Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability

Directory of Open Access Journals (Sweden)

C. Krafft

Full Text Available Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field, the fan instability can excite VLF waves (whistlers and lower hybrid waves with characteristics close to those observed in space experiments.

Key words. Space plasma physics (waves and instabilities – Radio Science (waves in plasma – Solar physics, astrophysics and astronomy (radio emissions

Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability

Directory of Open Access Journals (Sweden)

C. Krafft

2003-07-01

Full Text Available Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field, the fan instability can excite VLF waves (whistlers and lower hybrid waves with characteristics close to those observed in space experiments.Key words. Space plasma physics (waves and instabilities – Radio Science (waves in plasma – Solar physics, astrophysics and astronomy (radio emissions

Supra-thermal charged particle energies in a low pressure radio-frequency electrical discharge in air

International Nuclear Information System (INIS)

Littlefield, R.G.

1976-01-01

Velocity spectra of supra-thermal electrons escaping from a low-pressure radio-frequency discharge in air have been measured by a time-of-flight method of original design. In addition, the energy spectra of the supra-thermal electrons and positive ions escaping from the rf discharge have been measured by a retarding potential method. Various parameters affecting the energy of the supra-thermal charged particles are experimentally investigated. A model accounting for the supra-thermal charged particle energies is developed and is shown to be consistent with experimental observations

Measurement and modelling of suprathermal electron bursts generated in front of a lower hybrid antenna

Czech Academy of Sciences Publication Activity Database

Gunn, J. P.; Fuchs, Vladimír; Petržílka, Václav; Ekedahl, A.; Fedorczak, N.; Goniche, M.; Hillairet, J.

2016-01-01

Roč. 56, č. 3 (2016), č. článku 036004. ISSN 0029-5515 R&D Projects: GA MŠk(CZ) LM2011021 Institutional support: RVO:61389021 Keywords : lower hybrid * scrape off layer * SOL turbulence * Landau damping * suprathermal electrons 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/10.1088/0029-5515/56/3/036004

Quiet-time Suprathermal (~0.1-1.5 keV) Electrons in the Solar Wind

Science.gov (United States)

Tao, Jiawei; Wang, Linghua; Zong, Qiugang; Li, Gang; Salem, Chadi S.; Wimmer-Schweingruber, Robert F.; He, Jiansen; Tu, Chuanyi; Bale, Stuart D.

2016-03-01

We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ˜0.1-1.5 keV to a Kappa distribution function with an index κ and effective temperature Teff. We also calculate the number density n and average energy Eavg of strahl and halo electrons by integrating the electron measurements between ˜0.1 and 1.5 keV. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity).

Suprathermal electron loss cone distributions in the solar wind: Ulysses observations

International Nuclear Information System (INIS)

Phillips, J. L.; Feldman, W. C.; Gosling, J. T.; Hammond, C. M.; Forsyth, R. J.

1996-01-01

We present observations by the Ulysses solar wind plasma experiment of a new class of suprathermal electron signatures. At low solar latitudes and heliocentric distances beyond 3.37 AU Ulysses encountered seven intervals, ranging in duration from 1 hour to 22 hours, in which the suprathermal distributions included an antisunward field-aligned beam and a return population with a flux dropout typically spanning ±60 deg. from the sunward field-aligned direction. All events occurred between the forward and reverse shocks or waves bounding corotating interaction regions (CIRs). The observations support a scenario in which the sunward-moving electrons result from reflection of the prevailing antisunward field-aligned beam at magnetic field compressions downstream from the spacecraft, with wide loss cones caused by the relatively weak mirror ratio. This hypothesis requires that the field magnitude within the CIRs actually increased locally with increasing field-aligned distance from the Sun

Suprathermal electron environment of comet 67P/Churyumov-Gerasimenko: Observations from the Rosetta Ion and Electron Sensor

Science.gov (United States)

Clark, G.; Broiles, T. W.; Burch, J. L.; Collinson, G. A.; Cravens, T.; Frahm, R. A.; Goldstein, J.; Goldstein, R.; Mandt, K.; Mokashi, P.; Samara, M.; Pollock, C. J.

2015-11-01

Context. The Rosetta spacecraft is currently escorting comet 67P/Churyumov-Gerasimenko until its perihelion approach at 1.2 AU. This mission has provided unprecedented views into the interaction of the solar wind and the comet as a function of heliocentric distance. Aims: We study the interaction of the solar wind and comet at large heliocentric distances (>2 AU) using data from the Rosetta Plasma Consortium Ion and Electron Sensor (RPC-IES). From this we gain insight into the suprathermal electron distribution, which plays an important role in electron-neutral chemistry and dust grain charging. Methods: Electron velocity distribution functions observed by IES fit to functions used to previously characterize the suprathermal electrons at comets and interplanetary shocks. We used the fitting results and searched for trends as a function of cometocentric and heliocentric distance. Results: We find that interaction of the solar wind with this comet is highly turbulent and stronger than expected based on historical studies, especially for this weakly outgassing comet. The presence of highly dynamical suprathermal electrons is consistent with observations of comets (e.g., Giacobinni-Zinner, Grigg-Skjellerup) near 1 AU with higher outgassing rates. However, comet 67P/Churyumov-Gerasimenko is much farther from the Sun and appears to lack an upstream bow shock. Conclusions: The mass loading process, which likely is the cause of these processes, plays a stronger role at large distances from the Sun than previously expected. We discuss the possible mechanisms that most likely are responsible for this acceleration: heating by waves generated by the pick-up ion instability, and the admixture of cometary photoelectrons.

Shaping the solar wind electron temperature anisotropy by the interplay of core and suprathermal populations

Science.gov (United States)

Shaaban Hamd, S. M.; Lazar, M.; Poedts, S.; Pierrard, V.; Štverák

2017-12-01

We present the results of an advanced parametrization of the temperature anisotropy of electrons in the slow solar wind and the electromagnetic instabilities resulting from the interplay of their thermal core and suprathermal halo populations. A large set of observational data (from the Ulysses, Helios and Cluster missions) is used to parametrize these components and establish their correlations. Comparative analysis demonstrates for the first time a particular implication of the suprathermal electrons which are less dense but hotter than thermal electrons. The instabilities are significantly stimulated by the interplay of the core and halo populations, leading to lower thresholds which shape the observed limits of the temperature anisotropy for both the core and halo populations. This double agreement strongly suggests that the selfgenerated instabilities play the major role in constraining the electron anisotropy.

Ignition and burn propagation with suprathermal electron auxiliary heating

International Nuclear Information System (INIS)

Han Shensheng; Wu Yanqing

2000-01-01

The rapid development in ultrahigh-intensity lasers has allowed the exploration of applying an auxiliary heating technique in inertial confinement fusion (ICF) research. It is hoped that, compared with the 'standard fast ignition' scheme, raising the temperature of a hot-spot over the ignition threshold based on the shock-heated temperature will greatly reduce the required output energy of an ignition ultrahigh-intensity pulse. One of the key issues in ICF auxiliary heating is: how can we transport the exogenous energy efficiently into the hot-spot of compressed DT fuel? A scheme is proposed with three phases. First, a partial-spherical-shell capsule, such as double-conical target, is imploded as in the conventional approach to inertial fusion to assemble a high-density fuel configuration with a hot-spot of temperature lower than the ignition threshold. Second, a hole is bored through the shell outside the hot-spot by suprathermal electron explosion boring. Finally, the fuel is ignited by suprathermal electrons produced in the high-intensity ignition laser-plasma interactions. Calculations with a simple hybrid model show that the new scheme can possibly lead to ignition and burn propagation with a total drive energy of a few tens of kilojoules and an output energy as low as hundreds of joules for a single ignition ultrahigh-intensity pulse. (author)

SUPRATHERMAL ELECTRONS IN THE SOLAR CORONA: CAN NONLOCAL TRANSPORT EXPLAIN HELIOSPHERIC CHARGE STATES?

International Nuclear Information System (INIS)

Cranmer, Steven R.

2014-01-01

There have been several ideas proposed to explain how the Sun's corona is heated and how the solar wind is accelerated. Some models assume that open magnetic field lines are heated by Alfvén waves driven by photospheric motions and dissipated after undergoing a turbulent cascade. Other models posit that much of the solar wind's mass and energy is injected via magnetic reconnection from closed coronal loops. The latter idea is motivated by observations of reconnecting jets and also by similarities of ion composition between closed loops and the slow wind. Wave/turbulence models have also succeeded in reproducing observed trends in ion composition signatures versus wind speed. However, the absolute values of the charge-state ratios predicted by those models tended to be too low in comparison with observations. This Letter refines these predictions by taking better account of weak Coulomb collisions for coronal electrons, whose thermodynamic properties determine the ion charge states in the low corona. A perturbative description of nonlocal electron transport is applied to an existing set of wave/turbulence models. The resulting electron velocity distributions in the low corona exhibit mild suprathermal tails characterized by ''kappa'' exponents between 10 and 25. These suprathermal electrons are found to be sufficiently energetic to enhance the charge states of oxygen ions, while maintaining the same relative trend with wind speed that was found when the distribution was assumed to be Maxwellian. The updated wave/turbulence models are in excellent agreement with solar wind ion composition measurements

Generation of Suprathermal Electrons by Collective Processes in Collisional Plasma

Science.gov (United States)

Tigik, S. F.; Ziebell, L. F.; Yoon, P. H.

2017-11-01

The ubiquity of high-energy tails in the charged particle velocity distribution functions (VDFs) observed in space plasmas suggests the existence of an underlying process responsible for taking a fraction of the charged particle population out of thermal equilibrium and redistributing it to suprathermal velocity and energy ranges. The present Letter focuses on a new and fundamental physical explanation for the origin of suprathermal electron velocity distribution function (EVDF) in a collisional plasma. This process involves a newly discovered electrostatic bremsstrahlung (EB) emission that is effective in a plasma in which binary collisions are present. The steady-state EVDF dictated by such a process corresponds to a Maxwellian core plus a quasi-inverse power-law tail, which is a feature commonly observed in many space plasma environments. In order to demonstrate this, the system of self-consistent particle- and wave-kinetic equations are numerically solved with an initially Maxwellian EVDF and Langmuir wave spectral intensity, which is a state that does not reflect the presence of EB process, and hence not in force balance. The EB term subsequently drives the system to a new force-balanced steady state. After a long integration period it is demonstrated that the initial Langmuir fluctuation spectrum is modified, which in turn distorts the initial Maxwellian EVDF into a VDF that resembles the said core-suprathermal VDF. Such a mechanism may thus be operative at the coronal source region, which is characterized by high collisionality.

QUIET-TIME SUPRATHERMAL (∼0.1–1.5 keV) ELECTRONS IN THE SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Tao, Jiawei; Wang, Linghua; Zong, Qiugang; He, Jiansen; Tu, Chuanyi [School of Earth and Space Science, Peking University, Beijing 100871 (China); Li, Gang [Department of Physics and CSPAR, University of Alabama in Huntsville, Alabama 35899 (United States); Salem, Chadi S.; Bale, Stuart D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Wimmer-Schweingruber, Robert F., E-mail: wanglhwang@gmail.com [Institute for Experimental and Applied Physics, University of Kiel, Leibnizstrasse 11, D-24118 Kiel (Germany)

2016-03-20

We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1–1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ∼0.1–1.5 keV to a Kappa distribution function with an index κ and effective temperature T{sub eff}. We also calculate the number density n and average energy E{sub avg} of strahl and halo electrons by integrating the electron measurements between ∼0.1 and 1.5 keV. We find a strong positive correlation between κ and T{sub eff} for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity)

SUPRATHERMAL ELECTRONS IN TITAN’S SUNLIT IONOSPHERE: MODEL–OBSERVATION COMPARISONS

Energy Technology Data Exchange (ETDEWEB)

Vigren, E.; Edberg, N. J. T.; Wahlund, J.-E. [Swedish Institute of Space Physics, Uppsala (Sweden); Galand, M.; Sagnières, L. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Wellbrock, A.; Coates, A. J. [Mullard Space Science Laboratory, University College London, Dorking, Surrey RH5 6NT (United Kingdom); Cui, J. [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Lavvas, P. [Université Reims Champagne-Ardenne, Reims (France); Snowden, D. [Department of Physics, Central Washington University, Ellensburg, WA 98926 (United States); Vuitton, V., E-mail: erik.vigren@irfu.se [Univ. Grenoble Alpes, CNRS, IPAG, Grenoble (France)

2016-08-01

The dayside ionosphere of the Saturnian satellite Titan is generated mainly from photoionization of N{sub 2} and CH{sub 4}. We compare model-derived suprathermal electron intensities with spectra measured by the Cassini Plasma Spectrometer/Electron Spectrometer (CAPS/ELS) in Titan's sunlit ionosphere (altitudes of 970–1250 km) focusing on the T40, T41, T42, and T48 Titan flybys by the Cassini spacecraft. The model accounts only for photoelectrons and associated secondary electrons, with a main input being the impinging solar EUV spectra as measured by the Thermosphere Ionosphere Mesosphere Energy and Dynamics/Solar EUV Experiment and extrapolated to Saturn. Associated electron-impact electron production rates have been derived from ambient number densities of N{sub 2} and CH{sub 4} (measured by the Ion Neutral Mass Spectrometer/Closed Source Neutral mode) and related energy-dependent electron-impact ionization cross sections. When integrating up to electron energies of 60 eV, covering the bulk of the photoelectrons, the model-based values exceed the observationally based values typically by factors of ∼3 ± 1. This finding is possibly related to current difficulties in accurately reproducing the observed electron number densities in Titan's dayside ionosphere. We compare the utilized dayside CAPS/ELS spectra with ones measured in Titan's nightside ionosphere during the T55–T59 flybys. The investigated nightside locations were associated with higher fluxes of high-energy (>100 eV) electrons than the dayside locations. As expected, for similar neutral number densities, electrons with energies <60 eV give a higher relative contribution to the total electron-impact ionization rates on the dayside (due to the contribution from photoelectrons) than on the nightside.

Investigation of the role of electron cyclotron resonance heating and magnetic configuration on the suprathermal ion population in the stellarator TJ-II using a luminescent probe

Science.gov (United States)

Martínez, M.; Zurro, B.; Baciero, A.; Jiménez-Rey, D.; Tribaldos, V.

2018-02-01

Numerous observation exist of a population of high energetic ions with energies well above the corresponding thermal values in plasmas generated by electron cyclotron resonance (ECR) heating in TJ-II stellarator and in other magnetically confined plasmas devices. In this work we study the impact of ECR heating different conditions (positions and powers) on fast ions escaping from plasmas in the TJ-II stellarator. For this study, an ion luminescent probe operated in counting mode is used to measure the energy distribution of suprathermal ions, in the range from 1 to 30 keV. It is observed that some suprathermal ions characteristics (such as temperature, particle and energy fluxes) are related directly with the gyrotron power and focus position of the heating beam in the plasma. Moreover, it is found that suprathermal ion characteristics vary during a magnetic configuration scan (performed along a single discharge). By investigating the suprathermal ions escaping from plasmas generated using two gyrotrons, one with fixed power and the other modulated (on/off) at low frequency (10 Hz), the de-confinement time of the suprathermal ions can be measured, which is of the order of a few milliseconds (power balance is used to understand the de-confinement times in terms of the interaction of suprathermal ions and plasma components. This model also can be used to interpret experimental results of energy loss due to suprathermal ions. Finally, observations of increases (peaks) in the population of escaping suprathermal ions, which are well localized at discrete energies, is documented, these peaks being observed in the energy distributions along a discharge.

Suprathermal ion transport in turbulent magnetized plasmas

International Nuclear Information System (INIS)

Bovet, A. D.

2015-01-01

Suprathermal ions, which have an energy greater than the quasi-Maxwellian background plasma temperature, are present in many laboratory and astrophysical plasmas. In fusion devices, they are generated by the fusion reactions and auxiliary heating. Controlling their transport is essential for the success of future fusion devices that could provide a clean, safe and abundant source of electric power to our society. In space, suprathermal ions include energetic solar particles and cosmic rays. The understanding of the acceleration and transport mechanisms of these particles is still incomplete. Basic plasma devices allow detailed measurements that are not accessible in astrophysical and fusion plasmas, due to the difficulty to access the former and the high temperatures of the latter. The basic toroidal device TORPEX offers an easy access for diagnostics, well characterized plasma scenarios and validated numerical simulations of its turbulence dynamics, making it the ideal platform for the investigation of suprathermal ion transport. This Thesis presents three-dimensional measurements of a suprathermal ion beam injected in turbulent TORPEX plasmas. The combination of uniquely resolved measurements and first principle numerical simulations reveals the general non-diffusive nature of the suprathermal ion transport. A precise characterization of their transport regime shows that, depending on their energies, suprathermal ions can experience either a super diffusive transport or a subdiffusive transport in the same background turbulence. The transport character is determined by the interaction of the suprathermal ion orbits with the turbulent plasma structures, which in turn depends on the ratio between the ion energy and the background plasma temperature. Time-resolved measurements reveal a clear difference in the intermittency of suprathermal ions time-traces depending on the transport regime they experience. Conditionally averaged measurements uncover the influence of

Microwave heating and diagnostic of suprathermal electrons in an overdense stellarator plasma

International Nuclear Information System (INIS)

Stange, Torsten

2014-01-01

The resonant coupling of microwaves into a magnetically confined plasma is one of the fundamental methods for the heating of such plasmas. Identifying and understanding the processes of the heating of overdense plasmas, in which the wave propagation is generally not possible because the wave frequency is below the plasma frequency, is becoming increasingly important for high density fusion plasmas. This work focuses on the heating of overdense plasmas in the WEGA stellarator. The excitation of electron Bernstein waves, utilizing the OXB-conversion process, provides a mechanism for the wave to reach the otherwise not accessible resonant absorption layer. In WEGA these OXB-heated plasmas exhibit a suprathermal electron component with energies up to 80 keV. The fast electrons are located in the plasma center and have a Maxwellian energy distribution function within the soft X-ray related energy range. The corresponding averaged energy is a few keV. The OXB-discharges are accompanied by a broadband microwave radiation spectrum with radiation temperatures of the order of keV. Its source was identified as a parametric decay of the heating wave and has no connection to the suprathermal electron component. For the detailed investigation of the microwave emission, a quasioptical mirror system, optimized for the OX-conversion, has been installed. Based on the measurement of the broadband microwave stray radiation of the decay process, the OX-conversion efficiency has been determined to 0.56 being in good agreement with full-wave calculations. In plasmas without an electron cyclotron resonance, corresponding to the wave frequency used, non-resonant heating mechanisms have been identified in the overdense plasma regions. Whistler waves or R-like waves are the only propagable wave types within the overdense plasmas. The analysis of the heating efficiency in dependence on the magnetic flux density leads to tunneling as the most probable coupling mechanism. For the determination

Statistics of counter-streaming solar wind suprathermal electrons at solar minimum: STEREO observations

Directory of Open Access Journals (Sweden)

B. Lavraud

2010-01-01

Full Text Available Previous work has shown that solar wind suprathermal electrons can display a number of features in terms of their anisotropy. Of importance is the occurrence of counter-streaming electron patterns, i.e., with "beams" both parallel and anti-parallel to the local magnetic field, which is believed to shed light on the heliospheric magnetic field topology. In the present study, we use STEREO data to obtain the statistical properties of counter-streaming suprathermal electrons (CSEs in the vicinity of corotating interaction regions (CIRs during the period March–December 2007. Because this period corresponds to a minimum of solar activity, the results are unrelated to the sampling of large-scale coronal mass ejections, which can lead to CSE owing to their closed magnetic field topology. The present study statistically confirms that CSEs are primarily the result of suprathermal electron leakage from the compressed CIR into the upstream regions with the combined occurrence of halo depletion at 90° pitch angle. The occurrence rate of CSE is found to be about 15–20% on average during the period analyzed (depending on the criteria used, but superposed epoch analysis demonstrates that CSEs are preferentially observed both before and after the passage of the stream interface (with peak occurrence rate >35% in the trailing high speed stream, as well as both inside and outside CIRs. The results quantitatively show that CSEs are common in the solar wind during solar minimum, but yet they suggest that such distributions would be much more common if pitch angle scattering were absent. We further argue that (1 the formation of shocks contributes to the occurrence of enhanced counter-streaming sunward-directed fluxes, but does not appear to be a necessary condition, and (2 that the presence of small-scale transients with closed-field topologies likely also contributes to the occurrence of counter-streaming patterns, but only in the slow solar wind prior to

Study of the thermal and suprathermal electron density fluctuations of the plasma in the Focus experiment

International Nuclear Information System (INIS)

Jolas, A.

1981-10-01

An experiment on Thomson scattering of ruby laser light by the electrons of a plasma produced by an intense discharge between the electrodes of a coaxial gun in a gas at low pressure has been carried out. It is shown that the imploding plasma is made up of layers with different characteristics: a dense plasma layer where the density fluctuations are isotropic and have a thermal level, and a tenuous plasma layer where the fluctuations are anisotropic, and strongly suprathermal. The suprathermal fluctuations are attributed to microscopic instabilities generated by the electric current circulating in the transition zone where the magnetic field penetrates the plasma [fr

Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.

Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

1998-10-01

Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

Study of profile control and suprathermal electron production with lower hybrid waves

International Nuclear Information System (INIS)

Soeldner, F.X.; Brambilla, M.; Leuterer, F.; Muenich, M.

1986-05-01

In this study the coupling of LH waves to suprathermal electrons, the LH current drive efficiency and the mechanism for sawtooth stabilisation will be discussed. A wide data base has been obtained by the LH experiments on Alcator C, ASDEX, FT; JFT-2M, JIPPT-IIU, Petula, PLT, Versator, WT II during the last years and important aspects as the scaling of global current drive efficiency are satisfactorily described by theory. We mainly rely here on experimental results from ASDEX and comparison with theoretical calculations by Fisch and Karney. (orig.)

Generation of suprathermal electrons during plasma current startup by lower hybrid waves in a tokamak

International Nuclear Information System (INIS)

Ohkubo, K.; Toi, K.; Kawahata, K.

1984-10-01

Suprathermal electrons which carry a seed current are generated by non-resonant parametric decay instability during initial phase of lower hybrid current startup in the JIPP T-IIU tokamak. From the numerical analysis, it is found that parametrically excited lower hybrid waves at lower side band can bridge the spectral gap between the thermal velocity and the low velocity end in the pump power spectrum. (author)

Nonlinear dust acoustic waves in a charge varying dusty plasma with suprathermal electrons

International Nuclear Information System (INIS)

Tribeche, Mouloud; Bacha, Mustapha

2010-01-01

Arbitrary amplitude dust acoustic waves in a dusty plasma with a high-energy-tail electron distribution are investigated. The effects of charge variation and electron deviation from the Boltzmann distribution on the dust acoustic soliton are then considered. The dust charge variation makes the dust acoustic soliton more spiky. The dust grain surface collects less electrons as the latter evolves far away from their thermodynamic equilibrium. The dust accumulation caused by a balance of the electrostatic forces acting on the dust grains is more effective for lower values of the electron spectral index. Under certain conditions, the dust charge fluctuation may provide an alternate physical mechanism causing anomalous dissipation, the strength of which becomes important and may prevail over that of dispersion as the suprathermal character of the plasma becomes important. Our results may explain the strong spiky waveforms observed in auroral plasmas.

Effects of ionization and ion loss on dust ion- acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

Science.gov (United States)

Tribeche, Mouloud; Mayout, Saliha

2016-07-01

The combined effects of ionization, ion loss and electron suprathermality on dust ion- acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg- de Vries (dK-- dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK- dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the DIA solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

Stereo ENA Imaging of the Ring Current and Multi-point Measurements of Suprathermal Particles and Magnetic Fields by TRIO-CINEMA

Science.gov (United States)

Lin, R. P.; Sample, J. G.; Immel, T. J.; Lee, D.; Horbury, T. S.; Jin, H.; SEON, J.; Wang, L.; Roelof, E. C.; Lee, E.; Parks, G. K.; Vo, H.

2012-12-01

The TRIO (Triplet Ionospheric Observatory) - CINEMA (Cubesat for Ions, Neutrals, Electrons, & Magnetic fields) mission consists of three identical 3-u cubesats to provide high sensitivity, high cadence, stereo measurements of Energetic Neutral Atoms (ENAs) from the Earth's ring current with ~1 keV FWHM energy resolution from ~4 to ~200 keV, as well as multi-point in situ measurements of magnetic fields and suprathermal electrons (~2 -200 keV) and ions (~ 4 -200 keV) in the auroral and ring current precipitation regions in low Earth orbit (LEO). A new Suprathermal Electron, Ion, Neutral (STEIN) instrument, using a 32-pixel silicon semiconductor detector with an electrostatic deflection system to separate ENAs from ions and from electrons below 30 keV, will sweep over most of the sky every 15 s as the spacecraft spins at 4 rpm. In addition, inboard and outboard (on an extendable 1m boom) miniature magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. An S-band transmitter will be used to provide ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station.The first CINEMA (funded by NSF) is scheduled for launch on August 14, 2012 into a 65 deg. inclination LEO. Two more identical CINEMAs are being developed by Kyung Hee University (KHU) in Korea under the World Class University (WCU) program, for launch in November 2012 into a Sun-synchronous LEO to form TRIO-CINEMA. A fourth CINEMA is being developed for a 2013 launch into LEO. This LEO constellation of nanosatellites will provide unique measurements highly complementary to NASA's RBSP and THEMIS missions. Furthermore, CINEMA's development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft may be important for future constellation space missions. Initial results from the first CINEMA will be presented if available.

Suprathermal Electron Generation and Channel Formation by an Ultrarelativistic Laser Pulse in an Underdense Preformed Plasma

International Nuclear Information System (INIS)

Malka, G.; Gaillard, R.; Miquel, J.L.; Rousseaux, C.; Bonnaud, G.; Busquet, M.; Lours, L.; Fuchs, J.; Pepin, H.; Fuchs, J.; Amiranoff, F.; Baton, S.D.

1997-01-01

Relativistic electrons are produced, with energies up to 20MeV, by the interaction of a high-intensity subpicosecond laser pulse (1 μm , 300 fs , 10 19 W/cm 2 ) with an underdense plasma. Two suprathermal electron populations appear with temperatures of 1 and 3MeV. In the same conditions, the laser beam transmission is increased up to 20% 30%. We observe both features along with the evidence of laser pulse channeling. A fluid model predicts a strong self-focusing of the pulse. Acceleration in the enhanced laser field seems the most likely mechanism leading to the second electron population. copyright 1997 The American Physical Society

Effects of ionization and ion loss on dust ion-acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

Energy Technology Data Exchange (ETDEWEB)

Mayout, Saliha; Gougam, Leila Ait [Faculty of Physics, Theoretical Physics Laboratory, Plasma Physics Group, University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria); Tribeche, Mouloud, E-mail: mouloudtribeche@yahoo.fr, E-mail: mtribeche@usthb.dz [Faculty of Physics, Theoretical Physics Laboratory, Plasma Physics Group, University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria); Algerian Academy of Sciences and Technologies, Algiers (Algeria)

2016-03-15

The combined effects of ionization, ion loss, and electron suprathermality on dust ion-acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg-de Vries (dK–dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK-dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the dust ion-acoustic solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

Effects of ionization and ion loss on dust ion-acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

International Nuclear Information System (INIS)

Mayout, Saliha; Gougam, Leila Ait; Tribeche, Mouloud

2016-01-01

The combined effects of ionization, ion loss, and electron suprathermality on dust ion-acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg-de Vries (dK–dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK-dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the dust ion-acoustic solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

ITER Plasma at Electron Cyclotron Frequency Domain: Stimulated Raman Scattering off Gould-Trivelpiece Modes and Generation of Suprathermal Electrons and Energetic Ions

Science.gov (United States)

Stefan, V. Alexander

2011-04-01

Stimulated Raman scattering in the electron cyclotron frequency range of the X-Mode and O-Mode driver with the ITER plasma leads to the ``tail heating'' via the generation of suprathermal electrons and energetic ions. The scattering off Trivelpiece-Gould (T-G) modes is studied for the gyrotron frequency of 170GHz; X-Mode and O-Mode power of 24 MW CW; on-axis B-field of 10T. The synergy between the two-plasmon decay and Raman scattering is analyzed in reference to the bulk plasma heating. Supported in part by Nikola TESLA Labs, La Jolla, CA

Statistical analysis of suprathermal electron drivers at 67P/Churyumov-Gerasimenko

Science.gov (United States)

Broiles, Thomas W.; Burch, J. L.; Chae, K.; Clark, G.; Cravens, T. E.; Eriksson, A.; Fuselier, S. A.; Frahm, R. A.; Gasc, S.; Goldstein, R.; Henri, P.; Koenders, C.; Livadiotis, G.; Mandt, K. E.; Mokashi, P.; Nemeth, Z.; Odelstad, E.; Rubin, M.; Samara, M.

2016-11-01

We use observations from the Ion and Electron Sensor (IES) on board the Rosetta spacecraft to study the relationship between the cometary suprathermal electrons and the drivers that affect their density and temperature. We fit the IES electron observations with the summation of two kappa distributions, which we characterize as a dense and warm population (˜10 cm-3 and ˜16 eV) and a rarefied and hot population (˜0.01 cm-3 and ˜43 eV). The parameters of our fitting technique determine the populations' density, temperature, and invariant kappa index. We focus our analysis on the warm population to determine its origin by comparing the density and temperature with the neutral density and magnetic field strength. We find that the warm electron population is actually two separate sub-populations: electron distributions with temperatures above 8.6 eV and electron distributions with temperatures below 8.6 eV. The two sub-populations have different relationships between their density and temperature. Moreover, the two sub-populations are affected by different drivers. The hotter sub-population temperature is strongly correlated with neutral density, while the cooler sub-population is unaffected by neutral density and is only weakly correlated with magnetic field strength. We suggest that the population with temperatures above 8.6 eV is being heated by lower hybrid waves driven by counterstreaming solar wind protons and newly formed, cometary ions created in localized, dense neutral streams. To the best of our knowledge, this represents the first observations of cometary electrons heated through wave-particle interactions.

Heating and generation of suprathermal particles at collisionless shocks

International Nuclear Information System (INIS)

Thomsen, M.F.

1985-01-01

Collisionless plasma shocks are different from ordinary collisional fluid shocks in several important respects. They do not in general heat the electrons and ions equally, nor do they produce Maxwellian velocity distributions downstream. Furthermore, they commonly generate suprathermal particles which propagate into the upstream region, giving advance warning of the presence of the shock and providing a ''seed'' population for further acceleration to high energies. Recent space observations and theory have revealed a great deal about the heating mechanisms which occur in collisionless shocks and about the origin of the various suprathermal particle populations which are found in association with them. An overview of the present understanding of these subjects is presented herein. 83 refs., 8 figs

Suprathermal viscosity of dense matter

International Nuclear Information System (INIS)

Alford, Mark; Mahmoodifar, Simin; Schwenzer, Kai

2010-01-01

Motivated by the existence of unstable modes of compact stars that eventually grow large, we study the bulk viscosity of dense matter, taking into account non-linear effects arising in the large amplitude regime, where the deviation μ Δ of the chemical potentials from chemical equilibrium fulfills μ Δ > or approx. T. We find that this supra-thermal bulk viscosity can provide a potential mechanism for saturating unstable modes in compact stars since the viscosity is strongly enhanced. Our study confirms previous results on strange quark matter and shows that the suprathermal enhancement is even stronger in the case of hadronic matter. We also comment on the competition of different weak channels and the presence of suprathermal effects in various color superconducting phases of dense quark matter.

Electron cyclotron emission measurements during 28 GHz electron cyclotron resonance heating in Wendelstein WVII-A stellarator

International Nuclear Information System (INIS)

Hartfuss, H.J.; Gasparino, U.; Tutter, M.; Brakel, R.; Cattanei, G.; Dorst, D.; Elsner, A.; Engelhardt, K.; Erckmann, V.; Grieger, G.; Grigull, P.; Hacker, H.; Jaeckel, H.; Jaenicke, R.; Junker, J.; Kick, M.; Kroiss, H.; Kuehner, G.; Maassberg, H.; Mahn, C.; Mueller, G.; Ohlendorf, W.; Rau, F.; Renner, H.; Ringler, H.; Sardei, F.; Weller, A.; Wobig, H.; Wuersching, E.; Zippe, M.; Kasparek, W.; Mueller, G.A.; Raeuchle, E.; Schueller, P.G.; Schwoerer, K.; Thumm, M.

1987-11-01

Electron cyclotron emission measurements have been carried out on electron cyclotron resonance heated plasmas in the WENDELSTEIN VII-A Stellarator. Blackbody radiation from the thermalized plasma main body as well as radiation from a small amount of weakly relativistic suprathermal electrons has been detected. In addition sideband emission has been observed near the second harmonic of the heating line source. Harmonic generation and parametric wave decay at the upper hybrid layer may be a reasonable explanation. (orig.)

Time Variations of the Spectral Indices of the Suprathermal Distribution as observed by WIND/STICS

Science.gov (United States)

Gruesbeck, J. R.; Christian, E. R.; Lepri, S. T.; Thomas, J.; Zurbuchen, T.; Gloeckler, G.

2011-12-01

Suprathermal particle spectra, measured in various regions of the heliosphere and heliosheath by Ulysses, ACE and Voyager, have recently been reported. In many cases long accumulation times had to be used to obtain sufficient statistical accuracy, and corrections were necessary, since only a fraction of phase space was measured. The SupraThermal Ion Composition Spectrometer (STICS), onboard Wind, enables observations of the suprathermal plasma in the solar wind at much higher time resolution. In addition, the STICS samples nearly full three-dimensional phase space, enabling measurements of anisotropies. We present a multi-year investigation of the spectral index of the suprathermal distribution, accumulated over 1 day and less, where we see significant time variation. An average lower bound value of the spectral index is at ~ -5, however, there are time periods during which the observed distributions steepen. We will also present an analysis of time and spatial variations of the suprathermal particle fluxes, observed by STICS and other instruments. In particular, we will compare the observed variability with predictions from a model by Bochsler and Moebius, based on data of the Interstellar Boundary Explorer (IBEX), who postulated that energetic neutral atoms, from outside of the heliosheath, which then penetrate the inner heliosphere and are finally ionized, could be a source of the very suprathermal populations we observe.

Suprathermal electron production in laser-irradiated Cu targets characterized by combined methods of x-ray imaging and spectroscopy

Czech Academy of Sciences Publication Activity Database

Renner, Oldřich; Šmíd, Michal; Batani, D.; Antonelli, L.

2016-01-01

Roč. 58, č. 7 (2016), 1-8, č. článku 075007. ISSN 0741-3335 R&D Projects: GA MŠk LQ1606; GA MŠk EF15_008/0000162; GA MŠk(CZ) LD14089 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : laser- plasma interaction * inertial confinement fusion * suprathermal electron Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.392, year: 2016

New Measurements of Suprathermal Ions, Energetic Particles, and Cosmic Rays in the Outer Heliosphere from the New Horizons PEPSSI Instrument

Science.gov (United States)

Hill, M. E.; Kollmann, P.; McNutt, R. L., Jr.; Stern, A.; Weaver, H. A., Jr.; Young, L. A.; Olkin, C.; Spencer, J. R.

2017-12-01

During the period from January 2012 to December 2017 the New Horizons spacecraft traveled from 22 to 41 AU from the Sun, making nearly continuous interplanetary plasma and particle measurements utilizing the SWAP and PEPSSI instruments. We report on newly extended measurements from PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) that now bring together suprathermal particles above 2 keV/nuc (including interstellar pickup ions), energetic particles with H, He, and O composition from 30 keV to 1 MeV, and cosmic rays above 65 MeV (with effective count-rate-limited upper energy of 1 GeV). Such a wide energy range allows us to look at the solar wind structures passing over the spacecraft, the energetic particles that are often accelerated by these structures, and the suppression of cosmic rays resulting from the increased turbulence inhibiting cosmic ray transport to the spacecraft position (i.e., Forbush decreases). This broad perspective provides simultaneous, previously unattainable diagnostics of outer heliospheric particle dynamics and acceleration. Besides the benefit of being recent, in-ecliptic measurements, unlike the historic Voyager 1 and 2 spacecraft, these PEPSSI observations are also totally unique in the suprathermal range; in this region only PEPSSI can span the suprathermal range, detecting a population that is a linchpin to understanding the outer heliosphere.

MAVEN SupraThermal and Thermal Ion Compostion (STATIC) Instrument

Science.gov (United States)

McFadden, J. P.; Kortmann, O.; Curtis, D.; Dalton, G.; Johnson, G.; Abiad, R.; Sterling, R.; Hatch, K.; Berg, P.; Tiu, C.; Gordon, D.; Heavner, S.; Robinson, M.; Marckwordt, M.; Lin, R.; Jakosky, B.

2015-12-01

The MAVEN SupraThermal And Thermal Ion Compostion (STATIC) instrument is designed to measure the ion composition and distribution function of the cold Martian ionosphere, the heated suprathermal tail of this plasma in the upper ionosphere, and the pickup ions accelerated by solar wind electric fields. STATIC operates over an energy range of 0.1 eV up to 30 keV, with a base time resolution of 4 seconds. The instrument consists of a toroidal "top hat" electrostatic analyzer with a 360° × 90° field-of-view, combined with a time-of-flight (TOF) velocity analyzer with 22.5° resolution in the detection plane. The TOF combines a -15 kV acceleration voltage with ultra-thin carbon foils to resolve H+, He^{++}, He+, O+, O2+, and CO2+ ions. Secondary electrons from carbon foils are detected by microchannel plate detectors and binned into a variety of data products with varying energy, mass, angle, and time resolution. To prevent detector saturation when measuring cold ram ions at periapsis (˜10^{1 1} eV/cm2 s sr eV), while maintaining adequate sensitivity to resolve tenuous pickup ions at apoapsis (˜103 eV/cm2 s sr eV), the sensor includes both mechanical and electrostatic attenuators that increase the dynamic range by a factor of 103. This paper describes the instrument hardware, including several innovative improvements over previous TOF sensors, the ground calibrations of the sensor, the data products generated by the experiment, and some early measurements during cruise phase to Mars.

Suprathermal He2+ in the Earth's foreshock region

International Nuclear Information System (INIS)

Fuselier, S.A.; Thomsen, M.F.; Ipavich, F.M.; Schmidt, W.K.H.

1995-01-01

ISEE 1 and 2 H + and He 2+ observations upstream from the Earth's bow shock are used to investigate the origin of energetic (or diffuse) ion distributions. Diffuse ion distributions have energies from a few keV/e to > 100 keV/e and have near solar wind concentrations (i.e., an average of about 4% He 2+ ). These distributions may evolve from suprathermal ion distributions that have energies between 1 and a few keV/e. Upstream intervals were selected from the ISEE data to determine which suprathermal distributions have He 2+ concentrations similar to those of diffuse ion distributions. The type of distribution and the location in the foreshock were similar in all events studied. Two intervals that represent the results from this study are discussed in detail. The results suggest that diffuse ion distributions evolve from suprathermal distributions in the region upstream from the quasi-parallel bow shock. For He 2+ , the suprathermal distribution is a nongyrotropic partial ring beam and has characteristics consistent with specular reflection off the quasi-parallel bow shock. The suprathermal proton distributions associated with these He 2+ distributions are nongyrotropic partial ring beams or nearly gyrotropic ring beams also approximately consistent with specular reflection. The location in the quasi-parallel foreshock and the similarity of the suprathermal He 2+ and H + distributions suggest that these are the seed population for diffuse distributions in the foreshock region. 30 refs., 5 figs., 1 tab

SUPRATHERMAL ELECTRON STRAHL WIDTHS IN THE PRESENCE OF NARROW-BAND WHISTLER WAVES IN THE SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Kajdič, P. [Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico City (Mexico); Alexandrova, O.; Maksimovic, M.; Lacombe, C. [LESIA, Observatoire de Paris, PSL Research University, CNRS, UPMC UniversitéParis 06, Université Paris-Diderot, 5 Place Jules Janssen, F-92190 Meudon (France); Fazakerley, A. N., E-mail: primoz@geofisica.unam.mx [Mullard Space Science Laboratory, University College London (United Kingdom)

2016-12-20

We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind (SW). We show that this interaction does occur and that it is associated with enhanced widths of the so-called strahl component. The latter is directed along the interplanetary magnetic field away from the Sun. We do the study by comparing the strahl pitch angle widths in the SW at 1 AU in the absence of large scale discontinuities and transient structures, such as interplanetary shocks, interplanetary coronal mass ejections, stream interaction regions, etc. during times when the whistler mode waves were present and when they were absent. This is done by using the data from two Cluster instruments: Spatio Temporal Analysis of Field Fluctuations experiment (STAFF) data in the frequency range between ∼0.1 and ∼200 Hz were used for determining the wave properties and Plasma Electron And Current Experiment (PEACE) data sets at 12 central energies between ∼57 eV (equivalent to ∼10 typical electron thermal energies in the SW, E{sub T}) and ∼676 eV (∼113 E{sub T}) for pitch angle measurements. Statistical analysis shows that, during the intervals with the whistler waves, the strahl component on average exhibits pitch angle widths between 2° and 12° larger than during the intervals when these waves are not present. The largest difference is obtained for the electron central energy of ∼344 eV (∼57 ET).

SUPRATHERMAL ELECTRON STRAHL WIDTHS IN THE PRESENCE OF NARROW-BAND WHISTLER WAVES IN THE SOLAR WIND

International Nuclear Information System (INIS)

Kajdič, P.; Alexandrova, O.; Maksimovic, M.; Lacombe, C.; Fazakerley, A. N.

2016-01-01

We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind (SW). We show that this interaction does occur and that it is associated with enhanced widths of the so-called strahl component. The latter is directed along the interplanetary magnetic field away from the Sun. We do the study by comparing the strahl pitch angle widths in the SW at 1 AU in the absence of large scale discontinuities and transient structures, such as interplanetary shocks, interplanetary coronal mass ejections, stream interaction regions, etc. during times when the whistler mode waves were present and when they were absent. This is done by using the data from two Cluster instruments: Spatio Temporal Analysis of Field Fluctuations experiment (STAFF) data in the frequency range between ∼0.1 and ∼200 Hz were used for determining the wave properties and Plasma Electron And Current Experiment (PEACE) data sets at 12 central energies between ∼57 eV (equivalent to ∼10 typical electron thermal energies in the SW, E T ) and ∼676 eV (∼113 E T ) for pitch angle measurements. Statistical analysis shows that, during the intervals with the whistler waves, the strahl component on average exhibits pitch angle widths between 2° and 12° larger than during the intervals when these waves are not present. The largest difference is obtained for the electron central energy of ∼344 eV (∼57 ET).

Suprathermal grains: on intergalactic magnetic fields

International Nuclear Information System (INIS)

Dasgupta, A.K.

1979-01-01

Charged dust grains of radii a approximately equal to 3 x 10 -6 to approximately 3 x 10 -5 cm may be driven out of the galaxy due to radiation pressure of starlight. Once clear of the main gas-dust layer, dust grains may then escape into intergalactic space. Such grains are virtually indestructible-being evaporated only during formation. The dust grains, once injected into the intergalactic medium, may acquire suprathermal energy, thus 'suprathermal grains' in collision with magnetized cloud by the Fermi process. In order to attain relativistic energy, suprathermal grains have to move in and out ('scattering') of the magnetic field of the medium. It is now well established that high energy cosmic rays are of the order 10 20 eV or more. It has been speculated that these high energy (> = 10 18 eV) cosmic ray particles are charged dust grains, of intergalactic origin. This is possible only if there exists a magnetic field in the intergalactic medium. (Auth.)

Discovery of Suprathermal Fe+ in and near Earth's Magnetosphere

Science.gov (United States)

Christon, S. P.; Hamilton, D. C.; Plane, J. M. C.; Mitchell, D. G.; Grebowsky, J. M.; Spjeldvik, W. N.; Nylund, S. R.

2017-12-01

Suprathermal (87-212 keV/e) singly charged iron, Fe+, has been observed in and near Earth's equatorial magnetosphere using long-term ( 21 years) Geotail/STICS ion composition data. Fe+ is rare compared to dominant suprathermal solar wind and ionospheric origin heavy ions. Earth's suprathermal Fe+ appears to be positively associated with both geomagnetic and solar activity. Three candidate lower-energy sources are examined for relevance: ionospheric outflow of Fe+ escaped from ion layers altitude, charge exchange of nominal solar wind Fe+≥7, and/or solar wind transported inner source pickup Fe+ (likely formed by solar wind Fe+≥7 interaction with near sun interplanetary dust particles, IDPs). Semi-permanent ionospheric Fe+ layers form near 100 km altitude from the tons of IDPs entering Earth's atmosphere daily. Fe+ scattered from these layers is observed up to 1000 km altitude, likely escaping in strong ionospheric outflows. Using 26% of STICS's magnetosphere-dominated data at low-to-moderate geomagnetic activity levels, we demonstrate that solar wind Fe charge exchange secondaries are not an obvious Fe+ source then. Earth flyby and cruise data from Cassini/CHEMS, a nearly identical instrument, show that inner source pickup Fe+ is likely not important at suprathermal energies. Therefore, lacking any other candidate sources, it appears that ionospheric Fe+ constitutes at least an important portion of Earth's suprathermal Fe+, comparable to observations at Saturn where ionospheric origin suprathermal Fe+ has also been observed.

Suprathermal He{sup 2+} in the Earth`s foreshock region

Energy Technology Data Exchange (ETDEWEB)

Fuselier, S.A. [Lockheed Palo Alto Research Lab., CA (United States); Thomsen, M.F. [Los Alamos National Lab., NM (United States); Ipavich, F.M. [Univ. of Maryland, College Park, MD (United States); Schmidt, W.K.H. [Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany)

1995-09-01

ISEE 1 and 2 H{sup +} and He{sup 2+} observations upstream from the Earth`s bow shock are used to investigate the origin of energetic (or diffuse) ion distributions. Diffuse ion distributions have energies from a few keV/e to > 100 keV/e and have near solar wind concentrations (i.e., an average of about 4% He{sup 2+}). These distributions may evolve from suprathermal ion distributions that have energies between 1 and a few keV/e. Upstream intervals were selected from the ISEE data to determine which suprathermal distributions have He{sup 2+} concentrations similar to those of diffuse ion distributions. The type of distribution and the location in the foreshock were similar in all events studied. Two intervals that represent the results from this study are discussed in detail. The results suggest that diffuse ion distributions evolve from suprathermal distributions in the region upstream from the quasi-parallel bow shock. For He{sup 2+}, the suprathermal distribution is a nongyrotropic partial ring beam and has characteristics consistent with specular reflection off the quasi-parallel bow shock. The suprathermal proton distributions associated with these He{sup 2+} distributions are nongyrotropic partial ring beams or nearly gyrotropic ring beams also approximately consistent with specular reflection. The location in the quasi-parallel foreshock and the similarity of the suprathermal He{sup 2+} and H{sup +} distributions suggest that these are the seed population for diffuse distributions in the foreshock region. 30 refs., 5 figs., 1 tab.

Electron Energetics in the Martian Dayside Ionosphere: Model Comparisons with MAVEN Data

Science.gov (United States)

Sakai, Shotaro; Andersson, Laila; Cravens, Thomas E.; Mitchell, David L.; Mazelle, Christian; Rahmati, Ali; Fowler, Christopher M.; Bougher, Stephen W.; Thiemann, Edward M. B.; Epavier, Francis G.;

Discovery of Suprathermal Ionospheric Origin Fe+ in and Near Earth's Magnetosphere

Science.gov (United States)

Christon, S. P.; Hamilton, D. C.; Plane, J. M. C.; Mitchell, D. G.; Grebowsky, J. M.; Spjeldvik, W. N.; Nylund, S. R.

2017-11-01

Suprathermal (87-212 keV/e) singly charged iron, Fe+, has been discovered in and near Earth's 9-30 RE equatorial magnetosphere using 21 years of Geotail STICS (suprathermal ion composition spectrometer) data. Its detection is enhanced during higher geomagnetic and solar activity levels. Fe+, rare compared to dominant suprathermal solar wind and ionospheric origin heavy ions, might derive from one or all three candidate lower-energy sources: (a) ionospheric outflow of Fe+ escaped from ion layers near 100 km altitude, (b) charge exchange of nominal solar wind iron, Fe+≥7, in Earth's exosphere, or (c) inner source pickup Fe+ carried by the solar wind, likely formed by solar wind Fe interaction with near-Sun interplanetary dust particles. Earth's semipermanent ionospheric Fe+ layers derive from tons of interplanetary dust particles entering Earth's atmosphere daily, and Fe+ scattered from these layers is observed up to 1000 km altitude, likely escaping in strong ionospheric outflows. Using 26% of STICS's magnetosphere-dominated data when possible Fe+2 ions are not masked by other ions, we demonstrate that solar wind Fe charge exchange secondaries are not an obvious Fe+ source. Contemporaneous Earth flyby and cruise data from charge-energy-mass spectrometer on the Cassini spacecraft, a functionally identical instrument, show that inner source pickup Fe+ is likely not important at suprathermal energies. Consequently, we suggest that ionospheric Fe+ constitutes at least a significant portion of Earth's suprathermal Fe+, comparable to the situation at Saturn where suprathermal Fe+ is also likely of ionospheric origin.

On the propagation of hydromagnetic waves in a plasma of thermal and suprathermal components

Science.gov (United States)

Kumar, Nagendra; Sikka, Himanshu

2007-12-01

The propagation of MHD waves is studied when two ideal fluids, thermal and suprathermal gases, coupled by magnetic field are moving with the steady flow velocity. The fluids move independently in a direction perpendicular to the magnetic field but gets coupled along the field. Due to the presence of flow in suprathermal and thermal fluids there appears forward and backward waves. All the forward and backward modes propagate in such a way that their rate of change of phase speed with the thermal Mach number is same. It is also found that besides the usual hydromagnetic modes there appears a suprathermal mode which propagates with faster speed. Surface waves are also examined on an interface formed with composite plasma (suprathermal and thermal gases) on one side and the other is a non-magnetized plasma. In this case, the modes obtained are two or three depending on whether the sound velocity in thermal gas is equal to or greater than the sound velocity in suprathermal gas. The results lead to the conclusion that the interaction of thermal and suprathermal components may lead to the occurrence of an additional mode called suprathermal mode whose phase velocity is higher than all the other modes.

Suprathermal protons in the interplanetary solar wind

Science.gov (United States)

Goodrich, C. C.; Lazarus, A. J.

1976-01-01

Using the Mariner 5 solar wind plasma and magnetic field data, we present observations of field-aligned suprathermal proton velocity distributions having pronounced high-energy shoulders. These observations, similar to the interpenetrating stream observations of Feldman et al. (1974), are clear evidence that such proton distributions are interplanetary rather than bow shock associated phenomena. Large Alfven speed is found to be a requirement for the occurrence of suprathermal proton distribution; further, we find the proportion of particles in the shoulder to be limited by the magnitude of the Alfven speed. It is suggested that this last result could indicate that the proton thermal anisotropy is limited at times by wave-particle interactions

Electron density interferometry measurement in laser-matter interaction

International Nuclear Information System (INIS)

Popovics-Chenais, C.

1981-05-01

This work is concerned with the laser-interferometry measurement of the electronic density in the corona and the conduction zone external part. Particularly, it is aimed at showing up density gradients and at their space-time localization. The first chapter recalls the density profile influence on the absorption principal mechanisms and the laser energy transport. In chapter two, the numerical and analytical hydrodynamic models describing the density profile are analysed. The influence on the density profile of the ponderomotive force associated to high oscillating electric fields is studied, together with the limited thermal conduction and suprathermal electron population. The mechanism action, in our measurement conditions, is numerically simulated. Calculations are made with experimental parameters. The measurement interaction conditions, together with the diagnostic method by high resolution laser interferometry are detailed. The results are analysed with the help of numerical simulation which is the experiment modeling. An overview of the mechanisms shown up by interferometric measurements and their correlation with other diagnostics is the conclusion of this work [fr

Modelling of non-thermal electron cyclotron emission during ECRH

International Nuclear Information System (INIS)

Tribaldos, V.; Krivenski, V.

1990-01-01

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

Observations of thermal and suprathermal tail ions from WIND

Science.gov (United States)

Randol, B. M.; Christian, E. R.; Wilson, L. B., III

2016-12-01

The velocity distribution function (VDF) of solar wind protons (as well as other ion populations) is comprised of a thermal Maxwellian core and an accelerated suprathermal tail, beginning at around 1 keV in the frame co-moving with solar wind bulk velocity. The form of the suprathermal tail is a power law in phase space density, f, vs. speed, v, such that f / vγ, where γ is the power law index. This commonly observed index is of particular interest because no traditional theory predicts its existence. We need more data in order to test these theories. The general shape is of interest because it is kappa-like. We show combined observations from three different instruments on the WIND spacecraft: 3DP/PLSP, STICS, and 3DP/SST/Open. These data stretch from 102 to 107 eV in energy, encompassing both the thermal and suprathermal proton populations. We show further evidence for this kappa-like distribution and report on our progress on fitting of empirical functions to these data.

Calculation of Self-consistent Radial Electric Field in Presence of Convective Electron Transport in a Stellarator

International Nuclear Information System (INIS)

Kernbichler, W.; Heyn, M.F.; Kasilov, S.V.

2003-01-01

Convective transport of supra-thermal electrons can play a significant role in the energy balance of stellarators in case of high power electron cyclotron heating. Here, together with neoclassical thermal particle fluxes also the supra-thermal electron flux should be taken into account in the flux ambipolarity condition, which defines the self-consistent radial electric field. Since neoclassical particle fluxes are non-linear functions of the radial electric field, one needs an iterative procedure to solve the ambipolarity condition, where the supra-thermal electron flux has to be calculated for each iteration. A conventional Monte-Carlo method used earlier for evaluation of supra-thermal electron fluxes is rather slow for performing the iterations in reasonable computer time. In the present report, the Stochastic Mapping Technique (SMT), which is more effective than the conventional Monte Carlo method, is used instead. Here, the problem with a local monoenergetic supra-thermal particle source is considered and the effect of supra-thermal electron fluxes on both, the self-consistent radial electric field and the formation of different roots of the ambipolarity condition are studied

Charged particle measurements from a rocket-borne electron accelerator experiment

International Nuclear Information System (INIS)

Duprat, G.R.J.; McNamara, A.G.; Whalen, B.A.

1982-01-01

This chapter presents charged particle observations which relate to the spatial distribution of energetic (keV) charged particles surrounding the accelerator during gun firings, the energy distribution of energetic electrons produced in the plasma by the electron beam, and the dependence of these characteristics on the beam energy, current, and injection angle. The primary objective of the flight of the Nike Black Brant rocket (NUB-06) was to use an electron beam to probe the auroral field lines for electric fields parallel to the magnetic field. The secondary objectives were to study electron beam interactions in the ionosphere and spacecraft charging effects. It is demonstrated that during high current (greater than or equal to 10ma electron beam firings, an intense suprathermal as well as energetic electron population is created on flux tubes near the beam. Certain similarities exist between these measurements and corresponding ones made in the Houston vacuum tank suggesting that the same instability observed in the laboratory is occurring at high altitudes in the ionosphere

Electron distribution functions in Io plasma torus

International Nuclear Information System (INIS)

Boev, A.G.

2003-01-01

Electron distribution functions measured by the Voyager 1 in different shares of the Io plasma torus are explained. It is proved that their suprathermal tails are formed by the electrical field induced by the 'Jupiter wind'. The Maxwellian parts of all these spectra characterize thermal equilibrium populations of electrons and the radiation of exited ions

Suprathermal fusion reactions in laser-imploded D-T pellets. Applicability to pellet diagnosis and necessity of nuclear data

International Nuclear Information System (INIS)

Tabaru, Y.; Nakao, Y.; Kudo, K.; Nakashima, H.

1995-01-01

The suprathermal fusion reaction is examined on the basis of coupled transport/hydrodynamic calculation. We also calculate the energy spectrum of neutrons bursting from DT pellet. Because of suprathermal fusion and rapid pellet expansion, these neutrons contain fast components whose maximum energy reachs about 40 MeV. The pellet ρR diagnosis by the detection of suprathermal fusion neutrons is discussed. (author)

ON THE REMOTE DETECTION OF SUPRATHERMAL IONS IN THE SOLAR CORONA AND THEIR ROLE AS SEEDS FOR SOLAR ENERGETIC PARTICLE PRODUCTION

Energy Technology Data Exchange (ETDEWEB)

Laming, J. Martin; Moses, J. Daniel; Ko, Yuan-Kuen [Space Science Division, Naval Research Laboratory, Code 7684, Washington, DC 20375 (United States); Ng, Chee K. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Rakowski, Cara E.; Tylka, Allan J. [NASA/GSFC Code 672, Greenbelt, MD 20771 (United States)

2013-06-10

Forecasting large solar energetic particle (SEP) events associated with shocks driven by fast coronal mass ejections (CMEs) poses a major difficulty in the field of space weather. Besides issues associated with CME initiation, the SEP intensities are difficult to predict, spanning three orders of magnitude at any given CME speed. Many lines of indirect evidence point to the pre-existence of suprathermal seed particles for injection into the acceleration process as a key ingredient limiting the SEP intensity of a given event. This paper outlines the observational and theoretical basis for the inference that a suprathermal particle population is present prior to large SEP events, explores various scenarios for generating seed particles and their observational signatures, and explains how such suprathermals could be detected through measuring the wings of the H I Ly{alpha} line.

ON THE REMOTE DETECTION OF SUPRATHERMAL IONS IN THE SOLAR CORONA AND THEIR ROLE AS SEEDS FOR SOLAR ENERGETIC PARTICLE PRODUCTION

International Nuclear Information System (INIS)

Laming, J. Martin; Moses, J. Daniel; Ko, Yuan-Kuen; Ng, Chee K.; Rakowski, Cara E.; Tylka, Allan J.

2013-01-01

Forecasting large solar energetic particle (SEP) events associated with shocks driven by fast coronal mass ejections (CMEs) poses a major difficulty in the field of space weather. Besides issues associated with CME initiation, the SEP intensities are difficult to predict, spanning three orders of magnitude at any given CME speed. Many lines of indirect evidence point to the pre-existence of suprathermal seed particles for injection into the acceleration process as a key ingredient limiting the SEP intensity of a given event. This paper outlines the observational and theoretical basis for the inference that a suprathermal particle population is present prior to large SEP events, explores various scenarios for generating seed particles and their observational signatures, and explains how such suprathermals could be detected through measuring the wings of the H I Lyα line.

CINEMA (Cubesat for Ion, Neutral, Electron, MAgnetic fields)

Science.gov (United States)

Lin, R. P.; Parks, G. K.; Halekas, J. S.; Larson, D. E.; Eastwood, J. P.; Wang, L.; Sample, J. G.; Horbury, T. S.; Roelof, E. C.; Lee, D.; Seon, J.; Hines, J.; Vo, H.; Tindall, C.; Ho, J.; Lee, J.; Kim, K.

2009-12-01

The NSF-funded CINEMA mission will provide cutting-edge magnetospheric science and critical space weather measurements, including high sensitivity mapping and high cadence movies of ring current, >4 keV Energetic Neutral Atom (ENA), as well as in situ measurements of suprathermal electrons (>~2 keV) and ions (>~ 4 keV) in the auroral and ring current precipitation regions, all with ~1 keV FWHM resolution and uniform response up to ~100 keV. A Suprathermal Electron, Ion, Neutral (STEIN) instrument adds an electrostatic deflection system to the STEREO STE (SupraThermal Electron) 4-pixel silicon semiconductor sensor to separate ions from electrons and from ENAs up to ~20 keV. In addition, inboard and outboard (on an extendable 1m boom) magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. A new attitude control system (ACS) uses torque coils, a solar aspect sensor and the magnetometers to de-tumble the 3u CINEMA spacecraft, then spin it up to ~1 rpm with the spin axis perpendicular to the ecliptic, so STEIN can sweep across most of the sky every minute. Ideally, CINEMA will be placed into a high inclination low earth orbit that crosses the auroral zone and cusp. An S-band transmitter will be used to provide > ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station. Two more identical CINEMA spacecraft will be built by Kyung Hee University (KHU) in Korea under their World Class University (WCU) program, to provide stereo ENA imaging and multi-point in situ measurements. Furthermore, CINEMA’s development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft will be important for future nanosatellite space missions.

A kinetic study of solar wind electrons

International Nuclear Information System (INIS)

Lie-Svendsen, Oeystein; Leer, Egil

1996-01-01

The evolution of the distribution function for a test population of electrons in an isothermal electron-proton corona has been studied using a Fokker-Planck description. The aim is to investigate whether a suprathermal tail forms due to the energy dependence of the Coulomb cross section. We find that a Maxwellian test population, injected into this background close to the coronal base with a temperature equal to that of the background electrons, maintains its shape throughout the transition from collision-dominated to collisionless flow. No significant suprathermal tail in the electron distribution function is seen in the outer corona

Slowly moving test charge in two-electron component non-Maxwellian plasma

International Nuclear Information System (INIS)

Ali, S.; Eliasson, B.

2015-01-01

Potential distributions around a slowly moving test charge are calculated by taking into account the electron-acoustic waves in an unmagnetized plasma. Considering a neutralizing background of static positive ions, the supra-thermal hot and cold electrons are described by the Vlasov equations to account for the Kappa (power-law in velocity space) and Maxwell equilibrium distributions. Fourier analysis further leads to the derivation of electrostatic potential showing the impact of supra-thermal hot electrons. The test charge moves slowly in comparison with the hot and cold electron thermal speeds and is therefore shielded by the electrons. This gives rise to a short-range Debye-Hückel potential decaying exponentially with distance and to a far field potential decaying as inverse third power of the distance from the test charge. The results are relevant for both laboratory and space plasmas, where supra-thermal hot electrons with power-law distributions have been observed

Finite grid radius and thickness effects on retarding potential analyzer measured suprathermal electron density and temperature

International Nuclear Information System (INIS)

Knudsen, W.C.

1992-01-01

The effect of finite grid radius and thickness on the electron current measured by planar retarding potential analyzers (RPAs) is analyzed numerically. Depending on the plasma environment, the current is significantly reduced below that which is calculated using a theoretical equation derived for an idealized RPA having grids with infinite radius and vanishingly small thickness. A correction factor to the idealized theoretical equation is derived for the Pioneer Venus (PV) orbiter RPA (ORPA) for electron gases consisting of one or more components obeying Maxwell statistics. The error in density and temperature of Maxwellian electron distributions previously derived from ORPA data using the theoretical expression for the idealized ORPA is evaluated by comparing the densities and temperatures derived from a sample of PV ORPA data using the theoretical expression with and without the correction factor

Solar wind ∼0.1-1.5 keV electrons at quiet times

Energy Technology Data Exchange (ETDEWEB)

Tao, Jiawei; Wang, Linghua, E-mail: wanglhwang@gmail.com; Zong, Qiugang; He, Jiansen; Tu, Chuanyi [School of Earth and Space Science, Peking University, Beijing 100871 (China); Li, Gang [Department of Physics and CSPAR, University of Alabama in Huntsville, Alabama 35899 (United States); Salem, Chadi S.; Bale, Stuart D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Wimmer-Schweingruber, Robert F. [Institute for Experimental and Applied Physics, University of Kiel (Germany)

2016-03-25

We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1-1.5 keV) electrons measured by the WIND 3-D Plasma & Energetic Particle (3DP) instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. Firstly, we separate strahl (beaming) electrons and halo (isotropic) electrons based on their features in pitch angle distributions. Secondly, we fit the observed energy spectrum of both the strahl and halo electrons at ∼0.1-1.5 keV to a Kappa distribution function with an index κ, effective temperature T{sub eff} and density n{sub 0}. We also integrate the the measurements over ∼0.1-1.5 keV to obtain the average electron energy E{sub avg} of the strahl and halo. We find a strong positive correlation between κ and T{sub eff} for both the strahl and halo, possibly reflecting the nature of the generation of these suprathermal electrons. Among the 245 selected samples, ∼68% have the halo κ smaller than the strahl κ, while ∼50% have the halo E{sub h} larger than the strahl E{sub s}.

Correcting PSP electron measurements for the effects of spacecraft electrostatic and magnetic fields

Science.gov (United States)

McGinnis, D.; Halekas, J. S.; Larson, D. E.; Whittlesey, P. L.; Kasper, J. C.

2017-12-01

The near-Sun environment which the Parker Solar Probe will investigate presents a unique challenge for the measurement of thermal and suprathermal electrons. Over one orbital period, the ionizing photon flux and charged particle densities vary to such an extent that the spacecraft could charge to electrostatic potentials ranging from a few volts to tens of volts or more, and it may even develop negative electrostatic potentials near closest approach. In addition, significant permanent magnetic fields from spacecraft components will perturb thermal electron trajectories. Given these effects, electron distribution function (EDF) measurements made by the SWEAP/SPAN electron sensors will be significantly affected. It is thus important to try to understand the extent and nature of such effects, and to remediate them as much as possible. To this end, we have incorporated magnetic fields and a model electrostatic potential field into particle tracing simulations to predict particle trajectories through the near spacecraft environment. These simulations allow us to estimate how the solid angle elements measured by SPAN deflect and stretch in the presence of these fields and therefore how and to what extent EDF measurements will be distorted. In this work, we demonstrate how this technique can be used to produce a `dewarping' correction factor. Further, we show that this factor can correct synthetic datasets simulating the warped EDFs that the SPAN instruments are likely to measure over a wide range of spacecraft potentials and plasma Debye lengths.

Electron heat conduction and suprathermal particles

International Nuclear Information System (INIS)

Bakunin, O.G.; Krasheninnikov, S.I.

1991-01-01

As recognized at present, the applicability of Spitzer-Harm's theory on electron heat conduction along the magnetic field is limited by comparatively small values of the thermal electron mean free path ratio, λ to the characteristic length of changes in plasma parameters, L: γ=λ/L≤10 -2 . The stationary kinetic equation for the electron distribution function inhomogeneous along the x-axis f e (v,x) allows one to have solutions in the self-similar variables. The objective of a given study is to generalize the solutions for the case of arbitrary Z eff , that will allow one to compare approximate solutions to the kinetic equation with the precise ones in a wide range of parameters. (author) 8 refs., 2 figs

Energy of auroral electrons and Z mode generation

Science.gov (United States)

Krauss-Varban, D.; Wong, H. K.

1990-01-01

The present consideration of Z-mode radiation generation, in light of observational results indicating that the O mode and second-harmonic X-mode emissions can prevail over the X-mode fundamental radiation when suprathermal electron energy is low, gives attention to whether the thermal effect on the Z-mode dispersion can be equally important, and whether the Z-mode can compete for the available free-energy source. It is found that, under suitable circumstances, the growth rate of the Z-mode can be substantial even for low suprathermal auroral electron energies. Growth is generally maximized for propagation perpendicular to the magnetic field.

Effect of ion suprathermality on arbitrary amplitude dust acoustic waves in a charge varying dusty plasma

International Nuclear Information System (INIS)

Tribeche, Mouloud; Mayout, Saliha; Amour, Rabia

2009-01-01

Arbitrary amplitude dust acoustic waves in a high energy-tail ion distribution are investigated. The effects of charge variation and ion suprathermality on the large amplitude dust acoustic (DA) soliton are then considered. The correct suprathermal ion charging current is rederived based on the orbit motion limited approach. In the adiabatic case, the variable dust charge is expressed in terms of the Lambert function and we take advantage of this transcendental function to show the existence of rarefactive variable charge DA solitons involving cusped density humps. The dust charge variation leads to an additional enlargement of the DA soliton, which is less pronounced as the ions evolve far away from Maxwell-Boltzmann distribution. In the nonadiabatic case, the dust charge fluctuation may provide an alternate physical mechanism causing anomalous dissipation the strength of which becomes important and may prevail over that of dispersion as the ion spectral index κ increases. Our results may provide an explanation for the strong spiky waveforms observed in auroral electric field measurements by Ergun et al.[Geophys. Res. Lett. 25, 2025 (1998)].

A physical mechanism producing suprathermal populations and initiating substorms in the Earth's magnetotail

Directory of Open Access Journals (Sweden)

D. V. Sarafopoulos

2008-06-01

Full Text Available We suggest a candidate physical mechanism, combining there dimensional structure and temporal development, which is potentially able to produce suprathermal populations and cross-tail current disruptions in the Earth's plasma sheet. At the core of the proposed process is the "akis" structure; in a thin current sheet (TCS the stretched (tail-like magnetic field lines locally terminate into a sharp tip around the tail midplane. At this sharp tip of the TCS, ions become non-adiabatic, while a percentage of electrons are accumulated and trapped: The strong and transient electrostatic electric fields established along the magnetic field lines produce suprathermal populations. In parallel, the tip structure is associated with field aligned and mutually attracted parallel filamentary currents which progressively become more intense and inevitably the structure collapses, and so does the local TCS. The mechanism is observationally based on elementary, almost autonomous and spatiotemporal entities that correspond each to a local thinning/dipolarization pair having duration of ~1 min. Energetic proton and electron populations do not occur simultaneously, and we infer that they are separately accelerated at local thinnings and dipolarizations, respectively. In one example energetic particles are accelerated without any dB/dt variation and before the substorm expansion phase onset. A particular effort is undertaken demonstrating that the proposed acceleration mechanism may explain the plasma sheet ratio Ti/Te≈7. All our inferences are checked by the highest resolution datasets obtained by the Geotail Energetic Particles and Ion Composition (EPIC instrument. The energetic particles are used as the best diagnostics for the accelerating source. Near Earth (X≈10 RE selected events support our basic concept. The proposed mechanism seems to reveal a fundamental building block of the substorm phenomenon and may be the basic process/structure, which is now

Self-consistent electron transport in collisional plasmas

International Nuclear Information System (INIS)

Mason, R.J.

1982-01-01

A self-consistent scheme has been developed to model electron transport in evolving plasmas of arbitrary classical collisionality. The electrons and ions are treated as either multiple donor-cell fluids, or collisional particles-in-cell. Particle suprathermal electrons scatter off ions, and drag against fluid background thermal electrons. The background electrons undergo ion friction, thermal coupling, and bremsstrahlung. The components move in self-consistent advanced E-fields, obtained by the Implicit Moment Method, which permits Δt >> ω/sub p/ -1 and Δx >> lambda/sub D/ - offering a 10 2 - 10 3 -fold speed-up over older explicit techniques. The fluid description for the background plasma components permits the modeling of transport in systems spanning more than a 10 7 -fold change in density, and encompassing contiguous collisional and collisionless regions. Results are presented from application of the scheme to the modeling of CO 2 laser-generated suprathermal electron transport in expanding thin foils, and in multi-foil target configurations

Proceedings of eighth joint workshop on electron cyclotron emission and electron cyclotron resonance heating. Vol. 1

International Nuclear Information System (INIS)

1993-03-01

The theory of electron cyclotron resonance phenomena is highly developed. The main theoretical tools are well established, generally accepted and able to give a satisfactory description of the main results obtained in electron cyclotron emission, absorption and current drive experiments. In this workshop some advanced theoretical and numerical tools have been presented (e.g., 3-D Fokker-Planck codes, treatment of the r.f. beam as a whole, description of non-linear and finite-beam effects) together with the proposal for new scenarios for ECE and ECA measurements (e.g., for diagnosing suprathermal populations and their radial transport). (orig.)

Proceedings of eighth joint workshop on electron cyclotron emission and electron cyclotron resonance heating. Vol. 2

International Nuclear Information System (INIS)

1993-03-01

The theory of electron cyclotron resonance phenomena is highly developed. The main theoretical tools are well established, generally accepted and able to give a satisfactory description of the main results obtained in electron cyclotron emission, absorption and current drive experiments. In this workshop some advanced theoretical and numerical tools have been presented (e.g., 3-D Fokker-Planck codes, treatment of the r.f. beam as a whole, description of non-linear and finite-beam effects) together with the proposal for new scenarios for ECE and ECA measurements (e.g., for diagnosing suprathermal populations and their radial transport). (orig.)

Suprathermal-electron generation, transport, and deposition in CO2-laser-irradiated targets

International Nuclear Information System (INIS)

Hauer, A.; Goldman, R.; Kristal, R.

1982-01-01

Experiments on both axial and lateral energy transport and deposition in spherical targets are described. A variety of diagnostics have been used to measure hot-electron transport and deposition including bremsstrahlung and inner-shell radiation and soft x-ray temperature measurements. Self-generated electric and magnetic fields play an important role in the transport and deposition of the hot electrons. In some cases distinct patterns of surface deposition consistent with magnetic-field configurations have been observed

Electron thermal conduction in LASNEX

International Nuclear Information System (INIS)

Munro, D.; Weber, S.

1994-01-01

This report is a transcription of hand-written notes by DM dated 29 January 1986, transcribed by SW, with some clarifying comments added and details specific to running the LASNEX code deleted. Reference to the esoteric measurement units employed in LASNEX has also been deleted by SW (hopefully, without introducing errors in the numerical constants). The report describes the physics equations only, and only of electron conduction. That is, it does not describe the numerical method, which may be finite difference or finite element treatment in space, and (usually) implicit treatment in time. It does not touch on other electron transport packages which are available, and which include suprathermal electrons, nonlocal conduction, Krook model conduction, and modifications to electron conduction by magnetic fields. Nevertheless, this model is employed for the preponderance of LASNEX simulations

Studies of suprathermal electron loss in the magnetic ripple of Tore Supra

International Nuclear Information System (INIS)

Basiuk, V.; Lipa, M.; Martin, G.; Chantant, M.; Guilhem, D.; Imbeaux, F.; Mitteau, R.; Peysson, Y.; Surle, F.

2000-01-01

A new prototype of protection against fast electron trapped in the magnetic ripple was installed on Tore-Supra in 1998. It was designed to support the high flux of fast electron generated by lower hybrid in the CIEL project (up to 6 MW/m 2 ) during steady state experiments. So it is actively cooled and allows a direct measurement of the energy lost in the ripple. (author)

ANTHEM: a two-dimensional multicomponent self-consistent hydro-electron transport code for laser-matter interaction studies

International Nuclear Information System (INIS)

Mason, R.J.

1982-01-01

The ANTHEM code for the study of CO 2 -laser-generated transport is outlined. ANTHEM treats the background plasma as coupled Eulerian thermal and ion fluids, and the suprathermal electrons as either a third fluid or a body of evolving collisional PIC particles. The electrons scatter off the ions; the suprathermals drag against the thermal background. Self-consistent E- and B-fields are computed by the Implicit Moment Method. The current status of the code is described. Typical output from ANTHEM is discussed with special application to Augmented-Return-Current CO 2 -laser-driven targets

Ripple enhanced transport of suprathermal alpha particles

International Nuclear Information System (INIS)

Tani, K.; Takizuka, T.; Azumi, M.

1986-01-01

The ripple enhanced transport of suprathermal alpha particles has been studied by the newly developed Monte-Carlo code in which the motion of banana orbit in a toroidal field ripple is described by a mapping method. The existence of ripple-resonance diffusion has been confirmed numerically. We have developed another new code in which the radial displacement of banana orbit is given by the diffusion coefficients from the mapping code or the orbit following Monte-Carlo code. The ripple loss of α particles during slowing down has been estimated by the mapping model code as well as the diffusion model code. From the comparison of the results with those from the orbit-following Monte-Carlo code, it has been found that all of them agree very well. (author)

Application of the model of the relativistic anti-loss-cone distribution to ECE spectrum in discharge applying LH wave

International Nuclear Information System (INIS)

Sato, Masayasu; Yokomizo, Hideaki

1987-11-01

The electron cyclotron emission (ECE) is dominated from supra-thermal electron in discharge applying LH wave. We obtain informations of supra-thermal electron by applying the model of the relativistic anti-loss-cone distribution to ECE spectrum in the discharge. In this model, the emission perpendicular to the magnetic field are considered. The frequency range is considered to be well above the plasma and electron cyclotron frequencies, thus collective effects can be neglected. The electron distribution is assumed to be anisotropic in the velocity space and strongly extended in the direction parallel to the magnetic field, namely the relativistic anti-loss-cone distribution. The informations of supra-thermal electron are obtained by the following way. The temperature and density of the supra-thermal electron and the anti-loss-cone angle are obtained from the power spectrum of LH wave launched, the measured slope of the spectrum of ECE and the spectral radiance of ECE. (author)

The study of dynamics of electrons in the presence of large current densities; Etude de la dynamique des electrons en presence de fortes densites de courant

Energy Technology Data Exchange (ETDEWEB)

Garcia, G

2007-11-15

The runaway electron effect is considered in different fields: nuclear fusion, or the heating of the solar corona. In this thesis, we are interested in runaway electrons in the ionosphere. We consider the issue of electrons moving through an ionospheric gas of positive ions and neutrals under the influence of a parallel electric field. We develop a kinetic model of collisions including electrons/electrons, electrons/ions and electrons/neutrals collisions. We use a Fokker-Planck approach to describe binary collisions between charged particles with a long-range interaction. A computational example is given illustrating the approach to equilibrium and the impact of the different terms. Then, a static electric field is applied in a new sample run. In this run, the electrons move in the z direction, parallel to the electric field. The first results show that all the electron distribution functions are non-Maxwellian. Furthermore, runaway electrons can carry a significant part of the total current density up to 20% of the total current density. Nevertheless, we note that the divergence free of the current density is not conserved. We introduce major changes in order to take into account the variation of the different moments of the ion distribution functions. We observe that the electron distribution functions are still non-Maxwellian. Runaway electrons are created and carry the current density. The core distribution stay at rest. As these electrons undergo less collisions, they increase the plasma conductivity. We make a parametric study. We fit the electron distribution function by two Maxwellian. We show that the time to reach the maximal current density is a key point. Thus, when we increase this time, we modify the temperatures. The current density plays a primary role. When the current density increases, all the moments of the distributions increase: electron density and mean velocity of the suprathermal distribution and the electron temperature of the core and

Heated electron distributions from resonant absorption

International Nuclear Information System (INIS)

DeGroot, J.S.; Tull, J.E.

1975-01-01

A simplified model of resonant absorption of obliquely incident laser light has been developed. Using a 1.5 dimensional electrostatic simulation computer code, it is shown that the inclusion of ion motion is critically important in determining the heated electron distributions from resonant absorption. The electromagnetic wave drives up an electron plasma wave. For long density scale lengths (Lapprox. =10 3 lambda/subD//sube/), the phase velocity of this wave is very large (ω/kapproximately-greater-than10V/sub th/) so that if heating does occur, a suprathermal tail of very energetic electrons is produced. However, the pressure due to this wave steepens the density profile until the density gradient scale length near the critical density (where the local plasma frequency equals the laser frequency) is of order 20lambda/subD//sube/. The electrostatic wave is thus forced to have a much lower phase velocity (ω/kapprox. =2.5V/sub th/). In this case, more electrons are heated to much lower velocities. The heated electron distributions are exponential in velocity space. Using a simple theory it is shown that this property of profile steepening applies to most of a typical laser fusion pulse. This steepening raises the threshold for parametric instabilities near the critical surface. Thus, the extensive suprathermal electron distributions typically produced by these parametric instabilities can be drastically reduced

3rd harmonic electron cyclotron resonant heating absorption enhancement by 2nd harmonic heating at the same frequency in a tokamak

International Nuclear Information System (INIS)

Gnesin, S; Coda, S; Goodman, T P; Decker, J; Peysson, Y; Mazon, D

2012-01-01

The fundamental mechanisms responsible for the interplay and synergy between the absorption dynamics of extraordinary-mode electron cyclotron waves at two different harmonic resonances (the 2nd and 3rd) are investigated in the TCV tokamak. An enhanced 3rd harmonic absorption in the presence of suprathermal electrons generated by 2nd harmonic heating is predicted by Fokker–Planck simulations, subject to complex alignment requirements in both physical space and momentum space. The experimental signature for the 2nd/3rd harmonic synergy is sought through the suprathermal bremsstrahlung emission in the hard x-ray range of photon energy. Using a synthetic diagnostic, the emission variation due to synergy is calculated as a function of the injected power and of the radial transport of suprathermal electrons. It is concluded that in the present experimental setup a synergy signature has not been unambiguously detected. The detectability of the synergy is then discussed with respect to variations and uncertainties in the plasma density and effective charge in view of future optimized experiments. (paper)

Winter nightime ion temperatures and energetic electrons from 0go 6 plasma measurements

International Nuclear Information System (INIS)

Sanatani, S.; Breig, E.L.

1981-01-01

This paper presents and discusses ion temperature and suprathermal electron flux data acquired with the retarding potential analyzer on board the ogo 6 satellite when it was in solar eclipse. Attention is directed to measurements in the 400- to 800-km height interval between midnight and predawn in the northern winter nonpolar ionosphere. Statistical analysis of data recorded during a 1-month time span permits a decoupling of horizontal and altitude effects. A distinct longitudinal variation is observed for ion temperature above 500 km, with a significant relative enhancement over the western North Altantic Altitude distributions of ion temperature are compatible with Millstone Hill profiles within the common region of this enhancement. Large fluxes of energetic electrons are observed and extend to mush lower geomagnetic latitudes in the same longitude sector. Both a direct correlation in magnitude and a strong similarity in spatial extent are demonstrated for these ion temperature and electron flux data. The location of the limiting low-altitude boundary for observation of the electron fluxes is variable, dependent on local time and season as well as longitude. Variations in this boundary are found to be consistent with a calculated conjugate solar zenith angle of 99 0 +- 2 0 describing photoproduction of energetic electrons in the southern hemisphere. The ogo 6 data are considered to be indicative of an energy source originating in the sunlit summer hemisphere and providing heat via transport of photoelectrons to a broad but preferential segment of the winter nighttime mid-latitude ionosphere. Ions at other longitudes are without access to this energy source and cool to near the neutral temperature at heights to above 800 km inthe predawn hours

The study of dynamics of electrons in the presence of large current densities

International Nuclear Information System (INIS)

Garcia, G.

2007-11-01

The runaway electron effect is considered in different fields: nuclear fusion, or the heating of the solar corona. In this thesis, we are interested in runaway electrons in the ionosphere. We consider the issue of electrons moving through an ionospheric gas of positive ions and neutrals under the influence of a parallel electric field. We develop a kinetic model of collisions including electrons/electrons, electrons/ions and electrons/neutrals collisions. We use a Fokker-Planck approach to describe binary collisions between charged particles with a long-range interaction. A computational example is given illustrating the approach to equilibrium and the impact of the different terms. Then, a static electric field is applied in a new sample run. In this run, the electrons move in the z direction, parallel to the electric field. The first results show that all the electron distribution functions are non-Maxwellian. Furthermore, runaway electrons can carry a significant part of the total current density up to 20% of the total current density. Nevertheless, we note that the divergence free of the current density is not conserved. We introduce major changes in order to take into account the variation of the different moments of the ion distribution functions. We observe that the electron distribution functions are still non-Maxwellian. Runaway electrons are created and carry the current density. The core distribution stay at rest. As these electrons undergo less collisions, they increase the plasma conductivity. We make a parametric study. We fit the electron distribution function by two Maxwellian. We show that the time to reach the maximal current density is a key point. Thus, when we increase this time, we modify the temperatures. The current density plays a primary role. When the current density increases, all the moments of the distributions increase: electron density and mean velocity of the suprathermal distribution and the electron temperature of the core and

Laboratory Measurements of Electrostatic Solitary Structures Generated by Beam Injection

International Nuclear Information System (INIS)

Lefebvre, Bertrand; Chen, Li-Jen; Gekelman, Walter; Pribyl, Patrick; Vincena, Stephen; Kintner, Paul; Pickett, Jolene; Chiang, Franklin; Judy, Jack

2010-01-01

Electrostatic solitary structures are generated by injection of a suprathermal electron beam parallel to the magnetic field in a laboratory plasma. Electric microprobes with tips smaller than the Debye length (λ De ) enabled the measurement of positive potential pulses with half-widths 4 to 25λ De and velocities 1 to 3 times the background electron thermal speed. Nonlinear wave packets of similar velocities and scales are also observed, indicating that the two descend from the same mode which is consistent with the electrostatic whistler mode and result from an instability likely to be driven by field-aligned currents.

TRIO (Triplet Ionospheric Observatory) Mission

Science.gov (United States)

Lee, D.; Seon, J.; Jin, H.; Kim, K.; Lee, J.; Jang, M.; Pak, S.; Kim, K.; Lin, R. P.; Parks, G. K.; Halekas, J. S.; Larson, D. E.; Eastwood, J. P.; Roelof, E. C.; Horbury, T. S.

2009-12-01

Triplets of identical cubesats will be built to carry out the following scientific objectives: i) multi-observations of ionospheric ENA (Energetic Neutral Atom) imaging, ii) ionospheric signature of suprathermal electrons and ions associated with auroral acceleration as well as electron microbursts, and iii) complementary measurements of magnetic fields for particle data. Each satellite, a cubesat for ion, neutral, electron, and magnetic fields (CINEMA), is equipped with a suprathermal electron, ion, neutral (STEIN) instrument and a 3-axis magnetometer of magnetoresistive sensors. TRIO is developed by three institutes: i) two CINEMA by Kyung Hee University (KHU) under the WCU program, ii) one CINEMA by UC Berkeley under the NSF support, and iii) three magnetometers by Imperial College, respectively. Multi-spacecraft observations in the STEIN instruments will provide i) stereo ENA imaging with a wide angle in local times, which are sensitive to the evolution of ring current phase space distributions, ii) suprathermal electron measurements with narrow spacings, which reveal the differential signature of accelerated electrons driven by Alfven waves and/or double layer formation in the ionosphere between the acceleration region and the aurora, and iii) suprathermal ion precipitation when the storm-time ring current appears. In addition, multi-spacecraft magnetic field measurements in low earth orbits will allow the tracking of the phase fronts of ULF waves, FTEs, and quasi-periodic reconnection events between ground-based magnetometer data and upstream satellite data.

Opacity broadening and interpretation of suprathermal CO linewidths: Macroscopic turbulence and tangled molecular clouds

Science.gov (United States)

Hacar, A.; Alves, J.; Burkert, A.; Goldsmith, P.

2016-06-01

Context. Since their first detection in the interestellar medium, (sub-)millimeter line observations of different CO isotopic variants have routinely been employed to characterize the kinematic properties of the gas in molecular clouds. Many of these lines exhibit broad linewidths that greatly exceed the thermal broadening expected for the low temperatures found within these objects. These observed suprathermal CO linewidths are assumed to originate from unresolved supersonic motions inside clouds. Aims: The lowest rotational J transitions of some of the most abundant CO isotopologues, 12CO and 13CO, are found to present large optical depths. In addition to well-known line saturation effects, these large opacities present a non-negligible contribution to their observed linewidths. Typically overlooked in the literature, in this paper we aim to quantify the impact of these opacity broadening effects on the current interpretation of the CO suprathermal line profiles. Methods: Combining large-scale observations and LTE modeling of the ground J = 1-0 transitions of the main 12CO, 13CO, C18O isotopologues, we have investigated the correlation of the observed linewidths as a function of the line opacity in different regions of the Taurus molecular cloud. Results: Without any additional contributions to the gas velocity field, a large fraction of the apparently supersonic (ℳ ~ 2-3) linewidths measured in both 12CO and 13CO (J = 1-0) lines can be explained by the saturation of their corresponding sonic-like, optically thin C18O counterparts assuming standard isotopic fractionation. Combined with the presence of multiple components detected in some of our C18O spectra, these opacity effects also seem to be responsible for most of the highly supersonic linewidths (ℳ > 8-10) detected in some of the broadest 12CO and 13CO spectra in Taurus. Conclusions: Our results demonstrate that most of the suprathermal 12CO and 13CO linewidths reported in nearby clouds like Taurus

Interaction of supra-thermal ions with turbulence in a magnetized toroidal plasma

International Nuclear Information System (INIS)

Plyushchev, G.

2009-01-01

This thesis addresses the interaction of a supra-thermal ion beam with turbulence in the simple magnetized toroidal plasma of TORPEX. The first part of the Thesis deals with the ohmic assisted discharges on TORPEX. The aim of these discharges is the investigation of the open to closed magnetic field line transition. The relevant magnetic diagnostics were developed. Ohmic assisted discharges with a maximum plasma current up to 1 kA are routinely obtained. The equilibrium conditions on the vacuum magnetic field configuration were investigated. In the second part of the Thesis, the design of the fast ion source and detector are discussed. The accelerating electric field needed for the fast ion source was optimized. The fast ion source was constructed and commissioned. To detect the fast ions a specially designed gridded energy analyzer was used. The electron energy distribution function was obtained to demonstrate the efficiency of the detector. The experiments with the fast ion beam were conducted in different plasma regions of TORPEX. In the third part of the Thesis, numerical simulations are used to interpret the measured fast ion beam behavior. It is shown that a simple single particle equation of motion explains the beam behavior in the experiments in the absence of plasma. To explain the fast ion beam experiments with the plasma a turbulent electric field must be used. The model that takes into account this turbulent electrical field qualitatively explains the shape of the fast ion current density profile in the different plasma regions of TORPEX. The vertically elongated fast ion current density profiles are explained by a spread in the fast ion velocity distribution. The theoretically predicted radial fast ion beam spreading due to the turbulent electric field was observed in the experiment. (author)

The « 3-D donut » electrostatic analyzer for millisecond timescale electron measurements in the solar wind

Science.gov (United States)

Berthomier, M.; Techer, J. D.

2017-12-01

Understanding electron acceleration mechanisms in planetary magnetospheres or energy dissipation at electron scale in the solar wind requires fast measurement of electron distribution functions on a millisecond time scale. Still, since the beginning of space age, the instantaneous field of view of plasma spectrometers is limited to a few degrees around their viewing plane. In Earth's magnetosphere, the NASA MMS spacecraft use 8 state-of-the-art sensor heads to reach a time resolution of 30 milliseconds. This costly strategy in terms of mass and power consumption can hardly be extended to the next generation of constellation missions that would use a large number of small-satellites. In the solar wind, using the same sensor heads, the ESA THOR mission is expected to reach the 5ms timescale in the thermal energy range, up to 100eV. We present the « 3-D donut » electrostatic analyzer concept that can change the game for future space missions because of its instantaneous hemispheric field of view. A set of 2 sensors is sufficient to cover all directions over a wide range of energy, e.g. up to 1-2keV in the solar wind, which covers both thermal and supra-thermal particles. In addition, its high sensitivity compared to state of the art instruments opens the possibility of millisecond time scale measurements in space plasmas. With CNES support, we developed a high fidelity prototype (a quarter of the full « 3-D donut » analyzer) that includes all electronic sub-systems. The prototype weights less than a kilogram. The key building block of the instrument is an imaging detector that uses EASIC, a low-power front-end electronics that will fly on the ESA Solar Orbiter and on the NASA Parker Solar Probe missions.

Studies of suprathermal emission due to cyclotron-electronic heating of the tokamak TCV plasma

International Nuclear Information System (INIS)

Blanchard, P.

2002-07-01

Photo sensitization of wide band gap semiconductors is used in a wide range of application like silver halide photography and xerography. The development of a new type of solar cells, based on the sensitization of meso porous metal oxide films by panchromatic dyes, has triggered a lot of fundamental research on electron transfer dynamics. Upon excitation, the sensitizer transfers an electron in the conduction band of the semiconductor. Recombination of the charge separated state is prevented by the fast regeneration of the dye by an electron donor present in solution. Until recently, most of the work in this area has been focused on the competition between the recombination and the regeneration processes, which take place in the nanosecond to millisecond regime. With the development of solid-state femtosecond laser, the measurement of the dynamics of the first electron transfer step occurring in the solar cell has become possible . Electron injection from ruthenium(Il) poly pyridyl complexes into titanium dioxide has been found to occur with a poly exponential rate, with time constants ranging from 10 ps. In spite of the lately acquired capacity to measure the dynamics of these reactions, the physical meaning of this poly exponential kinetics and the factors that can influence this process are still poorly understood. In this work, the development of a new femtosecond pump-probe spectrometer, intended to monitor the ultrafast dynamics of electron injection, is presented. The study of this process requires an excellent temporal resolution and a large wavelength tunability to be able to excite a great variety of dyes and to probe the different products of the reaction. These specifications were met using the latest progress made in optical parametric amplification, which allowed the construction of a versatile experimental set-up. The interfacing by computer of the different devices used during the experiments increase the ease of use of the set-up. Transient

Profile measurements of localized fast electrons and ions in TORE SUPRA

International Nuclear Information System (INIS)

Basiuk, V.; Roubin, J.P.; Becoulet, A.; Carrasco, J.; Martin, G.; Moreau, D.; Saoutic, B.

1992-01-01

The strong toroidal and poloidal anisotropy of the heat flux to the first wall of Tore Supra during additional heating has been related to suprathermal particle losses induced by the TF ripple. In this paper we describe a new system of electric collectors designed to diagnose these localized particles and we analyse measurements performed during LHCD, ICRH and NBI heating. The interaction of fast particles created by additional heating with the TF ripple perturbation in Tore Supra has been analyzed by a direct measurement of the localized particles. The good confinement region has been identified thanks to a peak in the measured current profiles and is in agreement with theory. During LHCD and ICRH, the global losses are weak but strongly anisotropic leading to hot spots at the wall. During ICRH, an ejection of fast ions by the sawteeth towards peripheral zones where they get lost in the ripple has been seen. This is a possible scenario of α particle losses in a reactor

Characterization of LH induced current carrying fast electrons in JET

Energy Technology Data Exchange (ETDEWEB)

Ramponi, G.; Airoldi, A. [Consiglio Nazionale delle Ricerche, Milan (Italy). Lab. di Fisica del Plasma; Bartlett, D.; Brusati, M.; Froissard, P.; Gormezano, C.; Rimini, F.; Silva, R.P. da; Tanzi, C.P. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

1992-12-31

Lower Hybrid Current Drive (LHCD) experiments have recently been made at JET by coupling up to 2.4 MW of RF power at 3.7 GHz, with a power spectrum centered at n{sub ||} = 1.8 {+-} 0.2 corresponding to a resonating electron energy of about 100 keV via Electron Landau Damping. The Current Drive (CD) efficiency has been observed to increase when LH and ICRH power are applied simultaneously to the plasma, suggesting that a part of the fast magnetosonic wave is absorbed on the LH-generated fast electrons. An important problem of CD experiments in tokamaks is the determination of the radial distribution of the driven current and the characterization in the momentum space of the current carrying fast electrons by using appropriate diagnostic tools. For this purpose, a combined analysis of the Electron Cyclotron Emission (ECE) and of the Fast Electron Bremsstrahlung (FEB) measurements has been made, allowing the relevant parameters of the suprathermal electrons to be estimated. (author) 5 refs., 5 figs., 2 tabs.

Characterization of LH induced current carrying fast electrons in JET

International Nuclear Information System (INIS)

Ramponi, G.; Airoldi, A.; Bartlett, D.; Brusati, M.; Froissard, P.; Gormezano, C.; Rimini, F.; Silva, R.P. da; Tanzi, C.P.

1992-01-01

Lower Hybrid Current Drive (LHCD) experiments have recently been made at JET by coupling up to 2.4 MW of RF power at 3.7 GHz, with a power spectrum centered at n || = 1.8 ± 0.2 corresponding to a resonating electron energy of about 100 keV via Electron Landau Damping. The Current Drive (CD) efficiency has been observed to increase when LH and ICRH power are applied simultaneously to the plasma, suggesting that a part of the fast magnetosonic wave is absorbed on the LH-generated fast electrons. An important problem of CD experiments in tokamaks is the determination of the radial distribution of the driven current and the characterization in the momentum space of the current carrying fast electrons by using appropriate diagnostic tools. For this purpose, a combined analysis of the Electron Cyclotron Emission (ECE) and of the Fast Electron Bremsstrahlung (FEB) measurements has been made, allowing the relevant parameters of the suprathermal electrons to be estimated. (author) 5 refs., 5 figs., 2 tabs

Study of suprathermal electron transport in solid or compressed matter for the fast-ignitor scheme

International Nuclear Information System (INIS)

Perez, F.

2010-01-01

The inertial confinement fusion (ICF) concept is widely studied nowadays. It consists in quickly compressing and heating a small spherical capsule filled with fuel, using extremely energetic lasers. Since approximately 15 years, the fast-ignition (FI) technique has been proposed to facilitate the fuel heating by adding a particle beam - electrons generated by an ultra-intense laser - at the exact moment when the capsule compression is at its maximum. This thesis constitutes an experimental study of these electron beams generated by picosecond-scale lasers. We present new results on the characteristics of these electrons after they are accelerated by the laser (energy, divergence, etc.) as well as their interaction with the matter they pass through. The experimental results are explained and reveal different aspects of these laser-accelerated fast electrons. Their analysis allowed for significant progress in understanding several mechanisms: how they are injected into solid matter, how to measure their divergence, and how they can be automatically collimated inside compressed matter. (author) [fr

Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

International Nuclear Information System (INIS)

Goldston, R.J.; Towner, H.H.

1980-02-01

Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, beam ions become trapped in local magnetic wells near their banana tips due to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, near-perpendicular untrapped ions are captured (again near a banana tip) due to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced variable lingering period near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* identical with epsilon/sin theta/Nqdelta is of order unity or smaller

Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

International Nuclear Information System (INIS)

Goldston, R.J.; Towner, H.H.

1981-01-01

Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, ions become trapped in local magnetic wells near their banana tips owing to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, ions are captured (again near a banana tip) owing to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced 'variable lingering period' near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* is identical with epsilonsinthetaNqdelta is of order unity or smaller. (author)

Electricity electron measurement

International Nuclear Information System (INIS)

Kim, Sang Jin; Sung, Rak Jin

1985-11-01

This book deals with measurement of electricity and electron. It is divided into fourteen chapters, which depicts basic of electricity measurement, unit and standard, important electron circuit for measurement, instrument of electricity, impedance measurement, power and power amount measurement, frequency and time measurement, waveform measurement, record instrument and direct viewing instrument, super high frequency measurement, digital measurement on analog-digital convert, magnetic measurement on classification by principle of measurement, measurement of electricity application with principle sensors and systematization of measurement.

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

Electron foreshock

International Nuclear Information System (INIS)

Klimas, A.J.

1985-01-01

ISEE particle and wave data are noted to furnish substantial support for the basic features of the velocity dispersed model at the foreshock boundary that was proposed by Filbert and Kellogg (1979). Among many remaining discrepancies between this model and observation, it is noted that unstable reduced velocity distributions have been discovered behind the thin boundary proposed by the model, and that these are at suprathermal energies lying far below those explainable in terms of an oscillating, two-stream instability. Although the long-theorized unstable beam of electrons has been found in the foreshock, there is still no ready explanation of the means by which it could have gotten there. 16 references

Experimental reslts from the HERO project: In situ measurements of ionospheric modifications using sounding rockets

International Nuclear Information System (INIS)

Rose, G.; Grandal, B.; Neske, E.; Ott, W.; Spenner, K.; Maseide, K.; Troim, J.

1985-01-01

The Heating Rocket project HERO comprised the first in situ experiments to measure artifical ionospheric modifications at F layer heights set up by radio waves transmitted from the Heating facility at Ramfjord near Tromso in Northern Norway. Four instrumented payloads were launched on sounding rockets from Andoya Rocket Range during the autumn of 1982 into a sunlit ionosphere with the sun close to the horizon. The payloads recorded modifications, in particular, the presence of electron plasma waves near the reflection level of the heating wave. The amplitude and phase of the three components of the electric and magnetic fields of the heating wave were measured simultaneously as a function of altitude. Coherent spectra of the three electric field components of the locally generated electron plasma waves were obtained in a 50-kHz-wide band. At the same time quasi-continuous measurements were made on several fixed frequencies from 4 kHz to 16 kHz below the heating frequency and in the VLF-range using linear dipole antennas. Moreover, measurements were made of electron temperature, suprathermal electrons and local electron density along the rocket trajectory. The experimental results will be presented and discussed

Observation and interpretation of particle and electric field measurements inside and adjacent to an active auroral arc

International Nuclear Information System (INIS)

Carlson, C.W.; Kelley, M.C.

1977-01-01

A Javelin sounding rocket instrumented to measure electric fields, energetic particles, and suprathermal electrons was flown across an auroral display in the late expansion phase of a substorm. Four distinct regions of fields and particles were interpreted here in light of our present understanding of auroral dynamics.r of 10 and resemble fluxes mesured in the equatorial plane during the expansion phase. The hard fluxes in the equatorward zone are further energized and may act as a source for the outer radiation belt as inward convection further energizes them

Electron cyclotron waves, transport and instabilities in hot plasmas

International Nuclear Information System (INIS)

Westerhof, E.

1987-01-01

A number of topics relevant to the magnetic confinement approach to the thermonuclear fusion is addressed. The absorption and emission of electron cyclotron waves in a thermal plasma with a small population of supra-thermal, streaming electrons is examined and the properties of electron cyclotron waves in a plasma with a pure loss-cone distribution are studied. A report is given on the 1-D transport code simulations that were performed to assist the interpretation of the electron cyclotron heating experiments on the TFR tokamak. Transport code simulations of sawteeth discharges in the T-10 tokamak are discussed in order to compare the predictions of different models for the sawtooth oscillations with the experimental findings. 149 refs.; 69 figs.; 7 tabs

Artificial electron beams in the magnetosphere and ionosphere

International Nuclear Information System (INIS)

Winckler, J.R.

1990-01-01

The Plasma Diagnostics Payload of the Echo 7 satellite carried TV cameras and photometers by means of which the luminosity around an electron beam in the polar ionosphere could be studied. It was found that, while the beam Larmor spiral could be clearly seen near 100 km, above this only a column due to suprathermal electrons was observable. At high altitudes, the emission of neutral gas both generated powerful luminosity and substantially reduced accelerator potentials. An analysis of conjugate echoes indicates that inferred magnetospheric electric fields do not map well into the ionosphere, as well as the presence of strong pitch-angle scattering. 11 refs

The Lunar Potential Determination Using Apollo-Era Data and Modern Measurements and Models

Science.gov (United States)

Collier, Michael R.; Farrell, William M.; Espley, Jared; Webb, Phillip; Stubbs, Timothy J.; Webb, Phillip; Hills, H. Kent; Delory, Greg

2008-01-01

Since the Apollo era the electric potential of the Moon has been a subject of interest and debate. Deployed by three Apollo missions, Apollo 12, Apollo 14 and Apollo 15, the Suprathermal Ion Detector Experiment (SIDE) determined the sunlit lunar surface potential to be about +10 Volts using the energy spectra of lunar ionospheric thermal ions accelerated toward the Moon. More recently, the Lunar Prospector (LP) Electron Reflectometer used electron distributions to infer negative lunar surface potentials, primarily in shadow. We will present initial results from a study to combine lunar surface potential measurements from both SIDE and the LP/Electron Reflectometer to calibrate an advanced model of lunar surface charging which includes effects from the plasma environment, photoemission, secondaries ejected by ion impact onto the lunar surface, and the lunar wake created downstream by the solar wind-lunar interaction.

Edge density profile measurements by X-mode reflectometry on Tore Supra

International Nuclear Information System (INIS)

Clairet, F.; Bottereau, C.; Chareau, J.M.; Paume, M.; Sabot, R.

2000-10-01

A broadband reflectometer operating in the frequency range 50-75 GHz has been developed on Tore Supra to measure electron density profiles at the edge. The system uses extraordinary mode polarization and performs routine measurements in 20 μs with a heterodyne detection to ensure a high dynamic range sensitivity. It allows separate phase and amplitude information of the signal. The density profiles are fully automatically calculated from the raw phase. The initialization is done with an automatic detection of the first cut-off from the amplitude of the reflected signal with accuracy up to ±0.5 cm. The profiles are now part of the public database of Tore Supra (TS) and can provide details of density structures better than the centimeter range. High reliability of the measurements for various plasma conditions make this diagnostic an ideal tool to study specific edge plasma physics with given examples on detached plasma behaviour and RF antenna-plasma coupling processes. It also is shown how the presence of suprathermal electrons may perturb the measurements. (authors)

Self-consistent electric field effect on electron transport of ECH plasmas

International Nuclear Information System (INIS)

Chan, V.S.; Murakami, S.

1999-02-01

An algorithm is proposed which treats the ECH generated potential in a self-consistent way, by extending the Monte-Carlo Fokker-Planck method used by Murakami [S. Murakami et al., Proc. 17th IAEA Fusion Energy Conference, Yokohama, 1998 (International Atomic Energy Agency, Vienna, in press), paper CN-69/TH2/1]. The additional physics is expected to influence the transport of both thermal and suprathermal electrons in a helical toroidal system. (author)

Suprathermal ions in the solar wind from the Voyager spacecraft: Instrument modeling and background analysis

International Nuclear Information System (INIS)

Randol, B M; Christian, E R

2015-01-01

Using publicly available data from the Voyager Low Energy Charged Particle (LECP) instruments, we investigate the form of the solar wind ion suprathermal tail in the outer heliosphere inside the termination shock. This tail has a commonly observed form in the inner heliosphere, that is, a power law with a particular spectral index. The Voyager spacecraft have taken data beyond 100 AU, farther than any other spacecraft. However, during extended periods of time, the data appears to be mostly background. We have developed a technique to self-consistently estimate the background seen by LECP due to cosmic rays using data from the Voyager cosmic ray instruments and a simple, semi-analytical model of the LECP instruments

Study of ion cyclotron fluctuations. Application to the measurement of the ion temperature

International Nuclear Information System (INIS)

Lehner, T.

1982-02-01

A diagnostic technique for measuring the ion temperature of tokamak-type plasmas was developed. A theoretical study was made of the form factor associated with the ion cyclotron waves; the influence of Te/Ti on the frequency of the extrema of the dispersion relations was demonstrated. The different effects able to modify the spectral density (in particular the drift velocity and the impurities) were investigated. The mechanisms of suprathermal excitation of cylotron waves in tokamaks were reviewed together with the various effects stabilizing the spectrum: collisions, shear of the magnetic field lines. The experimental realization of the diagnostic technique is based on Thomson scattering by the electron density fluctuations [fr

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

International Nuclear Information System (INIS)

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

2003-01-01

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

Runaway electron generation as possible trigger for enhancement of magnetohydrodynamic plasma activity and fast changes in runaway beam behavior

International Nuclear Information System (INIS)

Pankratov, I. M.; Zhou, R. J.; Hu, L. Q.

2015-01-01

Peculiar phenomena were observed during experiments with runaway electrons: rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the electron cyclotron emission (ECE) signal (cyclotron radiation of suprathermal electrons). These phenomena were initially observed in TEXTOR (Tokamak Experiment for Technology Oriented Research), where these events only occurred in the current decay phase or in discharges with thin stable runaway beams at a q = 1 drift surface. These rapid changes in the synchrotron spot were interpreted by the TEXTOR team as a fast pitch angle scattering event. Recently, similar rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the non-thermal ECE signal were observed in the EAST (Experimental Advanced Superconducting Tokamak) runaway discharge. Runaway electrons were located around the q = 2 rational magnetic surface (ring-like runaway electron beam). During the EAST runaway discharge, stepwise ECE signal increases coincided with enhanced magnetohydrodynamic (MHD) activity. This behavior was peculiar to this shot. In this paper, we show that these non-thermal ECE step-like jumps were related to the abrupt growth of suprathermal electrons induced by bursting electric fields at reconnection events during this MHD plasma activity. Enhancement of the secondary runaway electron generation also occurred simultaneously. Local changes in the current-density gradient appeared because of local enhancement of the runaway electron generation process. These current-density gradient changes are considered to be a possible trigger for enhancement of the MHD plasma activity and the rapid changes in runaway beam behavior

Runaway electron generation as possible trigger for enhancement of magnetohydrodynamic plasma activity and fast changes in runaway beam behavior

Energy Technology Data Exchange (ETDEWEB)

Pankratov, I. M., E-mail: pankratov@kipt.kharkov.ua, E-mail: rjzhou@ipp.ac.cn [Institute of Plasma Physics, NSC Kharkov Institute of Physics and Technology, Academicheskaya Str. 1, 61108 Kharkov (Ukraine); Zhou, R. J., E-mail: pankratov@kipt.kharkov.ua, E-mail: rjzhou@ipp.ac.cn; Hu, L. Q. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2015-07-15

Peculiar phenomena were observed during experiments with runaway electrons: rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the electron cyclotron emission (ECE) signal (cyclotron radiation of suprathermal electrons). These phenomena were initially observed in TEXTOR (Tokamak Experiment for Technology Oriented Research), where these events only occurred in the current decay phase or in discharges with thin stable runaway beams at a q = 1 drift surface. These rapid changes in the synchrotron spot were interpreted by the TEXTOR team as a fast pitch angle scattering event. Recently, similar rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the non-thermal ECE signal were observed in the EAST (Experimental Advanced Superconducting Tokamak) runaway discharge. Runaway electrons were located around the q = 2 rational magnetic surface (ring-like runaway electron beam). During the EAST runaway discharge, stepwise ECE signal increases coincided with enhanced magnetohydrodynamic (MHD) activity. This behavior was peculiar to this shot. In this paper, we show that these non-thermal ECE step-like jumps were related to the abrupt growth of suprathermal electrons induced by bursting electric fields at reconnection events during this MHD plasma activity. Enhancement of the secondary runaway electron generation also occurred simultaneously. Local changes in the current-density gradient appeared because of local enhancement of the runaway electron generation process. These current-density gradient changes are considered to be a possible trigger for enhancement of the MHD plasma activity and the rapid changes in runaway beam behavior.

Runaway electron generation as possible trigger for enhancement of magnetohydrodynamic plasma activity and fast changes in runaway beam behavior

Science.gov (United States)

Pankratov, I. M.; Zhou, R. J.; Hu, L. Q.

2015-07-01

Peculiar phenomena were observed during experiments with runaway electrons: rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the electron cyclotron emission (ECE) signal (cyclotron radiation of suprathermal electrons). These phenomena were initially observed in TEXTOR (Tokamak Experiment for Technology Oriented Research), where these events only occurred in the current decay phase or in discharges with thin stable runaway beams at a q = 1 drift surface. These rapid changes in the synchrotron spot were interpreted by the TEXTOR team as a fast pitch angle scattering event. Recently, similar rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the non-thermal ECE signal were observed in the EAST (Experimental Advanced Superconducting Tokamak) runaway discharge. Runaway electrons were located around the q = 2 rational magnetic surface (ring-like runaway electron beam). During the EAST runaway discharge, stepwise ECE signal increases coincided with enhanced magnetohydrodynamic (MHD) activity. This behavior was peculiar to this shot. In this paper, we show that these non-thermal ECE step-like jumps were related to the abrupt growth of suprathermal electrons induced by bursting electric fields at reconnection events during this MHD plasma activity. Enhancement of the secondary runaway electron generation also occurred simultaneously. Local changes in the current-density gradient appeared because of local enhancement of the runaway electron generation process. These current-density gradient changes are considered to be a possible trigger for enhancement of the MHD plasma activity and the rapid changes in runaway beam behavior.

Electron Fishbone Simulations in FTU-like Equilibria Using XHMGC

Energy Technology Data Exchange (ETDEWEB)

Vlad, G.; Briguglio, S.; Fogaccia, G.; Zonca, F.; Di Troia, C.; Fusco, V.; Wang, X., E-mail: gregorio.vlad@enea.it [Associazione Euratom-ENEA sulla Fusione, Rome (Italy); IFTS, Zhejiang University, Hangzhou (China)

2012-09-15

Full text: Internal kink instabilities exhibiting fishbone like frequency chirp down have been observed in a variety of experiments where a high energy electron population was present. The relevance of the electron fishbones is primarily related to the fact that suprathermal electrons are characterized by relatively small orbit width, when compared with those of fast ions, similarly to the case of alpha particles in burning plasmas: thus, electron fishbones offer the opportunity to study the coupling between energetic particles and MHD modes in burning plasma relevant conditions even in present machines. In fact, precession resonance depends on energy, not mass; meanwhile, suprathermal electron transport perpendicular to the equilibrium magnetic field caused by fishbones can reflect some properties of fluctuation induced transport of fusion alphas due to precession resonance. The nonlinear MHD-Gyrokinetic code (HMGC) has been recently extended (from which the name XHMGC) to include new physics, including both thermal ion compressibility and diamagnetic effects, and finite parallel electric field due to parallel thermal electron pressure gradient, which enters the parallel Ohm's law and generalizes it, accounting for the kinetic thermal plasma response. Moreover, XHMGC is now able to treat up to three independent particle populations kinetically, assuming different equilibrium distribution functions (as, e.g., bulk ions, energetic (ion and/or electrons) particles accelerated by NBI, ICRH, fusion generated alpha particles, etc.). We will refer to the typical parameters of the FTU machine, where electron fishbones appearance has occurred in Lower Hybrid heated discharges. The FTU-like equilibrium corresponds to a torus with circular shape cross section, with an inverse aspect ratio {approx} 0.3. The safety factor profile has been assumed slightly reversed. Energetic electrons, described by a strongly anisotropic Maxwellian distribution function (thus, retaining

Suppression of suprathermal ions from a colloidal microjet target containing SnO2 nanoparticles by using double laser pulses

International Nuclear Information System (INIS)

Higashiguchi, Takeshi; Kaku, Masanori; Katto, Masahito; Kubodera, Shoichi

2007-01-01

We have demonstrated suppression of suprathermal ions from a colloidal microjet target plasma containing tin-dioxide (SnO 2 ) nanoparticles irradiated by double laser pulses. We observed a significant decrease of the tin and oxygen ion signals in the charged-state-separated energy spectra when double laser pulses were irradiated. The peak energy of the singly ionized tin ions decreased from 9 to 3 keV when a preplasma was produced. The decrease in the ion energy, considered as debris suppression, is attributed to the interaction between an expanding low-density preplasma and a main laser pulse

Suppression of suprathermal ions from a colloidal microjet target containing SnO2 nanoparticles by using double laser pulses

Science.gov (United States)

Higashiguchi, Takeshi; Kaku, Masanori; Katto, Masahito; Kubodera, Shoichi

2007-10-01

We have demonstrated suppression of suprathermal ions from a colloidal microjet target plasma containing tin-dioxide (SnO2) nanoparticles irradiated by double laser pulses. We observed a significant decrease of the tin and oxygen ion signals in the charged-state-separated energy spectra when double laser pulses were irradiated. The peak energy of the singly ionized tin ions decreased from 9to3keV when a preplasma was produced. The decrease in the ion energy, considered as debris suppression, is attributed to the interaction between an expanding low-density preplasma and a main laser pulse.

Observation of suprathermal electron fluxes during ionospheric modification experiments

International Nuclear Information System (INIS)

Fejer, J.A.; Sulzer, M.P.

1987-01-01

The temporal behavior of backscatter by ionospheric Langmuir waves was observed with the 430-MHz radar at Arecibo while a powerful HF wave was cycled 2 s on, 3 s off. The time resolution was 0.1 s. Late at night, in the absence of photoelectrons, using an HF equivalent radiated power of 80 MW at 3.175 MHz, the initial enhancement of about 6% above system noise of the backscattered power with Doppler shifts between -3.75 and -3.85 MHz was reached about 0.25 s after switching on the HF transmitter. In the following second the enhancement gradually decreased to about 3% and remained there until switching off. During the late afternoon, in the presence of photoelectrons, using the same HF power at 5.1 MHz, an initial enhancement by 25% of the backscattered power with Doppler shifts between -5.25 and -5.35 MHz appeared within less than 0.1 s after switching on the HF transmitter. The incoherent backscatter by Langmuir waves enhanced by photoelectrons was already above system noise by a factor greatly in excess of 10 before switching on the HF transmitter; the 25% enhancement thus corresponds to an enhancement greatly in excess of 250% above system noise. The enhancement drops to less than one tenth of its original value in less than a second. The nighttime effect is attributed to multiple acceleration of electrons from the high-energy tail of the Maxwellian distribution. The daytime effect is believed to be due to a modification in the distribution function of photoelectrons

Demonstration of Electron Bernstein Wave Heating in a Reversed Field Pinch

Science.gov (United States)

Seltzman, Andrew H.

The Electron Bernstein wave (EBW) presents an alternative to conventional electron cyclotron resonance heating and current drive in overdense plasmas, where electromagnetic waves are inaccessible. The first observation of rf heating in a reversed field pinch (RFP) using the EBW has been demonstrated on Madison Symmetric Torus (MST). The EBW propagates radially inward through a magnetic field that is either stochastic or has broken flux surfaces, before absorption on a substantially Doppler-shifted cyclotron resonance (? = n*?_ce - k_parallel*v_parallel), where n is the harmonic number. Deposition depth is controllable with plasma current on a broad range (n=1-7) of harmonics. Novel techniques were required to measure the suprathermal electron tail generated by EBW heating in the presence of intense Ohmic heating. In the thick-shelled MST RFP, the radial accessibility of the EBW is limited to r/a > 0.8 ( 10 cm), where a=52cm is the minor radius, by magnetic field error induced by the porthole necessary for the antenna; accessibility in a thin-shelled device with actively controlled saddle coils (without the burden of substantial porthole field error) is likely to be r/a> 0.5 in agreement with ray tracing studies. Measured electron loss rates with falloff time constants in the 10s of micros imply a large, non-collisional radial diffusivity; collisional times with background particles are on the order of one millisecond. EBW-heated test electrons are used as a probe of edge (r/a > 0.9) radial transport, showing a modest transition from 'standard' to reduced-tearing RFP operation.

Electron beam interaction with space plasmas.

Science.gov (United States)

Krafft, C.; Bolokitin, A. S.

1999-12-01

Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification.

Self-similar variables and the problem of nonlocal electron heat conductivity

International Nuclear Information System (INIS)

Krasheninnikov, S.I.; Bakunin, O.G.

1993-10-01

Self-similar solutions of the collisional electron kinetic equation are obtained for the plasmas with one (1D) and three (3D) dimensional plasma parameter inhomogeneities and arbitrary Z eff . For the plasma parameter profiles characterized by the ratio of the mean free path of thermal electrons with respect to electron-electron collisions, γ T , to the scale length of electron temperature variation, L, one obtains a criterion for determining the effect that tail particles with motion of the non-diffusive type have on the electron heat conductivity. For these conditions it is shown that the use of a open-quotes symmetrizedclose quotes kinetic equation for the investigation of the strong nonlocal effect of suprathermal electrons on the electron heat conductivity is only possible at sufficiently high Z eff (Z eff ≥ (L/γ T ) 1/2 ). In the case of 3D inhomogeneous plasma (spherical symmetry), the effect of the tail electrons on the heat transport is less pronounced since they are spread across the radius r

Generation and Beaming of Early Hot Electrons onto the Capsule in Laser-Driven Ignition Hohlraums

Science.gov (United States)

Dewald, E. L.; Hartemann, F.; Michel, P.; Milovich, J.; Hohenberger, M.; Pak, A.; Landen, O. L.; Divol, L.; Robey, H. F.; Hurricane, O. A.; Döppner, T.; Albert, F.; Bachmann, B.; Meezan, N. B.; MacKinnon, A. J.; Callahan, D.; Edwards, M. J.

2016-02-01

In hohlraums for inertial confinement fusion (ICF) implosions on the National Ignition Facility, suprathermal hot electrons, generated by laser plasma instabilities early in the laser pulse ("picket") while blowing down the laser entrance hole (LEH) windows, can preheat the capsule fuel. Hard x-ray imaging of a Bi capsule surrogate and of the hohlraum emissions, in conjunction with the measurement of time-resolved bremsstrahlung spectra, allows us to uncover for the first time the directionality of these hot electrons and infer the capsule preheat. Data and Monte Carlo calculations indicate that for most experiments the hot electrons are emitted nearly isotropically from the LEH. However, we have found cases where a significant fraction of the generated electrons are emitted in a collimated beam directly towards the capsule poles, where their local energy deposition is up to 10 × higher than the average preheat value and acceptable levels for ICF implosions. The observed "beaming" is consistent with a recently unveiled multibeam stimulated Raman scattering model [P. Michel et al., Phys. Rev. Lett. 115, 055003 (2015)], where laser beams in a cone drive a common plasma wave on axis. Finally, we demonstrate that we can control the amount of generated hot electrons by changing the laser pulse shape and hohlraum plasma.

Ion acoustic solitons in a plasma with two-temperature kappa-distributed electrons

International Nuclear Information System (INIS)

Baluku, T. K.; Hellberg, M. A.

2012-01-01

Existence domains and characteristics of ion acoustic solitons are studied in a two-temperature electron plasma with both electron components being kappa-distributed, as found in Saturn's magnetosphere. As is the case for double-Boltzmann electrons, solitons of both polarities can exist over restricted ranges of fractional hot electron density ratio for this plasma model. Low κ values, which indicate increased suprathermal particles in the tail of the distribution, yield a smaller domain in the parameter space of hot density fraction and normalized soliton velocity (f, M), over which both soliton polarities are supported for a given plasma composition (the coexistence region). For some density ratios that support coexistence, solitons occur even at the lowest (critical) Mach number (i.e., at the acoustic speed), as found recently for a number of other plasma models. Like Maxwellians, low-κ distributions also support positive potential double layers over a narrow range of low fractional cool electron density (<10%).

Ion acoustic solitons in a plasma with two-temperature kappa-distributed electrons

Energy Technology Data Exchange (ETDEWEB)

Baluku, T. K.; Hellberg, M. A. [School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000 (South Africa)

2012-01-15

Existence domains and characteristics of ion acoustic solitons are studied in a two-temperature electron plasma with both electron components being kappa-distributed, as found in Saturn's magnetosphere. As is the case for double-Boltzmann electrons, solitons of both polarities can exist over restricted ranges of fractional hot electron density ratio for this plasma model. Low {kappa} values, which indicate increased suprathermal particles in the tail of the distribution, yield a smaller domain in the parameter space of hot density fraction and normalized soliton velocity (f, M), over which both soliton polarities are supported for a given plasma composition (the coexistence region). For some density ratios that support coexistence, solitons occur even at the lowest (critical) Mach number (i.e., at the acoustic speed), as found recently for a number of other plasma models. Like Maxwellians, low-{kappa} distributions also support positive potential double layers over a narrow range of low fractional cool electron density (<10%).

Solar Wind 0.1-1 keV Electrons in the Corotating Interaction Regions

Science.gov (United States)

Wang, L.; Tao, J.; Li, G.; Wimmer-Schweingruber, R. F.; Jian, L. K.; He, J.; Tu, C.; Tian, H.; Bale, S. D.

2017-12-01

Here we present a statistical study of the 0.1-1 keV suprathermal electrons in the undisturbed and compressed slow/fast solar wind, for the 71 corotating interaction regions (CIRs) with good measurements from the WIND 3DP and MFI instruments from 1995 to 1997. For each of these CIRs, we separate the strahl and halo electrons based on their different behaviors in pitch angle distributions in the undisturbed and compressed solar wind. We fit both the strahl and halo energy spectra to a kappa function with an index κ index and effective temperature Teff, and calculate the pitch-angle width at half-maximum (PAHM) of the strahl population. We also integrate the electron measurements between 0.1 and 1.0 keV to obtain the number density n and average energy Eavg for the strahl and halo populations. We find that for both the strahl and halo populations within and around these CIRs, the fitted κ index strongly correlates with Teff, similar to the quiet-time solar wind (Tao et al., ApJ, 2016). The number density of both the strahl and halo shows a strong positive correlation with the electron core temperature. The strahl number density ns is correlated with the magnitude of interplanetary magnetic field, and the strahl PAHM width is anti-correlated with the solar wind speed. These results suggest that the origin of strahl electrons from the solar corona is likely related to the electron core temperature and magnetic field strength, while the production of halo electrons in the interplanetary medium could depend on the solar wind velocity.

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

Radially localized measurements of superthermal electrons using oblique electron cyclotron emission

International Nuclear Information System (INIS)

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

1996-05-01

It is shown that radial localization of optically tin Electron Cyclotron Emission from superthermal electrons can be imposed by observation of emission upshifted from the thermal cyclotron resonance in the horizontal midplane of a tokamak. A new and unique diagnostic has been proposed and operated to make radially localized measurements of superthermal electrons during Lower Hybrid Current Drive on the PBX-M tokamak. The superthermal electron density profile as well as moments of the electron energy distribution as a function of radius are measured during Lower Hybrid Current Drive. The time evolution of these measurements after the Lower Hybrid power is turned off are given and the observed behavior reflects the collisional isotropization of the energy distribution and radial diffusion of the spatial profile

Electron precipitation control of the Mars nightside ionosphere

Science.gov (United States)

Lillis, R. J.; Girazian, Z.; Mitchell, D. L.; Adams, D.; Xu, S.; Benna, M.; Elrod, M. K.; Larson, D. E.; McFadden, J. P.; Andersson, L.; Fowler, C. M.

2017-12-01

The nightside ionosphere of Mars is known to be highly variable, with densities varying substantially with ion species, solar zenith angle, solar wind conditions and geographic location. The factors that control its structure include neutral densities, day-night plasma transport, plasma temperatures, dynamo current systems driven by neutral winds, solar energetic particle events, superthermal electron precipitation, chemical reaction rates and the strength, geometry and topology of crustal magnetic fields. The MAVEN mission has been the first to systematically sample the nightside ionosphere by species, showing that shorter-lived species such as CO2+ and O+ are more correlated with electron precipitation flux than longer lived species such as O2+ and NO+, as would be expected, and is shown in the figure below from Girazian et al. [2017, under review at Geophysical Research Letters]. In this study we use electron pitch-angle and energy spectra from the Solar Wind Electron Analyzer (SWEA) and Solar Energetic Particle (SEP) instruments, ion and neutral densities from the Neutral Gas and Ion Mass Spectrometer (NGIMS), electron densities and temperatures from the Langmuir Probe and Waves (LPW) instrument, as well as electron-neutral ionization cross-sections. We present a comprehensive statistical study of electron precipitation on the Martian nightside and its effect on the vertical, local-time and geographic structure and composition of the ionosphere, over three years of MAVEN observations. We also calculate insitu electron impact ionization rates and compare with ion densities to judge the applicability of photochemical models of the formation and maintenance of the nightside ionosphere. Lastly, we show how this applicability varies with altitude and is affected by ion transport measured by the Suprathermal and thermal Ion Composition (STATIC) instrument.

Electron shower transverse profile measurement

International Nuclear Information System (INIS)

Lednev, A.A.

1993-01-01

A method to measure the shower transverse profile is described. Calibration data of the lead-glass spectrometer GAMS collected in a wide electron beam without any additional coordinate detector are used. The method may be used for the measurements in both cellular- and projective-type spectrometers. The results of measuring the 10 GeV electron shower profile in the GAMS spectrometer, without optical grease between the lead-glass radiators and photomultipliers, are approximated with an analytical function. The estimate of the coordinate accuracy is obtained. 5 refs., 8 figs

Electronic Warfare Signature Measurement Facility

Data.gov (United States)

Federal Laboratory Consortium — The Electronic Warfare Signature Measurement Facility contains specialized mobile spectral, radiometric, and imaging measurement systems to characterize ultraviolet,...

Source Population and Acceleration Location of Suprathermal Heavy Ions in Corotating Interaction Regions

Energy Technology Data Exchange (ETDEWEB)

Filwett, R. J.; Desai, M. I. [University of Texas at San Antonio, San Antonio, TX (United States); Dayeh, M. A.; Broiles, T. W. [Southwest Research Institute, San Antonio, TX (United States)

2017-03-20

We have analyzed the ∼20–320 keV nucleon{sup −1} suprathermal (ST) heavy ion abundances in 41 corotating interaction regions (CIRs) observed by the Wind spacecraft from 1995 January to 2008 December. Our results are: (1) the CIR Fe/CNO and NeS/CNO ratios vary with the sunspot number, with values being closer to average solar energetic particle event values during solar maxima and lower than nominal solar wind values during solar minima. The physical mechanism responsible for the depleted abundances during solar minimum remains an open question. (2) The Fe/CNO increases with energy in the 6 events that occurred during solar maximum, while no such trends are observed for the 35 events during solar minimum. (3) The Fe/CNO shows no correlation with the average solar wind speed. (4) The Fe/CNO is well correlated with the corresponding upstream ∼20–320 keV nucleon{sup −1} Fe/CNO and not with the solar wind Fe/O measured by ACE in 31 events. Using the correlations between the upstream ∼20–40 keV nucleon{sup −1} Fe/CNO and the ∼20–320 keV nucleon{sup −1} Fe/CNO in CIRs, we estimate that, on average, the ST particles traveled ∼2 au along the nominal Parker spiral field line, which corresponds to upper limits for the radial distance of the source or acceleration location of ∼1 au beyond Earth orbit. Our results are consistent with those obtained from recent surveys, and confirm that CIR ST heavy ions are accelerated more locally, and are at odds with the traditional viewpoint that CIR ions seen at 1 au are bulk solar wind ions accelerated between 3 and 5 au.

Secondary electrons monitor for continuous electron energy measurements in UHF linac

International Nuclear Information System (INIS)

Zimek, Zbigniew; Bulka, Sylwester; Mirkowski, Jacek; Roman, Karol

2001-01-01

Continuous energy measurements have now became obligatory in accelerator facilities devoted to radiation sterilization process. This is one of several accelerator parameters like dose rate, beam current, bean scan parameters, conveyer speed which must be recorded as it is a required condition of accelerator validation procedure. Electron energy measurements are rather simple in direct DC accelerator, where the applied DC voltage is directly related to electron energy. High frequency linacs are not offering such opportunity in electron energy measurements. The analyzing electromagnet is applied in some accelerators but that method can be used only in off line mode before or after irradiation process. The typical solution is to apply the non direct method related to control and measurements certain accelerator parameters like beam current and microwave energy pulse power. The continuous evaluation of electron energy can be performed on the base of calculation and result comparison with calibration curve

Benchmarking NaI(Tl) Electron Energy Resolution Measurements

International Nuclear Information System (INIS)

Mengesha, Wondwosen; Valentine, J D.

2002-01-01

A technique for validating electron energy resolution results measured using the modified Compton coincidence technique (MCCT) has been developed. This technique relies on comparing measured gamma-ray energy resolution with calculated values that were determined using the measured electron energy resolution results. These gamma-ray energy resolution calculations were based on Monte Carlo photon transport simulations, the measured NaI(Tl) electron response, a simplified cascade sequence, and the measured electron energy resolution results. To demonstrate this technique, MCCT-measured NaI(Tl) electron energy resolution results were used along with measured gamma-ray energy resolution results from the same NaI(Tl) crystal. Agreement to within 5% was observed for all energies considered between the calculated and measured gamma-ray energy resolution results for the NaI(Tl) crystal characterized. The calculated gamma-ray energy resolution results were also compared with previously published gamma-ray energy resolution measurements with good agreement (<10%). In addition to describing the validation technique that was developed in this study and the results, a brief review of the electron energy resolution measurements made using the MCCT is provided. Based on the results of this study, it is believed that the MCCT-measured electron energy resolution results are reliable. Thus, the MCCT and this validation technique can be used in the future to characterize the electron energy resolution of other scintillators and to determine NaI(Tl) intrinsic energy resolution

Current scaling for the radiative characteristics of a micropinch discharge

International Nuclear Information System (INIS)

Dogov, A.N.

2005-01-01

The absolute vacuum UV and soft X-ray (hν > 100 eV) yield from a micropinch discharge of plasma is measured. The current scaling in the range of 30-250 kA is found for a number of the discharge parameters: the vacuum UV and soft X-ray yield, electron temperature, effective temperature of suprathermal electrons and energy of bremsstrahlung emission from thermal electrons. The experimental data are in a good agreement with the calculated data [ru

Transport effects with hot electrons in laser fusion. Final report, October 1, 1981-February 28, 1983

International Nuclear Information System (INIS)

Shkarofsky, I.P.

1983-02-01

Two explanations are offered which can account for heat inhibition found in laser-fusion experiments. The first explanation requires an anisotorpic electron velocity distribution with a higher temperature parallel to the surface than into the surface. This provides axial heat inhibition. Lateral heat inhibition is associated with azimuthal magnetic fields. The second explanation requires the presence of both hot suprathermal and thermal electrons. The hot electrons can cause the flux limiter to decrease substantially below the free-streaming limit in an intermediate range of collisionality. Conditions for this situation occur in the coronal region. We compare a Maxwellian distribution to an exp(-v 5 /v 5 /sub c/) variation for the cold electrons and find that the flux limiter decreases more for the latter case. The effects of collisions between cold and hot electrons is also looked into. The Cartesian tensor approach is used in the above investigations with various forms for the zeroth order electron velocity distribution function

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

Measurement of the tau lepton electronic branching fraction

International Nuclear Information System (INIS)

Akerib, D.S.; Barish, B.; Chadha, M.; Cowen, D.F.; Eigen, G.; Miller, J.S.; Urheim, J.; Weinstein, A.J.; Acosta, D.; Masek, G.; Ong, B.; Paar, H.; Sivertz, M.; Bean, A.; Gronberg, J.; Kutschke, R.; Menary, S.; Morrison, R.J.; Nelson, H.N.; Richman, J.D.; Tajima, H.; Schmidt, D.; Sperka, D.; Witherell, M.S.; Procario, M.; Yang, S.; Daoudi, M.; Ford, W.T.; Johnson, D.R.; Lingel, K.; Lohner, M.; Rankin, P.; Smith, J.G.; Alexander, J.P.; Bebek, C.; Berkelman, K.; Besson, D.; Browder, T.E.; Cassel, D.G.; Coffman, D.M.; Drell, P.S.; Ehrlich, R.; Galik, R.S.; Garcia-Sciveres, M.; Geiser, B.; Gittelman, B.; Gray, S.W.; Hartill, D.L.; Heltsley, B.K.; Honscheid, K.; Jones, C.; Kandaswamy, J.; Katayama, N.; Kim, P.C.; Kreinick, D.L.; Ludwig, G.S.; Masui, J.; Mevissen, J.; Mistry, N.B.; Ng, C.R.; Nordberg, E.; O'Grady, C.; Patterson, J.R.; Peterson, D.; Riley, D.; Sapper, M.; Selen, M.; Worden, H.; Worris, M.; Wuerthwein, F.; Avery, P.; Freyberger, A.; Rodriguez, J.; Stephens, R.; Yelton, J.; Cinabro, D.; Henderson, S.; Kinoshita, K.; Liu, T.; Saulnier, M.; Wilson, R.; Yamamoto, H.; Sadoff, A.J.; Ammar, R.; Ball, S.; Baringer, P.; Coppage, D.; Copty, N.; Davis, R.; Hancock, N.; Kelly, M.; Kwak, N.; Lam, H.; Kubota, Y.; Lattery, M.; Nelson, J.K.; Patton, S.; Perticone, D.; Poling, R.; Savinov, V.; Schrenk, S.; Wang, R.; Alam, M.S.; Kim, I.J.; Nemati, B.; O'Neill, J.J.; Romero, V.; Severini, H.; Sun, C.R.; Wang, P.; Zoeller, M.M.; Crawford, G.; Fulton, R.; Gan, K.K.; Kagan, H.; Kass, R.; Lee, J.; Malchow, R.; Morrow, F.; Sung, M.; White, C.; Whitmore, J.; Wilson, P.; Butler, F.; Fu, X.; Kalbfleisch, G.; Lambrecht, M.; Ross, W.R.; Skubic, P.; Snow, J.; Wang, P.; Bortoletto, D.; Brown, D.N.; Dominick, J.; McIlwain, R.L.; Miao, T.; Miller, D.H.; Modesitt, M.; Schaffner, S.F.; Shibata, E.I.; Shipsey, I.P.J.; Battle, M.; Ernst, J.; Kroha, H.; Roberts, S.; Sparks, K.; Thorndike, E.H.; Wang, C.; Sanghera, S.; Skwarnicki, T.; Stroynowski, R.; Artuso, M.; Goldberg, M.; Horwitz, N.

1992-01-01

The tau lepton electron branching fraction has been measured with the CLEO II detector at the Cornell Electron Storage Ring as B e =0.1749±0.0014±0.0022, with the first error statistical and the second systematic. The measurement involves counting electron-positron annihilation events in which both taus decay to electrons, and normalizing to the number of tau-pair decays expected from the measured luminosity. Detected photons in these events constitute a definitive observation of tau decay radiation

Electron cyclotron emission measurement in Tore Supra

International Nuclear Information System (INIS)

Javon, C.

1991-06-01

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

Langmuir wave-packet generation from an electron beam propagating in the inhomogeneous solar wind

International Nuclear Information System (INIS)

Zaslavsky, A.; Maksimovic, M.; Volokitin, A. S.; Krasnoselskikh, V. V.; Bale, S. D.

2010-01-01

Recent in-situ observations by the TDS instrument equipping the STEREO spacecraft revealed that large amplitude spatially localized Langmuir waves are frequent in the solar wind, and correlated with the presence of suprathermal electron beams during type III events or close to the electron foreshock. We briefly present the new theoretical model used to perform the study of these localized electrostatic waves, and show first results of simulations of the destabilization of Langmuir waves by a beam propagating in the inhomogeneous solar wind. The main results are that the destabilized waves are mainly focalized near the minima of the density profiles, and that the nonlinear interaction of the waves with the resonant particles enhances this focalization compared to a situation in which the only propagation effects are taken into account.

Electron-cloud measurements and simulations for the APS

International Nuclear Information System (INIS)

Furman, M.A.; Pivi, M.; Harkay, K.C.; Rosenberg, R.A.

2001-01-01

We compare experimental results with simulations of the electron cloud effect induced by a positron beam at the APS synchrotron light source at ANL, where the electron cloud effect has been observed and measured with dedicated probes. We find good agreement between simulations and measurements for reasonable values of certain secondary electron yield (SEY) parameters, most of which were extracted from recent bench measurements at SLAC

Plasma diffusion due to magnetic field fluctuations

International Nuclear Information System (INIS)

Okuda, H.; Lee, W.W.; Lin, A.T.

1979-01-01

Plasma diffusion due to magnetic field fluctuations has been studied in two dimensions for a plasma near thermal equilibrium and when the fluctuations are suprathermal. It is found that near thermal equilibrium electron diffusion varies as B -2 when the collisionless skin depth is greater than the thermal electron gyroradius and is generally smaller than the diffusion due to collisions or electrostatic fluctuations for a low-β plasma. When the suprathermal magnetic fluctuation exists because of macroscopic plasma currents, electron diffusion is enhanced due to the coalescence of current filaments and magnetic islands. Magnetic field energy is found to condense to the longest wavelength available in the system and stays there longer than the electron diffusion time scale

Creating space plasma from the ground

Science.gov (United States)

Carlson, H. C.; Djuth, F. T.; Zhang, L. D.

2017-01-01

We have performed an experiment to compare as directly as realizable the ionization production rate by HF radio wave energy versus by solar EUV. We take advantage of the commonality that ionization production by both ground-based high-power HF radio waves and by solar EUV is driven by primary and secondary suprathermal electrons near and above 20 eV. Incoherent scatter radar (ISR) plasma-line amplitudes are used as a measure of suprathermal electron fluxes for ISR wavelengths near those for 430 MHz and are indeed a clean measure of such for those fluxes sufficiently weak to have negligible self-damping. We present data from an HF heating experiment on November 2015 at Arecibo, which even more directly confirm the only prior midlatitude estimate, of order 10% efficiency for conversion of HF energy to ionospheric ionization. We note the theoretical maximum possible is 1/3, while 1% or less reduces the question to near practical irrelevance. Our measurements explicitly confirm the prediction that radio-frequency production of artificial ionospheres can be practicable, even at midlatitudes. Furthermore, that this midlatitude efficiency is comparable to efficiencies measured at high latitudes (which include enhancements unique to high latitudes including magnetic zenith effect, gyrofrequency multiples, and double resonances) requires reexamination of current theoretical thinking about soft-electron acceleration processes in weakly magnetized plasmas. The implications are that electron acceleration by any of a variety of processes may be a fundamental underpinning to energy redistribution in space plasmas.

Status of the Instrument Control Unit for EPD on-board Solar Orbiter

Science.gov (United States)

Sánchez Prieto, Sebastián; Da Silva, Antonio; Rodriguez Polo, Oscar; Parra Espada, Pablo; Gutierrez Molina, Oscar; Fernandez Salgado, Javier

Solar Orbiter is the next heliospheric mission sponsored by ESA. The launch is planned for 2017 and it will be as close as 0.28 AU from the Sun. One of the instruments for Solar Orbiter is the Energetic Particle Detector (EPD) responsible for measuring energies from 2 keV to 200 MeV/n. EPD consists of four detectors, Electron Proton Telescope (EPT), High Energy Telescope (HET), SupraThermal Electrons, Ions, & Neutrals (STEIN), and Suprathermal Ion Spectrograph (SIS), plus the Instrument Control Unit called ICU. The Space Research Group of the University of Alcalá in Spain is the responsible for developing the ICU. In this work we present the development status of the ICU after the Critical Design Review. We also address the planned activities for the next year including the development of the Engineering and Qualification Model (EQM) and Flight Model (PM). Special focus is paid to the software and verification & validation activities.

Preionization electron density measurement by collecting electric charge

International Nuclear Information System (INIS)

Giordano, G.; Letardi, T.

1988-01-01

A method using electron collection for preionization-electron number density measurements is presented. A cathode-potential drop model is used to describe the measurement principle. There is good agreement between the model and the experimental result

Transmission Electron Microscope Measures Lattice Parameters

Science.gov (United States)

Pike, William T.

1996-01-01

Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.

Debye-scale solitary structures measured in a beam-plasma laboratory experiment

Directory of Open Access Journals (Sweden)

B. Lefebvre

2011-01-01

Full Text Available Solitary electrostatic pulses have been observed in numerous places of the magnetosphere such as the vicinity of reconnection current sheets, shocks or auroral current systems, and are often thought to be generated by energetic electron beams. We present results of a series of experiments conducted at the UCLA large plasma device (LAPD where a suprathermal electron beam was injected parallel to a static magnetic field. Micro-probes with tips smaller than a Debye length enabled the detection of solitary pulses with positive electric potential and half-widths 4–25 Debye lengths (λ_De, over a set of experiments with various beam energies, plasma densities and magnetic field strengths. The shape, scales and amplitudes of the structures are similar to those observed in space, and consistent with electron holes. The dependance of these properties on the experimental parameters is shown. The velocities of the solitary structures (1–3 background electron thermal velocities are found to be much lower than the beam velocities, suggesting an excitation mechanism driven by parallel currents associated to the electron beam.

Spatial variations in the suprathermal ion distributions during substorms in the plasma sheet

International Nuclear Information System (INIS)

Kistler, L.M.; Moebius, E.; Klecker, B.; Gloeckler, G.; Ipavich, F.M.; Hamilton, D.C.

1990-01-01

Using data from AMPTE IRM and AMPTE CCE, the authors have determined the pre- and post-injection suprathermal energy spectra for the ion species H + , O + , He + , and He ++ for six events in which substorm-associated particle injections are observed in both the near-Earth plasma sheet and farther down the tail. They find similar spectral changes in both locations, with the spectra becoming harder with the injection. Post-injection, the flux decreases exponentially with radial distance. Approximately the same gradient is observed in all species. In addition, they find that although the O + /H + and the He ++ /H + ratios increase with energy per charge, the ratios are approximately the same at the same energy per charge at the two spacecraft. The observations are difficult to explain either with a model in which the ions are accelerated at a neutral line and transported toward Earth or with a model in which the ions are accelerated in the near-Earth region by current disruption/diversion and transported down the tail. In either case, the ions would have to be transported throughout the tail without much energization or deenergization in order to explain the energy per charge correlations. Further, earthward transport without energization would not lead to the observed radial gradient. A combination of these acceleration mechanisms, a disturbance that propagates throughout the plasma sheet, or a more global mechanism may explain the observations

Effects of lower hybrid fast electron populations on electron temperature measurements at JET

International Nuclear Information System (INIS)

Tanzi, C.P.; Bartlett, D.V.; Schunke, B.

1993-01-01

The Lower Hybrid Current Drive (LHCD) system on JET has to date achieved up to 1.5 MA of driven current. This current is carried by a fast electron population with energies more than ten times the electron temperature and density about 10 -4 of the bulk plasma. This paper discusses the effects of this fast electron population on our ability to make reliable temperature measurements using ECE and reviews the effects on other plasma diagnostics which rely on ECE temperature measurements for their interpretation. (orig.)

Three-wave electron vortex lattices for measuring nanofields.

Science.gov (United States)

Dwyer, C; Boothroyd, C B; Chang, S L Y; Dunin-Borkowski, R E

2015-01-01

It is demonstrated how an electron-optical arrangement consisting of two electron biprisms can be used to generate three-wave vortex lattices with effective lattice spacings between 0.1 and 1 nm. The presence of vortices in these lattices was verified by using a third biprism to perform direct phase measurements via off-axis electron holography. The use of three-wave lattices for nanoscale electromagnetic field measurements via vortex interferometry is discussed, including the accuracy of vortex position measurements and the interpretation of three-wave vortex lattices in the presence of partial spatial coherence. Copyright © 2014 Elsevier B.V. All rights reserved.

Energization of electrons in a plasma beam entering a curved magnetic field

International Nuclear Information System (INIS)

Brenning, N.; Lindberg, L.; Eriksson, A.

1980-09-01

Earlier experiments have indicated that suprathermal electrons appear when a collisionless plasma flowing along a magnetic field enters a region where the magnetic field is curved. In the present investigation newly developed methods of He-spectroscopy based on the absolute intensities of the He I 3889 A and He II 4686 A lines are utilized to study the electron temperature and to estimate the population of non-thermal electrons. The density of helium added for the diagnostic purpose is so low that the flow is not disturbed. It is found that the intrusion of the plasma into a curved or transverse field gives rise to a slight increase (15-20%) in the electron temperature and a remarkable increase in the fraction of non-thermal (>100 eV) electrons from below 1% to as much as 20-25% of the total electron population. There are also indications that the energization of electrons is particularly efficient on that side of the plasma beam which becomes polarized to a positive potential when entering the curved field. The experiments are confined to the case of weak magnetic field, i.e. only the electrons are magnetically confined. New details of the electric field and potential structure are presented and discussed. Electric field components parallel to the magnetic field are likely to energize the electrons, probably through the run-away phenomenon. (Auth.)

Emittance Measurements from a Laser Driven Electron Injector

Energy Technology Data Exchange (ETDEWEB)

Reis, David A

2003-07-28

The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 {angstrom}, the LCLS requires an electron injector that can produce an electron beam with approximately 1 {pi} mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the laser and electron beam at the GTF. A convolved measurement of the relative timing between the laser and the rf phase in the gun shows that the jitter is less than 2.5 ps rms. Emittance measurements of the electron beam at 35 MeV are reported as a function of the (Gaussian) pulse length and transverse profile of the laser as well as the charge of the electron beam at constant phase and gradient in both the gun and linac. At 1 nC the emittance was found to be {approx} 13 {pi} mm-mrad for 5 ps and 8 ps long laser pulses. At 0.5 nC the measured emittance decreased approximately 20% in the 5 ps case and 40% in the 8 ps case. These measurements are between 40-80% higher than simulations for similar experimental conditions. In addition, the thermal emittance of the electron beam was measured to be 0.5 {pi} mm-mrad.

Local charge measurement using off-axis electron holography

DEFF Research Database (Denmark)

Beleggia, Marco; Gontard, L.C.; Dunin-Borkowski, R.0E.

2016-01-01

A model-independent approach based on Gauss’ theorem for measuring the local charge in a specimen from an electron-optical phase image recorded using off-axis electron holography was recently proposed. Here, we show that such a charge measurement is reliable when it is applied to determine the to...

Counterstreaming electrons in small interplanetary magnetic flux ropes

Science.gov (United States)

Feng, H. Q.; Zhao, G. Q.; Wang, J. M.

2015-12-01

Small interplanetary magnetic flux ropes (SIMFRs) are commonly observed by spacecraft at 1 AU, and their origin still remains disputed. We investigated the counterstreaming suprathermal electron (CSE) signatures of 106 SIMFRs measured by Wind during 1995-2005. We found that 79 (75%) of the 106 flux ropes contain CSEs, and the percentages of counterstreaming vary from 8% to 98%, with a mean value of 51%. CSEs are often observed in magnetic clouds (MCs), and this indicates these MCs are still attached to the Sun at both ends. CSEs are also related to heliospheric current sheets (HCSs) and the Earth's bow shock. We divided the SIMFRs into two categories: The first category is far from HCSs, and the second category is in the vicinity of HCSs. The first category has 57 SIMFRs, and only 7 of 57 ropes have no CSEs. This ratio is similar to that of MCs. The second category has 49 SIMFRs; however, 20 of the 49 events have no CSEs. This ratio is larger than that of MCs. These two categories have different origins. One category originates from the solar corona, and most ropes are still connected to the Sun at both ends. The other category is formed near HCSs in the interplanetary space.

Electron Cloud Measurements in Fermilab Main Injector and Recycler

Energy Technology Data Exchange (ETDEWEB)

Eldred, Jeffrey Scott [Indiana U.; Backfish, M. [Fermilab; Tan, C. Y. [Fermilab; Zwaska, R. [Fermilab

2015-06-01

This conference paper presents a series of electron cloud measurements in the Fermilab Main Injector and Recycler. A new instability was observed in the Recycler in July 2014 that generates a fast transverse excitation in the first high intensity batch to be injected. Microwave measurements of electron cloud in the Recycler show a corresponding depen- dence on the batch injection pattern. These electron cloud measurements are compared to those made with a retard- ing field analyzer (RFA) installed in a field-free region of the Recycler in November. RFAs are also used in the Main Injector to evaluate the performance of beampipe coatings for the mitigation of electron cloud. Contamination from an unexpected vacuum leak revealed a potential vulnerability in the amorphous carbon beampipe coating. The diamond-like carbon coating, in contrast, reduced the electron cloud signal to 1% of that measured in uncoated stainless steel beampipe.

Electron bunch length measurement with a wakefield radiation decelerator

Directory of Open Access Journals (Sweden)

Weiwei Li

2014-03-01

Full Text Available In this paper, we propose a novel method to measure the electron bunch length with a dielectric wakefield radiation (DWR decelerator which is composed of two dielectric-lined waveguides (DLWs and an electron spectrometer. When an electron beam passes through a DLW, the DWR is excited which leads to an energy loss of the electron beam. The energy loss is found to be largely dependent on the electron bunch length and can be easily measured by an electron spectrometer which is essential for a normal accelerator facility. Our study shows that this method has a high resolution and a great simplicity.

Electron cyclotron emission measurements at the stellarator TJ-K

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-01

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

Measurements on wave propagation characteristics of spiraling electron beams

Science.gov (United States)

Singh, A.; Getty, W. D.

1976-01-01

Dispersion characteristics of cyclotron-harmonic waves propagating on a neutralized spiraling electron beam immersed in a uniform axial magnetic field are studied experimentally. The experimental setup consisted of a vacuum system, an electron-gun corkscrew assembly which produces a 110-eV beam with the desired delta-function velocity distribution, a measurement region where a microwave signal is injected onto the beam to measure wavelengths, and a velocity analyzer for measuring the axial electron velocity. Results of wavelength measurements made at beam currents of 0.15, 1.0, and 2.0 mA are compared with calculated values, and undesirable effects produced by increasing the beam current are discussed. It is concluded that a suitable electron beam for studies of cyclotron-harmonic waves can be generated by the corkscrew device.

Particle acceleration during merging-compression plasma start-up in the Mega Amp Spherical Tokamak

Science.gov (United States)

McClements, K. G.; Allen, J. O.; Chapman, S. C.; Dendy, R. O.; Irvine, S. W. A.; Marshall, O.; Robb, D.; Turnyanskiy, M.; Vann, R. G. L.

2018-02-01

Magnetic reconnection occurred during merging-compression plasma start-up in the Mega Amp Spherical Tokamak (MAST), resulting in the prompt acceleration of substantial numbers of ions and electrons to highly suprathermal energies. Accelerated field-aligned ions (deuterons and protons) were detected using a neutral particle analyser at energies up to about 20 keV during merging in early MAST pulses, while nonthermal electrons have been detected indirectly in more recent pulses through microwave bursts. However no increase in soft x-ray emission was observed until later in the merging phase, by which time strong electron heating had been detected through Thomson scattering measurements. A test-particle code CUEBIT is used to model ion acceleration in the presence of an inductive toroidal electric field with a prescribed spatial profile and temporal evolution based on Hall-MHD simulations of the merging process. The simulations yield particle distributions with properties similar to those observed experimentally, including strong field alignment of the fast ions and the acceleration of protons to higher energies than deuterons. Particle-in-cell modelling of a plasma containing a dilute field-aligned suprathermal electron component suggests that at least some of the microwave bursts can be attributed to the anomalous Doppler instability driven by anisotropic fast electrons, which do not produce measurable enhancements in soft x-ray emission either because they are insufficiently energetic or because the nonthermal bremsstrahlung emissivity during this phase of the pulse is below the detection threshold. There is no evidence of runaway electron acceleration during merging, possibly due to the presence of three-dimensional field perturbations.

Electron transport measurements in methane using an improved pulsed Townsend technique

International Nuclear Information System (INIS)

Hunter, S.R.; Carter, J.G.; Christophorou, L.G.

1986-01-01

An improved pulsed Townsend technique for the measurement of electron transport parameters in gases is described. The accuracy and sensitivity of the technique have been investigated by performing, respectively, electron attachment coefficient measurements in pure O 2 over a wide range of E/N at selected O 2 pressures and by determining the electron attachment and ionization coefficients and electron drift velocity in CH 4 over a wide E/N range. Good agreement has been obtained between the present and the previously published electron attachment coefficients in O 2 and for the drift velocity measurements in CH 4 . The data on the electron attachment coefficient in CH 4 (measured for the first time) showed that with the present improved pulsed Townsend method, electron attachment coefficients up to 10 times smaller than the ionization coefficients at a given E/N value can be accurately measured. Our measurements of the electron attachment and ionization coefficients in CH 4 are in good agreement with a Boltzmann equation analysis of the electron gain and loss processes in CH 4 using published electron scattering cross sections for this molecule

Dark-field electron holography for the measurement of geometric phase

International Nuclear Information System (INIS)

Hytch, M.J.; Houdellier, F.; Huee, F.; Snoeck, E.

2011-01-01

The genesis, theoretical basis and practical application of the new electron holographic dark-field technique for mapping strain in nanostructures are presented. The development places geometric phase within a unified theoretical framework for phase measurements by electron holography. The total phase of the transmitted and diffracted beams is described as a sum of four contributions: crystalline, electrostatic, magnetic and geometric. Each contribution is outlined briefly and leads to the proposal to measure geometric phase by dark-field electron holography (DFEH). The experimental conditions, phase reconstruction and analysis are detailed for off-axis electron holography using examples from the field of semiconductors. A method for correcting for thickness variations will be proposed and demonstrated using the phase from the corresponding bright-field electron hologram. -- Highlights: → Unified description of phase measurements in electron holography. → Detailed description of dark-field electron holography for geometric phase measurements. → Correction procedure for systematic errors due to thickness variations.

Quadrupole moments as measures of electron correlation in two-electron atoms

International Nuclear Information System (INIS)

Ceraulo, S.C.; Berry, R.S.

1991-01-01

We have calculated quadrupole moments, Q zz , of helium in several of its doubly excited states and in two of its singly excited Rydberg states, and of the alkaline-earth atoms Be, Mg, Ca, Sr, and Ba in their ground and low-lying excited states. The calculations use well-converged, frozen-core configuration-interaction (CI) wave functions and, for interpretive purposes, Hartree-Fock (HF) atomic wave functions and single-term, optimized, molecular rotor-vibrator (RV) wave functions. The quadrupole moments calculated using RV wave functions serve as a test of the validity of the correlated, moleculelike model, which has been used to describe the effects of electron correlation in these two-electron and pseudo-two-electron atoms. Likewise, the quadrupole moments calculated with HF wave functions test the validity of the independent-particle model. In addition to their predictive use and their application to testing simple models, the quadrupole moments calculated with CI wave functions reveal previously unavailable information about the electronic structure of these atoms. Experimental methods by which these quadrupole moments might be measured are also discussed. The quadrupole moments computed from CI wave functions are presented as predictions; measurements of Q zz have been made for only two singly excited Rydberg states of He, and a value of Q zz has been computed previously for only one of the states reported here. We present these results in the hope of stimulating others to measure some of these quadrupole moments

Relativistic Electrons Produced by Foreshock Disturbances Observed Upstream of Earth's Bow Shock

Science.gov (United States)

Wilson, L. B., III; Sibeck, D. G.; Turner, D. L.; Osmane, A.; Caprioli, D.; Angelopoulos, V.

2016-01-01

Charged particles can be reflected and accelerated by strong (i.e., high Mach number) astrophysical collisionless shock waves, streaming away to form a foreshock region in communication with the shock. Foreshocks are primarily populated by suprathermal ions that can generate foreshock disturbances-largescale (i.e., tens to thousands of thermal ion Larmor radii), transient (approximately 5-10 per day) structures. They have recently been found to accelerate ions to energies of several keV. Although electrons in Saturn's high Mach number (M > 40) bow shock can be accelerated to relativistic energies (nearly 1000 keV), it has hitherto been thought impossible to accelerate electrons beyond a few tens of keV at Earth's low Mach number (1 =M foreshock disturbances to energies up to at least approximately 300 keV. Although such energetic electrons have been previously observed, their presence has been attributed to escaping magnetospheric particles or solar events. These relativistic electrons are not associated with any solar or magnetospheric activity. Further, due to their relatively small Larmor radii (compared to magnetic gradient scale lengths) and large thermal speeds (compared to shock speeds), no known shock acceleration mechanism can energize thermal electrons up to relativistic energies. The discovery of relativistic electrons associated with foreshock structures commonly generated in astrophysical shocks could provide a new paradigm for electron injections and acceleration in collisionless plasmas.

Electron drift time in silicon drift detectors: A technique for high precision measurement of electron drift mobility

International Nuclear Information System (INIS)

Castoldi, A.; Rehak, P.

1995-01-01

This paper presents a precise absolute measurement of the drift velocity and mobility of electrons in high resistivity silicon at room temperature. The electron velocity is obtained from the differential measurement of the drift time of an electron cloud in a silicon drift detector. The main features of the transport scheme of this class of detectors are: the high uniformity of the electron motion, the transport of the signal electrons entirely contained in the high-purity bulk, the low noise timing due to the very small anode capacitance (typical value 100 fF), and the possibility to measure different drift distances, up to the wafer diameter, in the same semiconductor sample. These features make the silicon drift detector an optimal device for high precision measurements of carrier drift properties. The electron drift velocity and mobility in a 10 kΩ cm NTD n-type silicon wafer have been measured as a function of the electric field in the range of possible operation of a typical drift detector (167--633 V/cm). The electron ohmic mobility is found to be 1394 cm 2 /V s. The measurement precision is better than 1%. copyright 1995 American Institute of Physics

Electron Source Brightness and Illumination Semi-Angle Distribution Measurement in a Transmission Electron Microscope.

Science.gov (United States)

Börrnert, Felix; Renner, Julian; Kaiser, Ute

2018-05-21

The electron source brightness is an important parameter in an electron microscope. Reliable and easy brightness measurement routes are not easily found. A determination method for the illumination semi-angle distribution in transmission electron microscopy is even less well documented. Herein, we report a simple measurement route for both entities and demonstrate it on a state-of-the-art instrument. The reduced axial brightness of the FEI X-FEG with a monochromator was determined to be larger than 108 A/(m2 sr V).

Local texture measurements with the scanning electron microscope

International Nuclear Information System (INIS)

Gottstein, G.; Engler, O.

1993-01-01

Techniques for convenient measurement of the crystallographic orientation of small volumes in bulk samples by electron diffraction in the SEM are discussed. They make use of Selected Area Electron Channelling Patterns (SAECP) and Electron Back Scattering Patterns (EBSP). The principle of pattern formation as well as measuring and evaluation procedure are introduced. The methods offer a viable procedure for obtaining information on the spatial arrangement of orientations, i.e. on orientation topography. Thus, they provide a new level of information on crystallographic texture. An application of the techniques for local texture measurements is demonstrated by an example, namely for investigation of considering the recrystallization behaviour of binary Al-1.3% Mn with large precipitates. Finally, further developments of the EBSP technique are addressed. (orig.)

Development of electron temperature measuring system by silicon drift detector

International Nuclear Information System (INIS)

Song Xianying; Yang Jinwei; Liao Min

2007-12-01

Soft X-ray spectroscopy with two channels Silicon Drift Detector (SDD) are adopted for electron temperature measuring on HL-2A tokamak in 2005. The working principle, design and first operation of the SDD soft X-ray spectroscopy are introduced. The measuring results of electron temperature are also presented. The results show that the SDD is very good detector for electron temperature measuring on HL-2A tokamak. These will become a solid basic work to establish SDD array for electron temperature profiling. (authors)

A data driven method to measure electron charge mis-identification rate

CERN Document Server

Bakhshiansohi, Hamed

2009-01-01

Electron charge mis-measurement is an important challenge in analyses which depend on the charge of electron. To estimate the probability of {\\it electron charge mis-measurement} a data driven method is introduced and a good agreement with MC based methods is achieved.\\\\ The third moment of $\\phi$ distribution of hits in electron SuperCluster is studied. The correlation between this variable and the electron charge is also investigated. Using this `new' variable and some other variables the electron charge measurement is improved by two different approaches.

Measuring the electron beam energy in a magnetic bunch compressor

Energy Technology Data Exchange (ETDEWEB)

Hacker, Kirsten

2010-09-15

Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 {mu}m precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

Measuring the electron beam energy in a magnetic bunch compressor

International Nuclear Information System (INIS)

Hacker, Kirsten

2010-09-01

Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 μm precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

Wave and plasma measurements and GPS diagnostics of the main ionospheric trough as a hybrid method used for Space Weather purposes

Directory of Open Access Journals (Sweden)

H. Rothkaehl

2008-02-01

Full Text Available The region of the main ionospheric trough is a unique region of the ionosphere, where different types of waves and instabilities can be generated. This region of the ionosphere acts like a lens, focusing a variety of indicators from the equator of plasmapause and local ionospheric plasma. This paper reports the results of monitoring the mid-latitude trough structure, dynamics and wave activity. For these purposes, the data gathered by the currently-operating DEMETER satellite and past diagnostics located on IK-19, Apex, and MAGION-3 spacecraft, as well as TEC measurements were used. A global-time varying picture of the ionospheric trough was reconstructed using the sequence of wave spectra registered and plasma measurements in the top-side ionosphere. The authors present the wave activity from ULF frequency band to the HF frequency detected inside the trough region and discuss its properties during geomagnetic disturbances. It is thought that broadband emissions are correlated with low frequency radiation, which is excited by the wave-particle interaction in the equatorial plasmapause and moves to the ionosphere along the geomagnetic field line. In the ionosphere, the suprathermal electrons can interact with these electrostatic waves and excite electron acoustic waves or HF longitudinal plasma waves. Furthermore, the electron density trough can provide useful data on the magnetosphere ionosphere dynamics and morphology and, in consequence, can be used for Space Weather purposes.

Three-dimensional space charge distribution measurement in electron beam irradiated PMMA

International Nuclear Information System (INIS)

Imaizumi, Yoichi; Suzuki, Ken; Tanaka, Yasuhiro; Takada, Tatsuo

1996-01-01

The localized space charge distribution in electron beam irradiated PMMA was investigated using pulsed electroacoustic method. Using a conventional space charge measurement system, the distribution only in the depth direction (Z) can be measured assuming the charges distributed uniformly in the horizontal (X-Y) plane. However, it is difficult to measure the distribution of space charge accumulated in small area. Therefore, we have developed the new system to measure the three-dimensional space charge distribution using pulsed electroacoustic method. The system has a small electrode with a diameter of 1mm and a motor-drive X-Y stage to move the sample. Using the data measured at many points, the three-dimensional distribution were obtained. To estimate the system performance, the electron beam irradiated PMMA was used. The electron beam was irradiated from transmission electron microscope (TEM). The depth of injected electron was controlled using the various metal masks. The measurement results were compared with theoretically calculated values of electron range. (author)

Detailed Characteristics of Radiation Belt Electrons Revealed by CSSWE/REPTile Measurements

Science.gov (United States)

Zhang, K.; Li, X.; Schiller, Q.; Gerhardt, D. T.; Millan, R. M.

2016-12-01

The outer radiation belt electrons are highly dynamic. We study the detailed characteristics of the relativistic electrons in the outer belt using measurements from the Colorado Student Space Weather Experiment (CSSWE) mission, a low Earth orbit Cubesat, which transverses the radiation belt four times in one orbit ( 1.5 hr) and has the advantage of measuring the dynamic activities of the electrons including their rapid precipitations. Among the features of the relativistic electrons, we show the measured electron distribution as a function of geomagnetic activities and local magnetic field strength. Moreover, a specific precipitation band, which happened on 19 Jan 2013, is investigated based on the conjunctive measurement of CSSWE and the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL). In this precipitation band event, the net loss of the 0.58 1.63 MeV electrons (L=3.5 6) is estimated to account for 6.84% of the total electron content.

Atomic physics measurements in an electron Beam Ion Trap

International Nuclear Information System (INIS)

Marrs, R.E.; Beiersdorfer, P.; Bennett, C.

1989-01-01

An electron Beam Ion Trap at Lawrence Livermore National Laboratory is being used to produce and trap very-highly-charged ions (q ≤ 70/+/) for x-ray spectroscopy measurements. Recent measurements of transition energies and electron excitation cross sections for x-ray line emission are summarized. 13 refs., 10 figs

Measurement of Cosmic-Ray TeV Electrons

Science.gov (United States)

Schubnell, Michael; Anderson, T.; Bower, C.; Coutu, S.; Gennaro, J.; Geske, M.; Mueller, D.; Musser, J.; Nutter, S.; Park, N.; Tarle, G.; Wakely, S.

2011-09-01

The Cosmic Ray Electron Synchrotron Telescope (CREST) high-altitude balloon experiment is a pathfinding effort to detect for the first time multi-TeV cosmic-ray electrons. At these energies distant sources will not contribute to the local electron spectrum due to the strong energy losses of the electrons and thus TeV observations will reflect the distribution and abundance of nearby acceleration sites. CREST will detect electrons indirectly by measuring the characteristic synchrotron photons generated in the Earth's magnetic field. The instrument consist of an array of 1024 BaF2 crystals viewed by photomultiplier tubes surrounded by a hermetic scintillator shield. Since the primary electron itself need not traverse the payload, an effective detection area is achieved that is several times the nominal 6.4 m2 instrument. CREST is scheduled to fly in a long duration circumpolar orbit over Antarctica during the 2011-12 season.

Electron drift velocity measurements in liquid krypton-methane mixtures

CERN Document Server

Folegani, M; Magri, M; Piemontese, L

1999-01-01

Electron drift velocities have been measured in liquid krypton, pure and mixed with methane at different concentrations (1-10% in volume) versus electric field strength, and a possible effect of methane on electron lifetime has been investigated. While no effect on lifetime could be detected, since lifetimes were in all cases longer than what measurable, a very large increase in drift velocity (up to a factor 6) has been measured.

Measurement of electron beams profile of pierce type electron source using sensor of used Tv tube

International Nuclear Information System (INIS)

Darsono; Suhartono; Suprapto; Elin Nuraini

2015-01-01

The measurement of an electron beam profile has been performed using electron beam monitor based on method of phosphorescent materials. The main components of the electron beam monitor consists of a fluorescent sensor using a used Tv tube, CCTV camera to record images on a Tv screen, video adapter as interface between CCTV and laptop, and the laptop as a viewer and data processing. Two Pierce-type electron sources diode and triode was measured the shape of electron beam profile in real time. Results of the experiments showed that the triode electron source of Pierce type gave the shape of electron beam profiles better than that of the diode electron source .The anode voltage is not so influential on the beam profile shape. The focused voltage in the triode electron source is so influence to the shape of the electron beam profile, but above 5 kV no great effect. It can be concluded that the electron beam monitor can provide real time observations and drawings shape of the electron beam profile displayed on the used Tv tube glass screen which is the real picture of the shape of the electron beam profile. Triode electron source produces a better electron beam profile than that of the diode electron source. (author)

A device for measuring electron beam characteristics

Directory of Open Access Journals (Sweden)

M. Andreev

2017-01-01

Full Text Available This paper presents a device intended for diagnostics of electron beams and the results obtained with this device. The device comprises a rotating double probe operating in conjunction with an automated probe signal collection and processing system. This provides for measuring and estimating the electron beam characteristics such as radius, current density, power density, convergence angle, and brightness.

Inter-satellite calibration of FengYun 3 medium energy electron fluxes with POES electron measurements

Science.gov (United States)

Zhang, Yang; Ni, Binbin; Xiang, Zheng; Zhang, Xianguo; Zhang, Xiaoxin; Gu, Xudong; Fu, Song; Cao, Xing; Zou, Zhengyang

2018-05-01

We perform an L-shell dependent inter-satellite calibration of FengYun 3 medium energy electron measurements with POES measurements based on rough orbital conjunctions within 5 min × 0.1 L × 0.5 MLT. By comparing electron flux data between the U.S. Polar Orbiting Environmental Satellites (POES) and Chinese sun-synchronous satellites including FY-3B and FY-3C for a whole year of 2014, we attempt to remove less reliable data and evaluate systematic uncertainties associated with the FY-3B and FY-3C datasets, expecting to quantify the inter-satellite calibration factors for the 150-350 keV energy channel at L = 2-7. Compared to the POES data, the FY-3B and FY-3C data generally exhibit a similar trend of electron flux variations but more or less underestimate them within a factor of 5 for the medium electron energy 150-350 keV channel. Good consistency in the flux conjunctions after the inter-calibration procedures gives us certain confidence to generalize our method to calibrate electron flux measurements from various satellite instruments.

Dark field electron holography for strain measurement

Energy Technology Data Exchange (ETDEWEB)

Beche, A., E-mail: armand.beche@fei.com [CEA-Grenoble, INAC/SP2M/LEMMA, F-38054 Grenoble (France); Rouviere, J.L. [CEA-Grenoble, INAC/SP2M/LEMMA, F-38054 Grenoble (France); Barnes, J.P.; Cooper, D. [CEA-LETI, Minatec Campus, F-38054 Grenoble (France)

2011-02-15

Dark field electron holography is a new TEM-based technique for measuring strain with nanometer scale resolution. Here we present the procedure to align a transmission electron microscope and obtain dark field holograms as well as the theoretical background necessary to reconstruct strain maps from holograms. A series of experimental parameters such as biprism voltage, sample thickness, exposure time, tilt angle and choice of diffracted beam are then investigated on a silicon-germanium layer epitaxially embedded in a silicon matrix in order to obtain optimal dark field holograms over a large field of view with good spatial resolution and strain sensitivity. -- Research Highlights: {yields} Step by step explanation of the dark field electron holography technique. {yields} Presentation of the theoretical equations to obtain quantitative strain map. {yields} Description of experimental parameters influencing dark field holography results. {yields} Quantitative strain measurement on a SiGe layer embedded in a silicon matrix.

Interferometer for electron density measurement in exploding wire plasma

International Nuclear Information System (INIS)

Batra, Jigyasa; Jaiswar, Ashutosh; Kaushik, T.C.

2016-12-01

Mach-Zehnder Interferometer (MZI) has been developed for measuring electron density profile in pulsed plasmas. MZI is to be used for characterizing exploding wire plasmas for correlating electron density dynamics with x-rays emission. Experiments have been carried out for probing electron density in pulsed plasmas produced in our laboratory like in spark gap and exploding wire plasmas. These are microsecond phenomenon. Changes in electron density have been registered in interferograms with the help of a streak camera for specific time window. Temporal electron density profiles have been calculated by analyzing temporal fringe shifts in interferograms. This report deals with details of MZI developed in our laboratory along with its theory. Basic introductory details have also been provided for exploding wire plasmas to be probed. Some demonstrative results of electron density measurements in pulsed plasmas of spark gap and single exploding wires have been described. (author)

Non-Local Diffusion of Energetic Electrons during Solar Flares

Science.gov (United States)

Bian, N. H.; Emslie, G.; Kontar, E.

2017-12-01

The transport of the energy contained in suprathermal electrons in solar flares plays a key role in our understanding of many aspects of flare physics, from the spatial distributions of hard X-ray emission and energy deposition in the ambient atmosphere to global energetics. Historically the transport of these particles has been largely treated through a deterministic approach, in which first-order secular energy loss to electrons in the ambient target is treated as the dominant effect, with second-order diffusive terms (in both energy and angle) generally being either treated as a small correction or even neglected. Here, we critically analyze this approach, and we show that spatial diffusion through pitch-angle scattering necessarily plays a very significant role in the transport of electrons. We further show that a satisfactory treatment of the diffusion process requires consideration of non-local effects, so that the electron flux depends not just on the local gradient of the electron distribution function but on the value of this gradient within an extended region encompassing a significant fraction of a mean free path. Our analysis applies generally to pitch-angle scattering by a variety of mechanisms, from Coulomb collisions to turbulent scattering. We further show that the spatial transport of electrons along the magnetic field of a flaring loop can be modeled as a Continuous Time Random Walk with velocity-dependent probability distribution functions of jump sizes and occurrences, both of which can be expressed in terms of the scattering mean free path.

GEOS-2 measurements of cold ions in the magnetosheath

International Nuclear Information System (INIS)

Rodgers, D.J.; Johnstone, A.D.; Sojka, J.J.

1985-01-01

The Suprathermal Plasma Analysers on GEOS-2 are able to make differential energy measurements of plasma particles down to sub-eV energies because the entire sensor package can be biased relative to the spacecraft. When the package is biased negatively with respect to space potential, low energy positive ions are sucked in and are more easily detected against the background. Large fluxes of ions with temperatures of the order of 1 eV or less were consistently detected at space potential when the spacecraft was in the magnetosheath though not when it was in the nearby magnetosphere. This apparent geophysical correlation, suggesting that the ions were part of the magnetosheath ion population, was contradicted by the fact that the ions showed no signs of the large drift velocity associated with the electric field in the magnetosheath. It is concluded, after further investigation, that the observed ions were probably sputtered as neutrals from the spacecraft surface by the impact of solar wind ions and subsequently ionized by sunlight or electron impact. The effect of sputtering by solar wind ions has not been previously observed, although it could have consequences for the long-term stability of spacecraft surfaces. (author)

Cluster observations of particle acceleration up to supra-thermal energies in the cusp region related to low-frequency wave activity – possible implications for the substorm initiation process

Directory of Open Access Journals (Sweden)

T. A. Fritz

2008-03-01

Full Text Available The purpose of our study is to investigate the way particles are accelerated up to supra-thermal energies in the cusp diamagnetic cavities. For this reason we have examined a number of Cluster cusp crossings, originally identified by Zhang et al. (2005, for the years 2001 and 2002 using data from RAPID, STAFF, EFW, CIS, PEACE, and FGM experiments. In the present study we focus on two particular cusp crossings on 25 March 2002 and on 10 April 2002 which demonstrate in a clear way the general characteristics of the events in our survey. Both events exhibit very sharp spatial boundaries seen both in CNO (primarily single-charged oxygen of ionospheric origin based on CIS observations and H+ flux increases within the RAPID energy range with the magnetic field intensity being anti-correlated. Unlike the first event, the second one shows also a moderate electron flux increase. The fact that the duskward electric field Ey has relatively low values <5 mV/m while the local wave activity is very intense provides a strong indication that particle energization is caused primarily by wave-particle interactions. The wave power spectra and propagation parameters during these cusp events are examined in detail. It is concluded that the high ion fluxes and at the same time the presence or absence of any sign of energization in the electrons clearly shows that the particle acceleration depends on the wave power near the local particle gyrofrequency and on the persistence of the wave-particle interaction process before particles escape from cusp region. Furthermore, the continuous existence of energetic O+ ions suggests that energetic O+ populations are of spatial nature at least for the eight events that we have studied so far.

A device for electron gun emittance measurement

International Nuclear Information System (INIS)

Aune, B.; Corveller, P.; Jablonka, M.; Joly, J.M.

1985-05-01

In order to improve the final emittance of the beam delivered by the ALS electron linac a new gun is going to be installed. To measure its emittance and evaluate the contribution of different factors to emittance growth we have developed an emittance measurement device. We describe the experimental and mathematical procedure we have followed, and give some results of measurements

Rocket measurements of electron density irregularities during MAC/SINE

Science.gov (United States)

Ulwick, J. C.

1989-01-01

Four Super Arcas rockets were launched at the Andoya Rocket Range, Norway, as part of the MAC/SINE campaign to measure electron density irregularities with high spatial resolution in the cold summer polar mesosphere. They were launched as part of two salvos: the turbulent/gravity wave salvo (3 rockets) and the EISCAT/SOUSY radar salvo (one rocket). In both salvos meteorological rockets, measuring temperature and winds, were also launched and the SOUSY radar, located near the launch site, measured mesospheric turbulence. Electron density irregularities and strong gradients were measured by the rocket probes in the region of most intense backscatter observed by the radar. The electron density profiles (8 to 4 on ascent and 4 on descent) show very different characteristics in the peak scattering region and show marked spatial and temporal variability. These data are intercompared and discussed.

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

Science.gov (United States)

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

2012-12-01

At the fusion experiment JET, a Michelson interferometer is used to measure the spectrum of the electron cyclotron emission in the spectral range 70-500 GHz. The interferometer is absolutely calibrated using the hot/cold technique and, in consequence, the spatial profile of the plasma electron temperature is determined from the measurements. The current state of the interferometer hardware, the calibration setup, and the analysis technique for calibration and plasma operation are described. A new, full-system, absolute calibration employing continuous data acquisition has been performed recently and the calibration method and results are presented. The noise level in the measurement is very low and as a result the electron cyclotron emission spectrum and thus the spatial profile of the electron temperature are determined to within ±5% and in the most relevant region to within ±2%. The new calibration shows that the absolute response of the system has decreased by about 15% compared to that measured previously and possible reasons for this change are presented. Temperature profiles measured with the Michelson interferometer are compared with profiles measured independently using Thomson scattering diagnostics, which have also been recently refurbished and recalibrated, and agreement within experimental uncertainties is obtained.

Measuring the electron-ion ring parameters by bremsstrahlung

International Nuclear Information System (INIS)

Inkin, V.D.; Mozelev, A.A.; Sarantsev, V.P.

1982-01-01

A system is described for measuring the number of electrons and ions in the electron-ion rings of a collective heavy ion accelerator. The system operation is based on detecting gamma quanta of bremsstrahlung following the ring electron interaction with the nuclei of neutral atoms and ions at different stages of filling the ring with ions. The radiation detector is a scintillation block - a photomultiplier operating for counting with NaI(Tl) crystal sized 30x30 mm and ensuring the detection efficiency close to unity. The system apparatus is made in the CAMAC standard and rems on-line with the TRA/i miniature computer. The block-diagrams of the system and algorithm of data processing are presented. A conclusion is drawn that the results of measuring the ring parameters with the use of the diagnostics system described are in good agreement within the range of measuring errors with those obtained by means of the diagnostics system employing synchrotron radiation and induction sensors

Temperature measurement systems in wearable electronics

Science.gov (United States)

Walczak, S.; Gołebiowski, J.

2014-08-01

The aim of this paper is to present the concept of temperature measurement system, adapted to wearable electronics applications. Temperature is one of the most commonly monitored factor in smart textiles, especially in sportswear, medical and rescue products. Depending on the application, measured temperature could be used as an initial value of alert, heating, lifesaving or analysis system. The concept of the temperature measurement multi-point system, which consists of flexible screen-printed resistive sensors, placed on the T-shirt connected with the central unit and the power supply is elaborated in the paper.

Emittance measurement for high-brightness electron guns

International Nuclear Information System (INIS)

Kobayashi, H.; Kurihara, T.; Sato, I.; Asami, A.; Yamazaki, Y.; Otani, S.; Ishizawa, Y.

1992-01-01

An emittance measurement system based on a high-precision pepper-pot technique has been developed for electron guns with low emittance of around πmm-mrad. Electron guns with a 1 mmφ cathode, the material of which is impregnated tungsten or single-crystal lanthanum hexaboride (La 1-x Ce x )B 6 , have been developed. The performance has been evaluated by putting stress on cathode roughness, which gives rise to an angular divergence, according to the precise emittance measurement system. A new type of cathode holder, which is a modified version of the so called Vogel type, was developed and the beam uniformity has been improved. (Author) 5 figs., tab., 9 refs

Electric Field Measurements At The Magnetopause

Science.gov (United States)

Lindqvist, P.-A.; Dunlop, M.

The quasi-thermal noise (QTN) is due to the thermal motions of the particles, which produce electrostatic fluctuations. This noise is detected by any sensitive receiver at the ports of an electric antenna immersed in a plasma and can be used to measure in-situ the plasma density, temperature and bulk velocity. The basic reason is that this noise can be formally calculated as a function of both the particle velocity distribu- tions and the antenna geometry. So, conversely, the "spectroscopy" of this noise re- veals the local plasma properties. This method is routinely used on various spacecraft (Ulysses, Wind) in the solar wind or in planetary magnetospheres/ionospheres (Image at Earth, Cassini at Venus, Earth and soon at Saturn). This method has the advantage of being relatively immune to spacecraft potential and photoelectrons pertubations, since it senses a large plasma volume. It provides an accurate measurement of the electron density (a few %) because it is based on the detection of the strong signal peak near the local plasma frequency (which is close to a resonance for electrostatic waves). We will show that QTN may be as well adapted to measure 1) magnetized (anisotropic) plasmas (and deduce the magnetic field strength), 2) suprathermal or non-thermal component (as for example a kappa distribution), and 3) a wide range of core temperature, i.e from ~10 eV, as in the solar wind, to rather low temperatures (tron density and temperature for comparison with our models of Mercury/solar wind interaction.

Response of Saturn's ionosphere to solar radiation: Testing parameterizations for thermal electron heating and secondary ionization processes

Science.gov (United States)

Moore, Luke; Galand, Marina; Mueller-Wodarg, Ingo; Mendillo, Michael

2009-12-01

We evaluate the effectiveness of two parameterizations in Saturn's ionosphere over a range of solar fluxes, seasons, and latitudes. First, the parameterization of the thermal electron heating rate, Q* e, introduced in [Moore, L., Galand, M., Mueller-Wodarg, I., Yelle, R.V., Mendillo, M., 2008. Plasma temperatures in Saturn's ionosphere. J. Geophys. Res. 113, A10306. doi:10.1029/2008JA013373.] for one specific set of conditions, is found to produce ion and electron temperatures that agree with self-consistent suprathermal electron calculations to within 2% on average under all conditions considered. Next, we develop a new parameterization of the secondary ion production rate at Saturn based on the calculations of [Galand, M., Moore, L., Mueller-Wodarg, I., Mendillo, M., 2009. Modeling the photoelectron secondary ionization process at Saturn. accepted. J. Geophys. Res.]; it is found to be accurate to within 4% on average. The demonstrated effectiveness of these two parameterizations over a wide range of input conditions makes them good candidates for inclusion in 3D Saturn thermosphere-ionosphere general circulation models (TIGCMs).

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

Electron beam interaction with space plasmas

International Nuclear Information System (INIS)

Krafft, C.; Volokitin, A.S.

1999-01-01

Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification. Recently, theoretical studies of the nonlinear evolution of a thin monoenergetic electron beam injected in a magnetized plasma and interacting with a whistler wave packet have led to new results. The influence of an effective dissipation process connected with whistler wave field leakage out of the beam volume to infinity (that is, effective radiation outside the beam) on the nonlinear evolution of beam electrons distribution in phase space has been studied under conditions relevant to active space experiments and related laboratory modelling. The beam-waves system's evolution reveals the formation of stable nonlinear structures continuously decelerated due to the effective friction imposed by the strongly dissipated waves. The nonlinear interaction between the electron bunches and the wave packet are discussed in terms of dynamic energy exchange, particle trapping, slowing down of the beam, wave dissipation and quasi-linear diffusion. (author)

Resistance and sheet resistance measurements using electron beam induced current

International Nuclear Information System (INIS)

Czerwinski, A.; Pluska, M.; Ratajczak, J.; Szerling, A.; KaPtcki, J.

2006-01-01

A method for measurement of spatially uniform or nonuniform resistance in layers and strips, based on electron beam induced current (EBIC) technique, is described. High electron beam currents are used so that the overall resistance of the measurement circuit affects the EBIC signal. During the evaluation, the electron beam is scanned along the measured object, whose load resistance varies with the distance. The variation is compensated by an adjustable resistance within an external circuit. The method has been experimentally deployed for sheet resistance determination of buried regions of lateral confinements in semiconductor laser heterostructures manufactured by molecular beam epitaxy

Electron Bunch Length Measurement for LCLS at SLAC

International Nuclear Information System (INIS)

Zelazny, M.; Allison, S.; Chevtsov, Sergei; Emma, P.; Kotturi, K.d.; Loos, H.; Peng, S.; Rogind, D.; Straumann, T.

2007-01-01

At Stanford Linear Accelerator Center (SLAC) a Bunch Length Measurement system has been developed to measure the length of the electron bunch for its new Linac Coherent Light Source (LCLS). This destructive measurement uses a transverse-mounted RF deflector (TCAV) to vertically streak the electron beam and an image taken with an insertable screen and a camera. The device control software was implemented with the Experimental Physics and Industrial Control System (EPICS) toolkit. The analysis software was implemented in Matlab(trademark) using the EPICS/Channel Access Interface for Scilab(trademark) and Matlab(trademark) (labCA). This architecture allowed engineers and physicists to develop and integrate their control and analysis without duplication of effort

Hard x-ray measurements of the hot-electron rings in EBT-S

International Nuclear Information System (INIS)

Hillis, D.L.

1982-06-01

A thorough understanding of the hot electron rings in ELMO Bumpy Torus-Scale (EBT-S) is essential to the bumpy torus concept of plasma production, since the rings provide bulk plasma stability. The hot electrons are produced via electron cyclotron resonant heating using a 28-GHz cw gyrotron, which has operated up to power levels of 200 kW. The parameters of the energetic electron rings are studied via hard x-ray measurement techniques and with diamagnetic pickup coils. The hard x-ray measurements have used collimated NaI(Tl) detectors to determine the electron temperature T/sub e/ and electron density n/sub e/ for the hot electron annulus. Typical values of T/sub e/ are 400 to 500 keV and of n/sub e/ 2 to 5 x 10 11 cm -3 . The total stored energy of a single energetic electron ring as measured by diamagnetic pickup loops approaches approx. 40 J and is in good agreement with that deduced from hard x-ray measurements. By combining the experimental measurements from hard x-rays and the diamagnetic loops, an estimate can be obtained for the volume of a single hot electron ring. The ring volume is determined to be approx. 2.2 litres, and this volume remains approximately constant over the T-mode operating regime. Finally, the power in the electrons scattered out of the ring is measured indirectly by measuring the x-ray radiation produced when those electrons strike the chamber walls. The variation of this radiation with increasing microwave power levels is found to be consistent with classical scattering estimates

Introduction to electronic relaxation in solids: mechanisms and measuring techniques

International Nuclear Information System (INIS)

Bonville, P.

1983-01-01

The fluctuations of electronic magnetic moments in solids may be investigated by several techniques, either electronic or nuclear. This paper is an introduction of the most frequently encountered paramagnetic relaxation mechanisms (phonons, conduction electrons, exchange or dipolar interactions) in condensed matter, and to the different techniques used for measuring relaxation frequencies: electronic paramagnetic resonance, nuclear magnetic resonance, Moessbauer spectroscopy, inelastic neutron scattering, measurement of longitudinal ac susceptibility and γ-γ perturbed angular correlations. We mainly focus our attention on individual ionic fluctuation spectra, the majority of the experimental work refered to concerning rare earth systems [fr

Real-time measurement and monitoring of absorbed dose for electron beams

Science.gov (United States)

Korenev, Sergey; Korenev, Ivan; Rumega, Stanislav; Grossman, Leon

2004-09-01

The real-time method and system for measurement and monitoring of absorbed dose for industrial and research electron accelerators is considered in the report. The system was created on the basis of beam parameters method. The main concept of this method consists in the measurement of dissipated kinetic energy of electrons in the irradiated product, determination of number of electrons and mass of irradiated product in the same cell by following calculation of absorbed dose in the cell. The manual and automation systems for dose measurements are described. The systems are acceptable for all types of electron accelerators.

Real-time measurement and monitoring of absorbed dose for electron beams

Energy Technology Data Exchange (ETDEWEB)

Korenev, Sergey E-mail: sergey_korenev@steris.com; Korenev, Ivan; Rumega, Stanislav; Grossman, Leon

2004-10-01

The real-time method and system for measurement and monitoring of absorbed dose for industrial and research electron accelerators is considered in the report. The system was created on the basis of beam parameters method. The main concept of this method consists in the measurement of dissipated kinetic energy of electrons in the irradiated product, determination of number of electrons and mass of irradiated product in the same cell by following calculation of absorbed dose in the cell. The manual and automation systems for dose measurements are described. The systems are acceptable for all types of electron accelerators.

Real-time measurement and monitoring of absorbed dose for electron beams

International Nuclear Information System (INIS)

Korenev, Sergey; Korenev, Ivan; Rumega, Stanislav; Grossman, Leon

2004-01-01

The real-time method and system for measurement and monitoring of absorbed dose for industrial and research electron accelerators is considered in the report. The system was created on the basis of beam parameters method. The main concept of this method consists in the measurement of dissipated kinetic energy of electrons in the irradiated product, determination of number of electrons and mass of irradiated product in the same cell by following calculation of absorbed dose in the cell. The manual and automation systems for dose measurements are described. The systems are acceptable for all types of electron accelerators

Alpha and conversion electron spectroscopy of 238,239Pu and 241Am and alpha-conversion electron coincidence measurements

Energy Technology Data Exchange (ETDEWEB)

Dion, Michael P.; Miller, Brian W.; Warren, Glen A.

2016-09-01

A technique to determine the isotopics of a mixed actinide sample has been proposed by measuring the coincidence of the alpha particle during radioactive decay with the conversion electron (or Auger) emitted during the relaxation of the daughter isotope. This presents a unique signature to allow the deconvolution of isotopes that possess overlapping alpha particle energy. The work presented here are results of conversion electron spectroscopy of 241Am, 238Pu and 239Pu using a dual-stage peltier-cooled 25 mm2 silicon drift detector. A passivated ion implanted planar silicon detector provided measurements of alpha spectroscopy. The conversion electron spectra were evaluated from 20–55 keV based on fits to the dominant conversion electron emissions, which allowed the relative conversion electron emission intensities to be determined. These measurements provide crucial singles spectral information to aid in the coincident measurement approach.

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...

Measurement of the electron quenching rate in an electron beam pumped KrF* laser

International Nuclear Information System (INIS)

Nishioka, Hajime; Kurashima, Toshio; Kuranishi, Hideaki; Ueda, Kenichi; Takuma, Hiroshi; Sasaki, Akira; Kasuya, Koichi.

1988-01-01

The electron quenching rate of KrF * in an electron beam pumped laser has been studied by accurately measuring the saturation intensity in a mixture of Ar/Kr/F 2 = 94/6/0.284. The input intensity of the measurements was widely varied from 100 W cm -2 (small signal region) to 100 MW cm -2 (absorption dominant region) in order to separate laser parameters which are small signal gain coefficient, absorption coefficient, and saturation intensity from the measured net gain coefficients. The gas pressure and the pump rate were varied in the range of 0.5 to 2.5 atm and 0.3 to 1.4 MW cm -3 , respectively. The electron quenching rate constant of 4.5 x 10 -7 cm 3 s -1 was obtained from the pressure and the pump rate dependence of the KrF * saturation intensity with the temperature dependence of the rate gas 3-body quenching rate as a function of gas temperature to the -3rd power. The small signal gain coefficients calculated with the determined quenching rate constants shows excellent agreement with the measurements. (author)

Photoion Auger-electron coincidence measurements near threshold

International Nuclear Information System (INIS)

Levin, J.C.; Biedermann, C.; Keller, N.; Liljeby, L.; Short, R.T.; Sellin, I.A.; Lindle, D.W.

1990-01-01

The vacancy cascade which fills an atomic inner-shell hole is a complex process which can proceed by a variety of paths, often resulting in a broad distribution of photoion charge states. We have measured simplified argon photoion charge distributions by requiring a coincidence with a K-LL or K-LM Auger electron, following K excitation with synchrotron radiation, as a function of photon energy, and report here in detail the argon charge distributions coincident with K-L 1 L 23 Auger electrons. The distributions exhibit a much more pronounced photon-energy dependence than do the more complicated non-coincident spectra. Resonant excitation of the K electron to np levels, shakeoff of these np electrons by subsequent decay processes, double-Auger decay, and recapture of the K photoelectron through postcollision interaction occur with significant probability. 17 refs

TeV electron measurement with CREST experiment

Science.gov (United States)

Park, Nahee; Anderson, T.; Bower, C.; Coutu, S.; Gennaro, J.; Geske, M.; Muller, D.; Musser, J.; Nutter, S.

CREST, the Cosmic Ray Electron Synchrotron Telescope is a balloon-borne experiment de-signed to measure the spectrum of multi-TeV electrons by the detection of the x-ray synchrotron photons generated in the magnetic field of the Earth. Electrons in the TeV range are expected to reflect the properties of local sources because fluxes from remote locations are suppressed by radiative losses during propagation. Since CREST needs to intersect only a portion of the kilometers-long trail of photons generated by the high-energy electron, the method yields a larger effective area than the physical size of the detector, boosting detection areas. The in-strument is composed of an array of 1024 BaF2 crystals and a set of scintillating veto counters. A long duration balloon flight in Antarctica is currently planned for the 2010-11 season.

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

International Nuclear Information System (INIS)

Bauer, H.E.; Seiler, H.

1988-01-01

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

Miniature electron bombardment evaporation source: evaporation rate measurement

International Nuclear Information System (INIS)

Nehasil, V.; Masek, K.; Matolin, V.; Moreau, O.

1997-01-01

Miniature electron beam evaporation sources which operate on the principle of vaporization of source material, in the form of a tip, by electron bombardment are produced by several companies specialized in UHV equipment. These sources are used primarily for materials that are normally difficult to deposit due to their high evaporation temperature. They are appropriate for special applications such as heteroepitaxial thin film growth requiring a very low and well controlled deposition rate. A simple and easily applicable method of evaporation rate control is proposed. The method is based on the measurement of ion current produced by electron bombardment of evaporated atoms. The absolute evaporation flux values were measured by means of the Bayard-Alpert ion gauge, which enabled the ion current vs evaporation flux calibration curves to be plotted. (author). 1 tab., 4 figs., 6 refs

Wave and plasma measurements and GPS diagnostics of the main ionospheric trough as a hybrid method used for Space Weather purposes

Directory of Open Access Journals (Sweden)

H. Rothkaehl

2008-02-01

Full Text Available The region of the main ionospheric trough is a unique region of the ionosphere, where different types of waves and instabilities can be generated. This region of the ionosphere acts like a lens, focusing a variety of indicators from the equator of plasmapause and local ionospheric plasma. This paper reports the results of monitoring the mid-latitude trough structure, dynamics and wave activity. For these purposes, the data gathered by the currently-operating DEMETER satellite and past diagnostics located on IK-19, Apex, and MAGION-3 spacecraft, as well as TEC measurements were used. A global-time varying picture of the ionospheric trough was reconstructed using the sequence of wave spectra registered and plasma measurements in the top-side ionosphere. The authors present the wave activity from ULF frequency band to the HF frequency detected inside the trough region and discuss its properties during geomagnetic disturbances. It is thought that broadband emissions are correlated with low frequency radiation, which is excited by the wave-particle interaction in the equatorial plasmapause and moves to the ionosphere along the geomagnetic field line. In the ionosphere, the suprathermal electrons can interact with these electrostatic waves and excite electron acoustic waves or HF longitudinal plasma waves.

Furthermore, the electron density trough can provide useful data on the magnetosphere ionosphere dynamics and morphology and, in consequence, can be used for Space Weather purposes.

Weak measurement from the electron displacement current: new path for applications

International Nuclear Information System (INIS)

Marian, D; Colomés, E; Oriols, X; Zanghì, N

2015-01-01

The interest on weak measurements is rapidly growing during the last years as a unique tool to better understand and predict new quantum phenomena. Up to now many theoretical and experimental weak-measurement techniques deal with (relativistic) photons or cold atoms, but there is much less investigation on (non-relativistic) electrons in up-to-date electronics technologies. We propose a way to perform weak measurements in nanoelectronic devices through the measurement of the total current (particle plus displacement component) in such devices. We study the interaction between an electron in the active region of a electron device with a metal surface working as a sensing electrode by means of the (Bohmian) conditional wave function. We perform numerical (Monte Carlo) simulations to reconstruct the Bohmian trajectories in the iconic double slit experiment. This work opens new paths for understanding the quantum properties of an electronic system as well as for exploring new quantum engineering applications in solid state physics. (paper)

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.

Measuring up: Implementing a dental quality measure in the electronic health record context.

Science.gov (United States)

Bhardwaj, Aarti; Ramoni, Rachel; Kalenderian, Elsbeth; Neumann, Ana; Hebballi, Nutan B; White, Joel M; McClellan, Lyle; Walji, Muhammad F

2016-01-01

Quality improvement requires using quality measures that can be implemented in a valid manner. Using guidelines set forth by the Meaningful Use portion of the Health Information Technology for Economic and Clinical Health Act, the authors assessed the feasibility and performance of an automated electronic Meaningful Use dental clinical quality measure to determine the percentage of children who received fluoride varnish. The authors defined how to implement the automated measure queries in a dental electronic health record. Within records identified through automated query, the authors manually reviewed a subsample to assess the performance of the query. The automated query results revealed that 71.0% of patients had fluoride varnish compared with the manual chart review results that indicated 77.6% of patients had fluoride varnish. The automated quality measure performance results indicated 90.5% sensitivity, 90.8% specificity, 96.9% positive predictive value, and 75.2% negative predictive value. The authors' findings support the feasibility of using automated dental quality measure queries in the context of sufficient structured data. Information noted only in free text rather than in structured data would require using natural language processing approaches to effectively query electronic health records. To participate in self-directed quality improvement, dental clinicians must embrace the accountability era. Commitment to quality will require enhanced documentation to support near-term automated calculation of quality measures. Copyright © 2016 American Dental Association. Published by Elsevier Inc. All rights reserved.

Measurements of the Electron Reconstruction and Identification Efficiencies in ATLAS

CERN Document Server

Sommer, P; The ATLAS collaboration

2014-01-01

Isolated, high-energy electrons constitute a very clean signature at hadron collider experiments. As the final states of many Standard Model processes, as well as physics beyond the Standard Model, analyses at the ATLAS experiment heavily rely on electrons. A precise knowledge of the efficiency to correctly reconstruct and identify these electrons is thus important. In this contribution the measurement of these efficiencies is described. It is performed with a tag-and-probe method using $Z$ and $J/\\psi$ decays to electrons in $20.3\\,\\mathrm{fb}^{-1}$ of $pp$ collisions recorded in 2012 at $\\sqrt{s}=8$ TeV. The combination of the measurements results in identification efficiencies determined with an accuracy of a few per mil for electrons with a transverse energy of $E_{\\mathrm{T}}>30$ GeV.

Measurement of Electron Cloud Effects in SPS

CERN Document Server

Jiménez, J M

2004-01-01

The electron cloud is not a new phenomenon, indeed, it was observed already in other machines like the proton storage rings in BINP Novosibirsk or in the Intersecting Storage Ring (ISR) at CERN. Inside an accelerator beam pipe, the electrons can collectively and coherently interact with the beam potential and degrade the performance of the accelerators operating with intense positively charged bunched beams. In the LHC, electron multipacting is expected to take place in the cold and warm beam pipe due to the presence of the high intensities bunched beams, creating an electron cloud. The additional heat load induced by the electron cloud onto the LHC beam screens of the cold magnets of the LHC bending sections (the arcs represent ~21 km in length) was, and is still, considered as one of the main possible limitation of LHC performances. Since 1997 and in parallel with the SPS studies with LHC-type beams, measurements in other machines or in the laboratory have been made to provide the input parameters required ...

Absolute beam-charge measurement for single-bunch electron beams

International Nuclear Information System (INIS)

Suwada, Tsuyoshi; Ohsawa, Satoshi; Furukawa, Kazuro; Akasaka, Nobumasa

2000-01-01

The absolute beam charge of a single-bunch electron beam with a pulse width of 10 ps and that of a short-pulsed electron beam with a pulse width of 1 ns were measured with a Faraday cup in a beam test for the KEK B-Factory (KEKB) injector linac. It is strongly desired to obtain a precise beam-injection rate to the KEKB rings, and to estimate the amount of beam loss. A wall-current monitor was also recalibrated within an error of ±2%. This report describes the new results for an absolute beam-charge measurement for single-bunch and short-pulsed electron beams, and recalibration of the wall-current monitors in detail. (author)

Measurement of microwave radiation from electron beam in the atmosphere

Energy Technology Data Exchange (ETDEWEB)

Ohta, I.S.; Akimune, H. [Faculty of Science and Engineering, Konan University, Kobe 658-8501 (Japan); Fukushima, M.; Ikeda, D. [Institute of Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Inome, Y. [Faculty of Science and Engineering, Konan University, Kobe 658-8501 (Japan); Matthews, J.N. [University of Utah, Salt Lake City, UT 4112-0830 (United States); Ogio, S. [Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Sagawa, H. [Institute of Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Sako, T. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Shibata, T. [High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan); Yamamoto, T., E-mail: tokonatu@konan-u.ac.jp [Faculty of Science and Engineering, Konan University, Kobe 658-8501 (Japan)

2016-02-21

We report the use of an electron light source (ELS) located at the Telescope Array Observatory in Utah, USA, to measure the isotropic microwave radiation from air showers. To simulate extensive air showers, the ELS emits an electron beam into the atmosphere and a parabola antenna system for the satellite communication is used to measure the microwave radiation from the electron beam. Based on this measurement, an upper limit on the intensity of a 12.5 GHz microwave radiation at 0.5 m from a 10{sup 18} eV air shower was estimated to be 3.96×10{sup −16} W m{sup −2} Hz{sup −1} with a 95% confidence level.

Electron density measurements during ion beam transport on Gamble II

International Nuclear Information System (INIS)

Weber, B.V.; Hinshelwood, D.D.; Neri, J.M.; Ottinger, P.F.; Rose, D.V.; Stephanakis, S.J.; Young, F.C.

1999-01-01

High-sensitivity laser interferometry was used to measure the electron density created when an intense proton beam (100 kA, 1 MeV, 50 ns) from the Gamble II generator was transported through low-pressure gas as part of a project investigating Self-Pinched Transport (SPT) of intense ion beams. This measurement is non-perturbing and sufficiently quantitative to allow benchmarking of codes (particularly IPROP) used to model beam-gas interaction and ion-beam transport. Very high phase sensitivity is required for this measurement. For example, a 100-kA, 1-MeV, 10-cm-radius proton beam with uniform current density has a line-integrated proton density equal to n b L = 3 x 10 13 cm -2 . An equal electron line-density, n e L = n b L, (expected for transport in vacuum) will be detected as a phase shift of the 1.064 microm laser beam of only 0.05degree, or an optical path change of 1.4 x 10 -4 waves (about the size of a hydrogen atom). The time-history of the line-integrated electron density, measured across a diameter of the transport chamber at 43 cm from the input aperture, starts with the proton arrival time and decays differently depending on the gas pressure. The gas conditions included vacuum (10 -4 Torr air), 30 to 220 mTorr He, and 1 Torr air. The measured densities vary by three orders of magnitude, from 10 13 to 10 16 cm -2 for the range of gas pressures investigated. In vacuum, the measured electron densities indicate only co-moving electrons (n e L approximately n b L). In He, when the gas pressure is sufficient for ionization by beam particles and SPT is observed, n e L increases to about 10 n b L. At even higher pressures where electrons contribute to ionization, even higher electron densities are observed with an ionization fraction of about 2%. The diagnostic technique as used on the SPT experiment will be described and a summary of the results will be given. The measurements are in reasonable agreement with theoretical predictions from the IPROP code

Electron density measurements in the TRIAM-1 tokamak

Energy Technology Data Exchange (ETDEWEB)

Mitarai, O; Nakashima, H; Nakamura, K; Hiraki, N; Toi, K [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1980-02-01

Electron density measurements in the TRIAM-1 tokamak are carried out by a 140 GHz microwave interferometer. To follow rapid density variations, a high-speed direct-reading type interferometer is constructed. The density of (1 - 20) x 10/sup 13/ cm/sup -3/ is measured.

Electron density measurements in the TRIAM-1 tokamak

International Nuclear Information System (INIS)

Mitarai, Osamu; Nakashima, Hisatoshi; Nakamura, Kazuo; Hiraki, Naoji; Toi, Kazuo

1980-01-01

Electron density measurements in the TRIAM-1 tokamak are carried out by a 140 GHz microwave interferometer. To follow rapid density variations, a high-speed direct-reading type interferometer is constructed. The density of (1 - 20) x 10 13 cm -3 is measured. (author)

Scientific Considerations for Future Spectroscopic Measurements from Space of Activity on the Sun

Science.gov (United States)

Holman, Gordon D.

2016-01-01

High-resolution UV and X-ray spectroscopy are important to understanding the origin and evolution of magnetic energy release in the solar atmosphere, as well as the subsequent evolution of heated plasma and accelerated particles. Electromagnetic radiation is observed from plasma heated to temperatures ranging from about 10 k K to above 10 MK, from accelerated electrons emitting photons primarily at X-ray energies, and from ions emitting in gamma rays. These observations require space-based instruments sensitive to emissions at wavelengths shorter than the near UV. This article reviews some recent observations with emphasis on solar eruptive events, the models that describe them, and the measurements they indicate are needed for substantial progress in the future. Specific examples are discussed demonstrating that imaging spectroscopy with a cadence of seconds or better is needed to follow, understand, and predict the evolution of solar activity. Critical to substantial progress is the combination of a judicious choice of UV, EUV, and soft X-ray imaging spectroscopy sensitive to the evolution of this thermal plasma combined with hard X-ray imaging spectroscopy sensitive to suprathermal electrons. The major challenge will be to conceive instruments that, within the bounds of possible technologies and funding, have the flexibility and field of view to obtain spectroscopic observations where and when events occur while providing an optimum balance of dynamic range, spectral resolution and range, and spatial resolution.

Tests of an electron monitor for routine quality control measurements of electron energies

International Nuclear Information System (INIS)

Ramsay, E.B.; Reinstein, L.E.; Meek, A.G.

1991-01-01

The depth dose for electrons is sensitive to energy and the AAPM Task Group 24 has recommended that tests be performed at monthly intervals to assure electron beam energy constancy by verifying the depth for the 80% dose to within ±3 mm. Typically, this is accomplished by using a two-depth dose ratio technique. Recently, a new device, the Geske monitor, has been introduced that is designed for verifying energy constancy in a single reading. The monitor consists of nine parallel plate detectors that alternate with 5-mm-thick absorbers made of an aluminum alloy. An evaluation of the clinical usefulness of this monitor for the electron beams available on a Varian Clinac 20 has been undertaken with respect to energy discrimination. Beam energy changes of 3 mm of the 80% dose give rise to measurable output changes ranging from 1.7% for 20-MeV electron beams to 15% for 6-MeV electron beams

Measurements of the electron cloud in the APS storage ring

International Nuclear Information System (INIS)

Harkey, K. C.

1999-01-01

Synchrotron radiation interacting with the vacuum chamber walls in a storage ring produce photoelectrons that can be accelerated by the beam, acquiring sufficient energy to produce secondary electrons in collisions with the walls. If the secondary-electron yield (SEY) coefficient of the wall material is greater than one, as is the case with the aluminum chambers in the Advanced Photon Source (APS) storage ring, a runaway condition can develop. As the electron cloud builds up along a train of stored positron or electron bunches, the possibility exists that a transverse perturbation of the head bunch will be communicated to trailing bunches due to interaction with the cloud. In order to characterize the electron cloud, a special vacuum chamber was built and inserted into the ring. The chamber contains 10 rudimentary electron-energy analyzers, as well as three targets coated with different materials. Measurements show that the intensity and electron energy distribution are highly dependent on the temporal spacing between adjacent bunches and the amount of current contained in each bunch. Furthermore, measurements using the different targets are consistent with what would be expected based on the SEY of the coatings. Data for both positron and electron beams are presented

Measurement of eDsub(L)/μ of electrons in liquid xenon

International Nuclear Information System (INIS)

Doke, T.; Suzuki, S.; Shibamura, E.; Masuda, K.

1983-01-01

A new method for measuring the spread of electron swarm drifting under uniform electric field in liquid xenon is proposed. This is made by observing the width of scintillation pulse produced by drifting electrons in the vicinity of a thin center wire of a proportional scintillation counter, put in the end part of the electron drift space. From the spread of electron swarm and its drift time, the ratio of longitudinal diffusion coefficient to mobility epsilon sub(L) = eDsub(L)/μ for electrons in liquid xenon is directly obtained. epsilon sub(L) of electron swarms under the various electric fields have been measured and compared with epsilon sub(T) = eDsub(T)/μ previously obtained under the same electric fields. (Authors)

Band rejection filter for measurement of electron cyclotron emission during electron cyclotron heating

International Nuclear Information System (INIS)

Iwase, Makoto; Ohkubo, Kunizo; Kubo, Shin; Idei, Hiroshi.

1996-05-01

For the measurement of electron cyclotron emission from the high temperature plasma, a band rejection filter in the range of 40-60 GHz is designed to reject the 53.2 GHz signal with large amplitude from the gyrotron for the purpose of plasma electron heating. The filter developed with ten sets of three quarters-wavelength coupled by TE 111 mode of tunable resonant cavity has rejection of 50 dB and 3 dB bandwidth of 500 MHz. The modified model of Tschebysheff type for the prediction of rejection is proposed. It is confirmed that the measured rejection as a function of frequency agrees well with the experimental results for small coupling hole, and also clarified that the rejection ratio increases for the large coupling hole. (author)

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)

Energetic electron measurements in the edge of a reversed-field pinch

International Nuclear Information System (INIS)

Ingraham, J.C.; Ellis, R.F.; Downing, J.N.; Munson, C.P.; Weber, P.G.; Wurden, G.A.

1990-01-01

The edge plasma of the ZT-40M [Fusion Technol. 8, 1571 (1985)] reversed-field pinch has been studied using a combination of three different plasma probes: a double-swept Langmuir probe, an electrostatic energy analyzer, and a calorimeter--Langmuir probe. The edge plasma has been measured both with and without a movable graphite tile limiter present nearby in the plasma. Without a limiter a fast nonthermal tail of electrons (T congruent 350 eV) is detected in the edge plasma with nearly unidirectional flow along B and having a density between 2% and 10% of the cold edge plasma (T congruent 20 eV). The toroidal sense of this fast electron flow is against the force of the applied electric field. A large power flux along B is measured flowing in the same direction as the fast electrons and is apparently carried by the fast electrons. With the limiter present the fast electrons are still detected in the plasma, but are strongly attenuated in the shadow of the limiter. The measured scrape-off lengths for both the fast electrons and the cold plasma indicate cross-field transport at the rate of, or less than, Bohm diffusion. Estimates indicate that the fast electrons could carry the reversed-field pinch current density at the edge and, from the measured transverse diffusion rates, could also account for the electron energy loss channel in ZT-40 M. The long mean-free-path kinetic nature of these fast electrons suggests that a kinetic process, rather than a magnetohydrodynamic process that is based upon a local Ohm's law formulation, is responsible for their generation

Measurement of the electron quenching rate in an electron beam pumped KrF/sup */ laser

Energy Technology Data Exchange (ETDEWEB)

Nishioka, Hajime; Kurashima, Toshio; Kuranishi, Hideaki; Ueda, Kenichi; Takuma, Hiroshi; Sasaki, Akira; Kasuya, Koichi.

1988-09-01

The electron quenching rate of KrF/sup */ in an electron beam pumped laser has been studied by accurately measuring the saturation intensity in a mixture of Ar/Kr/F/sub 2/ = 94/6/0.284. The input intensity of the measurements was widely varied from 100 W cm/sup -2/ (small signal region) to 100 MW cm/sup -2/ (absorption dominant region) in order to separate laser parameters which are small signal gain coefficient, absorption coefficient, and saturation intensity from the measured net gain coefficients. The gas pressure and the pump rate were varied in the range of 0.5 to 2.5 atm and 0.3 to 1.4 MW cm/sup -3/, respectively. The electron quenching rate constant of 4.5 x 10/sup -7/ cm/sup 3/s/sup -1/ was obtained from the pressure and the pump rate dependence of the KrF/sup */ saturation intensity with the temperature dependence of the rate gas 3-body quenching rate as a function of gas temperature to the -3rd power. The small signal gain coefficients calculated with the determined quenching rate constants shows excellent agreement with the measurements.

Measurements of Lunar Dust Charging Properties by Electron Impact

Science.gov (United States)

Abbas, Mian M.; Tankosic, Dragana; Craven, Paul D.; Schneider, Todd A.; Vaughn, Jason A.; LeClair, Andre; Spann, James F.; Norwood, Joseph K.

2009-01-01

Dust grains in the lunar environment are believed to be electrostatically charged predominantly by photoelectric emissions resulting from solar UV radiation on the dayside, and on the nightside by interaction with electrons in the solar wind plasma. In the high vacuum environment on the lunar surface with virtually no atmosphere, the positive and negative charge states of micron/submicron dust grains lead to some unusual physical and dynamical dust phenomena. Knowledge of the electrostatic charging properties of dust grains in the lunar environment is required for addressing their hazardous effect on the humans and mechanical systems. It is well recognized that the charging properties of individual small micron size dust grains are substantially different from the measurements on bulk materials. In this paper we present the results of measurements on charging of individual Apollo 11 and Apollo 17 dust grains by exposing them to mono-energetic electron beams in the 10-100 eV energy range. The charging/discharging rates of positively and negatively charged particles of approx. 0.1 to 5 micron radii are discussed in terms of the sticking efficiencies and secondary electron yields. The secondary electron emission process is found to be a complex and effective charging/discharging mechanism for incident electron energies as low as 10-25 eV, with a strong dependence on particle size. Implications of the laboratory measurements on the nature of dust grain charging in the lunar environment are discussed.

Measurement of Electron Clouds in Large Accelerators by Microwave Dispersion

Energy Technology Data Exchange (ETDEWEB)

De Santis, S.; Byrd, J.M.; /LBL, Berkeley; Caspers, F.; /CERN; Krasnykh, A.; /SLAC; Kroyer, T.; /CERN; Pivi, M.T.F.; /SLAC; Sonnad, K.G.; /LBL, Berkeley

2008-03-19

Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation at high currents. Furthermore, it is difficult to probe their density over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave transmitted over a section of the accelerator and used it to measure the average electron cloud density over a 50 m section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center.

Calibration Base Lines for Electronic Distance Measuring Instruments (EDMI)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — A calibration base line (CBL) is a precisely measured, straight-line course of approximately 1,400 m used to calibrate Electronic Distance Measuring Instruments...

Electron Beam Size Measurements in a Cooling Solenoid

CERN Document Server

Kroc, Thomas K; Burov, Alexey; Seletsky, Sergey; Shemyakin, Alexander V

2005-01-01

The Fermilab Electron Cooling Project requires a straight trajectory and constant beam size to provide effective cooling of the antiprotons in the Recycler. A measurement system was developed using movable appertures and steering bumps to measure the beam size in a 20 m long, nearly continuous, solenoid. This paper discusses the required beam parameters, the implimentation of the measurement system and results for our application.

Plasma dynamics with second and third-harmonic ECRH and access to quasi-stationary ELM-free H-mode on TCV

International Nuclear Information System (INIS)

Porte, L.; Coda, S.; Alberti, S.; Arnoux, G.; Blanchard, P.; Bortolon, A.; Fasoli, A.; Goodman, T.P.; Klimanov, Y.; Martin, Y.; Maslov, M.; Scarabosio, A.; Weisen, H.

2007-01-01

Intense electron cyclotron resonance heating (ECRH) and electron cyclotron current drive (ECCD) are employed on the Tokamak a Configuration Variable (TCV) both in second- and third-harmonic X-mode (X2 and X3). The plasma behaviour under such conditions is driven largely by the electron dynamics, motivating extensive studies of the heating and relaxation phenomena governing both the thermal and suprathermal electron populations. In particular, the dynamics of suprathermal electrons are intimately tied to the physics of X2 ECCD. ECRH is also a useful tool for manipulating the electron distribution function in both physical and velocity space. Fundamental studies of the energetic electron dynamics have been performed using periodic, low-duty-cycle bursts of ECRH, with negligible average power injection, and with electron cyclotron emission (ECE). The characteristic times of the dynamical evolution are clearly revealed. Suprathermal electrons have also been shown to affect the absorption of X3 radiation. Thermal electrons play a crucial role in high density plasmas where indirect ion heating can be achieved through ion-electron collisions. In recent experiments ∼ 1.35 MW of vertically launched X3 ECRH was coupled to a diverted ELMy H-mode plasma. In cases where ≥ 1.1 MW of ECRH power was coupled, the discharge was able to transition into a quasi-stationary ELM-free H-mode regime. These H-modes operated at β N ∼ 2, n-bar e /n G approx. 0.25 and had high energy confinement, H IPB98(y,2) up to ∼ 1.6. Despite being purely electron heated and having no net particle source these discharges maintained a density peaking factor (n e,o /(n e ) ∼ 1.6). They also exhibited spontaneous toroidal momentum production in the co-current direction. The momentum production is due to a transport process as there is no external momentum input. This process supports little or no radial gradient of the toroidal velocity

Measuring processes with opto-electronic semiconductor components

International Nuclear Information System (INIS)

1985-01-01

This is a report on the state of commercially available semiconductor emitters and detectors for the visible, near, middle and remote infrared range. A survey is given on the distance, speed, flow and length measuring techniques using opto-electronic components. Automatic focussing, the use of light barriers, non-contact temperature measurements, spectroscopic gas, liquid and environmental measurement techniques and gas analysis in medical techniques show further applications of the new components. The modern concept of guided radiation in optical fibres and their use in system technology is briefly explained. (DG) [de

Measurements of beat wave accelerated electrons in a toroidal plasma

International Nuclear Information System (INIS)

Rogers, J.H.

1992-06-01

Electrons are accelerated by large amplitude electron plasma waves driven by counter-propagating microwaves with a difference frequency approximately equal to the electron plasma frequency. Energetic electrons are observed only when the phase velocity of the wave is in the range 3v e ph e (v ph was varied 2v e ph e ), where v e is the electron thermal velocity, (kT e /m e ) 1/2 . As the phase velocity increases, fewer electrons are accelerated to higher velocities. The measured current contained in these accelerated electrons has the power dependence predicted by theory, but the magnitude is lower than predicted

Direct measurement of electron beam quality conversion factors using water calorimetry.

Science.gov (United States)

Renaud, James; Sarfehnia, Arman; Marchant, Kristin; McEwen, Malcolm; Ross, Carl; Seuntjens, Jan

2015-11-01

In this work, the authors describe an electron sealed water calorimeter (ESWcal) designed to directly measure absorbed dose to water in clinical electron beams and its use to derive electron beam quality conversion factors for two ionization chamber types. A functioning calorimeter prototype was constructed in-house and used to obtain reproducible measurements in clinical accelerator-based 6, 9, 12, 16, and 20 MeV electron beams. Corrections for the radiation field perturbation due to the presence of the glass calorimeter vessel were calculated using Monte Carlo (MC) simulations. The conductive heat transfer due to dose gradients and nonwater materials was also accounted for using a commercial finite element method software package. The relative combined standard uncertainty on the ESWcal dose was estimated to be 0.50% for the 9-20 MeV beams and 1.00% for the 6 MeV beam, demonstrating that the development of a water calorimeter-based standard for electron beams over such a wide range of clinically relevant energies is feasible. The largest contributor to the uncertainty was the positioning (Type A, 0.10%-0.40%) and its influence on the perturbation correction (Type B, 0.10%-0.60%). As a preliminary validation, measurements performed with the ESWcal in a 6 MV photon beam were directly compared to results derived from the National Research Council of Canada (NRC) photon beam standard water calorimeter. These two independent devices were shown to agree well within the 0.43% combined relative uncertainty of the ESWcal for this beam type and quality. Absorbed dose electron beam quality conversion factors were measured using the ESWcal for the Exradin A12 and PTW Roos ionization chambers. The photon-electron conversion factor, kecal, for the A12 was also experimentally determined. Nonstatistically significant differences of up to 0.7% were found when compared to the calculation-based factors listed in the AAPM's TG-51 protocol. General agreement between the relative

Note on measuring electronic stopping of slow ions

Science.gov (United States)

Sigmund, P.; Schinner, A.

2017-11-01

Extracting stopping cross sections from energy-loss measurements requires careful consideration of the experimental geometry. Standard procedures for separating nuclear from electronic stopping treat electronic energy loss as a friction force, ignoring its dependence on impact parameter. In the present study we find that incorporating this dependence has a major effect on measured stopping cross sections, in particular for light ions at low beam energies. Calculations have been made for transmission geometry, nuclear interactions being quantified by Bohr-Williams theory of multiple scattering on the basis of a Thomas-Fermi-Molière potential, whereas electronic interactions are characterized by Firsov theory or PASS code. Differences between the full and the restricted stopping cross section depend on target thickness and opening angle of the detector and need to be taken into account in comparisons with theory as well as in applications of stopping data. It follows that the reciprocity principle can be violated when checked on restricted instead of full electronic stopping cross sections. Finally, we assert that a seeming gas-solid difference in stopping of low-energy ions is actually a metal-insulator difference. In comparisons with experimental results we mostly consider proton data, where nuclear stopping is only a minor perturbation.

Electron attachment rate constant measurement by photoemission electron attachment ion mobility spectrometry (PE-EA-IMS)

International Nuclear Information System (INIS)

Su, Desheng; Niu, Wenqi; Liu, Sheng; Shen, Chengyin; Huang, Chaoqun; Wang, Hongmei; Jiang, Haihe; Chu, Yannan

2012-01-01

Photoemission electron attachment ion mobility spectrometry (PE-EA-IMS), with a source of photoelectrons induced by vacuum ultraviolet radiation on a metal surface, has been developed to study electron attachment reaction at atmospheric pressure using nitrogen as the buffer gas. Based on the negative ion mobility spectra, the rate constants for electron attachment to tetrachloromethane and chloroform were measured at ambient temperature as a function of the average electron energy in the range from 0.29 to 0.96 eV. The experimental results are in good agreement with the data reported in the literature. - Highlights: ► Photoemission electron attachment ion mobility spectrometry (PE-EA-IMS) was developed to study electron attachment reaction. ► The rate constants of electron attachment to CCl 4 and CHCl 3 were determined. ► The present experimental results are in good agreement with the previously reported data.

Burst mode trigger of STEREO in situ measurements

Science.gov (United States)

Jian, L. K.; Russell, C. T.; Luhmann, J. G.; Curtis, D.; Schroeder, P.

2013-06-01

Since the launch of the STEREO spacecraft, the in situ instrument suites have continued to modify their burst mode trigger in order to optimize the collection of high-cadence magnetic field, solar wind, and suprathermal electron data. This report reviews the criteria used for the burst mode trigger and their evolution with time. From 2007 to 2011, the twin STEREO spacecraft observed 236 interplanetary shocks, and 54% of them were captured by the burst mode trigger. The capture rate increased remarkably with time, from 30% in 2007 to 69% in 2011. We evaluate the performance of multiple trigger criteria and investigate why some of the shocks were missed by the trigger. Lessons learned from STEREO are useful for future missions, because the telemetry bandwidth needed to capture the waveforms of high frequency but infrequent events would be unaffordable without an effective burst mode trigger.

Quantitative biological measurement in Transmission Electron Tomography

International Nuclear Information System (INIS)

Mantell, Judith M; Verkade, Paul; Arkill, Kenton P

2012-01-01

It has been known for some time that biological sections shrink in the transmission electron microscope from exposure to the electron beam. This phenomenon is especially important in Electron Tomography (ET). The effect on shrinkage of parameters such as embedding medium or sample type is less well understood. In addition anisotropic area shrinkage has largely been ignored. The intention of this study is to explore the shrinkage on a number of samples ranging in thickness from 200 nm to 500 nm. A protocol was developed to determine the shrinkage in area and thickness using the gold fiducials used in electron tomography. In brief: Using low dose philosophy on the section, a focus area was used prior to a separate virgin study area for a series of known exposures on a tilted sample. The shrinkage was determined by measurements on the gold beads from both sides of the section as determined by a confirmatory tomogram. It was found that the shrinkage in area (approximately to 90-95% of the original) and the thickness (approximately 65% of the original at most) agreed with pervious authors, but that a lmost all the shrinkage was in the first minute and that although the direction of the in-plane shrinkage (in x and y) was sometimes uneven the end result was consistent. It was observed, in general, that thinner samples showed more percentage shrinkage than thicker ones. In conclusion, if direct quantitative measurements are required then the protocol described should be used for all areas studied.

Quantitative biological measurement in Transmission Electron Tomography

Science.gov (United States)

Mantell, Judith M.; Verkade, Paul; Arkill, Kenton P.

2012-07-01

It has been known for some time that biological sections shrink in the transmission electron microscope from exposure to the electron beam. This phenomenon is especially important in Electron Tomography (ET). The effect on shrinkage of parameters such as embedding medium or sample type is less well understood. In addition anisotropic area shrinkage has largely been ignored. The intention of this study is to explore the shrinkage on a number of samples ranging in thickness from 200 nm to 500 nm. A protocol was developed to determine the shrinkage in area and thickness using the gold fiducials used in electron tomography. In brief: Using low dose philosophy on the section, a focus area was used prior to a separate virgin study area for a series of known exposures on a tilted sample. The shrinkage was determined by measurements on the gold beads from both sides of the section as determined by a confirmatory tomogram. It was found that the shrinkage in area (approximately to 90-95% of the original) and the thickness (approximately 65% of the original at most) agreed with pervious authors, but that a lmost all the shrinkage was in the first minute and that although the direction of the in-plane shrinkage (in x and y) was sometimes uneven the end result was consistent. It was observed, in general, that thinner samples showed more percentage shrinkage than thicker ones. In conclusion, if direct quantitative measurements are required then the protocol described should be used for all areas studied.

Electronic instrumentation system for pulsed neutron measurements

International Nuclear Information System (INIS)

Burda, J.; Igielski, A.; Kowalik, W.

1982-01-01

An essential point of pulsed neutron measurement of thermal neutron parameters for different materials is the registration of the thermal neutron die-away curve after a fast neutron bursts have been injected into the system. An electronic instrumentation system which is successfully applied for pulsed neutron measurements is presented. An important part of the system is the control unit which has been designed and built in the Laboratory of Neutron Parameters of Materials. (author)

Measurements and simulations of seeded electron microbunches with collective effects

Directory of Open Access Journals (Sweden)

K. Hacker

2015-09-01

Full Text Available Measurements of the longitudinal phase-space distributions of electron bunches seeded with an external laser were done in order to study the impact of collective effects on seeded microbunches in free-electron lasers. When the collective effects of Coulomb forces in a drift space and coherent synchrotron radiation in a chicane are considered, velocity bunching of a seeded microbunch appears to be a viable alternative to compression with a magnetic chicane under high-gain harmonic generation seeding conditions. Measurements of these effects on seeded electron microbunches were performed with a rf deflecting structure and a dipole magnet which streak out the electron bunch for single-shot images of the longitudinal phase-space distribution. Particle tracking simulations in 3D predicted the compression dynamics of the seeded microbunches with collective effects.

The beam energy measurement system for the Beijing electron-positron collider

International Nuclear Information System (INIS)

Zhang, J.Y.; Abakumova, E.V.; Achasov, M.N.; Blinov, V.E.; Cai, X.; Dong, H.Y.; Fu, C.D.; Harris, F.A.; Kaminsky, V.V.; Krasnov, A.A.; Liu, Q.; Mo, X.H.; Muchnoi, N.Yu.; Nikolaev, I.B.; Qin, Q.; Qu, H.M.; Olsen, S.L.; Pyata, E.E.; Shamov, A.G.; Shen, C.P.

2012-01-01

The beam energy measurement system (BEMS) for the upgraded Beijing electron-positron collider BEPC-II is described. The system is based on measuring the energies of Compton back-scattered photons. The relative systematic uncertainty of the electron and positron beam energy determination is estimated as 2⋅10 -5 .

Precise measurement in elastic electron scattering: HAPPEX and E-158 experiments

International Nuclear Information System (INIS)

Vacheret, A.

2004-12-01

Parity Violation asymmetry measurements in elastic electron scattering are in one hand an interesting way of retrieving new informations about the sea quarks of the nucleon and in the other hand a powerful test of the Standard Model electroweak sector at low energy. This thesis describes the HAPPEX experiment at JLab and the E-158 experiment at SLAC (USA) which measure de parity violation asymmetries in elastic scattering of polarized electron on nuclei like Hydrogen or Helium and on atomic electrons. With the measurements on hadronic targets one can extract the strange quarks contribution to the charge and current density of the nucleon. With the electron-electron scattering one can test the standard model at the loop level and far from the Z pole by extracting sin 2 θ W . In this thesis we describe the formalism associated with the electroweak probe. We present in detail the experimental methods used to make such precise measurements of parity violation asymmetry. Then, we describe the experimental set-up of each experiment and in particular the electron detector and the feedback loop on the beam current for the HAPPEX experiment and the analysis of E-158 run III with a dedicated systematic study on the beam sub-pulse fluctuations. We present the preliminary results for each experiment with a comparison with the other existing results and the future experiments. (author)

Measurements of absorbed energy distributions in water from pulsed electron beams

International Nuclear Information System (INIS)

Devanney, J.A.

1974-01-01

An evaluation of the use of a holographic interferometer to measure the energy deposition as a function of depth in water from pulsed electron beams, together with a brief description of the interferometer and the technique of generating a hologram are presented. The holographic interferometer is used to measure the energy deposition as a function of depth in water from various pulsed beams of monoenergetic electrons in the energy range from 1.0 to 2.5 MeV. These results are compared to those computed by using a Monte Carlo radiation transport code, ETRAN-15, for the same electron energies. After the discrepancies between the measured and computed results are evaluated, reasonable agreement is found between the measured and computed absorbed energy distributions as a function of depth in water. An evalutation of the response of the interferometer as a function of electron intensities is performed. A comparison among four energy deposition curves that result from the irradiation of water with pulsed electron beams from a Febetron accelerator, model 705, is presented. These pulsed beams were produced by the same vacuum diode with the same charging voltage. The results indicate that the energy distribution of the electrons in the pulsed beam is not always constant. A comparison of the energy deposition curves that result from the irradiation of water with electron pulses from different vacuum diodes but the same charging voltage is presented. These results indicate again that the energy distribution of the electrons in the pulsed beam may vary between vacuum diodes. These differences would not be realized by using a totally absorbing metal calorimeter and Faraday Cup

Characterisation of a MOSFET-based detector for dose measurement under megavoltage electron beam radiotherapy

Science.gov (United States)

Jong, W. L.; Ung, N. M.; Tiong, A. H. L.; Rosenfeld, A. B.; Wong, J. H. D.

2018-03-01

The aim of this study is to investigate the fundamental dosimetric characteristics of the MOSkin detector for megavoltage electron beam dosimetry. The reproducibility, linearity, energy dependence, dose rate dependence, depth dose measurement, output factor measurement, and surface dose measurement under megavoltage electron beam were tested. The MOSkin detector showed excellent reproducibility (>98%) and linearity (R2= 1.00) up to 2000 cGy for 4-20 MeV electron beams. The MOSkin detector also showed minimal dose rate dependence (within ±3%) and energy dependence (within ±2%) over the clinical range of electron beams, except for an energy dependence at 4 MeV electron beam. An energy dependence correction factor of 1.075 is needed when the MOSkin detector is used for 4 MeV electron beam. The output factors measured by the MOSkin detector were within ±2% compared to those measured with the EBT3 film and CC13 chamber. The measured depth doses using the MOSkin detector agreed with those measured using the CC13 chamber, except at the build-up region due to the dose volume averaging effect of the CC13 chamber. For surface dose measurements, MOSkin measurements were in agreement within ±3% to those measured using EBT3 film. Measurements using the MOSkin detector were also compared to electron dose calculation algorithms namely the GGPB and eMC algorithms. Both algorithms were in agreement with measurements to within ±2% and ±4% for output factor (except for the 4 × 4 cm2 field size) and surface dose, respectively. With the uncertainties taken into account, the MOSkin detector was found to be a suitable detector for dose measurement under megavoltage electron beam. This has been demonstrated in the in vivo skin dose measurement on patients during electron boost to the breast tumour bed.

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.

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.

First measurements of electron vorticity in the foreshock and solar wind

International Nuclear Information System (INIS)

Gurgiolo, C.; Goldstein, M.L.; Vinas, A.F.; Fazakerley, A.N.

2010-01-01

We describe the methodology used to set up and compute spatial derivatives of the electron moments using data acquired by the Plasma Electron And Current Experiment (PEACE) from the four Cluster spacecraft. The results are used to investigate electron vorticity in the foreshock. We find that much of the measured vorticity, under nominal conditions, appears to be caused by changes in the flow direction of the return (either reflected or leakage from the magnetosheath) and strahl electron populations as they couple to changes in the magnetic field orientation. This in turn results in deflections in the total bulk velocity producing the measured vorticity. (orig.)

First measurements of electron vorticity in the foreshock and solar wind

Energy Technology Data Exchange (ETDEWEB)

Gurgiolo, C. [Bitterroot Basic Research, Hamilton, MT (United States); Goldstein, M.L.; Vinas, A.F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Geospace Science Lab.; Fazakerley, A.N. [University College London (United Kingdom). Mullard Space Science Lab.

2010-07-01

We describe the methodology used to set up and compute spatial derivatives of the electron moments using data acquired by the Plasma Electron And Current Experiment (PEACE) from the four Cluster spacecraft. The results are used to investigate electron vorticity in the foreshock. We find that much of the measured vorticity, under nominal conditions, appears to be caused by changes in the flow direction of the return (either reflected or leakage from the magnetosheath) and strahl electron populations as they couple to changes in the magnetic field orientation. This in turn results in deflections in the total bulk velocity producing the measured vorticity. (orig.)

First measurements of electron vorticity in the foreshock and solar wind

Directory of Open Access Journals (Sweden)

C. Gurgiolo

2010-12-01

Full Text Available We describe the methodology used to set up and compute spatial derivatives of the electron moments using data acquired by the Plasma Electron And Current Experiment (PEACE from the four Cluster spacecraft. The results are used to investigate electron vorticity in the foreshock. We find that much of the measured vorticity, under nominal conditions, appears to be caused by changes in the flow direction of the return (either reflected or leakage from the magnetosheath and strahl electron populations as they couple to changes in the magnetic field orientation. This in turn results in deflections in the total bulk velocity producing the measured vorticity.

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...

Measurement of the electron beam mode in earth's foreshock

Science.gov (United States)

Onsager, T. G.; Holzworth, R. H.

1990-01-01

High frequency electric field measurements from the AMPTE IRM plasma wave receiver are used to identify three simultaneously excited electrostatic wave modes in the earth's foreshock region: the electron beam mode, the Langmuir mode, and the ion acoustic mode. A technique is developed which allows the rest frame frequecy and wave number of the electron beam waves to be determined. It is shown that the experimentally determined rest frame frequency and wave number agree well with the most unstable frequency and wave number predicted by linear homogeneous Vlasov theory for a plasma with Maxwellian background electrons and a Lorentzian electron beam. From a comparison of the experimentally determined and theoretical values, approximate limits are put on the electron foreshock beam temperatures. A possible generation mechanism for ion acoustic waves involving mode coupling between the electron beam and Langmuir modes is also discussed.

Polystyrene calorimeter for electron beam dose measurements

DEFF Research Database (Denmark)

Miller, A.

1995-01-01

Calorimeters from polystrene have been constructed for dose measurement at 4-10 MeV electron accelerators. These calorimeters have been used successfully for a few years, and polystyrene calorimeters for use at energies down to 1 MeV and being tested. Advantage of polystyrene as the absorbing...

Electron-Scale Measurements of Magnetic Reconnection in Space

Science.gov (United States)

Burch, J. L.; Torbert, R. B.; Phan, T. D.; Chen, L.-J.; Moore, T. E.; Ergun, R. E.; Eastwood, J. P.; Gershman, D. J.; Cassak, P. A.; Argall, M. R.;

Secondary electron measurement and XPS characterization of NEG coatings

International Nuclear Information System (INIS)

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

2014-01-01

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

Trade Measures for Regulating Transboundary Movement of Electronic Waste

Directory of Open Access Journals (Sweden)

Gideon Emcee Christian

2017-08-01

Full Text Available International trade in used electrical and electronics equipment (UEEE provides an avenue for socio-economic development in the developing world and also serves as a conduit for transboundary dumping of waste electrical and electronic equipment (WEEE also referred to as electronic waste or e-waste. The latter problem arises from the absence of a regulatory framework for differentiating between functional UEEE and junk e-waste. This has resulted in both functional UEEE and junk e-waste being concurrently shipped to developing countries under the guise of international trade in used electronics. Dealing with these problems will require effective regulation of international trade in UEEE from both exporting and importing countries. Although, the export of e-waste from the European Community to developing countries is currently prohibited, significant amount of e-waste from the region continue to flow into developing countries due to lax regulatory measures in the latter. Hence, there is need for a regulatory regime in developing countries to complement the prohibitory regime in the major e-waste source countries. This paper proposes trade measures modelled in line with WTO rules which could be adopted by developing countries in addressing these problems. The proposed measures include the development of a compulsory certification and labelling system for functional UEEE as well as trade ban on commercial importation of UEEE not complying with the said certification and labelling system. The paper then goes further to examine these proposed measures in the light of WTO rules and jurisprudence.

Laser diagnostics of high vibrational and rotational H2-states

International Nuclear Information System (INIS)

Mosbach, Th.; Schulz-von der Gathen, V.; Doebele, H.F.

2002-01-01

We report on measurements of vibrational and rotational excited electronic-ground-state hydrogen molecules in a magnetic multipole plasma source by LIF with VUV radiation. The measurements are taken after rapid shut-off of the discharge current. Absolute level populations are obtained using Rayleigh scattering calibration with Krypton. The theoretically predicted suprathermal population of the vibrational distribution is clearly identified. We found also non-Boltzmann rotational distributions for the high vibrational states. The addition of noble gases (Argon and Xenon) to hydrogen leads to a decrease of the vibrational population. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

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

NARCIS (Netherlands)

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

2012-01-01

At the fusion experiment JET, a Michelson interferometer is used to measure the spectrum of the electron cyclotron emission in the spectral range 70-500 GHz. The interferometer is absolutely calibrated using the hot/cold technique and, in consequence, the spatial profile of the plasma electron

The Role of Diffusion in the Transport of Energetic Electrons during Solar Flares

Energy Technology Data Exchange (ETDEWEB)

Bian, Nicolas H.; Kontar, Eduard P. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom); Emslie, A. Gordon, E-mail: nicolas.bian@glasgow.gla.ac.uk, E-mail: emslieg@wku.edu [Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101 (United States)

2017-02-01

The transport of the energy contained in suprathermal electrons in solar flares plays a key role in our understanding of many aspects of flare physics, from the spatial distributions of hard X-ray emission and energy deposition in the ambient atmosphere to global energetics. Historically the transport of these particles has been largely treated through a deterministic approach, in which first-order secular energy loss to electrons in the ambient target is treated as the dominant effect, with second-order diffusive terms (in both energy and angle) generally being either treated as a small correction or even neglected. Here, we critically analyze this approach, and we show that spatial diffusion through pitch-angle scattering necessarily plays a very significant role in the transport of electrons. We further show that a satisfactory treatment of the diffusion process requires consideration of non-local effects, so that the electron flux depends not just on the local gradient of the electron distribution function but on the value of this gradient within an extended region encompassing a significant fraction of a mean free path. Our analysis applies generally to pitch-angle scattering by a variety of mechanisms, from Coulomb collisions to turbulent scattering. We further show that the spatial transport of electrons along the magnetic field of a flaring loop can be modeled rather effectively as a Continuous Time Random Walk with velocity-dependent probability distribution functions of jump sizes and occurrences, both of which can be expressed in terms of the scattering mean free path.

Measurements of electron excitation and recombination for Ne-like Ba46+

International Nuclear Information System (INIS)

Marrs, R.E.; Levine, M.A.; Knapp, D.A.; Henderson, J.R.

1987-07-01

A new facility at Lawrence Livermore National Laboratory has been used to obtain measurements for electron-impact excitation, dielectronic recombination and radiative recombination for the neon-like Ba 46+ ion. The experimental technique consists of trapping highly charged ions inside the space charge of an electron beam and measuring their x-ray emission spectra

Measurement of the diffusion length of thermal neutrons inside graphite

International Nuclear Information System (INIS)

Ertaud, A.; Beauge, R.; Fauquez, H.; De Laboulay, H.; Mercier, C.; Vautrey, L.

1948-11-01

The diffusion length of thermal neutrons inside a given industrial graphite is determined by measuring the neutron density inside a parallelepipedal piling up of graphite bricks (2.10 x 2.10 x 2.442 m). A 3.8 curies (Ra α → Be) source is placed inside the parallelepipedal block of graphite and thin manganese detectors are used. Corrections are added to the unweighted measurements to take into account the effects of the damping of supra-thermal neutrons in the measurement area. These corrections are experimentally deduced from the differential measurements made with a cadmium screen interposed between the source and the first plane of measurement. An error analysis completes the report. The diffusion length obtained is: L = 45.7 cm ± 0.3. The average density of the graphite used is 1.76 and the average apparent density of the piling up is 1.71. (J.S.)

Active silicon x-ray for measuring electron temperature

International Nuclear Information System (INIS)

Snider, R.T.

1994-07-01

Silicon diodes are commonly used for x-ray measurements in the soft x-ray region between a few hundred ev and 20 keV. Recent work by Cho has shown that the charge collecting region in an underbiased silicon detector is the depletion depth plus some contribution from a region near the depleted region due to charge-diffusion. The depletion depth can be fully characterized as a function of the applied bias voltage and is roughly proportional to the squart root of the bias voltage. We propose a technique to exploit this effect to use the silicon within the detector as an actively controlled x-ray filter. With reasonable silicon manufacturing methods, a silicon diode detector can be constructed in which the sensitivity of the collected charge to the impinging photon energy spectrum can be changed dynamically in the visible to above the 20 keV range. This type of detector could be used to measure the electron temperature in, for example, a tokamak plasma by sweeping the applied bias voltage during a plasma discharge. The detector samples different parts of the energy spectrum during the bias sweep, and the data collected contains enough information to determine the electron temperature. Benefits and limitations of this technique will be discussed along with comparisons to similar methods for measuring electron temperature and other applications of an active silicon x-ray filter

Deka-keV X-ray emission associated with the onset of radio noise storms

DEFF Research Database (Denmark)

Crosby, N.; Vilmer, N.; Lund, Niels

1996-01-01

Radio noise storms show that suprathermal electrons (a few tens of keV) are present in the vicinity of active regions during several hours or even a few days. Where and how these electrons are energized is not yet well known. A flare-like sudden energy release in the active region is in general o...

Direct measurement of electron beam quality conversion factors using water calorimetry

Energy Technology Data Exchange (ETDEWEB)

Renaud, James, E-mail: james.renaud@mail.mcgill.ca; Seuntjens, Jan [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4 (Canada); Sarfehnia, Arman [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5S 3E2 (Canada); Marchant, Kristin [Allan Blair Cancer Centre, Saskatchewan Cancer Agency, Regina, Saskatchewan S4T 7T1, Canada and Department of Oncology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A1 (Canada); McEwen, Malcolm; Ross, Carl [Ionizing Radiation Standards, National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)

2015-11-15

Purpose: In this work, the authors describe an electron sealed water calorimeter (ESWcal) designed to directly measure absorbed dose to water in clinical electron beams and its use to derive electron beam quality conversion factors for two ionization chamber types. Methods: A functioning calorimeter prototype was constructed in-house and used to obtain reproducible measurements in clinical accelerator-based 6, 9, 12, 16, and 20 MeV electron beams. Corrections for the radiation field perturbation due to the presence of the glass calorimeter vessel were calculated using Monte Carlo (MC) simulations. The conductive heat transfer due to dose gradients and nonwater materials was also accounted for using a commercial finite element method software package. Results: The relative combined standard uncertainty on the ESWcal dose was estimated to be 0.50% for the 9–20 MeV beams and 1.00% for the 6 MeV beam, demonstrating that the development of a water calorimeter-based standard for electron beams over such a wide range of clinically relevant energies is feasible. The largest contributor to the uncertainty was the positioning (Type A, 0.10%–0.40%) and its influence on the perturbation correction (Type B, 0.10%–0.60%). As a preliminary validation, measurements performed with the ESWcal in a 6 MV photon beam were directly compared to results derived from the National Research Council of Canada (NRC) photon beam standard water calorimeter. These two independent devices were shown to agree well within the 0.43% combined relative uncertainty of the ESWcal for this beam type and quality. Absorbed dose electron beam quality conversion factors were measured using the ESWcal for the Exradin A12 and PTW Roos ionization chambers. The photon-electron conversion factor, k{sub ecal}, for the A12 was also experimentally determined. Nonstatistically significant differences of up to 0.7% were found when compared to the calculation-based factors listed in the AAPM’s TG-51 protocol

Electron temperature from x-ray continuum measurements on the NIF

Science.gov (United States)

Jarrott, Leonard; Bachmann, Benjamin; Benedetti, Robin; Izumi, Nobuhiko; Khan, Shahab; Landen, Otto; Ma, Tammy; Nagel, Sabrina; Pak, Arthur; Patel, Prav; Schneider, Marilyn; Springer, Paul; LLNL Collaboration

2017-10-01

We report on measurements of the electron temperature within the hot spot of inertially confined, layered implosions on the NIF using a titanium differential filtering x-ray diagnostic. The electron temperature from x-ray emission is insensitive to non-thermal velocity flows as is the case with ion temperature measurements and is thus a critical parameter in interpreting stagnated hot spot conditions. Here we discuss measurements using titanium filters ranging from 10 μm to 1mm in thickness with a sensitivity band of 10-30keV coupled with penumbral pinholes. The use of larger pinhole diameters increases x-ray fluence improving sensitivity of photon energies with minimal attenuation from the compressed fuel/shell. This diagnostic has been fielded on a series of cryogenic shots with DT ion temperatures ranging from 2-5keV. Analysis of the measurement will be presented along with a comparison against simulated electron temperatures and x-ray spectra as well as a comparison to DT ion temperature measurements. This work was performed under the auspices of U.S. DoE by LLNL under Contract No. DE-AC52-07NA27344.

Note: Measurement of the runaway electrons in the J-TEXT tokamak

International Nuclear Information System (INIS)

Chen, Z. Y.; Zhang, Y.; Zhang, X. Q.; Luo, Y. H.; Jin, W.; Li, J. C.; Chen, Z. P.; Wang, Z. J.; Yang, Z. J.; Zhuang, G.

2012-01-01

The runaway electrons have been measured by hard x-ray detectors and soft x-ray array in the J-TEXT tokamak. The hard x-ray radiations in the energy ranges of 0.5-5 MeV are measured by two NaI detectors. The flux of lost runaway electrons can be obtained routinely. The soft x-ray array diagnostics are used to monitor the runaway beam generated in disruptions since the soft x-ray is dominated by the interaction between runaway electrons and metallic impurities inside the plasma. With the aid of soft x-ray array, runaway electron beam has been detected directly during the formation of runaway current plateau following the disruptions.

Cross-Field Current Instabilities in Thin Ionization Layers and the Enhanced Aurora

International Nuclear Information System (INIS)

Johnson, Jay R.; Okuda, Hideo

2008-01-01

Nearly half of the time, auroral displays exhibit thin, bright layers known as 'enhanced aurora'. There is a substantial body of evidence that connects these displays with thin, dense, heavy ion layers in the E-region. Based on the spectral characteristics of the enhanced layers, it is believed that they result when wave-particle interaction heats ambient electrons to energies at or just above the 17 eV ionization energy of N2. While there are several possible instabilities that could produce suprathermal electrons in thin layers, there has been no clear theoretical investigation which examines in detail how wave instabilities in the thin ionization layers could develop and produce the suprathermal electrons. We examine instabilities which would occur in thin, dense, heavy ion layers using extensive analytical analysis combined with particle simulations. We analyze a cross field current instability that is found to be strongly unstable in the heavy ion layers. Electrostatic simulations show that substantial heating of the ambient electrons occurs with energization at or above the N2 ionization energy.

Measurements of electron drift velocity in pure isobutane

Energy Technology Data Exchange (ETDEWEB)

Vivaldini, Tulio C.; Lima, Iara B.; Goncalves, Josemary A.C.; Botelho, Suzana; Tobias, Carmen C.B., E-mail: ccbueno@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Ridenti, Marco A.; Pascholati, Paulo R. [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Fisica. Lab. do Acelerador Linear; Fonte, Paulo; Mangiarotti, Alessio [Universidade de Coimbra (Portugal). Dept de Fisica. Lab. de Instrumentacao e Fisica Experimental de Particulas

2009-07-01

In this work we report on preliminary results related to the dependence of the electron drift velocity for pure isobutane as a function of reduced electric field (E/N) in the range from 100 Td up to 216 Td. The measurements of electron drift velocity were based on the Pulsed Townsend technique. In order to validate the technique and analyzing non-uniformity effects, results for nitrogen are also presented and compared with a numerical simulation of the Bolsig+ code. (author)

Measurements of electron drift velocity in pure isobutane

International Nuclear Information System (INIS)

Vivaldini, Tulio C.; Lima, Iara B.; Goncalves, Josemary A.C.; Botelho, Suzana; Tobias, Carmen C.B.; Ridenti, Marco A.; Pascholati, Paulo R.; Fonte, Paulo; Mangiarotti, Alessio

2009-01-01

In this work we report on preliminary results related to the dependence of the electron drift velocity for pure isobutane as a function of reduced electric field (E/N) in the range from 100 Td up to 216 Td. The measurements of electron drift velocity were based on the Pulsed Townsend technique. In order to validate the technique and analyzing non-uniformity effects, results for nitrogen are also presented and compared with a numerical simulation of the Bolsig+ code. (author)

Measurement of optically and thermally stimulated electron emission from natural minerals

DEFF Research Database (Denmark)

Ankjærgaard, C.; Murray, A.S.; Denby, P.M.

2006-01-01

to a Riso TL/OSL reader, enabling optically stimulated electrons (OSE) and thermally stimulated electrons (TSE) to be measured simultaneously with optically stimulated luminescence (OSL) and thermoluminescence (TL). Repeated irradiation and measurement is possible without removing the sample from...... the counting chamber. Using this equipment both OSE and TSE from loose sand-sized grains of natural minerals has been recorded. It is shown that both the surface electron traps (giving rise to the OSE signals) and the bulk traps (giving rise to OSL) have the same dosimetric properties. A comparison of OSL...

Faraday cup for electron flux measurements on the microtron MT 25

International Nuclear Information System (INIS)

Vognar, M.; Simane, C.; Chvatil, D.

2001-01-01

The basic design criteria for construction of an evacuated Faraday cup for precise measurement of 5-25 MeV electron beam currents in air from a microtron are characterized. The homemade Faraday cup is described along with the electronic chain and its incorporation into the measuring beam line. The provisions applied to reduce backward electron escape are outlined. The current range was 10 -5 to 10 -10 A. The diameter of the Al entrance window of the Faraday cup was 1.8 cm, its area was 2.54 cm 2 and thickness 0.1 mm

Shielded button electrodes for time-resolved measurements of electron cloud buildup

International Nuclear Information System (INIS)

Crittenden, J.A.; Billing, M.G.; Li, Y.; Palmer, M.A.; Sikora, J.P.

2014-01-01

We report on the design, deployment and signal analysis for shielded button electrodes sensitive to electron cloud buildup at the Cornell Electron Storage Ring. These simple detectors, derived from a beam-position monitor electrode design, have provided detailed information on the physical processes underlying the local production and the lifetime of electron densities in the storage ring. Digitizing oscilloscopes are used to record electron fluxes incident on the vacuum chamber wall in 1024 time steps of 100 ps or more. The fine time steps provide a detailed characterization of the cloud, allowing the independent estimation of processes contributing on differing time scales and providing sensitivity to the characteristic kinetic energies of the electrons making up the cloud. By varying the spacing and population of electron and positron beam bunches, we map the time development of the various cloud production and re-absorption processes. The excellent reproducibility of the measurements also permits the measurement of long-term conditioning of vacuum chamber surfaces

Several cases of electronics and the measuring methods

International Nuclear Information System (INIS)

Supardiyono, Bb.; Kamadi, J.; Suparmono, M.; Indarto.

1980-01-01

Several cases of electronics and the measuring methods, covering electric conductivity and electric potential of analog systems, electric current, electric conductivity and electric potential of semiconductor diodes, and characteristics of transistors are described. (SMN)

Alpha and conversion electron spectroscopy of {sup 238,239}Pu and {sup 241}Am and alpha-conversion electron coincidence measurements

Energy Technology Data Exchange (ETDEWEB)

Dion, Michael P., E-mail: michael.dion@pnnl.gov; Miller, Brian W.; Warren, Glen A.

2016-09-11

A technique to determine the isotopic constituents of a mixed actinide sample has been proposed by a coincident alpha-conversion electron measurement. This presents a unique signature to allow the unfolding of isotopes that possess overlapping alpha particle energy and reduce backgrounds of an unseparated sample. The work presented here are results of conversion electron spectroscopy of {sup 241}Am, {sup 238}Pu and {sup 239}Pu using a dual-stage peltier-cooled 25 mm{sup 2} silicon drift detector and alpha spectroscopy with a passivated ion implanted planar silicon detector. The conversion electron spectra were evaluated from 20–55 keV based on fits to the dominant conversion electron emissions, which allowed the relative conversion electron emission intensities to be determined. These measurements provide crucial singles spectral information and calibration to aid in the coincident measurement approach. Furthermore, an alpha-conversion electron spectrometer was assembled using the silicon based detectors described and results of a coincident spectrum analysis is reported for {sup 241}Am.

Measurement of the activity of electron capturing isotopes

International Nuclear Information System (INIS)

Szoerenyi, A.

1980-01-01

In order to measure precisely the activity of electron capturing isotopes, an equipment was constructed for the detection the X-photons, the Auger- and the conversing electrons by a high-pressure, gas-flow 4π proportional counter. The proportional counter and the NaI(Tl) scintillation counter are placed in a common lead-shielding, thus, the equipment is suited for the measurement of radioisotopes decaying in coincidence. The structure of the proportional counter and of the pressure-control system are detailed. As an example, the energy spectra of a 109 Cd solution, taken at different pressures, are published. At a pressure of 1.1 MPa the 3 peaks are well separated. The results of an international test, in which the radioactivity of a 57 Co sample was determined, are published, too. (L.E.)

Measurements of electron cloud growth and mitigation in dipole, quadrupole, and wiggler magnets

Energy Technology Data Exchange (ETDEWEB)

Calvey, J.R., E-mail: jrc97@cornell.edu; Hartung, W.; Li, Y.; Livezey, J.A.; Makita, J.; Palmer, M.A.; Rubin, D.

2015-01-11

Retarding field analyzers (RFAs), which provide a localized measurement of the electron cloud, have been installed throughout the Cornell Electron Storage Ring (CESR), in different magnetic field environments. This paper describes the RFA designs developed for dipole, quadrupole, and wiggler field regions, and provides an overview of measurements made in each environment. The effectiveness of electron cloud mitigations, including coatings, grooves, and clearing electrodes, are assessed with the RFA measurements.

Measurement of the electron beam mode in the Earth's foreshock

International Nuclear Information System (INIS)

Onsager, T.G.; Holzworth, R.H.

1990-01-01

High frequency electric field measurements from the AMPTE IRM plasma wave receiver are used to identify three simultaneously excited electrostatic wave modes in the Earth's foreshock region: the electron beam mode the Langmuir mode, and the ion acoustic mode. A technique is developed which allows the rest frame frequency and wave number of the electron beam waves to be determined. Plasma wave and magnetometer data are used to determine the interplanetary magnetic field direction at which the spacecraft becomes magnetically connected to the Earth's bow shock. From the knowledge of this direction, the upstreaming electron cutoff velocity can be calculated. The authors take this calculated cutoff velocity to be the flow velocity of an electron beam in the plasma. Assuming that the wave phase speed is approximately equal to the beam speed and using the measured electric field frequency, they determine the plasma rest frame frequency and the wave number. They then show that the experimentally determined rest frame frequency and wave number agree well with the most unstable frequency and wave number predicted by linear homogeneous Vlasov theory for a plasma with Maxwellian background electrons and a Lorentzian electron beam. From a comparison of the experimentally determined and theoretical values, approximate limits are put on the electron foreshock beam temperatures. A possible generation mechanism for ion acoustic waves involving mode coupling between the electron beam and Langmuir modes is also discussed

Spectral measurements of runway electrons in the TEXTOR tokamak

International Nuclear Information System (INIS)

Kudyakov, Timur

2009-01-01

The generation of multi-MeV runaway electrons is a well known effect related to the plasma disruptions in tokamaks. The runaway electrons can substantially reduce the lifetime of the future tokamak ITER. In this thesis physical properties of runaway electrons and their possible negative effects on ITER have been studied in the TEXTOR tokamak. A new diagnostic, a scanning probe, has been developed to provide direct measurements of the absolute number of runaway electrons coming from the plasma, its energy distribution and the related energy load in the material during low density (runaway) discharges and during disruptions. The basic elements of the probe are YSO crystals which transform the energy of runaway electrons into visible light which is guided via optical fibres to photomultipliers. In order to obtain the energy distribution of runaways, the crystals are covered with layers of stainless steel (or tungsten in two earlier test versions) of different thicknesses. The final probe design has 9 crystals and can temporally and spectrally resolve electrons with energies between 4 MeV and 30 MeV. The probe is tested and absolutely calibrated at the linear electron accelerator ELBE in Rossendorf. The measurements are in good agreement with Monte Carlo simulations using the Geant4 code. The runaway transport in the presence of the internal and externally applied magnetic perturbations has been studied. The diffusion coefficient and the value of the magnetic fluctuation for runaways were derived as a function of B t . It was found that an increase of runaway losses from the plasma with the decreasing toroidal magnetic field is accompanied with a growth of the magnetic fluctuation in the plasma. The magnetic shielding picture could be confirmed which predicts that the runaway loss occurs predominantly for low energy runaways (few MeV) and considerably less for the high energy ones. In the case of the externally applied magnetic perturbations by means of the dynamic

Spectral measurements of runway electrons in the TEXTOR tokamak

Energy Technology Data Exchange (ETDEWEB)

Kudyakov, Timur

2009-07-22

The generation of multi-MeV runaway electrons is a well known effect related to the plasma disruptions in tokamaks. The runaway electrons can substantially reduce the lifetime of the future tokamak ITER. In this thesis physical properties of runaway electrons and their possible negative effects on ITER have been studied in the TEXTOR tokamak. A new diagnostic, a scanning probe, has been developed to provide direct measurements of the absolute number of runaway electrons coming from the plasma, its energy distribution and the related energy load in the material during low density (runaway) discharges and during disruptions. The basic elements of the probe are YSO crystals which transform the energy of runaway electrons into visible light which is guided via optical fibres to photomultipliers. In order to obtain the energy distribution of runaways, the crystals are covered with layers of stainless steel (or tungsten in two earlier test versions) of different thicknesses. The final probe design has 9 crystals and can temporally and spectrally resolve electrons with energies between 4 MeV and 30 MeV. The probe is tested and absolutely calibrated at the linear electron accelerator ELBE in Rossendorf. The measurements are in good agreement with Monte Carlo simulations using the Geant4 code. The runaway transport in the presence of the internal and externally applied magnetic perturbations has been studied. The diffusion coefficient and the value of the magnetic fluctuation for runaways were derived as a function of B{sub t}. It was found that an increase of runaway losses from the plasma with the decreasing toroidal magnetic field is accompanied with a growth of the magnetic fluctuation in the plasma. The magnetic shielding picture could be confirmed which predicts that the runaway loss occurs predominantly for low energy runaways (few MeV) and considerably less for the high energy ones. In the case of the externally applied magnetic perturbations by means of the dynamic

Beam Spot Measurement on a 400 keV Electron Accelerator

DEFF Research Database (Denmark)

Miller, Arne

1979-01-01

A line probe is used to measure the beam spot radius and beam divergence at a 400 keV ICT electron accelerator, and a method is shown for reducing the line probe data in order to get the radial function.......A line probe is used to measure the beam spot radius and beam divergence at a 400 keV ICT electron accelerator, and a method is shown for reducing the line probe data in order to get the radial function....

The beam energy measurement system for the Beijing electron-positron collider

International Nuclear Information System (INIS)

Abakumova, E.V.; Achasov, M.N.; Blinov, V.E.; Cai, X.; Dong, H.Y.; Fu, C.D.; Harris, F.A.; Kaminsky, V.V.; Krasnov, A.A.; Liu, Q.; Mo, X.H.; Muchnoi, N.Yu.; Nikolaev, I.B.; Qin, Q.; Qu, H.M.; Olsen, S.L.; Pyata, E.E.; Shamov, A.G.; Shen, C.P.; Todyshev, K.Yu.

2011-01-01

The beam energy measurement system (BEMS) for the upgraded Beijing electron-positron collider BEPC-II is described. The system is based on measuring the energies of Compton back-scattered photons. The relative systematic uncertainty of the electron and positron beam energy determination is estimated as 2×10 -5 . The relative uncertainty of the beam's energy spread is about 6%.

New technique for measurement of electron attachment to molecules

International Nuclear Information System (INIS)

Harding, T.W.

1984-01-01

One of the goals of this dissertation was to develop a faster method of measuring the attachment properties of molecules. An apparatus was successfully developed that employs a pair of coaxial cylindrical electrodes with the inner one serving also as a pulsed photoelectron source. An electron swarm is driven radially outward through a mixture of an attaching gas and a buffer gas. Both the electrons and resulting negative ions are detected as time-resolved currents by a cylindrical detector contained within the outer electrode as a Faraday cage. Data collection and analysis are handled by a minicomputer based data acquisition system with two independent digitizers. Data were obtained for oxygen in helium or nitrogen as a buffer gas and for sulfur dioxide in helium. Attaching gas percentage were generally below 1%. The electric field to number density ratio was in the range of 1.7 x 10 -19 to 3.8 X 10 -18 V cm 2 . Attachment coefficients were obtained firstly by treating the negative ion currents as a measure of electron attenuation through a gas mixture and secondly by reconstructing the spatial distribution of negative ions at the time of electron passage from the time-resolved currents

Measurement of centroid trajectory of Dragon-I electron beam

International Nuclear Information System (INIS)

Jiang Xiaoguo; Wang Yuan; Zhang Wenwei; Zhang Kaizhi; Li Jing; Li Chenggang; Yang Guojun

2005-01-01

The control of the electron beam in an intense current linear induction accelerator (LIA) is very important. The center position of the electron beam and the beam profile are two important parameters which should be measured accurately. The setup of a time-resolved measurement system and a data processing method for determining the beam center position are introduced for the purpose of obtaining Dragon-I electron beam trajectory including beam profile. The actual results show that the centroid position error can be controlled in one to two pixels. the time-resolved beam centroid trajectory of Dragon-I (18.5 MeV, 2 kA, 90 ns) is obtained recently in 10 ns interval, 3 ns exposure time with a multi-frame gated camera. The results show that the screw movement of the electron beam is mainly limited in an area with a radius of 0.5 mm and the time-resolved diameters of the beam are 8.4 mm, 8.8 mm, 8.5 mm, 9.3 mm and 7.6 mm. These results have provided a very important support to several research areas such as beam trajectory tuning and beam transmission. (authors)

Measurements of hot electrons in the Extrap T1 reversed-field pinch

International Nuclear Information System (INIS)

Welander, A.; Bergsaaker, H.

1998-01-01

The presence of an anisotropic energetic electron population in the edge region is a characteristic feature of reversed-field pinch (RFP) plasmas. In the Extrap T1 RFP, the anisotropic, parallel heat flux in the edge region measured by calorimetry was typically several hundred MWm -2 . To gain more insight into the origin of the hot electron component and to achieve time resolution of the hot electron flow during the discharge, a target probe with a soft x-ray monitor was designed, calibrated and implemented. The x-ray emission from the target was measured with a surface barrier detector covered with a set of different x-ray filters to achieve energy resolution. A calibration in the range 0.5-2 keV electron energy was performed on the same target and detector assembly using a LaB 6 cathode electron gun. The calibration data are interpolated and extrapolated numerically. A directional asymmetry of more than a factor of 100 for the higher energy electrons is observed. The hot electrons are estimated to constitute 10% of the total electron density at the edge and their energy distribution is approximated by a half-Maxwellian with a temperature slightly higher than the central electron temperature. Scalings with plasma current, as well as correlations with local Hα measurements and radial dependences, are presented. (author)

Electron temperature measurements in lowdensity plasmas by helium spectroscopy

International Nuclear Information System (INIS)

Brenning, N.

1977-09-01

This method to use relative intensities of singlet and triplet lines of neutral helium to measure electron temperature in low-density plasmas is examined. Calculations from measured and theoretical data about transitions in neutral helium are carried out and compared to experimental results. It is found that relative intensities of singlet and triplet lines from neutral helium only can be used for TE determination in low-density, short-duration plasmas. The most important limiting processes are excitation from the metastable 2 3 S level and excitation transfer in collisions between electrons and excited helium atoms. An evaluation method is suggested, which minimizes the effect of these processes. (author)

MICROWAVE NOISE MEASUREMENT OF ELECTRON TEMPERATURES IN AFTERGLOW PLASMAS

Energy Technology Data Exchange (ETDEWEB)

Leiby, Jr., C. C.; McBee, W. D.

1963-10-15

Transient electron temperatures in afterglow plasmas were determined for He (5 and 10 torr), Ne, and Ne plus or minus 5% Ar (2.4 and 24 torr) by combining measurements of plasma microwave noise power, and plasma reflectivity and absorptivity. Use of a low-noise parametric preamplifier permitted continuous detection during the afterglow of noise power at 5.5 Bc in a 1 Mc bandwidth. Electron temperature decays were a function of pressure and gas but were slower than predicted by electron energy loss mechanisms. The addition of argon altered the electron density decay in the neon afterglow but the electron temperature decay was not appreciably changed. Resonances in detected noise power vs time in the afterglow were observed for two of the three plasma waveguide geometries studied. These resonances correlate with observed resonances in absorptivity and occur over the same range of electron densities for a given geometry independent of gas type and pressure. (auth)

Portable audio electronics for impedance-based measurements in microfluidics

International Nuclear Information System (INIS)

Wood, Paul; Sinton, David

2010-01-01

We demonstrate the use of audio electronics-based signals to perform on-chip electrochemical measurements. Cell phones and portable music players are examples of consumer electronics that are easily operated and are ubiquitous worldwide. Audio output (play) and input (record) signals are voltage based and contain frequency and amplitude information. A cell phone, laptop soundcard and two compact audio players are compared with respect to frequency response; the laptop soundcard provides the most uniform frequency response, while the cell phone performance is found to be insufficient. The audio signals in the common portable music players and laptop soundcard operate in the range of 20 Hz to 20 kHz and are found to be applicable, as voltage input and output signals, to impedance-based electrochemical measurements in microfluidic systems. Validated impedance-based measurements of concentration (0.1–50 mM), flow rate (2–120 µL min −1 ) and particle detection (32 µm diameter) are demonstrated. The prevailing, lossless, wave audio file format is found to be suitable for data transmission to and from external sources, such as a centralized lab, and the cost of all hardware (in addition to audio devices) is ∼10 USD. The utility demonstrated here, in combination with the ubiquitous nature of portable audio electronics, presents new opportunities for impedance-based measurements in portable microfluidic systems. (technical note)

Studies of suprathermal emission due to cyclotron-electronic heating of the tokamak TCV plasma; Etudes du rayonnement suprathermique emis lors du chauffage cyclotronique electronique du plasma du tokamak TCV

Energy Technology Data Exchange (ETDEWEB)

Blanchard, P

2002-07-01

Photo sensitization of wide band gap semiconductors is used in a wide range of application like silver halide photography and xerography. The development of a new type of solar cells, based on the sensitization of meso porous metal oxide films by panchromatic dyes, has triggered a lot of fundamental research on electron transfer dynamics. Upon excitation, the sensitizer transfers an electron in the conduction band of the semiconductor. Recombination of the charge separated state is prevented by the fast regeneration of the dye by an electron donor present in solution. Until recently, most of the work in this area has been focused on the competition between the recombination and the regeneration processes, which take place in the nanosecond to millisecond regime. With the development of solid-state femtosecond laser, the measurement of the dynamics of the first electron transfer step occurring in the solar cell has become possible . Electron injection from ruthenium(Il) poly pyridyl complexes into titanium dioxide has been found to occur with a poly exponential rate, with time constants ranging from < 100 fs up to > 10 ps. In spite of the lately acquired capacity to measure the dynamics of these reactions, the physical meaning of this poly exponential kinetics and the factors that can influence this process are still poorly understood. In this work, the development of a new femtosecond pump-probe spectrometer, intended to monitor the ultrafast dynamics of electron injection, is presented. The study of this process requires an excellent temporal resolution and a large wavelength tunability to be able to excite a great variety of dyes and to probe the different products of the reaction. These specifications were met using the latest progress made in optical parametric amplification, which allowed the construction of a versatile experimental set-up. The interfacing by computer of the different devices used during the experiments increase the ease of use of the set

Unique electron polarimeter analyzing power comparison and precision spin-based energy measurement

International Nuclear Information System (INIS)

Joseph Grames; Charles Sinclair; Joseph Mitchell; Eugene Chudakov; Howard Fenker; Arne Freyberger; Douglas Higinbotham; Poelker, B.; Michael Steigerwald; Michael Tiefenback; Christian Cavata; Stephanie Escoffier; Frederic Marie; Thierry Pussieux; Pascal Vernin; Samuel Danagoulian; Kahanawita Dharmawardane; Renee Fatemi; Kyungseon Joo; Markus Zeier; Viktor Gorbenko; Rakhsha Nasseripour; Brian Raue; Riad Suleiman; Benedikt Zihlmann

2004-01-01

Precision measurements of the relative analyzing powers of five electron beam polarimeters, based on Compton, Moller, and Mott scattering, have been performed using the CEBAF accelerator at the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory). A Wien filter in the 100 keV beamline of the injector was used to vary the electron spin orientation exiting the injector. High statistical precision measurements of the scattering asymmetry as a function of the spin orientation were made with each polarimeter. Since each polarimeter receives beam with the same magnitude of polarization, these asymmetry measurements permit a high statistical precision comparison of the relative analyzing powers of the five polarimeters. This is the first time a precise comparison of the analyzing powers of Compton, Moller, and Mott scattering polarimeters has been made. Statistically significant disagreements among the values of the beam polarization calculated from the asymmetry measurements made with each polarimeter reveal either errors in the values of the analyzing power, or failure to correctly include all systematic effects. The measurements reported here represent a first step toward understanding the systematic effects of these electron polarimeters. Such studies are necessary to realize high absolute accuracy (ca. 1%) electron polarization measurements, as required for some parity violation measurements planned at Jefferson Laboratory. Finally, a comparison of the value of the spin orientation exiting the injector that provides maximum longitudinal polarization in each experimental hall leads to an independent and very precise (better than 10-4) absolute measurement of the final electron beam energy

Emittance Measurements from a Laser Driven Electron Injector

CERN Document Server

Reis, D

2003-01-01

The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 (angstrom), the LCLS requires an electron injector that can produce an electron beam with approximately 1 pi mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the ...

Electronics/avionics integrity - Definition, measurement and improvement

Science.gov (United States)

Kolarik, W.; Rasty, J.; Chen, M.; Kim, Y.

The authors report on the results obtained from an extensive, three-fold research project: (1) to search the open quality and reliability literature for documented information relative to electronics/avionics integrity; (2) to interpret and evaluate the literature as to significant concepts, strategies, and tools appropriate for use in electronics/avionics product and process integrity efforts; and (3) to develop a list of critical findings and recommendations that will lead to significant progress in product integrity definition, measurement, modeling, and improvements. The research consisted of examining a broad range of trade journals, scientific journals, and technical reports, as well as face-to-face discussions with reliability professionals. Ten significant recommendations have been supported by the research work.

Determination of electron bunch shape using transition radiation and phase-energy measurements

International Nuclear Information System (INIS)

Crosson, E.R.; Berryman, K.W.; Richman, B.A.

1995-01-01

We present data comparing microbunch temporal information obtained from electron beam phase-energy measurements with that obtained from transition radiation auto-correlation measurements. The data was taken to resolve some of the ambiguities in previous transition radiation results. By measuring the energy spectrum of the electron beam as a function of its phase relative to the accelerating field, phase-energy information was extracted. This data was analyzed using tomographic techniques to reconstruct the phase-space distribution assuming an electron energy dependence of E(var-phi) = E o + E acc cos(var-phi), where E o is the energy of an electron entering the field, E acc is the peak energy gain, and var-phi is the phase between the crest of the RF wave and an electron. Temporal information about the beam was obtained from the phase space distribution by taking the one dimensional projection along the time axis. We discuss the use of this technique to verify other transition radiation analysis methods

Determination of electron bunch shape using transition radiation and phase-energy measurements

Energy Technology Data Exchange (ETDEWEB)

Crosson, E.R.; Berryman, K.W.; Richman, B.A. [Stanford Univ., CA (United States)] [and others

1995-12-31

We present data comparing microbunch temporal information obtained from electron beam phase-energy measurements with that obtained from transition radiation auto-correlation measurements. The data was taken to resolve some of the ambiguities in previous transition radiation results. By measuring the energy spectrum of the electron beam as a function of its phase relative to the accelerating field, phase-energy information was extracted. This data was analyzed using tomographic techniques to reconstruct the phase-space distribution assuming an electron energy dependence of E({var_phi}) = E{sub o} + E{sub acc}cos({var_phi}), where E{sub o} is the energy of an electron entering the field, E{sub acc} is the peak energy gain, and {var_phi} is the phase between the crest of the RF wave and an electron. Temporal information about the beam was obtained from the phase space distribution by taking the one dimensional projection along the time axis. We discuss the use of this technique to verify other transition radiation analysis methods.

SU-F-T-84: Measurement and Monte-Carlo Simulation of Electron Phase Spaces Using a Wide Angle Magnetic Electron Spectrometer

Energy Technology Data Exchange (ETDEWEB)

Englbrecht, F; Lindner, F; Bin, J; Wislsperger, A; Reiner, M; Kamp, F; Belka, C; Dedes, G; Schreiber, J; Parodi, K [LMU Munich, Munich, Bavaria (Germany)

2016-06-15

Purpose: To measure and simulate well-defined electron spectra using a linear accelerator and a permanent-magnetic wide-angle spectrometer to test the performance of a novel reconstruction algorithm for retrieval of unknown electron-sources, in view of application to diagnostics of laser-driven particle acceleration. Methods: Six electron energies (6, 9, 12, 15, 18 and 21 MeV, 40cm × 40cm field-size) delivered by a Siemens Oncor linear accelerator were recorded using a permanent-magnetic wide-angle electron spectrometer (150mT) with a one dimensional slit (0.2mm × 5cm). Two dimensional maps representing beam-energy and entrance-position along the slit were measured using different scintillating screens, read by an online CMOS detector of high resolution (0.048mm × 0.048mm pixels) and large field of view (5cm × 10cm). Measured energy-slit position maps were compared to forward FLUKA simulations of electron transport through the spectrometer, starting from IAEA phase-spaces of the accelerator. The latter ones were validated against measured depth-dose and lateral profiles in water. Agreement of forward simulation and measurement was quantified in terms of position and shape of the signal distribution on the detector. Results: Measured depth-dose distributions and lateral profiles in the water phantom showed good agreement with forward simulations of IAEA phase-spaces, thus supporting usage of this simulation source in the study. Measured energy-slit position maps and those obtained by forward Monte-Carlo simulations showed satisfactory agreement in shape and position. Conclusion: Well-defined electron beams of known energy and shape will provide an ideal scenario to study the performance of a novel reconstruction algorithm using measured and simulated signal. Future work will increase the stability and convergence of the reconstruction-algorithm for unknown electron sources, towards final application to the electrons which drive the interaction of TW-class laser

Description of the plasma diagnostics package (PDP) for the OSS-1 Shuttle mission and JSC plasma chamber test in conjunction with the fast pulse electron gun (FPEG)

Science.gov (United States)

Shawhan, S. D.

1982-01-01

The objectives, equipment, and techniques for the plasma diagnostics package (PDP) carried by the OSS-1 instrument payload of the STS-4 and scheduled for the Spacelab-2 mission are described. The goals of the first flight were to examine the Orbiter-magnetoplasma interactions by measuring the electric and magnetic field strengths, the ionized particle wakes, and the generated waves. The RMS was employed to lift the unit out of the bay in order to allow characterization of the fields, EM interference, and plasma contamination within 15 m of the Orbiter. The PDP will also be used to examine plasma depletion, chemical reaction rates, waves, and energized plasma produced by firing of the Orbiter thrusters. Operation of the PDP was carried out in the NASA Space Environment Simulation Laboratory test chamber, where the PDP was used to assay the fields, fluxes, wave amplitudes, and particle energy spectra. The PDP instrumentation is also capable of detecting thermal ions, thermal electrons suprathermal particles, VHF/UHF EMI levels, and the S-band field strength.

Uncertainties of size measurements in electron microscopy characterization of nanomaterials in foods

DEFF Research Database (Denmark)

Dudkiewicz, Agnieszka; Boxall, Alistair B. A.; Chaudhry, Qasim

2015-01-01

Electron microscopy is a recognized standard tool for nanomaterial characterization, and recommended by the European Food Safety Authority for the size measurement of nanomaterials in food. Despite this, little data have been published assessing the reliability of the method, especially for size...... measurement of nanomaterials characterized by a broad size distribution and/or added to food matrices. This study is a thorough investigation of the measurement uncertainty when applying electron microscopy for size measurement of engineered nanomaterials in foods. Our results show that the number of measured...

Collaborative research: Dynamics of electrostatic solitary waves and their effects on current layers

Energy Technology Data Exchange (ETDEWEB)

Chen, Li-Jen

2014-04-18

by the Cluster spacecraft and those measured in LAPD. One of the similarities in the characteristics of ESWs observed in space and in LAPD is that the time duration tends to be approximately the inverse of the electron plasma frequency [Pickett et al., 2009b]. Discovery of suprathermal electron bursts inside a series of magnetic islands: Our effort in examining the roles of ESWs in reconnection current layers resulted in the serendipitous discovery that was published in Nature Physics. In earth’s magnetosphere, we observed through the measurements from the four Cluster spacecraft, a series of magnetic islands and suprathermal electron bursts within the islands. The islands were identified to be effectively acceleration sites for electrons [Chen et al., 2008, 2009].

Electron momentum density measurements by means of positron annihilation and Compton spectroscopy

International Nuclear Information System (INIS)

Gerber, W.; Dlubek, G.; Marx, U.; Bruemmer, O.; Prautzsch, J.

1982-01-01

The electron momentum density is measured applying positron annihilation and Compton spectroscopy in order to get information about electron wave functions. Compton spectroscopic measurements of Pd-Ag and Cu-Zn alloy systems are carried out taking into account crystal structure, mixability, and order state. Three-dimensional momentum densities of silicon are determined in order to get better information about its electronic structure. The momentum density and the spin density of ferromagnetic nickel are investigated using angular correlation curves

Measurements of hot electrons in the Extrap T1 reversed-field pinch

Science.gov (United States)

Welander, A.; Bergsåker, H.

1998-02-01

The presence of an anisotropic energetic electron population in the edge region is a characteristic feature of reversed-field pinch (RFP) plasmas. In the Extrap T1 RFP, the anisotropic, parallel heat flux in the edge region measured by calorimetry was typically several hundred 0741-3335/40/2/011/img1. To gain more insight into the origin of the hot electron component and to achieve time resolution of the hot electron flow during the discharge, a target probe with a soft x-ray monitor was designed, calibrated and implemented. The x-ray emission from the target was measured with a surface barrier detector covered with a set of different x-ray filters to achieve energy resolution. A calibration in the range 0.5-2 keV electron energy was performed on the same target and detector assembly using a 0741-3335/40/2/011/img2 cathode electron gun. The calibration data are interpolated and extrapolated numerically. A directional asymmetry of more than a factor of 100 for the higher energy electrons is observed. The hot electrons are estimated to constitute 10% of the total electron density at the edge and their energy distribution is approximated by a half-Maxwellian with a temperature slightly higher than the central electron temperature. Scalings with plasma current, as well as correlations with local 0741-3335/40/2/011/img3 measurements and radial dependences, are presented.

Measurement of electron density and electron temperature of a cascaded arc plasma using laser Thomson scattering compared to an optical emission spectroscopic approach

Science.gov (United States)

Yong, WANG; Cong, LI; Jielin, SHI; Xingwei, WU; Hongbin, DING

2017-11-01

As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering (LTS) system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5 × 1019 m-3 to 7.1 × 1020 m-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison, an optical emission spectroscopy (OES) system was established as well. The results showed that the electron excitation temperature (configuration temperature) measured by OES is significantly higher than the electron temperature (kinetic electron temperature) measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium (LTE). This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.

Multi-Point Measurements to Characterize Radiation Belt Electron Precipitation Loss

Science.gov (United States)

Blum, L. W.

2017-12-01

Multipoint measurements in the inner magnetosphere allow the spatial and temporal evolution of various particle populations and wave modes to be disentangled. To better characterize and quantify radiation belt precipitation loss, we utilize multi-point measurements both to study precipitating electrons directly as well as the potential drivers of this loss process. Magnetically conjugate CubeSat and balloon measurements are combined to estimate of the temporal and spatial characteristics of dusk-side precipitation features and quantify loss due to these events. To then understand the drivers of precipitation events, and what determines their spatial structure, we utilize measurements from the dual Van Allen Probes to estimate spatial and temporal scales of various wave modes in the inner magnetosphere, and compare these to precipitation characteristics. The structure, timing, and spatial extent of waves are compared to those of MeV electron precipitation during a few individual events to determine when and where EMIC waves cause radiation belt electron precipitation. Magnetically conjugate measurements provide observational support of the theoretical picture of duskside interaction of EMIC waves and MeV electrons leading to radiation belt loss. Finally, understanding the drivers controlling the spatial scales of wave activity in the inner magnetosphere is critical for uncovering the underlying physics behind the wave generation as well as for better predicting where and when waves will be present. Again using multipoint measurements from the Van Allen Probes, we estimate the spatial and temporal extents and evolution of plasma structures and their gradients in the inner magnetosphere, to better understand the drivers of magnetospheric wave characteristic scales. In particular, we focus on EMIC waves and the plasma parameters important for their growth, namely cold plasma density and cool and warm ion density, anisotropy, and composition.

Electron beam potential measurements on an inductive-store, opening-switch accelerator

International Nuclear Information System (INIS)

Riordan, J.C.; Goyer, J.R.; Kortbawi, D.; Meachum, J.S.; Mendenhall, R.S.; Roth, I.S.

1993-01-01

Direct measurement of the accelerating potential in a relativistic electron beam accelerator is difficult, particularly when the diode is downstream from a plasma opening switch. An indirect potential measurement can be obtained from the high energy tail of the bremsstrahlung spectrum generated as the electron beam strikes the anode. The authors' time-resolved spectrometer contains 7 silicon pin diode detectors filtered with 2 to 15 mm of lead to span an electron energy range of 0.5 to 2 MeV. A Monte-Carlo transport code was used to provide calibration curves, and the resulting potential measurements have been confirmed in experiments on the PITHON accelerator. The spectrometer has recently been deployed on PM1, an inductive-store, opening-switch testbed. The diode voltage measurements from the spectrometer are in good agreement with the diode voltage measured upstream and corrected using transmission line relations. The x-ray signal and spectral voltage rise 10 ns later than the corrected electrical voltage, however, indicating plasma motion between the opening switch and the diode

Understanding the Driver of Energetic Electron Precipitation Using Coordinated Multi-Satellite Measurements

Science.gov (United States)

Capannolo, L.; Li, W.; Ma, Q.

2017-12-01

Electron precipitation into the upper atmosphere is one of the important loss mechanisms in the Earth's inner magnetosphere. Various magnetospheric plasma waves (i.e., chorus, plasmaspheric hiss, electromagnetic ion cyclotron waves, etc.) play an important role in scattering energetic electrons into the loss cone, thus enhance ionization in the upper atmosphere and affect ring current and radiation belt dynamics. The present study evaluates conjunction events where low-earth-orbiting satellites (twin AeroCube-6) and near-equatorial satellites (twin Van Allen Probes) are located roughly along the same magnetic field line. By analyzing electron flux variation at various energies (> 35 keV) measured by AeroCube-6 and wave and electron measurements by Van Allen Probes, together with quasilinear diffusion theory and modeling, we determine the physical process of driving the observed energetic electron precipitation for the identified electron precipitation events. Moreover, the twin AeroCube-6 also helps us understand the spatiotemporal effect and constrain the coherent size of each electron precipitation event.

Direct measurement of electron density in microdischarge at atmospheric pressure by Stark broadening

International Nuclear Information System (INIS)

Dong Lifang; Ran Junxia; Mao Zhiguo

2005-01-01

We present a method and results for measurement of electron density in atmospheric-pressure dielectric barrier discharge. The electron density of microdischarge in atmospheric pressure argon is measured by using the spectral line profile method. The asymmetrical deconvolution is used to obtain Stark broadening. The results show that the electron density in single filamentary microdischarge at atmospheric pressure argon is 3.05x10 15 cm -3 if the electron temperature is 10,000 K. The result is in good agreement with the simulation. The electron density in dielectric barrier discharge increases with the increase of applied voltage

The system design of TRIO cinema Mission

Science.gov (United States)

Jin, Ho; Seon, Jongho; Kim, Khan-Hyuk; Lee, Dong-Hun; Kim, Kap-Sung; Lin, Robert; Parks, George; Tindall, Craig; Horbury, T. S.; Larson, Davin; Sample, John

TRIO (Triplet Ionospheric Observatory) CINEMA ( Cubesat for Ion, Neutral, Electron, MAg-netic fields) is a space science mission with three identical cubesats. The main scientific objec-tives are a multi-observation of ionospheric ENA (Energetic Neutral Atom) imaging, ionospheric signature of suprathermal electrons and ions and complementary measurements of magnetic fields for particle data. For this, Main payloads consist of a suprathermal electron, ion, neutral (STEIN) instrument and a 3-axis magnetometer of magnetoresistive sensors. The CINEMA is a 3-unit CubeSat, which translates to a 10 cm x 10 cm x 30 cm in volume and no more than four kilograms in mass. An attitude control system (ACS) uses torque coils, a sun sensor and the magnetometers and spin CINEMA spcaecraft 4 rpm with the spin axis perpendicular to the ecliptic plane. CINEMA will be placed into a high inclination low earth orbit that crosses the auroral zone and cusp. Three institutes are collaborating to develop CINEMA cubesats: i) two cubesats by Kyung Hee University (KHU) under their World Class University (WCU) program, ii) one cubesat by UC Berkeley under the NSF support, and iii) three magnetometers are provide by Imperial College, respectively. In this paper, we describe the system design and their performance of TR IO cinema mission. TRIO cinema's development of miniature in-strument and spacecraft spinning operation will play an important role for future nanosatellite space missions

Influence of Magnetic Topology on Mars' Ionospheric Structure

Science.gov (United States)

Adams, D.; Xu, S.; Mitchell, D. L.; Fillingim, M. O.; Lillis, R. J.; Andersson, L.; Fowler, C. M.; Benna, M.; Connerney, J. E. P.; Elrod, M. K.; Girazian, Z.; Vogt, M.

2017-12-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been in Mars' orbit since September 2014 (>1 Mars year), and has collected particle and field data within the ionosphere over wide ranges of altitudes, latitudes, and local times. This study uses MAVEN data to (1) analyze the influence of magnetic topology on the day-side ionosphere and (2) identify the sources of the night-side ionosphere. On the day side, magnetic strength and elevation angle are commonly used as proxies for magnetic topology. In this study, we use pitch-angle-resolved suprathermal electron measurements by the Solar Wind Electron Analyzer (SWEA) to directly deduce the magnetic topology instead of using a proxy. On the night side, the main sources of ionospheric plasma are bulk transport and plasma pressure gradient flow from the day side, as well as in situ production by electron impact ionization (EII). Plasma transport at Mars is complicated by the presence of intense crustal magnetic fields. Closed crustal magnetic fields form isolated plasma environments ("miniature magnetospheres") that inhibit external sources of cold ionospheric plasma as well as suprathermal (ionizing) electrons. Inside these closed magnetic loops, we study how the plasma evolves with bulk flow transport as the only source. By comparing closed and non-closed magnetic configurations, the effects of pressure gradient flow and EII can be distinguished. Finally, the densities of O2+, O+, and NO+, as measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS), are examined. Inside miniature magnetospheres on the night side, the abundances of these species are found to be primarily controlled by the different recombination rates, as there is little plasma created within these regions by EII or transported from the neighboring regions by plasma pressure gradient flow.

Beam lifetime measurement and analysis in Indus-2 electron ...

Indian Academy of Sciences (India)

In this paper, the beam lifetime measurement and its theoretical analysis are presented using measured vacuum pressure and applied radio frequency (RF) cavity voltage in Indus-2 electron storage ring at 2 GeV beam energy. Experimental studies of the effect of RF cavity voltage and bunched beam filling pattern on beam ...

Measurement of electron blockage factors for mamma scars

International Nuclear Information System (INIS)

Marques Fraguela, E.; Suero Rodrigo, M. A.

2011-01-01

Pencil Beam algorithm XiO CMS scheduler uses the applicator factor, instead of blocking factor in the calculation of monitor units (MU) shaped electron fields. This feature makes the algorithm for calculating an input field the same dose in the beam axis than it would if it were not blocked. It should, therefore, to correct the UM that provides the planner by a factor. The blocks used in electron treatment of the surgical mamma cancers often have a narrow elongated shape following the contour of the scar. Such openings have difficulty measuring the blocking factor with plane-parallel chambers recommended by national and international protocols (eg PTW Roos 34 001) as being so narrow that sometimes the camera is not completely irradiated. In this paper, we study the possibility of using a PTW 30010 Farmer cylindrical chamber for measuring the blocking factor of such openings.

Rocket measurement of auroral electron fluxes associated with field-aligned currents

International Nuclear Information System (INIS)

Pazich, P.M.; Anderson, H.R.

1975-01-01

A Nike-Tomahawk rocket was instrumented with a vector magnetometer and an array of particle detectors including an electron and proton energyspectrometer covering the energy range 0.5-20 keV in seven fixed intervals and measuring the pitch angle distribution from 0degree to 180degree as the rocket spun. The payload was launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972, over a bright auroral band that evidently was the poleward electron aurora, beyond the trapping boundary. An upper limit to the measured proton flux was 10 6 /cm 2 s sr keV. The energy spectrum of the electron flux measured during passage over the visible aurora always exhibited a peak within the measured energy range. During passage over the brighter auroral forms the peak shifted from approx.3 to approx.10 keV, the pitch angle distribution became peaked along B, and the intensity increased. Maximum fluxes of approx.3times10 8 el/cm 2 s sr keV were seen over the aurora, which reached approx.60 kR of lambda5577. The electron flux in regions of maximum flux tended to be the most field-aligned in the energy interval showing the highest intensity

Laser diagnostics of H- formation in a magnetic multicusp ion source

International Nuclear Information System (INIS)

Young, A.T.; Chen, P.; Kunkel, W.B.; Leung, K.N.; Li, C.Y.; Stutzin, G.C.

1991-05-01

The populations of ground electronic state atomic hydrogen and ground electronic state, vibrationally-rotationally excited hydrogen molecules in a negative hydrogen ion source discharge have been measured using vacuum ultraviolet (VUV) laser absorption spectroscopy. Vibrational states up to v=8 and rotational levels as high as J=15 have been measured. The measurements have been made under a range of discharge conditions. The complete vibrational population distribution for v=1-8, J=1 has been obtained. The vibrational distribution appears to be thermalized and does not exhibit a ''plateau'' at the higher vibrational levels, in contrast to most models of this system. In contrast, the high rotational states are populated suprathermally. These determinations indicate that rotationally excited molecules may play an important role in the production of H minus in these sources. 5 refs., 5 figs

Extracting Wair from the electron beam measurements of Domen and Lamperti.

Science.gov (United States)

Tessier, Frédéric; Cojocaru, Claudiu D; Ross, Carl K

2018-01-01

The average energy expended by an energetic electron to create an ion pair in dry air, W air , is a key quantity in radiation dosimetry. Although W air is well established for electron energies up to about 3 MeV, there is limited data for higher energies. The measurements by Domen and Lamperti [Med. Phys. 3, 294-301 (1976)] using electron beams in the energy range from 15 to 50 MeV can, in principle, be used to deduce values for W air , if the electron stopping power of graphite and air are known. A previous analysis of these data revealed an anomalous variation of 2% in W air as a function of the electron energy. We use Monte Carlo simulation techniques to reanalyze the original data and obtain new estimates for W air , and to investigate the source of the reported anomaly. Domen and Lamperti (DL) reported the ratio of the response of a graphite calorimeter to that of a graphite ionization chamber for broad beams of electrons with energies between 15 and 50 MeV and at different depths in graphite (including depths well beyond the range of the primary electrons, i.e., in the bremsstrahlung photon regime). Using a detailed EGSnrc model of the DL apparatus, as well as up-to-date stopping powers, we compute the dose ratio between the ionization chamber cavity and the calorimeter core, for plane-parallel electron beams. This dose ratio, multiplied by the DL measured ratio, provides a direct estimate for W air . Despite an improved analysis of the original work, the extracted values of W air still exhibit an increase as the mean electron energy at the point of measurement decreases below about 15 MeV. This anomalous trend is dubious physically, and inconsistent with extensive data for W air obtained at lower energies. A thorough sensitivity analysis indicates that this trend is unlikely to stem from errors in extrapolation and correction procedures, uncertainties in electron stopping powers, or bias in calorimetry or ionization chamber measurements. However, we find

Temperature dependence of electron mean free path in molybdenum from ultrasonic measurements

Energy Technology Data Exchange (ETDEWEB)

Almond, D P; Detwiler, D A; Rayne, J A [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA)

1975-09-08

The temperature dependence of the electronic mean free path in molybdenum has been obtained from ultrasonic attenuation measurements.For temperature up to 30 K a T/sup -2/ law is followed suggesting the importance of electron-electron scattering in the attenuation mechanism.

Precision Electron Density Measurements in the SSX MHD Wind Tunnel

Science.gov (United States)

Suen-Lewis, Emma M.; Barbano, Luke J.; Shrock, Jaron E.; Kaur, Manjit; Schaffner, David A.; Brown, Michael R.

2017-10-01

We characterize fluctuations of the line averaged electron density of Taylor states produced by the magnetized coaxial plasma gun of the SSX device using a 632.8 nm HeNe laser interferometer. The analysis method uses the electron density dependence of the refractive index of the plasma to determine the electron density of the Taylor states. Typical magnetic field and density values in the SSX device approach about B ≅ 0.3 T and n = 0 . 4 ×1016 cm-3 . Analysis is improved from previous density measurement methods by developing a post-processing method to remove relative phase error between interferometer outputs and to account for approximately linear phase drift due to low-frequency mechanical vibrations of the interferometer. Precision density measurements coupled with local measurements of the magnetic field will allow us to characterize the wave composition of SSX plasma via density vs. magnetic field correlation analysis, and compare the wave composition of SSX plasma with that of the solar wind. Preliminary results indicate that density and magnetic field appear negatively correlated. Work supported by DOE ARPA-E ALPHA program.

The measurement of internal conversion electrons of selected nuclei: A physics undergraduate laboratory experience

International Nuclear Information System (INIS)

Nagy, P.; Duggan, J.L.; Desmarais, D.

1992-01-01

Thin sources are now commercially available for a wide variety of isotopes that have measurable internal conversion coefficients. The authors have used standard surface barrier detectors, NIM electronics, and a personal computer analyzer to measure conversion electrons from a few of these sources. Conversion electrons energy and intensity were measured for 113 Sn, 133 Ba, 137 Cs, and 207 Bi. From the measured spectra the innershell binding energies of the K ampersand L Shell electrons from the daughter nuclei were determined and compared to theory. The relative conversion coefficients a k /a L and the K/L ration were also measured. The spin and parity change of the transitions will also be assigned based on the selection rules of the transitions

Comparison of Electron Imaging Modes for Dimensional Measurements in the Scanning Electron Microscope.

Science.gov (United States)

Postek, Michael T; Vladár, András E; Villarrubia, John S; Muto, Atsushi

2016-08-01

Dimensional measurements from secondary electron (SE) images were compared with those from backscattered electron (BSE) and low-loss electron (LLE) images. With the commonly used 50% threshold criterion, the lines consistently appeared larger in the SE images. As the images were acquired simultaneously by an instrument with the capability to operate detectors for both signals at the same time, the differences cannot be explained by the assumption that contamination or drift between images affected the SE, BSE, or LLE images differently. Simulations with JMONSEL, an electron microscope simulator, indicate that the nanometer-scale differences observed on this sample can be explained by the different convolution effects of a beam with finite size on signals with different symmetry (the SE signal's characteristic peak versus the BSE or LLE signal's characteristic step). This effect is too small to explain the >100 nm discrepancies that were observed in earlier work on different samples. Additional modeling indicates that those discrepancies can be explained by the much larger sidewall angles of the earlier samples, coupled with the different response of SE versus BSE/LLE profiles to such wall angles.

Electron temperature measurement of tungsten inert gas arcs

International Nuclear Information System (INIS)

Tanaka, Manabu; Tashiro, Shinichi

2008-01-01

In order to make clear the physical grounds of deviations from LTE (Local Thermodynamic Equilibrium) in the atmospheric helium TIG arcs electron temperature and LTE temperature obtained from electron number density were measured by using of line-profile analysis of the laser scattering method without an assumption of LTE. The experimental results showed that in comparison with the argon TIG arcs, the region where a deviation from LTE occurs tends to expand in higher arc current because the plasma reaches the similar state to LTE within shorter distance from the cathode due to the slower cathode jet velocity

Measurement of peripheral electron temperature by electron cyclotron emission during the H-mode transition in JFT-2M tokamak

International Nuclear Information System (INIS)

Hoshino, Katsumichi; Yamamoto, Takumi; Kawashima, Hisato

1987-01-01

Time evolution and profile of peripheral electron temperature during the H-mode like transition in a tokamak plasma is measured using the second and third harmonic of electron cyclotron emission (ECE). The so called ''H-mode'' state which has good particle/energy confinement is characterized by sudden decrease in the spectral line intensity of deuterium molecule. Such a sudden decrease in the line intensity of D α with good energy confinement is found not only in divertor discharges, but also in limiter dischargs in JFT-2M tokamak. It is found by the measurement of ECE that the peripheral electron temperature suddenly increases in both of such phases. The relation between H-transition and the peripheral electron temperature or its profile is investigated. (author)

Electron temperature measurement by a helium line intensity ratio method in helicon plasmas

International Nuclear Information System (INIS)

Boivin, R.F.; Kline, J.L.; Scime, E.E.

2001-01-01

Electron temperature measurements in helicon plasmas are difficult. The presence of intense rf fields in the plasma complicates the interpretation of Langmuir probe measurements. Furthermore, the non-negligible ion temperature in the plasma considerably shortens the lifetime of conventional Langmuir probes. A spectroscopic technique based on the relative intensities of neutral helium lines is used to measure the electron temperature in the HELIX (Hot hELicon eXperiment) plasma [P. A. Keiter et al., Phys. Plasmas 4, 2741 (1997)]. This nonintrusive diagnostic is based on the fact that electron impact excitation rate coefficients for helium singlet and triplet states differ as a function of the electron temperature. The different aspects related to the validity of this technique to measure the electron temperature in rf generated plasmas are discussed in this paper. At low plasma density (n e ≤10 11 cm -3 ), this diagnostic is believed to be very reliable since the population of the emitting level can be easily estimated with reasonable accuracy by assuming that all excitation originates from the ground state (steady-state corona model). At higher density, secondary processes (excitation transfer, excitation from metastable, cascading) become more important and a more complex collisional radiative model must be used to predict the electron temperature. In this work, different helium transitions are examined and a suitable transition pair is identified. For an electron temperature of 10 eV, the line ratio is measured as a function of plasma density and compared to values predicted by models. The measured line ratio function is in good agreement with theory and the data suggest that the excitation transfer is the dominant secondary process in high-density plasmas

Measurements of electron attachment by oxygen molecule in proportional counter

Energy Technology Data Exchange (ETDEWEB)

Tosaki, M., E-mail: tosaki.mitsuo.3v@kyoto-u.ac.jp [Radioisotope Research Center, Kyoto University, Kyoto 606-8501 (Japan); Kawano, T. [National Institute for Fusion Science, 322-6 Oroshi, Toki 509-5292 (Japan); Isozumi, Y. [Radioisotope Research Center, Kyoto University, Kyoto 606-8501 (Japan)

2013-11-15

We present pulse height measurements for 5-keV Auger electrons from a radioactive {sup 55}Fe source mounted at the inner cathode surface of cylindrical proportional counter, which is operated with CH{sub 4} admixed dry air or N{sub 2}. A clear shift of the pulse height has been observed by varying the amount of the admixtures; the number of electrons, created in the primary ionization by Auger electrons, is decreased by the electron attachment of the admixtures during their drift from the place near the source to the anode wire. The large gas amplification (typically 10{sup 4}) in the secondary ionization of proportional counter makes it possible to investigate a small change in the number of primary electrons. The electron attenuation cross-section of O{sub 2} has been evaluated by analyzing the shifts of the pulse height caused by the electron attachment to dry air and N{sub 2}.

Measurement of the magnetic interaction between two bound electrons of two separate ions.

Science.gov (United States)

Kotler, Shlomi; Akerman, Nitzan; Navon, Nir; Glickman, Yinnon; Ozeri, Roee

2014-06-19

Electrons have an intrinsic, indivisible, magnetic dipole aligned with their internal angular momentum (spin). The magnetic interaction between two electronic spins can therefore impose a change in their orientation. Similar dipolar magnetic interactions exist between other spin systems and have been studied experimentally. Examples include the interaction between an electron and its nucleus and the interaction between several multi-electron spin complexes. The challenge in observing such interactions for two electrons is twofold. First, at the atomic scale, where the coupling is relatively large, it is often dominated by the much larger Coulomb exchange counterpart. Second, on scales that are substantially larger than the atomic, the magnetic coupling is very weak and can be well below the ambient magnetic noise. Here we report the measurement of the magnetic interaction between the two ground-state spin-1/2 valence electrons of two (88)Sr(+) ions, co-trapped in an electric Paul trap. We varied the ion separation, d, between 2.18 and 2.76 micrometres and measured the electrons' weak, millihertz-scale, magnetic interaction as a function of distance, in the presence of magnetic noise that was six orders of magnitude larger than the magnetic fields the electrons apply on each other. The cooperative spin dynamics was kept coherent for 15 seconds, during which spin entanglement was generated, as verified by a negative measured value of -0.16 for the swap entanglement witness. The sensitivity necessary for this measurement was provided by restricting the spin evolution to a decoherence-free subspace that is immune to collective magnetic field noise. Our measurements show a d(-3.0(4)) distance dependence for the coupling, consistent with the inverse-cube law.

Electron temperature measurement in Z-pinch

International Nuclear Information System (INIS)

Gerusov, A.V.; Orlov, M.M.; Terent'ev, A.R.; Khrabrov, V.A.

1987-01-01

Measurement of temperature of emitting plasma sheath in noncylindrical Z-pinch in neon at the stage of convergence to the axis, based on comparing the intensity of spectral lines belonging to Ne1, Ne2, is performed. Line intensity relation dependence was determined using calculations according to emitting-collision model. Spectra were recorded by electron-optical converter and relative intensity was determined by subsequent photometry of photolayer. Cylindric symmetrical MHD-calculations during which temperature and the observed line intensity relation were determined, are conducted

Electron temperature measurements of FRX-C/LSM

International Nuclear Information System (INIS)

Rej, D.J.

1989-01-01

The electron temperature T/sub e/ has been measured with Thomson scattering field-reversed configurations (FRCs) on the Los Alamos FRX-C/LSM experiment. FRCs formed and trapped in-situ in the θ-pinch source are studied. These experiments mark the first comprehensive FRC T/sub e/ measurements in over five years with data gathered on over 400 discharges. Measurements are performed at a single point in space and time on each discharge. The Thomson scattering diagnostic consist of a Q-switched ruby laser focused from one end to a point 0.2 m from the axial midplane of the θ-pinch coil and at radius of either 0.00 or 0.10 m. Scattered light is collected, dispersed and detected with a 7-channel, triple-grating polychromator configured to detect light wavelengths between 658 and 692 nm. Photomultiplier currents are measured with gated A/D converters, with plasma background signals recorded 100-ns before and 100-ns after the laser pulse. Electron temperatures are measured at either radial position during the time interval, 10 ≤ t ≤ 70 μs, between FRC formation and the onset of the n = 2 instability which usually terminates the discharge. A variety of plasma conditions have been produced by adjusting three external parameters: the initial deuterium fill pressure p/sub O/; the reversed bias magnetic field B/sub b/; and the external magnetic field B/sub w/. The fill-pressure scan has been performed at B/sub b/ ≅ 60 mT and B/sub w/ ≅ 0.4 T with p/sub o/ set at either 2, 3, 4 or 5 mtorr. The bias-field scan, 37 ≤ B/sub b/ ≤ 95 mT, has been performed at p/sub o/ = 3 mtorr and B/sub w/ ≅ 0.4 T. 7 refs., 3 figs., 3 tabs

Simultaneous Measurements of Substorm-Related Electron Energization in the Ionosphere and the Plasma Sheet

Science.gov (United States)

Sivadas, N.; Semeter, J.; Nishimura, Y.; Kero, A.

2017-10-01

On 26 March 2008, simultaneous measurements of a large substorm were made using the Poker Flat Incoherent Scatter Radar, Time History of Events and Macroscale Interactions during Substorm (THEMIS) spacecraft, and all sky cameras. After the onset, electron precipitation reached energies ≳100 keV leading to intense D region ionization. Identifying the source of energetic precipitation has been a challenge because of lack of quantitative and magnetically conjugate measurements of loss cone electrons. In this study, we use the maximum entropy inversion technique to invert altitude profiles of ionization measured by the radar to estimate the loss cone energy spectra of primary electrons. By comparing them with magnetically conjugate measurements from THEMIS-D spacecraft in the nightside plasma sheet, we constrain the source location and acceleration mechanism of precipitating electrons of different energy ranges. Our analysis suggests that the observed electrons ≳100 keV are a result of pitch angle scattering of electrons originating from or tailward of the inner plasma sheet at 9RE, possibly through interaction with electromagnetic ion cyclotron waves. The electrons of energy 10-100 keV are produced by pitch angle scattering due to a potential drop of ≲10 kV in the auroral acceleration region (AAR) as well as wave-particle interactions in and tailward of the AAR. This work demonstrates the utility of magnetically conjugate ground- and space-based measurements in constraining the source of energetic electron precipitation. Unlike in situ spacecraft measurements, ground-based incoherent scatter radars combined with an appropriate inversion technique can be used to provide remote and continuous-time estimates of loss cone electrons in the plasma sheet.

Calorimetry for absorbed dose measurement at 1-4 MeV electron accelerators

International Nuclear Information System (INIS)

Miller, A.

2000-01-01

Calorimeters are used for dose measurement, calibration and intercomparisons at industrial electron accelerators, and their use at 10 MeV electron accelerators is well documented. The work under this research agreement concerns development of calorimeters for use at electron accelerators with energies in the range of 2-4 MeV. The dose range of the calorimeters is 3-40 kGy, and their temperature stability after irradiation was found to be sufficient for practical use in an industrial environment. Measurement uncertainties were determined to be 5% at k = 2. (author)

Electron spectroscopic evidence of electron correlation in Ni-Pt alloys: comparison with specific heat measurement

CERN Document Server

Nahm, T U; Kim, J Y; Oh, S J

2003-01-01

We have performed photoemission spectroscopy of Ni-Pt alloys to understand the origin of the discrepancy between the experimental linear coefficient of specific heat gamma and that predicted by band theory. We found that the quasiparticle density of states at the Fermi level deduced from photoemission measurement is in agreement with the experimental value of gamma, if we include the electron correlation effect. It was also found that the Ni 2p core level satellite intensity increases as Ni content is reduced, indicating a strong electron correlation effect which can enhance the quasiparticle effective mass considerably. This supports our conclusion that electron correlation is the most probable reason of disagreement of gamma between experiment and band theory.

Two old ways to measure the electron-neutrino mass

CERN Document Server

De Rújula, A

2013-01-01

Three decades ago, the measurement of the electron neutrino mass in atomic electron capture (EC) experiments was scrutinized in its two variants: single EC and neutrino-less double EC. For certain isotopes an atomic resonance enormously enhances the expected decay rates. The favoured technique, based on calorimeters as opposed to spectrometers, has the advantage of greatly simplifying the theoretical analysis of the data. After an initial surge of measurements, the EC approach did not seem to be competitive. But very recently, there has been great progress on micro-calorimeters and the measurement of atomic mass differences. Meanwhile, the beta-decay neutrino-mass limits have improved by a factor of 15, and the difficulty of the experiments by the cube of that figure. Can the "calorimetric" EC theory cope with this increased challenge? I answer this question affirmatively. In so doing I briefly review the subject and extensively address some persistent misunderstandings of the underlying quantum physics.

Electron density measurement for steady state plasmas

International Nuclear Information System (INIS)

Kawano, Yasunori; Chiba, Shinichi; Inoue, Akira

2000-01-01

Electron density of a large tokamak has been measured successfully by the tangential CO 2 laser polarimeter developed in JT-60U. The tangential Faraday rotation angles of two different wavelength of 9.27 and 10.6 μm provided the electron density independently. Two-color polarimeter concept for elimination of Faraday rotation at vacuum windows is verified for the first time. A system stability for long time operation up to ∼10 hours is confirmed. A fluctuation of a signal baseline is observed with a period of ∼3 hours and an amplitude of 0.4 - 0.7deg. In order to improve the polarimeter, an application of diamond window for reduction of the Faraday rotation at vacuum windows and another two-color polarimeter concept for elimination of mechanical rotation component are proposed. (author)

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-05-21

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

Dust-acoustic solitons in quantum plasma with kappa-distributed ions

Indian Academy of Sciences (India)

Abstract. Arbitrary amplitude dust-acoustic (DA) solitary waves in an unmagnetized and col- lisionless quantum dusty plasma comprising cold dust particles, kappa (κ)-distributed ions and degenerate electrons are investigated. The influence of suprathermality and quantum effects on the linear dispersion relation of DA ...

Why and How to Measure the Use of Electronic Resources

Directory of Open Access Journals (Sweden)

Jean Bernon

2008-11-01

Full Text Available A complete overview of library activity implies a complete and reliable measurement of the use of both electronic resources and printed materials. This measurement is based on three sets of definitions: document types, use types and user types. There is a common model of definitions for printed materials, but a lot of questions and technical issues remain for electronic resources. In 2006 a French national working group studied these questions. It relied on the COUNTER standard, but found it insufficient and pointed out the need for local tools such as web markers and deep analysis of proxy logs. Within the French national consortium COUPERIN, a new working group is testing ERMS, SUSHI standards, Shibboleth authentication, along with COUNTER standards, to improve the counting of the electronic resources use. At this stage this counting is insufficient and its improvement will be a European challenge for the future.

Electron beam water calorimetry measurements to obtain beam quality conversion factors.

Science.gov (United States)

Muir, Bryan R; Cojocaru, Claudiu D; McEwen, Malcolm R; Ross, Carl K

2017-10-01

To provide results of water calorimetry and ion chamber measurements in high-energy electron beams carried out at the National Research Council Canada (NRC). There are three main aspects to this work: (a) investigation of the behavior of ionization chambers in electron beams of different energies with focus on long-term stability, (b) water calorimetry measurements to determine absorbed dose to water in high-energy beams for direct calibration of ion chambers, and (c) using measurements of chamber response relative to reference ion chambers, determination of beam quality conversion factors, k Q , for several ion chamber types. Measurements are made in electron beams with energies between 8 MeV and 22 MeV from the NRC Elekta Precise clinical linear accelerator. Ion chamber measurements are made as a function of depth for cylindrical and plane-parallel ion chambers over a period of five years to investigate the stability of ion chamber response and for indirect calibration. Water calorimetry measurements are made in 18 MeV and 22 MeV beams. An insulated enclosure with fine temperature control is used to maintain a constant temperature (drifts less than 0.1 mK/min) of the calorimeter phantom at 4°C to minimize effects from convection. Two vessels of different designs are used with calibrated thermistor probes to measure radiation induced temperature rise. The vessels are filled with high-purity water and saturated with H 2 or N 2 gas to minimize the effect of radiochemical reactions on the measured temperature rise. A set of secondary standard ion chambers are calibrated directly against the calorimeter. Finally, several other ion chambers are calibrated in the NRC 60 Co reference field and then cross-calibrated against the secondary standard chambers in electron beams to realize k Q factors. The long-term stability of the cylindrical ion chambers in electron beams is better (always <0.15%) than plane-parallel chambers (0.2% to 0.4%). Calorimetry measurements

Positron lifetime measurements on electron irradiated amorphous alloys

International Nuclear Information System (INIS)

Moser, P.; Hautojaervi, P.; Chamberod, A.; Yli-Kauppila, J.; Van Zurk, R.

1981-08-01

Great advance in understanding the nature of point defects in crystalline metals has been achieved by employing positron annihilation technique. Positrons detect vacancy-type defects and the lifetime value of trapped positrons gives information on the size of submicroscopic vacancy aglomerates and microvoids. In this paper it is shown that low-temperature electron irradiations can result in a considerable increase in the positron lifetimes in various amorphous alloys because of the formation of vacancy-like defects which, in addition of the pre-existing holes, are able to trap positrons. Studied amorphous alloys were Fe 80 B 20 , Pd 80 Si 20 , Cu 50 Ti 50 , and Fe 40 Ni 40 P 14 B 6 . Electron irradiations were performed with 3 MeV electrons at 20 K to doses around 10 19 e - /cm 2 . After annealing positron lifetime spectra were measured at 77 K

Experimental measurement of electron heat diffusivity in a tokamak

International Nuclear Information System (INIS)

Callen, J.D.; Jahns, G.L.

1976-06-01

The electron temperature perturbation produced by internal disruptions in the center of the Oak Ridge Tokamak (ORMAK) is followed with a multi-chord soft x-ray detector array. The space-time evolution is found to be diffusive in character, with a conduction coefficient larger by a factor of 2.5 - 15 than that implied by the energy containment time, apparently because it is a measurement for the small group of electrons whose energies exceed the cut-off energy of the detectors

Cherenkov-type diamond detectors for measurements of fast electrons in the TORE-SUPRA tokamak

International Nuclear Information System (INIS)

Jakubowski, L.; Sadowski, M. J.; Zebrowski, J.; Rabinski, M.; Malinowski, K.; Mirowski, R.; Lotte, Ph.; Gunn, J.; Pascal, J-Y.; Colledani, G.; Basiuk, V.; Goniche, M.; Lipa, M.

2010-01-01

The paper presents a schematic design and tests of a system applicable for measurements of fast electron pulses emitted from high-temperature plasma generated inside magnetic confinement fusion machines, and particularly in the TORE-SUPRA facility. The diagnostic system based on the registration of the Cherenkov radiation induced by fast electrons within selected solid radiators is considered, and electron low-energy thresholds for different radiators are given. There are some estimates of high thermal loads, which might be deposited by intense electron beams upon parts of the diagnostic equipment within the TORE-SUPRA device. There are some proposed measures to overcome this difficulty by the selection of appropriate absorption filters and Cherenkov radiators, and particularly by the application of a fast-moving reciprocating probe. The paper describes the measuring system, its tests, as well as some results of the preliminary measurements of fast electrons within TORE-SUPRA facility.

Measurement of high-energy electrons by means of a Cherenkov detector in ISTTOK tokamak

Energy Technology Data Exchange (ETDEWEB)

Jakubowski, L., E-mail: lech.Jjakubowski@ipj.gov.p [Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk (Poland); Zebrowski, J. [Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk (Poland); Plyusnin, V.V. [Association Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Av. Rovisco Pais, 1049 - 001 Lisboa (Portugal); Malinowski, K.; Sadowski, M.J.; Rabinski, M. [Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk (Poland); Fernandes, H.; Silva, C.; Duarte, P. [Association Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Av. Rovisco Pais, 1049 - 001 Lisboa (Portugal)

2010-10-15

The paper concerns detectors of the Cherenkov radiation which can be used to measure high-energy electrons escaping from short-living plasma. Such detectors have high temporal (about 1 ns) and spatial (about 1 mm) resolution. The paper describes a Cherenkov-type detector which was designed, manufactured and installed in the ISTTOK tokamak in order to measure fast runaway electrons. The radiator of that detector was made of an aluminium nitride (AlN) tablet with a light-tight filter on its front surface. Cherenkov signals from the radiator were transmitted through an optical cable to a fast photomultiplier. It made possible to perform direct measurements of the runaway electrons of energy above 80 keV. The measured energy values and spatial characteristics of the recorded electrons appeared to be consistent with results of numerical modelling of the runaway electron generation process in the ISTTOK tokamak.

Cherenkov-type diamond detectors for measurements of fast electrons in the TORE-SUPRA tokamak

Energy Technology Data Exchange (ETDEWEB)

Jakubowski, L.; Sadowski, M. J.; Zebrowski, J.; Rabinski, M.; Malinowski, K.; Mirowski, R. [Andrzej Soltan Institute for Nuclear Studies (IPJ), Otwock-Swierk 05-400 (Poland); Lotte, Ph.; Gunn, J.; Pascal, J-Y.; Colledani, G.; Basiuk, V.; Goniche, M.; Lipa, M. [CEA, IRFM, St Paul-lez-Durance F-13108 (France)

2010-01-15

The paper presents a schematic design and tests of a system applicable for measurements of fast electron pulses emitted from high-temperature plasma generated inside magnetic confinement fusion machines, and particularly in the TORE-SUPRA facility. The diagnostic system based on the registration of the Cherenkov radiation induced by fast electrons within selected solid radiators is considered, and electron low-energy thresholds for different radiators are given. There are some estimates of high thermal loads, which might be deposited by intense electron beams upon parts of the diagnostic equipment within the TORE-SUPRA device. There are some proposed measures to overcome this difficulty by the selection of appropriate absorption filters and Cherenkov radiators, and particularly by the application of a fast-moving reciprocating probe. The paper describes the measuring system, its tests, as well as some results of the preliminary measurements of fast electrons within TORE-SUPRA facility.

Measurements of the electron and muon inclusive cross-sections

Indian Academy of Sciences (India)

We present the measurements of the differential cross-sections for inclusive electron and muon production in proton–proton collisions at a centre-of-mass energy of s = 7 TeV, using ∼ 1.4 pb-1 of data collected by the ATLAS detector at the Large Hadron Collider. The muon cross-section is measured as a function of muon ...

Imaging and Measuring Electron Beam Dose Distributions Using Holographic Interferometry

DEFF Research Database (Denmark)

Miller, Arne; McLaughlin, W. L.

1975-01-01

Holographic interferometry was used to image and measure ionizing radiation depth-dose and isodose distributions in transparent liquids. Both broad and narrowly collimated electron beams from accelerators (2–10 MeV) provided short irradiation times of 30 ns to 0.6 s. Holographic images...... and measurements of absorbed dose distributions were achieved in liquids of various densities and thermal properties and in water layers thinner than the electron range and with backings of materials of various densities and atomic numbers. The lowest detectable dose in some liquids was of the order of a few k......Rad. The precision limits of the measurement of dose were found to be ±4%. The procedure was simple and the holographic equipment stable and compact, thus allowing experimentation under routine laboratory conditions and limited space....

Electron bunchlength measurement from analysis of fluctuations in spontaneous emission

International Nuclear Information System (INIS)

Catravas, P.; Leemans, W.P.; Wurtele, J.S.; Zolotorev, M.S.; Babzien, M.; Ben-Zvi, I.; Segalov, Z.; Wang, X.; Yakimenko, V.

1999-01-01

A statistical analysis of fluctuations in the spontaneous emission of a single bunch of electrons is shown to provide a new bunchlength diagnostic. This concept, originally proposed by Zolotorev and Stupakov [1], is based on the fact that shot noise from a finite bunch has a correlation length defined by the bunchlength, and therefore has a spiky spectrum. Single shot spectra of wiggler spontaneous emission have been measured at 632 nm from 44 MeV single electron bunches of 1 - 5 ps. The scaling of the spectral fluctuations with frequency resolution and the scaling of the spectral intensity distribution with bunchlength are studied. Bunchlength was extracted in a single shot measurement. Agreement was obtained between the experiment and a theoretical model, and with independent time integrated measurements. copyright 1999 American Institute of Physics

Demonstration of relatively new electron dosimetry measurement techniques on the Mevatron 80

International Nuclear Information System (INIS)

Meyer, J.A.; Palta, J.R.; Hogstrom, K.R.

1984-01-01

A comprehensive set of electron dosimetry measurements at 7, 10, 12, 15, and 18 MeV was made on a Mevatron 80. Dosimetry measurements presented include percentage depth dose, dose in the buildup region, field size dependence of output, output at extended distances, lead transmission measurements, and isodose curves. These beam measurements are presented to document the electron beam characteristics of this linear accelerator. Three relatively new dosimetry techniques, which have not been standardly used in the past, are illustrated. One technique determines the depth dose of fields too small to measure. A second technique accurately converts depth dose measured in polystyrene to depth dose in water. A third technique calculates the output at extended distances

Real-Time, Single-Shot Temporal Measurements of Short Electron Bunches, Terahertz CSR and FEL Radiation

CERN Document Server

Berden, G; Van der Meer, A F G

2005-01-01

Electro-optic detection of the Coulomb field of electron bunches is a promising technique for single-shot measurements of the bunch length and shape in the sub-picosecond time domain. This technique has been applied to the measurement of 50 MeV electron bunches in the FELIX free electron laser, showing the longitudinal profile of single bunches of around 650 fs FWHM [Phys. Rev. Lett. 93, 114802 (2004)]. The method is non-destructive and real-time, and therefore ideal for online monitoring of the longitudinal shape of single electron bunches. At FELIX we have used it for real-time optimization of sub-picosecond electron bunches. Electro-optic detection has also been used to measure the electric field profiles of far-infrared (or terahertz) optical pulses generated by the relativistic electrons. We have characterised the far-infrared output of the free electron laser, and more recently, we have measured the temporal profile of terahertz optical pulses generated at one of the bending magnets.

Rocket potential measurements during electron beam injection into the ionosphere

International Nuclear Information System (INIS)

Gringauz, K.I.; Shutte, N.M.

1981-01-01

Electron flux measurements were made during pulsed injection of electron beams at a current of about 0.5 A and energy of 15 or 27 keV, using a retarding potential analyzer which was mounted on the lateral surface of the Eridan rocket during the ARAKS experiment of January 26, 1975. The general character of the retardation curves was found to be the same regardless of the electron injection energy, and regardless of the fact whether the plasma generator, injecting quasineutral cesium plasma with an ion current of about 10 A, was switched on. A sharp current increase in the interval between 10 to the -7th and 10 to the -6th A was observed with a decrease of the retarding potential. The rocket potential did not exceed approximately 150 V at about 130 to 190 km, and decreased to 20 V near 100 km. This was explained by the formation of a highly conducting region near the rocket, which was formed via intense plasma waves generated by the beam. Measurements of electron fluxes with energies of 1 to 3 keV agree well with estimates based on the beam plasma discharge theory

Front-end electronics for accurate energy measurement of double beta decays

International Nuclear Information System (INIS)

Gil, A.; Díaz, J.; Gómez-Cadenas, J.J.; Herrero, V.; Rodriguez, J.; Serra, L.; Toledo, J.; Esteve, R.; Monzó, J.M.; Monrabal, F.; Yahlali, N.

2012-01-01

NEXT, a double beta decay experiment that will operate in Canfranc Underground Laboratory (Spain), aims at measuring the neutrinoless double-β decay of the 136Xe isotope using a TPC filled with enriched Xenon gas at high pressure operated in electroluminescence mode. One technological challenge of the experiment is to achieve resolution better than 1% in the energy measurement using a plane of UV sensitive photomultipliers readout with appropriate custom-made front-end electronics. The front-end is designed to be sensitive to the single photo-electron to detect the weak primary scintillation light produced in the chamber, and also to be able to cope with the electroluminescence signal (several hundred times higher and with a duration of microseconds). For efficient primary scintillation detection and precise energy measurement of the electroluminescent signals the front-end electronics features low noise and adequate amplification. The signal shaping provided allows the digitization of the signals at a frequency as low as 40 MHz.

Exciton diffusion coefficient measurement in ZnO nanowires under electron beam irradiation

Science.gov (United States)

Donatini, Fabrice; Pernot, Julien

2018-03-01

In semiconductor nanowires (NWs) the exciton diffusion coefficient can be determined using a scanning electron microscope fitted with a cathodoluminescence system. High spatial and temporal resolution cathodoluminescence experiments are needed to measure independently the exciton diffusion length and lifetime in single NWs. However, both diffusion length and lifetime can be affected by the electron beam bombardment during observation and measurement. Thus, in this work the exciton lifetime in a ZnO NW is measured versus the electron beam dose (EBD) via a time-resolved cathodoluminescence experiment with a temporal resolution of 50 ps. The behavior of the measured exciton lifetime is consistent with our recent work on the EBD dependence of the exciton diffusion length in similar NWs investigated under comparable SEM conditions. Combining the two results, the exciton diffusion coefficient in ZnO is determined at room temperature and is found constant over the full span of EBD.

In situ measurements and transmission electron microscopy of carbon nanotube field-effect transistors

International Nuclear Information System (INIS)

Kim, Taekyung; Kim, Seongwon; Olson, Eric; Zuo Jianmin

2008-01-01

We present the design and operation of a transmission electron microscopy (TEM)-compatible carbon nanotube (CNT) field-effect transistor (FET). The device is configured with microfabricated slits, which allows direct observation of CNTs in a FET using TEM and measurement of electrical transport while inside the TEM. As demonstrations of the device architecture, two examples are presented. The first example is an in situ electrical transport measurement of a bundle of carbon nanotubes. The second example is a study of electron beam radiation effect on CNT bundles using a 200 keV electron beam. In situ electrical transport measurement during the beam irradiation shows a signature of wall- or tube-breakdown. Stepwise current drops were observed when a high intensity electron beam was used to cut individual CNT bundles in a device with multiple bundles

Dosimetry measurements during the commissioning of the GJ-2 electron accelerator

DEFF Research Database (Denmark)

Chosdu, R.; Hilmy, N.; Tobing, R.

1995-01-01

The GJ-2 electron accelerator (made in China, Sanghai) was put into operation at the Centre for Application of Isotopes and Radiation in Jakarta, Indonesia. In the course of the commissioning of the machine its main technical parameters were measured under different operating conditions. The elec......The GJ-2 electron accelerator (made in China, Sanghai) was put into operation at the Centre for Application of Isotopes and Radiation in Jakarta, Indonesia. In the course of the commissioning of the machine its main technical parameters were measured under different operating conditions......, ethanol-chlorobenzene dosimeter solution and FWT-60 film dosimeters. The applicability of polystyrene calorimeters designed for low electron energies at Ris phi National Laboratory was also tested for nominal dose determination....

A method for the direct measurement of electronic site populations in a molecular aggregate using two-dimensional electronic-vibrational spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Lewis, Nicholas H. C.; Dong, Hui; Oliver, Thomas A. A.; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720 (United States)

2015-09-28

Two dimensional electronic spectroscopy has proved to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale.

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

Ion Flux Measurements in Electron Beam Produced Plasmas in Atomic and Molecular Gases

Science.gov (United States)

Walton, S. G.; Leonhardt, D.; Blackwell, D. D.; Murphy, D. P.; Fernsler, R. F.; Meger, R. A.

2001-10-01

In this presentation, mass- and time-resolved measurements of ion fluxes sampled from pulsed, electron beam-generated plasmas will be discussed. Previous works have shown that energetic electron beams are efficient at producing high-density plasmas (10^10-10^12 cm-3) with low electron temperatures (Te < 1.0 eV) over the volume of the beam. Outside the beam, the plasma density and electron temperature vary due, in part, to ion-neutral and electron-ion interactions. In molecular gases, electron-ion recombination plays a significant role while in atomic gases, ion-neutral interactions are important. These interactions also determine the temporal variations in the electron temperature and plasma density when the electron beam is pulsed. Temporally resolved ion flux and energy distributions at a grounded electrode surface located adjacent to pulsed plasmas in pure Ar, N_2, O_2, and their mixtures are discussed. Measurements are presented as a function of operating pressure, mixture ratio, and electron beam-electrode separation. The differences in the results for atomic and molecular gases will also be discussed and related to their respective gas-phase kinetics.

CO2 laser interferometer for temporally and spatially resolved electron density measurements

Science.gov (United States)

Brannon, P. J.; Gerber, R. A.; Gerardo, J. B.

1982-09-01

A 10.6-μm Mach-Zehnder interferometer has been constructed to make temporally and spatially resolved measurements of electron densities in plasmas. The device uses a pyroelectric vidicon camera and video memory to record and display the two-dimensional fringe pattern and a Pockels cell to limit the pulse width of the 10.6-μm radiation. A temporal resolution of 14 ns has been demonstrated. The relative sensitivity of the device for electron density measurements is 2×1015 cm-2 (the line integral of the line-of-sight length and electron density), which corresponds to 0.1 fringe shift.

CO2 laser interferometer for temporally and spatially resolved electron density measurements

International Nuclear Information System (INIS)

Brannon, P.J.; Gerber, R.A.; Gerardo, J.B.

1982-01-01

A 10.6-μm Mach--Zehnder interferometer has been constructed to make temporally and spatially resolved measurements of electron densities in plasmas. The device uses a pyroelectric vidicon camera and video memory to record and display the two-dimensional fringe pattern and a Pockels cell to limit the pulse width of the 10.6-μm radiation. A temporal resolution of 14 ns has been demonstrated. The relative sensitivity of the device for electron density measurements is 2 x 10 15 cm -2 (the line integral of the line-of-sight length and electron density), which corresponds to 0.1 fringe shift

Rocket measurements of X-rays and energetic electrons through an auroral arc

International Nuclear Information System (INIS)

Aarsnes, K.; Stadsnes, J.; Soeraas, F.

1976-01-01

Preliminary results from rocket measurements on auroral electron precipitation are discussed as far as the spatial structure and time and space variations in the primary electron fluxes are concerned. The analysis demonstrates that there was a good overall correspondence between the X-ray and electron data. By using a well collimated X-ray detector on a spinning rocket, it was possible to get additional information on the overall electron precipitation pattern

Waves and Instabilities in Collisionless Shocks

Science.gov (United States)

1984-04-01

occur in the electron foreshock and are driven by suprathermal electrons escaping into the region upstream of the shock. Both the ion-acoustic and...ULF waves occur in the ion foreshock and are associated with ions streaming into the region upstream of 11 the shock. The region downstream of the...the discussion of these waves it is useful to distinguish two regions, called the electron foreshock and the ion foreshock . Because the particles

Calibration of a two-color soft x-ray diagnostic for electron temperature measurement

Energy Technology Data Exchange (ETDEWEB)

Reusch, L. M., E-mail: lmmcguire@wisc.edu; Den Hartog, D. J.; Goetz, J.; McGarry, M. B. [University of Wisconsin - Madison, Madison, Wisconsin 53703 (United States); Franz, P. [Consorzio RFX, Padova (Italy); Stephens, H. D. [University of Wisconsin - Madison, Madison, Wisconsin 53703 (United States); Pierce College Fort Steilacoom, Lakewood, Washington 98498 (United States)

2016-11-15

The two-color soft x-ray (SXR) tomography diagnostic on the Madison Symmetric Torus is capable of making electron temperature measurements via the double-filter technique; however, there has been a 15% systematic discrepancy between the SXR double-filter (SXR{sub DF}) temperature and Thomson scattering (TS) temperature. Here we discuss calibration of the Be filters used in the SXR{sub DF} measurement using empirical measurements of the transmission function versus energy at the BESSY II electron storage ring, electron microprobe analysis of filter contaminants, and measurement of the effective density. The calibration does not account for the TS and SXR{sub DF} discrepancy, and evidence from experiments indicates that this discrepancy is due to physics missing from the SXR{sub DF} analysis rather than instrumentation effects.

Measurements of picosecond pulses of a high-current electron accelerator

International Nuclear Information System (INIS)

Zheltov, K.A.; Petrenko, A.N.; Turundaevskaya, I.G.; Shalimanov, V.F.

1997-01-01

The duration of a picosecond high-current accelerator electron beam pulse duration is measured and its shape is determined using a measuring line, comprising a Faraday cup, a radiofrequency cable of minor length and a wide-band SRG-7 oscillograph. The procedure of data reconstruction according to regularization method is applied to determine the actual shape of the pulse measured

Detecting Electron Transport of Amino Acids by Using Conductance Measurement

Directory of Open Access Journals (Sweden)

Wei-Qiong Li

2017-04-01

Full Text Available The single molecular conductance of amino acids was measured by a scanning tunneling microscope (STM break junction. Conductance measurement of alanine gives out two conductance values at 10−1.85 G0 (1095 nS and 10−3.7 G0 (15.5 nS, while similar conductance values are also observed for aspartic acid and glutamic acid, which have one more carboxylic acid group compared with alanine. This may show that the backbone of NH2–C–COOH is the primary means of electron transport in the molecular junction of aspartic acid and glutamic acid. However, NH2–C–COOH is not the primary means of electron transport in the methionine junction, which may be caused by the strong interaction of the Au–SMe (methyl sulfide bond for the methionine junction. The current work reveals the important role of the anchoring group in the electron transport in different amino acids junctions.

Measurement of the band gap by reflection electron energy loss spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Vos, Maarten, E-mail: maarten.vos@anu.edu.au [Electronic Materials Engineering Department, Research School of Physics and Engineering, The Australian National University, Canberra 0200 (Australia); King, Sean W. [Logic Technology Development, Intel Corporation, Hillsboro, OR 97124 (United States); French, Benjamin L. [Ocotillo Materials Laboratory, Intel Corporation, Chandler, AZ 85248 (United States)

2016-10-15

Highlights: • Semiconductors are measured (without surface preparation) using REELS. • At low beam energies it is difficult to measure band gap due to surface impurities. • At very high energies it is difficult to measure band gap due to recoil effect. • At intermediate energies (around 5 keV) one obtains a good estimate of the band gap. - Abstract: We investigate the possibilities of measuring the band gap of a variety of semiconductors and insulators by reflection electron energy loss spectroscopy without additional surface preparation. The band gap is a bulk property, whereas reflection energy loss spectroscopy is generally considered a surface sensitive technique. By changing the energy of the incoming electrons, the degree of surface sensitivity can be varied. Here, we present case studies to determine the optimum condition for the determination of the band gap. At very large incoming electron energies recoil effects interfere with the band gap determination, whereas at very low energies surface effects are obscuring the band gap without surface preparation. Using an incoming energy of 5 keV a reasonable estimate of the band gap is obtained in most cases.

Measurement of the band gap by reflection electron energy loss spectroscopy

International Nuclear Information System (INIS)

Vos, Maarten; King, Sean W.; French, Benjamin L.

2016-01-01

Highlights: • Semiconductors are measured (without surface preparation) using REELS. • At low beam energies it is difficult to measure band gap due to surface impurities. • At very high energies it is difficult to measure band gap due to recoil effect. • At intermediate energies (around 5 keV) one obtains a good estimate of the band gap. - Abstract: We investigate the possibilities of measuring the band gap of a variety of semiconductors and insulators by reflection electron energy loss spectroscopy without additional surface preparation. The band gap is a bulk property, whereas reflection energy loss spectroscopy is generally considered a surface sensitive technique. By changing the energy of the incoming electrons, the degree of surface sensitivity can be varied. Here, we present case studies to determine the optimum condition for the determination of the band gap. At very large incoming electron energies recoil effects interfere with the band gap determination, whereas at very low energies surface effects are obscuring the band gap without surface preparation. Using an incoming energy of 5 keV a reasonable estimate of the band gap is obtained in most cases.

Electron cloud density measurements in accelerator beam-pipe using resonant microwave excitation

Energy Technology Data Exchange (ETDEWEB)

Sikora, John P., E-mail: jps13@cornell.edu [CLASSE, Cornell University, Ithaca, NY 14853 (United States); Carlson, Benjamin T. [Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Duggins, Danielle O. [Gordon College, Wenham, MA 01984 (United States); Hammond, Kenneth C. [Columbia University, New York, NY 10027 (United States); De Santis, Stefano [LBNL, Berkeley, CA 94720 (United States); Tencate, Alister J. [Idaho State University, Pocatello, ID 83209 (United States)

2014-08-01

An accelerator beam can generate low energy electrons in the beam-pipe, generally called electron cloud, that can produce instabilities in a positively charged beam. One method of measuring the electron cloud density is by coupling microwaves into and out of the beam-pipe and observing the response of the microwaves to the presence of the electron cloud. In the original technique, microwaves are transmitted through a section of beam-pipe and a change in EC density produces a change in the phase of the transmitted signal. This paper describes a variation on this technique in which the beam-pipe is resonantly excited with microwaves and the electron cloud density calculated from the change that it produces in the resonant frequency of the beam-pipe. The resonant technique has the advantage that measurements can be localized to sections of beam-pipe that are a meter or less in length with a greatly improved signal to noise ratio.

An optimized Faraday cage design for electron beam current measurements

International Nuclear Information System (INIS)

Turner, J.N.; Hausner, G.G.; Parsons, D.F.

1975-01-01

A Faraday cage detector is described for measuring electron beam intensity for use with energies up to 1.2 Mev, with the present data taken at 100 keV. The design features a readily changeable limiting aperture and detector cup geometry, and a secondary electron suppression grid. The detection efficiency of the cage is shown to be limited only by primary backscatter through the detector solid angle of escape, which is optimized with respect to primary backscattered electrons and secondary electron escape. The geometry and stopping material of the detection cup are varied, and the results show that for maximum detection efficiency with carbon as the stopping mateiral, the solid angle of escape must be equal to or less than 0.05πsr. The experimental results are consistent within the +-2% accuracy of the detection electronics, and are not limited by the Faraday cage detection efficiency. (author)

Control of the current density profile with lower hybrid current drive on PBX-M

International Nuclear Information System (INIS)

Bell, R.E.; Bernabei, S.; Chu, T.K.; Gettelfinger, G.; Greenough, N.; Hatcher, R.; Ignat, D.; Jardin, S.; Kaita, R.; Kaye, S.; Kozub, T.; Kugel, H.; LeBlanc, B.; Okabayashi, M.; Paul, S.; Sauthoff, N.; Sesnic, S.; Sun, Y.; Takahashi, H.; Tighe, W.; Valeo, E.; von Goeler, S.; Jones, S.; Kesner, J.; Luckhardt, S.; Paoletti, F.; Levinton, F.; Timini, F.

1993-07-01

Lower hybrid current drive (LHCD) is being explored as a means to control the current density profile on PBX-M with the goal of raising the central safety factor q(O) to values of 1.5-2 to facilitate access to a full-volume second stable regime. Initial experiments have been conducted with up to 400 kW of 4.6 GHz LH power in circular and indented plasmas with modest parameters. A tangential-viewing two-dimensional hard x-ray imaging diagnostic has been used to observe the bremsstrahlung emission from the suprathermal electrons generated during LHCD. Hollow hard x-ray images have indicated off-axis localization of the driven current. A serious obstacle to the control of the current density profile with LHCD is the concomitant generation of MHD activity, which can seriously degrade the confinement of suprathermal electrons. By combining neutral beam injection with LHCD, an MHD-free condition has been obtained where q(O) is raised above 1

Capacitive divider for output voltage measurement of intense electron beam accelerator

International Nuclear Information System (INIS)

Ding Desheng; Yi Lingzhi; Yu Binxiong; Hong Zhiqiang; Liu Jinliang

2012-01-01

A kind of simple-mechanism, easy-disassembly self-integrating capacitive divider used for measuring diode output voltage of intense electron beam accelerator (IEBA) is developed. The structure of the capacitive divider is described, and the capacitance value of the capacitive divider is calculated by theoretical analysis and electromagnetic simulation. The dependence of measurement voltage on electrical parameters such as stray capacitance, earth capacitance of front resistance is obtained by PSpice simulation. Measured waveforms appear overshoot phenomenon when stray capacitance of front resistance is larger, and the wavefront will be affected when earth capacitance of front resistance is larger. The diode output voltage waveforms of intense electron beam accelerator, are measured by capacitive divider and calibrated by water resistance divider, which is accordance with that measured by a resistive divider, the division ratio is about 563007. The designed capacitive divider can be used to measure high-voltage pulse with 100 ns full width at half maximum. (authors)

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

Lifetime measurements using the Jefferson Lad Load-Lock Electron Gun

International Nuclear Information System (INIS)

J. Grames; P. Adderley; M. Baylac; J. Brittian; D. Charles; J. Clark; J. Hansknecht; M. Poelker; M. Stutzman; K. Surles-Law

2000-01-01

Lifetime measurements of bulk GaAs using a 100 kV load-lock electron gun and beam line were made. Initial tests used anodized samples to study lifetime under various conditions (gun vacuum, laser spot location, activated area). Subsequent tests used a mechanical mask to limit the active area and included improved monitoring of the gun chamber and beam line vacuum pressure. Results of these measurements support claims made at past workshops, namely photocathode lifetime improves when gun vacuum is enhanced and when electron emission from the edge of the photocathode is eliminated. The dependence upon laser spot location is less certain. Tests studying lifetime at higher beam intensity (I ∼ 8 mA) have begun

Simulations of the electron cloud buildup and its influence on the microwave transmission measurement

Energy Technology Data Exchange (ETDEWEB)

Haas, Oliver Sebastian, E-mail: o.haas@gsi.de [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt (Germany); Boine-Frankenheim, Oliver [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt (Germany); Technische Universität Darmstadt, Institut für Theorie Elektromagnetischer Felder, Schlossgartenstraße 8, 64289 Darmstadt (Germany); Petrov, Fedor [Technische Universität Darmstadt, Institut für Theorie Elektromagnetischer Felder, Schlossgartenstraße 8, 64289 Darmstadt (Germany)

2013-11-21

An electron cloud density in an accelerator can be measured using the Microwave Transmission (MWT) method. The aim of our study is to evaluate the influence of a realistic, nonuniform electron cloud on the MWT. We conduct electron cloud buildup simulations for beam pipe geometries and bunch parameters resembling roughly the conditions in the CERN SPS. For different microwave waveguide modes the phase shift induced by a known electron cloud density is obtained from three different approaches: 3D Particle-In-Cell (PIC) simulation of the electron response, a 2D eigenvalue solver for waveguide modes assuming a dielectric response function for cold electrons, a perturbative method assuming a sufficiently smooth density profile. While several electron cloud parameters, such as temperature, result in minor errors in the determined density, the transversely inhomogeneous density can introduce a large error in the measured electron density. We show that the perturbative approach is sufficient to describe the phase shift under realistic electron cloud conditions. Depending on the geometry of the beam pipe, the external magnetic field configuration and the used waveguide mode, the electron cloud density can be concentrated at the beam pipe or near the beam pipe center, leading to a severe over- or underestimation of the electron density. -- Author-Highlights: •Electron cloud distributions are very inhomogeneous, especially in dipoles. •These inhomogeneities affect the microwave transmission measurement results. •Electron density might be over- or underestimated, depending on setup. •This can be quantified with several models, e.g. a perturbative approach.

Measuring the electron bunch timing with femtosecond resolution at FLASH

International Nuclear Information System (INIS)

Bock, Marie Kristin

2013-03-01

Bunch arrival time monitors (BAMs) are an integral part of the laser-based synchronisation system which is being developed at the Free Electron Laser in Hamburg (FLASH).The operation principle comprises the measurement of the electron bunch arrival time relative to the optical timing reference, which is provided by actively length-stabilised fibre-links of the synchronisation system. The monitors are foreseen to be used as a standard diagnostic tool, not only for FLASH but also for the future European X-Ray Free-Electron Laser (European XFEL). The present bunch arrival time monitors have evolved from proof-of-principle experiments to beneficial diagnostic devices, which are almost permanently available during standard machine operation. This achievement has been a major objective of this thesis. The developments went in parallel to improvements in the reliable and low-maintenance operation of the optical synchronisation system. The key topics of this thesis comprised the characterisation and optimisation of the opto-mechanical front-ends of both, the fibre-links and the BAMs. The extent of applications involving the bunch arrival time information has been enlarged, providing automated measurements for properties of the RF acceleration modules, for instance, the RF on-crest phase determination and the measurement of energy fluctuations. Furthermore, two of the currently installed BAMs are implemented in an active phase and gradient stabilisation of specific modules in order to minimise the arrival time jitter of the electron bunches at the location of the FEL undulators, which is crucial for a high timing resolution of pump-probe experiments.

Measuring the electron bunch timing with femtosecond resolution at FLASH

Energy Technology Data Exchange (ETDEWEB)

Bock, Marie Kristin

2013-03-15

Bunch arrival time monitors (BAMs) are an integral part of the laser-based synchronisation system which is being developed at the Free Electron Laser in Hamburg (FLASH).The operation principle comprises the measurement of the electron bunch arrival time relative to the optical timing reference, which is provided by actively length-stabilised fibre-links of the synchronisation system. The monitors are foreseen to be used as a standard diagnostic tool, not only for FLASH but also for the future European X-Ray Free-Electron Laser (European XFEL). The present bunch arrival time monitors have evolved from proof-of-principle experiments to beneficial diagnostic devices, which are almost permanently available during standard machine operation. This achievement has been a major objective of this thesis. The developments went in parallel to improvements in the reliable and low-maintenance operation of the optical synchronisation system. The key topics of this thesis comprised the characterisation and optimisation of the opto-mechanical front-ends of both, the fibre-links and the BAMs. The extent of applications involving the bunch arrival time information has been enlarged, providing automated measurements for properties of the RF acceleration modules, for instance, the RF on-crest phase determination and the measurement of energy fluctuations. Furthermore, two of the currently installed BAMs are implemented in an active phase and gradient stabilisation of specific modules in order to minimise the arrival time jitter of the electron bunches at the location of the FEL undulators, which is crucial for a high timing resolution of pump-probe experiments.

Effects of peripheral physical phenomena on ECE spectra

International Nuclear Information System (INIS)

Airoldi, A.; Ramponi, G.

1993-01-01

In large fusion Tokamaks the measurement of the Electron Cyclotron Emission (ECE) from the low field side, perpendicularly viewing chord, is by now a standard way of obtaining the radial electron temperature profile. In high temperature plasmas the condition of large optical thickness for the second harmonic X-mode may be easily satisfied even for frequencies corresponding to the edge plasma region, allowing the temperature profile to be inferred. Recent experimental observations of enhanced emission at frequencies associated with the extreme edge of the profile in H-mode JET plasmas have been interpreted as the effect of a small fraction of suprathermal electrons. It is well known that the ECE spectra are very sensitive to the presence of non-thermal electron components, thus it is important to interpret the ECE signals as an indication of the possible deviation of the electron distribution function from a 'pure' Maxwellian and to discern under which conditions they are a good measure of the plasma thermal energy. (author) 3 refs., 6 figs

Light Quality Affects Chloroplast Electron Transport Rates Estimated from Chl Fluorescence Measurements.

Science.gov (United States)

Evans, John R; Morgan, Patrick B; von Caemmerer, Susanne

2017-10-01

Chl fluorescence has been used widely to calculate photosynthetic electron transport rates. Portable photosynthesis instruments allow for combined measurements of gas exchange and Chl fluorescence. We analyzed the influence of spectral quality of actinic light on Chl fluorescence and the calculated electron transport rate, and compared this with photosynthetic rates measured by gas exchange in the absence of photorespiration. In blue actinic light, the electron transport rate calculated from Chl fluorescence overestimated the true rate by nearly a factor of two, whereas there was closer agreement under red light. This was consistent with the prediction made with a multilayer leaf model using profiles of light absorption and photosynthetic capacity. Caution is needed when interpreting combined measurements of Chl fluorescence and gas exchange, such as the calculation of CO2 partial pressure in leaf chloroplasts. © Crown copyright 2017.

Synchrotron-based measurements of the electronic structure of the organic semiconductor copper phthalocyanine

International Nuclear Information System (INIS)

Downes, J.E.

2004-01-01

Full text: Copper phthalocyanine (CuPc) is a prototypical molecular organic semiconductor that is currently used in the construction of many organic electronic devices such as organic light emitting diodes (OLEDs). Although the material is currently being used, and despite many experimental and theoretical studies, it's detailed electronic structure is still not completely understood. This is likely due to two key factors. Firstly, the interaction of the Cu 3d and phthalocyanine ligand 2p electrons leads to the formation of a complex arrangement of localized and delocalized states near the Fermi level. Secondly, thin films of the material are subject to damage by the photon beam used to make measurements of their electronic structure. Using the synchrotron-based techniques of soft x-ray emission spectroscopy (XES) and x-ray photoemission spectroscopy (XPS), we have measured the detailed electronic structure of in-situ grown thin film samples of CuPc. Beam damage was minimized by continuous translation of the sample during data acquisition. The results obtained differ significantly from previous XES and ultraviolet photoemission measurements, but are in excellent agreement with recent density functional calculations. The reasons for these discrepancies will be explained, and their implications for future measurements on similar materials will be explored

Plasma electron density measurement with multichannel microwave interferometer on the HL-1 tokamak device

International Nuclear Information System (INIS)

Xu Deming; Zhang Hongyin; Liu Zetian; Ding Xuantong; Li Qirui; Wen Yangxi

1989-11-01

A multichannel microwave interferometer which is composed of different microwave interferometers (one 2 mm band, one 4 mm band and two 8 mm band) has been used to measure the plasma electron density on HL-1 tokamak device. The electron density approaching to 5 x 10 13 cm -3 is measured by a 2 mm band microwave interferometer. In the determinable range, the electron density profile in the cross-section on HL-1 device has been measured by this interferometer. A microcomputer data processing system is also developed

Measurements of the electron dose distribution near inhomogeneities using a plastic scintillation detector

International Nuclear Information System (INIS)

Wells, C.M.M.; Mackie, T.R.; Podgorsak, M.B.; Holmes, M.A.; Papanikolaou, N.; Reckwerdt, P.J.; Cygler, J.; Rogers, D.W.O.; Bielajew, A.F.; Schmidt, D.G.

1994-01-01

Accurate measurement of the electron dose distribution near an inhomogeneity is difficult with traditional dosimeters which themselves perturb the electron field. The authors tested the performance of a new high resolution, water-equivalent plastic scintillation detector which has ideal properties for this application. A plastic scintillation detector with a 1 mm diameter, 3 mm long cylindrical sensitive volume was used to measure the dose distributions behind standard benchmark inhomogeneities in water phantoms. The plastic scintillator material is more water equivalent than polystyrene in terms of its mass collision stopping power and mass scattering power. Measurements were performed for beams of electrons having initial energies of 6 and 18 MeV at depths from 0.2-4.2 cm behind the inhomogeneities. The detector reveals hot and cold spots behind heterogeneities at resolutions equivalent to typical film digitizer spot sizes. Plots of the dose distributions behind air, aluminum, lead, and formulations for cortical and inner bone-equivalent materials are presented. The plastic scintillation detector is suited for measuring the electron dose distribution near an inhomogeneity. 14 refs., 9 figs

Lead Halide Perovskites as Charge Generation Layers for Electron Mobility Measurement in Organic Semiconductors.

Science.gov (United States)

Love, John A; Feuerstein, Markus; Wolff, Christian M; Facchetti, Antonio; Neher, Dieter

2017-12-06

Hybrid lead halide perovskites are introduced as charge generation layers (CGLs) for the accurate determination of electron mobilities in thin organic semiconductors. Such hybrid perovskites have become a widely studied photovoltaic material in their own right, for their high efficiencies, ease of processing from solution, strong absorption, and efficient photogeneration of charge. Time-of-flight (ToF) measurements on bilayer samples consisting of the perovskite CGL and an organic semiconductor layer of different thickness are shown to be determined by the carrier motion through the organic material, consistent with the much higher charge carrier mobility in the perovskite. Together with the efficient photon-to-electron conversion in the perovskite, this high mobility imbalance enables electron-only mobility measurement on relatively thin application-relevant organic films, which would not be possible with traditional ToF measurements. This architecture enables electron-selective mobility measurements in single components as well as bulk-heterojunction films as demonstrated in the prototypical polymer/fullerene blends. To further demonstrate the potential of this approach, electron mobilities were measured as a function of electric field and temperature in an only 127 nm thick layer of a prototypical electron-transporting perylene diimide-based polymer, and found to be consistent with an exponential trap distribution of ca. 60 meV. Our study furthermore highlights the importance of high mobility charge transporting layers when designing perovskite solar cells.

OTR profile measurement of a LINAC electron beam with portable ultra high-speed camera

International Nuclear Information System (INIS)

Mogi, T.; Nisiyama, S.; Tomioka, S.; Enoto, T.

2004-01-01

We have studied on and developed a portable ultra high-speed camera, and so applied to measurement of a LINAC electron beam. We measured spatial OTR profiles of a LINAC electron beam using this camera with temporal resolution 80ns. (author)

Electron Identification Performance and First Measurement of $W \\to e + \

CERN Document Server

Ueno, Rynichi

2010-01-01

The identification of electrons is important for the ATLAS experiment because electrons are present in many interactions of interest produced at the Large Hadron Collider. A deep knowledge of the detector, the electron identification algorithms, and the calibration techniques are crucial in order to accomplish this task. This thesis work presents a Monte Carlo study using electrons from the W —> e + v process to evaluate the performance of the ATLAS electromagnetic calorimeter. A significant number of electrons was produced in the early ATLAS collision runs at centre-of-mass energies of 900 GeV and 7 TeV between November 2009 and April 2010, and their properties are presented. Finally, a first measurement of W —> e + v process with the ATLAS experiment was successfully accomplished with the first C = 1.0 nb_ 1 of data at the 7 TeV collision energy, and the properties of the W candidates are also detailed.

Electronic property measurements for piezoelectric ceramics. Technical notes

International Nuclear Information System (INIS)

Cain, M.; Stewart, M.; Gee, M.

1998-01-01

A series of measurement notes are presented, with emphasis placed on the technical nature of the testing methodology, for the determination of key electronic properties for piezoelectric ceramic materials that are used as sensors and actuators. The report is segmented into 'sections' that may be read independently from the rest of the report. The following measurement issues are discussed: Polarisation/Electric field (PE) loop measurements including a discussion of commercial and an in-house constructed system that measures PE loops; Dielectric measurements at low and high stress application, including some thermal and stress dependency modelling of piezo materials properties, developed at NPL; Strain measurement techniques developed at CMMT; Charge measurement techniques suitable for PE loop and other data acquisition; PE loop measurement and software analysis developed at CMMT and Manchester University. The primary objective of this report is to provide a framework on which the remainder of the testing procedures are to be developed for measurements of piezoelectric properties at high stress and stress rate. These procedures will be the subject of a future publication. (author)

Spectral measurements of few-electron uranium ions produced and trapped in a high-energy electron beam ion trap

International Nuclear Information System (INIS)

Beiersdorfer, P.

1994-01-01

Measurements of 2s l/2 -2p 3/2 electric dipole and 2p 1/2 -2p 3/2 magnetic dipole and electric quadrupole transitions in U 82+ through U 89+ have been made with a high-resolution crystal spectrometer that recorded the line radiation from stationary ions produced and trapped in a high-energy electron beam ion trap. From the measurements we infer -39.21 ± 0.23 eV for the QED contribution to the 2s 1/2 -2p 3/2 transition energy of lithiumlike U 89+ . A comparison between our measurements and various computations illustrates the need for continued improvements in theoretical approaches for calculating the atomic structure of ions with two or more electrons in the L shell

Measurement of neutrino flux from neutrino-electron elastic scattering

Science.gov (United States)

Park, J.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Galindo, R.; Ghosh, A.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; Martinez Caicedo, D. A.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Osta, J.; Paolone, V.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Wospakrik, M.; Zavala, G.; Zhang, D.; Miner ν A Collaboration

2016-06-01

Muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based νμ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to ˜10 % due to uncertainties in hadron production and focusing. We have isolated a sample of 135 ±17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI νμ flux from 9% to 6%. Our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.

Turbulent ion heating in TCV Tokamak plasmas

International Nuclear Information System (INIS)

Schlatter, Ch.

2009-08-01

charge exchange measurements, by doping the plasma with ion neutralisation targets injected with the diagnostic neutral beam (DNBI), were used to absolutely calibrate the NPA. Advanced modelling of the measured hydrogenic charge exchange spectra with the neutralisation and neutral transport codes KN1D and DOUBLE-TCV permitted a calculation of the absolute neutral density profiles of the plasma species.The energisation and the properties of fast ions were studied in dedicated, low density, cold ion, hot electron plasmas, resonantly heated at the second harmonic of the electron cyclotron frequency. The ion acceleration occurs on a characteristic timescale in the sub-millisecond range and comprises up to 20 % of the plasma ions. The number of fast ions n i s and their effective temperature T i s are found to depend strongly on the bulk and suprathermal electron parameters, in particular T i s ≥ T e b (electron bulk) and n i s ∼ v de (toroidal electron drift speed). The suprathermal electrons, abundantly generated in plasmas subjected to ECCD, are diagnosed with perpendicular and oblique viewing electron cyclotron emission (ECE) antennas and the measured frequency spectra are reconstructed with the relativistic ECE radiation balance code NOTEC-TCV. With steady-state ECRH and ECCD, the fast ion population reaches an equilibrium state. The spatial fast ion temperature profile is broad, of similar shape compared to the bulk ion temperature profile. The hottest suprathermal temperature observed is T i s ≥ 6 keV. Various potential ion acceleration mechanisms were examined for relevance in the TCV parameter range. The simultaneous wave-electron and wave-ion resonances of ion acoustic turbulence (IAT) show the best correlation with the available experimental knowledge. Ion acoustic waves are emitted by the weakly relativistic circulating electrons and are mainly Landau damped onto the ions. Destabilisation of IAT is markedly facilitated by the important degree of

Measurements of low density, high velocity flow by electron beam fluorescence technique

International Nuclear Information System (INIS)

Soga, Takeo; Takanishi, Masaya; Yasuhara, Michiru

1981-01-01

A low density chamber with an electron gun system was made for the measurements of low density, high velocity (high Mach number) flow. This apparatus is a continuous running facility. The number density and the rotational temperature in the underexpanding free jet of nitrogen were measured along the axis of the jet by the electron beam fluorescence technique. The measurements were carried out from the vicinity of the exit of the jet to far downstream of the first Mach disk. Rotational nonequilibrium phenomena were observed in the hypersonic flow field as well as in the shock wave (Mach disk). (author)

Problems in the measurement of electron-dose distribution with film dosimeters inserted into solid materials

International Nuclear Information System (INIS)

Okuda, Shuichi; Fukuda, Kyue; Tabata, Tatsuo; Okabe, Shigeru

1981-01-01

On the insertion of film dosimeters into solid materials, thin air gaps are formed. The influence of such gaps on measured profiles of depth-dose distributions was investigated for aluminum irradiated with collimated beams of 15-MeV electrons. Measurements were made by changing the gap width or the incidence angle of the electrons. The present results showed that streaming of incident electrons through the gaps resulted in the appearance of a peak and a minimum in a depth-dose curve measured. This effect was suppressed by the increase of the angle between the film and the electron-beam axis. (author)

The energy spectrum of cosmic-ray electrons measured with H.E.S.S

International Nuclear Information System (INIS)

Egberts, Kathrin

2009-01-01

The spectrum of cosmic-ray electrons has so far been measured using balloon and satellite-based instruments. At TeV energies, however, the sensitivity of such instruments is very limited due to the low flux of electrons at very high energies and small detection areas of balloon/satellite based experiments. The very large collection area of ground-based imaging atmospheric Cherenkov telescopes gives them a substantial advantage over balloon/ satellite based instruments when detecting very-high-energy electrons (> 300 GeV). By analysing data taken by the High Energy Stereoscopic System (H.E.S.S.), this work extends the known electron spectrum up to 4 TeV - a range that is not accessible to direct measurements. However, in contrast to direct measurements, imaging atmospheric Cherenkov telescopes such as H.E.S.S. detect air showers that cosmic-ray electrons initiate in the atmosphere rather than the primary particle. Thus, the main challenge is to differentiate between air showers initiated by electrons and those initiated by the hadronic background. A new analysis technique was developed that determines the background with the support of the machine-learning algorithm Random Forest. It is shown that this analysis technique can also be applied in other areas such as the analysis of diffuse γ rays from the Galactic plane. (orig.)

The energy spectrum of cosmic-ray electrons measured with H.E.S.S.

Energy Technology Data Exchange (ETDEWEB)

Egberts, Kathrin

2009-03-30

The spectrum of cosmic-ray electrons has so far been measured using balloon and satellite-based instruments. At TeV energies, however, the sensitivity of such instruments is very limited due to the low flux of electrons at very high energies and small detection areas of balloon/satellite based experiments. The very large collection area of ground-based imaging atmospheric Cherenkov telescopes gives them a substantial advantage over balloon/ satellite based instruments when detecting very-high-energy electrons (> 300 GeV). By analysing data taken by the High Energy Stereoscopic System (H.E.S.S.), this work extends the known electron spectrum up to 4 TeV - a range that is not accessible to direct measurements. However, in contrast to direct measurements, imaging atmospheric Cherenkov telescopes such as H.E.S.S. detect air showers that cosmic-ray electrons initiate in the atmosphere rather than the primary particle. Thus, the main challenge is to differentiate between air showers initiated by electrons and those initiated by the hadronic background. A new analysis technique was developed that determines the background with the support of the machine-learning algorithm Random Forest. It is shown that this analysis technique can also be applied in other areas such as the analysis of diffuse {gamma} rays from the Galactic plane. (orig.)

A Novel Electronic Device for Measuring Urine Flow Rate: A Clinical Investigation

OpenAIRE

Aliza Goldman; Hagar Azran; Tal Stern; Mor Grinstein; Dafna Wilner

2017-01-01

Objective: Currently, most vital signs in the intensive care unit (ICU) are electronically monitored. However, clinical practice for urine output (UO) measurement, an important vital sign, usually requires manual recording of data that is subject to human errors. In this study, we assessed the ability of a novel electronic UO monitoring device to measure real-time hourly UO versus current clinical practice. Design: Patients were connected to the RenalSense Clarity RMS Sensor Kit with a sensor...

Fundamental processes in the expansion, energization, and coupling of single- and multi-Ion plasmas in space: Laboratory simulation experiments

Science.gov (United States)

Szuszczewicz, E. P.; Bateman, T. T.

1996-01-01

We have conducted a laboratory investigation into the physics of plasma expansions and their associated energization processes. We studied single- and multi-ion plasma processes in self-expansions, and included light and heavy ions and heavy/light mixtures to encompass the phenomenological regimes of the solar and polar winds and the AMPTE and CRRES chemical release programs. The laboratory experiments provided spatially-distributed time-dependent measurements of total plasma density, temperature, and density fluctuation power spectra with the data confirming the long-theorized electron energization process in an expanding cloud - a result that was impossible to determine in spaceborne experiments (as e.g., in the CRRES program). These results provided the missing link in previous laboratory and spaceborne programs. confirming important elements in our understanding of such solar-terrestrial processes as manifested in expanding plasmas in the solar wind (e.g., CMES) and in ionospheric outflow in plasmaspheric fluctuate refilling after a storm. The energization signatures were seen in an entire series of runs that varied the ion species (Ar', Xe', Kr' and Ne'), and correlative studies included spectral analyses of electrostatic waves collocated with the energized electron distributions. In all cases wave energies were most intense during the times in which the suprathermal populations were present, with wave intensity increasing with the intensity of the suprathermal electron population. This is consistent with theoretical expectations wherein the energization process is directly attributable to wave particle interactions. No resonance conditions were observed, in an overall framework in which the general wave characteristics were broadband with power decreasing with increasing frequency.

Effect of Electron Seeding on Experimentally Measured Multipactor Discharge Threshold

Science.gov (United States)

Noland, Jonathan; Graves, Timothy; Lemon, Colby; Looper, Mark; Farkas, Alex

2012-10-01

Multipactor is a vacuum phenomenon in which electrons, moving in resonance with an externally applied electric field, impact material surfaces. If the number of secondary electrons created per primary electron impact averages more than unity, the resonant interaction can lead to an electron avalanche. Multipactor is a generally undesirable phenomenon, as it can cause local heating, absorb power, or cause detuning of RF circuits. In order to increase the probability of multipactor initiation, test facilities often employ various seeding sources such as radioactive sources (Cesium 137, Strontium 90), electron guns, or photon sources. Even with these sources, the voltage for multipactor initiation is not certain as parameters such as material type, RF pulse length, and device wall thickness can all affect seed electron flux and energy in critical gap regions, and hence the measured voltage threshold. This study investigates the effects of seed electron source type (e.g., photons versus beta particles), material type, gap size, and RF pulse length variation on multipactor threshold. In addition to the experimental work, GEANT4 simulations will be used to estimate the production rate of low energy electrons (< 5 keV) by high energy electrons and photons. A comparison of the experimental fluxes to the typical energetic photon and particle fluxes experienced by spacecraft in various orbits will also be made. Initial results indicate that for a simple, parallel plate device made of aluminum, there is no threshold variation (with seed electrons versus with no seed electrons) under continuous-wave RF exposure.

Measurements of Relativistic Effects in Collective Thomson Scattering at Electron Temperatures less than 1 keV

Energy Technology Data Exchange (ETDEWEB)

Ross, James Steven [Univ. of California, San Diego, CA (United States)

2010-01-01

Simultaneous scattering from electron-plasma waves and ion-acoustic waves is used to measure local laser-produced plasma parameters with high spatiotemporal resolution including electron temperature and density, average charge state, plasma flow velocity, and ion temperature. In addition, the first measurements of relativistic modifications in the collective Thomson scattering spectrum from thermal electron-plasma fluctuations are presented [1]. Due to the high phase velocity of electron-plasma fluctuations, relativistic effects are important even at low electron temperatures (T_e < 1 keV). These effects have been observed experimentally and agree well with a relativistic treatment of the Thomson scattering form factor [2]. The results are important for the interpretation of scattering measurements from laser produced plasmas. Thomson scattering measurements are used to characterize the hydrodynamics of a gas jet plasma which is the foundation for a broad series of laser-plasma interaction studies [3, 4, 5, 6]. The temporal evolution of the electron temperature, density and ion temperature are measured. The measured electron density evolution shows excellent agreement with a simple adiabatic expansion model. The effects of high temperatures on coupling to hohlraum targets is discussed [7]. A peak electron temperature of 12 keV at a density of 4.7 × 10²⁰cm^-3 are measured 200 μm outside the laser entrance hole using a two-color Thomson scattering method we developed in gas jet plasmas [8]. These measurements are used to assess laser-plasma interactions that reduce laser hohlraum coupling and can significantly reduce the hohlraum radiation temperature.