnakumar S. R. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 70064 (India)

    2016-05-23

    Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

  1. Spin polarization of a magnetic electron gas induced by a van Vleck ion

    International Nuclear Information System (INIS)

    Palermo, L.; Silva, X.A. do

    1978-11-01

    The mutual polarization of a magnetic electron gas and a van Vleck ion, interacting via exchange, are theoretically investigated using the double-time Green function method. A pair of equations describing the dynamics of the electron gas and the ion are conveniently decoupled and an analytic expression for the electron gas polarization, which depends on the square of the exchange parameter, is obtained. Besides a RKKY-like term, a new term associated to the process of formation of the magnetic moment of the ion appears [pt

  2. Minimum detection limit and spatial resolution of thin-sample field-emission electron probe microanalysis

    International Nuclear Information System (INIS)

    Kubo, Yugo; Hamada, Kotaro; Urano, Akira

    2013-01-01

    The minimum detection limit and spatial resolution for a thinned semiconductor sample were determined by electron probe microanalysis (EPMA) using a Schottky field emission (FE) electron gun and wavelength dispersive X-ray spectrometry. Comparison of the FE-EPMA results with those obtained using energy dispersive X-ray spectrometry in conjunction with scanning transmission electron microscopy, confirmed that FE-EPMA is largely superior in terms of detection sensitivity. Thin-sample FE-EPMA is demonstrated as a very effective method for high resolution, high sensitivity analysis in a laboratory environment because a high probe current and high signal-to-noise ratio can be achieved. - Highlights: • Minimum detection limit and spatial resolution determined for FE-EPMA. • Detection sensitivity of FE-EPMA greatly superior to that of STEM-EDX. • Minimum detection limit and spatial resolution controllable by probe current

  3. Circular dichroism measurements at an x-ray free-electron laser with polarization control

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, G.; Shevchuk, I.; Walter, P.; Viefhaus, J. [Deutsches Elektronen-Synchrotron, Notkestraße 85, 22607 Hamburg (Germany); Lindahl, A. O. [PULSE at Stanford, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Knie, A. [Institut für Physik, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Glownia, J. M.; Helml, W.; Huang, Z.; Marinelli, A.; Nuhn, H.-D.; Moeller, S.; Coffee, R. N.; Ilchen, M., E-mail: markus.ilchen@xfel.eu [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Buck, J.; Galler, A.; Liu, J. [European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); and others

    2016-08-15

    A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O{sub 2} 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

  4. Circular dichroism measurements at an x-ray free-electron laser with polarization control

    Science.gov (United States)

    Hartmann, G.; Lindahl, A. O.; Knie, A.; Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Shevchuk, I.; Buck, J.; Galler, A.; Glownia, J. M.; Helml, W.; Huang, Z.; Kabachnik, N. M.; Kazansky, A. K.; Liu, J.; Marinelli, A.; Mazza, T.; Nuhn, H.-D.; Walter, P.; Viefhaus, J.; Meyer, M.; Moeller, S.; Coffee, R. N.; Ilchen, M.

    2016-08-01

    A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O2 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

  5. Probing the positron moderation process using high-intensity, highly polarized slow-positron beams

    Science.gov (United States)

    Van House, J.; Zitzewitz, P. W.

    1984-01-01

    A highly polarized (P = 0.48 + or - 0.02) intense (500,000/sec) beam of 'slow' (Delta E = about 2 eV) positrons (e+) is generated, and it is shown that it is possible to achieve polarization as high as P = 0.69 + or - 0.04 with reduced intensity. The measured polarization of the slow e+ emitted by five different positron moderators showed no dependence on the moderator atomic number (Z). It is concluded that only source positrons with final kinetic energy below 17 keV contribute to the slow-e+ beam, in disagreement with recent yield functions derived from low-energy measurements. Measurements of polarization and yield with absorbers of different Z between the source and moderator show the effects of the energy and angular distributions of the source positrons on P. The depolarization of fast e+ transmitted through high-Z absorbers has been measured. Applications of polarized slow-e+ beams are discussed.

  6. Novel probe for determining the size and position of a relativistic electron beam

    International Nuclear Information System (INIS)

    Orzechowski, T.J.; Koehler, H.; Edwards, W.; Nelson, M.; Marshall, B.

    1984-01-01

    In order to determine the size and position of a relativistic electron beam inside the wiggler magnetic field of a Free Electron Laser (FEL), we have developed a new probe which intercepts the electron beam on a high Z target and monitors the resulting bremsstrahlung radiation. The probe is designed to move along the entire three meters of the wiggler. This FEL is designed to operate in the microwave region (2 to 8 mm) and the interaction region is an oversized waveguide with a cross section 3 cm x 9.8 cm. The axial probe moves inside this waveguide. The probe stops the electron beam on a Tantalum target and the resulting x-rays are scattered in the forward direction. A scintillator behind the beam stop reacts to the x-rays and emits visible light in the region where the x-rays strike. An array of fiber optics behind the scintillator transmits the visible light to a Reticon camera system which images the visible pattern from the scintillator. Processing the optical image is done by digitizing and storing the image and/or recording the image on video tape. Resolution and performance of this probe will be discussed

  7. A new Langmuir probe concept for rapid sampling of space plasma electron density

    International Nuclear Information System (INIS)

    Jacobsen, K S; Pedersen, A; Moen, J I; Bekkeng, T A

    2010-01-01

    In this paper we describe a new Langmuir probe concept that was invented for the in situ investigation of HF radar backscatter irregularities, with the capability to measure absolute electron density at a resolution sufficient to resolve the finest conceivable structure in an ionospheric plasma. The instrument consists of two or more fixed-bias cylindrical Langmuir probes whose radius is small compared to the Debye length. With this configuration, it is possible to acquire absolute electron density measurements independent of electron temperature and rocket/satellite potential. The system was flown on the ICI-2 sounding rocket to investigate the plasma irregularities which cause HF backscatter. It had a sampling rate of more than 5 kHz and successfully measured structures down to the scale of one electron gyro radius. The system can easily be adapted for any ionospheric rocket or satellite, and provides high-quality measurements of electron density at any desired resolution

  8. Laser-polarized noble gases: a powerful probe for biology, medicine, and subatomic physics

    Science.gov (United States)

    Cates, Gordon

    2010-03-01

    For over a decade, laser-polarized noble gases such as ^3He and ^129Xe have proven useful for a wide range of scientific inquiries. These include investigations of pulmonary disease using the polarized gas as a signal source for magnetic resonance imaging (MRI), measurements of various aspects of nucleon structure, and tests of fundamental symmetries. Early efforts were often limited by expensive and bulky laser systems, but ongoing advancements in solid-state lasers have enabled increasingly large volumes of polarized gas to be produced with steadily improved polarization. Equally important have been advances in the fundamental understanding of spin exchange. This has led, for example, to the introduction of hybrid mixtures of alkali metals that can increase the efficiency of spin exchange by an order of magnitude. As a consequence of these advances, the figure of merit for polarized nuclear targets has increased by roughly three orders of magnitude in comparison to early accelerator-based experiments. And in MRI applications, it has become possible to pursue increasingly sophisticated imaging protocols that provide a wide range of diagnostic information. Even the earliest noble-gas MR images of the gas space of the human lung provided unprecedented resolution. More recent work includes the use of diffusion-sensitizing pulse sequences to study lung microstructure, and tagging techniques that enable the visualization (in real-time MRI movies) of gas flow during breathing. The range of applications of laser-polarized noble gases is continuing to grow, and it is notable that with an improved understanding of the underlying physics, it is quite likely that the capabilities of this useful technology will expand for some time to come.

  9. Development of a high average current polarized electron source with long cathode operational lifetime

    Directory of Open Access Journals (Sweden)

    C. K. Sinclair

    2007-02-01

    Full Text Available Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory require highly polarized electron beams, often at high average current. Spin-polarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and have often deteriorated fairly quickly in ultrahigh vacuum even without electron beam delivery. At Jefferson Lab, we have developed a polarized electron source in which the photocathodes degrade exceptionally slowly without electron emission, and in which ion back bombardment is the predominant mechanism limiting the operational lifetime of the cathodes during electron emission. We have reproducibly obtained cathode 1/e dark lifetimes over two years, and 1/e charge density and charge lifetimes during electron beam delivery of over 2×10^{5}   C/cm^{2} and 200 C, respectively. This source is able to support uninterrupted high average current polarized beam delivery to three experimental halls simultaneously for many months at a time. Many of the techniques we report here are directly applicable to the development of GaAs photoemission electron guns to deliver high average current, high brightness unpolarized beams.

  10. Miniaturized Ultrasound Imaging Probes Enabled by CMUT Arrays with Integrated Frontend Electronic Circuits

    Science.gov (United States)

    Khuri-Yakub, B. (Pierre) T.; Oralkan, Ömer; Nikoozadeh, Amin; Wygant, Ira O.; Zhuang, Steve; Gencel, Mustafa; Choe, Jung Woo; Stephens, Douglas N.; de la Rama, Alan; Chen, Peter; Lin, Feng; Dentinger, Aaron; Wildes, Douglas; Thomenius, Kai; Shivkumar, Kalyanam; Mahajan, Aman; Seo, Chi Hyung; O’Donnell, Matthew; Truong, Uyen; Sahn, David J.

    2010-01-01

    Capacitive micromachined ultrasonic transducer (CMUT) arrays are conveniently integrated with frontend integrated circuits either monolithically or in a hybrid multichip form. This integration helps with reducing the number of active data processing channels for 2D arrays. This approach also preserves the signal integrity for arrays with small elements. Therefore CMUT arrays integrated with electronic circuits are most suitable to implement miniaturized probes required for many intravascular, intracardiac, and endoscopic applications. This paper presents examples of miniaturized CMUT probes utilizing 1D, 2D, and ring arrays with integrated electronics. PMID:21097106

  11. Integrated organic electronic based optochemical sensors using polarization filters

    International Nuclear Information System (INIS)

    Kraker, Elke; Haase, Anja; Lamprecht, Bernhard; Jakopic, Georg; Konrad, Christian; Koestler, Stefan

    2008-01-01

    A compact, integrated photoluminescence based oxygen and pH sensor, utilizing an organic light emitting device (OLED) as the light source and an organic photodiode (OPD) as the detection unit, is described. The main challenge in such an integrated sensor is the suppression of the excitation light at the detector, which is typically by many orders of magnitude higher in intensity than the emitted fluorescence. In our approach, we refrain from utilizing edge filters which require narrow band excitation sources and dyes with an adequate large Stokes shift. We rather developed an integrated sensor concept relying on two polarizers to separate the emission and excitation light. One polarizer is located right after the OLED, while the other one, oriented at 90 deg. to the first, is placed in front of the OPD. The main advantage of this solution is that any combination of excitation and emission light is acceptable, even if the two signals overlap spectrally. This is especially important for the use of OLEDs as the excitation sources, as these devices typically exhibit a broad spectral emission

  12. Probing sea quarks and gluons: the electron-ion collider project

    International Nuclear Information System (INIS)

    Horn, T.

    2014-01-01

    A future Electron-Ion Collider (EIC) would be the world's first polarized electron-proton collider, and the world's first e-A collider, and would seek the QCD foundation of nucleons and nuclei in terms of the sea quarks and gluons, matching to these valence quark studies. The EIC will provide a versatile range of kinematics and beam polarization, as well as beam species, to allow for mapping the spin and spatial structure of the quark sea and gluons, to discover the collective effects of gluons in atomic nuclei, and to understand the emergence of hadronic matter from color charge. (authors)

  13. Single electron probes of fractional quantum hall states

    Science.gov (United States)

    Venkatachalam, Vivek

    When electrons are confined to a two dimensional layer with a perpendicular applied magnetic field, such that the ratio of electrons to flux quanta (nu) is a small integer or simple rational value, these electrons condense into remarkable new phases of matter that are strikingly different from the metallic electron gas that exists in the absence of a magnetic field. These phases, called integer or fractional quantum Hall (IQH or FQH) states, appear to be conventional insulators in their bulk, but behave as a dissipationless metal along their edge. Furthermore, electrical measurements of such a system are largely insensitive to the detailed geometry of how the system is contacted or even how large the system is... only the order in which contacts are made appears to matter. This insensitivity to local geometry has since appeared in a number of other two and three dimensional systems, earning them the classification of "topological insulators" and prompting an enormous experimental and theoretical effort to understand their properties and perhaps manipulate these properties to create robust quantum information processors. The focus of this thesis will be two experiments designed to elucidate remarkable properties of the metallic edge and insulating bulk of certain FQH systems. To study such systems, we can use mesoscopic devices known as single electron transistors (SETs). These devices operate by watching single electrons hop into and out of a confining box and into a nearby wire (for measurement). If it is initially unfavorable for an electron to leave the box, it can be made favorable by bringing another charge nearby, modifying the energy of the confined electron and pushing it out of the box and into the nearby wire. In this way, the SET can measure nearby charges. Alternatively, we can heat up the nearby wire to make it easier for electrons to enter and leave the box. In this way, the SET is a sensitive thermometer. First, by operating the SET as an

  14. Lower Hybrid Frequency Range Waves Generated by Ion Polarization Drift Due to Electromagnetic Ion Cyclotron Waves: Analysis of an Event Observed by the Van Allen Probe B

    Science.gov (United States)

    Khazanov, G. V.; Boardsen, S.; Krivorutsky, E. N.; Engebretson, M. J.; Sibeck, D.; Chen, S.; Breneman, A.

    2017-01-01

    We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of approximately 0.86. We assume that the correlation is the result of LHFR wave generation by the ions polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth rates, their frequency distribution, and the frequency dependence of the ratio of the LHFR wave power spectral density (PSD)parallel and perpendicular to the ambient magnetic eld to the total PSD were found. These characteristics of the growth rates were compared with the corresponding characteristics of the observed LHFR activity. Reasonable agreement between these features and the strong correlation between EMIC and LHFR energy densities support the assumption that the LHFR wave generation can be caused by the ions polarization drift in the electric field of an EMIC wave.

  15. A three-dimensional polarization domain retrieval method from electron diffraction data

    International Nuclear Information System (INIS)

    Pennington, Robert S.; Koch, Christoph T.

    2015-01-01

    We present an algorithm for retrieving three-dimensional domains of picometer-scale shifts in atomic positions from electron diffraction data, and apply it to simulations of ferroelectric polarization in BaTiO 3 . Our algorithm successfully and correctly retrieves polarization domains in which the Ti atom positions differ by less than 3 pm (0.4% of the unit cell diagonal distance) with 5 and 10 nm depth resolution along the beam direction, and we also retrieve unit cell strain, corresponding to tetragonal-to-cubic unit cell distortions, for 10 nm domains. Experimental applicability is also discussed. - Highlights: • We show a retrieval method for ferroelectric polarization from TEM diffraction data. • Simulated strain and polarization variations along the beam direction are retrieved. • This method can be used for 3D strain and polarization mapping without specimen tilt

  16. Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

    Energy Technology Data Exchange (ETDEWEB)

    Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburg, PA (United States); Dickey, Elizabeth C. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States)

    2017-02-15

    A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO{sub 3} single crystals. Further, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system. - Highlights: • A novel technique to directly polar domains utilizing EBSD is demonstrated. • The technique relies on dynamical diffraction simulations of EBSD patterns. • The technique is demonstrated by mapping 180° domains in LiNbO{sub 3} single crystals. • Further application of this technique to other materials classes is discussed.

  17. Polarization reversal of electron cyclotron wave due to radial boundary condition

    International Nuclear Information System (INIS)

    Takahashi, K.; Kaneko, T.; Hatakeyama, R.

    2004-01-01

    The electron cyclotron wave is an important plasma wave in the fields of basic plasma physics and nuclear fusion. Propagation and absorption of electromagnetic waves with electron cyclotron resonance (ECR) frequency are experimentally and theoretically investigated for the case of inhomogeneously magnetized plasma column with peripheral vacuum layer, when a left-hand polarized wave (LHPW) is selectively launched. The polarization reversal from the LHPW to the right-hand polarized wave is found to occur near the ECR point. As a result, it is clarified that the LHPW, which has been considered not to be absorbed at the ECR point, is absorbed near the ECR point. The phenomena can be explained by taking into account the effects of the radial boundary conditions. In addition, it is found that the polarization reversal point can be adjusted by the external parameters, for example, plasma radius. (authors)

  18. Target correlation and polarization effects on the electron impact ionization of He atoms

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Hari P, E-mail: hps1@physics.ucf.edu [Physics Department, University of Central Florida, Orlando, FL 32816 (United States)

    2011-03-28

    We have reported here the results of our investigation of the effects of electron correlation and polarization of the target in the incident channel on the electron impact ionization of the helium atom. The triple differential cross section (TDCS) is calculated for 28.6 eV incident electron energy for the case when the two final-state outgoing electrons share 4.0 eV excess energy equally and unequally and leave in the opposite direction. The electron correlation and polarization of the He-target in the initial state are considered completely ab initio using the recently extended multiconfiguration Hartree-Fock method. The electron correlation between the two outgoing electrons in the final state is included through the variationally determined screening potential. It is found that both target correlation and polarization in the incident channel play an important role; the polarization has larger effect on the TDCS than the target correlation. We compared our results with available experimental and theoretical data.

  19. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments

    Directory of Open Access Journals (Sweden)

    Maxime Deutsch

    2014-05-01

    Full Text Available Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  20. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments.

    Science.gov (United States)

    Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

    2014-05-01

    Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  1. Probing supersymmetry with parity-violating electron scattering

    OpenAIRE

    Kurylov, A.; Ramsey-Musolf, M. J.; Su, Shufang

    2003-01-01

    We compute the one-loop supersymmetric (SUSY) contributions to the weak charges of the electron ($Q_W^e$), proton ($Q_W^p$), and cesium nucleus ($Q_W^{\\rm Cs}$) in the Minimal Supersymmetric Standard Model (MSSM). Such contributions can generate several percent corrections to the corresponding Standard Model values. The magnitudes of the SUSY loop corrections to $Q_W^e$ and $Q_W^p$ are correlated over nearly all of the MSSM parameter space and result in an increase in the magnitudes of these ...

  2. Probing Plasmonic Nanostructures with Electron Energy - Loss Spectroscopy

    DEFF Research Database (Denmark)

    Raza, Søren

    for nonlocal response. The experimental work comprises the use of electron energy-loss spectroscopy (EELS) to excite and study both localized and propagating surface plasmons in metal structures. Following a short introduction, we present the theoretical foundation to describe nonlocal response in Maxwell......, dimer with nanometer-sized gaps, core-shell nanowire with ultrathin metal shell, and a thin metal film. In all cases we compare the nonlocal models with the local-response approximation. Below the plasma frequency, we find that the distance between the induced positive and negative surface charges...

  3. 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

  4. A 60 GHz Dual-Polarized Probe for Spherical Near-Field Measurements

    DEFF Research Database (Denmark)

    Popa, Paula Irina; Breinbjerg, Olav

    2017-01-01

    to waveguide adapters up to 67 GHz for OMT-switch connection. A 27 dBi gain conical horn is designed by using WIPL-D software and in-house manufactured. The 60 GHz probe system is being assembled and tested in planar near-field (PNF) setup at DTU. The results are validated by comparison with WIPL-D simulations...

  5. Probing space–time structure of new physics with polarized beams ...

    Indian Academy of Sciences (India)

    Abstract. At the international linear collider large beam polarization of both the elec- tron and positron beams will enhance the signature of physics due to interactions that are beyond the standard model. Here we review our recently obtained results on a general model-independent method of determining for an arbitary ...

  6. On the spallation of a polarized photon on a nonpolarized electron

    International Nuclear Information System (INIS)

    Bozrikov, P.V.; Kopytov, G.F.

    1978-01-01

    Considered is the process of the spallation of a polarized photon of the plane electromagnet wave into two polarized photons on a nonpolarized electron. One of these photons is considered as an emitted one, another as a photon of a plane wave. The degrees of circular and linear polarization of the emitted photon are studied in detail. It is shown that the degree of linear polarization does not depend on the type of circular polarization of the initial plane wave photon. At a relativistic electron moving in the direction of the plane wave, totally linearly polarized radiation appears. The analogy between the following two processes is made: (1) γ 1 +e - → γ 2 + γ tilde +e' - (where γ 1 , γ 2 are photons of the plane wave, and γ tilde is an emitted photon) and (2) γ 1 +e - → γ 2 +γ 3 +e' - . From the correspondence between the processes it follows that the results of the investigation may be applied to the double Compton effect. Besides, it appears to be possible to study the correlation between polarization states of all three photons participating in the double Compton scattering

  7. Electron motion in high-pressure polar gases: NH3

    International Nuclear Information System (INIS)

    Christophorou, L.G.; Carter, J.G.; Maxey, D.V.

    1982-01-01

    Drift velocities w for slow electrons in NH 3 vapor have been measured and are reported as a function of the density-reduced electric field E/N ( -17 V cm 2 ), density N (2.43--292 x 10 18 molecule cm -3 ), and temperature T (300--650 K). The w decreases with increasing N considerably and this decrease varies with T; for a fixed N it is higher the lower the T. Use is made of the T- and N-dependence of w to assess the role of the various processes which delay the electron drift. The density range above approx.2.5 x 10 19 molecules cm -3 seems (anionic) electron state. The number density N/sub L/ at which complete electron localization occurs, has been estimated at various T. At T = 300 K, N/sub L/approx. =3.3 x 10 20 molecule cm -3 or approx.0.01 g cm 3 . Estimates have also been made of the binding energy of the electron to the trapping species (possibly NH 3 clusters) which, depending on T, range from 0.11 to 0.15 eV

  8. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

    Science.gov (United States)

    Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

    2017-07-21

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  9. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

    KAUST Repository

    Govyadinov, Alexander A.

    2017-07-14

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  10. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

    KAUST Repository

    Govyadinov, Alexander A.; Konečná , Andrea; Chuvilin, Andrey; Vé lez, Saü l; Dolado, Irene; Nikitin, Alexey Y.; Lopatin, Sergei; Casanova, Fè lix; Hueso, Luis E.; Aizpurua, Javier; Hillenbrand, Rainer

    2017-01-01

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  11. Electron - polar acoustical phonon interactions in nitride based diluted magnetic semiconductor quantum well via hot electron magnetotransport

    International Nuclear Information System (INIS)

    Pandya, Ankur; Shinde, Satyam; Jha, Prafulla K.

    2015-01-01

    In this paper the hot electron transport properties like carrier energy and momentum scattering rates and electron energy loss rates are calculated via interactions of electrons with polar acoustical phonons for Mn doped BN quantum well in BN nanosheets via piezoelectric scattering and deformation potential mechanisms at low temperatures with high electric field. Electron energy loss rate increases with the electric field. It is observed that at low temperatures and for low electric field the phonon absorption is taking place whereas, for sufficient large electric field, phonon emission takes place. Under the piezoelectric (polar acoustical phonon) scattering mechanism, the carrier scattering rate decreases with the reduction of electric field at low temperatures wherein, the scattering rate variation with electric field is limited by a specific temperature beyond which there is no any impact of electric field on such scattering

  12. Vibrational excitations in molecular layers probed by ballistic electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kajen, Rasanayagam Sivasayan; Chandrasekhar, Natarajan [Institute of Materials Research and Engineering, 3 Research Link, 117602 (Singapore); Feng Xinliang; Muellen, Klaus [Max-Planck-Institut fuer Polymerforschung, Postfach 3148, D-55021 Mainz (Germany); Su Haibin, E-mail: n-chandra@imre.a-star.edu.sg, E-mail: muellen@mpip-mainz.mpg.de, E-mail: hbsu@ntu.edu.sg [Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

    2011-10-28

    We demonstrate the information on molecular vibrational modes via the second derivative (d{sup 2}I{sub B}/dV{sup 2}) of the ballistic electron emission spectroscopy (BEES) current. The proposed method does not create huge fields as in the case of conventional derivative spectroscopy and maintains a zero bias across the device. BEES studies carried out on three different types of large polycyclic aromatic hydrocarbon (PAH) molecular layers show that the d{sup 2}I{sub B}/dV{sup 2} spectra consist of uniformly spaced peaks corresponding to vibronic excitations. The peak spacing is found to be identical for molecules within the same PAH family though the BEES onset voltage varies for different molecules. In addition, injection into a particular orbital appears to correspond to a specific vibrational mode as the manifestation of the symmetry principle.

  13. Design and performance of a spin-polarized electron energy loss spectrometer with high momentum resolution

    Energy Technology Data Exchange (ETDEWEB)

    Vasilyev, D.; Kirschner, J. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

    2016-08-15

    We describe a new “complete” spin-polarized electron energy loss spectrometer comprising a spin-polarized primary electron source, an imaging electron analyzer, and a spin analyzer of the “spin-polarizing mirror” type. Unlike previous instruments, we have a high momentum resolution of less than 0.04 Å{sup −1}, at an energy resolution of 90-130 meV. Unlike all previous studies which reported rather broad featureless data in both energy and angle dependence, we find richly structured spectra depending sensitively on small changes of the primary energy, the kinetic energy after scattering, and of the angle of incidence. The key factor is the momentum resolution.

  14. Anisotropic electron velocity distribution in an ECR helium plasma as determined from polarization of emission lines

    International Nuclear Information System (INIS)

    Iwamae, A; Sato, T; Horimoto, Y; Inoue, K; Fujimoto, T; Uchida, M; Maekawa, T

    2005-01-01

    A helium plasma is produced by electron-cyclotron resonance heating in a cusp-configuration magnetic field. Several neutral helium lines are found polarized in the direction perpendicular to the magnetic field; the maximum polarization degree exceeds 10%. The polarization degree and intensity of the emission lines yield, respectively, the alignment and population of the upper levels. The population-alignment collisional-radiative model is developed, and the experimental result is interpreted in terms of an anisotropic electron velocity distribution; it is of a Saturn-type with the central thermal component of 14 eV and the 'ring' component displaced by 9.2 eV from the central component. The relative number of 'ring' electrons is 40%. (letter to the editor)

  15. Cross sections and spin polarizations of electrons elastically scattered from oriented molecules (CH3I)

    International Nuclear Information System (INIS)

    Fink, M.; Ross, A.W.; Fink, R.J.

    1989-01-01

    Elastic differential cross sections and spin polarizations for electrons elastically scattered from CH 3 I are calculated using the independent atom model. Three molecular orientations with respect to the incident electron wavevector are considered - first, the molecule is oriented randomly, second, the electron wave front and molecular bond are parallel, and third, the wavefront and the bond axis are perpendicular. It will be seen to what extent orientational averaging weakens features of the cross section and spin polarization. The calculations show that cross section and spin polarization measurements are a possible tool for determining the degree of molecular orientation. There is no degeneracy between I-C and C-I in cross section and spin polarization measurements. The results presented here for 200 eV and 600 eV electrons scattered by CH 3 I should be considered as a case study and it should be possible to find molecules and electron energies for which even more dramatic differences between the various orientations between the molecules and the electrons can be expected. (orig.)

  16. Polarimetry of the polarized hydrogen deuteride HDice target under an electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Laine, Vivien E. [Blaise Pascal Univ., Aubiere (France)

    2013-10-01

    The study of the nucleon structure has been a major research focus in fundamental physics in the past decades and still is the main research line of the Thomas Jefferson National Accelerator Facility (Jefferson Lab). For this purpose and to obtain statistically meaningful results, having both a polarized beam and a highly efficient polarized target is essential. For the target, this means high polarization and high relative density of polarized material. A Hydrogen Deuteride (HD) target that presents both such characteristics has been developed first at Brookhaven National Lab (BNL) and brought to the Hall B of Jefferson Lab in 2008. The HD target has been shown to work successfully under a high intensity photon beam (BNL and Jefferson Lab). However, it remained to be seen if the target could stand an electron beam of reasonably high current (nA). In this perspective, the target was tested for the first time in its frozen spin mode under an electron beam at Jefferson Lab in 2012 during the g14 experiment. This dissertation presents the principles and usage procedures of this HD target. The polarimetry of this target with Nuclear Magnetic Resonance (NMR) during the electron beam tests is also discussed. In addition, this dissertation also describes another way to perform target polarimetry with the elastic scattering of electrons off a polarized target by using data taken on helium-3 during the E97-110 experiment that occurred in Jefferson Lab's Hall A in 2003.

  17. Influence of Neutral Currents on Electron and Gamma Polarizations in the Process e+N→e′+N+γ

    International Nuclear Information System (INIS)

    Ousmane Manga, Adamou; Moussa, Aboubacar; Aboubacar, Almoustapha; Samsonenko, N. V.

    2014-01-01

    The differential cross section of electron inelastic scattering by nuclei followed by γ radiation is calculated using the multipole decomposition of the hadronic currents and by taking into account the longitudinal polarization of the initial electron and the circular polarization of the γ radiation. We performed the analysis of the angular and energy dependence of the degree of electron and photon polarization which can yield information on values of weak neutral currents parameters

  18. Probing spin-polarized edge state superconductivity by Andreev reflection in in-plane magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Reinthaler, Rolf W.; Tkachov, Grigory; Hankiewicz, Ewelina M. [Faculty of Physics and Astrophysics, University of Wuerzburg, Wuerzburg (Germany)

    2015-07-01

    Finding signatures of unconventional superconductivity in Quantum Spin Hall systems is one of the challenges of solid state physics. Here we induce superconductivity in a 3D topological insulator thin film to cause the formation of helical edge states, which are protected against backscattering even in finite magnetic fields. Above a critical in-plane magnetic field, which is much smaller than the critical field of typical superconductors, the quasi-particle gap closes, giving rise to energy-dependent spin polarization. In this regime the spin-polarized edge state superconductivity can be detected by Andreev reflection. We propose measurement setups to experimentally observe the spin-dependent excess current and dI/dV characteristics.

  19. Mining social media data for opinion polarities about electronic cigarettes.

    Science.gov (United States)

    Dai, Hongying; Hao, Jianqiang

    2017-03-01

    There is an ongoing debate about harm and benefit of e-cigarettes, usage of which has rapidly increased in recent years. By separating non-commercial (organic) tweets from commercial tweets, we seek to evaluate the general public's attitudes towards e-cigarettes. We collected tweets containing the words 'e-cig', 'e-cigarette', 'e-liquid', 'vape', 'vaping', 'vapor' and 'vaporizer' from 23 July to 14 October 2015 (n=757 167). A multilabel Naïve Bayes model was constructed to classify tweets into 5 polarities (against, support, neutral, commercial, irrelevant). We further analysed the prevalence of e-cigarette tweets, geographic variations in these tweets and the impact of socioeconomic factors on the public attitudes towards e-cigarettes. Opinions from organic tweets about e-cigarettes were mixed (against 17.7%, support 10.8% and neutral 19.4%). The organic-against tweets delivered strong educational information about the risks of e-cigarette use and advocated for the general public, especially youth, to stop vaping. However, the organic-against tweets were outnumbered by commercial tweets and organic-support tweets by a ratio of over 1 to 3. Higher prevalence of organic tweets was associated with states with higher education rates (r=0.60, p<0.0001), higher percentage of black and African-American population (r=0.34, p=0.01), and higher median household income (r=0.33, p=0.02). The support rates for e-cigarettes were associated with states with fewer persons under 18 years old (r=-0.33, p=0.02) and a higher percentage of female population (r=0.3, p=0.02). The organic-against tweets raised public awareness of potential health risks and could aid in preventing non-smokers, adolescents and young adults from using e-cigarettes. Opinion polarities about e-cigarettes from social networks could be highly influential to the general public, especially youth. Further educational campaigns should include measuring their effectiveness. Published by the BMJ Publishing Group

  20. Design and commissioning of an aberration-corrected ultrafast spin-polarized low energy electron microscope with multiple electron sources.

    Science.gov (United States)

    Wan, Weishi; Yu, Lei; Zhu, Lin; Yang, Xiaodong; Wei, Zheng; Liu, Jefferson Zhe; Feng, Jun; Kunze, Kai; Schaff, Oliver; Tromp, Ruud; Tang, Wen-Xin

    2017-03-01

    We describe the design and commissioning of a novel aberration-corrected low energy electron microscope (AC-LEEM). A third magnetic prism array (MPA) is added to the standard AC-LEEM with two prism arrays, allowing the incorporation of an ultrafast spin-polarized electron source alongside the standard cold field emission electron source, without degrading spatial resolution. The high degree of symmetries of the AC-LEEM are utilized while we design the electron optics of the ultrafast spin-polarized electron source, so as to minimize the deleterious effect of time broadening, while maintaining full control of electron spin. A spatial resolution of 2nm and temporal resolution of 10ps (ps) are expected in the future time resolved aberration-corrected spin-polarized LEEM (TR-AC-SPLEEM). The commissioning of the three-prism AC-LEEM has been successfully finished with the cold field emission source, with a spatial resolution below 2nm. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Inner Core Tilt and Polar Motion: Probing the Dynamics Deep Inside the Earth

    Science.gov (United States)

    Dumberry, M.; Bloxham, J.

    2003-12-01

    A tilted inner core permits exchange of angular momentum between the core and the mantle through gravitational and pressure torques and, as a result, changes in the direction of Earth's axis of rotation with respect to the mantle. Some of the observed variations in the direction of Earth's rotation could then be caused by equatorial torques on the inner core which tilt the latter out of its alignment with the mantle. In this work, we investigate whether such a scenario could explain the decade polar motion known as the Markowitz wobble. We show that a decade polar motion of the same amplitude as the observed Markowitz wobble requires a torque of 1020 N m which tilts the inner core by 0.07 degrees. This result critically depends on the viscosity of the inner core; for a viscosity less than 5 x 1017 Pa s, larger torques are required. A torque of 1020 N m with decadal periodicity can perhaps be produced by electromagnetic coupling between the inner core and a component of the flow in the outer core known as torsional oscillations, provided that the radial magnetic field at the inner core boundary is on the order of 3 to 4 mT and satisfies certain geometrical constraints. The resulting polar motion thus produced is eccentric and polarized, in agreement with the observations. Our model suggests that equatorial torques at the inner core boundary might also excite the Chandler wobble, provided shorter wavelength torsional oscillations with higher natural frequencies have enough power or provided there exists another physical mechanism that can generate a large torque at a 14 month period.

  2. Electron transfer reactions to probe the electrode/solution interface

    Energy Technology Data Exchange (ETDEWEB)

    Capitanio, F.; Guerrini, E.; Colombo, A.; Trasatti, S. [Milan Univ., Milan (Italy). Dept. of Physical Chemistry and Electrochemistry

    2008-07-01

    The reactions that occur at the interface between an electrode and an electrolyte were examined with particular reference to the interaction of different electrode surfaces with redox couples. A semi-integration or convolution technique was used to study the kinetics of electron transfer on different electrode materials with different hydrophilic behaviour, such as Boron-Doped-Diamond (BDD), Au and Pt. Standard reversible redox couples were also investigated, including (Fe3+/2+, Fe(CN)63-/4-, Ru(NH3)63+/2+, Co(NH3)63+/2+, Ir4+/3+, V4+/5+ and V3+/2+). The proposed method proved to be simple, straightforward and reliable since the obtained kinetic information was in good agreement with data in the literature. It was concluded that the kinetics of the electrode transfer reactions depend on the chemical nature of the redox couple and electrode material. The method should be further extended to irreversible couples and other electrode materials such as mixed oxide electrodes. 3 refs., 2 figs.

  3. Experimental Route to Scanning Probe Hot Electron Nanoscopy (HENs) Applied to 2D Material

    KAUST Repository

    Giugni, Andrea; Torre, Bruno; Allione, Marco; Das, Gobind; Wang, Zhenwei; He, Xin; Alshareef, Husam N.; Di Fabrizio, Enzo M.

    2017-01-01

    for applications in electronics: 2D MoS2 single crystal and a p-type SnO layer. Results are supported by complementary scanning Kelvin probe microscopy, traditional conductive AFM, and Raman measurements. New features highlighted by HEN technique reveal details

  4. Diagnosis of early human myocardial ischemic damage with electron probe microanalysis

    International Nuclear Information System (INIS)

    Singh, S.; Abraham, J.L.; Raasch, F.; Wolf, P.; Bloor, C.M.

    1983-01-01

    We determined the Na/K x-ray intensity ratio in frozen sections of myocardial tissues obtained at autopsy from patients who died from various causes, using electron probe analysis. We have been able to distinguish between the ischemically injured and normal cells. The method is simple, fast, and dependable even when the duration of ischemia is only 30 minutes

  5. Mach probe interpretation in the presence of supra-thermal electrons

    Czech Academy of Sciences Publication Activity Database

    Fuchs, Vladimír; Gunn, J. P.

    2007-01-01

    Roč. 14, č. 3 (2007), 032501-1 ISSN 1070-664X R&D Projects: GA ČR GA202/04/0360 Institutional research plan: CEZ:AV0Z20430508 Keywords : Mach probes * supra -thermal electrons * quasi-neutral PIC codes Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.325, year: 2007

  6. Prospects for Measuring $\\Delta$G from Jets at HERA with Polarized Protons and Electrons

    CERN Document Server

    De Roeck, A.; Kunne, F.; Maul, M.; Schafer, A.; Wu, C.Y.; Mirkes, E.; Radel, G.

    1996-01-01

    The measurement of the polarized gluon distribution function Delta G(x) from photon-gluon fusion processes in electron-proton deep inelastic scattering producing two jets has been investigated. The study is based on the MEPJET and PEPSI simulation programs. The size of the expected spin asymmetry and corresponding statistical uncertainties for a possible measurement with polarized beams of electrons and protons at HERA have been estimated. The results show that the asymmetry can reach a few percent, and is not washed out by hadronization and higher order processes.

  7. Prospects for measuring ΔG from jets at HERA with polarized protons and electrons

    International Nuclear Information System (INIS)

    Roeck, A. de; Feltesse, J.; Kunne, F.; Maul, M.; Schaefer, A.; Wu, C.Y.; Mirkes, E.; Raedel, G.

    1996-09-01

    The measurement of the polarized gluon distribution function ΔG(x) from photon-gluon fusion processes in electron-proton deep inelastic scattering producing two jets has been investigated. The study is based on the MEPJET and PEPSI simulation programs. The size of the expected spin asymmetry and corresponding statistical uncertainties for a possible measurement with polarized beams of electrons and protons at HERA have been estimated. The results show that the asymmetry can reach a few percent, and is not washed out by hadronization and higher order processes. (orig.)

  8. Final-photon polarization in the scattering of photons by high-energy electrons

    International Nuclear Information System (INIS)

    Choi, J.; Choi, S.Y.; Ie, S.H.; Song, H.S.; Good, R.H. Jr.

    1987-01-01

    A general method for calculating the polarization of the outgoing photon beam in any reaction is presented. As an example the method is applied to the high-energy photon beam produced in Compton scattering of a laser beam by a high-energy electron beam. The Stokes parameters of the outgoing photon beam, relative to a unit vector normal to the photon momentum and including their dependence on the polarization of incident photon and electron beams, are obtained explicitly. It is expected that this method will be useful, both in photon production reactions and in the subsequent high-energy photon reactions

  9. Polarized Bhabha scattering and a precision measurement of the electron neutral current couplings

    International Nuclear Information System (INIS)

    Abe, K.; Abt, I.; Ahn, C.J.; Akagi, T.; Ash, W.W.; Aston, D.; Bacchetta, N.; Baird, K.G.; Baltay, C.; Band, H.R.; Barakat, M.B.; Baranko, G.; Bardon, O.; Barklow, T.; Bazarko, A.O.; Ben-David, R.; Benvenuti, A.C.; Bienz, T.; Bilei, G.M.; Bisello, D.; Blaylock, G.; Bogart, J.R.; Bolton, T.; Bower, G.R.; Brau, J.E.; Breidenbach, M.; Bugg, W.M.; Burke, D.; Burnett, T.H.; Burrows, P.N.; Busza, W.; Calcaterra, A.; Caldwell, D.O.; Calloway, D.; Camanzi, B.; Carpinelli, M.; Cassell, R.; Castaldi, R.; Castro, A.; Cavalli-Sforza, M.; Church, E.; Cohn, H.O.; Coller, J.A.; Cook, V.; Cotton, R.; Cowan, R.F.; Coyne, D.G.; D'Oliveira, A.; Damerell, C.J.S.; Dasu, S.; De Sangro, R.; De Simone, P.; Dell'Orso, R.; Dima, M.; Du, P.Y.C.; Dubois, R.; Eisenstein, B.I.; Elia, R.; Falciai, D.; Fan, C.; Fero, M.J.; Frey, R.; Furuno, K.; Gillman, T.; Gladding, G.; Gonzalez, S.; Hallewell, G.D.; Hart, E.L.; Hasegawa, Y.; Hedges, S.; Hertzbach, S.S.; Hildreth, M.D.; Huber, J.; Huffer, M.E.; Hughes, E.W.; Hwang, H.; Iwasaki, Y.; Jacques, P.; Jaros, J.; Johnson, A.S.; Johnson, J.R.; Johnson, R.A.; Junk, T.; Kajikawa, R.; Kalelkar, M.; Karliner, I.; Kawahara, H.; Kendall, H.W.; Kim, Y.; King, M.E.; King, R.; Kofler, R.R.; Krishna, N.M.; Kroeger, R.S.; Labs, J.F.; Langston, M.; Lath, A.; Lauber, J.A.; Leith, D.W.G.; Liu, X.; Loreti, M.; Lu, A.; Lynch, H.L.; Ma, J.; Mancinelli, G.; Manly, S.; Mantovani, G.; Markiewicz, T.W.; Maruyama, T.; Massetti, R.; Masuda, H.; Mazzucato, E.; McKemey, A.K.; Meadows, B.T.; Messner, R.; Mockett, P.M.; Moffeit, K.C.; Mours, B.; Mueller, G.; Muller, D.; Nagamine, T.; Nauenberg, U.; Neal, H.; Nussbaum, M.; Ohnishi, Y.; Osborne, L.S.; Panvini, R.S.; Park, H.; Pavel, T.J.; Peruzzi, I.; Pescara, L.; Piccolo, M.; Piemontese, L.; Pieroni, E.; Pitts, K.T.; Plano, R.J.; Prepost, R.; Prescott, C.Y.; Punkar, G.D.; Quigley, J.; Ratcliff, B.N.; Reeves, T.W.; Rensing, P.E.; Rochester, L.S.; Rothberg, J.E.; Rowson, P.C.; Russell, J.J.; Saxton, O.H.; Schalk, T.

    1995-01-01

    Bhabha scattering with polarized electrons at the Z 0 resonance has been measured with the SLD experiment at the SLAC Linear Collider. The first measurement of the left-right asymmetry in Bhabha scattering is presented, yielding the effective weak mixing angle of sinθ eff W =0.2245±0.0049±0.0010. The effective electron couplings to the Z 0 are extracted from a combined analysis of polarized Bhabha scattering and the left-right asymmetry previously published: υ e =-0.0414±0.0020 and a e =-0.4977±0.0045

  10. Parity Violation in Atoms and Polarized Electron Scattering

    CERN Document Server

    Bouchiat, Marie-Anne; PAVI'97

    1999-01-01

    This work is an extensive review of the advances in the field of parity violation experiments in electron scattering at high energy and and in atomic physics. The results are a challenge to the standard electroweak theory and the understanding of hadron structure. The theoretical framework is presented at a pedagogical level, experiments and future projects are reviewed, and the results and their interpretation are discussed.

  11. Leveraging Technological Capabilities across Polarized Cultures: Shanghai Delco Electronics Limited

    OpenAIRE

    Lucy A. Ojode

    2006-01-01

    Rallying its units for an impending spin-off from General Motors, the Delphi Automotive Systems division cleared the Delphi Delco Electronics (Delphi-D) unit to begin planning for entry into China in 1994. Delphi saw China as ideal for leveraging its technological and innovation capabilities as well as the enormous General Motor heritage and reputation from years of experience delivering quality products to the automotive industry. Delphi-D found a perfect partner in Shanghai Changjiang YiBia...

  12. Electron-energy relaxation in polar semiconductor double quantum dots

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Khás, Zdeněk; Zdeněk, Petr; Čerňanský, Marian; Lin, C. Y.

    2001-01-01

    Roč. 15, č. 27 (2001), s. 3503-3512 ISSN 0217-9792 R&D Projects: GA AV ČR IAA1010113; GA MŠk OC P5.20 Institutional research plan: CEZ:AV0Z1010914 Keywords : electron ic energy relaxation * zero-dimensional nanostructures Subject RIV: BE - The oretical Physics Impact factor: 0.523, year: 2001

  13. Probing Individual Ice Nucleation Events with Environmental Scanning Electron Microscopy

    Science.gov (United States)

    Wang, Bingbing; China, Swarup; Knopf, Daniel; Gilles, Mary; Laskin, Alexander

    2016-04-01

    Heterogeneous ice nucleation is one of the processes of critical relevance to a range of topics in the fundamental and the applied science and technologies. Heterogeneous ice nucleation initiated by particles proceeds where microscopic properties of particle surfaces essentially control nucleation mechanisms. Ice nucleation in the atmosphere on particles governs the formation of ice and mixed phase clouds, which in turn influence the Earth's radiative budget and climate. Heterogeneous ice nucleation is still insufficiently understood and poses significant challenges in predictive understanding of climate change. We present a novel microscopy platform allowing observation of individual ice nucleation events at temperature range of 193-273 K and relative humidity relevant for ice formation in the atmospheric clouds. The approach utilizes a home built novel ice nucleation cell interfaced with Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system is applied for direct observation of individual ice formation events, determining ice nucleation mechanisms, freezing temperatures, and relative humidity onsets. Reported microanalysis of the ice nucleating particles (INP) include elemental composition detected by the energy dispersed analysis of X-rays (EDX), and advanced speciation of the organic content in particles using scanning transmission x-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The performance of the IN-ESEM system is validated through a set of experiments with kaolinite particles with known ice nucleation propensity. We demonstrate an application of the IN-ESEM system to identify and characterize individual INP within a complex mixture of ambient particles.

  14. Magnetic field vector and electron density diagnostics from linear polarization measurements in 14 solar prominences

    Science.gov (United States)

    Bommier, V.

    1986-01-01

    The Hanle effect is the modification of the linear polarization parameters of a spectral line due to the effect of the magnetic field. It has been successfully applied to the magnetic field vector diagnostic in solar prominences. The magnetic field vector is determined by comparing the measured polarization to the polarization computed, taking into account all the polarizing and depolarizing processes in line formation and the depolarizing effect of the magnetic field. The method was applied to simultaneous polarization measurements in the Helium D3 line and in the hydrogen beta line in 14 prominences. Four polarization parameters are measured, which lead to the determination of the three coordinates of the magnetic field vector and the electron density, owing to the sensitivity of the hydrogen beta line to the non-negligible effect of depolarizing collisions with electrons and protons of the medium. A mean value of 1.3 x 10 to the 10th power cu. cm. is derived in 14 prominences.

  15. Acceleration of polarized electrons in the Bonn synchrotron and the planned stretcher ring ELSA

    International Nuclear Information System (INIS)

    Brefeld, W.

    1981-10-01

    In the last year at the synchrotron polarized electrons were successfully accelerated. For this the polarization vector in the transfer channel between source and LINAC was rotated in such a way that the electrons can be injected into the accelerator with the necessary vertical polarization. It was shown that the degree of polarization of the electrons after passing of the imperfection resonances at 0.441 GeV, 0.881 GeV, 1.322 GeV, and 1.763 GeV and the intrinsic resonance at 1.498 GeV remained conserved at a high degree also without additional procedures. Although it is desirable to reduce the present depolarization. First attempts for overcoming the second resonance were performed. The results indicate that for this a system of two pulse dipoles doesn't suffice. For the answer of this question however a much more intensive polarized source is needed. At ELSA the working with polarized electrons seems to be possible in the whole energy range if it succeeds to circumvent the position of the intrinsic resonance dependent from the working point. Though the imperfection resonances at 2.203 GeV, 2.644 GeV, and 3.085 GeV can depolarize the electrons much more strongly because of the relatively slow passing through the resonances an overcoming with pulse dipoles should by possible. Because of the large resonance time-distances the dipoles have much more time than in the synchrotron to reach the required value steadily. (orig.) [de

  16. Electron temperature and heat load measurements in the COMPASS divertor using the new system of probes

    Science.gov (United States)

    Adamek, J.; Seidl, J.; Horacek, J.; Komm, M.; Eich, T.; Panek, R.; Cavalier, J.; Devitre, A.; Peterka, M.; Vondracek, P.; Stöckel, J.; Sestak, D.; Grover, O.; Bilkova, P.; Böhm, P.; Varju, J.; Havranek, A.; Weinzettl, V.; Lovell, J.; Dimitrova, M.; Mitosinkova, K.; Dejarnac, R.; Hron, M.; The COMPASS Team; The EUROfusion MST1 Team

    2017-11-01

    A new system of probes was recently installed in the divertor of tokamak COMPASS in order to investigate the ELM energy density with high spatial and temporal resolution. The new system consists of two arrays of rooftop-shaped Langmuir probes (LPs) used to measure the floating potential or the ion saturation current density and one array of Ball-pen probes (BPPs) used to measure the plasma potential with a spatial resolution of ~3.5 mm. The combination of floating BPPs and LPs yields the electron temperature with microsecond temporal resolution. We report on the design of the new divertor probe arrays and first results of electron temperature profile measurements in ELMy H-mode and L-mode. We also present comparative measurements of the parallel heat flux using the new probe arrays and fast infrared termography (IR) data during L-mode with excellent agreement between both techniques using a heat power transmission coefficient γ  =  7. The ELM energy density {{\\varepsilon }\\parallel } was measured during a set of NBI assisted ELMy H-mode discharges. The peak values of {{\\varepsilon }\\parallel } were compared with those predicted by model and with experimental data from JET, AUG and MAST with a good agreement.

  17. Study of an efficient application of the tagged bremsstrahlung in double-polarization experiments in the GeV range and the use of the inelastic electron scattering under extremely forward angles as alternative to the tagged bremsstrahlung

    International Nuclear Information System (INIS)

    Konrad, M.

    2006-03-01

    For the preparation of photonic probes for hadron physics the determination of energy and polarization of the photons is essential. In this dissertation in a first part a possibility of the determination of the degree of polarization by use of the asymmetry observables is presented. In a second part a possibility isd discussed to perform an energy and polarization tagging of nearly real photons in electron scattering under small Q 2 . By this method it should be possible to tag billions of photons per second

  18. Ion sense of polarization of the electromagnetic wave field in the electron whistler frequency band

    Directory of Open Access Journals (Sweden)

    B. Lundin

    Full Text Available It is shown that the left-hand (or ion-type sense of polarization can appear in the field interference pattern of two plane electron whistler waves. Moreover, it is demonstrated that the ion-type polarized wave electric fields can be accompanied by the presence at the same observation point of electron-type polarized wave magnetic fields. The registration of ion-type polarized fields with frequencies between the highest ion gyrofrequency and the electron gyrofrequency in a cold, overdense plasma is a sufficient indication for the existence of an interference wave pattern, which can typically occur near artificial or natural reflecting magnetospheric plasma regions, inside waveguides (as in helicon discharges, for example, in fields resonantly emitted by beams of charged particles or, in principle, in some self-sustained, nonlinear wave field structures. A comparison with the conventional spectral matrix data processing approach is also presented in order to facilitate the calculations of the analyzed polarization parameters.

    Key words. Ionosphere (wave propagation Radio science (waves in plasma Space plasma physics (general or miscellaneous

  19. Ion sense of polarization of the electromagnetic wave field in the electron whistler frequency band

    Directory of Open Access Journals (Sweden)

    B. Lundin

    2002-08-01

    Full Text Available It is shown that the left-hand (or ion-type sense of polarization can appear in the field interference pattern of two plane electron whistler waves. Moreover, it is demonstrated that the ion-type polarized wave electric fields can be accompanied by the presence at the same observation point of electron-type polarized wave magnetic fields. The registration of ion-type polarized fields with frequencies between the highest ion gyrofrequency and the electron gyrofrequency in a cold, overdense plasma is a sufficient indication for the existence of an interference wave pattern, which can typically occur near artificial or natural reflecting magnetospheric plasma regions, inside waveguides (as in helicon discharges, for example, in fields resonantly emitted by beams of charged particles or, in principle, in some self-sustained, nonlinear wave field structures. A comparison with the conventional spectral matrix data processing approach is also presented in order to facilitate the calculations of the analyzed polarization parameters.Key words. Ionosphere (wave propagation Radio science (waves in plasma Space plasma physics (general or miscellaneous

  20. Monte Carlo studies of thermalization of electron-hole pairs in spin-polarized degenerate electron gas in monolayer graphene

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2018-02-01

    Monte Carlo method is applied to the study of relaxation of excited electron-hole (e-h) pairs in graphene. The presence of background of spin-polarized electrons, with high density imposing degeneracy conditions, is assumed. To such system, a number of e-h pairs with spin polarization parallel or antiparallel to the background is injected. Two stages of relaxation: thermalization and cooling are clearly distinguished when average particles energy and its standard deviation σ _E are examined. At the very beginning of thermalization phase, holes loose energy to electrons, and after this process is substantially completed, particle distributions reorganize to take a Fermi-Dirac shape. To describe the evolution of and σ _E during thermalization, we define characteristic times τ _ {th} and values at the end of thermalization E_ {th} and σ _ {th}. The dependence of these parameters on various conditions, such as temperature and background density, is presented. It is shown that among the considered parameters, only the standard deviation of electrons energy allows to distinguish between different cases of relative spin polarizations of background and excited electrons.

  1. Micro-four-point probes in a UHV scanning electron microscope for in-situ surface-conductivity measurements

    DEFF Research Database (Denmark)

    Shiraki, I.; Nagao, T.; Hasegawa, S.

    2000-01-01

    For in-situ measurements of surface conductivity in ultrahigh vacuum (UHV), we have installed micro-four-point probes (probe spacings down to 4 mum) in a UHV scanning electron microscope (SEM) combined with scanning reflection-high-energy electron diffraction (RHEED). With the aid of piezoactuators...

  2. Sensitivity of self-powered detector probes to electron and gamma-ray fields

    Energy Technology Data Exchange (ETDEWEB)

    Lone, M A; Wong, P Y [Atomic Energy of Canada Ltd., Chalk River, ON (Canada)

    1996-12-31

    A self-powered detector (SPD) is a simple, passive device that consists of a coaxial probe with a metallic outer sleeve, a mineral oxide insulating layer, and a metallic inner core. SPD`s are used in nuclear reactors to monitor neutron and gamma fields. Responses of SPD`s to electrons and {gamma}-rays of various energies were investigated with Monte Carlo simulations. Transmission filters were studied for the design of threshold SPD probes used for online monitoring of the energy spectrum of high-power industrial electron accelerator beams. Filters were also investigated for the enhancement of {gamma}-ray sensitivity of an SPD placed in a mixed electron and {gamma}-ray field. (author). 30 refs., 1 tab., 8 figs.

  3. Sensitivity of self-powered detector probes to electron and gamma-ray fields

    International Nuclear Information System (INIS)

    Lone, M.A.; Wong, P.Y.

    1995-01-01

    A self-powered detector (SPD) is a simple, passive device that consists of a coaxial probe with a metallic outer sleeve, a mineral oxide insulating layer, and a metallic inner core. SPD's are used in nuclear reactors to monitor neutron and gamma fields. Responses of SPD's to electrons and γ-rays of various energies were investigated with Monte Carlo simulations. Transmission filters were studied for the design of threshold SPD probes used for online monitoring of the energy spectrum of high-power industrial electron accelerator beams. Filters were also investigated for the enhancement of γ-ray sensitivity of an SPD placed in a mixed electron and γ-ray field. (author). 30 refs., 1 tab., 8 figs

  4. Probing plasmons in three dimensions by combining complementary spectroscopies in a scanning transmission electron microscope

    International Nuclear Information System (INIS)

    Hachtel, J A; Haglund, R F; Pantelides, S T; Marvinney, C; Mayo, D; Mouti, A; Lupini, A R; Chisholm, M F; Mu, R; Pennycook, S J

    2016-01-01

    The nanoscale optical response of surface plasmons in three-dimensional metallic nanostructures plays an important role in many nanotechnology applications, where precise spatial and spectral characteristics of plasmonic elements control device performance. Electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) within a scanning transmission electron microscope have proven to be valuable tools for studying plasmonics at the nanoscale. Each technique has been used separately, producing three-dimensional reconstructions through tomography, often aided by simulations for complete characterization. Here we demonstrate that the complementary nature of the two techniques, namely that EELS probes beam-induced electronic excitations while CL probes radiative decay, allows us to directly obtain a spatially- and spectrally-resolved picture of the plasmonic characteristics of nanostructures in three dimensions. The approach enables nanoparticle-by-nanoparticle plasmonic analysis in three dimensions to aid in the design of diverse nanoplasmonic applications. (paper)

  5. Electron dropout echoes induced by interplanetary shock: Van Allen Probes observations

    International Nuclear Information System (INIS)

    Hao, Y. X.; Zong, Q.-G.; Zhou, X.-Z.; Fu, S. Y.; Rankin, R.

    2016-01-01

    On 23 November 2012, a sudden dropout of the relativistic electron flux was observed after an interplanetary shock arrival. The dropout peaks at ~1 MeV and more than 80% of the electrons disappeared from the drift shell. Van Allen twin Probes observed a sharp electron flux dropout with clear energy dispersion signals. The repeating flux dropout and recovery signatures, or “dropout echoes”, constitute a new phenomenon referred to as a “drifting electron dropout” with a limited initial spatial range. The azimuthal range of the dropout is estimated to be on the duskside, from ~1300 to 0100 LT. We then conclude that the shock-induced electron dropout is not caused by the magnetopause shadowing. Furthermore, the dropout and consequent echoes suggest that the radial migration of relativistic electrons is induced by the strong dusk-dawn asymmetric interplanetary shock compression on the magnetosphere.

  6. Pyrene absorption can be a convenient method for probing critical micellar concentration (cmc) and indexing micellar polarity.

    Science.gov (United States)

    Basu Ray, Gargi; Chakraborty, Indranil; Moulik, Satya P

    2006-02-01

    The critical micellar concentration (cmc) of both ionic and non-ionic surfactants can be conveniently determined from the measurements of UV absorption of pyrene in surfactant solution. The results on a number of surfactants have agreed with that realized from pyrene fluorescence measurements as well as that obtained following conductometric, tensiometric and calorimetric methods. The absorbance vs [surfactant] profiles for all the major UV spectral peaks of pyrene have been found to be sigmoidal in nature which were analyzed according to Sigmoidal-Boltzmann equation (SBE) to evaluate the cmcs of the studied surfactants. The difference between the initial and the final asymptotes (a(i) and a(f), respectively) of the sigmoidal profile, Delta a = (a(f)-a(i)) and the slope of the sigmoid, S(sig) have been observed to depend on the type of the surfactant. The Delta a has shown a linear correlation with the ratio of the fluorescence intensities of the first and the third vibronic peaks, I1/I3 of pyrene which is considered as a measure of the environmental polarity (herein micellar interior) of the probe (pyrene). Thus, Delta a values have the prospect for use as another index for the estimation of polarity of micellar interior.

  7. Characterization of polarized electrons coming from helium post-discharge source

    International Nuclear Information System (INIS)

    Zerhouni, R.O.

    1996-02-01

    The objective of this thesis is the characterization of the polarized electron source developed at Orsay and foreseen to be coupled to a cw accelerator for nuclear physics experiments. The principle of operation of this source relies on the chemo-ionization reaction between optically aligned helium triplet metastable atoms and CO 2 molecules. The helium metastable atoms are generated by injection of purified helium into a 2,45 GHz micro-wave discharge. They are optically pumped using two beams of 1,083 micro-meter resonant radiation, one circularly and the other linearly polarized. Both beams are delivered by a high power LNA laser. The metastable atomic beam interacts with a dense (10 13 cm -3 ) spin singlet CO 2 target. A fraction of the produced polarized electrons is extracted and collimated by electrostatic optics. Either to the Mott polarimeter or to the Faraday cup in order to measure the electron polarization and extracted current. For current intensities of 100 micro-Amperes, the electronic polarization reaches 62 % and shows that this type of source has reached the same high competitive level as the most performing GaAs ones. Additionally, the optical properties of the extracted beam are found to be excellent. These properties (energy spread and emittance) reflect the electron energy distribution at the chemo-ionization region. The upper limit of the beam's energy spread is 0.24 eV since this value characterizes our instrumental resolution. The average normalized emittance is found to be 0.6 pi mm-mrad. These values satisfy the requirements of most cw accelerators. All the measurements were performed at low electron beam transport energies (1 to 2 KeV). (author). 105 refs., 54 figs., 4 tabs

  8. IMPURITY SEGREGATION OF STAINLESS STEEL STUDIED BY ATOM-PROBE AND AUGER ELECTRON SPECTROSCOPY

    OpenAIRE

    Koguchi , Y.; Takahashi , K.; Ishikawa , Y.

    1987-01-01

    The surface compositions of type 304 stainless steel heated in vacuum at 600-900°C were determined by an atom-probe and Auger electron spectroscopic analysis. In addition to enrichment and depletion of alloying elements in the surface of the stainless steel, segregation of impurity elements such as carbon, nitrogen, phosphorus and sulfur is known to occur. In this paper the atom-probe was used to measure the impurity segregation in the grains as well as in the grain boundary while the AES was...

  9. Probing Protein Structure and Folding in the Gas Phase by Electron Capture Dissociation

    Science.gov (United States)

    Schennach, Moritz; Breuker, Kathrin

    2015-07-01

    The established methods for the study of atom-detailed protein structure in the condensed phases, X-ray crystallography and nuclear magnetic resonance spectroscopy, have recently been complemented by new techniques by which nearly or fully desolvated protein structures are probed in gas-phase experiments. Electron capture dissociation (ECD) is unique among these as it provides residue-specific, although indirect, structural information. In this Critical Insight article, we discuss the development of ECD for the structural probing of gaseous protein ions, its potential, and limitations.

  10. The high peak current polarized electron source of the Stanford Linear Collider

    International Nuclear Information System (INIS)

    Schultz, D.; Alley, R.; Aoyagi, H.; Clendenin, J.; Frisch, J.; Garden, C.; Hoyt, E.; Kirby, R.; Klaisner, L.; Kulikov, A.; Mulhollan, G.; Prescott, C.; Saez, P.; Tang, H.; Turner, J.; Woods, M.; Yeremian, D.; Zolotorev, M.

    1994-01-01

    The Stanford Linear Collider injector requires two 2 ns pulses of 4.5-5.5 x 10 10 electrons, separated by 61 ns at 120 Hz, from its source. Since 1992, these currents have been provided by a polarized electron source based on GaAs photocathodes. A beam polarization of 76±4% has been measured at the end of the 50 GeV linac. At low photocathode quantum efficiencies, and for excitation near threshold, the maximum current delivered by the source is constrained, not by the space charge limit of the gun, but by a ''charge limit'' of the photocathode. The charge limited current is proportional to the photocathode quantum efficiency, but the proportionality varies for different photocathode types. Experience with high polarization strained GaAs photocathodes on a test beamline and on the SLC is presented. (orig.)

  11. Measurement of the transverse polarization of electrons emitted in free-neutron decay.

    Science.gov (United States)

    Kozela, A; Ban, G; Białek, A; Bodek, K; Gorel, P; Kirch, K; Kistryn, St; Kuźniak, M; Naviliat-Cuncic, O; Pulut, J; Severijns, N; Stephan, E; Zejma, J

    2009-05-01

    Both components of the transverse polarization of electrons (sigmaT1, sigmaT2) emitted in the beta-decay of polarized, free neutrons have been measured. The T-odd, P-odd correlation coefficient quantifying sigmaT2, perpendicular to the neutron polarization and electron momentum, was found to be R=0.008+/-0.015+/-0.005. This value is consistent with time reversal invariance and significantly improves limits on the relative strength of imaginary scalar couplings in the weak interaction. The value obtained for the correlation coefficient associated with sigmaT1, N=0.056+/-0.011+/-0.005, agrees with the Standard Model expectation, providing an important sensitivity test of the experimental setup.

  12. Remote sensing of electron density and ion composition using nonducted whistler observations on OGO 1 and Van Allen Probes

    Science.gov (United States)

    Sonwalkar, V. S.; Butler, J.; Reddy, A.

    2017-12-01

    wave instrument (e.g. OGO, ISEE 1, DE 1, POLAR, CLUSTER, Van Allen Probes). The method can be easily extended to make tomographic measurements of magnetospheric electron and ion density by analyzing a series of whistlers observed along the satellite orbit.

  13. A new standardless quantitative electron probe microanalysis technique applied to III-V compound semiconductors

    International Nuclear Information System (INIS)

    Zangalis, K.P.; Christou, A.

    1982-01-01

    The present paper introduces a new standardless quantitative scheme for off-line electron microprobe analysis applications. The analysis is based on standard equations of the type Isub(i)=Csub(i)fsub(ZAF)βsub(i) and is specifically suitable for compound semiconductors. The roots to the resultant nth-degree polynomial are the unknown concentrations. Methods for computing Csub(i) when coefficients βsub(i) are unknown are also outlined. Applications of standardless analysis to GaAs and InP specimens are compared with results obtained by Auger electron spectroscopy and quantitative electron probe analysis with standards. (Auth.)

  14. Dynamics of valence-shell electrons and nuclei probed by strong-field holography and rescattering

    Science.gov (United States)

    Walt, Samuel G.; Bhargava Ram, Niraghatam; Atala, Marcos; Shvetsov-Shilovski, Nikolay I; von Conta, Aaron; Baykusheva, Denitsa; Lein, Manfred; Wörner, Hans Jakob

    2017-01-01

    Strong-field photoelectron holography and laser-induced electron diffraction (LIED) are two powerful emerging methods for probing the ultrafast dynamics of molecules. However, both of them have remained restricted to static systems and to nuclear dynamics induced by strong-field ionization. Here we extend these promising methods to image purely electronic valence-shell dynamics in molecules using photoelectron holography. In the same experiment, we use LIED and photoelectron holography simultaneously, to observe coupled electronic-rotational dynamics taking place on similar timescales. These results offer perspectives for imaging ultrafast dynamics of molecules on femtosecond to attosecond timescales. PMID:28643771

  15. Electron scattering times in ZnO based polar heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Falson, J., E-mail: j.falson@fkf.mpg.de [Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Tokyo 113-8656 (Japan); Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561 (Japan); Max Planck Institute for Solid State Research, D-70569 Stuttgart (Germany); Kozuka, Y. [Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Tokyo 113-8656 (Japan); Smet, J. H. [Max Planck Institute for Solid State Research, D-70569 Stuttgart (Germany); Arima, T. [Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Tsukazaki, A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency (JST), Tokyo 102-0075 (Japan); Kawasaki, M. [Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Tokyo 113-8656 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)

    2015-08-24

    The remarkable historic advances experienced in condensed matter physics have been enabled through the continued exploration and proliferation of increasingly richer and cleaner material systems. In this work, we report on the scattering times of charge carriers confined in state-of-the-art MgZnO/ZnO heterostructures displaying electron mobilities in excess of 10{sup 6} cm{sup 2}/V s. Through an examination of low field quantum oscillations, we obtain the effective mass of charge carriers, along with the transport and quantum scattering times. These times compare favorably with high mobility AlGaAs/GaAs heterostructures, suggesting the quality of MgZnO/ZnO heterostructures now rivals that of traditional semiconductors.

  16. Elastic and inelastic electron scattering on tensor polarized deuteron

    International Nuclear Information System (INIS)

    Zevakov, S.A.; Barkov, L.M.; Arenkhovel', Kh.

    2006-01-01

    The components T 20 and T 21 of the tensor analysis capability of the elastic electron scattering on deuteron are measured in the momentum transfer range of 8.4-21.6 fm -2 . The form factors of deuteron G C and G Q are defined in the momentum transfer range where the monopole charge form factor G C turns into zero. The preliminary measuring results of T 20 , T 21 and T 22 of the deuteron photodisintegration reaction in the photon energy range of 25-500 MeV and the proton departure angles equal to 20 deg-40 deg and 75 deg-105 deg are presented. The experimental results are compared with the theoretical predictions [ru

  17. Rotatable spin-polarized electron source for inverse-photoemission experiments

    International Nuclear Information System (INIS)

    Stolwijk, S. D.; Wortelen, H.; Schmidt, A. B.; Donath, M.

    2014-01-01

    We present a ROtatable Spin-polarized Electron source (ROSE) for the use in spin- and angle-resolved inverse-photoemission (SR-IPE) experiments. A key feature of the ROSE is a variable direction of the transversal electron beam polarization. As a result, the inverse-photoemission experiment becomes sensitive to two orthogonal in-plane polarization directions, and, for nonnormal electron incidence, to the out-of-plane polarization component. We characterize the ROSE and test its performance on the basis of SR-IPE experiments. Measurements on magnetized Ni films on W(110) serve as a reference to demonstrate the variable spin sensitivity. Moreover, investigations of the unoccupied spin-dependent surface electronic structure of Tl/Si(111) highlight the capability to analyze complex phenomena like spin rotations in momentum space. Essentially, the ROSE opens the way to further studies on complex spin-dependent effects in the field of surface magnetism and spin-orbit interaction at surfaces

  18. On the theory of elastic scattering of spin polarized electrons from ferromagnets

    International Nuclear Information System (INIS)

    Helman, J.S.

    1984-01-01

    The first Born approximation supposedly inadequate for dealing with elastic scattering of spin polarized electrons on ferromagnets is reconsidered. It is found that when used in conjunction with a spin dependent pseudopotential, it can describe the gross features of the ansisotropy. (Author) [pt

  19. On the theory of elastic scattering of spin polarized electrons from ferromagnets

    International Nuclear Information System (INIS)

    Helman, J.S.; Baltenspenger, W.

    1984-01-01

    The first Born approximation supposedly inadequate for dealing with the elastic scattering of spin polarized electrons on ferromagnets is reconsidered. It is found that when used in conjunction with a spin dependent pseudo-potential, it can describe the gross features of the anisotropy. (author) [pt

  20. A high power gain switched diode laser oscillator and amplifier for the CEBAF polarized electron injector

    International Nuclear Information System (INIS)

    Poelker, M.; Hansknecht, J.

    1996-01-01

    The photocathode in the polarized electron source at Jefferson Lab is illuminated with pulsed laser light from a gain switched diode laser and diode optical amplifier. Laser pulse repetition rates up to 2,000 MHz, optical pulsewidths between 31 and 123 ps, and average power > 100 mW are demonstrated. The laser system is highly reliable and completely remotely controlled

  1. Coalescence of two polarized photons with antiparallel momenta into one on an electron

    International Nuclear Information System (INIS)

    Galynskii, M.V.

    1989-01-01

    The matrix elements have been calculated for the coalescence of two photons with antiparallel momenta and equal frequencies into one on an electron. An explicit expression for the differential probability for the process, with allowance for the polarization of all the particles, has been obtained in the nonrelativistic approximation

  2. Progress on the design of the polarized Medium-energy Electron Ion Collider at JLAB

    Energy Technology Data Exchange (ETDEWEB)

    Lin, F.; Bogacz, A.; Brindza, P.; Camsonne, A.; Daly, E.; Derbenev, Ya. S.; Douglas, D.; Ent, R.; Gaskell, D.; Geng, R.; Grames, J.; Guo, J.; Harwood, L.; Hutton, A.; Jordan, K.; Kimber, A.; Krafft, G.; Li, R.; Michalski, T.; Morozov, V. S.; Nadel-Turonski, P.; /Jefferson Lab /Argonne /DESY /Moscow , Inst. Phys. Tech., Dolgoprydny /Dubna, JINR /Northern Illinois U. /Old Doominion U. /Novosibirsk, GOO Zaryad /SLAC /Texas A-M

    2015-07-14

    The Medium-energy Electron Ion Collider (MEIC) at JLab is designed to provide high luminosity and high polarization needed to reach new frontiers in the exploration of nuclear structure. The luminosity, exceeding 1033 cm-2s-1 in a broad range of the center-of-mass (CM) energy and maximum luminosity above 1034 cm-2s-1, is achieved by high-rate collisions of short small-emittance low-charge bunches made possible by high-energy electron cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3He) can be easily preserved and manipulated due to the unique figure-8 shape of the collider rings. A fully consistent set of parameters have been developed considering the balance of machine performance, required technical development and cost. This paper reports recent progress on the MEIC accelerator design including electron and ion complexes, integrated interaction region design, figure-8-ring-based electron and ion polarization schemes, RF/SRF systems and ERL-based high-energy electron cooling. Luminosity performance is also presented for the MEIC baseline design.

  3. Plasma diagnostics by electron guns and electric field probes on ISEE-1

    International Nuclear Information System (INIS)

    Pedersen, A.

    1982-01-01

    The use of electron guns to control the potential of a satellite with conductive surfaces is discussed with reference to the results of the ISEE-1 satellite experiment. The two electron guns carried by the satellite can emit electrons with energies up to 48 eV, and the emitted electron current has a maximum value of 0.5-1.0 mA. The satellite potential, with or without gun operation, can be measured with reference to one or two spherical electric field probes positioned on booms at a distance of 36 m from the satellite. The probes are biased with a negative current from a high-impedance source to be slightly positive (0.5-1.0 V) relative to the plasma, and the spacecraft is normally several volts more positive and can be further positively charged by operating the electron gun. Plasma diagnostics can be carried out by appropriate sweeps of gun currents and energy of emitted electrons to obtain information about density and characteristic energy of ambient electrons. 9 references

  4. Vacancy-induced ferromagnetism in ZnO probed by spin-polarized positron annihilation spectroscopy

    Science.gov (United States)

    Maekawa, Masaki; Abe, Hiroshi; Miyashita, Atsumi; Sakai, Seiji; Yamamoto, Shunya; Kawasuso, Atsuo

    2017-04-01

    We investigated the ferromagnetism of ZnO induced by oxygen implantation by using spin-polarized positron annihilation spectroscopy together with magnetization measurements. The magnetization measurements showed the appearance of ferromagnetism after oxygen implantation and its disappearance during post-implantation annealing at temperatures above 573 K. The Doppler broadening of annihilation radiation (DBAR) spectrum showed asymmetry upon field reversal after oxygen implantation. The obtained differential DBAR spectrum between positive and negative magnetic fields was well-explained with a theoretical calculation considering zinc vacancies. The disappearance of the field-reversal asymmetry of the DBAR spectrum as a result of annealing agreed with the observations of ferromagnetism by magnetization measurements. These results suggest the radiation-induced zinc vacancies to be the source of the observed ferromagnetism of ZnO.

  5. Probing the magnetic profile of diluted magnetic semiconductors using polarized neutron reflectivity.

    Science.gov (United States)

    Luo, X; Tseng, L T; Lee, W T; Tan, T T; Bao, N N; Liu, R; Ding, J; Li, S; Lauter, V; Yi, J B

    2017-07-24

    Room temperature ferromagnetism has been observed in the Cu doped ZnO films deposited under an oxygen partial pressure of 10 -3 and 10 -5 torr on Pt (200 nm)/Ti (45 nm)/Si (001) substrates using pulsed laser deposition. Due to the deposition at relatively high temperature (873 K), Cu and Ti atoms diffuse to the surface and interface, which significantly affects the magnetic properties. Depth sensitive polarized neutron reflectometry method provides the details of the composition and magnetization profiles and shows that an accumulation of Cu on the surface leads to an increase in the magnetization near the surface. Our results reveal that the presence of the copper at Zn sites induces ferromagnetism at room temperature, confirming intrinsic ferromagnetism.

  6. Electron magnetic chiral dichroism in CrO2 thin films using monochromatic probe illumination in a transmission electron microscope

    International Nuclear Information System (INIS)

    Loukya, B.; Zhang, X.; Gupta, A.; Datta, R.

    2012-01-01

    Electron magnetic chiral dichroism (EMCD) has been studied in CrO 2 thin films (with (100) and (110) growth orientations on TiO 2 substrates) using a gun monochromator in an aberration corrected transmission electron microscope operating at 300 kV. Excellent signal-to-noise ratio is obtained at spatial resolution ∼10 nm using a monochromatic probe as compared to conventional parallel illumination, large area convergent beam electron diffraction and scanning transmission electron microscopy techniques of EMCD. Relatively rapid exposure using mono probe illumination enables collection of EMCD spectra in total of 8–9 min in energy filtered imaging mode for a given Cr L 2,3 energy scan (energy range ∼35 eV). We compared the EMCD signal obtained by extracting the Cr L 2,3 spectra under three beam diffraction geometry of two different reciprocal vectors (namely g=110 and 200) and found that the g=200 vector enables acquisition of excellent EMCD signal from relatively thicker specimen area due to the associated larger extinction distance. Orbital to spin moment ratio has been calculated using EMCD sum rules for 3d elements and dichroic spectral features associated with CrO 2 are compared and discussed with XMCD theoretical spectra. - Highlights: ► Electron magnetic circular dichroism (EMCD) of CrO 2 thin film with two different orientations. ► Improved EMCD signal with Gun monochromator illumination. ► Improved EMCD signal with higher g vector.

  7. Radiative electron rearrangement and polarization in target K x-ray spectra

    International Nuclear Information System (INIS)

    Jamison, K.A.

    1978-01-01

    Two topics in the atomic physics of ion-atom collisions are studied. The first is an investigation of a free-atom decay process that is shown to be a two-electron one-photon decay. This two-electron decay requires an initial state with multiple inner-shell vacancies that has a high probability of creation in ion-atom collisions. Because this decay promotes one electron to a higher shell while allowing the other to fall to a lower shell, it is referred to as radiative electron rearrangement (RER). The investigation of this process includes the experimental study of the x-ray spectra region approx. 150 eV below the characteristic Kα 1 2 target radiation in third period elements when bombarded by various ion beams in the energy range 1 to 2 MeV/amu. Theoretical calculations of the transition energies, line strengths, and line widths are performed to verify the origin of the RER lines. The second topic of consideration is the study of the polarization of Kα satellite radiation from targets of Al and Si. It is shown that the polarization, which is observed experimentally with a curved-crystal polarimeter, is due to the nonstatistical population of the magnetic substates created in specific ion-atom collisions. Further, the polarization of the RER lines is studied. The connection between the polarization of the normal Kα satellite radiation and the polarization of the RER lines adds final proof to their origin as two-electron one-photon transitions

  8. Probing the electronic structure of redox species and direct determination of intrinsic reorganization energies of electron transfer reactions

    International Nuclear Information System (INIS)

    Wang, Xue-Bin; Wang, Lai-Sheng

    2000-01-01

    An experimental technique capable of directly determining the intrinsic reorganization energies of bimolecular electron transfer reactions is described. Appropriate solution phase redox species are prepared in the gas phase using electrospray ionization and probed using photodetachment spectroscopy. Five metal complex anions involved in the Fe 2+ -Fe 3+ redox couple are investigated and the intramolecular reorganization energies are measured directly from spectral features due to removing the most loosely bound 3d electron from the Fe(II)-complexes. The photodetachment spectra also yield electronic structure information about the Fe 2+ -Fe 3+ redox couple and provide a common electronic structure origin for the reducing capability of the Fe(II)-complexes, the most common redox reagents. (c) 2000 American Institute of Physics

  9. Probing the Magnetic Field Structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Gold, Roman; McKinney, Jonathan C. [Department of Physics and Joint Space-Science Institute, University of Maryland, College Park, MD 20742 (United States); Johnson, Michael D.; Doeleman, Sheperd S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2017-03-10

    Magnetic fields are believed to drive accretion and relativistic jets in black hole accretion systems, but the magnetic field structure that controls these phenomena remains uncertain. We perform general relativistic (GR) polarized radiative transfer of time-dependent three-dimensional GR magnetohydrodynamical simulations to model thermal synchrotron emission from the Galactic Center source Sagittarius A* (Sgr A*). We compare our results to new polarimetry measurements by the Event Horizon Telescope (EHT) and show how polarization in the visibility (Fourier) domain distinguishes and constrains accretion flow models with different magnetic field structures. These include models with small-scale fields in disks driven by the magnetorotational instability as well as models with large-scale ordered fields in magnetically arrested disks. We also consider different electron temperature and jet mass-loading prescriptions that control the brightness of the disk, funnel-wall jet, and Blandford–Znajek-driven funnel jet. Our comparisons between the simulations and observations favor models with ordered magnetic fields near the black hole event horizon in Sgr A*, though both disk- and jet-dominated emission can satisfactorily explain most of the current EHT data. We also discuss how the black hole shadow can be filled-in by jet emission or mimicked by the absence of funnel jet emission. We show that stronger model constraints should be possible with upcoming circular polarization and higher frequency (349 GHz) measurements.

  10. Modeling of polarization phenomena due to RF sheaths and electron beams in magnetized plasma

    International Nuclear Information System (INIS)

    Faudot, E.

    2005-01-01

    This work investigates the problematic of hot spots induced by accelerated particle fluxes in tokamaks. It is shown that the polarization due to sheaths in the edge plasma in which an electron beam at a high level of energy is injected, can reach several hundreds volts and thus extend the deposition area. The notion of obstructed sheath is introduced and explains the acceleration of energy deposition by the decreasing of the sheath potential. Then, a 2-dimensional fluid modeling of flux tubes in front of ICRF antennae allows us to calculate the rectified potentials taking into account RF polarization currents transverse to magnetic field lines. The 2-dimensional fluid code designed validates the analytical results which show that the DC rectified potential is 50% greater with polarization currents than without. Finally, the simultaneous application of an electron beam and a RF potential reveals that the potentials due to each phenomenon are additives when RF potential is much greater than beam polarization. The density depletion of polarized flux tubes in 2-dimensional PIC (particles in cells) simulations is characterized but not yet explained. (author)

  11. Deep inelastic scattering of polarized electrons by polarized 3 He and the study of the neutron spin structure

    International Nuclear Information System (INIS)

    Arnold, R.G.; Bosted, P.E.; Dunne, J.; Fellbaum, J.; Keppel, C.; Rock, S.E.; Spengos, M.; Szalata, Z.M.; White, J.L.; Breton, V.; Fonvieille, H.; Roblin, Y.; Shapiro, G.; Hughes, E.W.; Borel, H.; Lombard-Nelsen, R.M.; Marroncle, J.; Morgenstern, J.; Staley, F.; Terrien, Y.; Anthony, P.L.; Dietrich, F.S.; Chupp, T.E.; Smith, T.; Thompson, A.K.; Kuhn, S.E.; Cates, G.D.; Middleton, H.; Newbury, N.R.; Anthony, P.L.; Gearhart, R.; Hughes, E.W.; Maruyama, T.; Meyer, W.; Petratos, G.G.; Pitthan, R.; Rokni, S.H.; Stuart, L.M.; White, J.L.; Woods, M.; Young, C.C.; Erbacher, R.; Kawall, D.; Kuhn, S.E.; Meziani, Z.E.; Holmes, R.; Souder, P.A.; Xu, J.; Meziani, Z.E.; Band, H.R.; Johnson, J.R.; Maruyama, T.; Prepost, R.; Zapala, G.

    1996-01-01

    The neutron longitudinal and transverse asymmetries A 1 n and A 2 n have been extracted from deep inelastic scattering of polarized electrons by a polarized 3 He target at incident energies of 19.42, 22.66 and 25.51 GeV. The measurement allows for the determination of the neutron spin structure functions g 1 n (x, Q 2 ) and g 2 n (x, Q 2 ) over the range 0.03 2 of 2 (GeV/c) 2 . The data are used for the evaluation of the Ellis-Jaffe and Bjorken sum rules. The neutron spin structure function g 1 n (x, Q 2 ) is small and negative within the range of our measurement, yielding an integral ∫ 0.03 0.6 g 1 n (x)dx - 0.028 ± 0.006 (stat) ± 0.006 (syst). Assuming Regge behavior at low x, we extract Γ 1 n ∫ 0 1 g 1 n (x)dx = - 0.031 ± 0.006 (stat) ± 0.009 (syst). Combined with previous proton integral results from SLAC experiment E143, we find Γ 1 p - Γ 1 n = 0.160 ± 0.015 in agreement with the Bjorken sum rule prediction Γ 1 p - Γ 1 p 0.176 ± 0.008 at a Q 2 value of 3 (GeV/c) 2 evaluated using α s 0.32 ± 0.05. (authors)

  12. Light-free magnetic resonance force microscopy for studies of electron spin polarized systems

    International Nuclear Information System (INIS)

    Pelekhov, Denis V.; Selcu, Camelia; Banerjee, Palash; Chung Fong, Kin; Chris Hammel, P.; Bhaskaran, Harish; Schwab, Keith

    2005-01-01

    Magnetic resonance force microscopy is a scanned probe technique capable of three-dimensional magnetic resonance imaging. Its excellent sensitivity opens the possibility for magnetic resonance studies of spin accumulation resulting from the injection of spin polarized currents into a para-magnetic collector. The method is based on mechanical detection of magnetic resonance which requires low noise detection of cantilever displacement; so far, this has been accomplished using optical interferometry. This is undesirable for experiments on doped silicon, where the presence of light is known to enhance spin relaxation rates. We report a non-optical displacement detection scheme based on sensitive microwave capacitive readout

  13. Strain-induced phase transition and electron spin-polarization in graphene spirals.

    Science.gov (United States)

    Zhang, Xiaoming; Zhao, Mingwen

    2014-07-16

    Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices.

  14. Quantum pump effect induced by a linearly polarized microwave in a two-dimensional electron gas.

    Science.gov (United States)

    Song, Juntao; Liu, Haiwen; Jiang, Hua

    2012-05-30

    A quantum pump effect is predicted in an ideal homogeneous two-dimensional electron gas (2DEG) that is normally irradiated by linearly polarized microwaves (MW). Without considering effects from spin-orbital coupling or the magnetic field, it is found that a polarized MW can continuously pump electrons from the longitudinal to the transverse direction, or from the transverse to the longitudinal direction, in the central irradiated region. The large pump current is obtained for both the low frequency limit and the high frequency case. Its magnitude depends on sample properties such as the size of the radiated region, the power and frequency of the MW, etc. Through the calculated results, the pump current should be attributed to the dominant photon-assisted tunneling processes as well as the asymmetry of the electron density of states with respect to the Fermi energy.

  15. Correlations and polarization in electronic and atomic collisions and (e,2e) reactions

    International Nuclear Information System (INIS)

    Teubner, P.J.O.; Weigold, E.

    1992-01-01

    This volume contains the invited papers presented at the Sixth International Symposium on Correlations and Polarization in Electronic and Atomic collisions and (e,2e) Reactions held at Flinders University, Adelaide, Australia from 18-21 July, 1991. This symposium was a satellite meeting to the XVII International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC) held in Brisbane, Australia. It follows a tradition of satellite meetings on (e,2e) collisions and on correlation and polarization in electronic and atomic collisions held in association with previous ICPEACs. The subject matter of this symposium covered that of the previous meeting at Hoboken, USA (1989) on correlation and polarization phenomena as well as that of the previous meeting at the University of Maryland (1989) on (e,2e) collisions. In addition it extended the scope to include some discussion of (e,3e), (γ,eγ) and (γ,2γ) coincidence measurements. The discussion of the current rapid advances in coincidence experiments, correlations and polarization measurements and related theoretical developments brought together 100 scientist from many countries with broad interdisciplinary backgrounds. The symposium stressed the common threads weaving through all these areas of research. (Author)

  16. Search for Time Reversal Violation in Neutron Decay: A Measurement of the Transverse Polarization of Electrons

    International Nuclear Information System (INIS)

    Bodek, K.; Kaczmarek, A.; Kistryn, St.; Kuzniak, M.; Zejma, J.; Pulut, J.; Kirch, K.; Bialek, A.; Kozela, A.; Ban, G.; Naviliat-Cuncic, O.; Gorel, P.; Beck, M.; Lindroth, A.; Severijns, N.; Stephan, E.; Czarnecki, A.

    2006-01-01

    A non-zero value of the R-correlation coefficient due to the e - polarization component, perpendicular to the plane spanned by the spin of the decaying neutron and the electron momentum, would signal a violation of time reversal symmetry and thus physics beyond the Standard Model. The value of the N-correlation coefficient, given by the transverse e - polarization component within that plane, is expected to be finite. The measurement of N serves as an important systematic check of the apparatus for the R-measurement. The first phase of data taking has been completed. Preliminary results from a limited data sample show no deviations from the Standard Model predictions

  17. Physics in the GeV region with polarized targets in electron storage rings

    International Nuclear Information System (INIS)

    Holt, R.J.

    1988-01-01

    There is evidence from the D(γ,p)n reaction that the meson-exchange model is failing in the GeV region. Surprisingly, it appears that the new (Dγ,p)n data favor the energy dependence of the nuclear chromodynamics model rather that of the meson-exchange model. Application of the polarization method to electron scattering studies is in its infancy, and it is potentially a very powerful technique. The internal target method coupled with laser-driven polarized targets should represent an important tool for nuclear physics

  18. Polarization effects in the reaction of charm baryon production on colliding electron-positron beams

    International Nuclear Information System (INIS)

    Rekalo, M.P.; Korzh, A.P.; Barannik, V.P.

    1980-01-01

    To calculate energy and angular distributions of various decay products of charm baAyons, which are prodUced in reactions on colliding e + e - beams, it is necessary to know the differential cross sections of the e + e - → C+anti C process which correspond to different polarized states of produced C and anti C (C - charm baryon). These differential cross sections are calculated for a single-photon mechanism with respect to the contribution of the anapole and electric dipole form factors of C-baryon. Polarizations of colliding electron-positron beams are taken into account in a full volume

  19. Electron Tunneling in Lithium Ammonia Solutions Probed by Frequency-Dependent Electron-Spin Relaxation Studies

    Science.gov (United States)

    Maeda, Kiminori; Lodge, Matthew T.J.; Harmer, Jeffrey; Freed, Jack H.; Edwards, Peter P.

    2012-01-01

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T1) and spin-spin (T2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multi-exponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1–10)×10−12 s over a temperature range 230–290K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a timescale of ca. 10−13 s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential

  20. Electron tunneling in lithium-ammonia solutions probed by frequency-dependent electron spin relaxation studies.

    Science.gov (United States)

    Maeda, Kiminori; Lodge, Matthew T J; Harmer, Jeffrey; Freed, Jack H; Edwards, Peter P

    2012-06-06

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T(1)) and spin-spin (T(2)) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multiexponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1-10) × 10(-12) s over a temperature range 230-290 K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a time scale of ∼10(-13) s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great

  1. Relativistic Electron Response to the Combined Magnetospheric Impact of a Coronal Mass Ejection Overlapping with a High-Speed Stream: Van Allen Probes Observations

    Science.gov (United States)

    Kanekal, S. G.; Baker, D. N.; Henderson, M. G.; Li, W.; Fennell, J. F.; Zheng, Y.; Richardson, I. G.; Jones, A.; Ali, A. F.; Elkington, S. R.; hide

    2015-01-01

    During early November 2013, the magnetosphere experienced concurrent driving by a coronal mass ejection (CME) during an ongoing high-speed stream (HSS) event. The relativistic electron response to these two kinds of drivers, i.e., HSS and CME, is typically different, with the former often leading to a slower buildup of electrons at larger radial distances, while the latter energizing electrons rapidly with flux enhancements occurring closer to the Earth. We present a detailed analysis of the relativistic electron response including radial profiles of phase space density as observed by both Magnetic Electron and Ion Sensor (MagEIS) and Relativistic Electron Proton Telescope instruments on the Van Allen Probes mission. Data from the MagEIS instrument establish the behavior of lower energy (electrons which span both intermediary and seed populations during electron energization. Measurements characterizing the plasma waves and magnetospheric electric and magnetic fields during this period are obtained by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probes, Search Coil Magnetometer and Flux Gate Magnetometer instruments on board Time History of Events and Macroscale Interactions during Substorms, and the low-altitude Polar-orbiting Operational Environmental Satellites. These observations suggest that during this time period, both radial transport and local in situ processes are involved in the energization of electrons. The energization attributable to radial diffusion is most clearly evident for the lower energy (electrons, while the effects of in situ energization by interaction of chorus waves are prominent in the higher-energy electrons.

  2. Probing electron acceleration and x-ray emission in laser-plasma accelerators

    International Nuclear Information System (INIS)

    Thaury, C.; Ta Phuoc, K.; Corde, S.; Brijesh, P.; Lambert, G.; Malka, V.; Mangles, S. P. D.; Bloom, M. S.; Kneip, S.

    2013-01-01

    While laser-plasma accelerators have demonstrated a strong potential in the acceleration of electrons up to giga-electronvolt energies, few experimental tools for studying the acceleration physics have been developed. In this paper, we demonstrate a method for probing the acceleration process. A second laser beam, propagating perpendicular to the main beam, is focused on the gas jet few nanosecond before the main beam creates the accelerating plasma wave. This second beam is intense enough to ionize the gas and form a density depletion, which will locally inhibit the acceleration. The position of the density depletion is scanned along the interaction length to probe the electron injection and acceleration, and the betatron X-ray emission. To illustrate the potential of the method, the variation of the injection position with the plasma density is studied

  3. Quantitative analysis of biological fluids by electron probe and X ray spectrometry

    International Nuclear Information System (INIS)

    Girod, Chantal

    1986-01-01

    In order to know the kidney normal operation and to have an insight on cellular transport mechanisms and hormonal regulations at the nephron level, a technique based on the use of an electron probe has been developed for the elemental analysis of micro-volumes of biological fluids. This academic document reports applications of this technique on animals on which such fluids have been sampled at different levels of the nephron. As these samples are available in too small volumes to be dosed by conventional methods, they have been quantitatively analysed by using an electronic probe based analyser in order to determine concentrations of all elements with an atomic number greater than that of carbon. After a presentation of the implemented method and hardware, the author thus describes how an analysis is performed, and reports and discusses an example (analysis conditions, data acquisition, data processing, minimum detectable concentration, reasons for measurement scattering)

  4. Fluorescent probe studies of polarity and solvation within room temperature ionic liquids: a review.

    Science.gov (United States)

    Pandey, Shubha; Baker, Sheila N; Pandey, Siddharth; Baker, Gary A

    2012-09-01

    Ionic liquids display an array of useful and sometimes unconventional, solvent features and have attracted considerable interest in the field of green chemistry for the potential they hold to significantly reduce environmental emissions. Some of these points have a bearing on the chemical reactivity of these systems and have also generated interest in the physical and theoretical aspects of solvation in ionic liquids. This review presents an introduction to the field of ionic liquids, followed by discussion of investigations into the solvation properties of neat ionic liquids or mixed systems including ionic liquids as a major or minor component. The ionic liquid based multicomponent systems discussed are composed of other solvents, other ionic liquids, carbon dioxide, surfactants or surfactant solutions. Although we clearly focus on fluorescence spectroscopy as a tool to illuminate ionic liquid systems, the issues discussed herein are of general relevance to discussions of polarity and solvent effects in ionic liquids. Transient solvation measurements carried out by means of time-resolved fluorescence measurements are particularly powerful for their ability to parameterize the kinetics of the solvation process in ionic liquids and are discussed as well.

  5. New measurements in plutonium L X ray emission spectrum using an electron probe micro-analyser

    International Nuclear Information System (INIS)

    Bobin, J.L.; Despres, J.

    1966-01-01

    Further studies by means of an electron-probe micro-analyser, allowed report CEA-R--1798 authors to set up a larger plutonium X ray spectrum table. Measurements of plutonium L II and L III levels excitation potentials have also been achieved. Some remarks about apparatus performance data (such as spectrograph sensibility, resolving power and accuracy) will be found in the appendix. (authors) [fr

  6. Nonlocal Response of Metallic Nanospheres Probed by Light, Electrons, and Atoms

    DEFF Research Database (Denmark)

    Christensen, Thomas; Yan, Wei; Raza, Søren

    2014-01-01

    Inspired by recent measurements on individual metallic nanospheres that cannot be explained with traditional classical electrodynamics, we theoretically investigate the effects of nonlocal response by metallic nanospheres in three distinct settings: atomic spontaneous emission, electron energy loss...... blueshifted surface plasmon but also an infinite series of bulk plasmons that have no counterpart in a local-response approximation. We show that these increasingly blueshifted multipole plasmons become spectrally more prominent at shorter probe-to-surface separations and for decreasing nanosphere radii...

  7. Probing flexible conformations in molecular junctions by inelastic electron tunneling spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Mingsen [Department of Physics, Guizhou University, Guiyang, 550025 (China); Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Institute of Applied Physics, Guizhou Normal College, Guiyang, 550018 (China); Ye, Gui; Jiang, Jun, E-mail: jiangj1@ustc.edu.cn [Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, 230026 (China); Cai, Shaohong, E-mail: caish@mail.gufe.edu.cn [Department of Physics, Guizhou University, Guiyang, 550025 (China); Guizhou Key Laboratory of Economic System Simulation, Guizhou University of Finance and Economics, Guiyang, 550004 (China); Sun, Guangyu [Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Institute of Applied Physics, Guizhou Normal College, Guiyang, 550018 (China)

    2015-01-15

    The probe of flexible molecular conformation is crucial for the electric application of molecular systems. We have developed a theoretical procedure to analyze the couplings of molecular local vibrations with the electron transportation process, which enables us to evaluate the structural fingerprints of some vibrational modes in the inelastic electron tunneling spectroscopy (IETS). Based on a model molecule of Bis-(4-mercaptophenyl)-ether with a flexible center angle, we have revealed and validated a simple mathematical relationship between IETS signals and molecular angles. Our results might open a route to quantitatively measure key geometrical parameters of molecular junctions, which helps to achieve precise control of molecular devices.

  8. Probing plasma wakefields using electron bunches generated from a laser wakefield accelerator

    Science.gov (United States)

    Zhang, C. J.; Wan, Y.; Guo, B.; Hua, J. F.; Pai, C.-H.; Li, F.; Zhang, J.; Ma, Y.; Wu, Y. P.; Xu, X. L.; Mori, W. B.; Chu, H.-H.; Wang, J.; Lu, W.; Joshi, C.

    2018-04-01

    We show experimental results of probing the electric field structure of plasma wakes by using femtosecond relativistic electron bunches generated from a laser wakefield accelerator. Snapshots of laser-driven linear wakes in plasmas with different densities and density gradients are captured. The spatiotemporal evolution of the wake in a plasma density up-ramp is recorded. Two parallel wakes driven by a laser with a main spot and sidelobes are identified in the experiment and reproduced in simulations. The capability of this new method for capturing the electron- and positron-driven wakes is also shown via 3D particle-in-cell simulations.

  9. Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse

    Directory of Open Access Journals (Sweden)

    J. Szlachetko

    2014-03-01

    Full Text Available Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10−18 s to femtoseconds (10−15 s and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS, we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.

  10. Plasma potential and electron temperature evaluated by ball-pen and Langmuir probes in the COMPASS tokamak

    Science.gov (United States)

    Dimitrova, M.; Popov, Tsv K.; Adamek, J.; Kovačič, J.; Ivanova, P.; Hasan, E.; López-Bruna, D.; Seidl, J.; Vondráček, P.; Dejarnac, R.; Stöckel, J.; Imríšek, M.; Panek, R.; the COMPASS Team

    2017-12-01

    The radial distributions of the main plasma parameters in the scrape-off-layer of the COMPASS tokamak are measured during L-mode and H-mode regimes by using both Langmuir and ball-pen probes mounted on a horizontal reciprocating manipulator. The radial profile of the plasma potential derived previously from Langmuir probes data by using the first derivative probe technique is compared with data derived using ball-pen probes. A good agreement can be seen between the data acquired by the two techniques during the L-mode discharge and during the H-mode regime within the inter-ELM periods. In contrast with the first derivative probe technique, the ball-pen probe technique does not require a swept voltage and, therefore, the temporal resolution is only limited by the data acquisition system. In the electron temperature evaluation, in the far scrape-off layer and in the limiter shadow, where the electron energy distribution is Maxwellian, the results from both techniques match well. In the vicinity of the last closed flux surface, where the electron energy distribution function is bi-Maxwellian, the ball-pen probe technique results are in agreement with the high-temperature components of the electron distribution only. We also discuss the application of relatively large Langmuir probes placed in parallel and perpendicularly to the magnetic field lines to studying the main plasma parameters. The results obtained by the two types of the large probes agree well. They are compared with Thomson scattering data for electron temperatures and densities. The results for the electron densities are compared also with the results from ASTRA code calculation of the electron source due to the ionization of the neutrals by fast electrons and the origin of the bi-Maxwellian electron energy distribution function is briefly discussed.

  11. Importance of polarization effects in electron impact single ionization of argon atom

    Energy Technology Data Exchange (ETDEWEB)

    Purohit, G., E-mail: g_vpurohit@yahoo.co [Department of Basic Sciences, School of Engineering, Sir Padampat Singhania University, Bhatewar, Udaipur 313 601 (India); Patidar, Vinod; Sud, K.K. [Department of Basic Sciences, School of Engineering, Sir Padampat Singhania University, Bhatewar, Udaipur 313 601 (India)

    2009-12-15

    We report the results of our calculations of triple differential cross section (TDCS) for electron impact single ionization (i.e. (e, 2e) processes) from the 3s shell of argon using a modified distorted wave Born approximation formalism by including correlation-polarization potential, which accounts for both correlation and polarization effects. We observe that DWBA formalism including polarization potential is able to reproduce most of the trends of experimental data and hence provide a future direction for further investigation of ionization process from the 3s shell of argon. We also compare our results with the available theoretical and experimental results. The present calculations significantly improve the agreement with the experimental results but still there are certain discrepancies, which is a matter of further investigation.

  12. Measurement of electron beam polarization from unstrained GaAs via two-photon photoemission

    Energy Technology Data Exchange (ETDEWEB)

    McCarter, J.L., E-mail: jlm2ar@virginia.edu [Department of Physics, University of Virginia, Charlottesville, VA 22901 (United States); Afanasev, A. [Department of Physics, The George Washington University, Washington, DC 20052 (United States); Gay, T.J. [Jorgensen Hall, University of Nebraska, Lincoln, NE 68588 (United States); Hansknecht, J. [Thomas Jefferson National Accelerator Facility, 12050 Jefferson Avenue, Suite 500, Newport News, VA 23606 (United States); Kechiantz, A. [Department of Physics, The George Washington University, Washington, DC 20052 (United States); Poelker, M. [Thomas Jefferson National Accelerator Facility, 12050 Jefferson Avenue, Suite 500, Newport News, VA 23606 (United States)

    2014-02-21

    Two-photon absorption of 1560 nm light was used to generate polarized electron beams from unstrained GaAs photocathodes of varying thickness: 625 μm, 0.32 μm, and 0.18 μm. For each photocathode, the degree of spin polarization of the photoemitted beam was less than 50%, contradicting earlier predictions based on simple quantum mechanical selection rules for spherically-symmetric systems but consistent with the more sophisticated model of Bhat et al. (Phys. Rev. B 71 (2005) 035209). Polarization via two-photon absorption was the highest from the thinnest photocathode sample and comparable to that obtained via one-photon absorption (using 778 nm light), with values 40.3±1.0% and 42.6±1.0%, respectively.

  13. Calculation and construction of a beam-transport system for polarized electrons

    International Nuclear Information System (INIS)

    Marschke, G.

    1987-09-01

    In the framework of the ELSA-SAPHIR project a transfer channel between ELSA and the large-space detector SAPHIR was calculated and constructed. Existing optical elements were modified corresponding to their application and the missing racks constructed and ordered for fabrication. Furthermore the vacuum system was designed as the whole as well as in the single components. Starting from the architectonic conditions and the optics to be realized the coordinates of the elements were calculated as preconditions fo the geodetic measurements and calibrations. It was shown that both for a polarized and for an unpolarized electron beam an optic was realized corresponding to the requirements up to an energy of 3.5 GeV. Under the given conditions, the applied method of the rotation of the polarization vector, and the geometrical preconditions up to 3.0 GeV also an acceptable longitudinal polarization was reached. (orig./HSI) [de

  14. Detection of an electron beam in a high density plasma via an electrostatic probe

    Science.gov (United States)

    Majeski, Stephen; Yoo, Jongsoo; Zweben, Stewart; Yamada, Masaaki; Ji, Hantao

    2017-10-01

    The perturbation in floating potential by an electron beam is detected by a 1D floating potential probe array to evaluate the use of an electron beam for magnetic field line mapping in the Magnetic Reconnection Experiment (MRX) plasma. The MRX plasma is relatively high density (1013 cm-3) and low temperature (5 eV). Beam electrons are emitted from a tungsten filament and are accelerated by a 200 V potential across the sheath. They stream along the magnetic field lines towards the probe array. The spatial electron beam density profile is assumed to be a Gaussian along the radial axis of MRX and the effective beam width is determined from the radial profile of the floating potential. The magnitude of the perturbation is in agreement with theoretical predictions and the location of the perturbation is also in agreement with field line mapping. In addition, no significant broadening of the electron beam is observed after propagation for tens of centimeters through the high density plasma. These results demonstrate that this method of field line mapping is, in principle, feasible in high density plasmas. This work is supported by the DOE Contract No. DE-AC0209CH11466.

  15. Effect of the anisotropy of the electron g-factor in spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong, Chittagong 4331 (Bangladesh); Gray, E. MacA. [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)

    2010-02-15

    Spin polarization in the presence of an external magnetic field and electric bias in quantum confined semiconductor structures has been studied by time- and polarization-resolved spectrometry. From measurements with angular variations of the magnetic field from the Voigt configuration (VC) it was found that both the frequency ({Omega}) and decay rate ({beta}) of the oscillatory component of the polarization increase with variation of the angle from the VC. Their dependences are discussed based on the electron spin dephasing related to the spread of the electron g-factor (g{sub e}) (i.e. unequal values of the longitudinal (g{sub e||}) and transverse (g{sub e}-perpendicular) components of g{sub e}) and the exchange interaction between the electron and hole spins. It is demonstrated that the increase in {Omega} upon deviation of the magnetic field from the VC relates to the anisotropy of g{sub e} (g{sub e||} and g{sub e}-perpendicular) resulting from the quantum confinement effect. However, the angular dependence on {beta} is related to the residual exchange interaction between the electron spin and rapidly relaxing hole spin.

  16. Development of high-performance alkali-hybrid polarized 3He targets for electron scattering

    Science.gov (United States)

    Singh, Jaideep T.; Dolph, P. A. M.; Tobias, W. A.; Averett, T. D.; Kelleher, A.; Mooney, K. E.; Nelyubin, V. V.; Wang, Yunxiao; Zheng, Yuan; Cates, G. D.

    2015-05-01

    Background: Polarized 3He targets have been used as effective polarized neutron targets for electron scattering experiments for over twenty years. Over the last ten years, the effective luminosity of polarized 3He targets based on spin-exchange optical pumping has increased by over an order of magnitude. This has come about because of improvements in commercially-available lasers and an improved understanding of the physics behind the polarization process. Purpose: We present the development of high-performance polarized 3He targets for use in electron scattering experiments. Improvements in the performance of polarized 3He targets, target properties, and operating parameters are documented. Methods: We utilize the technique of alkali-hybrid spin-exchange optical pumping to polarize the 3He targets. Spectrally narrowed diode lasers used for the optical pumping greatly improved the performance. A simulation of the alkali-hybrid spin-exchange optical pumping process was developed to provide guidance in the design of the targets. Data was collected during the characterization of 24 separate glass target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. Results: From the data obtained we made determinations of the so-called X -factors that quantify a temperature-dependent and as-yet poorly understood spin-relaxation mechanism that limits the maximum achievable 3He polarization to well under 100%. The presence of the X -factor spin-relaxation mechanism was clearly evident in our data. Good agreement between the simulation and the actual target performance was obtained by including details such as off-resonant optical pumping. Included in our results is a measurement of the K -3He spin-exchange rate coefficient kseK=(7.46 ±0.62 ) ×10-20cm3/s over the temperature range 503 K to 563 K. Conclusions: In order to achieve high performance under the operating conditions described in this paper

  17. Probing the Milky Way electron density using multi-messenger astronomy

    Science.gov (United States)

    Breivik, Katelyn; Larson, Shane

    2015-04-01

    Multi-messenger observations of ultra-compact binaries in both gravitational waves and electromagnetic radiation supply highly complementary information, providing new ways of characterizing the internal dynamics of these systems, as well as new probes of the galaxy itself. Electron density models, used in pulsar distance measurements via the electron dispersion measure, are currently not well constrained. Simultaneous radio and gravitational wave observations of pulsars in binaries provide a method of measuring the average electron density along the line of sight to the pulsar, thus giving a new method for constraining current electron density models. We present this method and assess its viability with simulations of the compact binary component of the Milky Way using the public domain binary evolution code, BSE. This work is supported by NASA Award NNX13AM10G.

  18. Measurement of Wake fields in Plasma by a Probing Electron Beam

    International Nuclear Information System (INIS)

    Kiselev, V.A.; Linnik, A.F.; Onishchenko, I.N.; Uskov, V.V.

    2006-01-01

    The device for measuring intensity of wakefield, excited in plasma by a sequence of bunches of relativistic electrons is presented. Field amplitude is determined by measuring deflection of a probing electron beam (10 keV, 50 μA, of 1 mm diameter), which is injected perpendicularly to a direction of bunches movement. Results of measurement of focusing radial wakefield excited in plasma of density 5 x 10 11 cm - 3 by a sequence of needle electron bunches (each bunch of length 10 mm, diameter 1.5 mm, energy 14 MeV, 2 x 10 9 electrons in bunch, number of bunches 1500) are given. The measured radial wakefield strength was 2.5 kV/cm

  19. Electron Paramagnetic Resonance Measurements of Reactive Oxygen Species by Cyclic Hydroxylamine Spin Probes.

    Science.gov (United States)

    Dikalov, Sergey I; Polienko, Yuliya F; Kirilyuk, Igor

    2018-05-20

    Oxidative stress contributes to numerous pathophysiological conditions such as development of cancer, neurodegenerative, and cardiovascular diseases. A variety of measurements of oxidative stress markers in biological systems have been developed; however, many of these methods are not specific, can produce artifacts, and do not directly detect the free radicals and reactive oxygen species (ROS) that cause oxidative stress. Electron paramagnetic resonance (EPR) is a unique tool that allows direct measurements of free radical species. Cyclic hydroxylamines are useful and convenient molecular probes that readily react with ROS to produce stable nitroxide radicals, which can be quantitatively measured by EPR. In this work, we critically review recent applications of various cyclic hydroxylamine spin probes in biology to study oxidative stress, their advantages, and the shortcomings. Recent Advances: In the past decade, a number of new cyclic hydroxylamine spin probes have been developed and their successful application for ROS measurement using EPR has been published. These new state-of-the-art methods provide improved selectivity and sensitivity for in vitro and in vivo studies. Although cyclic hydroxylamine spin probes EPR application has been previously described, there has been lack of translation of these new methods into biomedical research, limiting their widespread use. This work summarizes "best practice" in applications of cyclic hydroxylamine spin probes to assist with EPR studies of oxidative stress. Additional studies to advance hydroxylamine spin probes from the "basic science" to biomedical applications are needed and could lead to better understanding of pathological conditions associated with oxidative stress. Antioxid. Redox Signal. 28, 1433-1443.

  20. Pitch Angle Scattering of Upgoing Electron Beams in Jupiter's Polar Regions by Whistler Mode Waves

    Science.gov (United States)

    Elliott, S. S.; Gurnett, D. A.; Kurth, W. S.; Clark, G.; Mauk, B. H.; Bolton, S. J.; Connerney, J. E. P.; Levin, S. M.

    2018-02-01

    The Juno spacecraft's Jupiter Energetic-particle Detector Instrument has observed field-aligned, unidirectional (upgoing) electron beams throughout most of Jupiter's entire polar cap region. The Waves instrument detected intense broadband whistler mode emissions occurring in the same region. In this paper, we investigate the pitch angle scattering of the upgoing electron beams due to interactions with the whistler mode waves. Profiles of intensity versus pitch angle for electron beams ranging from 2.53 to 7.22 Jovian radii show inconsistencies with the expected adiabatic invariant motion of the electrons. It is believed that the observed whistler mode waves perturb the electron motion and scatter them away from the magnetic field line. The diffusion equation has been solved by using diffusion coefficients which depend on the magnetic intensity of the whistler mode waves.

  1. Understanding the effects of electronic polarization and delocalization on charge-transport levels in oligoacene systems

    KAUST Repository

    Sutton, Christopher; Tummala, Naga Rajesh; Kemper, Travis; Aziz, Saadullah G.; Sears, John; Coropceanu, Veaceslav; Bredas, Jean-Luc

    2017-01-01

    Electronic polarization and charge delocalization are important aspects that affect the charge-transport levels in organic materials. Here, using a quantum mechanical/ embedded-charge (QM/EC) approach based on a combination of the long-range corrected omega B97X-D exchange-correlation functional (QM) and charge model 5 (CM5) point-charge model (EC), we evaluate the vertical detachment energies and polarization energies of various sizes of crystalline and amorphous anionic oligoacene clusters. Our results indicate that QM/EC calculations yield vertical detachment energies and polarization energies that compare well with the experimental values obtained from ultraviolet photoemission spectroscopy measurements. In order to understand the effect of charge delocalization on the transport levels, we considered crystalline naphthalene systems with QM regions including one or five-molecules. The results for these systems show that the delocalization and polarization effects are additive; therefore, allowing for electron delocalization by increasing the size of the QM region leads to the additional stabilization of the transport levels. Published by AIP Publishing.

  2. Understanding the effects of electronic polarization and delocalization on charge-transport levels in oligoacene systems

    KAUST Repository

    Sutton, Christopher

    2017-06-13

    Electronic polarization and charge delocalization are important aspects that affect the charge-transport levels in organic materials. Here, using a quantum mechanical/ embedded-charge (QM/EC) approach based on a combination of the long-range corrected omega B97X-D exchange-correlation functional (QM) and charge model 5 (CM5) point-charge model (EC), we evaluate the vertical detachment energies and polarization energies of various sizes of crystalline and amorphous anionic oligoacene clusters. Our results indicate that QM/EC calculations yield vertical detachment energies and polarization energies that compare well with the experimental values obtained from ultraviolet photoemission spectroscopy measurements. In order to understand the effect of charge delocalization on the transport levels, we considered crystalline naphthalene systems with QM regions including one or five-molecules. The results for these systems show that the delocalization and polarization effects are additive; therefore, allowing for electron delocalization by increasing the size of the QM region leads to the additional stabilization of the transport levels. Published by AIP Publishing.

  3. Circularly polarized harmonic generation by intense bicircular laser pulses: electron recollision dynamics and frequency dependent helicity

    Science.gov (United States)

    Bandrauk, André D.; Mauger, François; Yuan, Kai-Jun

    2016-12-01

    Numerical solutions of time-dependent Schrödinger equations for one and two electron cyclic molecules {{{H}}}nq+ exposed to intense bichromatic circularly polarized laser pulses of frequencies {ω }1 and {ω }2, such that {ω }1/{ω }2={n}1/{n}2 (integer) produce circularly polarized high order harmonics with a cut-off recollision maximum energy at and greater than the linear polarization law (in atomic units) {N}m{ω }1={I}p+3.17{U}p, where I p is the ionization potential and {U}p={(2{E}0)}2/4{ω }2 is the ponderomotive energy defined by the field E 0 (intensity I={{cE}}02/8π ) from each pulse and mean frequency ω =({ω }1+{ω }2)/2 . An electron recollision model in a rotating frame at rotating frequency {{Δ }}ω =({ω }1-{ω }2)/2 predicts this simple result as a result of recollision dynamics in a combination of bichromatic circularly polarized pulses. The harmonic helicities and their intensities are shown to depend on compatible symmetries of the net pulse electric fields with that of the molecules.

  4. Improved Electron Yield and Spin-Polarization from III-V Photocathodes via Bias Enhanced Carrier Drift: Final Report

    International Nuclear Information System (INIS)

    Mulhollan, Gregory A.

    2006-01-01

    In this DOE STTR program, Saxet Surface Science, with the Stanford Linear Accelerator Center as partner, designed, built and tested photocathode structures such that optimal drift-enhanced spin-polarization from GaAs based photoemitters was achieved with minimal bias supply requirements. The forward bias surface grid composition was optimized for maximum polarization and yield, together with other construction parameters including doping profile. This program has culminated in a cathode bias structure affording increased electron spin polarization when applied to III-V based photocathodes. The optimized bias structure has been incorporated into a cathode mounting and biasing design for use in a polarized electron gun.

  5. Investigations of the physical properties of photoemission polarized electron sources for accelerator applications

    International Nuclear Information System (INIS)

    Dunham, B.M.

    1993-01-01

    This experiment measured the polarization and quantum efficiency as a function of wavelength for the chalcopyrite semiconductor Zn (Ge 0.7 Si 0.3 )As 2 . Also, the onset of space charge growth of a 100 keV electron beam passing through the Illinois/CEBAF polarized electron injection system was studied by measuring the beam emittance as a function of current. Finally the thermal properties of GaAs were investigated by measuring the beam emittance as functions of the excitation laser wavelength and the laser spot size. The experiments were performed of Zn(Ge 0.7 Si 0.3 )As 2 was measured to be ∼19%, much lower than the expected 100%. Also, the expected emittance as a function of current was measured and the onset of space charge effects was found to be ∼0.5 mA, much lower than predicted by the electron gun design program EGUN. Finally, the effective transverse thermal energy of the electrons emitted from GaAs at 100 keV as a function of excitation wavelength was measured by a new method for low beam currents. The electron thermal energy for wavelengths between 840 and 633 nm was found to be ∼33 meV, a factor of 3 lower than for a thermionic electron gun. It was found to increase sharply for photon wavelengths less than 633 nm

  6. Electron acceleration by a radially polarized laser pulse during ionization of low density gases

    Directory of Open Access Journals (Sweden)

    Kunwar Pal Singh

    2011-03-01

    Full Text Available The acceleration of electrons by a radially polarized intense laser pulse has been studied. The axial electric field of the laser is responsible for electron acceleration. The axial electric field increases with decreasing laser spot size; however, the laser pulse gets defocused sooner for smaller values and the electrons do not experience high electric field for long, reducing the energy they can reach. The electron remains confined in the electric field of the laser for longer and the electron energy peaks for the normalized laser spot size nearly equal to the normalized laser intensity parameter. Electron energy peaks for initial laser phase ϕ_{0}=π due to accelerating laser phase and decreases with transverse initial position of the electrons. The energy and angle of the emittance spectrum of the electrons generated during ionization of krypton and argon at low densities have been obtained and a right choice of laser parameters has been suggested to obtain high energy quasimonoenergetic collimated electron beams. It has been found that argon is more suitable than krypton to obtain high energy electron beams due to higher ionization potential of inner shells for the former.

  7. Deep inelastic scattering of polarized electrons by polarized {sup 3} He and the study of the neutron spin structure

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, R G; Bosted, P E; Dunne, J; Fellbaum, J; Keppel, C; Rock, S E; Spengos, M; Szalata, Z M; White, J L [Washington State Univ., Pullman, WA (United States); Breton, V; Fonvieille, H; Roblin, Y [Clermont-Ferrand-2 Univ., 63 - Aubiere (France); Shapiro, G [Lawrence Berkeley Lab., CA (United States); Hughes, E W [California Inst. of Tech., Pasadena, CA (United States); Borel, H; Lombard-Nelsen, R M; Marroncle, J; Morgenstern, J; Staley, F; Terrien, Y [CEA Centre d` Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d` Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l` Instrumentation Associee; Petratos, G G [Kent State Univ., OH (United States); Anthony, P L; Dietrich, F S [Lawrence Livermore National Lab., CA (United States); Chupp, T E; Smith, T [Michigan Univ., Dearborn, MI (United States); Thompson, A K [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Kuhn, S E [Norfolk State Univ., VA (United States); Cates, G D; Middleton, H; Newbury, N R [Princeton Univ., NJ (United States); Anthony, P L; Gearhart, R; Hughes, E W; Maruyama, T; Meyer, W; Petratos, G G; Pitthan, R; Rokni, S H; Stuart, L M; White, J L; Woods, M; Young, C C [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Erbacher, R; Kawall, D; Kuhn, S E; Meziani, Z E [Stanford Univ., CA (United States); Holmes, R; Souder, P A; Xu, J [Syracuse Univ., NY (United States); Meziani, Z E [Temple Univ., Philadelphia, PA (United States); Band, H R; Johnson, J R; Maruyama, T; Prepost, R; Zapala, G [Wisconsin Univ., Madison, WI (United States)

    1997-12-31

    The neutron longitudinal and transverse asymmetries A{sub 1}{sup n} and A{sub 2}{sup n} have been extracted from deep inelastic scattering of polarized electrons by a polarized {sup 3}He target at incident energies of 19.42, 22.66 and 25.51 GeV. The measurement allows for the determination of the neutron spin structure functions g{sub 1}{sup n}(x, Q{sup 2}) and g{sub 2}{sup n} (x, Q{sup 2}) over the range 0.03 < x < 0.6 at an average Q{sup 2} of 2 (GeV/c){sup 2}. The data are used for the evaluation of the Ellis-Jaffe and Bjorken sum rules. The neutron spin structure function g{sub 1}{sup n} (x, Q{sup 2}) is small and negative within the range of our measurement, yielding an integral {integral}{sub 0.03}{sup 0.6} g{sub 1}{sup n} (x)dx - 0.028 {+-} 0.006 (stat) {+-} 0.006 (syst). Assuming Regge behavior at low x, we extract {Gamma}{sub 1}{sup n} {integral}{sub 0}{sup 1} g{sub 1}{sup n} (x)dx = - 0.031 {+-} 0.006 (stat) {+-} 0.009 (syst). Combined with previous proton integral results from SLAC experiment E143, we find {Gamma}{sub 1}{sup p} - {Gamma}{sub 1}{sup n} = 0.160 {+-} 0.015 in agreement with the Bjorken sum rule prediction {Gamma}{sub 1}{sup p} - {Gamma}{sub 1}{sup p} 0.176 {+-} 0.008 at a Q{sup 2} value of 3 (GeV/c){sup 2} evaluated using {alpha}{sub s} 0.32 {+-} 0.05. (authors). 109 refs.

  8. Production of charm and beauty in e+e- with polarized electron beam

    International Nuclear Information System (INIS)

    Su, D.

    1995-09-01

    The test of the Standard Model through the measurements of Z 0 to fermion couplings can benefit from much enhanced sensitivity by using longitudinally polarized electron beams. This report reviews preliminary electroweak measurements from SLD on heavy quark production at the Z 0 , using 150,000 hadronic Z 0 decays accumulated during the 93-95 runs with high electron beam polarization. The parity violating parameters A b and A c of the Zbb and Zcc couplings are measured directly from the left-right forward-backward asymmetries. A measurement of R b with a lifetime double tag and a summary of the preliminary measurement of A LR from the 93-95 SLD data are also included in this report

  9. Classical and quantum theories of the polarization bremsstrahlung in the local electron density model

    International Nuclear Information System (INIS)

    Astapenko, V.A.; Bureeva, L.A.; Lisitsa, V.S.

    2000-01-01

    Classical and quantum theories of polarization bremsstrahlung in a statistical (Thomas-Fermi) potential of complex atoms and ions are developed. The basic assumptions of the theories correspond to the approximations employed earlier in classical and quantum calculations of ordinary bremsstrahlung in a static potential. This makes it possible to study on a unified basis the contribution of both channels in the radiation taking account of their interference. The classical model makes it possible to obtain simple universal formulas for the spectral characteristics of the radiation. The theory is applied to electrons with moderate energies, which are characteristic for plasma applications, specifically, radiation from electrons on the argon-like ion KII at frequencies close to its ionization potential. The computational results show the importance of taking account of the polarization channel of the radiation for plasma with heavy ions

  10. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    International Nuclear Information System (INIS)

    Figuera, Juan de la; Vergara, Lucía; N'Diaye, Alpha T.; Quesada, Adrian; Schmid, Andreas K.

    2013-01-01

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along directions. ► Magnetic domain wall structures include wide Néel-caps

  11. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); Vergara, Lucía [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); N' Diaye, Alpha T. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Quesada, Adrian [Instituto de Cerámica y Vidrio, CSIC, Calle Kelsen 5, 28049, Madrid (Spain); Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-07-15

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along <110> directions. ► Magnetic domain wall structures include wide Néel-caps.

  12. Pressure dependence of electron temperature using rf-floated electrostatic probes in rf plasmas

    International Nuclear Information System (INIS)

    Cantin, A.; Gagne, R.R.J.

    1977-01-01

    A new technique, which eliminates ac between probe and plasma by means of a ''follower'', permits electrostatic probes to be used in rf plasmas with a degree of confidence and accuracy which is equal, if not better, to that for a dc discharge. Measurements in argon, using this technique, have shown that electron temperature (T/sub e/) in an rf discharge is not higher than in dc discharge. Moreover the values of T/sub e/ do not agree with von Engel's law, but are in close agreement with a theory based on free diffusion and extrapolated up to values of pR=20 Torr cm (pressure times tube radius). These results are in contradiction with published electrostatic probe results for a positive column, but agree with published results as determined by microwave radiometry and optical spectroscopy. The hypothesis is made that the supporting evidence in favor of von Engel's law, afforded by published electrostatic probe results, could be due to an artifact

  13. Simulating of spectrum and polarization characteristics of ultrarelativistic - electron coherent radiation in a diamond crystal

    International Nuclear Information System (INIS)

    Truten', V.I.

    2000-01-01

    On the base of the computer simulation method it is shown that new maxima of ultrarelativistic electron radiation spectrum in aligned crystals may appear in a low-frequency region together with the ordinary coherent maxima. The appearance of these maxima is the result of the high-index-crystal-plane effect. These maxima manifest themselves in spectral as well as in polarization features of radiation [ru

  14. Relaxation of electron energy in the coupled polar semiconductor quantum dots

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Khás, Zdeněk; Zdeněk, Petr; Čerňanský, Marian; Lin, C. Y.

    2001-01-01

    Roč. 49, 10-11 (2001), s. 1011-1018 ISSN 0015-8208 R&D Projects: GA AV ČR IAA1010113; GA MŠk OC P5.20 Institutional research plan: CEZ:AV0Z1010914 Keywords : coupled polar semiconductor quantum dots * electron energy relaxation Subject RIV: BE - The oretical Physics Impact factor: 1.043, year: 2001

  15. Key electronic states in lithium battery materials probed by soft X-ray spectroscopy

    International Nuclear Information System (INIS)

    Yang, Wanli; Liu, Xiaosong; Qiao, Ruimin; Olalde-Velasco, Paul; Spear, Jonathan D.; Roseguo, Louis; Pepper, John X.; Chuang, Yi-de; Denlinger, Jonathan D.; Hussain, Zahid

    2013-01-01

    Highlights: •Key electronic states in battery materials revealed by soft X-ray spectroscopy. •Soft X-ray absorption consistently probes Mn oxidation states in different systems. •Soft X-ray absorption and emission fingerprint battery operations in LiFePO 4 . •Spectroscopic guidelines for selecting/optimizing polymer materials for batteries. •Distinct SEI formation on same electrode material with different crystal orientations. -- Abstract: The formidable challenges for developing a safe, low-cost, high-capacity, and high-power battery necessitate employing advanced tools that are capable of directly probing the key electronic states relevant to battery performance. Synchrotron based soft X-ray spectroscopy directly measures both the occupied and unoccupied states in the vicinity of the Fermi level, including transition-metal-3d and anion-p states. This article presents the basic concepts on how fundamental physics in electronic structure could provide valuable information for lithium-ion battery applications. We then discuss some of our recent studies on transition-metal oxide based cathodes, silicon based anode, and solid-electrolyte-interphase through soft X-ray absorption and emission spectroscopy. We argue that spectroscopic results reveal the evolution of electronic states for fingerprinting, understanding, and optimizing lithium-ion battery operations

  16. Probing Ultrafast Electron Dynamics at Surfaces Using Soft X-Ray Transient Reflectivity Spectroscopy

    Science.gov (United States)

    Baker, L. Robert; Husek, Jakub; Biswas, Somnath; Cirri, Anthony

    The ability to probe electron dynamics with surface sensitivity on the ultrafast time scale is critical for understanding processes such as charge separation, injection, and surface trapping that mediate efficiency in catalytic and energy conversion materials. Toward this goal, we have developed a high harmonic generation (HHG) light source for femtosecond soft x-ray reflectivity. Using this light source we investigated the ultrafast carrier dynamics at the surface of single crystalline α-Fe2O3, polycrystalline α-Fe2O3, and the mixed metal oxide, CuFeO2. We have recently demonstrated that CuFeO2 in particular is a selective catalyst for photo-electrochemical CO2 reduction to acetate; however, the role of electronic structure and charge carrier dynamics in mediating catalytic selectivity has not been well understood. Soft x-ray reflectivity measurements probe the M2,3, edges of the 3d transition metals, which provide oxidation and spin state resolution with element specificity. In addition to chemical state specificity, these measurements are also surface sensitive, and by independently simulating the contributions of the real and imaginary components of the complex refractive index, we can differentiate between surface and sub-surface contributions to the excited state spectrum. Accordingly, this work demonstrates the ability to probe ultrafast carrier dynamics in catalytic materials with element and chemical state specificity and with surface sensitivity.

  17. Understanding the electron-phonon interaction in polar crystals: Perspective presented by the vibronic theory

    Science.gov (United States)

    Pishtshev, A.; Kristoffel, N.

    2017-05-01

    We outline our novel results relating to the physics of the electron-TO-phonon (el-TO-ph) interaction in a polar crystal. We explained why the el-TO-ph interaction becomes effectively strong in a ferroelectric, and showed how the electron density redistribution establishes favorable conditions for soft-behavior of the long-wavelength branch of the active TO vibration. In the context of the vibronic theory it has been demonstrated that at the macroscopic level the interaction of electrons with the polar zone-centre TO phonons can be associated with the internal long-range dipole forces. Also we elucidated a methodological issue of how local field effects are incorporated within the vibronic theory. These result provided not only substantial support for the vibronic mechanism of ferroelectricity but also presented direct evidence of equivalence between vibronic and the other lattice dynamics models. The corresponding comparison allowed us to introduce the original parametrization for constants of the vibronic interaction in terms of key material constants. The applicability of the suggested formula has been tested for a wide class of polar materials.

  18. Investigation of resonant polarization radiation of relativistic electrons in gratings at small angles

    International Nuclear Information System (INIS)

    Aleinik, A.N.; Chefonov, O.V.; Kalinin, B.N.; Naumenko, G.A.; Potylitsyn, A.P.; Saruev, G.A.; Sharafutdinov, A.F.

    2003-01-01

    The resonant optical polarization radiation (ROPR) in the Smith-Purcell geometry and the one from the inclined grating at the Tomsk synchrotron and 6-MeV microtron have been investigated. The polarization radiation was observed at 4.2 deg. from the 200 MeV electron beam and at 5 deg. from the 6.2 MeV electron beam. Two methods of measurement of ROPR maxima in these two cases have been used. In the first case (the experiment on synchrotron) we have fixed the wavelength of radiation using an optical filter; the orientation dependence of this radiation was measured. In this dependence we have observed two peaks of radiation from electrons in gold foil grating of 0.1 mm period. The first large peak is a zeroth order peak in direction of specular reflection, and the second one is the first-order peak of resonant polarization radiation. In the experiment on microtron the spectra of ROPR from aluminum foil strip grating of 0.2 mm period in the Smith-Purcell geometry were measured, and the peak of the first-order Smith-Purcell radiation in these spectra was observed. The comparison of data obtained with the simulation results has been performed

  19. Polarized Neutron Diffraction to Probe Local Magnetic Anisotropy of a Low-Spin Fe(III) Complex.

    Science.gov (United States)

    Ridier, Karl; Mondal, Abhishake; Boilleau, Corentin; Cador, Olivier; Gillon, Béatrice; Chaboussant, Grégory; Le Guennic, Boris; Costuas, Karine; Lescouëzec, Rodrigue

    2016-03-14

    We have determined by polarized neutron diffraction (PND) the low-temperature molecular magnetic susceptibility tensor of the anisotropic low-spin complex PPh4 [Fe(III) (Tp)(CN)3]⋅H2O. We found the existence of a pronounced molecular easy magnetization axis, almost parallel to the C3 pseudo-axis of the molecule, which also corresponds to a trigonal elongation direction of the octahedral coordination sphere of the Fe(III) ion. The PND results are coherent with electron paramagnetic resonance (EPR) spectroscopy, magnetometry, and ab initio investigations. Through this particular example, we demonstrate the capabilities of PND to provide a unique, direct, and straightforward picture of the magnetic anisotropy and susceptibility tensors, offering a clear-cut way to establish magneto-structural correlations in paramagnetic molecular complexes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Laser sources for polarized electron beams in cw and pulsed accelerators

    CERN Document Server

    Hatziefremidis, A; Fraser, D; Avramopoulos, H

    1999-01-01

    We report the characterization of a high power, high repetition rate, mode-locked laser system to be used in continuous wave and pulsed electron accelerators for the generation of polarized electron beams. The system comprises of an external cavity diode laser and a harmonically mode-locked Ti:Sapphire oscillator and it can provide up to 3.4 W average power, with a corresponding pulse energy exceeding 1 nJ at 2856 MHz repetition rate. The system is tunable between 770-785 and 815-835 nm with two sets of diodes for the external cavity diode laser. (author)

  1. Complete snake and rotator schemes for spin polarization in proton rings and large electron rings

    International Nuclear Information System (INIS)

    Steffen, K.

    1983-11-01

    In order to maintain spin polarization in proton rings and large electron rings, some generalized Siberian Snake scheme may be required to make the spin tune almost independent of energy and thus avoid depolarizing resonances. The practical problem of finding such schemes that, at reasonable technical effort, can be made to work over large energy ranges has been addressed before and is here revisited in a broadened view and with added new suggestions. As a result, possibly optimum schemes for electron rings (LEP) and proton rings are described. In the proposed LEP scheme, spin rotation is devised such that, at the interaction points, the spin direction is longitudinal as required for experiments. (orig.)

  2. Measurement of Tensor Polarization in Elastic Electron-Deuteron Scattering at Large Momentum Transfer

    International Nuclear Information System (INIS)

    David Abbott; Abdellah Ahmidouch; Heinz Anklin; Francois Arvieux; Jacques Ball; Beedoe, S.; Elizabeth Beise; Louis Bimbot; Werner Boeglin; Herbert Breuer; Roger Carlini; Nicholas Chant; Samuel Danagoulian; Dow, K.; Jean-Eric Ducret; James Dunne; Lars Ewell; Laurent Eyraud; Christophe Furget; Michel Garcon; Ronald Gilman; Charles Glashausser; Paul Gueye; Kenneth Gustafsson; Kawtar Hafidi; Adrian Honegger; Juerg Jourdan; Serge Kox; Gerfried Kumbartzki; Lu, L.; Allison Lung; David Mack; Pete Markowitz; Justin McIntyre; David Meekins; Fernand Merchez; Joseph Mitchell; Mohring, R.; Sekazi Mtingwa; Hamlet Mkrtchyan; David Pitz; Liming Qin; Ronald Ransome; Jean-Sebastien Real; Philip Roos; Paul Rutt; Reyad Sawafta; Samuel Stepanyan; Raphael Tieulent; Egle Tomasi-Gustafsson; William Turchinetz; Kelley Vansyoc; Jochen Volmer; Eric Voutier; William Vulcan; Claude Williamson; Stephen Wood; Chen Yan; Jie Zhao; Wenxia Zhao

    2000-01-01

    Tensor polarization observables (t20, t21 and t22) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c) 2 . The experiment was performed at the Jefferson Laboratory in Hall C using the electron HMS Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q 2 the deuteron charge form factors G C and G Q . They are in good agreement with relativistic calculations and disagree with pQCD predictions

  3. Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

    International Nuclear Information System (INIS)

    Lu, Yu-Hsuan; Pilkuhn, Manfred H.; Fu, Yi-Keng; Chu, Mu-Tao; Huang, Shyh-Jer; Su, Yan-Kuin; Wang, Kang L.

    2014-01-01

    The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL

  4. Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yu-Hsuan; Pilkuhn, Manfred H. [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Fu, Yi-Keng; Chu, Mu-Tao [Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China); Huang, Shyh-Jer, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States); Su, Yan-Kuin, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electronic Engineering, Kun-Shan University, Tainan 71003, Taiwan (China); Wang, Kang L. [Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States)

    2014-03-21

    The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL.

  5. Recent results on solvation dynamics of electron and spur reactions of solvated electron in polar solvents studied by femtosecond laser spectroscopy and picosecond pulse radiolysis

    International Nuclear Information System (INIS)

    Mostafavi, M.

    2006-01-01

    . Nevertheless, the results show that the effect of the molecular structure of the solvents on solvation dynamics of electron is not negligible. The first study of picosecond pulse radiolysis of neat tetrahydrofuran (THF) by pulse-probe method was performed using the ELYSE picosecond pulse electron facility. ELYSE is a laser triggered electron accelerator that delivers at repetition rate of 1-50 Hz, electron pulses with a duration 5-15 ps, a charge of 2-7 nC and a kinetic energy tuneable in the range 2-9 MeV. The pulse- probe study of neat THF shows a fast decay of absorbance at 790 nm within 2.5 ns (Figure 2). This decay is assigned to the solvated electron. From the decay we deduced the time dependent G-value of solvated electron in the picosecond time range. The ratio between the initial absorbance (at 30 ps) and at 2.5 ns is about 2. In similar conditions, the same ratio in water and in the alcohols is 1.15, 1.25, respectively. In fact, the G-value of solvated electron in THF is much more time dependent that those in polar solvents like water and alcohols. We compared the time dependent G value for solvated electron between two methods: direct time resolved measurement and scavenging method. The analysis suggests either that the initial yield in THF (at zero time) is lower than in water or that a very fast decay occurs within the electron pulse.Eventually, the first pulse radiolysis measurements at picosecond range and at elevated temperature in water is studied by pulse-probe method using a high temperature high pressure cell. This study is done in collaboration with the Radiolysis laboratory of CEA/Saclay. The kinetics of the hydrated electron are found to be temperature dependent (Figure 3) and are qualitatively in agreement with radiolytic yield values obtained at elevated temperature after spur reactions. Assuming the same initial G value at picosecond time range for different temperatures, we deduce that at 350 degree C the yield at nanosecond range becomes almost the

  6. Dynamical nuclear spin polarization induced by electronic current through double quantum dots

    International Nuclear Information System (INIS)

    Lopez-Monis, Carlos; Platero, Gloria; Inarrea, Jesus

    2011-01-01

    We analyse electron-spin relaxation in electronic transport through coherently coupled double quantum dots (DQDs) in the spin blockade regime. In particular, we focus on hyperfine (HF) interaction as the spin-relaxation mechanism. We pay special attention to the effect of the dynamical nuclear spin polarization induced by the electronic current on the nuclear environment. We discuss the behaviour of the electronic current and the induced nuclear spin polarization versus an external magnetic field for different HF coupling intensities and interdot tunnelling strengths. We take into account, for each magnetic field, all HF-mediated spin-relaxation processes coming from different opposite spin level approaches. We find that the current as a function of the external magnetic field shows a peak or a dip and that the transition from a current dip to a current peak behaviour is obtained by decreasing the HF coupling or by increasing the interdot tunnelling strength. We give a physical picture in terms of the interplay between the electrons tunnelling out of the DQD and the spin-flip processes due to the nuclear environment.

  7. Electron-impact excitation rate-coefficients and polarization of subsequent emission for Ar"+ ion

    International Nuclear Information System (INIS)

    Dipti; Srivastava, Rajesh

    2016-01-01

    Electron impact excitation in Ar"+ ions has been studied by using fully relativistic distorted wave theory. Calculations are performed to obtain the excitation cross-sections and rate-coefficients for the transitions from the ground state 3p"5 (J=3/2) to fine-structure levels of excited states 3p"44s, 3p"44p, 3p"45s, 3p"45p, 3p"43d and 3p"44d. Polarization of the radiation following the excitation has been calculated using the obtained magnetic sub-level cross-sections. Comparison of the present rate-coefficients is also done with the previously reported theoretical results for some unresolved fine structure transitions. - Highlights: • Fully relativistic distorted wave theory has been used to study the excitation of fine-structure states of Ar"+. • We have calculated electron-impact excitation cross-sections for the wide range of incident electron energies. • Electron impact excitation rate-coefficients are calculated as a function of electron temperature. • Polarization of photons emitted following the decay of the excited fine-structure states are also reported.

  8. In vivo imaging of a stable paramagnetic probe by pulsed-radiofrequency electron paramagnetic resonance spectroscopy

    DEFF Research Database (Denmark)

    Murugesan; Cook; Devasahayam

    1997-01-01

    , Recent advances in radiofrequency (RF) electronics have enabled the generation of pulses of the order of 10-50 ns. Such short pulses provide adequate spectral coverage for EPR studies at 300 MHz resonant frequency. Acquisition of free induction decays (FID) of paramagnetic species possessing...... inhomogeneously broadened narrow lines after pulsed excitation is feasible with an appropriate digitizer/averager. This report describes the use of time-domain RF EPR spectrometry and imaging for in vivo applications. FID responses were collected from a water-soluble, narrow line width spin probe within phantom...... samples in solution and also when infused intravenously in an anesthetized mouse. Using static magnetic field gradients and back-projection methods of image reconstruction, two-dimensional images of the spin-probe distribution were obtained in phantom samples as well as in a mouse. The resolution...

  9. Surface electronic transport measurements: A micro multi-point probe approach

    DEFF Research Database (Denmark)

    Barreto, Lucas

    2014-01-01

    This work is mostly focused on the study of electronic transport properties of two-dimensional materials, in particular graphene and topological insulators. To study these, we have improved a unique micro multi-point probe instrument used to perform transport measurements. Not only the experimental...... quantities are extracted, such as conductivity, carrier density and carrier mobility. • A method to insulate electrically epitaxial graphene grown on metals, based on a stepwise intercalation methodology, is developed and transport measurements are performed in order to test the insulation. • We show...... a direct measurement of the surface electronic transport on a bulk topological insulator. The surface state conductivity and mobility are obtained. Apart from transport properties, we also investigate the atomic structure of the Bi2Se3(111) surface via surface x-ray diraction and low-energy electron...

  10. Fiber optic probe of free electron evanescent fields in the optical frequency range

    Energy Technology Data Exchange (ETDEWEB)

    So, Jin-Kyu, E-mail: js1m10@orc.soton.ac.uk; MacDonald, Kevin F. [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Zheludev, Nikolay I. [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371 (Singapore)

    2014-05-19

    We introduce an optical fiber platform which can be used to interrogate proximity interactions between free-electron evanescent fields and photonic nanostructures at optical frequencies in a manner similar to that in which optical evanescent fields are sampled using nanoscale aperture probes in scanning near-field microscopy. Conically profiled optical fiber tips functionalized with nano-gratings are employed to couple electron evanescent fields to light via the Smith-Purcell effect. We demonstrate the interrogation of medium energy (30–50 keV) electron fields with a lateral resolution of a few micrometers via the generation and detection of visible/UV radiation in the 700–300 nm (free-space) wavelength range.

  11. Defects in electron irradiated vitreous SiO2 probed by positron annihiliation

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro; Kawano, Takao; Itoh, Hisayoshi

    1994-01-01

    Defects in 3 MeV electron irradiated vitreous SiO 2 (v-SiO 2 ) were probed by the positron annihilation technique. For unirradiated v-SiO 2 specimens, almost all positrons were found to annihilate from positronium (Ps) states. This high formation probability of Ps was attributed to the trapping of positrons by open-space defects. The formation probability of Ps was decreased by the electron irradiation. The observed inhibition of the Ps formation was attributed to the trapping of positrons by point defects introduced and/or activated by the irradiation. From measurements of the lifetime distribution of Ps, it was found that, by the electron irradiation, the mean size of open-space defects was decreased and the size distribution of such defects was broadened. (Author)

  12. Defects in electron irradiated vitreous SiO[sub 2] probed by positron annihiliation

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Tanigawa, Shoichiro (Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science); Kawano, Takao (Tsukuba Univ., Ibaraki (Japan). Radioisotope Centre); Itoh, Hisayoshi (Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment)

    1994-10-10

    Defects in 3 MeV electron irradiated vitreous SiO[sub 2] (v-SiO[sub 2]) were probed by the positron annihilation technique. For unirradiated v-SiO[sub 2] specimens, almost all positrons were found to annihilate from positronium (Ps) states. This high formation probability of Ps was attributed to the trapping of positrons by open-space defects. The formation probability of Ps was decreased by the electron irradiation. The observed inhibition of the Ps formation was attributed to the trapping of positrons by point defects introduced and/or activated by the irradiation. From measurements of the lifetime distribution of Ps, it was found that, by the electron irradiation, the mean size of open-space defects was decreased and the size distribution of such defects was broadened. (Author).

  13. Probing a molecular electronic transition by two-colour sum-frequency generation spectroscopy

    International Nuclear Information System (INIS)

    Humbert, C.; Dreesen, L.; Nihonyanagi, S.; Masuda, T.; Kondo, T.; Mani, A.A.; Uosaki, K.; Thiry, P.A.; Peremans, A.

    2003-01-01

    We demonstrate that a new emerging technique, two-colour sum-frequency generation (SFG) spectroscopy, can be used to probe the molecular electronic properties of self-assembled monolayers (SAMs). In the CH spectral range (2800-3200 cm -1 ), we show that the sum-frequency generation signal of a porphyrin alkanethiol derivative adsorbed on Pt(1 1 1) reaches a maximum intensity at ∼435 nm SFG wavelength. This wavelength corresponds to the porphyrin moiety specific π-π* molecular electronic transition which is called the Soret or B band. This resonant behaviour is not observed for 1-dodecanethiol SAMs, which are devoid of molecular electronic transition in the investigated visible spectral range

  14. A Spin-Light Polarimeter for Multi-GeV Longitudinally Polarized Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Mohanmurthy, Prajwal [Mississippi State University, Starkville, MS (United States); Dutta, Dipangkar [Mississippi State University, Starkville, MS (United States) and Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2014-02-01

    The physics program at the upgraded Jefferson Lab (JLab) and the physics program envisioned for the proposed electron-ion collider (EIC) include large efforts to search for interactions beyond the Standard Model (SM) using parity violation in electroweak interactions. These experiments require precision electron polarimetry with an uncertainty of < 0.5 %. The spin dependent Synchrotron radiation, called "spin-light," can be used to monitor the electron beam polarization. In this article we develop a conceptual design for a "spin-light" polarimeter that can be used at a high intensity, multi-GeV electron accelerator. We have also built a Geant4 based simulation for a prototype device and report some of the results from these simulations.

  15. Science Requirements and Conceptual Design for a Polarized Medium Energy Electron-Ion Collider at Jlab

    Energy Technology Data Exchange (ETDEWEB)

    Abeyratne, S; Ahmed, S; Barber, D; Bisognano, J; Bogacz, A; Castilla, A; Chevtsov, P; Corneliussen, S; Deconinck, W; Degtiarenko, P; Delayen, J; Derbenev, Ya; DeSilva, S; Douglas, D; Dudnikov, V; Ent, R; Erdelyi, B; Evtushenko, P; Fujii, Yu; Filatov, Yury; Gaskell, D; Geng, R; Guzey, V; Horn, T; Hutton, A; Hyde, C; Johnson, R; Kim, Y; Klein, F; Kondratenko, A; Kondratenko, M; Krafft, G; Li, R; Lin, F; Manikonda, S; Marhauser, F; McKeown, R; Morozov, V; Dadel-Turonski, P; Nissen, E; Ostroumov, P; Pivi, M; Pilat, F; Poelker, M; Prokudin, A; Rimmer, R; Satogata, T; Sayed, H; Spata, M; Sullivan, M; Tennant, C; Terzic, B; Tiefenback, M; Wang, M; Wang, S; Weiss, C; Yunn, B

    2012-08-01

    Researchers have envisioned an electron-ion collider with ion species up to heavy ions, high polarization of electrons and light ions, and a well-matched center-of-mass energy range as an ideal gluon microscope to explore new frontiers of nuclear science. In its most recent Long Range Plan, the Nuclear Science Advisory Committee (NSAC) of the US Department of Energy and the National Science Foundation endorsed such a collider in the form of a 'half-recommendation.' As a response to this science need, Jefferson Lab and its user community have been engaged in feasibility studies of a medium energy polarized electron-ion collider (MEIC), cost-effectively utilizing Jefferson Lab's already existing Continuous Electron Beam Accelerator Facility (CEBAF). In close collaboration, this community of nuclear physicists and accelerator scientists has rigorously explored the science case and design concept for this envisioned grand instrument of science. An electron-ion collider embodies the vision of reaching the next frontier in Quantum Chromodynamics - understanding the behavior of hadrons as complex bound states of quarks and gluons. Whereas the 12 GeV Upgrade of CEBAF will map the valence-quark components of the nucleon and nuclear wave functions in detail, an electron-ion collider will determine the largely unknown role sea quarks play and for the first time study the glue that binds all atomic nuclei. The MEIC will allow nuclear scientists to map the spin and spatial structure of quarks and gluons in nucleons, to discover the collective effects of gluons in nuclei, and to understand the emergence of hadrons from quarks and gluons. The proposed electron-ion collider at Jefferson Lab will collide a highly polarized electron beam originating from the CEBAF recirculating superconducting radiofrequency (SRF) linear accelerator (linac) with highly polarized light-ion beams or unpolarized light- to heavy-ion beams from a new ion accelerator and storage complex. Since the very

  16. Science Requirements and Conceptual Design for a Polarized Medium Energy Electron-Ion Collider at Jlab

    International Nuclear Information System (INIS)

    Abeyratne, S.; Accardi, A.; Ahmed, S.; Barber, D.; Bisognano, J.; Bogacz, A.; Castilla, A.; Chevtsov, P.; Corneliussen, S.; Deconinck, W.; Degtiarenko, P.; Delayen, J.; Derbenev, Ya.; DeSilva, S.; Douglas, D.; Dudnikov, V.; Ent, R.; Erdelyi, B.; Evtushenko, P.; Fujii, Yu; Filatov, Yury; Gaskell, D.; Geng, R.; Guzey, V.; Horn, T.; Hutton, A.; Hyde, C.; Johnson, R.; Kim, Y.; Klein, F.; Kondratenko, A.; Kondratenko, M.; Krafft, G.; Li, R.; Lin, F.; Manikonda, S.; Marhauser, F.; McKeown, R.; Morozov, V.; Dadel-Turonski, P.; Nissen, E.; Ostroumov, P.; Pivi, M.; Pilat, F.; Poelker, M.; Prokudin, A.; Rimmer, R.; Satogata, T.; Sayed, H.; Spata, M.; Sullivan, M.; Tennant, C.; Terzic, B.; Tiefenback, M.; Wang, H.; Wang, S.; Weiss, C.; Yunn, B.; Zhang, Y.

    2012-01-01

    Researchers have envisioned an electron-ion collider with ion species up to heavy ions, high polarization of electrons and light ions, and a well-matched center-of-mass energy range as an ideal gluon microscope to explore new frontiers of nuclear science. In its most recent Long Range Plan, the Nuclear Science Advisory Committee (NSAC) of the US Department of Energy and the National Science Foundation endorsed such a collider in the form of a 'half-recommendation.' As a response to this science need, Jefferson Lab and its user community have been engaged in feasibility studies of a medium energy polarized electron-ion collider (MEIC), cost-effectively utilizing Jefferson Lab's already existing Continuous Electron Beam Accelerator Facility (CEBAF). In close collaboration, this community of nuclear physicists and accelerator scientists has rigorously explored the science case and design concept for this envisioned grand instrument of science. An electron-ion collider embodies the vision of reaching the next frontier in Quantum Chromodynamics - understanding the behavior of hadrons as complex bound states of quarks and gluons. Whereas the 12 GeV Upgrade of CEBAF will map the valence-quark components of the nucleon and nuclear wave functions in detail, an electron-ion collider will determine the largely unknown role sea quarks play and for the first time study the glue that binds all atomic nuclei. The MEIC will allow nuclear scientists to map the spin and spatial structure of quarks and gluons in nucleons, to discover the collective effects of gluons in nuclei, and to understand the emergence of hadrons from quarks and gluons. The proposed electron-ion collider at Jefferson Lab will collide a highly polarized electron beam originating from the CEBAF recirculating superconducting radiofrequency (SRF) linear accelerator (linac) with highly polarized light-ion beams or unpolarized light- to heavy-ion beams from a new ion accelerator and storage complex. Since the very

  17. Electronic device for measuring the polarization parameter in the π-p → π0n charge exchange reaction on a polarized proton target

    International Nuclear Information System (INIS)

    Brehin, S.

    1967-12-01

    An electronic apparatus has been constructed to measure the polarization parameter P 0 (t) in π - p → π 0 n charge exchange scattering at 5.9 GeV/c and 11,2 GeV/c on polarized proton target. This device insures triggering of a heavy plate spark chamber, allowing visualisation of γ rays from the π 0 decays when the associated neutron offers suitable characteristics in direction and energy. The neutron is detected by an array of 32 counters and his energy is measured by a time of flight method. Electronic circuits of this apparatus are described as test and calibration methods used. (author) [fr

  18. ''Electron Conic'' Signatures observed in the nightside auroral zone and over the polar cap

    International Nuclear Information System (INIS)

    Menietti, J.D.; Burch, J.L.

    1985-01-01

    A preliminary search of the Dynamics Explorer 1 high-altitude plasma instrument data base has yielded examples of ''electron conic'' signatures. The three example passes show an association with regions of downward electron acceleration and upward ion beams, but this is not true of all the electron conic events. The electron conic signatures are clearly discernible on energy-flux-versus-time color spectrograms as pairs of discrete vertical bands which are symmetric about a pitch angle of approximately 180 0 . One of the examples is a polar cap pass with electron conic signatures observed at invariant latitudes from 84 0 to 75 0 . The other two cases are nightside auroral zone passes in which the regions of detectable electron conics are spatially more confined, covering only about 1 0 in invariant latitude. The conic signatures have been found at energies that range from 50 eV 0 is larger than expected for a loss cone feature. If the electrons conserve the first adiabatic invariant in a dipole magnetic field, and in some cases a parallel electric field, the mirroring altitude varies between about 500 km and 8000 km, which is above the atmospheric loss region. For this reason, and in analogy with the formation of ion conics, we suggest that the conic signatures are produced by heating of the electrons perpendicular to the magnetic field

  19. Strong electron bidirectional anisotropies in the distant tail: ISEE 3 observations of polar rain

    International Nuclear Information System (INIS)

    Baker, D.N.; Bame, S.J.; Feldman, W.C.; Gosling, J.T.; Zwickl, R.D.; Slavin, J.A.; Smith, E.J.

    1986-01-01

    A detailed observational treatment of bidirectional electrons (--50 to 50 eV)in the distant magnetotail (rapprox. >100 R/sub E/) is presented. It is found that electrons in this energy range commonly exhibit strong, field-aligned anisotropies in the tail lobes. Because of large tail motions, the ISEE 3 data provide extensive sampling of both the north and south lobes in rapid succession. These data demonstrate directly the strong asymmetries that exist between the north and south lobes at any one time. The bidirectional fluxes are found to occur predominantly in the lobe directly connected to the sunward interplanetary magnetic field in the open magnetosphere model (north lobe for away sectors and south lobe for toward sectors). Electron anisotropy and magnetic field data are presented which show the transition from unidirectional (sheath) electron populations to bidirectional (lobe) populations. Thus we demonstrate the open nature of the distant magnetopause and show that the source of the higher-energy, bidirectional lobe electrons is the tailward directed electron heat flux population in the distant magnetosheath. Taken together, the present evidence suggests that the bidirectional electrons that we observe in the distant tail are closely related to the polar rain electrons observed previously at lower altitudes. Furthermore, these data provide strong evidence that the distant tail is composed largely of open magnetic field lines in contradistinction to some recently advanced models

  20. Self-consistent electronic structure of spin-polarized dilute magnetic semiconductor quantum wells

    International Nuclear Information System (INIS)

    Hong, S. P.; Yi, K. S.; Quinn, J. J.

    2000-01-01

    The electronic properties of spin-symmetry-broken dilute magnetic semiconductor quantum wells are investigated self-consistently at zero temperature. The spin-split subband structure and carrier concentration of modulation-doped quantum wells are examined in the presence of a strong magnetic field. The effects of exchange and correlations of electrons are included in a local-spin-density-functional approximation. We demonstrate that exchange correlation of electrons decreases the spin-split subband energy but enhances the carrier density in a spin-polarized quantum well. We also observe that as the magnetic field increases, the concentration of spin-down (majority) electrons increases but that of spin-up (minority) electrons decreases. The effect of orbital quantization on the in-plane motion of electrons is also examined and shows a sawtoothlike variation in subband electron concentrations as the magnetic-field intensity increases. The latter variation is attributed to the presence of ionized donors acting as the electron reservoir, which is partially responsible for the formation of the integer quantum Hall plateaus. (c) 2000 The American Physical Society

  1. Measurement of the longitudinal polarization of the HERA electron beam using crystals and the ZEUS luminosity monitor

    International Nuclear Information System (INIS)

    Piotrzkowski, K.

    1995-12-01

    A measurement of the longitudinal polarization of the electron beam at HERA utilizing coherent interactions of high energy photons in crystals is described. Modification of existing facilities would allow an independent polarization measurement and a verification of birefringence phenomena in crystals for 20-30 GeV photons. Relevant experimental issues and systematic uncertainties are also presented. (orig.)

  2. Polar observations of electron density distribution in the Earth’s magnetosphere. 2. Density profiles

    Directory of Open Access Journals (Sweden)

    H. Laakso

    2002-11-01

    Full Text Available Using spacecraft potential measurements of the Polar electric field experiment, we investigate electron density variations of key plasma regions within the magnetosphere, including the polar cap, cusp, trough, plasmapause, and auroral zone. The statistical results were presented in the first part of this study, and the present paper reports detailed structures revealed by individual satellite passes. The high-altitude (> 3 RE polar cap is generally one of the most tenuous regions in the magnetosphere, but surprisingly, the polar cap boundary does not appear as a steep density decline. At low altitudes (1 RE in summer, the polar densities are very high, several 100 cm-3 , and interestingly, the density peaks at the central polar cap. On the noonside of the polar cap, the cusp appears as a dense, 1–3° wide region. A typical cusp density above 4 RE distance is between several 10 cm-3 and a few 100 cm-3 . On some occasions the cusp is crossed multiple times in a single pass, simultaneously with the occurrence of IMF excursions, as the cusp can instantly shift its position under varying solar wind conditions, similar to the magnetopause. On the nightside, the auroral zone is not always detected as a simple density cavity. Cavities are observed but their locations, strengths, and sizes vary. Also, the electric field perturbations do not necessarily overlap with the cavities: there are cavities with no field disturbances, as well as electric field disturbances observed with no clear cavitation. In the inner magnetosphere, the density distributions clearly show that the plasmapause and trough densities are well correlated with geomagnetic activity. Data from individual orbits near noon and midnight demonstrate that at the beginning of geomagnetic disturbances, the retreat speed of the plasmapause can be one L-shell per hour, while during quiet intervals the plasmapause can expand anti-earthward at the same speed. For the trough region, it is found

  3. Determination of electron beam polarization using electron detector in Compton polarimeter with less than 1% statistical and systematic uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, Amrendra [Mississippi State Univ., Mississippi State, MS (United States)

    2015-05-01

    The Q-weak experiment aims to measure the weak charge of proton with a precision of 4.2%. The proposed precision on weak charge required a 2.5% measurement of the parity violating asymmetry in elastic electron - proton scattering. Polarimetry was the largest experimental contribution to this uncertainty and a new Compton polarimeter was installed in Hall C at Jefferson Lab to make the goal achievable. In this polarimeter the electron beam collides with green laser light in a low gain Fabry-Perot Cavity; the scattered electrons are detected in 4 planes of a novel diamond micro strip detector while the back scattered photons are detected in lead tungstate crystals. This diamond micro-strip detector is the first such device to be used as a tracking detector in a nuclear and particle physics experiment. The diamond detectors are read out using custom built electronic modules that include a preamplifier, a pulse shaping amplifier and a discriminator for each detector micro-strip. We use field programmable gate array based general purpose logic modules for event selection and histogramming. Extensive Monte Carlo simulations and data acquisition simulations were performed to estimate the systematic uncertainties. Additionally, the Moller and Compton polarimeters were cross calibrated at low electron beam currents using a series of interleaved measurements. In this dissertation, we describe all the subsystems of the Compton polarimeter with emphasis on the electron detector. We focus on the FPGA based data acquisition system built by the author and the data analysis methods implemented by the author. The simulations of the data acquisition and the polarimeter that helped rigorously establish the systematic uncertainties of the polarimeter are also elaborated, resulting in the first sub 1% measurement of low energy (?1 GeV) electron beam polarization with a Compton electron detector. We have demonstrated that diamond based micro-strip detectors can be used for tracking in a

  4. Electric dipole excitation of {sup 208}Pb by polarized electron impact

    Energy Technology Data Exchange (ETDEWEB)

    Jakubassa-Amundsen, D.H. [University of Munich, Mathematics Institute, Munich (Germany); Ponomarev, V.Yu. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany)

    2016-03-15

    The cross sections and spin asymmetries for the excitation of 1{sup -} states in {sup 208}Pb by transversely polarized electrons with collision energy of 30-180MeV have been examined within the DWBA scattering formalism. As examples, we have considered a low-lying 1{sup -} state and also states belonging to the pygmy dipole and giant dipole resonances. The structure of these states and their corresponding transition charge and current densities have been taken from an RPA calculation within the quasiparticle phonon model. The complex-plane rotation method has been applied to achieve the convergence of the radial DWBA integrals for backward scattering. We have studied the behaviour of the cross sections and spin asymmetries as a function of electron energy and scattering angle. The role of the longitudinal and transversal contributions to the excitation has been thoroughly studied. We conclude that the spin asymmetry S, related to unpolarized outgoing electrons, is mostly well below 1% even at the backward scattering angles and its measurement provides a challenge for future experiments with polarized electrons. (orig.)

  5. Transport of electrons in the tunnel of an ion sensitive probe

    Czech Academy of Sciences Publication Activity Database

    Komm, Michael; Adámek, Jiří; Dejarnac, Renaud; Gunn, J. P.; Pekárek, Z.

    2011-01-01

    Roč. 53, č. 1 (2011), 015005-015005 ISSN 0741-3335 R&D Projects: GA AV ČR KJB100430901; GA MŠk 7G09042; GA MŠk LA08048 Institutional research plan: CEZ:AV0Z20430508 Keywords : Tokamak * plasma * katsumata probe * ExB drift * ion temperature * tunnel * electron Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.425, year: 2011 http://iopscience.iop.org/0741-3335/53/1/015005/pdf/0741-3335_53_1_015005.pdf

  6. A novel probe of intrinsic electronic structure: hard X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    Takata, Y.; Tamasaku, K.; Nishino, Y.; Miwa, D.; Yabashi, M.; Ikenaga, E.; Horiba, K.; Arita, M.; Shimada, K.; Namatame, H.; Nohira, H.; Hattori, T.; Soedergren, S.; Wannberg, B.; Taniguchi, M.; Shin, S.; Ishikawa, T.; Kobayashi, K.

    2005-01-01

    We have realized hard X-ray (HX) photoemission spectroscopy (PES) with high throughput and high-energy resolution for core level and valence band studies using high-energy and high-brilliance synchrotron radiation at SPring-8. This is a brand new method because large escape depth of high-energy photoelectrons enables us to probe intrinsic bulk states free from surface condition. By use of a newly developed electron energy analyzer and well-focused X-rays, high-energy resolution of 75 meV (E/ΔE 79,000) was realized for 5.95 keV photoelectrons

  7. Electron temperature and heat load measurements in the COMPASS divertor using the new system of probes

    Czech Academy of Sciences Publication Activity Database

    Adámek, Jiří; Seidl, Jakub; Horáček, Jan; Komm, Michael; Eich, T.; Pánek, Radomír; Cavalier, J.; Devitre, A.; Peterka, Matěj; Vondráček, Petr; Stöckel, Jan; Šesták, David; Grover, Ondřej; Bílková, Petra; Böhm, Petr; Varju, Jozef; Havránek, Aleš; Weinzettl, Vladimír; Lovell, J.; Dimitrova, Miglena; Mitošinková, Klára; Dejarnac, Renaud; Hron, Martin

    2017-01-01

    Roč. 57, č. 11 (2017), č. článku 116017. ISSN 0029-5515 R&D Projects: GA ČR(CZ) GA15-10723S; GA ČR(CZ) GA16-14228S; GA MŠk(CZ) LM2015045 EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : COMPASS * divertor * heat load * ELM * electron temperature * Ball-pen probe Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.307, year: 2016 http://iopscience.iop.org/article/10.1088/1741-4326/aa7e09

  8. 2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe.

    Science.gov (United States)

    Chen, Y H; Yang, X Y; Lin, C; Wang, L; Xu, M; Wang, X G; Xiao, C J

    2014-11-01

    A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

  9. Chemical analysis of minerals in granitic rocks by electron probe micro analyser

    International Nuclear Information System (INIS)

    Hiraoka, Yoshihiro

    1994-01-01

    The chemical compositions of minerals in a few granitic rocks were determined by electron probe micro analyser (EPMA). The accurate analytical data for standard feldspar groups were obtained by correcting the low analytical values of sodium and potassium that were arised from the damage in EPMA analysis. Using this method, feldspar groups and biotites in three granitic rocks gathered from Hiei, Hira and Kurama areas respectively, were analyzed. As the results, the local characteristics were observed in the kinds of feldspar groups and the chemical compositions of biotites that were contained in granitic rocks. (author)

  10. Detection of beryllium in oxides and silicates by electron-probe microanalysis

    Directory of Open Access Journals (Sweden)

    V. V. Khiller

    2017-12-01

    Full Text Available The author developed the technique of electron-probe microanalysis for quantitative determination of beryllium content, providing the example of studying natural minerals (aluminosilicates and oxides. This technique allowed to obtain a quantitative content of beryllium (in combination with other elements in the emeralds of the Mariinsky beryllium deposit and in zonal mariinskite-chrysoberyl from the chromitites of the Bazhenov ophiolite complex. All analyzes of minerals were performed on a CAMECA SX 100 electron probe microanalyzer with five wave spectrometers (IGG UB RAS. The pressure in the sample chamber was 2 × 10–4 Pa, in the electron gun region – 4 × 10–6 Pa, in wave spectrometers – 7 Pa. Accelerating voltage was 10 kV, the current of absorbed electrons on the Faraday cylinder (beam current was 100–150 nA. Diameter of the electron beam focused on the sample was 2 μm, the angle of x-ray extraction was 40°. The spectra were obtained on wave spectrometers with TAP crystal analyzers (2d = 25.745 Å, LPET (2d = 8.75 Å, LiF (2d = 4.0226 Å, and PC3 (2d = 211.4 Å, a specialized crystal for determining the content of beryllium and boron; the author carried out all the elements measurements along the Kα-lines. To determine position of the analytical peak and the background from two sides with the minimum possible spectral overlap, the author preliminarily recorded spectra on wave spectrometers. The obtained microprobe analyzes of minerals with quantitative determination of beryllium converge well with the available theoretical compositions of beryl and chrysoberyl, which indicates the high efficiency of the developed technique. By using this technique, we can relatively quickly and reliably determine the quantitative content of beryllium in natural silicates and oxides, which is an acute need for geological researchers studying the mineralogy of beryllium deposits.

  11. Biogeochemical fingerprints of life: earlier analogies with polar ecosystems suggest feasible instrumentation for probing the Galilean moons

    Science.gov (United States)

    Chela-Flores, J.; Cicuttin, A.; Crespo, M. L.; Tuniz, C.

    2015-07-01

    1960s) that the distribution range of 32S/34S in analysed extra-terrestrial material appears to be narrower than the isotopic ratio of H, C or N and may be the most reliable for estimating biological effects. In addition, we discuss the necessary instruments that can test our biogenic hypothesis. First of all we hasten to clarify that the last-generation miniaturized mass spectrometer we discuss in the present paper are capable of reaching the required accuracy of ‰ for the all-important measurements with JGO of the thin atmospheres of the icy satellites. To implement the measurements, we single out miniature laser ablation time-of-flight mass spectrometers that are ideal for the forthcoming JUICE probing of the exoatmospheres, ionospheres and, indirectly, surficial low-albedo regions. Ganymede's surface, besides having ancient dark terrains covering about one-third of the total surface, has bright terrains of more recent origin, possibly due to some internal processes, not excluding biological ones. The geochemical test could identify bioindicators on Europa and exclude them on its large neighbour by probing relatively recent bright terrains on Ganymede's Polar Regions.

  12. Monte Carlo Simulation of Quantitative Electron Probe Microanalysis of the PWR Spent Fuel with a Pt Coating

    International Nuclear Information System (INIS)

    Kwon, Hyoung Mun; Lee, Hyung Kwon; Son, Young Zoon; Chun, Yong Bum

    2012-01-01

    The PWR spent fuel sample should be coated with conducting material in order to provide a path for electrons and to prevent charging. Generally, the ZAF method has been used for quantitative electron probe microanalysis of conducting samples. However, the coated samples are not applicable for the ZAF method. Probe current, primary electron energy and x-ray produced by the primary beam are attenuated within the coating films. The electron and X-ray depth distributions for a quantitative electron probe micro analysis were simulated by the CASINO Monte Carlo program [2] to evaluate the x-ray attenuation within the Pt coating films. The target samples are the PWR spent fuels with 50 GWd/tU of burnup , 6 years of cooling time and a Pt coating film (3, 5, 7, 10 and 15 nm thickness)

  13. Monte Carlo Simulation of Quantitative Electron Probe Microanalysis of the PWR Spent Fuel with a Pt Coating

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Hyoung Mun; Lee, Hyung Kwon; Son, Young Zoon; Chun, Yong Bum [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    The PWR spent fuel sample should be coated with conducting material in order to provide a path for electrons and to prevent charging. Generally, the ZAF method has been used for quantitative electron probe microanalysis of conducting samples. However, the coated samples are not applicable for the ZAF method. Probe current, primary electron energy and x-ray produced by the primary beam are attenuated within the coating films. The electron and X-ray depth distributions for a quantitative electron probe micro analysis were simulated by the CASINO Monte Carlo program [2] to evaluate the x-ray attenuation within the Pt coating films. The target samples are the PWR spent fuels with 50 GWd/tU of burnup , 6 years of cooling time and a Pt coating film (3, 5, 7, 10 and 15 nm thickness)

  14. Ultrafast optical pump terahertz-probe spectroscopy of strongly correlated electron materials

    International Nuclear Information System (INIS)

    Averitt, R.D.; Taylor, Antoinette J.; Thorsmolle, V.K.; Jia, Quanxi; Lobad, A.I.; Trugman, S.A.

    2001-01-01

    We have used optical-pump far-infrared probe spectroscopy to probe the low energy electron dynamics of high temperature superconductors and colossal magnetoresistance manganites. For the superconductor YBa2Cu3O7, picosecond conductivity measurements probe the interplay between Cooper-pairs and quasiparticles. In optimally doped films, the recovery time for long-range phase-coherent pairing increases from ∼1.5 ps at 4K to ∼3.5 ps near Tc, consistent with the closing of the superconducting gap. For underdoped films, the measured recovery time is temperature independent (3.5 ps) in accordance with the presence of a pseudogap. Ultrafast picosecond measurements of optically induced changes in the absolute conductivity of La0:7M0:3MnO3 thin films (M = Ca, Sr) from 10K to ∼0.9Tc reveal a two-component relaxation. A fast, ∼2 ps, conductivity decrease arises from optically induced modification of the effective phonon temperature. The slower component, related to spin-lattice relaxation, has a lifetime that increases upon approaching Tc from below in accordance with an increasing spin specific heat. Our results indicate that for T<< Tc, the conductivity is determined by incoherent phonons while spin fluctuations dominate near Tc.

  15. Continuous wave protocol for simultaneous polarization and optical detection of P1-center electron spin resonance

    Science.gov (United States)

    Kamp, E. J.; Carvajal, B.; Samarth, N.

    2018-01-01

    The ready optical detection and manipulation of bright nitrogen vacancy center spins in diamond plays a key role in contemporary quantum information science and quantum metrology. Other optically dark defects such as substitutional nitrogen atoms (`P1 centers') could also become potentially useful in this context if they could be as easily optically detected and manipulated. We develop a relatively straightforward continuous wave protocol that takes advantage of the dipolar coupling between nitrogen vacancy and P1 centers in type 1b diamond to detect and polarize the dark P1 spins. By combining mutual spin flip transitions with radio frequency driving, we demonstrate the simultaneous optical polarization and detection of the electron spin resonance of the P1 center. This technique should be applicable to detecting and manipulating a broad range of dark spin populations that couple to the nitrogen vacancy center via dipolar fields, allowing for quantum metrology using these spin populations.

  16. Control of Electronic Conduction at an Oxide Heterointerface using Surface Polar Adsorbates

    Energy Technology Data Exchange (ETDEWEB)

    Bell, Christopher

    2011-08-19

    We study the effect of the surface adsorption of a variety of common laboratory solvents on the conductivity at the interface between LaAlO{sub 3} and SrTiO{sub 3}. This interface possesses a range of intriguing physics, notably a proposed connection between the surface state of the LaAlO{sub 3} and the conductivity buried in the SrTiO{sub 3}. We show that the application of chemicals such as acetone, ethanol, and water can induce a large change (factor of three) in the conductivity. This phenomenon is observed only for polar solvents. These data provide experimental evidence for a general polarization-facilitated electronic transfer mechanism.

  17. Contribution of vitamin K1 to the electron spin polarization in spinach photosystem I

    International Nuclear Information System (INIS)

    Rustandi, R.R.; Snyder, S.W.; Feezel, L.L.; Michalski, T.J.; Norris, J.R.; Thurnauer, M.C.; Biggins, J.

    1990-01-01

    The electron spin polarized (ESP) electron paramagnetic resonance (EPR) signal observed in spinach photosystem I (PSI) particles was examined in preparations depleted of vitamin K1 by solvent extraction and following biological reconstitution by the quinone. The ESP EPR signal was not detected in the solvent-extracted PSI sample but was restored upon reconstitution with either protonated or deuterated vitamin K1 under conditions that also restored electron transfer to the terminal PSI acceptors. Reconstitution using deuterated vitamin K1 resulted in a line narrowing of the ESP EPR signal, supporting the conclusion that the ESP EPR signals in the reconstituted samples arise from a radical pair consisting of the oxidized PSI primary donor, P700+, and reduced vitamin K1

  18. Soft x-ray spectroscopy for probing electronic and chemical states of battery materials

    International Nuclear Information System (INIS)

    Yang Wanli; Qiao Ruimin

    2016-01-01

    The formidable challenge of developing high-performance battery system stems from the complication of battery operations, both mechanically and electronically. In the electrodes and at the electrode–electrolyte interfaces, chemical reactions take place with evolving electron states. In addition to the extensive studies of material synthesis, electrochemical, structural, and mechanical properties, soft x-ray spectroscopy provides unique opportunities for revealing the critical electron states in batteries. This review discusses some of the recent soft x-ray spectroscopic results on battery binder, transition-metal based positive electrodes, and the solid-electrolyte-interphase. By virtue of soft x-ray’s sensitivity to electron states, the electronic property, the redox during electrochemical operations, and the chemical species of the interphases could be fingerprinted by soft x-ray spectroscopy. Understanding and innovating battery technologies need a multimodal approach, and soft x-ray spectroscopy is one of the incisive tools to probe the chemical and physical evolutions in batteries. (topical review)

  19. Compensation of aberrations of deflected electron probe by means of dynamical focusing with stigmator

    International Nuclear Information System (INIS)

    Baba, Norio; Ebe, Toyoe; Ikehata, Koichi; Ito, Yasuhiro; Terada, Hiroshi

    1979-01-01

    Electron beam passing through a deflecting field is in general, subjected to aberrations such as distortion, astigmatism and coma in accordance with the deflecting angle. Accordingly the aberration defect of deflected beam is the most serious limiting factor in the performances of micromachining, microminiaturization and high resolution scanning electron microscopes. From many investigators' results, it is obvious that three important compensation methods to aberrations exist in principle, i.e., double deflection system, dynamical focusing, and the dynamical correction using a stigmator. In this paper, based on the aberration formula derived from the eikonal or the path method, the practical data of the aberration constants of deflected electron beam for the sequential deflection system with parallel plates are calculated, and using its result, the distorted spot patterns of an electron probe deflected in two-dimensional directions for various defocusings are graphically displayed by the aid of a computer. Further, by means of the dynamical focusing with a stigmator, the conditions to completely compensate the second order astigmatic aberration are derived, and spot patterns and the electron density distributions within the spots in the case when the compensating conditions are satisfied are also graphically displayed. (Wakatsuki, Y.)

  20. Low magnification differential phase contrast imaging of electric fields in crystals with fine electron probes

    Energy Technology Data Exchange (ETDEWEB)

    Taplin, D.J. [School of Physics and Astronomy, Monash University, Clayton, Victoria 3800 (Australia); Shibata, N. [Institute of Engineering Innovation, School of Engineering, University of Tokyo, Tokyo 113-8656 (Japan); Weyland, M. [Monash Centre for Electron Microscopy, Monash University, Clayton, Victoria 3800 (Australia); Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800 (Australia); Findlay, S.D., E-mail: scott.findlay@monash.edu [School of Physics and Astronomy, Monash University, Clayton, Victoria 3800 (Australia)

    2016-10-15

    To correlate atomistic structure with longer range electric field distribution within materials, it is necessary to use atomically fine electron probes and specimens in on-axis orientation. However, electric field mapping via low magnification differential phase contrast imaging under these conditions raises challenges: electron scattering tends to reduce the beam deflection due to the electric field strength from what simple models predict, and other effects, most notably crystal mistilt, can lead to asymmetric intensity redistribution in the diffraction pattern which is difficult to distinguish from that produced by long range electric fields. Using electron scattering simulations, we explore the effects of such factors on the reliable interpretation and measurement of electric field distributions. In addition to these limitations of principle, some limitations of practice when seeking to perform such measurements using segmented detector systems are also discussed. - Highlights: • Measuring electric fields by on-axis electron diffraction is explored by simulation. • Electron channelling reduces deflection predicted by the phase object approximation. • First moment measurements cannot distinguish electric fields from specimen mistilt. • Segmented detector estimates are fairly insensitive to camera length and orientation.