Hotspot electron temperature from x-ray continuum measurements on the NIF

NASA Astrophysics Data System (ADS)

Jarrott, L. C.; Benedetti, L. R.; Chen, H.; Izumi, N.; Khan, S. F.; Ma, T.; Nagel, S. R.; Landen, O. L.; Pak, A.; Patel, P. K.; Schneider, M.; Scott, H. A.

2016-11-01

We report on measurements of the electron temperature in the hotspot of inertially confined, layered, spherical implosions on the National Ignition Facility using a differential filtering diagnostic. Measurements of the DT and DD ion temperatures using neutron time-of-flight detectors are complicated by the contribution of hot spot motion to the peak width, which produce an apparent temperature higher than the thermal temperature. The electron temperature is not sensitive to this non-thermal velocity and is thus a valuable input to interpreting the stagnated hot spot conditions. Here we show that the current differential filtering diagnostic provides insufficient temperature resolution for the hot spot temperatures of interest. We then propose a new differential filter configuration utilizing larger pinhole size to increase spectral fluence, as well as thicker filtration. This new configuration will improve measurement uncertainty by more than a factor of three, allowing for a more accurate hotspot temperature.

Hotspot electron temperature from x-ray continuum measurements on the NIF.

PubMed

Jarrott, L C; Benedetti, L R; Chen, H; Izumi, N; Khan, S F; Ma, T; Nagel, S R; Landen, O L; Pak, A; Patel, P K; Schneider, M; Scott, H A

2016-11-01

We report on measurements of the electron temperature in the hotspot of inertially confined, layered, spherical implosions on the National Ignition Facility using a differential filtering diagnostic. Measurements of the DT and DD ion temperatures using neutron time-of-flight detectors are complicated by the contribution of hot spot motion to the peak width, which produce an apparent temperature higher than the thermal temperature. The electron temperature is not sensitive to this non-thermal velocity and is thus a valuable input to interpreting the stagnated hot spot conditions. Here we show that the current differential filtering diagnostic provides insufficient temperature resolution for the hot spot temperatures of interest. We then propose a new differential filter configuration utilizing larger pinhole size to increase spectral fluence, as well as thicker filtration. This new configuration will improve measurement uncertainty by more than a factor of three, allowing for a more accurate hotspot temperature.

Suppression of electron temperature gradient turbulence via negative magnetic shear in NSTX.

PubMed

Yuh, H Y; Kaye, S M; Levinton, F M; Mazzucato, E; Mikkelsen, D R; Smith, D R; Bell, R E; Hosea, J C; LeBlanc, B P; Peterson, J L; Park, H K; Lee, W

2011-02-04

Negative magnetic shear is found to suppress electron turbulence and improve electron thermal transport for plasmas in the National Spherical Torus Experiment (NSTX). Sufficiently negative magnetic shear results in a transition out of a stiff profile regime. Density fluctuation measurements from high-k microwave scattering are verified to be the electron temperature gradient (ETG) mode by matching measured rest frequency and linear growth rate to gyrokinetic calculations. Fluctuation suppression under negligible E×B shear conditions confirm that negative magnetic shear alone is sufficient for ETG suppression. Measured electron temperature gradients can significantly exceed ETG critical gradients with ETG mode activity reduced to intermittent bursts, while electron thermal diffusivity improves to below 0.1 electron gyro-Bohms.

Validation of ISS Floating Potential Measurement Unit Electron Densities and Temperatures

NASA Technical Reports Server (NTRS)

Coffey, Victoria N.; Minow, Joseph I.; Parker, Linda N.; Bui, Them; Wright, Kenneth, Jr.; Koontz, Steven L.; Schneider, T.; Vaughn, J.; Craven, P.

2007-01-01

Validation of the Floating Potential Measurement Unit (FPMU) electron density and temperature measurements is an important step in the process of evaluating International Space Station spacecraft charging issues .including vehicle arcing and hazards to crew during extravehicular activities. The highest potentials observed on Space Station are due to the combined VxB effects on a large spacecraft and the collection of ionospheric electron and ion currents by the 160 V US solar array modules. Ionospheric electron environments are needed for input to the ISS spacecraft charging models used to predict the severity and frequency of occurrence of ISS charging hazards. Validation of these charging models requires comparing their predictions with measured FPMU values. Of course, the FPMU measurements themselves must also be validated independently for use in manned flight safety work. This presentation compares electron density and temperatures derived from the FPMU Langmuir probes and Plasma Impedance Probe against the independent density and temperature measurements from ultraviolet imagers, ground based incoherent scatter radar, and ionosonde sites.

Thomson scattering diagnostics of thermal plasmas: Laser heating of electrons and the existence of local thermodynamic equilibrium.

PubMed

Murphy, A B

2004-01-01

A number of assessments of electron temperatures in atmospheric-pressure arc plasmas using Thomson scattering of laser light have recently been published. However, in this method, the electron temperature is perturbed due to strong heating of the electrons by the incident laser beam. This heating was taken into account by measuring the electron temperature as a function of the laser pulse energy, and linearly extrapolating the results to zero pulse energy to obtain an unperturbed electron temperature. In the present paper, calculations show that the laser heating process has a highly nonlinear dependence on laser power, and that the usual linear extrapolation leads to an overestimate of the electron temperature, typically by 5000 K. The nonlinearity occurs due to the strong dependence on electron temperature of the absorption of laser energy and of the collisional and radiative cooling of the heated electrons. There are further problems in deriving accurate electron temperatures from laser scattering due to necessary averages that have to be made over the duration of the laser pulse and over the finite volume from which laser light is scattered. These problems are particularly acute in measurements in which the laser beam is defocused in order to minimize laser heating; this can lead to the derivation of electron temperatures that are significantly greater than those existing anywhere in the scattering volume. It was concluded from the earlier Thomson scattering measurements that there were significant deviations from equilibrium between the electron and heavy-particle temperatures at the center of arc plasmas of industrial interest. The present calculations indicate that such deviations are only of the order of 1000 K in 20 000 K, so that the usual approximation that arc plasmas are approximately in local thermodynamic equilibrium still applies.

Role of electron-phonon coupling in finite-temperature dielectric functions of Au, Ag, and Cu

NASA Astrophysics Data System (ADS)

Xu, Meng; Yang, Jia-Yue; Zhang, Shangyu; Liu, Linhua

2017-09-01

Realistic representation of finite temperature dielectric functions of noble metals is crucial in describing the optical properties of advancing applications in plasmonics and optical metamaterials. However, the atomistic origins of the temperature dependence of noble metals' dielectric functions still lack full explanation. In this paper, we implement electronic structure calculations as well as ellipsometry experiments to study the finite temperature dielectric functions of noble metals Au, Ag, and Cu. Theoretically, the intraband dielectric function is described by the Drude model, of which the important quantity electron lifetime is obtained by considering the electron-phonon, electron-electron, and electron-surface scattering mechanism. The electron-phonon coupling is key to determining the temperature dependence of electron lifetime and intraband dielectric function. For the interband dielectric function, it arises from the electronic interband transition. Due to the limitation of incorporating electron-phonon coupling into the interband transition scheme, the temperature dependence of the interband dielectric function is mainly determined by the thermal expansion effect. Experimentally, variable angle spectroscopic ellipsometry measures the dielectric functions of Au and Ag over the temperature range of 300-700 K and spectral range of 2-20 µm. Those experimental measurements are consistent with theoretical results and thus verify the theoretical models for the finite temperature dielectric function.

Heat-Flux Measurements from Collective Thomson-Scattering Spectra

NASA Astrophysics Data System (ADS)

Henchen, R. J.; Hu, S. X.; Katz, J.; Froula, D. H.; Rozmus, W.

2015-11-01

Collective Thomson scattering was used to measure heat flux in coronal plasmas. The relative amplitude of the Thomson-scattered power into the up- and downshifted electron plasma wave features was used to determine the flux of electrons moving along the temperature gradient at three to four times the electron thermal velocity. Simultaneously, the ion-acoustic wave features were measured. Their relative amplitude is used to measure the flux of the return-current electrons. The frequencies of these ion-acoustic and electron plasma wave features provide local measurements of the electron temperature and density. These spectra were obtained at five locations along the temperature gradient in a laser-produced blowoff plasma. These measurements of plasma parameters are used to infer the Spitzer -Härm flux qSH = - κ∇Te and are in good agreement with the values of the heat flux measured from the scattering-feature asymmetries. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

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

NASA Technical Reports Server (NTRS)

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.;

Temperature measurement systems in wearable electronics

NASA Astrophysics Data System (ADS)

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.

Determination of electron temperature in a penning discharge by the helium line ratio method

NASA Technical Reports Server (NTRS)

Richardson, R. W.

1975-01-01

The helium line ratio technique was used to determine electron temperatures in a toroidal steady-state Penning discharge operating in helium. Due to the low background pressure, less than .0001 torr, and the low electron density, the corona model is expected to provide a good description of the excitation processes in this discharge. In addition, by varying the Penning discharge anode voltage and background pressure, it is possible to vary the electron temperature as measured by the line ratio technique over a wide range (10 to 100+ eV). These discharge characteristics allow a detailed comparison of electron temperatures measured from different possible line ratios over a wide range of temperatures and under reproducible steady-state conditions. Good agreement is found between temperatures determined from different neutral line ratios, but use of the helium ion line results in a temperature systematically 10 eV high compared to that from the neutral lines.

[Temperature measurement of DC argon plasma jet].

PubMed

Yan, Jian-Hua; Pan, Xin-Chao; Ma, Zeng-Yi; Tu, Xin; Cen, Ke-Fa

2008-01-01

The electron temperature of DC arc plasma jet is an important parameter, which determines the characteristics of plasma jet. The measurement of emission spectrum was performed to obtain the spectral intensities of some Ar lines and the method of diagrammatic view of Boltzmann was adopted to calculate the electron temperature. The results indicated that the electron temperature dropped at different speed along with the axes of the plasma jet and rose rapidly when the current was increased, and it also rose when the flowrate of argon was increased.

Estimation of reliable range of electron temperature measurements with sets of given optical bandpass filters for KSTAR Thomson scattering system based on synthetic Thomson data

NASA Astrophysics Data System (ADS)

Kim, K.-h.; Oh, T.-s.; Park, K.-r.; Lee, J. H.; Ghim, Y.-c.

2017-11-01

One factor determining the reliability of measurements of electron temperature using a Thomson scattering (TS) system is transmittance of the optical bandpass filters in polychromators. We investigate the system performance as a function of electron temperature to determine reliable range of measurements for a given set of the optical bandpass filters. We show that such a reliability, i.e., both bias and random errors, can be obtained by building a forward model of the KSTAR TS system to generate synthetic TS data with the prescribed electron temperature and density profiles. The prescribed profiles are compared with the estimated ones to quantify both bias and random errors.

Measurement of electron temperature and density of the edge plasma of JET by ECE and microwave reflectometry

NASA Astrophysics Data System (ADS)

Bartlett, D. V.; Costley, A. E.; Porte, L.; Prentice, R.; Salmon, N. A.; Sips, G.

1990-12-01

The potential of electron cyclotron emission and microwave reflectometry as techniques for measuring the electron temperature and density in the edge region of tokamak plasmas is investigated. Experiments to realize this potential on JET are described and some illustrative results presented.

Hotspot electron temperature from x-ray continuum measurements on the NIF

DOE PAGES

Jarrott, L. C.; Benedetti, L. R.; Chen, H.; ...

2016-08-24

We report on measurements of the electron temperature in the hotspot of inertially confined, layered, spherical implosions on the National Ignition Facility using a differential filtering diagnostic. Measurements of the DT and DD ion temperatures using neutron time-of-flight detectors are complicated by the contribution of hot spot motion to the peak width, which produce an apparent temperature higher than the thermal temperature. The electron temperature is not sensitive to this non-thermal velocity and is thus a valuable input to interpreting the stagnated hot spot conditions. Here we show that the current differential filtering diagnostic provides insufficient temperature resolution for themore » hot spot temperatures of interest. We then propose a new differential filter configuration utilizing larger pinhole size to increase spectral fluence, as well as thicker filtration. In conclusion, this new configuration will improve measurement uncertainty by more than a factor of three, allowing for a more accurate hotspot temperature.« less

Retarding field energy analyzer for the Saskatchewan Torus-Modified plasma boundary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dreval, M.; Rohraff, D.; Xiao, C.

2009-10-15

The retarding field energy analyzer (RFA) is a simple and reliable diagnostic technique to measure the ion temperature in the scrape-off layer and edge of magnetic fusion devices. Design and operation features of a single-sided (facing the ion flow) RFA for ion temperature measurements in the Saskatchewan Torus-Modified (STOR-M) tokamak are described. Its compact size (21x15x20 mm{sup 3}) allows RFA measurements without perturbing plasma significantly. Both ion and electron temperature have been measured by RFA in the STOR-M tokamak. A method is proposed to correct the effects of ion flow on the ion temperature using the simultaneously measured Mach number.more » The measured electron temperature is consistent with the previously reported Langmuir probe data. Abnormal behavior of the RFA has been observed in both ion and electron modes when RFA is inserted deep into the plasma.« less

Ion and electron temperatures in the SUMMA mirror device by emission spectroscopy

NASA Technical Reports Server (NTRS)

Patch, R. W.; Voss, D. E.; Reinmann, J. J.; Snyder, A.

1974-01-01

Ion and electron temperatures, and ion drift were measured in a superconducting magnetic mirror apparatus by observing the Doppler-broadened charge-exchange component of the 667.8 and 587.6 nanometer He lines in He plasma, and the H sub alpha and H sub beta lines in H2 plasma. The second moment of the line profiles was used as the parameter for determining ion temperature. Corrections for magnetic splitting, fine structure, monochromator slit function, and variation in charge-exchange cross section with energy are included. Electron temperatures were measured by the line ratio method for the corona model, and correlations of ion and electron temperatures with plasma parameters are presented.

Method for local temperature measurement in a nanoreactor for in situ high-resolution electron microscopy.

PubMed

Vendelbo, S B; Kooyman, P J; Creemer, J F; Morana, B; Mele, L; Dona, P; Nelissen, B J; Helveg, S

2013-10-01

In situ high-resolution transmission electron microscopy (TEM) of solids under reactive gas conditions can be facilitated by microelectromechanical system devices called nanoreactors. These nanoreactors are windowed cells containing nanoliter volumes of gas at ambient pressures and elevated temperatures. However, due to the high spatial confinement of the reaction environment, traditional methods for measuring process parameters, such as the local temperature, are difficult to apply. To address this issue, we devise an electron energy loss spectroscopy (EELS) method that probes the local temperature of the reaction volume under inspection by the electron beam. The local gas density, as measured using quantitative EELS, is combined with the inherent relation between gas density and temperature, as described by the ideal gas law, to obtain the local temperature. Using this method we determined the temperature gradient in a nanoreactor in situ, while the average, global temperature was monitored by a traditional measurement of the electrical resistivity of the heater. The local gas temperatures had a maximum of 56 °C deviation from the global heater values under the applied conditions. The local temperatures, obtained with the proposed method, are in good agreement with predictions from an analytical model. Copyright © 2013 Elsevier B.V. All rights reserved.

Hot spot temperature measurements in DT layered implosions

NASA Astrophysics Data System (ADS)

Patel, Pravesh; Ma, T.; Macphee, A.; Callahan, D.; Chen, H.; Cerjan, C.; Clark, D.; Edgell, D.; Hurricane, O.; Izumi, N.; Khan, S.; Jarrott, L.; Kritcher, A.; Springer, P.

2015-11-01

The temperature of the burning DT hot spot in an ICF implosion is a crucial parameter in understanding the thermodynamic conditions of the fuel at stagnation and and the performance of the implosion in terms of alpha-particle self-heating and energy balance. The continuum radiation spectrum emitted from the hot spot provides an accurate measure of the emissivity-weighted electron temperature. Absolute measurements of the emitted radiation are made with several independent instruments including spatially-resolved broadband imagers, and space- and time-integrated monochromatic detectors. We present estimates of the electron temperature in DT layered implosions derived from the radiation spectrum most consistent with the available measurements. The emissivity-weighted electron temperatures are compared to the neutron-averaged apparent ion temperatures inferred from neutron time-of-flight detectors. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Temperature gradient scale length measurement: A high accuracy application of electron cyclotron emission without calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Houshmandyar, S., E-mail: houshmandyar@austin.utexas.edu; Phillips, P. E.; Rowan, W. L.

2016-11-15

Calibration is a crucial procedure in electron temperature (T{sub e}) inference from a typical electron cyclotron emission (ECE) diagnostic on tokamaks. Although the calibration provides an important multiplying factor for an individual ECE channel, the parameter ΔT{sub e}/T{sub e} is independent of any calibration. Since an ECE channel measures the cyclotron emission for a particular flux surface, a non-perturbing change in toroidal magnetic field changes the view of that channel. Hence the calibration-free parameter is a measure of T{sub e} gradient. B{sub T}-jog technique is presented here which employs the parameter and the raw ECE signals for direct measurement ofmore » electron temperature gradient scale length.« less

Thermometry of Silicon Nanoparticles

NASA Astrophysics Data System (ADS)

Mecklenburg, Matthew; Zutter, Brian; Regan, B. C.

2018-01-01

Current thermometry techniques lack the spatial resolution required to see the temperature gradients in typical, highly scaled modern transistors. As a step toward addressing this problem, we measure the temperature dependence of the volume plasmon energy in silicon nanoparticles from room temperature to 1250 °C , using a chip-style heating sample holder in a scanning transmission electron microscope (STEM) equipped with electron energy loss spectroscopy (EELS). The plasmon energy changes as expected for an electron gas subject to the thermal expansion of silicon. Reversing this reasoning, we find that measurements of the plasmon energy provide an independent measure of the nanoparticle temperature consistent with that of the heater chip's macroscopic, dual-function heater-and-thermometer to within the 5% accuracy of the thermometer's calibration. Thus, silicon has the potential to provide its own high-spatial-resolution thermometric readout signal via measurements of its volume plasmon energy. Furthermore, nanoparticles can, in general, serve as convenient nanothermometers for in situ electron-microscopy experiments.

Development of an Integrated Thermocouple for the Accurate Sample Temperature Measurement During High Temperature Environmental Scanning Electron Microscopy (HT-ESEM) Experiments.

PubMed

Podor, Renaud; Pailhon, Damien; Ravaux, Johann; Brau, Henri-Pierre

2015-04-01

We have developed two integrated thermocouple (TC) crucible systems that allow precise measurement of sample temperature when using a furnace associated with an environmental scanning electron microscope (ESEM). Sample temperatures measured with these systems are precise (±5°C) and reliable. The TC crucible systems allow working with solids and liquids (silicate melts or ionic liquids), independent of the gas composition and pressure. These sample holder designs will allow end users to perform experiments at high temperature in the ESEM chamber with high precision control of the sample temperature.

Nanoelectronic primary thermometry below 4 mK

PubMed Central

Bradley, D. I.; George, R. E.; Gunnarsson, D.; Haley, R. P.; Heikkinen, H.; Pashkin, Yu. A.; Penttilä, J.; Prance, J. R.; Prunnila, M.; Roschier, L.; Sarsby, M.

2016-01-01

Cooling nanoelectronic structures to millikelvin temperatures presents extreme challenges in maintaining thermal contact between the electrons in the device and an external cold bath. It is typically found that when nanoscale devices are cooled to ∼10 mK the electrons are significantly overheated. Here we report the cooling of electrons in nanoelectronic Coulomb blockade thermometers below 4 mK. The low operating temperature is attributed to an optimized design that incorporates cooling fins with a high electron–phonon coupling and on-chip electronic filters, combined with low-noise electronic measurements. By immersing a Coulomb blockade thermometer in the 3He/4He refrigerant of a dilution refrigerator, we measure a lowest electron temperature of 3.7 mK and a trend to a saturated electron temperature approaching 3 mK. This work demonstrates how nanoelectronic samples can be cooled further into the low-millikelvin range. PMID:26816217

Performance of a flight qualified, thermoelectrically temperature controlled QCM sensor with power supply, thermal controller and signal processor

NASA Technical Reports Server (NTRS)

Wallace, D. A.

1980-01-01

A thermoelectrically temperature controlled quartz crystal microbalance (QCM) system was developed for the measurement of ion thrustor generated mercury contamination on spacecraft. Meaningful flux rate measurements dictated an accurately held sensing crystal temperature despite spacecraft surface temperature variations from -35 C to +60 C over the flight temperature range. An electronic control unit was developed with magentic amplifier transformer secondary power supply, thermal control electronics, crystal temperature analog conditioning and a multiplexed 16 bit frequency encoder.

Correlation electron cyclotron emission diagnostic and improved calculation of turbulent temperature fluctuation levels on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Creely, A. J.; Freethy, S. J.; Burke, W. M.; Conway, G. D.; Leccacorvi, R.; Parkin, W. C.; Terry, D. R.; White, A. E.

2018-05-01

A newly upgraded correlation electron cyclotron emission (CECE) diagnostic has been installed on the ASDEX Upgrade tokamak and has begun to perform experimental measurements of electron temperature fluctuations. CECE diagnostics measure small amplitude electron temperature fluctuations by correlating closely spaced heterodyne radiometer channels. This upgrade expanded the system from six channels to thirty, allowing simultaneous measurement of fluctuation level radial profiles without repeat discharges, as well as opening up the possibility of measuring radial turbulent correlation lengths. Newly refined statistical techniques have been developed in order to accurately analyze the fluctuation data collected from the CECE system. This paper presents the hardware upgrades for this system and the analysis techniques used to interpret the raw data, as well as measurements of fluctuation spectra and fluctuation level radial profiles.

Ion acceleration and non-Maxwellian electron distributions in a low collisionality, high power helicon plasma source

NASA Astrophysics Data System (ADS)

Li, Yan; Sung, Yung-Ta; Scharer, John

2015-11-01

Ion acceleration through plasma double layer and non-Maxwellian two temperature electron distributions have been observed in Madison Helicon Experiment (MadHeX) operated in high RF power (>1000 W) and low Ar pressure (0.17 mtorr) inductive mode. By applying Optical Emission Spectroscopy (OES) cross-checked with an RF-compensated Langmuir probe (at 13.56 MHz and its second and third harmonics), the fast (>80 eV), untrapped electrons downstream of the double layer have a higher temperature of 13 eV than the trapped bulk electrons upstream with a temperature of 4 eV. The reduction of plasma potential and density observed in the double layer region require an upstream temperature ten times the measured 4 eV if occurring via Boltzmann ambipolar expansion. The hot tail electrons of the non-Maxwellian electron distribution affect the formation and the potential drop of the double layer region. The mechanism behind this has been explored via several non-invasive plasma diagnostics tools. The OES measured electron temperatures and densities are also cross-checked with Atomic Data and Analysis Structure (ADAS) and a millimeter wave interferometer respectively. The IEDF is measured by a four-grid RPA and also cross-checked with argon 668 nm Laser Induced Fluorescence (LIF). An emissive probe has been used to measure the plasma potential.

Measurement and interpretation of electron angle at mabe beam stop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanford, T.W.L.; Coleman, P.D.; Poukey, J.W.

1985-10-01

This analysis shows that radiation measurements combined with a sophisticated simulation provides a simple but powerful tool for estimating beam temperature in intense pulsed annular electron-beam accelerators. Specifically, the mean angle of incidence of a 60 kA, 7 MeV annular electron-beam at the beam stop of the MABE accelerator and the transverse beam temperature are determined. The angle is extracted by comparing dose profiles measured downstream of the stop with that expected from a simulation of the electron/photon transport in the stop. By calculating and removing the effect on the trajectories due to the change in electric field near themore » stop, the beam temperature is determined. Such measurements help give insight to beam generation and propagation within the accelerator.« less

Optimization of Pulsed-DEER Measurements for Gd-Based Labels: Choice of Operational Frequencies, Pulse Durations and Positions, and Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raitsimring, A.; Astashkin, A. V.; Enemark, J. H.

2012-12-29

In this work, the experimental conditions and parameters necessary to optimize the long-distance (≥ 60 Å) Double Electron-Electron Resonance (DEER) measurements of biomacromolecules labeled with Gd(III) tags are analyzed. The specific parameters discussed are the temperature, microwave band, the separation between the pumping and observation frequencies, pulse train repetition rate, pulse durations and pulse positioning in the electron paramagnetic resonance spectrum. It was found that: (i) in optimized DEER measurements, the observation pulses have to be applied at the maximum of the EPR spectrum; (ii) the optimal temperature range for Ka-band measurements is 14-17 K, while in W-band the optimalmore » temperatures are between 6-9 K; (iii) W-band is preferable to Ka-band for DEER measurements. Recent achievements and the conditions necessary for short-distance measurements (<15 Å) are also briefly discussed.« less

Electron temperature diagnostics of aluminium plasma in a z-pinch experiment at the “QiangGuang-1" facility

NASA Astrophysics Data System (ADS)

Li, Mo; Wu, Jian; Wang, Liang-Ping; Wu, Gang; Han, Juan-Juan; Guo, Ning; Qiu, Meng-Tong

2012-12-01

Two curved crystal spectrometers are set up on the “QiangGuang-1" generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several “bright spots" indicate electron temperatures between (450 eV ~ 520 eV) ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV ± 30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a ~ 1 MA facility.

Decay of the electron number density in the nitrogen afterglow using a hairpin resonator probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siefert, Nicholas S.; Ganguly, Biswa N.; Sands, Brian L.

A hairpin resonator was used to measure the electron number density in the afterglow of a nitrogen glow discharge (p=0.25-0.75 Torr). Electron number densities were measured using a time-dependent approach similar to the approach used by Spencer et al. [J. Phys. D 20, 923 (1987)]. The decay time of the electron number density was used to determine the electron temperature in the afterglow, assuming a loss of electrons via ambipolar diffusion to the walls. The electron temperature in the near afterglow remained between 0.4 and 0.6 eV, depending on pressure. This confirms the work by Guerra et al. [IEEE Trans.more » Plasma. Sci. 31, 542 (2003)], who demonstrated experimentally and numerically that the electron temperature stays significantly above room temperature via superelastic collisions with highly vibrationally excited ground state molecules and metastables, such as A {sup 3}{sigma}{sub u}{sup +}.« less

Profile measurements of the electron temperature on the ASDEX Upgrade, COMPASS, and ISTTOK tokamak using Thomson scattering, triple, and ball-pen probes

NASA Astrophysics Data System (ADS)

Adamek, J.; Müller, H. W.; Silva, C.; Schrittwieser, R.; Ionita, C.; Mehlmann, F.; Costea, S.; Horacek, J.; Kurzan, B.; Bilkova, P.; Böhm, P.; Aftanas, M.; Vondracek, P.; Stöckel, J.; Panek, R.; Fernandes, H.; Figueiredo, H.

2016-04-01

The ball-pen probe (BPP) technique is used successfully to make profile measurements of the electron temperature on the ASDEX Upgrade (Axially Symmetric Divertor Experiment), COMPASS (COMPact ASSembly), and ISTTOK (Instituto Superior Tecnico TOKamak) tokamak. The electron temperature is provided by a combination of the BPP potential (ΦBPP) and the floating potential (Vfl) of the Langmuir probe (LP), which is compared with the Thomson scattering diagnostic on ASDEX Upgrade and COMPASS. Excellent agreement between the two diagnostics is obtained for circular and diverted plasmas and different heating mechanisms (Ohmic, NBI, ECRH) in deuterium discharges with the same formula Te = (ΦBPP - Vfl)/2.2. The comparative measurements of the electron temperature using BPP/LP and triple probe (TP) techniques on the ISTTOK tokamak show good agreement of averaged values only inside the separatrix. It was also found that the TP provides the electron temperature with significantly higher standard deviation than BPP/LP. However, the resulting values of both techniques are well in the phase with the maximum of cross-correlation function being 0.8.

Profile measurements of the electron temperature on the ASDEX Upgrade, COMPASS, and ISTTOK tokamak using Thomson scattering, triple, and ball-pen probes.

PubMed

Adamek, J; Müller, H W; Silva, C; Schrittwieser, R; Ionita, C; Mehlmann, F; Costea, S; Horacek, J; Kurzan, B; Bilkova, P; Böhm, P; Aftanas, M; Vondracek, P; Stöckel, J; Panek, R; Fernandes, H; Figueiredo, H

2016-04-01

The ball-pen probe (BPP) technique is used successfully to make profile measurements of the electron temperature on the ASDEX Upgrade (Axially Symmetric Divertor Experiment), COMPASS (COMPact ASSembly), and ISTTOK (Instituto Superior Tecnico TOKamak) tokamak. The electron temperature is provided by a combination of the BPP potential (ΦBPP) and the floating potential (Vfl) of the Langmuir probe (LP), which is compared with the Thomson scattering diagnostic on ASDEX Upgrade and COMPASS. Excellent agreement between the two diagnostics is obtained for circular and diverted plasmas and different heating mechanisms (Ohmic, NBI, ECRH) in deuterium discharges with the same formula Te = (ΦBPP - Vfl)/2.2. The comparative measurements of the electron temperature using BPP/LP and triple probe (TP) techniques on the ISTTOK tokamak show good agreement of averaged values only inside the separatrix. It was also found that the TP provides the electron temperature with significantly higher standard deviation than BPP/LP. However, the resulting values of both techniques are well in the phase with the maximum of cross-correlation function being 0.8.

High temperature electrons exhausted from rf plasma sources along a magnetic nozzle

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Akahoshi, Hikaru; Charles, Christine; Boswell, Rod W.; Ando, Akira

2017-08-01

Two dimensional profiles of electron temperature are measured inside and downstream of a radiofrequency plasma thruster source having a magnetic nozzle and being immersed in vacuum. The temperature is estimated from the slope of the fully swept I-V characteristics of a Langmuir probe acquired at each spatial position and with the assumption of a Maxwellian distribution. The results show that the peripheral high temperature electrons in the magnetic nozzle originate from the upstream antenna location and are transported along the "connecting" magnetic field lines. Two-dimensional measurements of electron energy probability functions are also carried out in a second simplified laboratory device consisting of the source contiguously connected to the diffusion chamber: again the high temperature electrons are detected along the magnetic field lines intersecting the wall at the antenna location, even when the antenna location is shifted along the main axis. These results demonstrate that the peripheral energetic electrons in the magnetic nozzle mirror those created in the source tube.

Moderate temperature-dependent surface and volume resistivity and low-frequency dielectric constant measurements of pure and multi-walled carbon nanotube (MWCNT) doped polyvinyl alcohol thin films

NASA Astrophysics Data System (ADS)

Edwards, Matthew; Guggilla, Padmaja; Reedy, Angela; Ijaz, Quratulann; Janen, Afef; Uba, Samuel; Curley, Michael

2017-08-01

Previously, we have reported measurements of temperature-dependent surface resistivity of pure and multi-walled carbon nanotube (MWNCT) doped amorphous Polyvinyl Alcohol (PVA) thin films. In the temperature range from 22 °C to 40 °C with humidity-controlled environment, we found the surface resistivity to decrease initially, but to rise steadily as the temperature continued to increase. Moreover, electric surface current density (Js) was measured on the surface of pure and MWCNT doped PVA thin films. In this regard, the surface current density and electric field relationship follow Ohm's law at low electric fields. Unlike Ohmic conduction in metals where free electrons exist, selected captive electrons are freed or provided from impurities and dopants to become conduction electrons from increased thermal vibration of constituent atoms in amorphous thin films. Additionally, a mechanism exists that seemingly decreases the surface resistivity at higher temperatures, suggesting a blocking effect for conducting electrons. Volume resistivity measurements also follow Ohm's law at low voltages (low electric fields), and they continue to decrease as temperatures increase in this temperature range, differing from surface resistivity behavior. Moreover, we report measurements of dielectric constant and dielectric loss as a function of temperature and frequency. Both the dielectric constant and dielectric loss were observed to be highest for MWCNT doped PVA compared to pure PVA and commercial paper, and with frequency and temperature for all samples.

Multi-channel retarding field analyzer for EAST

NASA Astrophysics Data System (ADS)

M, HENKEL; D, HÖSCHEN; Y, LIANG; Y, LI; S, C. LIU; D, NICOLAI; N, SANDRI; G, SATHEESWARAN; N, YAN; H, X. ZHANG; the EAST, team2

2018-05-01

A multi-channel retarding field analyzer (MC-RFA) including two RFA modules and two Langmuir probes to measure the ion and electron temperature profiles within the scrape-off layer was developed for investigations of the interplay between magnetic topology and plasma transport at the plasma boundary. The MC-RFA probe for the stellarator W7-X and first measurements at the tokamak EAST was designed. The probe head allows simultaneous multi-channel ion temperature as well as for electron temperature measurements. The usability for radial correlation measurements of the measured ion currents is also given.

Electronic anisotropies revealed by detwinned angle-resolved photo-emission spectroscopy measurements of FeSe

NASA Astrophysics Data System (ADS)

Watson, Matthew D.; Haghighirad, Amir A.; Rhodes, Luke C.; Hoesch, Moritz; Kim, Timur K.

2017-10-01

We report high resolution angle-resolved photo-emission spectroscopy (ARPES) measurements of detwinned FeSe single crystals. The application of a mechanical strain is used to promote the volume fraction of one of the orthorhombic domains in the sample, which we estimate to be 80 % detwinned. While the full structure of the electron pockets consisting of two crossed ellipses may be observed in the tetragonal phase at temperatures above 90 K, we find that remarkably, only one peanut-shaped electron pocket oriented along the longer a axis contributes to the ARPES measurement at low temperatures in the nematic phase, with the expected pocket along b being not observed. Thus the low temperature Fermi surface of FeSe as experimentally determined by ARPES consists of one elliptical hole pocket and one orthogonally-oriented peanut-shaped electron pocket. Our measurements clarify the long-standing controversies over the interpretation of ARPES measurements of FeSe.

Statistical analysis of solar wind stream interface induced temperature effects on the upper mesosphere and lower thermosphere over SANAE IV, Antarctica

NASA Astrophysics Data System (ADS)

Ogunjobi, Olakunle; Sivakumar, Venkataraman; William; Sivla, T.

Using superposed epoch techniques, the TIMED (Thermosphere Ionosphere Mesosphere Energetic and Dynamics) and NOAA 15-18 (National Oceanic and Atmospheric Administration) satellites measurements are used to examine the response of the polar MLT (Mesosphere and Lower Thermosphere) temperature to energetic electron precipitation during solar wind stream interfaces (SI). We first investigate the relationship between the ionospheric absorption from the ground based riometer and degree of energetic electron precipitation from the MEPED (Medium Energy Proton and Electron Detectors) on board the NOAA satellites. By interpolating the energetic electron measurements from MEPED instruments, we can obtain the electron precipitation rates close in time to the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) temperature retrieval. Using measurements sorted over the vicinity of SANAE IV (South Africa National Antarctic Expedition IV), we investigate if there are significant temperature effects in the MLT altitude on SI arrival at Earth. The preliminary analysis indicate that there are no temperature increase below 100 km prior to the SI triggered precipitation; whereas a clear temperature increase is observed at 95 km immediately after the SI impact. The analysis on the SI geophysical properties indicates that an enhanced magnetospheric convection resulting to heating could be responsible for the temperature modification on SI arrival.

Linear magneto-resistance in Bi{sub 2}SeTe{sub 2} topological insulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amaladass, E. P., E-mail: edward@igcar.gov.in; Sharma, Shilpam; Devidas, T. R.

2016-05-23

Magnetic field and temperature dependent electronic transport measurements have been carried out on Bi{sub 2}SeTe{sub 2} topological insulator single crystals. The measurements reveal an insulating behavior and the carriers were found to be electrons (n-type) from Hall measurement. Magneto-resistance (MR) measurements in the field range (B) of 15 T to -15 T carried out at 4.2 K showed a cusp like weak anti-localization behavior for lower fields (-5 T 5 T. Upon increasing temperature, MR transforms to linear dependence of B at 40, 50 and 100 K. On further increasing temperatures (> 200 K), a parabolic MR is observed. Temperaturemore » dependent Hall data also showed a transition from a nonlinear to linear behavior upon increasing temperatures. Disorder induced changes in the electronic transport characteristics of bulk and surface electrons are believed to cause such changes in the magneto-transport behavior of this system.« less

Measurement and interpretation of electron angle at MABE beam stop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanford, T.W.L.; Coleman, P.D.; Poukey, J.W.

1985-01-01

This analysis shows that radiation measurements combined with a sophisticated simulation provides a simple but powerful tool for estimating beam temperature in intense pulsed annular electron-beam accelerators. Specifically, the mean angle of incidence of a 60 kA, 7 MeV annular electron-beam at the beam stop of the MABE accelerator and the transverse beam temperature are determined. The angle is extracted by comparing dose profiles measured downstream of the stop with that expected from a simulation of the electron/photon transport in the stop. By calculating and removing the effect on the trajectories due to the change in electric field near themore » stop, the beam temperature is determined. Such measurements help give insight to beam generation and propagation within the accelerator. 9 refs., 6 figs., 1 tab.« less

Improved understanding of the ball-pen probe through particle-in-cell simulations

NASA Astrophysics Data System (ADS)

Murphy-Sugrue, S.; Harrison, J.; Walkden, N. R.; Bryant, P.; Bradley, J. W.

2017-05-01

Ball-pen probes (BPP) have been deployed in the SOL of numerous tokamak experiments and low-temperature magnetised plasmas to make direct measurements of the plasma potential and electron temperature. Despite strong empirical evidence for the success of the BPP it lacks a theoretical underpinning of its collection mechanism. In this paper we investigate the capability of the probe to measure the plasma potential by means of particle-in-cell simulations. The BPP is found to float at a potential offset from the plasma potential by a factor {T}{{e}}{α }{{BPP}}. By simulating BPPs and Langmuir probes, excellent agreement has been found between the measured electron temperature and the specified source temperature. The transport mechanism for both ions and electrons has been determined. E × B drifts are observed to drive electrons and ions down the tunnel. This mechanism is sensitive to the diameter of the probe.

Development of a Method for Local Electron Temperature and Density Measurements in the Divertor of the JET Tokamak

NASA Technical Reports Server (NTRS)

Jupen, C.; Meigs, A.; Bhatia, A. K.; Brezinsek, S.; OMullane, M.

2004-01-01

Plasma volume recombination in the divertor, a process in which charged particles recombine to neutral atoms, contributes to plasma detachment and hence cooling at the divertor target region. Detachment has been observed at JET and other tokamaks and is known to occur at low electron temperatures (T(sub e)<1 eV) and at high electron density (n(sub e)>10(exp 20)/m(exp 3)). The ability to measure such low temperatures is therefore of interest for modelling the divertor. In present work we report development of a new spectroscopic technique for investigation of local electron density (n(sub e)) and temperature (T,) in the outer divertor at JET.

An analytic formula for the relativistic incoherent Thomson backscattering spectrum for a drifting bi-Maxwellian plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naito, O.

2015-08-15

An analytic formula has been derived for the relativistic incoherent Thomson backscattering spectrum for a drifting anisotropic plasma when the scattering vector is parallel to the drifting direction. The shape of the scattering spectrum is insensitive to the electron temperature perpendicular to the scattering vector, but its amplitude may be modulated. As a result, while the measured temperature correctly represents the electron distribution parallel to the scattering vector, the electron density may be underestimated when the perpendicular temperature is higher than the parallel temperature. Since the scattering spectrum in shorter wavelengths is greatly enhanced by the existence of drift, themore » diagnostics might be used to measure local electron current density in fusion plasmas.« less

High-temperature microphone system. [for measuring pressure fluctuations in gases at high temperature

NASA Technical Reports Server (NTRS)

Zuckerwar, A. J. (Inventor)

1979-01-01

Pressure fluctuations in air or other gases in an area of elevated temperature are measured using a condenser microphone located in the area of elevated temperature and electronics for processing changes in the microphone capacitance located outside the area the area and connected to the microphone by means of high-temperature cable assembly. The microphone includes apparatus for decreasing the undesirable change in microphone sensitivity at high temperatures. The high temperature cable assembly operates as a half-wavelength transmission line in an AM carrier system and maintains a large temperature gradient between the two ends of the cable assembly. The processing electronics utilizes a voltage controlled oscillator for automatic tuning thereby increasing the sensitivity of the measuring apparatus.

Comparison of the ultrafast hot electron dynamics of titanium nitride and gold for plasmonic applications

NASA Astrophysics Data System (ADS)

Doiron, Brock; Li, Yi; Mihai, Andrei P.; Cohen, Lesley F.; Petrov, Peter K.; Alford, Neil M.; Oulton, Rupert F.; Maier, Stefan A.

2017-08-01

With similar optical properties to gold and high thermal stability, titanium nitride continues to prove itself as a promising plasmonic material for high-temperature applications in the visible and near-infrared. In this work, we use transient pump probe differential reflection measurements to compare the electron energy decay channels in titanium nitride and gold thin films. Using an extended two temperature model to incorporate the photoexcited electrons, it is possible to separate the electron-electron and electron-phonon scattering contributions immediately following the arrival of the pump pulse. This model allows for incredibly accurate determination of the internal electronic properties using only optical measurements. As the electronic properties are key in hot electron applications, we show that titanium nitide has substantially longer electron thermalization and electron-phonon scattering times. With this, we were also able to resolve electron thermal conduction in the film using purely optical measurements.

Temperature Measurement by a Nanoscale Electron Probe Using Energy Gain and Loss Spectroscopy

NASA Astrophysics Data System (ADS)

Idrobo, Juan Carlos; Lupini, Andrew R.; Feng, Tianli; Unocic, Raymond R.; Walden, Franklin S.; Gardiner, Daniel S.; Lovejoy, Tracy C.; Dellby, Niklas; Pantelides, Sokrates T.; Krivanek, Ondrej L.

2018-03-01

Heat dissipation in integrated nanoscale devices is a major issue that requires the development of nanoscale temperature probes. Here, we report the implementation of a method that combines electron energy gain and loss spectroscopy to provide a direct measurement of the local temperature in the nanoenvironment. Loss and gain peaks corresponding to an optical-phonon mode in boron nitride were measured from room temperature to ˜1600 K . Both loss and gain peaks exhibit a shift towards lower energies as the sample is heated up. First-principles calculations of the temperature-induced phonon frequency shifts provide insights into the origin of this effect and confirm the experimental data. The experiments and theory presented here open the doors to the study of anharmonic effects in materials by directly probing phonons in the electron microscope.

Thomson-scattering measurements in the collective and noncollective regimes in laser produced plasmas (invited).

PubMed

Ross, J S; Glenzer, S H; Palastro, J P; Pollock, B B; Price, D; Tynan, G R; Froula, D H

2010-10-01

We present simultaneous Thomson-scattering measurements of light scattered from ion-acoustic and electron-plasma fluctuations in a N(2) gas jet plasma. By varying the plasma density from 1.5×10(18) to 4.0×10(19) cm(-3) and the temperature from 100 to 600 eV, we observe the transition from the collective regime to the noncollective regime in the high-frequency Thomson-scattering spectrum. These measurements allow an accurate local measurement of fundamental plasma parameters: electron temperature, density, and ion temperature. Furthermore, experiments performed in the high densities typically found in laser produced plasmas result in scattering from electrons moving near the phase velocity of the relativistic plasma waves. Therefore, it is shown that even at low temperatures relativistic corrections to the scattered power must be included.

Measurement of Debye length in laser-produced plasma.

NASA Technical Reports Server (NTRS)

Ehler, W.

1973-01-01

The Debye length of an expanded plasma created by placing an evacuated chamber with an entrance slit in the path of a freely expanding laser produced plasma was measured, using the slab geometry. An independent measurement of electron density together with the observed value for the Debye length also provided a means for evaluating the plasma electron temperature. This temperature has applications in ascertaining plasma conductivity and magnetic field necessary for confinement of the laser produced plasma. Also, the temperature obtained would be useful in analyzing electron-ion recombination rates in the expanded plasma and the dynamics of the cooling process of the plasma expansion.

Analysis method for Thomson scattering diagnostics in GAMMA 10/PDX.

PubMed

Ohta, K; Yoshikawa, M; Yasuhara, R; Chikatsu, M; Shima, Y; Kohagura, J; Sakamoto, M; Nakasima, Y; Imai, T; Ichimura, M; Yamada, I; Funaba, H; Minami, T

2016-11-01

We have developed an analysis method to improve the accuracies of electron temperature measurement by employing a fitting technique for the raw Thomson scattering (TS) signals. Least square fitting of the raw TS signals enabled reduction of the error in the electron temperature measurement. We applied the analysis method to a multi-pass (MP) TS system. Because the interval between the MPTS signals is very short, it is difficult to separately analyze each Thomson scattering signal intensity by using the raw signals. We used the fitting method to obtain the original TS scattering signals from the measured raw MPTS signals to obtain the electron temperatures in each pass.

Effective temperature of an ultracold electron source based on near-threshold photoionization.

PubMed

Engelen, W J; Smakman, E P; Bakker, D J; Luiten, O J; Vredenbregt, E J D

2014-01-01

We present a detailed description of measurements of the effective temperature of a pulsed electron source, based on near-threshold photoionization of laser-cooled atoms. The temperature is determined by electron beam waist scans, source size measurements with ion beams, and analysis with an accurate beam line model. Experimental data is presented for the source temperature as a function of the wavelength of the photoionization laser, for both nanosecond and femtosecond ionization pulses. For the nanosecond laser, temperatures as low as 14 ± 3 K were found; for femtosecond photoionization, 30 ± 5 K is possible. With a typical source size of 25 μm, this results in electron bunches with a relative transverse coherence length in the 10⁻⁴ range and an emittance of a few nm rad. © 2013 Elsevier B.V. All rights reserved.

Resolving an anomaly in electron temperature measurement using double and triple Langmuir probes

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Barada, K. K.; Chattopadhyay, P. K.; Ghosh, J.; Bora, D.

2015-02-01

Langmuir probes with variants such as single, double and triple probes remain the most common method of electron temperature measurement in low-temperature laboratory plasmas. However, proper estimation of electron temperature mainly using triple probe configuration requires the proper choice of compensation factor (W). Determination of the compensating factor is not very straightforward as it depends heavily on plasma floating potential (Vf), electron temperature (Te), the type of gas used for plasma production and the bias voltage applied to probe pins, especially in cases where there are substantial variations in floating potential. In this paper we highlight the anomaly in electron temperature measurement using double and triple Langmuir probe techniques as well as the proper determination of the compensation factor (W) to overcome this anomaly. Experiments are carried out with helicon antenna producing inductive radiofrequency plasmas, where significant variation of floating potential along the axis enables a detailed study of deviations introduced in Te measurements using triple probes compared to double and single probes. It is observed that the bias voltage between the probe pins of the triple probes plays an important role in the accurate determination of the compensating factor (W) and should be in the range (5Vd2 < Vd3 < 10Vd2), where Vd2 and Vd3 are the voltage between floating probe pins 2 and 1 and the bias voltage, respectively.

Multipurpose setup for low-temperature conversion electron Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Augustyns, V.; Trekels, M.; Gunnlaugsson, H. P.; Masenda, H.; Temst, K.; Vantomme, A.; Pereira, L. M. C.

2017-05-01

We describe an experimental setup for conversion electron Mössbauer spectroscopy (CEMS) at low temperature. The setup is composed of a continuous flow cryostat (temperature range of 4.2-500 K), detector housing, three channel electron multipliers, and corresponding electronics. We demonstrate the capabilities of the setup with CEMS measurements performed on a sample consisting of a thin enriched 57Fe film, with a thickness of 20 nm, deposited on a silicon substrate. We also describe exchangeable adaptations (lid and sample holder) which extend the applicability of the setup to emission Mössbauer spectroscopy as well as measurements under an applied magnetic field.

Temperature Dependent Electron Transport Properties of Gold Nanoparticles and Composites: Scanning Tunneling Spectroscopy Investigations.

PubMed

Patil, Sumati; Datar, Suwarna; Dharmadhikari, C V

2018-03-01

Scanning tunneling spectroscopy (STS) is used for investigating variations in electronic properties of gold nanoparticles (AuNPs) and its composite with urethane-methacrylate comb polymer (UMCP) as function of temperature. Films are prepared by drop casting AuNPs and UMCP in desired manner on silicon substrates. Samples are further analyzed for morphology under scanning electron microscopy (SEM) and atomic force microscopy (AFM). STS measurements performed in temperature range of 33 °C to 142 °C show systematic variation in current versus voltage (I-V) curves, exhibiting semiconducting to metallic transition/Schottky behavior for different samples, depending upon preparation method and as function of temperature. During current versus time (I-t) measurement for AuNPs, random telegraphic noise is observed at room temperature. Random switching of tunneling current between two discrete levels is observed for this sample. Power spectra derived from I-t show 1/f2 dependence. Statistical analysis of fluctuations shows exponential behavior with time width τ ≈ 7 ms. Local density of states (LDOS) plots derived from I-V curves of each sample show systematic shift in valance/conduction band edge towards/away from Fermi level, with respect to increase in temperature. Schottky emission is best fitted electron emission mechanism for all samples over certain range of bias voltage. Schottky plots are used to calculate barrier heights and temperature dependent measurements helped in measuring activation energies for electron transport in all samples.

Self-correcting electronically scanned pressure sensor

NASA Technical Reports Server (NTRS)

Gross, C. (Inventor)

1983-01-01

A multiple channel high data rate pressure sensing device is disclosed for use in wind tunnels, spacecraft, airborne, process control, automotive, etc., pressure measurements. Data rates in excess of 100,000 measurements per second are offered with inaccuracies from temperature shifts less than 0.25% (nominal) of full scale over a temperature span of 55 C. The device consists of thirty-two solid state sensors, signal multiplexing electronics to electronically address each sensor, and digital electronic circuitry to automatically correct the inherent thermal shift errors of the pressure sensors and their associated electronics.

Electron heated target temperature measurements in petawatt laser experiments based on extreme ultraviolet imaging and spectroscopy.

PubMed

Ma, T; Beg, F N; MacPhee, A G; Chung, H-K; Key, M H; Mackinnon, A J; Patel, P K; Hatchett, S; Akli, K U; Stephens, R B; Chen, C D; Freeman, R R; Link, A; Offermann, D T; Ovchinnikov, V; Van Woerkom, L D

2008-10-01

Three independent methods (extreme ultraviolet spectroscopy, imaging at 68 and 256 eV) have been used to measure planar target rear surface plasma temperature due to heating by hot electrons. The hot electrons are produced by ultraintense laser-plasma interactions using the 150 J, 0.5 ps Titan laser. Soft x-ray spectroscopy in the 50-400 eV region and imaging at the 68 and 256 eV photon energies give a planar deuterated carbon target rear surface pre-expansion temperature in the 125-150 eV range, with the rear plasma plume averaging a temperature approximately 74 eV.

Experiments on Quantum Hall Topological Phases in Ultra Low Temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Rui-Rui

2015-02-14

This project is to cool electrons in semiconductors to extremely low temperatures and to study new states of matter formed by low-dimensional electrons (or holes). At such low temperatures (and with an intense magnetic field), electronic behavior differs completely from ordinary ones observed at room temperatures or regular low temperature. Studies of electrons at such low temperatures would open the door for fundamental discoveries in condensed matter physics. Present studies have been focused on topological phases in the fractional quantum Hall effect in GaAs/AlGaAs semiconductor heterostructures, and the newly discovered (by this group) quantum spin Hall effect in InAs/GaSb materials.more » This project consists of the following components: 1) Development of efficient sample cooling techniques and electron thermometry: Our goal is to reach 1 mK electron temperature and reasonable determination of electron temperature; 2) Experiments at ultra-low temperatures: Our goal is to understand the energy scale of competing quantum phases, by measuring the temperature-dependence of transport features. Focus will be placed on such issues as the energy gap of the 5/2 state, and those of 12/5 (and possible 13/5); resistive signature of instability near 1/2 at ultra-low temperatures; 3) Measurement of the 5/2 gaps in the limit of small or large Zeeman energies: Our goal is to gain physics insight of 5/2 state at limiting experimental parameters, especially those properties concerning the spin polarization; 4) Experiments on tuning the electron-electron interaction in a screened quantum Hall system: Our goal is to gain understanding of the formation of paired fractional quantum Hall state as the interaction pseudo-potential is being modified by a nearby screening electron layer; 5) Experiments on the quantized helical edge states under a strong magnetic field and ultralow temperatures: our goal is to investigate both the bulk and edge states in a quantum spin Hall insulator under time-reversal symmetry-broken conditions.« less

Observation of warm, higher energy electrons transiting a double layer in a helicon plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sung, Yung-Ta, E-mail: ysung2@wisc.edu; Li, Yan; Scharer, John E.

2015-03-15

Measurements of an inductive RF helicon argon plasma double layer with two temperature electron distributions including a fast (>80 eV) tail are observed at 0.17 mTorr Ar pressure. The fast, untrapped electrons observed downstream of the double layer have a higher temperature (13 eV) than the trapped (T{sub e} = 4 eV) electrons. The reduction of plasma potential and density observed in the double layer region would require an upstream temperature ten times the measured 4 eV if occurring via Boltzmann ambipolar expansion. The experimental observation in Madison helicon experiment indicates that fast electrons with substantial density fractions can be created at low helicon operating pressures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reusch, L. M., E-mail: lmmcguire@wisc.edu; Den Hartog, D. J.; Goetz, J.

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 frommore » experiments indicates that this discrepancy is due to physics missing from the SXR{sub DF} analysis rather than instrumentation effects.« less

Diagnosing pure-electron plasmas with internal particle flux probes.

PubMed

Kremer, J P; Pedersen, T Sunn; Marksteiner, Q; Lefrancois, R G; Hahn, M

2007-01-01

Techniques for measuring local plasma potential, density, and temperature of pure-electron plasmas using emissive and Langmuir probes are described. The plasma potential is measured as the least negative potential at which a hot tungsten filament emits electrons. Temperature is measured, as is commonly done in quasineutral plasmas, through the interpretation of a Langmuir probe current-voltage characteristic. Due to the lack of ion-saturation current, the density must also be measured through the interpretation of this characteristic thereby greatly complicating the measurement. Measurements are further complicated by low densities, low cross field transport rates, and large flows typical of pure-electron plasmas. This article describes the use of these techniques on pure-electron plasmas in the Columbia Non-neutral Torus (CNT) stellarator. Measured values for present baseline experimental parameters in CNT are phi(p)=-200+/-2 V, T(e)=4+/-1 eV, and n(e) on the order of 10(12) m(-3) in the interior.

Electron temperature and density measurement of tungsten inert gas arcs with Ar-He shielding gas mixture

NASA Astrophysics Data System (ADS)

Kühn-Kauffeldt, M.; Marques, J.-L.; Forster, G.; Schein, J.

2013-10-01

The diagnostics of atmospheric welding plasma is a well-established technology. In most cases the measurements are limited to processes using pure shielding gas. However in many applications shielding gas is a mixture of various components including metal vapor in gas metal arc welding (GMAW). Shielding gas mixtures are intentionally used for tungsten inert gas (TIG) welding in order to improve the welding performance. For example adding Helium to Argon shielding gas allows the weld geometry and porosity to be influenced. Yet thermal plasmas produced with gas mixtures or metal vapor still require further experimental investigation. In this work coherent Thomson scattering is used to measure electron temperature and density in these plasmas, since this technique allows independent measurements of electron and ion temperature. Here thermal plasmas generated by a TIG process with 50% Argon and 50% Helium shielding gas mixture have been investigated. Electron temperature and density measured by coherent Thomson scattering have been compared to the results of spectroscopic measurements of the plasma density using Stark broadening of the 696.5 nm Argon spectral line. Further investigations of MIG processes using Thomson scattering technique are planned.

Profile measurements of the electron temperature on the ASDEX Upgrade, COMPASS, and ISTTOK tokamak using Thomson scattering, triple, and ball-pen probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamek, J., E-mail: adamek@ipp.cas.cz; Horacek, J.; Bilkova, P.

The ball-pen probe (BPP) technique is used successfully to make profile measurements of the electron temperature on the ASDEX Upgrade (Axially Symmetric Divertor Experiment), COMPASS (COMPact ASSembly), and ISTTOK (Instituto Superior Tecnico TOKamak) tokamak. The electron temperature is provided by a combination of the BPP potential (Φ{sub BPP}) and the floating potential (V{sub fl}) of the Langmuir probe (LP), which is compared with the Thomson scattering diagnostic on ASDEX Upgrade and COMPASS. Excellent agreement between the two diagnostics is obtained for circular and diverted plasmas and different heating mechanisms (Ohmic, NBI, ECRH) in deuterium discharges with the same formula T{submore » e} = (Φ{sub BPP} − V{sub fl})/2.2. The comparative measurements of the electron temperature using BPP/LP and triple probe (TP) techniques on the ISTTOK tokamak show good agreement of averaged values only inside the separatrix. It was also found that the TP provides the electron temperature with significantly higher standard deviation than BPP/LP. However, the resulting values of both techniques are well in the phase with the maximum of cross-correlation function being 0.8.« less

Large-scale variation of electron parameters from Quasi-Thermal Noise during WIND perigees in the Earth's magnetosphere

NASA Astrophysics Data System (ADS)

Issautier, Karine; Ongala-Edoumou, Samuel; Moncuquet, Michel

2016-04-01

The quasi-thermal noise (QTN) method consists in measuring the electrostatic fluctuations produced by the thermal motion of the ambient particles. This noise is detected with a sensitive wave receiver and measured at the terminal of a passive electric antenna, which is immersed in a stable plasma. The analysis of the so-called QTN provides in situ measurements, mainly the total electron density, with a good accuracy, and thermal temperature in a large number of space media. We create a preliminary electron database to analyse the anti-correlation between electron density and temperature deduced from WIND perigees in the Earth's plasmasphere. We analyse the radio power spectra measured by the Thermal Noise Receiver (TNR), using the 100-m long dipole antenna, onboard WIND spacecraft. We develop a systematic routine to determine the electron density, core and halo temperature and the magnitude of the magnetic field based on QTN in Bernstein modes. Indeed, the spectra are weakly banded between gyroharmonics below the upper hybrid frequency, from which we derive the local electron density. From the gyrofrequency determination, we obtain an independent measure of the magnetic field magnitude, which is in close agreement with the onboard magnetometer.

First results of electron temperature measurements by the use of multi-pass Thomson scattering system in GAMMA 10

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshikawa, M., E-mail: yosikawa@prc.tsukuba.ac.jp; Nagasu, K.; Shimamura, Y.

2014-11-15

A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system.

First results of electron temperature measurements by the use of multi-pass Thomson scattering system in GAMMA 10.

PubMed

Yoshikawa, M; Yasuhara, R; Nagasu, K; Shimamura, Y; Shima, Y; Kohagura, J; Sakamoto, M; Nakashima, Y; Imai, T; Ichimura, M; Yamada, I; Funaba, H; Kawahata, K; Minami, T

2014-11-01

A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system.

Magnetic and thermoelectric properties of electron doped Ca0.85Pr0.15MnO3

NASA Astrophysics Data System (ADS)

Hossain Khan, Momin; Pal, Sudipta; Bose, Esa

2015-10-01

We have investigated temperature-dependent magnetization (M), magnetic susceptibility (χ) and thermoelectric (S) properties of the electron-doped Ca0.85Pr0.15MnO3. With decrease of temperature, paramagnetic (PM) to antiferromagnetic (AFM) phase transition occurs with a well-defined Néel temperature (TN=122 K). Magnetic susceptibility measurements reveal that the paramagnetic state involves modified Curie-Weiss paramagnetism. Field cooled and zero field cooled magnetization measurements indicate a signature of magnetic frustration. Ferromagnetic (FM) double-exchange interactions associated with doped eg electrons are favored over competing AFM interactions below Tirr=112 K. Magnetization data also shows a second-order phase transition. The sign reversal in S(T) has been interpreted in terms of the change in the electronic structure relating to the orbital degrees of freedom of the doped eg electron. Low temperature (5-140 K) thermoelectric power, S (T) signifies the importance of electron-magnon scattering process.

Non-equilibrium thermionic electron emission for metals at high temperatures

NASA Astrophysics Data System (ADS)

Domenech-Garret, J. L.; Tierno, S. P.; Conde, L.

2015-08-01

Stationary thermionic electron emission currents from heated metals are compared against an analytical expression derived using a non-equilibrium quantum kappa energy distribution for the electrons. The latter depends on the temperature decreasing parameter κ ( T ) , which decreases with increasing temperature and can be estimated from raw experimental data and characterizes the departure of the electron energy spectrum from equilibrium Fermi-Dirac statistics. The calculations accurately predict the measured thermionic emission currents for both high and moderate temperature ranges. The Richardson-Dushman law governs electron emission for large values of kappa or equivalently, moderate metal temperatures. The high energy tail in the electron energy distribution function that develops at higher temperatures or lower kappa values increases the emission currents well over the predictions of the classical expression. This also permits the quantitative estimation of the departure of the metal electrons from the equilibrium Fermi-Dirac statistics.

Measurement of the hot spot electron temperature in NIF ICF implosions using Krypton x-ray emission spectroscopy

NASA Astrophysics Data System (ADS)

Ma, T.; Chen, H.; Patel, P. K.; Schneider, M.; Barrios, M.; Berzak Hopkins, L.; Casey, D.; Chung, H.-K.; Hammel, B.; Jarrott, C.; Nora, R.; Pak, A.; Scott, H.; Spears, B.; Weber, C.

2015-11-01

The inference of ion temperature from neutron spectral measurements in indirect-drive ICF implosions is known to be sensitive to non-thermal velocity distributions in the fuel. The electron temperature (Te) inferred from dopant line ratios should not be sensitive to these bulk motions and hence may be a better measure of the thermal temperature of the hot spot. Here we describe a series of experiments to be conducted on the NIF where a small concentration of a mid-Z dopant (Krypton) is added to the fuel gas. The x-ray spectra is measured and the electron temperature is inferred from Kr line ratios. We also quantify the level of radiative cooling in the hot spot due to this mid-Z dopant. These experiments represent the first direct measurement of hot spot Te using spectroscopy, and we will describe the considerations for applying x-ray spectroscopy in such dense and non-uniform hot spots. This work performed under the auspices of U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Freethy, S. J.; Görler, T.; Creely, A. J.; Conway, G. D.; Denk, S. S.; Happel, T.; Koenen, C.; Hennequin, P.; White, A. E.; ASDEX Upgrade Team

2018-05-01

Measurements of turbulent electron temperature fluctuation amplitudes, δTe ⊥/Te , frequency spectra, and radial correlation lengths, Lr(Te ⊥) , have been performed at ASDEX Upgrade using a newly upgraded Correlation ECE diagnostic in the range of scales k⊥<1.4 cm-1, kr<3.5 cm-1 ( k⊥ρs<0.28 and krρs<0.7 ). The phase angle between turbulent temperature and density fluctuations, αnT, has also been measured by using an ECE radiometer coupled to a reflectometer along the same line of sight. These quantities are used simultaneously to constrain a set of ion-scale non-linear gyrokinetic turbulence simulations of the outer core (ρtor = 0.75) of a low density, electron heated L-mode plasma, performed using the gyrokinetic simulation code, GENE. The ion and electron temperature gradients were scanned within uncertainties. It is found that gyrokinetic simulations are able to match simultaneously the electron and ion heat flux at this radius within the experimental uncertainties. The simulations were performed based on a reference discharge for which δTe ⊥/Te measurements were available, and Lr(Te ⊥) and αnT were then predicted using synthetic diagnostics prior to measurements in a repeat discharge. While temperature fluctuation amplitudes are overestimated by >50% for all simulations within the sensitivity scans performed, good quantitative agreement is found for Lr(Te ⊥) and αnT. A validation metric is used to quantify the level of agreement of individual simulations with experimental measurements, and the best agreement is found close to the experimental gradient values.

Kinetic Temperature and Electron Density Measurement in an Inductively Coupled Plasma Torch using Degenerate Four-Wave Mixing

NASA Technical Reports Server (NTRS)

Schafer, Julia; Lyons, Wendy; Tong, WIlliam G.; Danehy, Paul M.

2008-01-01

Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively-coupled plasma. Measurements are performed in a 1 kW, 27 MHz RF plasma using a continuous-wave, tunable 811.5-nm diode laser to excite the 4s(sup 3)P2 approaches 4p(sup 3)D3 argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler-broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000 K+/-150 K. Electron densities measured range from 6.1 (+/-0.3) x 10(exp 15)/cu cm to 10.1 (+/-0.3) x 10(exp 15)/cu cm. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.

A method for atomic-level noncontact thermometry with electron energy distribution

NASA Astrophysics Data System (ADS)

Kinoshita, Ikuo; Tsukada, Chiharu; Ouchi, Kohei; Kobayashi, Eiichi; Ishii, Juntaro

2017-04-01

We devised a new method of determining the temperatures of materials with their electron-energy distributions. The Fermi-Dirac distribution convoluted with a linear combination of Gaussian and Lorentzian distributions was fitted to the photoelectron spectrum measured for the Au(110) single-crystal surface at liquid N2-cooled temperature. The fitting successfully determined the surface-local thermodynamic temperature and the energy resolution simultaneously from the photoelectron spectrum, without any preliminary results of other measurements. The determined thermodynamic temperature was 99 ± 2.1 K, which was in good agreement with the reference temperature of 98.5 ± 0.5 K measured using a silicon diode sensor attached to the sample holder.

Determining coronal electron temperatures from observations with UVCS/SOHO

NASA Technical Reports Server (NTRS)

Fineschi, S.; Esser, R.; Habbal, S. R.; Karovska, M.; Romoli, M.; Strachan, L.; Kohl, J. L.; Huber, M. C. E.

1995-01-01

The electron temperature is a fundamental physical parameter of the coronal plasma. Currently, there are no direct measurements of this quantity in the extended corona. Observations with the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the upcoming Solar and Heliospheric Observatory (SOHO) mission can provide the most direct determination of the electron kinetic temperature (or, more precisely, the electron velocity distribution along the line of sight). This measurement is based on the observation of the Thomson-scattered Lyman alpha (Ly-alpha) profile. This observation is made particularly challenging by the fact that the integrated intensity of the electron-scattered Ly-alpha line is about 10(exp 3) times fainter than that of the resonantly-scattered Ly-alpha component. In addition, the former is distributed across 50 A (FWHM), unlike the latter that is concentrated in 1 A. These facts impose stringent requirements on the stray-light rejection properties of the coronagraph/spectrometer, and in particular on the requirements for the grating. We make use of laboratory measurements of the UVCS Ly-alpha grating stray-light, and of simulated electron-scattered Ly-alpha profiles to estimate the expected confidence levels of electron temperature determination. Models of different structures typical of the corona (e.g., streamers, coronal holes) are used for this parameter study.

Temperature measurement in intensive care patients: comparison of urinary bladder, oesophageal, rectal, axillary, and inguinal methods versus pulmonary artery core method.

PubMed

Lefrant, J-Y; Muller, L; de La Coussaye, J Emmanuel; Benbabaali, M; Lebris, C; Zeitoun, N; Mari, C; Saïssi, G; Ripart, J; Eledjam, J-J

2003-03-01

Comparisons of urinary bladder, oesophageal, rectal, axillary, and inguinal temperatures versus pulmonary artery temperature. Prospective cohort study. Intensive Care Unit of a University-Hospital. Forty-two intensive care patients requiring a pulmonary artery catheter (PAC). Patients requiring PAC and without oesophageal, urinary bladder, and/or rectal disease or recent surgery were included in the study. Temperature was simultaneously monitored with PAC, urinary, oesophageal, and rectal electronic thermometers and with axillary and inguinal gallium-in-glass thermometers. Comparisons used a Bland and Altman method. The pulmonary arterial temperature ranged from 33.7 degrees C to 40.2 degrees C. Urinary bladder temperature was assessed in the last 22 patients. A total of 529 temperature measurement comparisons were carried out (252 comparisons of esophageal, rectal, inguinal, axillary, and pulmonary artery temperature measurements in the first 20 patients, and 277 comparisons with overall methods in the last patients). Nine to 18 temperature measurement comparisons were carried out per patient (median = 13). The mean differences between pulmonary artery temperatures and those of the different methods studied were: oesophageal (0.11+/-0.30 degrees C), rectal (-0.07+/-0.40 degrees C), axillary (0.27+/-0.45 degrees C), inguinal (0.17+/-0.48 degrees C), urinary bladder (-0.21+/-0.20 degrees C). In critically ill patients, urinary bladder and oesophageal electronic thermometers are more reliable than the electronic rectal thermometer which is better than inguinal and axillary gallium-in-glass thermometers to measure core temperature.

An electronic system for measuring thermophysical properties of wind tunnel models

NASA Technical Reports Server (NTRS)

Corwin, R. R.; Kramer, J. S.

1975-01-01

An electronic system is described which measures the surface temperature of a small portion of the surface of the model or sample at high speeds using an infrared radiometer. This data is processed along with heating rate data from the reference heat gauge in a small computer and prints out the desired thermophysical properties, time, surface temperature, and reference heat rate. This system allows fast and accurate property measurements over thirty temperature increments. The technique, the details of the apparatus, the procedure for making these measurements, and the results of some preliminary tests are presented.

Time-of-Flight Measurements on TlBr Detectors

NASA Astrophysics Data System (ADS)

Suzuki, K.; Shorohov, M.; Sawada, T.; Seto, S.

2015-04-01

Carrier transport properties of TlBr crystals grown using the Bridgman method were investigated by the time-of-flight technique. The electron and hole mobilities were measured as 20 - 27 cm2 /Vs and 1.0 - 2.0 cm2/Vs respectively at room temperature. The temperature dependence of the electron mobility increases with decreasing temperature as approximated by a well-known empirical formula reflecting the reciprocal of the LO-phonon density.

Measurements of Electron Impact Excitation Cross Sections at the Harvard-Smithsonian Center for Astrophysics

NASA Technical Reports Server (NTRS)

Gardner, L. D.; Kohl, J. L.

2006-01-01

The analysis of absolute spectral line intensities and intensity ratios with spectroscopic diagnostic techniques provides empirical determinations of chemical abundances, electron densities and temperatures in astrophysical objects. Since spectral line intensities and their ratios are controlled by the excitation rate coefficients for the electron temperature of the observed astrophysical structure, it is imperative that one have accurate values for the relevant rate coefficients. Here at the Harvard-Smithsonian Center for Astrophysics, we have been carrying out measurements of electron impact excitation (EIE) for more than 25 years.

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

PubMed

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

2017-07-25

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

Plasma diagnosis as a tool for the determination of the parameters of electron beam evaporation and sources of ionization

NASA Astrophysics Data System (ADS)

Mukherjee, Jaya; Dileep Kumar, V.; Yadav, S. P.; Barnwal, Tripti A.; Dikshit, Biswaranjan

2016-07-01

The atomic vapor generated by electron beam heating is partially ionized due to atom-atom collisions (Saha ionization) and electron impact ionization, which depend upon the source temperature and area of evaporation as compared to the area of electron beam bombardment on the target. When electron beam evaporation is carried out by inserting the target inside an insulating liner to reduce conductive heat loss, it is expected that the area of evaporation becomes significantly more than the area of electron beam bombardment on the target, resulting in reduced electron impact ionization. To assess this effect and to quantify the parameters of evaporation, such as temperature and area of evaporation, we have carried out experiments using zirconium, tin and aluminum as a target. By measuring the ion content using a Langmuir probe, in addition to measuring the atomic vapor flux at a specific height, and by combining the experimental data with theoretical expressions, we have established a method for simultaneously inferring the source temperature, evaporation area and ion fraction. This assumes significance because the temperature cannot be reliably measured by an optical pyrometer due to the wavelength dependent source emissivity and reflectivity of thin film mirrors. In addition, it also cannot be inferred from only the atomic flux data at a certain height as the area of evaporation is unknown (it can be much more than the area of electron bombardment, especially when the target is placed in a liner). Finally, the reason for the lower observed electron temperatures of the plasma for all the three cases is found to be the energy loss due to electron impact excitation of the atomic vapor during its expansion from the source.

Measurement of electron-ion relaxation in warm dense copper

DOE PAGES

Cho, B. I.; Ogitsu, T.; Engelhorn, K.; ...

2016-01-06

Experimental investigation of electron-ion coupling and electron heat capacity of copper in warm and dense states are presented. From time-resolved x-ray absorption spectroscopy, the temporal evolution of electron temperature is obtained for non-equilibrium warm dense copper heated by an intense femtosecond laser pulse. Electron heat capacity and electron-ion coupling are inferred from the initial electron temperature and its decrease over 10 ps. As a result, data are compared with various theoretical models.

Soft x-ray continuum radiation transmitted through metallic filters: an analytical approach to fast electron temperature measurements.

PubMed

Delgado-Aparicio, L; Tritz, K; Kramer, T; Stutman, D; Finkenthal, M; Hill, K; Bitter, M

2010-10-01

A new set of analytic formulas describes the transmission of soft x-ray continuum radiation through a metallic foil for its application to fast electron temperature measurements in fusion plasmas. This novel approach shows good agreement with numerical calculations over a wide range of plasma temperatures in contrast with the solutions obtained when using a transmission approximated by a single-Heaviside function [S. von Goeler et al., Rev. Sci. Instrum. 70, 599 (1999)]. The new analytic formulas can improve the interpretation of the experimental results and thus contribute in obtaining fast temperature measurements in between intermittent Thomson scattering data.

A correlation electron cyclotron emission diagnostic and the importance of multifield fluctuation measurements for testing nonlinear gyrokinetic turbulence simulations.

PubMed

White, A E; Schmitz, L; Peebles, W A; Carter, T A; Rhodes, T L; Doyle, E J; Gourdain, P A; Hillesheim, J C; Wang, G; Holland, C; Tynan, G R; Austin, M E; McKee, G R; Shafer, M W; Burrell, K H; Candy, J; DeBoo, J C; Prater, R; Staebler, G M; Waltz, R E; Makowski, M A

2008-10-01

A correlation electron cyclotron emission (CECE) diagnostic has been used to measure local, turbulent fluctuations of the electron temperature in the core of DIII-D plasmas. This paper describes the hardware and testing of the CECE diagnostic and highlights the importance of measurements of multifield fluctuation profiles for the testing and validation of nonlinear gyrokinetic codes. The process of testing and validating such codes is critical for extrapolation to next-step fusion devices. For the first time, the radial profiles of electron temperature and density fluctuations are compared to nonlinear gyrokinetic simulations. The CECE diagnostic at DIII-D uses correlation radiometry to measure the rms amplitude and spectrum of the electron temperature fluctuations. Gaussian optics are used to produce a poloidal spot size with w(o) approximately 1.75 cm in the plasma. The intermediate frequency filters and the natural linewidth of the EC emission determine the radial resolution of the CECE diagnostic, which can be less than 1 cm. Wavenumbers resolved by the CECE diagnostic are k(theta) < or = 1.8 cm(-1) and k(r) < or = 4 cm(-1), relevant for studies of long-wavelength turbulence associated with the trapped electron mode and the ion temperature gradient mode. In neutral beam heated L-mode plasmas, core electron temperature fluctuations in the region 0.5 < r/a < 0.9, increase with radius from approximately 0.5% to approximately 2%, similar to density fluctuations that are measured simultaneously with beam emission spectroscopy. After incorporating "synthetic diagnostics" to effectively filter the code output, the simulations reproduce the characteristics of the turbulence and transport at one radial location r/a = 0.5, but not at a second location, r/a = 0.75. These results illustrate that measurements of the profiles of multiple fluctuating fields can provide a significant constraint on the turbulence models employed by the code.

DOE Office of Scientific and Technical Information (OSTI.GOV)

C. BARNES

Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either overdense, operating at high density relative to the magnetic field (e.g. {omega}{sub pe} >> {Omega}{sub ce} in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition ({tau} > 2). Electron Bernstein waves (EBWs) are electrostatic waves which can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers, as amore » result of their large K{sub i}. This talk reports on measurements of EBW emission on the CDX-U spherical torus, where B{sub 0} {approx} 2 kG, {approx} 10{sup 13} cm{sup -3} and T{sub e} {approx} 10 - 200 eV. Results will be presented for both direct detection of EBWs and for mode-converted EBW emission. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multi-point Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be {le} T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe was employed to measure changes in edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Changes in the mode conversion efficiency may explain the observation of mode-converted EBW radiation temperatures below T{sub e}. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where {omega}{sub pe} >> {Omega}{sub ce}.« less

Emission measures derived from far ultraviolet spectra of T Tauri stars

NASA Astrophysics Data System (ADS)

Cram, L. E.; Giampapa, M. S.; Imhoff, C. L.

1980-06-01

Spectroscopic diagnostics based on UV emission line observations have been developed to study the solar chromosphere, transition region, and corona. The atmospheric properties that can be inferred from observations of total line intensities include the temperature, by identifying the ionic species present; the temperature distribution of the emission measure, from the absolute intensities; and the electron density of the source, from line intensity ratios sensitive to the electron density. In the present paper, the temperature distribution of the emission measure is estimated from observations of far UV emission line fluxes of the T Tauri stars, RW Aurigae and RU Lupi, made on the IUE. A crude estimate of the electron density of one star is obtained, using density-sensitive line ratios.

Cold and warm electrons at comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Eriksson, A. I.; Engelhardt, I. A. D.; André, M.; Boström, R.; Edberg, N. J. T.; Johansson, F. L.; Odelstad, E.; Vigren, E.; Wahlund, J.-E.; Henri, P.; Lebreton, J.-P.; Miloch, W. J.; Paulsson, J. J. P.; Simon Wedlund, C.; Yang, L.; Karlsson, T.; Jarvinen, R.; Broiles, T.; Mandt, K.; Carr, C. M.; Galand, M.; Nilsson, H.; Norberg, C.

2017-09-01

Context. Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. Aims: Our aim is to demonstrate the existence of cold electrons in the inner coma of comet 67P/Churyumov-Gerasimenko and show filamentation of this plasma. Methods: In situ measurements of plasma density, electron temperature and spacecraft potential were carried out by the Rosetta Langmuir probe instrument, LAP. We also performed analytical modelling of the expanding two-temperature electron gas. Results: LAP data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5-10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order - 10 V. Conclusions: The warm (5-10 eV) electron population observed throughout the mission is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses.

Implantable, Ingestible Electronic Thermometer

NASA Technical Reports Server (NTRS)

Kleinberg, Leonard

1987-01-01

Small quartz-crystal-controlled oscillator swallowed or surgically implanted provides continuous monitoring of patient's internal temperature. Receiver placed near patient measures oscillator frequency, and temperature inferred from previously determined variation of frequency with temperature. Frequency of crystal-controlled oscillator varies with temperature. Circuit made very small and implanted or ingested to measure internal body temperature.

Temporal variations of electron density and temperature in Kr/Ne/H2 photoionized plasma induced by nanosecond pulses from extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-06-01

Spectral investigations of low-temperature photoionized plasmas created in a Kr/Ne/H2 gas mixture were performed. The low-temperature plasmas were generated by gas mixture irradiation using extreme ultraviolet pulses from a laser-plasma source. Emission spectra in the ultraviolet/visible range from the photoionized plasmas contained lines that mainly corresponded to neutral atoms and singly charged ions. Temporal variations in the plasma electron temperature and electron density were studied using different characteristic emission lines at various delay times. Results, based on Kr II lines, showed that the electron temperature decreased from 1.7 to 0.9 eV. The electron densities were estimated using different spectral lines at each delay time. In general, except for the Hβ line, in which the electron density decreased from 3.78 × 1016 cm-3 at 200 ns to 5.77 × 1015 cm-3 at 2000 ns, most of the electron density values measured from the different lines were of the order of 1015 cm-3 and decreased slightly while maintaining the same order when the delay time increased. The time dependences of the measured and simulated intensities of a spectral line of interest were also investigated. The validity of the partial or full local thermodynamic equilibrium (LTE) conditions in plasma was explained based on time-resolved electron density measurements. The partial LTE condition was satisfied for delay times in the 200 ns to 1500 ns range. The results are summarized, and the dominant basic atomic processes in the gas mixture photoionized plasma are discussed.

Investigation of ion and electron heat transport of high- T e ECH heated discharges in the large helical device

DOE PAGES

Pablant, N. A.; Satake, S.; Yokoyama, M.; ...

2016-01-28

An analysis of the radial electric field and heat transport, both for ions and electrons, is presented for a high-more » $${{T}_{\\text{e}}}$$ electron cyclotron heated (ECH) discharge on the large helical device (LHD). Transport analysis is done using the task3d transport suite utilizing experimentally measured profiles for both ions and electrons. Ion temperature and perpendicular flow profiles are measured using the recently installed x-ray imaging crystal spectrometer diagnostic (XICS), while electron temperature and density profiles are measured using Thomson scattering. The analysis also includes calculated ECH power deposition profiles as determined through the travis ray-tracing code. This is the first time on LHD that this type of integrated transport analysis with measured ion temperature profiles has been performed without NBI, allowing the heat transport properties of plasmas with only ECH heating to be more clearly examined. For this study, a plasma discharge is chosen which develops a high central electron temperature ($${{T}_{\\text{eo}}}=9$$ keV) at moderately low densities ($${{n}_{\\text{eo}}}=1.5\\times {{10}^{19}}$$ m-3). The experimentally determined transport properties from task3d are compared to neoclassical predictions as calculated by the gsrake and fortec-3d codes. The predicted electron fluxes are seen to be an order of magnitude less than the measured fluxes, indicating that electron transport is largely anomalous, while the neoclassical and measured ion heat fluxes are of the same magnitude. Neoclassical predictions of a strong positive ambipolar electric field ($${{E}_{\\text{r}}}$$ ) in the plasma core are validated through comparisons to perpendicular flow measurements from the XICS diagnostic. Furthermore, this provides confidence that the predictions are producing physically meaningful results for the particle fluxes and radial electric field, which are a key component in correctly predicting plasma confinement.« less

Effect of the magnetic field on measurements of the electron density and temperature by cylindrical probes in the Earth's ionosphere

NASA Astrophysics Data System (ADS)

Gubsky, V. F.

2009-12-01

In the 1960s and 1970s, quite simply produced cylindrical Langmuir probes were used in the USSR both on satellites (Kosmos-378, Intercosmos-2, -4, -8, -10, -19) and to measure the electron density and temperature on vertical launched rockets (Vertical’-4, -6, -10) within the Intercosmos program. These measurements were first made at middle latitudes. With increasing inclination of the orbits of launched satellites (satellites had no stabilization), falling sections were sometimes observed on probe characteristics in the electron saturation region. The Intercosmos-Bulgaria-1300 satellite, which was stabilized along three axes and was equipped with a cylindrical probe whose longitudinal axis was always directed downward to the Earth, was launched in 1981. This satellite allowed definite conclusions on the effect of the geomagnetic field on the form of the probe characteristic and, hence, on the determination of the electron density and temperature. Probe characteristics with falling sections are presented. These measurements are compared with those performed in a laboratory plasma. The appearance of negative sections on the probe characteristics is shown to be due to the effect of the geomagnetic field. The degree of this effect depends both on the electron density and temperature and on the probe voltage.

Investigations in the ionosphere by means of Kosmos 378. N(h) profiles and the temperature of the F region according to ground-based and satellite measurements above Khabarovsk

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mirmovich, E.G.; Shapiro, B.S.

1975-01-01

Simultaneous satellite measurements of electron density N/sub s/ and temperature (T/sub e/)/sub s/ at a height h/sub s/ above an observatory and ground-based observations are used to compute the total vertical electron density profiles N(h) and estimate the temperature of the ionospheric plasma. Four close time intervals after sunset were selected for analysis.

X-rays diagnostics of the hot electron energy distribution in the intense laser interaction with metal targets

NASA Astrophysics Data System (ADS)

Kostenko, O. F.; Andreev, N. E.; Rosmej, O. N.

2018-03-01

A two-temperature hot electron energy distribution has been revealed by modeling of bremsstrahlung emission, measured by the radiation attenuation and half-shade methods, and Kα emission from a massive silver cylinder irradiated by a subpicosecond s-polarized laser pulse with a peak intensity of about 2 × 1019 W/cm2. To deduce parameters of the hot electron spectrum, we have developed semi-analytical models of generation and measurements of the x-rays. The models are based on analytical expressions and tabulated data on electron stopping power as well as cross-sections of generation and absorption of the x-rays. The Kα emission from thin silver foils deposited on low-Z substrates, both conducting and nonconducting, has been used to verify the developed models and obtained hot electron spectrum. The obtained temperatures of the colder and hotter electron components are in agreement with the values predicted by kinetic simulations of the cone-guided approach to fast ignition [Chrisman et al., Phys. Plasmas 15, 056309 (2008)]. The temperature of the low-energy component of the accelerated electron spectrum is well below the ponderomotive scaling and Beg's law. We have obtained relatively low conversion efficiency of laser energy into the energy of hot electrons propagating through the solid target of about 2%. It is demonstrated that the assumption about a single-temperature hot electron energy distribution with the slope temperature described by the ponderomotive scaling relationship, without detailed analysis of the hot electron spectrum, can lead to strong overestimation of the laser-to-electron energy-conversion efficiency, in particular, the conversion efficiency of laser energy into the high-temperature component of the hot electron distribution.

Characterizing the temperature dependence of electronic packaging-material properties

NASA Astrophysics Data System (ADS)

Fu, Chia-Yu; Ume, Charles

1995-06-01

A computer-controlled, temperature-dependent material characterization system has been developed for thermal deformation analysis in electronic packaging applications, especially for printed wiring assembly warpage study. For fiberglass-reinforced epoxy (FR-4 type) material, the Young's moduli decrease to as low as 20-30% of the room-temperature values, while the shear moduli decrease to as low as 60-70% of the room-temperature values. The electrical resistance strain gage technique was used in this research. The test results produced overestimated values in property measurements, and this was shown in a case study. A noncontact strau]n measurement technique (laser extensometer) is now being used to measure these properties. Discrepancies of finite-element warpage predictions using different property values increase as the temperature increases from the stress-free temperature.

Variation of Derived Mesospheric Nitric Oxide in Relation to Wind and Temperature in Winter

NASA Technical Reports Server (NTRS)

Friedrich, M.; Torkar, K. M.

1984-01-01

As a good approximation, changes of the NO-density are solely responsible for changes of the non-auroral D-region. Under the assumption that other ion production processes are either known or negligible, one can derive (NO) from electron densities using a suitable effective electron loss rate. In the Winter Anomaly Campaign 1975/76 nineteen rocket payloads carried electron density measurements on fifteen days. On two of these days (NO) was measured in-situ by photometers. For these days one can establish the production not due to Lyman-alpha and NO. This rest production can then be applied to all (NO) derivations based on electron density measurements. In addition, in this campaign winds and temperatures were measured from the ground to approximately the base of the thermosphere. The derived field of NO densities between December 1975 and February 1976 from 70 to 100 km is compared to corresponding fields of winds (zonal and meridional), temperatures, pressure and Richardson numbers.

Viking electron temperature measurements - Evidence for a magnetic field in the Martian ionosphere

NASA Technical Reports Server (NTRS)

Hanson, W. B.; Mantas, G. P.

1988-01-01

Further analysis of the Viking RPA data has now provided measurements of the thermal electron temperature in the upper Martian ionosphere. It is found that Te is several thousand degrees K, i.e., only of the order of twice the ion temperature. The sum of all the measured partial plasma pressures, including ions and suprathermal electrons, has a minimum value of about 5 x 10 to the -10 dyn/sq cm near 350 km and is found to be insufficient to balance the measured electron pressure in the shocked solar wind near 1000 km altitude, by a factor of the order of 4. Thus there is no doubt that a magnetic field of at least 30 to 40 nT permeates the ionosphere. This conclusion is not inconsistent with previous assessments, but it now has a firm observational basis. These data do not uniquely establish whether the magnetic field is intrinsic or induced, but our assessment is that a significant intrinsic moment is not required.

Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak

NASA Astrophysics Data System (ADS)

Houshmandyar, S.; Hatch, D. R.; Horton, C. W.; Liao, K. T.; Phillips, P. E.; Rowan, W. L.; Zhao, B.; Cao, N. M.; Ernst, D. R.; Greenwald, M.; Howard, N. T.; Hubbard, A. E.; Hughes, J. W.; Rice, J. E.

2018-04-01

A profile for the critical gradient scale length (Lc) has been measured in L-mode discharges at the Alcator C-Mod tokamak, where electrons were heated by an ion cyclotron range of frequency through minority heating with the intention of simultaneously varying the heat flux and changing the local gradient. The electron temperature gradient scale length (LTe-1 = |∇Te|/Te) profile was measured via the BT-jog technique [Houshmandyar et al., Rev. Sci. Instrum. 87, 11E101 (2016)] and it was compared with electron heat flux from power balance (TRANSP) analysis. The Te profiles were found to be very stiff and already above the critical values, however, the stiffness was found to be reduced near the q = 3/2 surface. The measured Lc profile is in agreement with electron temperature gradient (ETG) models which predict the dependence of Lc-1 on local Zeff, Te/Ti, and the ratio of the magnetic shear to the safety factor. The results from linear Gene gyrokinetic simulations suggest ETG to be the dominant mode of turbulence in the electron scale (k⊥ρs > 1), and ion temperature gradient/trapped electron mode modes in the ion scale (k⊥ρs < 1). The measured Lc profile is in agreement with the profile of ETG critical gradients deduced from Gene simulations.

Tracking the ultrafast XUV optical properties of x-ray free-electron-laser heated matter with high-order harmonics

NASA Astrophysics Data System (ADS)

Williams, Gareth O.; Künzel, S.; Daboussi, S.; Iwan, B.; Gonzalez, A. I.; Boutu, W.; Hilbert, V.; Zastrau, U.; Lee, H. J.; Nagler, B.; Granados, E.; Galtier, E.; Heimann, P.; Barbrel, B.; Dovillaire, G.; Lee, R. W.; Dunn, J.; Recoules, V.; Blancard, C.; Renaudin, P.; de la Varga, A. G.; Velarde, P.; Audebert, P.; Merdji, H.; Zeitoun, Ph.; Fajardo, M.

2018-02-01

We present measurements of photon absorption by free electrons as a solid is transformed to plasma. A femtosecond x-ray free-electron laser is used to heat a solid, which separates the electron and ion heating time scales. The changes in absorption are measured with an independent probe pulse created through high-order-harmonic generation. We find an increase in electron temperature to have a relatively small impact on absorption, contrary to several predictions, whereas ion heating increases absorption. We compare the data to current theoretical and numerical approaches and find that a smoother electronic structure yields a better fit to the data, suggestive of a temperature-dependent electronic structure in warm dense matter.

Layout and results from the initial operation of the high-resolution x-ray imaging crystal spectrometer on the Large Helical Device.

PubMed

Pablant, N A; Bitter, M; Delgado-Aparicio, L; Goto, M; Hill, K W; Lazerson, S; Morita, S; Roquemore, A L; Gates, D; Monticello, D; Nielson, H; Reiman, A; Reinke, M; Rice, J E; Yamada, H

2012-08-01

First results of ion and electron temperature profile measurements from the x-ray imaging crystal spectrometer (XICS) diagnostic on the Large Helical Device (LHD) are presented. This diagnostic system has been operational since the beginning of the 2011 LHD experimental campaign and is the first application of the XICS diagnostic technique to helical plasma geometry. The XICS diagnostic provides measurements of ion and electron temperature profiles in LHD with a spatial resolution of 2 cm and a maximum time resolution of 5 ms (typically 20 ms). Ion temperature profiles from the XICS diagnostic are possible under conditions where charge exchange recombination spectroscopy (CXRS) is not possible (high density) or is perturbative to the plasma (low density or radio frequency heated plasmas). Measurements are made by using a spherically bent crystal to provide a spectrally resolved 1D image of the plasma from line integrated emission of helium-like Ar(16 +). The final hardware design and configuration are detailed along with the calibration procedures. Line-integrated ion and electron temperature measurements are presented, and the measurement accuracy is discussed. Finally central temperature measurements from the XICS system are compared to measurements from the Thomson scattering and CXRS systems, showing excellent agreement.

The radial gradients and collisional properties of solar wind electrons

NASA Technical Reports Server (NTRS)

Gilvie, K. W.; Scudder, J. D.

1977-01-01

The plasma instrument on Mariner 10 carried out measurements of electron density and temperature in the interplanetary medium between heliocentric distances of 0.85 and 0.45 AU. Due to the stable coronal configuration and low solar activity during the period of observation, the radial variations of these quantities could be obtained. The power-law exponent of the core temperature was measured to be -0.3 + or - 0.04, and the halo temperature was found to be almost independent of heliocentric distance. The exponent of the power law for the density variation was 2.5 + or - 0.2 and the extrapolated value at 1 AU was consistent with measured values during the same period. Calculations of the core electron self-collision time, and the core-halo equipartition time were made as a function of radial distance. These measurements indicate a macroscale picture of a Coulomb-collisional core and a collisionless isothermal halo. Extrapolating back to the sun, core and halo temperatures become equal at a radial distance of approx. 2-15 radii.

Microstructural stability of wrought, laser and electron beam glazed NARloy-Z alloy at elevated temperatures

NASA Technical Reports Server (NTRS)

Singh, J.; Jerman, G.; Bhat, B.; Poorman, R.

1993-01-01

Microstructure of wrought, laser, and electron-beam glazed NARloy-Z(Cu-3 wt.% Ag-0.5 wt.% Zr) was investigated for thermal stability at elevated temperatures (539 to 760 C (1,100 to 1,400 F)) up to 94 h. Optical and scanning electron microscopy and electron probe microanalysis were employed for studying microstructural evolution and kinetics of precipitation. Grain boundary precipitation and precipitate free zones (PFZ's) were observed in the wrought alloy after exposing to temperatures above 605 C (1,120 F). The fine-grained microstructure observed in the laser and electron-beam glazed NARloy-Z was much more stable at elevated temperatures. Microstructural changes correlated well with hardness measurements.

Electron-Temperature Dependence of the Recombination of NH4(+)((NH3)(sub n) Ions with Electrons

NASA Technical Reports Server (NTRS)

Skrzypkowski, M. P.; Johnson, R.

1997-01-01

The two-body recombination of NH4(+)(NH3)(sub 2,3) cluster-ions with electrons has been studied in an afterglow experiment in which the electron temperature T, was elevated by radio-frequency heating from 300 K up to 900 K. The recombination coefficients for the n = 2 and n = 3 cluster ions were found to be equal, alpha(sub 2, sup(2)) = alpha(sub 3, sup(2)) = (4.8 +/- 0.5) x 10(exp - 6)cu cm/s, and to vary with electron temperature as T(sub c, sup -0.65) rather than to be nearly temperature-independent as had been inferred from measurements in microwave-heated plasmas.

Ion and Electron Heating Characteristics of Magnetic Re- Connection in Mast Tokamak Merging Experiment

NASA Astrophysics Data System (ADS)

Tanabe, Hiroshi; Inomoto, Michiaki; Ono, Yasushi; Yamada, Takuma; Imazawa, Ryota; Cheng, Chio-Zong

2016-07-01

We present results of recent studies of high power heating of magnetic reconnection, the fundamental process of several astrophysical events such as solar flare, in the Mega Amp Spherical Tokamak (MAST) - the world largest merging experiment. In addition to the previously reported significant reconnection heating up to ˜1keV [1], detailed local profiles of electron and ion temperature have been measured using a ultra-fine 300 channel Ruby- and a 130 channel YAG-Thomson scattering and a new 32 channel ion Doppler tomography diagnostics [2]. 2D profile measurement of electron temperature revealed highly localized heating structure at the X point with the characteristic scale length of 0.02-0.05m0.3T), a thick layer of closed flux surface surrounding the current sheet sustains the temperature profile for longer time than the electron and ion energy relaxation time ˜4-10ms, finally forming triple peak structures of ion and electron temperatures at the X point and in the downstream. While the peak electron temperature at the X point increases with toroidal field, the bulk electron temperature and the ion temperature in the downstream are unaffected. [1] Y. Ono et.al., Plasma Phys. Control. Fusion 54, 124039 (2012) [2] H. Tanabe et. al., Nucl. Fusion 53, 093027 (2013). [3] H. Tanabe et.al., Phys. Rev. Lett. 115, 215004 (2015)

Reversed magnetic shear suppression of electron-scale turbulence on NSTX

NASA Astrophysics Data System (ADS)

Yuh, Howard Y.; Levinton, F. M.; Bell, R. E.; Hosea, J. C.; Kaye, S. M.; Leblanc, B. P.; Mazzucato, E.; Smith, D. R.; Domier, C. W.; Luhmann, N. C.; Park, H. K.

2009-11-01

Electron thermal internal transport barriers (e-ITBs) are observed in reversed (negative) magnetic shear NSTX discharges^1. These e-ITBs can be created with either neutral beam heating or High Harmonic Fast Wave (HHFW) RF heating. The e-ITB location occurs at the location of minimum magnetic shear determined by Motional Stark Effect (MSE) constrained equilibria. Statistical studies show a threshold condition in magnetic shear for e-ITB formation. High-k fluctuation measurements at electron turbulence wavenumbers^3 have been made under several different transport regimes, including a bursty regime that limits temperature gradients at intermediate magnetic shear. The growth rate of fluctuations has been calculated immediately following a change in the local magnetic shear, resulting in electron temperature gradient relaxation. Linear gyrokinetic simulation results for NSTX show that while measured electron temperature gradients exceed critical linear thresholds for ETG instability, growth rates can remain low under reversed shear conditions up to high electron temperatures gradients. ^1H. Yuh, et. al., PoP 16, 056120 ^2D.R. Smith, E. Mazzucato et al., RSI 75, 3840 ^3E. Mazzucato, D.R. Smith et al., PRL 101, 075001

Extracting the Electron-Ion Temperature Relaxation Rate from Ion Stopping Experiments

NASA Astrophysics Data System (ADS)

Grabowski, Paul E.; Frenje, Johan A.; Benedict, Lorin X.

2016-10-01

Direct measurement of i-e equilibration rates at ICF-relevant conditions is a big challenge, as it is difficult to differentiate from other sinks and sources of energy, such as heat conduction and pdV work. Another method is to use information from ion stopping experiments. Such experiments at the OMEGA laser have made precision energy loss measurements of fusion products at these conditions. Combined with the multimonochromatic x-ray imager technique, which gives temporally and spatially resolved electron temperature and density, we have a robust stopping experiment. We propose to use such stopping measurements to assess the i-e temperature relaxation rate, since both processes involve energy exchange between electrons and ions. We require that the fusion products are 1) much faster than the thermal ions so that i-i collisions are negligible compared to i-e collisions and 2) slower than the thermal electrons so that the stopping obeys a linear friction law. Then the Coulomb logarithms associated with ion stopping and i-e temperature relaxation rate are identical and a measurement of the former provides the latter. Prepared by LLNL under Contract DE-AC52-07NA27344.

Electron density profile measurements at a self-focusing ion beam with high current density and low energy extracted through concave electrodes.

PubMed

Fujiwara, Y; Hirano, Y; Kiyama, S; Nakamiya, A; Koguchi, H; Sakakita, H

2014-02-01

The self-focusing phenomenon has been observed in a high current density and low energy ion beam. In order to study the mechanism of this phenomenon, a special designed double probe to measure the electron density and temperature is installed into the chamber where the high current density ion beam is injected. Electron density profile is successfully measured without the influence of the ion beam components. Estimated electron temperature and density are ∼0.9 eV and ∼8 × 10(8) cm(-3) at the center of ion beam cross section, respectively. It was found that a large amount of electrons are spontaneously accumulated in the ion beam line in the case of self-forcing state.

Electron Temperature Gradient Scale Measurements in ICRF Heated Plasmas at Alcator C-Mod

NASA Astrophysics Data System (ADS)

Houshmandyar, Saeid; Phillips, Perry E.; Rowan, William L.; Howard, Nathaniel T.; Greenwald, Martin

2016-10-01

It is generally believed that the temperature gradient is a driving mechanism for the turbulent transport in hot and magnetically confined plasmas. A feature of many anomalous transport models is the critical threshold value (LC) for the gradient scale length, above which both the turbulence and the heat transport increases. This threshold is also predicted by the recent multi-scale gyrokinetic simulations, which are focused on addressing the electron (and ion) heat transport in tokamaks. Recently, we have established an accurate technique (BT-jog) to directly measure the electron temperature gradient scale length (LTe =Te / ∇T) profile, using a high-spatial resolution radiometer-based electron cyclotron emission (ECE) diagnostic. For the work presented here, electrons are heated by ion cyclotron range of frequencies (ICRF) through minority heating in L-mode plasmas at different power levels, TRANSP runs determine the electron heat fluxes and the scale lengths are measured through the BT-jog technique. Furthermore, the experiment is extended for different plasma current and electron densities by which the parametric dependence of LC on magnetic shear, safety factor and density will be investigated. This work is supported by U.S. DoE OFES, under Award No. DE-FG03-96ER-54373.

Calibrations of the LHD Thomson scattering system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamada, I., E-mail: yamadai@nifs.ac.jp; Funaba, H.; Yasuhara, R.

2016-11-15

The Thomson scattering diagnostic systems are widely used for the measurements of absolute local electron temperatures and densities of fusion plasmas. In order to obtain accurate and reliable temperature and density data, careful calibrations of the system are required. We have tried several calibration methods since the second LHD experiment campaign in 1998. We summarize the current status of the calibration methods for the electron temperature and density measurements by the LHD Thomson scattering diagnostic system. Future plans are briefly discussed.

Calibrations of the LHD Thomson scattering system.

PubMed

Yamada, I; Funaba, H; Yasuhara, R; Hayashi, H; Kenmochi, N; Minami, T; Yoshikawa, M; Ohta, K; Lee, J H; Lee, S H

2016-11-01

The Thomson scattering diagnostic systems are widely used for the measurements of absolute local electron temperatures and densities of fusion plasmas. In order to obtain accurate and reliable temperature and density data, careful calibrations of the system are required. We have tried several calibration methods since the second LHD experiment campaign in 1998. We summarize the current status of the calibration methods for the electron temperature and density measurements by the LHD Thomson scattering diagnostic system. Future plans are briefly discussed.

High time resolved electron temperature measurements by using the multi-pass Thomson scattering system in GAMMA 10/PDX.

PubMed

Yoshikawa, Masayuki; Yasuhara, Ryo; Ohta, Koichi; Chikatsu, Masayuki; Shima, Yoriko; Kohagura, Junko; Sakamoto, Mizuki; Nakashima, Yousuke; Imai, Tsuyoshi; Ichimura, Makoto; Yamada, Ichihiro; Funaba, Hisamichi; Minami, Takashi

2016-11-01

High time resolved electron temperature measurements are useful for fluctuation study. A multi-pass Thomson scattering (MPTS) system is proposed for the improvement of both increasing the TS signal intensity and time resolution. The MPTS system in GAMMA 10/PDX has been constructed for enhancing the Thomson scattered signals for the improvement of measurement accuracy. The MPTS system has a polarization-based configuration with an image relaying system. We optimized the image relaying optics for improving the multi-pass laser confinement and obtaining the stable MPTS signals over ten passing TS signals. The integrated MPTS signals increased about five times larger than that in the single pass system. Finally, time dependent electron temperatures were obtained in MHz sampling.

Half-life of the electron-capture decay of {sup 97}Ru: Precision measurement shows no temperature dependence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goodwin, J. R.; Golovko, V. V.; Iacob, V. E.

2009-10-15

We have measured the half-life of the electron-capture (ec) decay of {sup 97}Ru in a metallic environment, both at low temperature (19 K), and also at room temperature. We find the half-lives at both temperatures to be the same within 0.1%. This demonstrates that a recent claim that the ec decay half-life for {sup 7}Be changes by 0.9%{+-}0.2% under similar circumstances certainly cannot be generalized to other ec decays. Our results for the half-life of {sup 97}Ru, 2.8370(14) d at room temperature and 2.8382(14) d at 19 K, are consistent with, but much more precise than, previous room-temperature measurements. Inmore » addition, we have also measured the half-lives of the {beta}{sup -}-emitters {sup 103}Ru and {sup 105}Rh at both temperatures, and found them also to be unchanged.« less

Device Would Monitor Body Parameters Continuously

NASA Technical Reports Server (NTRS)

Cook, Joseph S., Jr.

1995-01-01

Proposed miniature electronic circuit continuously measures temperature of human subject. Once mounted on subject's skin with medical adhesive tape, electronic thermometer remains in thermal equilibrium with subject's body; thereafter, no need to wait until thermometer reaches body temperature before taking reading. Design provides for switches used to set alarm alerting medical attendants if subject's temperature exceeds critical level. For use on very young child, electronic thermometer sewed into shirt or other suitable garment; device held in contact with skin, and child could not swallow it. Replacement of sensor and computing algorithm changes temperature monitor to cardiorespiratory monitor.

Morphology and electronic transport of polycrystalline pentacene thin-film transistors

NASA Astrophysics Data System (ADS)

Knipp, D.; Street, R. A.; Völkel, A. R.

2003-06-01

Temperature-dependent measurements of thin-film transistors were performed to gain insight in the electronic transport of polycrystalline pentacene. Devices were fabricated with plasma-enhanced chemical vapor deposited silicon nitride gate dielectrics. The influence of the dielectric roughness and the deposition temperature of the thermally evaporated pentacene films were studied. Although films on rougher gate dielectrics and films prepared at low deposition temperatures exhibit similar grain size, the electronic properties are different. Increasing the dielectric roughness reduces the free carrier mobility, while low substrate temperature leads to more and deeper hole traps.

Measurement of brightness temperature of two-dimensional electron gas in channel of a high electron mobility transistor at ultralow dissipation power

NASA Astrophysics Data System (ADS)

Korolev, A. M.; Shulga, V. M.; Turutanov, O. G.; Shnyrkov, V. I.

2016-07-01

A technically simple and physically clear method is suggested for direct measurement of the brightness temperature of two-dimensional electron gas (2DEG) in the channel of a high electron mobility transistor (HEMT). The usage of the method was demonstrated with the pseudomorphic HEMT as a specimen. The optimal HEMT dc regime, from the point of view of the "back action" problem, was found to belong to the unsaturated area of the static characteristics possibly corresponding to the ballistic electron transport mode. The proposed method is believed to be a convenient tool to explore the ballistic transport, electron diffusion, 2DEG properties and other electrophysical processes in heterostructures.

Winter nighttime ion temperatures and energetic electrons from OGO 6 plasma measurements

NASA Technical Reports Server (NTRS)

Sanatani, S.; Breig, E. L.

1981-01-01

In the reported investigation, ion temperature and suprathermal electron flux data were acquired with the retarding potential analyzer on board the OGO 6 satellite when it was in solar eclipse. Attention is given 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 Atlantic. 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 much lower geomagnetic latitudes in the same longitude sector.

Tracking the ultrafast XUV optical properties of x-ray free-electron-laser heated matter with high-order harmonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Gareth O.; Künzel, S.; Daboussi, S.

We present measurements of photon absorption by free electrons as a solid is transformed to plasma. A femtosecond x-ray free-electron laser is used to heat a solid, which separates the electron and ion heating time scales. The changes in absorption are measured with an independent probe pulse created through high-order-harmonic generation. We find an increase in electron temperature to have a relatively small impact on absorption, contrary to several predictions, whereas ion heating increases absorption. Here, we compare the data to current theoretical and numerical approaches and find that a smoother electronic structure yields a better fit to the data,more » suggestive of a temperature-dependent electronic structure in warm dense matter.« less

Tracking the ultrafast XUV optical properties of x-ray free-electron-laser heated matter with high-order harmonics

DOE PAGES

Williams, Gareth O.; Künzel, S.; Daboussi, S.; ...

2018-02-14

We present measurements of photon absorption by free electrons as a solid is transformed to plasma. A femtosecond x-ray free-electron laser is used to heat a solid, which separates the electron and ion heating time scales. The changes in absorption are measured with an independent probe pulse created through high-order-harmonic generation. We find an increase in electron temperature to have a relatively small impact on absorption, contrary to several predictions, whereas ion heating increases absorption. Here, we compare the data to current theoretical and numerical approaches and find that a smoother electronic structure yields a better fit to the data,more » suggestive of a temperature-dependent electronic structure in warm dense matter.« less

Development of optical diagnostics for performance evaluation of arcjet thrusters

NASA Technical Reports Server (NTRS)

Cappelli, Mark A.

1995-01-01

Laser and optical emission-based measurements have been developed and implemented for use on low-power hydrogen arcjet thrusters and xenon-propelled electric thrusters. In the case of low power hydrogen arcjets, these laser induce fluorescence measurements constitute the first complete set of data that characterize the velocity and temperature field of such a device. The research performed under the auspices of this NASA grant includes laser-based measurements of atomic hydrogen velocity and translational temperature, ultraviolet absorption measurements of ground state atomic hydrogen, Raman scattering measurements of the electronic ground state of molecular hydrogen, and optical emission based measurements of electronically excited atomic hydrogen, electron number density, and electron temperature. In addition, we have developed a collisional-radiative model of atomic hydrogen for use in conjunction with magnetohydrodynamic models to predict the plasma radiative spectrum, and near-electrode plasma models to better understand current transfer from the electrodes to the plasma. In the final year of the grant, a new program aimed at developing diagnostics for xenon plasma thrusters was initiated, and results on the use of diode lasers for interrogating Hall accelerator plasmas has been presented at recent conferences.

Electron Temperatures and Flow Speeds of the Low Solar Corona: MACS Results from the Total Solar Eclipse of 29 March 2006 in Libya

NASA Technical Reports Server (NTRS)

Reginald, Nelson L.; Davila, Joseph M.; SaintCyr, O.; Rabin, Douglas M.; Guhathakurta, Madhulika; Hassler, Donald M.; Gashut, Hadi

2011-01-01

An experiment was conducted in conjunction with the total solar eclipse on 29 March 2006 in Libya to measure both the electron temperature and its flow speed simultaneously at multiple locations in the low solar corona by measuring the visible K-coronal spectrum. Coronal model spectra incorporating the effects of electron temperature and its flow speed were matched with the measured K-coronal spectra to interpret the observations. Results show electron temperatures of (1.10 +/- 0.05) MK, (0.70 +/- 0.08) MK, and (0.98 +/- 0.12) MK, at 1.1 Solar Radius from Sun center in the solar north, east and west, respectively, and (0.93 +/- 0.12) MK, at 1.2 Solar Radius from Sun center in the solar west. The corresponding outflow speeds obtained from the spectral fit are (103 +/- 92) km/s, (0 + 10) km/s, (0+10) km/s, and (0+10) km/s. Since the observations were taken only at 1.1 Solar Radius and 1.2 Solar Radius from Sun center, these speeds, consistent with zero outflow, are in agreement with expectations and provide additional confirmation that the spectral fitting method is working. The electron temperature at 1.1 Solar Radius from Sun center is larger at the north (polar region) than the east and west (equatorial region).

Observation of the effects of stronger magnetic fields on warm, higher energy electrons and ion beams transiting a double layer in a helicon plasma

NASA Astrophysics Data System (ADS)

Scharer, John; Sung, Yung-Ta; Li, Yan

2017-10-01

Fast, two-temperature electrons (>80 eV, Te =13 eV tail, 4 eV bulk) with substantial tail density fractions are created at low (< = 1.7 mtorr) Ar pressure @ 340 G in the antenna region with nozzle mirror ratio of 1.4 on MadHeX @ 900W. These distributions including a fast tail are observed upstream of a double layer. The fast, untrapped tail electrons measured downstream of the double layer have a higher temperature of 13 eV than the trapped, upstream electrons of 4 eV temperature. Upstream plasma potential fluctuations of + - 30 percent are observed. An RF-compensated Langmuir probe is used to measure the electron temperatures and densities and OES, mm wave IF and an RPA for the IEDF are also utilized. As the magnetic field is increased to 1020 G, an increase in the electron temperature and density upstream of the double layer is observed with Te= 15-25 eV with a primarily single temperature mode. Accelerated ion beam energies in the range of 65-120 eV are observed as the magnetic field is increased from 340 to 850 G. The role of the nozzle, plasma double layer and helicon wave coupling on the EEDF and ion acceleration will be discussed. Research supported in part by the University of Wisconsin.

Effects of discharge chamber length on the negative ion generation in volume-produced negative hydrogen ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Kyoung-Jae; Jung, Bong-Ki; An, YoungHwa

2014-02-15

In a volume-produced negative hydrogen ion source, control of electron temperature is essential due to its close correlation with the generation of highly vibrationally excited hydrogen molecules in the heating region as well as the generation of negative hydrogen ions by dissociative attachment in the extraction region. In this study, geometric effects of the cylindrical discharge chamber on negative ion generation via electron temperature changes are investigated in two discharge chambers with different lengths of 7.5 cm and 11 cm. Measurements with a radio-frequency-compensated Langmuir probe show that the electron temperature in the heating region is significantly increased by reducingmore » the length of the discharge chamber due to the reduced effective plasma size. A particle balance model which is modified to consider the effects of discharge chamber configuration on the plasma parameters explains the variation of the electron temperature with the chamber geometry and gas pressure quite well. Accordingly, H{sup −} ion density measurement with laser photo-detachment in the short chamber shows a few times increase compared to the longer one at the same heating power depending on gas pressure. However, the increase drops significantly as operating gas pressure decreases, indicating increased electron temperatures in the extraction region degrade dissociative attachment significantly especially in the low pressure regime. It is concluded that the increase of electron temperature by adjusting the discharge chamber geometry is efficient to increase H{sup −} ion production as long as low electron temperatures are maintained in the extraction region in volume-produced negative hydrogen ion sources.« less

Improved analysis techniques for cylindrical and spherical double probes.

PubMed

Beal, Brian; Johnson, Lee; Brown, Daniel; Blakely, Joseph; Bromaghim, Daron

2012-07-01

A versatile double Langmuir probe technique has been developed by incorporating analytical fits to Laframboise's numerical results for ion current collection by biased electrodes of various sizes relative to the local electron Debye length. Application of these fits to the double probe circuit has produced a set of coupled equations that express the potential of each electrode relative to the plasma potential as well as the resulting probe current as a function of applied probe voltage. These equations can be readily solved via standard numerical techniques in order to determine electron temperature and plasma density from probe current and voltage measurements. Because this method self-consistently accounts for the effects of sheath expansion, it can be readily applied to plasmas with a wide range of densities and low ion temperature (T(i)/T(e) ≪ 1) without requiring probe dimensions to be asymptotically large or small with respect to the electron Debye length. The presented approach has been successfully applied to experimental measurements obtained in the plume of a low-power Hall thruster, which produced a quasineutral, flowing xenon plasma during operation at 200 W on xenon. The measured plasma densities and electron temperatures were in the range of 1 × 10(12)-1 × 10(17) m(-3) and 0.5-5.0 eV, respectively. The estimated measurement uncertainty is +6%∕-34% in density and +∕-30% in electron temperature.

Thermal Structure and Energy Influx to the Day-and Nightside Venus Ionosphere.

PubMed

Knudsen, W C; Spenner, K; Whitten, R C; Spreiter, J R; Miller, K L; Novak, V

1979-07-06

Pioneer Venus in situ measurements made with the retarding potential analyzer reveal strong variations in the nightside ionospheric plasma density from location to location in some orbits and from orbit to orbit. The ionopause is evident at night as a relatively abrupt decrease in the thermal plasma concentration from a few hundred to ten or fewer ions per cubic centimeter. The nightside ion and electron temperatures above an altitude of 250 kilometers, within the ionosphere and away from the terminator, are comparable in magnitude and have a value at the ionopause of approximately 8000 K. The electron temperature increases from a few tens of thousands of degrees Kelvin just outside the ionopause to several hundreds of thoussands of degrees Kelvin further into the shocked solar wind. The coldest ion temperatures measured at an altitude of about 145 kilometers are 140 to 150 K and are still evidently above the neutral temperature. Preliminary day-and nightside model ion and electron temperature height profiles are compared with measured profiles. To raise the model ion temperature to the measured ion temperature on both day-and nightsides, it was necessary to include an ion energy source of the order of 4 x 10(-3) erg per square centimeter per second, presumably Joule heating. The heat flux through the electron gas from the solar wind into the neutral atmosphere averaged over day and night may be as large as 0.05 erg per square centimeter per second. Integrated over the planet surface, this heat flux represents one-tenth of the solar wind energy expended in drag on the sunward ionopause hemisphere.

MAVEN observations of electron temperatures in the dayside ionosphere at Mars

NASA Astrophysics Data System (ADS)

Sakai, S.; Cravens, T.; Andersson, L.; Fowler, C. M.; Thiemann, E.; Eparvier, F. G.; Bougher, S. W.; Rahmati, A.; Reedy, N. L.; Mitchell, D. L.; Mazelle, C. X.; Mahaffy, P. R.; Jakosky, B. M.

2016-12-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) have observed the ionospheric electron temperature at Mars since November 2014. The only in-situ measurements of plasma temperatures were provided by the two Viking landers in 1976 before the MAVEN mission. The ionospheric electron temperatures are particularly important for determining the neutral escape rate from the atmosphere of Mars. We have investigated the electron temperatures on the dayside ionosphere using the Langmuir Probe and Waves instrument onboard MAVEN. The temperatures are studied in two regions of (1) the crustal magnetic field and (2) the solar wind/induced (or draped) magnetic field. We also focused on how temperatures vary with solar zenith angle (SZA) and the solar extreme ultraviolet (EUV) irradiances. The electron temperatures did not vary much due to the SZA variation, but increased when the solar EUV irradiances are high. This means the ionospheric temperatures are sensitive to the solar activity. Furthermore, we investigated the correlation of electron temperatures against magnetic field configurations under the same EUV irradiances. The electron temperatures in the crustal region were lower than those in the draped region. One possible explanation is that the energy input from high altitude, which is related to the tail and solar wind electrons, might control the temperatures in the draped region. Vertical heat conductance in the draped region could also affect the electron temperatures (with a greater effect in the draped region), so that electrons cooled at low altitude tend to transport to high altitude. However, the electron heating is more local in the draped region, and the electrons would be heated efficiently. Therefore, the electron temperatures in the draped region were higher than those in the crustal region. It is implied that the rate of atmospheric escape, which is attributed to photochemical escape, depends on the topology of the magnetic fields.

Advanced Sensor and Packaging Technologies for Intelligent Adaptive Engine Controls (Preprint)

DTIC Science & Technology

2013-05-01

combination of micro-electromechanical systems (MEMS) sensor technology, novel ceramic materials, high - temperature electronics, and advanced harsh...with simultaneous pressure measurements up to 1,000 psi. The combination of a high - temperature , high -pressure-ratio compressor system, and adaptive...combination of micro-electromechanical systems (MEMS) sensor technology, novel ceramic materials, high temperature electronics, and advanced harsh

Multichannel temperature control for solar heating

NASA Technical Reports Server (NTRS)

Currie, J. R.

1978-01-01

Multiplexer/amplifier circuit monitors temperatures and temperature differences. Although primarily designed for cycle control in solar-heating systems, it can also measure temperatures in motors, ovens, electronic hardware, and other equipment.

Fuel temperature counter

Treesearch

John R. Murray; Charles W. Philpot

1963-01-01

Fuel temperature is and has always been difficult to measure. To understand better the problem of fire and fire weather behavior, it is important to measure this variable. We have developed for field use a new fuel temperature counter which can be used to obtain such measurements quickly and easily. This electronic recording instrument is easy to construct and operate...

Thomson scattering measurements from asymmetric interpenetrating plasma flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, J. S., E-mail: ross36@llnl.gov; Moody, J. D.; Fiuza, F.

2014-11-15

Imaging Thomson scattering measurements of collective ion-acoustic fluctuations have been utilized to determine ion temperature and density from laser produced counter-streaming asymmetric flows. Two foils are heated with 8 laser beams each, 500 J per beam, at the Omega Laser facility. Measurements are made 4 mm from the foil surface using a 60 J 2ω probe laser with a 200 ps pulse length. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the multi-ion species, asymmetric flows theoretical form factor for the ion feature such that the ion temperatures, ion densities, and flow velocities formore » each plasma flow are determined.« less

Electron and ion dynamics study of iron in warm dense matter regime by time-resolved XAS measurements and from first-principles

NASA Astrophysics Data System (ADS)

Ogitsu, T.; Fernandez-Paãella, A.; Correa, A.; Engelhorn, K.; Barbrel, B.; Prendergast, D. G.; Pemmaraju, D.; Beckwith, M.; Kraus, D.; Hamel, S.; Cho, B. I.; Jin, L.; Wong, J.; Heinman, P.; Collins, G. W.; Falcone, R.; Ping, Y.

2016-10-01

We present a study of the electron-phonon coupling of warm dense iron upon femtosecond laser excitation by time-resolved x-ray absorption near edge spectroscopy (XANES). The dynamics of iron in electron-ion non-equilibrium conditions was studied using ab-initio density-functional-theory (DFT) simulations combined with the Two Temperature Model (TTM) where spatial inhomogeneity of electron (and ion) temperature(s) due to short ballistic electron transport length in iron was explicitly taken into consideration. Detailed comparison between our simulation results and experiments indicates that the ion temperature dependence on specific heat and on electron-phonon coupling also plays a relevant role in modeling the relaxation dynamics of electrons and ions. These results are the first experimental evidence of the suppression of the electron-phonon coupling factor of a transition metal at electron temperatures ranging 5000- 10000 K. This work was performed under DOE contract DE-AC52-07NA27344 with support from OFES Early Career program and LLNL LDRD program.

Evaluating the Uncertainties in the Electron Temperature and Radial Speed Measurements Using White Light Corona Eclipse Observations

NASA Technical Reports Server (NTRS)

Reginald, Nelson L.; Davilla, Joseph M.; St. Cyr, O. C.; Rastaetter, Lutz

2014-01-01

We examine the uncertainties in two plasma parameters from their true values in a simulated asymmetric corona. We use the Corona Heliosphere (CORHEL) and Magnetohydrodynamics Around the Sphere (MAS) models in the Community Coordinated Modeling Center (CCMC) to investigate the differences between an assumed symmetric corona and a more realistic, asymmetric one. We were able to predict the electron temperatures and electron bulk flow speeds to within +/-0.5 MK and +/-100 km s(exp-1), respectively, over coronal heights up to 5.0 R from Sun center.We believe that this technique could be incorporated in next-generation white-light coronagraphs to determine these electron plasma parameters in the low solar corona. We have conducted experiments in the past during total solar eclipses to measure the thermal electron temperature and the electron bulk flow speed in the radial direction in the low solar corona. These measurements were made at different altitudes and latitudes in the low solar corona by measuring the shape of the K-coronal spectra between 350 nm and 450 nm and two brightness ratios through filters centered at 385.0 nm/410.0 nm and 398.7 nm/423.3 nm with a bandwidth of is approximately equal to 4 nm. Based on symmetric coronal models used for these measurements, the two measured plasma parameters were expected to represent those values at the points where the lines of sight intersected the plane of the solar limb.

Interpretation of transport measurements in ZnO-thin films

NASA Astrophysics Data System (ADS)

Petukhov, Vladimir; Stoemenos, John; Rothman, Johan; Bakin, Andrey; Waag, Andreas

2011-01-01

In order to interpret results of temperature dependent Hall measurements in heteroepitaxial ZnO-thin films, we adopted a multilayer conductivity model considering carrier-transport through the interfacial layer with degenerate electron gas as well as the upper part of ZnO layers with lower conductivity. This model was applied to the temperature dependence of the carrier concentration and mobility measured by Hall effect in a ZnO-layer grown on c-sapphire with conventional high-temperature MgO and low-temperature ZnO buffer. We also compared our results with the results of maximum entropy mobility-spectrum analysis (MEMSA). The formation of the highly conductive interfacial layer was explained by analysis of transmission electron microscopy (TEM) images taken from similar layers.

Non-invasive probe diagnostic method for electron temperature and ion current density in atmospheric pressure plasma jet source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Young-Cheol; Kim, Yu-Sin; Lee, Hyo-Chang

2015-08-15

The electrical probe diagnostics are very hard to be applied to atmospheric plasmas due to severe perturbation by the electrical probes. To overcome this, the probe for measuring electron temperature and ion current density is indirectly contacted with an atmospheric jet source. The plasma parameters are obtained by using floating harmonic analysis. The probe is mounted on the quartz tube that surrounds plasma. When a sinusoidal voltage is applied to a probe contacting on a quartz tube, the electrons near the sheath at dielectric tube are collected and the probe current has harmonic components due to probe sheath nonlinearity. Frommore » the relation of the harmonic currents and amplitude of the sheath voltage, the electron temperature near the wall can be obtained with collisional sheath model. The electron temperatures and ion current densities measured at the discharge region are in the ranges of 2.7–3.4 eV and 1.7–5.2 mA/cm{sup 2} at various flow rates and input powers.« less

Temperature dependence of damage coefficient in electron irradiated solar cells

NASA Technical Reports Server (NTRS)

Faith, T. J.

1973-01-01

Measurements of light-generated current vs cell temperature on electron-irradiated n/p silicon solar cells show the temperature coefficient of this current to increase with increasing fluence for both 10-ohm and 20-ohm cells. A relationship between minority-carrier diffusion length and light-generated current was derived by combining measurements of these two parameters: vs fluence at room temperature, and vs cell temperature in cells irradiated to a fluence of 1 x 10 to the 15th power e/sq cm. This relationship was used, together with the light-generated current data, to calculate the temperature dependence of the diffusion-length damage coefficient. The results show a strong decrease in the damage coefficient with increasing temperature in the range experienced by solar panels in synchronous earth orbit.

Studies on color-center formation in glass utilizing measurements made during 1 to 3 MeV electron irradiation

NASA Technical Reports Server (NTRS)

Swyler, K. J.; Levy, P. W.

1976-01-01

The coloring of NBS 710 glass was studied using a facility for making optical absorption measurements during and after electron irradiation. The induced absorption contains three Gaussian shaped bands. The color center growth curves contain two saturating exponential and one linear components. After irradiation the coloring decays can be described by three decreasing exponentials. At room temperature both the coloring curve plateau and coloring rate increases with increasing dose rate. Coloring measurements made at fixed dose rate but at increasing temperature indicate: (1) The coloring curve plateau decreases with increasing temperature and coloring is barely measurable near 400 C. (2) The plateau is reached more rapidly as the temperature increases. (3) The decay occurring after irradiation cannot be described by Arrhenius kinetics. At each temperature the coloring can be explained by simple kinetics. The temperature dependence of the decay can be explained if it is assumed that the thermal untrapping is controlled by a distribution of activation energies.

A Eu/Tb-mixed MOF for luminescent high-temperature sensing

NASA Astrophysics Data System (ADS)

Wang, Huizhen; Zhao, Dian; Cui, Yuangjing; Yang, Yu; Qian, Guodong

2017-02-01

Temperature measurements and thermal mapping using luminescent MOF operating in the high-temperature range are of great interest in the micro-electronic diagnosis. In this paper, we report a thermostable Eu/Tb-mixed MOF Eu0.37Tb0.63-BTC-a exhibiting strong luminescence at elevated temperature, which can serve as a ratiometric luminescent thermometer for high-temperature range. The high-temperature operating range (313-473 K), high relative sensitivity and accurate temperature resolution, make such a Eu/Tb-mixed MOF useful for micro-electronic diagnosis.

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

NASA Technical Reports Server (NTRS)

Knudsen, William 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 gasses 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.

Electroluminescence of hot electrons in AlGaN/GaN high-electron-mobility transistors under radio frequency operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brazzini, Tommaso, E-mail: tommaso.brazzini@bristol.ac.uk; Sun, Huarui; Uren, Michael J.

2015-05-25

Hot electrons in AlGaN/GaN high electron mobility transistors are studied during radio frequency (RF) and DC operation by means of electroluminescence (EL) microscopy and spectroscopy. The measured EL intensity is decreased under RF operation compared to DC at the same average current, indicating a lower hot electron density. This is explained by averaging the DC EL intensity over the measured load line used in RF measurements, giving reasonable agreement. In addition, the hot electron temperature is lower by up to 15% under RF compared to DC, again at least partially explainable by the weighted averaging along the specific load line.more » However, peak electron temperature under RF occurs at high V{sub DS} and low I{sub DS} where EL is insignificant suggesting that any wear-out differences between RF and DC stress of the devices will depend on the balance between hot-carrier and field driven degradation mechanisms.« less

MAVEN observations of dayside peak electron densities in the ionosphere of Mars

NASA Astrophysics Data System (ADS)

Vogt, Marissa F.; Withers, Paul; Fallows, Kathryn; Andersson, Laila; Girazian, Zachary; Mahaffy, Paul R.; Benna, Mehdi; Elrod, Meredith K.; Connerney, John E. P.; Espley, Jared R.; Eparvier, Frank G.; Jakosky, Bruce M.

2017-01-01

The peak electron density in the dayside Martian ionosphere is a valuable diagnostic of the state of the ionosphere. Its dependence on factors like the solar zenith angle, ionizing solar irradiance, neutral scale height, and electron temperature has been well studied. The Mars Atmosphere and Volatile EvolutioN spacecraft's September 2015 "deep dip" orbits, in which the orbital periapsis was lowered to 125 km, provided the first opportunity since Viking to sample in situ a complete dayside electron density profile including the main peak. Here we present peak electron density measurements from 37 deep dip orbits and describe conditions at the altitude of the main peak, including the electron temperature and composition of the ionosphere and neutral atmosphere. We find that the dependence of the peak electron density and the altitude of the main peak on solar zenith angle are well described by analytical photochemical theory. Additionally, we find that the electron temperatures at the main peak display a dependence on solar zenith angle that is consistent with the observed variability in the peak electron density. Several peak density measurements were made in regions of large crustal magnetic field, but there is no clear evidence that the crustal magnetic field strength influences the peak electron density, peak altitude, or electron temperature. Finally, we find that the fractional abundance of O2+ and CO2+ at the peak altitude is variable but that the two species together consistently represent 95% of the total ion density.

Shot noise at high temperatures

NASA Astrophysics Data System (ADS)

Gutman, D. B.; Gefen, Yuval

2003-07-01

We consider the possibility of measuring nonequilibrium properties of the current correlation functions at high temperatures (and small bias). Through the example of the third cumulant of the current (S3) we demonstrate that odd-order correlation functions represent nonequilibrium physics even at small external bias and high temperatures. We calculate S3=y(eV/T)e2I for a quasi-one-dimensional diffusive constriction. We calculate the scaling function y in two regimes: when the scattering processes are purely elastic and when the inelastic electron-electron scattering is strong. In both cases we find that y interpolates between two constants. In the low- (high-) temperature limit y is strongly (weakly) enhanced (suppressed) by the electron-electron scattering.

Temperature-driven topological transition in 1T'-MoTe2

NASA Astrophysics Data System (ADS)

Berger, Ayelet Notis; Andrade, Erick; Kerelsky, Alexander; Edelberg, Drew; Li, Jian; Wang, Zhijun; Zhang, Lunyong; Kim, Jaewook; Zaki, Nader; Avila, Jose; Chen, Chaoyu; Asensio, Maria C.; Cheong, Sang-Wook; Bernevig, Bogdan A.; Pasupathy, Abhay N.

2018-01-01

The topology of Weyl semimetals requires the existence of unique surface states. Surface states have been visualized in spectroscopy measurements, but their connection to the topological character of the material remains largely unexplored. 1T'-MoTe2, presents a unique opportunity to study this connection. This material undergoes a phase transition at 240 K that changes the structure from orthorhombic (putative Weyl semimetal) to monoclinic (trivial metal), while largely maintaining its bulk electronic structure. Here, we show from temperature-dependent quasiparticle interference measurements that this structural transition also acts as a topological switch for surface states in 1T'-MoTe2. At low temperature, we observe strong quasiparticle scattering, consistent with theoretical predictions and photoemission measurements for the surface states in this material. In contrast, measurements performed at room temperature show the complete absence of the scattering wavevectors associated with the trivial surface states. These distinct quasiparticle scattering behaviors show that 1T'-MoTe2 is ideal for separating topological and trivial electronic phenomena via temperature-dependent measurements.

Comparison of cryogenic low-pass filters.

PubMed

Thalmann, M; Pernau, H-F; Strunk, C; Scheer, E; Pietsch, T

2017-11-01

Low-temperature electronic transport measurements with high energy resolution require both effective low-pass filtering of high-frequency input noise and an optimized thermalization of the electronic system of the experiment. In recent years, elaborate filter designs have been developed for cryogenic low-level measurements, driven by the growing interest in fundamental quantum-physical phenomena at energy scales corresponding to temperatures in the few millikelvin regime. However, a single filter concept is often insufficient to thermalize the electronic system to the cryogenic bath and eliminate spurious high frequency noise. Moreover, the available concepts often provide inadequate filtering to operate at temperatures below 10 mK, which are routinely available now in dilution cryogenic systems. Herein we provide a comprehensive analysis of commonly used filter types, introduce a novel compact filter type based on ferrite compounds optimized for the frequency range above 20 GHz, and develop an improved filtering scheme providing adaptable broad-band low-pass characteristic for cryogenic low-level and quantum measurement applications at temperatures down to few millikelvin.

Comparison of cryogenic low-pass filters

NASA Astrophysics Data System (ADS)

Thalmann, M.; Pernau, H.-F.; Strunk, C.; Scheer, E.; Pietsch, T.

2017-11-01

Low-temperature electronic transport measurements with high energy resolution require both effective low-pass filtering of high-frequency input noise and an optimized thermalization of the electronic system of the experiment. In recent years, elaborate filter designs have been developed for cryogenic low-level measurements, driven by the growing interest in fundamental quantum-physical phenomena at energy scales corresponding to temperatures in the few millikelvin regime. However, a single filter concept is often insufficient to thermalize the electronic system to the cryogenic bath and eliminate spurious high frequency noise. Moreover, the available concepts often provide inadequate filtering to operate at temperatures below 10 mK, which are routinely available now in dilution cryogenic systems. Herein we provide a comprehensive analysis of commonly used filter types, introduce a novel compact filter type based on ferrite compounds optimized for the frequency range above 20 GHz, and develop an improved filtering scheme providing adaptable broad-band low-pass characteristic for cryogenic low-level and quantum measurement applications at temperatures down to few millikelvin.

Spatially resolved density and ionization measurements of shocked foams using x-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J.; Keiter, P. A.; Montgomery, D. S.

2016-09-28

We present experiments at the Trident laser facility demonstrating the use of x-ray fluorescence (XRF) to simultaneously measure density, ionization state populations, and electron temperature in shocked foams. An imaging x-ray spectrometer obtained spatially resolved measurements of Ti K-α emission. Density profiles were measured from K-α intensity. Ti ionization state distributions and electron temperatures were inferred by fitting K-α spectra to spectra from CRETIN simulations. This work shows that XRF provides a powerful tool to complement other diagnostics to make equation of state measurements of shocked materials containing a suitable tracer element.

N2 Temperature of Vibration instrument for sounding rocket observation in the lower thermosphere

NASA Astrophysics Data System (ADS)

Kurihara, J.; Iwagami, N.; Oyama, K.-I.

2013-11-01

The N2 Temperature of Vibration (NTV) instrument was developed to study energetics and structure of the lower thermosphere, applying the Electron Beam Fluorescence (EBF) technique to measurements of vibrational temperature, rotational temperature and number density of atmospheric N2. The sounding rocket experiments using this instrument have been conducted four times, including one failure of the electron gun. Aerodynamic effects on the measurement caused by the supersonic motion of the rocket were analyzed quantitatively using three-dimensional simulation of Direct Simulation Monte Carlo (DSMC) method, and the absolute density profile was obtained through the correction of the spin modulation.

Filtering peripheral high temperature electrons in a cylindrical rf-driven plasmas by an axisymmetric radial magnetic field

NASA Astrophysics Data System (ADS)

Akahoshi, Hikaru; Takahashi, Kazunori; Ando, Akira

2018-03-01

High temperature electrons generated near a radial wall of a cylindrical source tube in a radiofrequency (rf) inductively-coupled plasma is filtered by an axisymmetric radial magnetic field formed near the source exit by locating annular permanent magnets, where the axial magnetic field strength in the radially central region is fairly uniform inside the source tube and is close to zero near the source exit. The source is operated at 3 mTorr in argon and the rf antenna is powered by a 13.56 MHz and 400 W rf generator. Measurement of electron energy probability functions shows the presence of the peripheral high temperature electrons inside the source, while the temperature of the peripheral electrons downstream of the source is observed to be reduced.

Method to estimate the electron temperature and neutral density in a plasma from spectroscopic measurements using argon atom and ion collisional-radiative models.

PubMed

Sciamma, Ella M; Bengtson, Roger D; Rowan, W L; Keesee, Amy; Lee, Charles A; Berisford, Dan; Lee, Kevin; Gentle, K W

2008-10-01

We present a method to infer the electron temperature in argon plasmas using a collisional-radiative model for argon ions and measurements of electron density to interpret absolutely calibrated spectroscopic measurements of argon ion (Ar II) line intensities. The neutral density, and hence the degree of ionization of this plasma, can then be estimated using argon atom (Ar I) line intensities and a collisional-radiative model for argon atoms. This method has been tested for plasmas generated on two different devices at the University of Texas at Austin: the helicon experiment and the helimak experiment. We present results that show good correlation with other measurements in the plasma.

Innovative Technology Transfer Partnerships

NASA Technical Reports Server (NTRS)

Kohler, Jeff

2004-01-01

The National Aeronautics and Space Administration (NASA) seeks to license its Advanced Tire and Strut Pressure Monitor (TSPM) technology. The TSPM is a handheld system to accurately measure tire and strut pressure and temperature over a wide temperature range (20 to 120 OF), as well as improve personnel safety. Sensor accuracy, electronics design, and a simple user interface allow operators quick, easy access to required measurements. The handheld electronics, powered by 12-VAC or by 9-VDC batteries, provide the user with an easy-to-read visual display of pressure/temperature or the streaming of pressure/temperature data via an RS-232 interface. When connected to a laptop computer, this new measurement system can provide users with automated data recording and trending, eliminating the chance for data hand-recording errors. In addition, calibration software allows for calibration data to be automatically utilized for the generation of new data conversion equations, simplifying the calibration processes that are so critical to reliable measurements. The design places a high-accuracy pressure sensor (also used as a temperature sensor) as close to the tire or strut measurement location as possible, allowing the user to make accurate measurements rapidly, minimizing the amount of high-pressure volumes, and allowing reasonable distance between the tire or strut and the operator. The pressure sensor attaches directly to the pressure supply/relief valve on the tire and/or strut, with necessary electronics contained in the handheld enclosure. A software algorithm ensures high accuracy of the device over the wide temperature range. Using the pressure sensor as a temperature sensor permits measurement of the actual temperature of the pressurized gas. This device can be adapted to create a portable calibration standard that does not require thermal conditioning. This allows accurate pressure measurements without disturbing the gas temperature. In-place calibration can save considerable time and money and is suitable in many process applications throughout industry.

Use of a microwave diagnostics technique to measure the temperature of an axisymmetric ionized gas flow

NASA Astrophysics Data System (ADS)

Tsel'Sov, Iu. G.; Kondrat'ev, A. S.

1990-12-01

A method is developed for determining the temperature of an ionized gas on the basis of electron-density sounding. This technique is used to measure the cross-sectional temperature distribution of an axisymmetric ionized gas flow using microwave diagnostics.

Temperature gradients due to adiabatic plasma expansion in a magnetic nozzle

NASA Astrophysics Data System (ADS)

Sheehan, J. P.; Longmier, B. W.; Bering, E. A.; Olsen, C. S.; Squire, J. P.; Ballenger, M. G.; Carter, M. D.; Cassady, L. D.; Díaz, F. R. Chang; Glover, T. W.; Ilin, A. V.

2014-08-01

A mechanism for ambipolar ion acceleration in a magnetic nozzle is proposed. The plasma is adiabatic (i.e., does not exchange energy with its surroundings) in the diverging section of a magnetic nozzle so any energy lost by the electrons must be transferred to the ions via the electric field. Fluid theory indicates that the change in plasma potential is proportional to the change in average electron energy. These predictions were compared to measurements in the VX-200 experiment which has conditions conducive to ambipolar ion acceleration. A planar Langmuir probe was used to measure the plasma potential, electron density, and electron temperature for a range of mass flow rates and power levels. Axial profiles of those parameters were also measured, showing consistency with the adiabatic ambipolar fluid theory.

Progress on FIR interferometry and Thomson Scattering measurements on HIT-SI3

NASA Astrophysics Data System (ADS)

Everson, Christopher; Jarboe, Thomas; Morgan, Kyle

2017-10-01

Spatially resolved measurements of the electron temperature (Te) and density (ne) will be fundamental in assessing the degree to which HIT-SI3 demonstrates closed magnetic flux and energy confinement. Further, electron temperature measurements have not yet been made on an inductively-driven spheromak. Far infrared (FIR) interferometer and Thomson Scattering (TS) systems have been installed on the HIT-SI3 spheromak. The TS system currently implemented on HIT-SI3 was originally designed for other magnetic confinement experiments, and progress continues toward modifying and optimizing for HIT-SI3 plasmas. Initial results suggest that the electron temperature is of order 10 eV. Plans to modify the TS system to provide more sensitivity and accuracy at low temperatures are presented. The line-integrated ne is measured on one chord by the FIR interferometer, with densities near 5x1019 m-3. Four cylindrical volumes have been added to the HIT-SI3 apparatus to enhance passive pumping. It is hoped that this will allow for more control of the density during the 2 ms discharges. Density measurements from before and after the installation of the passive pumping volumes are presented for comparison.

Development of a spectroscopic technique for simultaneous magnetic field, electron density, and temperature measurements in ICF-relevant plasmas.

PubMed

Dutra, E C; Koch, J A; Presura, R; Angermeier, W A; Darling, T; Haque, S; Mancini, R C; Covington, A M

2016-11-01

Spectroscopic techniques in the visible range are often used in plasma experiments to measure B-field induced Zeeman splitting, electron densities via Stark broadening, and temperatures from Doppler broadening. However, when electron densities and temperatures are sufficiently high, the broadening of the Stark and Doppler components can dominate the emission spectra and obscure the Zeeman component. In this research, we are developing a time-resolved multi-axial technique for measuring the Zeeman, Stark, and Doppler broadened line emission of dense magnetized plasmas for Z-pinch and Dense Plasma Focus (DPF) accelerators. The line emission is used to calculate the electron densities, temperatures, and B-fields. In parallel, we are developing a line-shape modeling code that incorporates the broadening effects due to Stark, Doppler, and Zeeman effects for dense magnetized plasma. This manuscript presents the details of the experimental setup and line shape code, along with the results obtained from an Al iii doublet at the University of Nevada, Reno at Nevada Terawatt Facility. Future tests are planned to further evaluate the technique and modeling on other material wire array, gas puff, and DPF platforms.

Implementation of a multichannel soft x-ray diagnostic for electron temperature measurements in TJ-II high-density plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baiao, D.; Varandas, C.; Medina, F.

2012-10-15

Based on the multi-foil technique, a multichannel soft x-ray diagnostic for electron temperature measurements has been recently implemented in the TJ-II stellarator. The diagnostic system is composed by four photodiodes arrays with beryllium filters of different thickness. An in-vacuum amplifier board is coupled to each array, aiming at preventing induced noise currents. The Thomson scattering and the vacuum ultraviolet survey diagnostics are used for assessing plasma profiles and composition, being the analysis carried out with the radiation code IONEQ. The electron temperature is determined through the different signal-pair ratios with temporal and spatial resolution. The design and preliminary results frommore » the diagnostic are presented.« less

Effects of density gradients and fluctuations at the plasma edge on ECEI measurements at ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Vanovac, B.; Wolfrum, E.; Denk, S. S.; Mink, F.; Laggner, F. M.; Birkenmeier, G.; Willensdorfer, M.; Viezzer, E.; Hoelzl, M.; Freethy, S. J.; Dunne, M. G.; Lessig, A.; Luhmann, N. C., Jr.; the ASDEX Upgrade Team; the EUROfusion MST1 Team

2018-04-01

Electron cyclotron emission imaging (ECEI) provides measurements of electron temperature (T e ) and its fluctuations (δT e ). However, when measuring at the plasma edge, in the steep gradient region, radiation transport effects must be taken into account. It is shown that due to these effects, the scrape-off layer region is not accessible to the ECEI measurements in steady state conditions and that the signal is dominated by the shine-through emission. Transient effects, such as filaments, can change the radiation transport locally, but cannot be distinguished from the shine-through. Local density measurements are essential for the correct interpretation of the electron cyclotron emission, since the density fluctuations influence the temperature measurements at the plasma edge. As an example, a low frequency 8 kHz mode, which causes 10%-15% fluctuations in the signal level of the ECEI, is analysed. The same mode has been measured with the lithium beam emission spectroscopy density diagnostic, and is very well correlated in time with high frequency magnetic fluctuations. With radiation transport modelling of the electron cyclotron radiation in the ECEI geometry, it is shown that the density contributes significantly to the radiation temperature (T rad) and the experimental observations have shown the amplitude modulation in both density and temperature measurements. The poloidal velocity of the low frequency mode measured by the ECEI is 3 km s-1. The calculated velocity of the high frequency mode measured with the magnetic pick-up coils is about 25 km s-1. Velocities are compared with the E × B background flow velocity and possible explanations for the origin of the low frequency mode are discussed.

Probing matter at extreme Gbar pressures at the NIF

DOE PAGES

Kritcher, A. L.; Doeppner, T.; Swift, D.; ...

2013-12-04

Here we describe a platform to measure the material properties, specifically the equation of state and electron temperature, at pressures of 100 Mbar to a Gbar at the National Ignition Facility (NIF). In our experiments we launch spherically convergent shock waves into solid CH, CD, or diamond samples using a hohlraum radiation drive, in an indirect drive laser geometry. X-ray radiography is applied to measure the shock speed and infer the mass density profile, enabling determination of the material pressure and Hugoniot equation of state. X-ray scattering is applied to measure the electron temperature through probing of the electron velocitymore » distribution via Doppler broadening.« less

High-temperature electronics applications in space exploration

NASA Astrophysics Data System (ADS)

Jurgens, R. F.

1982-05-01

One of the most exciting applications of high-temperature electronics is related to the exploration of the planet Venus. On this planet the atmospheric temperatures range from about 170 K at elevations of 100 km to a searing 730 K near the surface. Mechanisms for exploring the atmosphere might include balloons, airplanes, surface landers, and surface-launched probes. Balloons, for example, could fly in the region from 20 (320 C at 22 bars) to 60 km (-20 C at 0.2 bar). Suitable balloon fabrics presently exclude excursions to lower altitudes; however, adequate electronic systems could survive to 325 C. Small airplanes would require more sophisticated electronics for guidance and control. Long life surface landers would most likely be developed first, as these could be used to measure long-term variations in weather. Ranging transponders would be important for ephemeris development, measurement of spin state, and studies of general relativity. Surface temperatures of 460 C and pressures of 90 bars present a challenge to the developers of such instruments. Other space applications for high-temperature electronics include transponders for the surface of Mercury, near solar drag-free orbiters, and deep atmospheric penetrators for Jupiter and Saturn. Each of these has its own particular problems with respect to instrumentation adequate to meet the desired scientific goals. This paper is primarily concerned with defining possible mission applications, the required electronic systems, and the approaches that are currently being studied for their development.

High-temperature electronics applications in space exploration

NASA Technical Reports Server (NTRS)

Jurgens, R. F.

1982-01-01

One of the most exciting applications of high-temperature electronics is related to the exploration of the planet Venus. On this planet the atmospheric temperatures range from about 170 K at elevations of 100 km to a searing 730 K near the surface. Mechanisms for exploring the atmosphere might include balloons, airplanes, surface landers, and surface-launched probes. Balloons, for example, could fly in the region from 20 (320 C at 22 bars) to 60 km (-20 C at 0.2 bar). Suitable balloon fabrics presently exclude excursions to lower altitudes; however, adequate electronic systems could survive to 325 C. Small airplanes would require more sophisticated electronics for guidance and control. Long life surface landers would most likely be developed first, as these could be used to measure long-term variations in weather. Ranging transponders would be important for ephemeris development, measurement of spin state, and studies of general relativity. Surface temperatures of 460 C and pressures of 90 bars present a challenge to the developers of such instruments. Other space applications for high-temperature electronics include transponders for the surface of Mercury, near solar drag-free orbiters, and deep atmospheric penetrators for Jupiter and Saturn. Each of these has its own particular problems with respect to instrumentation adequate to meet the desired scientific goals. This paper is primarily concerned with defining possible mission applications, the required electronic systems, and the approaches that are currently being studied for their development.

Electron temperature and density probe for small aeronomy satellites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oyama, K.-I.; Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan, Taiwan; International Center for Space Weather Study and education, Kyushu University, Fukuoka

2015-08-15

A compact and low power consumption instrument for measuring the electron density and temperature in the ionosphere has been developed by modifying the previously developed Electron Temperature Probe (ETP). A circuit block which controls frequency of the sinusoidal signal is added to the ETP so that the instrument can measure both T{sub e} in low frequency mode and N{sub e} in high frequency mode from the floating potential shift of the electrode. The floating potential shift shows a minimum at the upper hybrid resonance frequency (f{sub UHR}). The instrument which is named “TeNeP” can be used for tiny satellites whichmore » do not have enough conductive surface area for conventional DC Langmuir probe measurements. The instrument also eliminates the serious problems associated with the contamination of satellite surface as well as the sensor electrode.« less

Parametric dependence of ion temperature and electron density in the SUMMA hot-ion plasma using laser light scattering and emission spectroscopy

NASA Technical Reports Server (NTRS)

Snyder, A.; Patch, R. W.; Lauver, M. R.

1980-01-01

Hot-ion plasma experiments were conducted in the NASA Lewis SUMMA facility. A steady-state modified Penning discharge was formed by applying a radially inward dc electric field of several kilovolts near the magnetic mirror maxima. Results are reported for a hydrogen plasma covering a wide range in midplane magnetic flux densities from 0.5 to 3.37 T. Input power greater than 45 kW was obtained with water-cooled cathodes. Steady-state plasmas with ion kinetic temperatures from 18 to 830 eV were produced and measured spectroscopically. These ion temperatures were correlated with current, voltage, and magnetic flux density as the independent variables. Electron density measurements were made using an unusually sensitive Thomson scattering apparatus. The measured electron densities range from 2.1 x 10 to the 11th to 6.8 x 10 to the 12th per cu cm.

Evaluating Uncertainties in Coronal Electron Temperature and Radial Speed Measurements Using a Simulation of the Bastille Day Eruption

NASA Astrophysics Data System (ADS)

Reginald, Nelson; St. Cyr, Orville; Davila, Joseph; Rastaetter, Lutz; Török, Tibor

2018-05-01

Obtaining reliable measurements of plasma parameters in the Sun's corona remains an important challenge for solar physics. We previously presented a method for producing maps of electron temperature and speed of the solar corona using K-corona brightness measurements made through four color filters in visible light, which were tested for their accuracies using models of a structured, yet steady corona. In this article we test the same technique using a coronal model of the Bastille Day (14 July 2000) coronal mass ejection, which also contains quiet areas and streamers. We use the coronal electron density, temperature, and flow speed contained in the model to determine two K-coronal brightness ratios at (410.3, 390.0 nm) and (423.3, 398.7 nm) along more than 4000 lines of sight. Now assuming that for real observations, the only information we have for each line of sight are these two K-coronal brightness ratios, we use a spherically symmetric model of the corona that contains no structures to interpret these two ratios for electron temperature and speed. We then compare the interpreted (or measured) values for each line of sight with the true values from the model at the plane of the sky for that same line of sight to determine the magnitude of the errors. We show that the measured values closely match the true values in quiet areas. However, in locations of coronal structures, the measured values are predictably underestimated or overestimated compared to the true values, but can nevertheless be used to determine the positions of the structures with respect to the plane of the sky, in front or behind. Based on our results, we propose that future white-light coronagraphs be equipped to image the corona using four color filters in order to routinely create coronal maps of electron density, temperature, and flow speed.

Probing the relationship between magnetic and temperature structures with soft x-rays on the Madison Symmetric Torus

NASA Astrophysics Data System (ADS)

McGarry, Meghan B.

An innovative new soft x-ray (SXR) diagnostic has been developed for the Madison Symmetric Torus that provides measurements of tomographic emissivity and electron temperature (Te) via the double-foil technique. Two measurements of electron temperature from SXR emission are available, one from the ratio of the emissivities through thin and thick filters as mapped onto magnetic flux surfaces, and the other directly from the ratio of two foils sharing a single line-of-sight. The SXR measurements have been benchmarked against Thomson Scattering electron temperature during high current, improved confinement discharges, and show excellent agreement. The SXR diagnostic has been used to investigate the source of emissive structures seen during high-current improved confinement discharges. Although the emissivity structures are correlated to the magnetic configuration of the discharges, direct-brightness Te measurements do not typically show a clear Te structure, indicating a general upper limit of ˜ 15--20% on any possible localized increase in Te. In most shots, the flux-surface reconstructed Te shows no indication of Te structure. However, in one discharge with a very large tearing mode amplitude (15 Gauss), measurements and modeling indicate that the structure has a localized increase of 20-180 eV in Te. The structure cannot be explained by a localized enhancement of electron density. A second case study with a multiple-helicity magnetic spectrum indicates that a ring of enhanced SXR emission at 0.4 normalized radius is caused by an impurity accumulation of up to 58% that of the core region. For the first time, the SXR diagnostic has also been combined with Al11+ impurity measurements to normalize the aluminum contribution to the SXR emission spectrum and demonstrate that the filter thicknesses used for the diagnostic do not pass aluminum line radiation. The new SXR Te and tomography diagnostic will continue to provide insight into the relationship between magnetic structures and electron temperature in improved confinement plasmas.

Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: off-resonant and resonant cases.

PubMed

Cortázar, O D; Megía-Macías, A; Vizcaíno-de-Julián, A

2013-09-01

Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

Multiple Fermi pockets revealed by Shubnikov-de Haas oscillations in WTe2

NASA Astrophysics Data System (ADS)

Xiang, Fei-Xiang; Veldhorst, Menno; Dou, Shi-Xue; Wang, Xiao-Lin

2015-11-01

The recently discovered non-saturating and parabolic magnetoresistance and the pressure-induced superconductivity at low temperature in WTe2 imply its rich electronic structure and possible practical applications. Here we use magnetotransport measurements to investigate the electronic structure of WTe2 single crystals. A non-saturating and parabolic magnetoresistance is observed from low temperature to high temperature up to 200 K with magnetic fields up to 8 T. Shubnikov-de Haas (SdH) oscillations with beating patterns are observed, the fast Fourier transform of which reveals three oscillation frequencies, corresponding to three pairs of Fermi pockets with comparable effective masses, m* ∼ 0.31~me . By fitting the Hall resistivity, we infer that they can be attributed to one pair of electron pockets and two pairs of hole pockets, together with nearly perfect compensation of the electron-hole carrier concentration. These magnetotransport measurements reveal the complex electronic structure in WTe2, explaining the non-saturating magnetoresistance.

Temperature Dependence of Dissociative Electron Attachment to Halogenated Hydrocarbons

NASA Astrophysics Data System (ADS)

Wang, Yicheng; Christophorou, Loucas G.

1996-10-01

Most of the gas mixtures currently in use for plasma processing of semiconductors involve halogenated hydrocarbons such as the strongly electronegative gases CCl4 and CFCl_3, the weakly electronegative gas CF_2Cl2 and the very weakly electronegative gases CHF3 and CF_4. Many dissociation processes are known to occur for these molecules. One of these dissociation reactions which is particularly effective for the strongly electronegative hydrocarbons is dissociative electron attachment. Even for weakly electron attaching gases, molecular dissociation via dissociative electron attachment at low energies can be an efficient dissociation process if the gas temperature is higher than ambient. Dissociative electron attachment is known to increase with increasing temperature above room temperature for many such compounds. In this paper, we report our measurements on the increases of the total electron attachment rate constant for CF_2Cl2 with increasing gas temperature from room temperature to about 600 K. -Research sponsored in part by the U.S. Air Force Wright Laboratory under contract F33615-96-C-2600 with the University of Tennessee. Also, Department of Physics, The University of Tennessee, Knoxville, TN.

Laboratory Measurements of the Dielectronic Recombination Satellite Transitions of He-Like FE XXV and H-Like FE XXVI

NASA Technical Reports Server (NTRS)

Gu, M. F.; Beiersdorfer, P.; Brown, G. V.; Graf, A.; Kelley, R. I.; Kilbourne, C. A.; Porter, F. S.; Kahn, S. M,

2012-01-01

We present laboratory spectra of dielectronic recombination (DR) satellite transitions attached to the He-like and H-like iron resonance lines obtained with the NASA Goddard Space Flight Center X-ray calorimeter and produced by a thermal plasma simu1ation technique on the EBIT-I electron beam ion trap at the Lawrence Livermore National Laboratory. We demonstrate that the calorimeter has sufficient spectral resolution in the 6-9 keV range to provide reliable measurements not only of standard DR satellite to resonance line intensities but also of DR satellite to DR satellite ratios that can be used to diagnose nonthermal electron distributions. Electron temperatures derived from the measured line intensities are consistent with the temperature of the simulated plasma. Temperature measurements based on DR satellite transitions have significant advantages over those based on collisional ionization equilibrium or continuum shape. Thus, successful demonstration of this method with the X-ray calorimeter is an important step fur its application in X-ray astronomy.

Plasma parameters in a multidipole plasma system

NASA Astrophysics Data System (ADS)

Ruscanu, D.; Anita, V.; Popa, G.

Plasma potential and electron number densities and electron temperatures under bi-Maxwellian approximation for electron distribution function of the multidipole argon plasma source system were measured for a gas pressure ranging between 10-4 and 10-3 mbar and an anode-cathode voltage ranging between 40 and 120 V but a constant discharge current intensity. The first group, as ultimate or cold electrons and main electron plasma population, results by trapping of the slow electrons produced by ionisation process due to primary-neutral collisions. The trapping process is produced by potential well due to positive plasma potential with respect to the anode so that electron temperature of the ultimate electrons does not depend on both the gas pressure and discharge voltage. The second group, as secondary or hot electrons, results as degrading process of the primaries and their number density increases while their temperature decreases with the increase of both the gas pressure and discharge voltage.

Measurement of collective excitations in VO 2 by resonant inelastic x-ray scattering

DOE PAGES

He, Haowei; Gray, A. X.; Granitzka, P.; ...

2016-10-15

Vanadium dioxide is of broad interest as a spin-1/2 electron system that realizes a metal-insulator transition near room temperature, due to a combination of strongly correlated and itinerant electron physics. Here, resonant inelastic x-ray scattering is used to measure the excitation spectrum of charge and spin degrees of freedom at the vanadium L edge under different polarization and temperature conditions, revealing excitations that differ greatly from those seen in optical measurements. Furthermore, these spectra encode the evolution of short-range energetics across the metal-insulator transition, including the low-temperature appearance of a strong candidate for the singlet-triplet excitation of a vanadium dimer.

MAVEN Observations of Dayside Peak Electron Densities in the Ionosphere of Mars

NASA Astrophysics Data System (ADS)

Vogt, M. F.; Withers, P.; Andersson, L.; Mahaffy, P. R.; Benna, M.; Elrod, M. K.; Connerney, J. E. P.; Espley, J. R.; Eparvier, F. G.; Jakosky, B. M.

2016-12-01

The peak electron density in the dayside Martian ionosphere is a valuable diagnostic of the state of the ionosphere. Its dependence on factors like the solar zenith angle, ionizing solar irradiance, neutral scale height, and electron temperature has been well studied. The MAVEN spacecraft's September 2015 "deep dip" orbits, in which the orbital periapsis is lowered to 120 km, provided our first opportunity since Viking to sample in situ a complete dayside electron density profiles including the main peak, and the first observations with contemporaneous comprehensive measurements of the local plasma and magnetic field properties. We have analyzed the peak electron density measurements from the MAVEN deep dip orbits and will discuss their variability with various ionospheric properties, including the proximity to regions of large crustal magnetic fields, and external drivers. We will also present observations of the electron temperature and atmospheric neutral and ion composition at the altitude of the peak electron density.

Consequences of Part Temperature Variability in Electron Beam Melting of Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Fisher, Brian A.; Mireles, Jorge; Ridwan, Shakerur; Wicker, Ryan B.; Beuth, Jack

2017-12-01

To facilitate adoption of Ti-6Al-4V (Ti64) parts produced via additive manufacturing (AM), the ability to ensure part quality is critical. Measuring temperatures is an important component of part quality monitoring in all direct metal AM processes. In this work, surface temperatures were monitored using a custom infrared camera system attached to an Arcam electron beam melting (EBM®) machine. These temperatures were analyzed to understand their possible effect on solidification microstructure based on solidification cooling rates extracted from finite element simulations. Complicated thermal histories were seen during part builds, and temperature changes occurring during typical Ti64 builds may be large enough to affect solidification microstructure. There is, however, enough time between fusion of individual layers for spatial temperature variations (i.e., hot spots) to dissipate. This means that an effective thermal control strategy for EBM® can be based on average measured surface temperatures, ignoring temperature variability.

Molybdenum electron impact width parameter measurement by laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Sternberg, E. M. A.; Rodrigues, N. A. S.; Amorim, J.

2016-01-01

In this work, we suggest a method for electron impact width parameter calculation based on Stark broadening of emission lines of a laser-ablated plasma plume. First, electron density and temperature must be evaluated by means of the Saha-Boltzmann plot method for neutral and ionized species of the plasma. The method was applied for laser-ablated molybdenum plasma plume. For molybdenum plasma electron temperature, which varies around 10,000 K, and electron density, which reaches values around 1018 cm-3, and considering that total measured line broadening was due experimental and Stark broadening mainly, electron impact width parameter of molybdenum emission lines was determined as (0.01 ± 0.02) nm. Intending to validate the presented method, it was analyzed the laser-ablated aluminum plasma plume and the obtained results were in agreement with the predicted on the literature.

Characterization of the fast electrons distribution produced in a high intensity laser target interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westover, B.; Lawrence Livermore National Laboratory, Livermore, California 94550; Chen, C. D.

2014-03-15

Experiments on the Titan laser (∼150 J, 0.7 ps, 2 × 10{sup 20} W cm{sup −2}) at the Lawrence Livermore National Laboratory were carried out in order to study the properties of fast electrons produced by high-intensity, short pulse laser interacting with matter under conditions relevant to Fast Ignition. Bremsstrahlung x-rays produced by these fast electrons were measured by a set of compact filter-stack based x-ray detectors placed at three angles with respect to the target. The measured bremsstrahlung signal allows a characterization of the fast electron beam spectrum, conversion efficiency of laser energy into fast electron kinetic energy and angular distribution. A Monte Carlo codemore » Integrated Tiger Series was used to model the bremsstrahlung signal and infer a laser to fast electron conversion efficiency of 30%, an electron slope temperature of about 2.2 MeV, and a mean divergence angle of 39°. Simulations were also performed with the hybrid transport code ZUMA which includes fields in the target. In this case, a conversion efficiency of laser energy to fast electron energy of 34% and a slope temperature between 1.5 MeV and 4 MeV depending on the angle between the target normal direction and the measuring spectrometer are found. The observed temperature of the bremsstrahlung spectrum, and therefore the inferred electron spectrum are found to be angle dependent.« less

Two-Dimensional Spatial Imaging of Charge Transport in Germanium Crystals at Cryogenic Temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moffatt, Robert

2016-03-01

In this dissertation, I describe a novel apparatus for studying the transport of charge in semiconductors at cryogenic temperatures. The motivation to conduct this experiment originated from an asymmetry observed between the behavior of electrons and holes in the germanium detector crystals used by the Cryogenic Dark Matter Search (CDMS). This asymmetry is a consequence of the anisotropic propagation of electrons in germanium at cryogenic temperatures. To better model our detectors, we incorporated this effect into our Monte Carlo simulations of charge transport. The purpose of the experiment described in this dissertation is to test those models in detail. Ourmore » measurements have allowed us to discover a shortcoming in our most recent Monte Carlo simulations of electrons in germanium. This discovery would not have been possible without the measurement of the full, two-dimensional charge distribution, which our experimental apparatus has allowed for the first time at cryogenic temperatures.« less

Langmuir probe measurements in a time-fluctuating-highly ionized non-equilibrium cutting arc: analysis of the electron retarding part of the time-averaged current-voltage characteristic of the probe.

PubMed

Prevosto, L; Kelly, H; Mancinelli, B

2013-12-01

This work describes the application of Langmuir probe diagnostics to the measurement of the electron temperature in a time-fluctuating-highly ionized, non-equilibrium cutting arc. The electron retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the electron current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged electron temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged electron temperature. In particular, an averaged electron temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such electron temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core.

Room-temperature electron spin relaxation of nitroxides immobilized in trehalose: Effect of substituents adjacent to NO-group

NASA Astrophysics Data System (ADS)

Kuzhelev, Andrey A.; Strizhakov, Rodion K.; Krumkacheva, Olesya A.; Polienko, Yuliya F.; Morozov, Denis A.; Shevelev, Georgiy Yu.; Pyshnyi, Dmitrii V.; Kirilyuk, Igor A.; Fedin, Matvey V.; Bagryanskaya, Elena G.

2016-05-01

Trehalose has been recently promoted as efficient immobilizer of biomolecules for room-temperature EPR studies, including distance measurements between attached nitroxide spin labels. Generally, the structure of nitroxide influences the electron spin relaxation times, being crucial parameters for room-temperature pulse EPR measurements. Therefore, in this work we investigated a series of nitroxides with different substituents adjacent to NO-moiety including spirocyclohexane, spirocyclopentane, tetraethyl and tetramethyl groups. Electron spin relaxation times (T1, Tm) of these radicals immobilized in trehalose were measured at room temperature at X- and Q-bands (9/34 GHz). In addition, a comparison was made with the corresponding relaxation times in nitroxide-labeled DNA immobilized in trehalose. In all cases phase memory times Tm were close to 700 ns and did not essentially depend on structure of substituents. Comparison of temperature dependences of Tm at T = 80-300 K shows that the benefit of spirocyclohexane substituents well-known at medium temperatures (∼100-180 K) becomes negligible at 300 K. Therefore, unless there are specific interactions between spin labels and biomolecules, the room-temperature value of Tm in trehalose is weakly dependent on the structure of substituents adjacent to NO-moiety of nitroxide. The issues of specific interactions and stability of nitroxide labels in biological media might be more important for room temperature pulsed dipolar EPR than differences in intrinsic spin relaxation of radicals.

Note: Fiber optic transport probe for Hall measurements under light and magnetic field at low temperatures: Case study of a two dimensional electron gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhadauria, P. P. S.; Gupta, Anurag; Kumar, Pramod

2015-05-15

A fiber optic based probe is designed and developed for electrical transport measurements in presence of quasi-monochromatic (360–800 nm) light, varying temperature (T = 1.8–300 K), and magnetic field (B = 0–7 T). The probe is tested for the resistivity and Hall measurements performed on a LaAlO{sub 3}–SrTiO{sub 3} heterointerface system with a conducting two dimensional electron gas.

Analysis of coronal H I Lyman alpha measurements from a rocket flight on 1979 April 13

NASA Technical Reports Server (NTRS)

Withbroe, G. L.; Kohl, J. L.; Weiser, H.; Noci, G.; Munro, R. H.

1982-01-01

It is noted that measurements of the profiles of resonantly scattered hydrogen Lyman-alpha coronal radiation have been used in determining hydrogen kinetic temperatures from 1.5 to 4 solar radii from sun center in a quiet region of the corona. Proton temperatures derived using the line widths decrease with height from 2.6 x 10 to the 6th K at 1.5 solar radii to 1.2 x 10 to the 6th K at 4 solar radii. These measurements, together with temperatures for lower heights determined from earlier Skylab and eclipse data, suggest that there is a maximum in the quiet coronal proton temperature at about 1.5 solar radii. Comparison of measured Lyman-alpha intensities with those calculated using a representative model for the radial variation of the coronal electron density yields information on the magnitude of the electron temperature gradient and suggests that the solar wind flow was subsonic for distances less than 4 solar radii.

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Haowei; Gray, A. X.; Granitzka, P.

Vanadium dioxide is of broad interest as a spin-1/2 electron system that realizes a metal-insulator transition near room temperature, due to a combination of strongly correlated and itinerant electron physics. Here, resonant inelastic x-ray scattering is used to measure the excitation spectrum of charge and spin degrees of freedom at the vanadium L edge under different polarization and temperature conditions, revealing excitations that differ greatly from those seen in optical measurements. Furthermore, these spectra encode the evolution of short-range energetics across the metal-insulator transition, including the low-temperature appearance of a strong candidate for the singlet-triplet excitation of a vanadium dimer.

Carrier concentration dependence of donor activation energy in n-type GaN epilayers grown on Si (1 1 1) by plasma-assisted MBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Mahesh; Central Research Laboratory, Bharat Electronics, Bangalore 560 013; Bhat, Thirumaleshwara N.

Highlights: ► The n-type GaN layers were grown by plasma-assisted molecular beam epitaxy. ► The optical characteristics of a donor level in Si-doped GaN were studied. ► Activation energy of a Si-related donor was estimated from temperature dependent PL measurements. ► PL peak positions, FWHM of PL and activation energies are found to be proportional to the cube root of carrier density. ► The involvement of donor levels is supported by the temperature-dependent electron concentration measurements. -- Abstract: The n-type GaN layers were grown by plasma-assisted MBE and either intentionally doped with Si or unintentionally doped. The optical characteristics ofmore » a donor level in Si-doped, GaN were studied in terms of photoluminescence (PL) spectroscopy as a function of electron concentration. Temperature dependent PL measurements allowed us to estimate the activation energy of a Si-related donor from temperature-induced decay of PL intensity. PL peak positions, full width at half maximum of PL and activation energies are found to be proportional to the cube root of carrier density. The involvement of donor levels is supported by the temperature-dependent electron concentration measurements.« less

Headset Bluetooth and cell phone based continuous central body temperature measurement system.

PubMed

Sanches, J Miguel; Pereira, Bruno; Paiva, Teresa

2010-01-01

The accurate measure of the central temperature is a very important physiologic indicator in several clinical applications, namely, in the characterization and diagnosis of sleep disorders. In this paper a simple system is described to continuously measure the body temperature at the ear. An electronic temperature sensor is coupled to the microphone of a common commercial auricular Bluetooth device that sends the temperature measurements to a mobile phone to which is paired. The measurements are stored at the mobile phone and periodically sent to a medical facility by email or SMS (short messaging service).

ITER ECE Diagnostic: Design Progress of IN-DA and the diagnostic role for Physics

NASA Astrophysics Data System (ADS)

Pandya, H. K. B.; Kumar, Ravinder; Danani, S.; Shrishail, P.; Thomas, Sajal; Kumar, Vinay; Taylor, G.; Khodak, A.; Rowan, W. L.; Houshmandyar, S.; Udintsev, V. S.; Casal, N.; Walsh, M. J.

2017-04-01

The ECE Diagnostic system in ITER will be used for measuring the electron temperature profile evolution, electron temperature fluctuations, the runaway electron spectrum, and the radiated power in the electron cyclotron frequency range (70-1000 GHz), These measurements will be used for advanced real time plasma control (e.g. steering the electron cyclotron heating beams), and physics studies. The scope of the Indian Domestic Agency (IN-DA) is to design and develop the polarizer splitter units; the broadband (70 to 1000 GHz) transmission lines; a high temperature calibration source in the Diagnostics Hall; two Michelson Interferometers (70 to 1000 GHz) and a 122-230 GHz radiometer. The remainder of the ITER ECE diagnostic system is the responsibility of the US domestic agency and the ITER Organization (IO). The design needs to conform to the ITER Organization’s strict requirements for reliability, availability, maintainability and inspect-ability. Progress in the design and development of various subsystems and components considering various engineering challenges and solutions will be discussed in this paper. This paper will also highlight how various ECE measurements can enhance understanding of plasma physics in ITER.

Spatially resolved density and ionization measurements of shocked foams using x-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J.; Keiter, P. A.; Montgomery, D. S.

2016-09-22

We present experiments at the Trident laser facility demonstrating the use of x-ray fluorescence (XRF) to simultaneously measure density, ionization state populations, and electron temperature in shocked foams. An imaging x-ray spectrometer was used to obtain spatially-resolved measurements of Ti K-more » $$\\alpha$$ emission. Density profiles were measured from K-$$\\alpha$$ intensity. Ti ionization state distributions and electron temperatures were inferred by fitting K-$$\\alpha$$ spectra to spectra from CRETIN simulations. This study shows that XRF provides a powerful tool to complement other diagnostics to make equation of state measurements of shocked materials containing a suitable tracer element.« less

Short-interval multi-laser Thomson scattering measurements of hydrogen pellet ablation in LHD.

PubMed

Yasuhara, R; Sakamoto, R; Yamada, I; Motojima, G; Hayashi, H

2014-11-01

Thomson scattering forms an important aspect of measuring the electron density and temperature profiles of plasmas. In this study, we demonstrate Thomson scattering measurements obtained over a short interval (<1 ms) by using an event triggering system with a multi-laser configuration. We attempt to use our system to obtain the electron temperature and density profiles before and immediately after pellet injection into the large helical device. The obtained profiles exhibit dramatic changes after pellet injection as per our shot-by-shot measurements. We believe that this measurement technique will contribute towards a better understanding of the physics of the pellet deposition.

Short-interval multi-laser Thomson scattering measurements of hydrogen pellet ablation in LHD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yasuhara, R., E-mail: yasuhara@nifs.ac.jp; Sakamoto, R.; Yamada, I.

2014-11-15

Thomson scattering forms an important aspect of measuring the electron density and temperature profiles of plasmas. In this study, we demonstrate Thomson scattering measurements obtained over a short interval (<1 ms) by using an event triggering system with a multi-laser configuration. We attempt to use our system to obtain the electron temperature and density profiles before and immediately after pellet injection into the large helical device. The obtained profiles exhibit dramatic changes after pellet injection as per our shot-by-shot measurements. We believe that this measurement technique will contribute towards a better understanding of the physics of the pellet deposition.

Multi-environment Nanocalorimeter with Electrical Contacts for Use in the Scanning Electron Microscope.

PubMed

Yi, Feng; Stevanovic, Ana; Osborn, William A; Kolmakov, A; LaVan, David A

2017-11-01

We have developed a versatile nanocalorimeter sensor which allows imaging and electrical measurements of samples under different gaseous environments using the scanning electron microscope (SEM) and can simultaneously measure the sample temperature and associated heat of reaction. This new sensor consists of four independent heating/sensing elements for nanocalorimetry and eight electrodes for electrical measurements, all mounted on a 50 nm thick, 250 μm × 250 μm suspended silicon nitride membrane. This membrane is highly electron transparent and mechanically robust enabling in situ SEM observation under realistic temperatures, environmental conditions and pressures up to one atmosphere. To demonstrate this new capability, we report here on 1) in situ SEM-nanocalorimetry study of melting and solidification of polyethylene oxide, 2) the temperature dependence of conductivity of a nanowire; 3) the electron beam induced current measurements (EBID) of a nanowire in vacuum and air. Furthermore, the sensor is easily adaptable to operate in liquid environment and is compatible with most existing SEM. This versatile platform couples nanocalorimetry with in situ SEM imaging under various gaseous and liquid environments and is applicable to materials research, nanotechnology, energy, catalysis and biomedical applications.

An investigation into the role of metastable states on excited populations of weakly ionized argon plasmas, with applications for optical diagnostics

NASA Astrophysics Data System (ADS)

Arnold, Nicholas; Loch, Stuart; Ballance, Connor; Thomas, Ed

2017-10-01

Low temperature plasmas (Te < 10 eV) are ubiquitous in the medical, industrial, basic, and dusty plasma communities, and offer an opportunity for researchers to gain a better understanding of atomic processes in plasmas. Here, we report on a new atomic dataset for neutral and low charge states of argon, from which rate coefficients and cross-sections for the electron-impact excitation of neutral argon are determined. We benchmark by comparing with electron impact excitation cross-sections available in the literature, with very good agreement. We have used the Atomic Data and Analysis Structure (ADAS) code suite to calculate a level-resolved, generalized collisional-radiative (GCR) model for line emission in low temperature argon plasmas. By combining our theoretical model with experimental electron temperature, density, and spectral measurements from the Auburn Linear eXperiment for Instability Studies (ALEXIS), we have developed diagnostic techniques to measure metastable fraction, electron temperature, and electron density. In the future we hope to refine our methods, and extend our model to plasmas other than ALEXIS. Supported by the U.S. Department of Energy. Grant Number: DE-FG02-00ER54476.

Ion Temperature Measurements in an electron beam ion trap (EBIT)

NASA Astrophysics Data System (ADS)

Beiersdorfer, P.; Decaux, V.; Widmann, K.

1997-11-01

An electron beam ion trap consists of a Penning-type cylindrical trap traversed by a high-energy (<= 200 keV), high-density (Ne <= 10^13 cm-3) electron beam. Ions are trapped by the space charge potential of the electron beam, a static potential on the end electrodes, and a 3-T axial magnetic field [1]. The ions are heated by the electron beam and leave the trap once their kinetic energy suffices to overcome the potential barriers. Using high-resolution x-ray spectroscopy, we have made systematic measurements of the temperature of Ti^20+ and Cs^45+ ions in the trap [2]. The dependence of the ion temperature on operating parameters, such as trapping potential, beam current, and neutral gas pressure, will be presented. Temperatures as low as 15.4 ± 4.4 eV and as high as 2 keV were observed. *Work performed under the auspices of the U.S.D.o.E. by Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. [1] M. Levine et al., Phys. Scripta T22, 157 (1989). [2]P. Beiersdorfer et al., PRL 77, 5356 (1996); P. Beiersdorfer, in AIP Conf. Proc. No. 389, p. 121 (1997).

Modeling and design of radiative hydrodynamic experiments with X-ray Thomson Scattering measurements on NIF

NASA Astrophysics Data System (ADS)

Ma, K. H.; Lefevre, H. J.; Belancourt, P. X.; MacDonald, M. J.; Doeppner, T.; Keiter, P. A.; Kuranz, C. C.; Johnsen, E.

2017-10-01

Recent experiments at the National Ignition Facility studied the effect of radiation on shock-driven hydrodynamic instability growth. X-ray radiography images from these experiments indicate that perturbation growth is lower in highly radiative shocks compared to shocks with negligible radiation flux. The reduction in instability growth is attributed to ablation from higher temperatures in the foam for highly radiative shocks. The proposed design implements the X-ray Thomson Scattering (XRTS) technique in the radiative shock tube platform to measure electron temperatures and densities in the shocked foam. We model these experiments with CRASH, an Eulerian radiation hydrodynamics code with block-adaptive mesh refinement, multi-group radiation transport and electron heat conduction. Simulations are presented with SiO2 and carbon foams for both the high temperature, radiative shock and the low-temperature, hydrodynamic shock cases. Calculations from CRASH give estimations for shock speed, electron temperature, effective ionization, and other quantities necessary for designing the XRTS diagnostic measurement. This work is funded by the LLNL under subcontract B614207, and was performed under the auspices of the U.S. DOE by LLNL under Contract No. DE-AC52-07NA27344.

Coherent energy scale revealed by ultrafast dynamics of UX3 (X = Al, Sn, Ga) single crystals

NASA Astrophysics Data System (ADS)

Nair, Saritha K.; Zhu, J.-X.; Sarrao, J. L.; Taylor, A. J.; Chia, Elbert E. M.

2012-09-01

The temperature dependence of relaxation dynamics of UX3 (X = Al, Ga, Sn) compounds is studied using the time-resolved pump-probe technique in reflectance geometry. For UGa3, our data are consistent with the formation of a spin density wave gap as evidenced from the quasidivergence of the relaxation time τ near the Néel temperature TN. For UAl3 and USn3, the relaxation dynamics shows a change from single-exponential to two-exponential behavior below a particular temperature, suggestive of coherence formation of the 5f electrons with the conduction band electrons. This particular temperature can be attributed to the spin fluctuation temperature Tsf, a measure of the strength of Kondo coherence. Our Tsf is consistent with other data such as resistivity and susceptibility measurements. The temperature dependence of the relaxation amplitude and time of UAl3 and USn3 were also fitted by the Rothwarf-Taylor model. Our results show that ultrafast optical spectroscopy is sensitive to c-f Kondo hybridization in the f-electron systems.

NMR Evidences of the Coupling between Conduction Electrons and Molecular Degrees of Freedom in the Exotic Member of the Bechgaard Salt (TMTSF)2FSO3

NASA Astrophysics Data System (ADS)

Satsukawa, Hidetaka; Yajima, Akio; Hiraki, Ko-ichi; Takahashi, Toshihiro; Kang, Haeyong; Jo, Younjung; Kang, Woun; Chung, Ok-Hee

2016-12-01

We performed 77Se- and 19F-NMR measurements on single crystals of (TMTSF)2FSO3 to characterize the electronic structures of different phases in the temperature-pressure phase diagram, determined by precise transport measurements [Jo et al., Phys. Rev. B 67, 014516 (2003)]. We claim that such varieties of electronic states in the refined phase diagram are caused by strong couplings of the conduction electrons with FSO3 anions, especially with the permanent electric dipoles on the anions. We suggest that as temperature decreases, the FSO3 anions form orientational ordering through two steps; first, only the tetrahedrons form an orientational order leaving the orientations of the electronic dipoles in random (transition I); then the dipoles form a perfect orientational order at a lower temperature (transition II). In the intermediate temperature range between transitions I and II, we found an appreciable enhancement of homogeneous and inhomogeneous widths of the 77Se-NMR spectrum. From the analysis of the angular dependence of the linewidth, we attributed these anomalies to the intramolecular charge disproportionation or imbalance and its slow dynamics caused by the coupling with the permanent electric dipole of the anion. Results of 19F-NMR relaxation and lineshape measurements support this picture very well. Electronic structures at higher pressures up to 1.25 GPa are discussed on the basis of the results of the 77Se- and 19F-NMR measurements.

Length-dependent thermal transport in one-dimensional self-assembly of planar π-conjugated molecules

NASA Astrophysics Data System (ADS)

Tang, Hao; Xiong, Yucheng; Zu, Fengshuo; Zhao, Yang; Wang, Xiaomeng; Fu, Qiang; Jie, Jiansheng; Yang, Juekuan; Xu, Dongyan

2016-06-01

This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport. Interestingly, a gradual transition to the linear length dependence is observed with the increase of the lateral dimensions of CuPc nanoribbons. The measured thermal resistance of single crystalline CuPc nanoribbons shows an increasing trend with temperature. However, the trend of temperature dependence of thermal resistance is reversed after electron irradiation, i.e., decreasing with temperature, indicating that the single crystalline CuPc nanoribbons become `amorphous'. Similar behavior is also observed for PTCDI nanoribbons after electron irradiation, proving that the electron beam can induce amorphization of single crystalline self-assembled nanostructures of planar π-conjugated molecules. The measured thermal resistance of the `amorphous' CuPc nanoribbon demonstrates a roughly linear dependence on the nanoribbon length, suggesting that normal diffusion dominates thermal transport.This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport. Interestingly, a gradual transition to the linear length dependence is observed with the increase of the lateral dimensions of CuPc nanoribbons. The measured thermal resistance of single crystalline CuPc nanoribbons shows an increasing trend with temperature. However, the trend of temperature dependence of thermal resistance is reversed after electron irradiation, i.e., decreasing with temperature, indicating that the single crystalline CuPc nanoribbons become `amorphous'. Similar behavior is also observed for PTCDI nanoribbons after electron irradiation, proving that the electron beam can induce amorphization of single crystalline self-assembled nanostructures of planar π-conjugated molecules. The measured thermal resistance of the `amorphous' CuPc nanoribbon demonstrates a roughly linear dependence on the nanoribbon length, suggesting that normal diffusion dominates thermal transport. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09043a

A flow cell for measuring X-ray Compton scattering of liquid at temperatures up to 623 K and pressures up to 20 MPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, Takumi, E-mail: onot@scf.che.tohoku.ac.jp; Watanabe, Masaru; Sato, Yoshiyuki

2016-08-15

A flow-type cell was developed for measuring Compton scattering spectra of heat-sensitive aqueous solution. Compton scattering spectra of water and ethanol were measured in the region from ambient conditions to 623 K and 20 MPa. Compton profiles derived from measurement with the flow-type cell were comparable with those in the literature. Results obtained from the flow-type cell showed that delocalization of electronic charge density of water and ethanol at high temperatures occurred. Delocalization of the electronic charge density of ethanol was greater than that of water at high temperature, which is consistent with the prior works that use proton NMRmore » chemical shifts to describe hydrogen bonding.« less

A Statistical Study of Eiscat Electron and Ion Temperature Measurements In The E-region

NASA Astrophysics Data System (ADS)

Hussey, G.; Haldoupis, C.; Schlegel, K.; Bösinger, T.

Motivated by the large EISCAT data base, which covers over 15 years of common programme operation, and previous statistical work with EISCAT data (e.g., C. Hal- doupis, K. Schlegel, and G. Hussey, Auroral E-region electron density gradients mea- sured with EISCAT, Ann. Geopshysicae, 18, 1172-1181, 2000), a detailed statistical analysis of electron and ion EISCAT temperature measurements has been undertaken. This study was specifically concerned with the statistical dependence of heating events with other ambient parameters such as the electric field and electron density. The re- sults showed previously reported dependences such as the electron temperature being directly correlated with the ambient electric field and inversely related to the electron density. However, these correlations were found to be also dependent upon altitude. There was also evidence of the so called "Schlegel effect" (K. Schlegel, Reduced effective recombination coefficient in the disturbed polar E-region, J. Atmos. Terr. Phys., 44, 183-185, 1982); that is, the heated electron gas leads to increases in elec- tron density through a reduction in the recombination rate. This paper will present the statistical heating results and attempt to offer physical explanations and interpretations of the findings.

Single Crystal Diamond Needle as Point Electron Source.

PubMed

Kleshch, Victor I; Purcell, Stephen T; Obraztsov, Alexander N

2016-10-12

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Single Crystal Diamond Needle as Point Electron Source

NASA Astrophysics Data System (ADS)

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-10-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Time-resolved microplasma excitation temperature in a pulsed microwave discharge

NASA Astrophysics Data System (ADS)

Hopwood, Jeffrey; Monfared, Shabnam; Hoskinson, Alan

2013-09-01

Microwave-driven microplasmas are usually operated in a steady-state mode such that the electron temperature is constant in time. Transient measurements of excitation temperature and helium emission lines, however, suggest that short microwave pulses can be used to raise the electron energy by 20-30% for approximately 100 ns. Time-resolved optical emission spectrometry reveals an initial burst of light emission from the igniting microplasma. This emission overshoot is also correlated with a measured increase in excitation temperature. Excimer emission lags atomic emission, however, and does not overshoot. A simple model demonstrates that an increase in electron temperature is responsible for the overshoot of atomic optical emission at the beginning of each microwave pulse. The formation of dimers and subsequent excimer emission requires slower three-body collisions with the excited rare gas atom; this is why excimer emission does not overshoot the steady state value. Similar experimental and modeling results are observed in argon gas. The overshoot in electron temperature may be used to manipulate the collisional production of species in microplasmas using short, low-duty cycle microwave pulses. This material is based upon work supported by the USAF and Physical Sciences Inc., under contract No. FA8650-C-12-C-2312. Additional support was provided by the DARPA MPD program under award FA9550-12-1-0006.

EPR-based distance measurements at ambient temperature.

PubMed

Krumkacheva, Olesya; Bagryanskaya, Elena

2017-07-01

Pulsed dipolar (PD) EPR spectroscopy is a powerful technique allowing for distance measurements between spin labels in the range of 2.5-10.0nm. It was proposed more than 30years ago, and nowadays is widely used in biophysics and materials science. Until recently, PD EPR experiments were limited to cryogenic temperatures (T<80K). Recently, application of spin labels with long electron spin dephasing time at room temperature such as triarylmethyl radicals and nitroxides with bulky substituents at a position close to radical centers enabled measurements at room temperature and even at physiologically relevant temperatures by PD EPR as well as other approaches based on EPR (e.g., relaxation enhancement; RE). In this paper, we review the features of PD EPR and RE at ambient temperatures, in particular, requirements on electron spin phase memory time, ways of immobilization of biomolecules, the influence of a linker between the spin probe and biomolecule, and future opportunities. Copyright © 2017 Elsevier Inc. All rights reserved.

The effects of temperature and magnetic flux on electron transport through a four-channel DNA model

NASA Astrophysics Data System (ADS)

Lee, Sunhee; Hedin, Eric; Joe, Yong

2010-03-01

The temperature dependence of the conductivity of lambda phage DNA has been measured by Tran et al [1] experimentally, where the conductivity displayed strong (weak) temperature dependence above (below) a threshold temperature. In order to understand the temperature effects of electron transport theoretically, we study a two-dimensional and four-channel DNA model using a tight-binding (TB) Hamiltonian. The thermal effects within a TB model are incorporated into the hopping integral and the relative twist angle from its equilibrium value between base-pairs. Since these thermal structural fluctuations localize the electronic wave functions in DNA, we examine a temperature-dependent localization length, a temperature-driven transmission, and current-voltage characteristics in this system. In addition, we incorporate magnetic field effects into the analysis of the transmission through DNA in order to modulate the quantum interference between the electron paths that comprise the 4-channel structure. [1] P. Tran, B. Alavi, and G. Gruner, PRL 85, 1564 (2000).

Preliminary Low Temperature Electron Irradiation of Triple Junction Solar Cells

NASA Technical Reports Server (NTRS)

Stella, Paul M.; Mueller, Robert L.; Scrivner, Roy L.; Helizon, Roger S.

2007-01-01

For many years extending solar power missions far from the sun has been a challenge not only due to the rapid falloff in solar intensity (intensity varies as inverse square of solar distance) but also because some of the solar cells in an array may exhibit a LILT (low intensity low temperature) degradation that reduces array performance. Recent LILT tests performed on commercial triple junction solar cells have shown that high performance can be obtained at solar distances as great as approx. 5 AU1. As a result, their use for missions going far from the sun has become very attractive. One additional question that remains is whether the radiation damage experienced by solar cells under low temperature conditions will be more severe than when measured during room temperature radiation tests where thermal annealing may take place. This is especially pertinent to missions such as the New Frontiers mission Juno, which will experience cell irradiation from the trapped electron environment at Jupiter. Recent testing2 has shown that low temperature proton irradiation (10 MeV) produces cell degradation results similar to room temperature irradiations and that thermal annealing does not play a factor. Although it is suggestive to propose the same would be observed for low temperature electron irradiations, this has not been verified. JPL has routinely performed radiation testing on commercial solar cells and has also performed LILT testing to characterize cell performance under far sun operating conditions. This research activity was intended to combine the features of both capabilities to investigate the possibility of any room temperature annealing that might influence the measured radiation damage. Although it was not possible to maintain the test cells at a constant low temperature between irradiation and electrical measurements, it was possible to obtain measurements with the cell temperature kept well below room temperature. A fluence of 1E15 1MeV electrons was selected as representative of a moderately high dose that might be expected for a solar powered mission. Fluences much greater than this would require large increases in array area and mass, compromising the ability of PV to compete with non-solar alternatives.

Self-absorption characteristics of measured laser-induced plasma line shapes

NASA Astrophysics Data System (ADS)

Parigger, C. G.; Surmick, D. M.; Gautam, G.

2017-02-01

The determination of electron density and temperature is reported from line-of-sight measurements of laser-induced plasma. Experiments are conducted in standard ambient temperature and pressure air and in a cell containing ultra-high-pure hydrogen slightly above atmospheric pressure. Spectra of the hydrogen Balmer series lines can be measured in laboratory air due to residual moisture following optical breakdown generated with 13 to 14 nanosecond, pulsed Nd:YAG laser radiation. Comparisons with spectra obtained in hydrogen gas yields Abel-inverted line shape appearances that indicate occurrence of self-absorption. The electron density and temperature distributions along the line of sight show near-spherical rings, expanding at or near the speed of sound in the hydrogen gas experiments. The temperatures in the hydrogen studies are obtained using Balmer series alpha, beta, gamma profiles. Over and above the application of empirical formulae to derive the electron density from hydrogen alpha width and shift, and from hydrogen beta width and peak-separation, so-called escape factors and the use of a doubling mirror are discussed.

Experimental and theoretical investigation of the temperature dependent electronic quenching of O(1D) atoms in collisions with Kr

NASA Astrophysics Data System (ADS)

Nuñez-Reyes, Dianailys; Kłos, Jacek; Alexander, Millard H.; Dagdigian, Paul J.; Hickson, Kevin M.

2018-03-01

The kinetics and dynamics of the collisional electronic quenching of O(1D) atoms by Kr have been investigated in a joint experimental and theoretical study. The kinetics of quenching were measured over the temperature range 50-296 K using the Laval nozzle method. O(1D) atoms were prepared by 266 nm photolysis of ozone, and the decay of the O(1D) concentration was monitored through vacuum ultraviolet fluorescence at 115.215 nm, from which the rate constant was determined. To interpret the experiments, a quantum close-coupling treatment of the quenching transition from the 1D state to the 3Pj fine-structure levels in collisions with Kr, and also Ar and Xe, was carried out. The relevant potential energy curves and spin-orbit coupling matrix elements were obtained in electronic structure calculations. We find reasonable agreement between computed temperature-dependent O(1D)-Rg (Rg = Ar, Kr, Xe) quenching rate constants and the present measurements for Kr and earlier measurements. In particular, the temperature dependence is well described.

A Two-Fluid, MHD Coronal Model

NASA Technical Reports Server (NTRS)

Suess, Steven T.; Wang, A.-H.; Wu, S. T.; Poletto, G.; McComas, D. J.

1998-01-01

We describe first results from a numerical two-fluid MHD model of the global structure of the solar corona. The model is two-fluid in the sense that it accounts for the collisional energy exchange between protons and electrons. As in our single-fluid model, volumetric heat and momentum sources are required to produce high speed wind from coronal holes, low speed wind above streamers, and mass fluxes similar to the empirical solar wind. By specifying different proton and electron heating functions we obtain a high proton temperature in the coronal hole and a relatively low proton temperature in the streamer (in comparison with the electron temperature). This is consistent with inferences from SOHO/UVCS, and with the Ulysses/SWOOPS proton and electron temperature measurements which we show from the fast latitude scan. The density in the coronal hole between 2 solar radii and 5 solar radii (2RS and 5RS) is similar to the density reported from SPARTAN 201-01 measurements by Fisher and Guhathakurta. The proton mass flux scaled to 1 AU is 2.4 x 10(exp 8)/sq cm s, which is consistent with Ulysses observations. Inside the closed field region, the density is sufficiently high so that the simulation gives equal proton and electron temperatures due to the high collision rate. In open field regions (in the coronal hole and above the streamer) the proton and electron temperatures differ by varying amounts. In the streamer, the temperature and density are similar to those reported empirically by Li et al and the plasma beta is larger than unity everywhere above approx. 1.5 R(sub s), as it is in all other MHD coronal streamer models.

Effect of superconducting spacer layer thickness on magneto-transport and magnetic properties of La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Minaxi, E-mail: meenanith@gmail.com; Sharma, K. K., E-mail: kknitham@gmail.com; Pandey, Pankaj K.

2014-01-07

We have studied the magneto-transport and magnetic properties of LSMO/YBCO/LSMO trilayers on LaAlO{sub 3} (001) substrate, deposited using pulsed laser deposition technique. From x-ray diffraction measurements, it is confirmed that the grown trilayer films are single phase natured. The temperature dependent resistivity shows a metallic behavior below 350 K. At low temperature from resistivity fitted data, we observe that electron-electron, electron-phonon, and electron-magnon interactions are the main factors for scattering of carriers. The ferromagnetic LSMO layers suppress the critical temperature of YBCO spacer layer. We observe maximum magnetoresistance value ∼49% at 250 K for LSMO(200 nm)/YBCO(50 nm)/LSMO(200 nm) trilayer. Magnetization measurements reveal that at roommore » temperature the YBCO spacer layer is allowing the LSMO layers to interact antiferromagnetically.« less

Impact of metal gates on remote phonon scattering in titanium nitride/hafnium dioxide n-channel metal-oxide-semiconductor field effect transistors-low temperature electron mobility study

NASA Astrophysics Data System (ADS)

Maitra, Kingsuk; Frank, Martin M.; Narayanan, Vijay; Misra, Veena; Cartier, Eduard A.

2007-12-01

We report low temperature (40-300 K) electron mobility measurements on aggressively scaled [equivalent oxide thickness (EOT)=1 nm] n-channel metal-oxide-semiconductor field effect transistors (nMOSFETs) with HfO2 gate dielectrics and metal gate electrodes (TiN). A comparison is made with conventional nMOSFETs containing HfO2 with polycrystalline Si (poly-Si) gate electrodes. No substantial change in the temperature acceleration factor is observed when poly-Si is replaced with a metal gate, showing that soft optical phonons are not significantly screened by metal gates. A qualitative argument based on an analogy between remote phonon scattering and high-resolution electron energy-loss spectroscopy (HREELS) is provided to explain the underlying physics of the observed phenomenon. It is also shown that soft optical phonon scattering is strongly damped by thin SiO2 interface layers, such that room temperature electron mobility values at EOT=1 nm become competitive with values measured in nMOSFETs with SiON gate dielectrics used in current high performance processors.

Langmuir Probe Measurements in an Inductively Coupled Ar/CF4 Plasmas

NASA Technical Reports Server (NTRS)

Rao, M. V. V. S.; Meyyappan, M.; Sharma, S. P.; Arnold, James O. (Technical Monitor)

2000-01-01

Technological advancement in the microelectronics industry requires an understanding of the physical and chemical processes occurring in plasmas of fluorocarbon gases, such as carbon tetrafluoride (CF4) which is commonly used as an etchant, and their mixtures to optimize various operating parameters. In this paper we report data on electron number density (ne), electron temperature'(Te), electron energy distribution function (EEDF), mean electron energy, ion number density (ni), and plasma potential (Vp) measured by using Langmuir probe in an inductively coupled 13.56 MHz radio frequency plasmas generated in 50%Ar:50%CF4 mixture in the GEC cell. The probe data were recorded at various radial positions providing radial profiles of these plasma parameters at 10-50 mTorr pressures and 200 W and 300 W of RF power. Present measurements indicate that the electron and ion number densities increase with increase in pressure and power. Whereas the plasma potential and electron temperature decrease with increase in pressure, and they weakly depend on RF power. The radial profiles exhibit that the electron and ion number densities and the plasma potential peak at the center of the plasma with an exponential fall away from it, while the electron temperature has a minimum at the center and it increases steadily towards the electrode edge. The EEDFs have a characteristic drop near the low energy end at all pressures and pressures and their shapes represent non-Maxwellian plasma and exhibit more like Druyvesteyn energy distribution.v

Charge-carrier mobilities in Cd(0.8)Zn(0.2)Te single crystals used as nuclear radiation detectors

NASA Technical Reports Server (NTRS)

Burshtein, Z.; Jayatirtha, H. N.; Burger, A.; Butler, J. F.; Apotovsky, B.; Doty, F. P.

1993-01-01

Charge-carrier mobilities were measured for the first time in Cd(0.8)Zn(0.2)Te single crystals using time-of-flight measurements of charge carriers produced by short (10 ns) light pulses from a frequency-doubled Nd:YAG laser (532 nm). The electron mobility displayed a T exp -1.1 dependence on the absolute temperature T in the range 200-320 K, with a room-temperature mobility of 1350 sq cm/V s. The hole mobility displayed a T exp -2.0 dependence in the same temperature range, with a room-temperature mobility of 120 sq cm/V s. Cd(0.8)Zn(0.2)Te appears to be a very favorable material for a room-temperature electronic nuclear radiation detector.

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

NASA Astrophysics Data System (ADS)

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 non-Maxwellian electron velocity distributions in a reflex discharge

NASA Technical Reports Server (NTRS)

Phipps, C. R., Jr.; Bershader, D.

1978-01-01

The results of a ruby laser Thomson scattering study of the space and time-resolved electron velocity distributions in a pulsed Penning discharge in hydrogen are presented. Electron densities were to the order of 10 to the 13th/cu cm and temperatures were roughly 3 eV. This point is just prior to the cessation of the discharge ohmic heating pulse. For magnetic strengths less than 200 G, Maxwellian distributions were found over an energy range six times thermal energy. Temperatures agreed with Langmuir probe data. For fields of 450 G, chaotic plasma potentials were observed to be unstable and the Thomson scattering showed that the electron velocity distributions had central temperatures of 2 eV and wing temperatures of 15-12 eV.

Radial Profiles of the Plasma Electron Characteristics in a 30 kW Arc Jet

NASA Technical Reports Server (NTRS)

Codron, Douglas A.; Nawaz, Anuscheh

2013-01-01

The present effort aims to strengthen modeling work conducted at the NASA Ames Research Center by measuring the critical plasma electron characteristics within and slightly outside of an arc jet plasma column. These characteristics are intended to give physical insights while assisting in the formulation of boundary conditions to validate full scale simulations. Single and triple Langmuir probes have been used to achieve estimates of the electron temperature (T(sub e)), electron number density (n(sub e)) and plasma potential (outside of the plasma column) as probing location is varied radially from the flow centerline. Both the electron temperature and electron number density measurements show a large dependence on radial distance from the plasma column centerline with T(sub e) approx. = (3 - 12 eV and n(sub e) approx. = 10(exp 12) - 10(exp 14)/cu cm.

Martian Electron Temperatures in the Sub Solar Region.

NASA Astrophysics Data System (ADS)

Fowler, C. M.; Peterson, W. K.; Andersson, L.; Thiemann, E.; Mayyasi, M.; Yelle, R. V.; Benna, M.; Espley, J. R.

2017-12-01

Observations from Viking, and MAVEN have shown that the observed ionospheric electron temperatures are systematically higher than those predicted by many models. Because electron temperature is a balance between heating, cooling, and heat transport, we systematically compare the magnitude of electron heating from photoelectrons, electron cooling and heat transport, as a function of altitude within 30 degrees of the sub solar point. MAVEN observations of electron temperature and density, EUV irradiance, neutral and ion composition are used to evaluate terms in the heat equation following the framework of Matta et al. (Icarus, 2014, doi:10.1016/j.icarus.2013.09.006). Our analysis is restricted to inbound orbits where the magnetic field is within 30 degrees of horizontal. MAVEN sampled the sub solar region in May 2015 and again in May 2017, in near northern spring equinoctial conditions. Solar activity was higher and the spacecraft sampled altitudes down to 120 km in 2015, compared to 160 km in 2017. We find that between 160 and 200 km the Maven electron temperatures are in thermal equilibrium, in the sub solar region, on field lines inclined less than 30 degrees to the horizontal. Above 200km the data suggest that heating from other sources, such as wave heating are significant. Below 160 km some of the discrepancy comes from measurement limitations. This is because the MAVEN instrument cannot resolve the lowest electron temperatures, and because some cooling rates scale as the difference between the electron and neutral temperatures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borovsky, Joseph E; Cayton, Thomas E; Denton, Michael H

Electron flux measurements from 7 satellites in geosynchronous orbit from 1990-2007 are fit with relativistic bi-Maxwellians, yielding a number density n and temperature T description of the outer electron radiation belt. For 54.5 spacecraft years of measurements the median value ofn is 3.7x10-4 cm-3 and the median value ofT is 142 keY. General statistical properties of n, T, and the 1.1-1.5 MeV flux J are investigated, including local-time and solar-cycle dependencies. Using superposed-epoch analysis triggered on storm onset, the evolution of the outer electron radiation belt through high-speed-steam-driven storms is investigated. The number density decay during the calm before themore » storm is seen, relativistic-electron dropouts and recoveries from dropout are investigated, and the heating of the outer electron radiation belt during storms is examined. Using four different triggers (SSCs, southward-IMF CME sheaths, southward-IMF magnetic clouds, and minimum Dst), CME-driven storms are analyzed with superposed-epoch techniques. For CME-driven storms an absence of a density decay prior to storm onset is found, the compression of the outer electron radiation belt at time of SSC is analyzed, the number-density increase and temperature decrease during storm main phase is seen, and the increase in density and temperature during storm recovery phase is observed. Differences are found between the density-temperature and the flux descriptions, with more information for analysis being available in the density-temperature description.« less

First measurement of time evolution of electron temperature profiles with Nd:YAG Thomson scattering system on Heliotron J.

PubMed

Kenmochi, N; Minami, T; Takahashi, C; Tei, S; Mizuuchi, T; Kobayashi, S; Nagasaki, K; Nakamura, Y; Okada, H; Kado, S; Yamamoto, S; Ohshima, S; Konoshima, S; Shi, N; Zang, L; Ohtani, Y; Kasajima, K; Sano, F

2014-11-01

A Nd:YAG Thomson scattering system has been developed for Heliotron J. The system consists of two 550 mJ 50 Hz lasers, large collection optics, and 25 radial channel (∼1 cm spatial resolution) interference polychromators. This measurement system achieves a S/N ratio of ∼50 for low-density plasma (ne ∼ 0.5 × 10(19) m(-3)). A time evolution of electron temperature profiles was measured with this system for a high-intensity gas-puff (HIGP) fueling neutral-beam-injection plasma. The peripheral temperature of the higher-density phase after HIGP recovers to the low-density pre-HIGP level, suggesting that improving particle transport in the HIGP plasma may be possible.

Divertor electron temperature and impurity diffusion measurements with a spectrally resolved imaging radiometer.

PubMed

Clayton, D J; Jaworski, M A; Kumar, D; Stutman, D; Finkenthal, M; Tritz, K

2012-10-01

A divertor imaging radiometer (DIR) diagnostic is being studied to measure spatially and spectrally resolved radiated power P(rad)(λ) in the tokamak divertor. A dual transmission grating design, with extreme ultraviolet (~20-200 Å) and vacuum ultraviolet (~200-2000 Å) gratings placed side-by-side, can produce coarse spectral resolution over a broad wavelength range covering emission from impurities over a wide temperature range. The DIR can thus be used to evaluate the separate P(rad) contributions from different ion species and charge states. Additionally, synthetic spectra from divertor simulations can be fit to P(rad)(λ) measurements, providing a powerful code validation tool that can also be used to estimate electron divertor temperature and impurity transport.

Investigating electron spin resonance spectroscopy of a spin-½ compound in a home-built spectrometer

NASA Astrophysics Data System (ADS)

Sarkar, Jit; Roy, Subhadip; Singh, Jitendra Kumar; Singh, Sourabh; Chakraborty, Tanmoy; Mitra, Chiranjib

2018-05-01

In this work we report electron spin resonance (ESR) measurements performed on NH4CuPO4.H2O, a Heisenberg spin ½ dimer compound. We carried out the experiments both at room temperature and at 78 K, which are well above the antiferromagnetic ordering temperature of the system where the paramagnetic spins have a dominant role in determining its magnetic behavior. We performed the measurements in a home built custom designed continuous wave electron spin resonance (CW-ESR) spectrometer. By analyzing the experimental data, we were able to quantify the Landé g-factor and the ESR line-width of the sample.

Characterization of the Exradin W1 scintillator for use in radiotherapy.

PubMed

Carrasco, P; Jornet, N; Jordi, O; Lizondo, M; Latorre-Musoll, A; Eudaldo, T; Ruiz, A; Ribas, M

2015-01-01

To evaluate the main characteristics of the Exradin W1 scintillator as a dosimeter and to estimate measurement uncertainties when used in radiotherapy. We studied the calibration procedure, energy and modality dependence, short-term repeatability, dose-response linearity, angular dependence, temperature dependence, time to reach thermal equilibrium, dose-rate dependence, water-equivalent depth of the effective measurement point, and long-term stability. An uncertainty budget was derived for relative and absolute dose measurements in photon and electron beams. Exradin W1 showed a temperature dependence of -0.225% °C(-1). The loss of sensitivity with accumulated dose decreased with use. The sensitivity of Exradin W1 was energy independent for high-energy photon and electron beams. All remaining dependencies of Exradin W1 were around or below 0.5%, leading to an uncertainty budget of about 1%. When a dual channel electrometer with automatic trigger was not used, timing effects became significant, increasing uncertainties by one order of magnitude. The Exradin W1 response is energy independent for high energy x-rays and electron beams, and only one calibration coefficient is needed. A temperature correction factor should be applied to keep uncertainties around 2% for absolute dose measurements and around 1% for relative measurements in high-energy photon and electron beams. The Exradin W1 scintillator is an excellent alternative to detectors such as diodes for relative dose measurements.

Thomson scattering diagnostic for the measurement of ion species fraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, J S; Park, H S; Amendt, A

2012-05-01

Simultaneous Thomson scattering measurements of collective electron-plasma and ion-acoustic fluctuations have been utilized to determine ion species fraction from laser produced CH plasmas. The CH{sub 2} foil is heated with 10 laser beams, 500 J per beam, at the Omega Laser facility. Thomson scattering measurements are made 4 mm from the foil surface using a 30 J 2{omega} probe laser with a 1 ns pulse length. Using a series of target shots the plasma evolution is measured from 2.5 ns to 9 ns after the rise of the heater beams. Measuring the electron density and temperature from the electron-plasma fluctuationsmore » constrains the fit of the two-ion species theoretical form factor for the ion feature such that the ion temperature, plasma flow velocity and ion species fraction are determined. The ion species fraction is determined to an accuracy of {+-}0.06 in species fraction.« less

Anisotropic electron temperature measurements without knowing the spectral transmissivity for a JT-60SA Thomson scattering diagnostic.

PubMed

Tojo, H; Hatae, T; Yatsuka, E; Itami, K

2012-10-01

This paper focuses on a method for measuring the electron temperature (T(e)) without knowing the transmissivity using Thomson scattering diagnostic with a double-pass scattering system. Application of this method for measuring the anisotropic T(e), i.e., the T(e) in the directions parallel (T(eparallel)) and perpendicular (T(eperpendicular)) to the magnetic field, is proposed. Simulations based on the designed parameters for a JT-60SA indicate the feasibility of the measurements except in certain T(e) ranges, e.g., T(eparallel) ~ 3.5T(eperpendicular) at 120° of the scattering angle.

Superconducting fluctuations and characteristic time scales in amorphous WSi

NASA Astrophysics Data System (ADS)

Zhang, Xiaofu; Lita, Adriana E.; Sidorova, Mariia; Verma, Varun B.; Wang, Qiang; Nam, Sae Woo; Semenov, Alexei; Schilling, Andreas

2018-05-01

We study magnitudes and temperature dependencies of the electron-electron and electron-phonon interaction times which play the dominant role in the formation and relaxation of photon-induced hotspots in two-dimensional amorphous WSi films. The time constants are obtained through magnetoconductance measurements in a perpendicular magnetic field in the superconducting fluctuation regime and through time-resolved photoresponse to optical pulses. The excess magnetoconductivity is interpreted in terms of the weak-localization effect and superconducting fluctuations. Aslamazov-Larkin and Maki-Thompson superconducting fluctuations alone fail to reproduce the magnetic field dependence in the relatively high magnetic field range when the temperature is rather close to Tc because the suppression of the electronic density of states due to the formation of short-lifetime Cooper pairs needs to be considered. The time scale τi of inelastic scattering is ascribed to a combination of electron-electron (τe -e) and electron-phonon (τe -p h) interaction times, and a characteristic electron-fluctuation time (τe -f l) , which makes it possible to extract their magnitudes and temperature dependencies from the measured τi. The ratio of phonon-electron (τp h -e) and electron-phonon interaction times is obtained via measurements of the optical photoresponse of WSi microbridges. Relatively large τe -p h/τp h -e and τe -p h/τe -e ratios ensure that in WSi the photon energy is more efficiently confined in the electron subsystem than in other materials commonly used in the technology of superconducting nanowire single-photon detectors (SNSPDs). We discuss the impact of interaction times on the hotspot dynamics and compare relevant metrics of SNSPDs from different materials.

Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sung, C., E-mail: csung@physics.ucla.edu; White, A. E.; Greenwald, M.

2016-04-15

Long wavelength turbulent electron temperature fluctuations (k{sub y}ρ{sub s} < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local,more » electrostatic ion-scale simulations (k{sub y}ρ{sub s} ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)].« less

Ultrafast non-radiative dynamics of atomically thin MoSe 2

DOE PAGES

Lin, Ming -Fu; Kochat, Vidya; Krishnamoorthy, Aravind; ...

2017-10-17

Non-radiative energy dissipation in photoexcited materials and resulting atomic dynamics provide a promising pathway to induce structural phase transitions in two-dimensional materials. However, these dynamics have not been explored in detail thus far because of incomplete understanding of interaction between the electronic and atomic degrees of freedom, and a lack of direct experimental methods to quantify real-time atomic motion and lattice temperature. Here, we explore the ultrafast conversion of photoenergy to lattice vibrations in a model bi-layered semiconductor, molybdenum diselenide, MoSe 2. Specifically, we characterize sub-picosecond lattice dynamics initiated by the optical excitation of electronic charge carriers in the highmore » electron-hole plasma density regime. Our results focuses on the first ten picosecond dynamics subsequent to photoexcitation before the onset of heat transfer to the substrate, which occurs on a ~100 picosecond time scale. Photoinduced atomic motion is probed by measuring the time dependent Bragg diffraction of a delayed mega-electronvolt femtosecond electron beam. Transient lattice temperatures are characterized through measurement of Bragg peak intensities and calculation of the Debye-Waller factor (DWF). These measurements show a sub-picosecond decay of Bragg diffraction and a correspondingly rapid rise in lattice temperatures. We estimate a high quantum yield for the conversion of excited charge carrier energy to lattice motion under our experimental conditions, indicative of a strong electron-phonon interaction. First principles nonadiabatic quantum molecular dynamics simulations (NAQMD) on electronically excited MoSe 2 bilayers reproduce the observed picosecond-scale increase in lattice temperature and ultrafast conversion of photoenergy to lattice vibrations. Calculation of excited-state phonon dispersion curves suggests that softened vibrational modes in the excited state are involved in efficient and rapid energy transfer between the electronic system and the lattice.« less

Ultrafast non-radiative dynamics of atomically thin MoSe 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Ming -Fu; Kochat, Vidya; Krishnamoorthy, Aravind

Non-radiative energy dissipation in photoexcited materials and resulting atomic dynamics provide a promising pathway to induce structural phase transitions in two-dimensional materials. However, these dynamics have not been explored in detail thus far because of incomplete understanding of interaction between the electronic and atomic degrees of freedom, and a lack of direct experimental methods to quantify real-time atomic motion and lattice temperature. Here, we explore the ultrafast conversion of photoenergy to lattice vibrations in a model bi-layered semiconductor, molybdenum diselenide, MoSe 2. Specifically, we characterize sub-picosecond lattice dynamics initiated by the optical excitation of electronic charge carriers in the highmore » electron-hole plasma density regime. Our results focuses on the first ten picosecond dynamics subsequent to photoexcitation before the onset of heat transfer to the substrate, which occurs on a ~100 picosecond time scale. Photoinduced atomic motion is probed by measuring the time dependent Bragg diffraction of a delayed mega-electronvolt femtosecond electron beam. Transient lattice temperatures are characterized through measurement of Bragg peak intensities and calculation of the Debye-Waller factor (DWF). These measurements show a sub-picosecond decay of Bragg diffraction and a correspondingly rapid rise in lattice temperatures. We estimate a high quantum yield for the conversion of excited charge carrier energy to lattice motion under our experimental conditions, indicative of a strong electron-phonon interaction. First principles nonadiabatic quantum molecular dynamics simulations (NAQMD) on electronically excited MoSe 2 bilayers reproduce the observed picosecond-scale increase in lattice temperature and ultrafast conversion of photoenergy to lattice vibrations. Calculation of excited-state phonon dispersion curves suggests that softened vibrational modes in the excited state are involved in efficient and rapid energy transfer between the electronic system and the lattice.« less

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic.

PubMed

Rowan, W L; Houshmandyar, S; Phillips, P E; Austin, M E; Beno, J H; Hubbard, A E; Khodak, A; Ouroua, A; Taylor, G

2016-11-01

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct view of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rowan, W. L., E-mail: w.l.rowan@austin.utexas.edu; Houshmandyar, S.; Phillips, P. E.

2016-11-15

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct viewmore » of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.« less

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic

DOE PAGES

Rowan, W. L.; Houshmandyar, S.; Phillips, P. E.; ...

2016-09-07

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct viewmore » of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Here, blackbody radiation sources are provided for in situ calibration.« less

Carrier-Specific Femtosecond XUV Transient Absorption of PbI 2 Reveals Ultrafast Nonradiative Recombination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Ming-Fu; Verkamp, Max A.; Leveillee, Joshua

Femtosecond carrier recombination in PbI 2 is measured using tabletop high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy and ultrafast electron diffraction. XUV absorption from 45 eV to 62 eV measures transitions from the iodine 4d core level to the conduction band density of states. Photoexcitation at 400 nm creates separate and distinct transient absorption signals for holes and electrons, separated in energy by the 2.4 eV band gap of the semiconductor. The shape of the conduction band and therefore the XUV absorption spectrum is temperature dependent, and nonradiative recombination converts the initial electronic excitation to thermal excitation within picoseconds. Ultrafastmore » electron diffraction (UED) is used to measure the lattice temperature and confirm the recombination mechanism. Lastly, the XUV and UED results support a 2nd-order recombination model with a rate constant of 2.5x10 -9 cm 3/s.« less

Carrier-Specific Femtosecond XUV Transient Absorption of PbI 2 Reveals Ultrafast Nonradiative Recombination

DOE PAGES

Lin, Ming-Fu; Verkamp, Max A.; Leveillee, Joshua; ...

2017-11-30

Femtosecond carrier recombination in PbI 2 is measured using tabletop high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy and ultrafast electron diffraction. XUV absorption from 45 eV to 62 eV measures transitions from the iodine 4d core level to the conduction band density of states. Photoexcitation at 400 nm creates separate and distinct transient absorption signals for holes and electrons, separated in energy by the 2.4 eV band gap of the semiconductor. The shape of the conduction band and therefore the XUV absorption spectrum is temperature dependent, and nonradiative recombination converts the initial electronic excitation to thermal excitation within picoseconds. Ultrafastmore » electron diffraction (UED) is used to measure the lattice temperature and confirm the recombination mechanism. Lastly, the XUV and UED results support a 2nd-order recombination model with a rate constant of 2.5x10 -9 cm 3/s.« less

Flush-mounted probe diagnostics for argon glow discharge plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Liang, E-mail: xld02345@mail.ustc.edu.cn; Cao, Jinxiang; Liu, Yu

2014-09-15

A comparison is made between plasma parameters measured by a flush-mounted probe (FP) and a cylindrical probe (CP) in argon glow discharge plasma. Parameters compared include the space potential, the plasma density, and the effective electron temperature. It is found that the ion density determined by the FP agrees well with the electron density determined by the CP in the quasi-neutral plasma to better than 10%. Moreover, the space potential and effective electron temperature calculated from electron energy distribution function measured by the FP is consistent with that measured by the CP over the operated discharge current and pressure ranges.more » These results present the FP can be used as a reliable diagnostic tool in the stable laboratory plasma and also be anticipated to be applied in other complicated plasmas, such as tokamaks, the region of boundary-layer, and so on.« less

Room temperature mechanical properties of electron beam welded zircaloy-4 sheet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parga, C. J.; Rooyen, I. J.; Coryell, B. D.

Room temperature mechanical properties of electron beam welded and plain Zircaloy-4 sheet (1.6mm thick) have been measured and compared. Various welding parameters were utilized to join sheet material. Electron beam welded specimens and as-received sheet specimens show comparable mechanical properties. Zr-4 sheet displays anisotropy; tensile properties measured for transverse display higher elastic modulus, yield strength, reduction of area and slightly lower ductility than for the longitudinal (rolling direction). Higher welding power increases the alloy’s hardness, elastic modulus and yield strength, with a corresponding decrease in tensile strength and ductility. The hardness measured at weld is comparable to the parent metalmore » hardness. Hardness at heat-affected-zone is slightly higher. Electron microscopic examination shows distinct microstructure morphology and grain size at the weld zone, HAZ and parent metal. A correlation between welding parameters, mechanical properties and microstructural features was established for electron beam welded Zircaloy-4 sheet material.« less

Room temperature mechanical properties of electron beam welded zircaloy-4 sheet

DOE PAGES

Parga, C. J.; Rooyen, I. J.; Coryell, B. D.; ...

2017-11-04

Room temperature mechanical properties of electron beam welded and plain Zircaloy-4 sheet (1.6mm thick) have been measured and compared. Various welding parameters were utilized to join sheet material. Electron beam welded specimens and as-received sheet specimens show comparable mechanical properties. Zr-4 sheet displays anisotropy; tensile properties measured for transverse display higher elastic modulus, yield strength, reduction of area and slightly lower ductility than for the longitudinal (rolling direction). Higher welding power increases the alloy’s hardness, elastic modulus and yield strength, with a corresponding decrease in tensile strength and ductility. The hardness measured at weld is comparable to the parent metalmore » hardness. Hardness at heat-affected-zone is slightly higher. Electron microscopic examination shows distinct microstructure morphology and grain size at the weld zone, HAZ and parent metal. A correlation between welding parameters, mechanical properties and microstructural features was established for electron beam welded Zircaloy-4 sheet material.« less

On-chip magnetic cooling of a nanoelectronic device.

PubMed

Bradley, D I; Guénault, A M; Gunnarsson, D; Haley, R P; Holt, S; Jones, A T; Pashkin, Yu A; Penttilä, J; Prance, J R; Prunnila, M; Roschier, L

2017-04-04

We demonstrate significant cooling of electrons in a nanostructure below 10 mK by demagnetisation of thin-film copper on a silicon chip. Our approach overcomes the typical bottleneck of weak electron-phonon scattering by coupling the electrons directly to a bath of refrigerated nuclei, rather than cooling via phonons in the host lattice. Consequently, weak electron-phonon scattering becomes an advant- age. It allows the electrons to be cooled for an experimentally useful period of time to temperatures colder than the dilution refrigerator platform, the incoming electrical connections, and the host lattice. There are efforts worldwide to reach sub-millikelvin electron temperatures in nanostructures to study coherent electronic phenomena and improve the operation of nanoelectronic devices. On-chip magnetic cooling is a promising approach to meet this challenge. The method can be used to reach low, local electron temperatures in other nanostructures, obviating the need to adapt traditional, large demagnetisation stages. We demonstrate the technique by applying it to a nanoelectronic primary thermometer that measures its internal electron temperature. Using an optimised demagnetisation process, we demonstrate cooling of the on-chip electrons from 9 mK to below 5 mK for over 1000 seconds.

On-chip magnetic cooling of a nanoelectronic device

NASA Astrophysics Data System (ADS)

Bradley, D. I.; Guénault, A. M.; Gunnarsson, D.; Haley, R. P.; Holt, S.; Jones, A. T.; Pashkin, Yu. A.; Penttilä, J.; Prance, J. R.; Prunnila, M.; Roschier, L.

2017-04-01

We demonstrate significant cooling of electrons in a nanostructure below 10 mK by demagnetisation of thin-film copper on a silicon chip. Our approach overcomes the typical bottleneck of weak electron-phonon scattering by coupling the electrons directly to a bath of refrigerated nuclei, rather than cooling via phonons in the host lattice. Consequently, weak electron-phonon scattering becomes an advant- age. It allows the electrons to be cooled for an experimentally useful period of time to temperatures colder than the dilution refrigerator platform, the incoming electrical connections, and the host lattice. There are efforts worldwide to reach sub-millikelvin electron temperatures in nanostructures to study coherent electronic phenomena and improve the operation of nanoelectronic devices. On-chip magnetic cooling is a promising approach to meet this challenge. The method can be used to reach low, local electron temperatures in other nanostructures, obviating the need to adapt traditional, large demagnetisation stages. We demonstrate the technique by applying it to a nanoelectronic primary thermometer that measures its internal electron temperature. Using an optimised demagnetisation process, we demonstrate cooling of the on-chip electrons from 9 mK to below 5 mK for over 1000 seconds.

Effect of working power and pressure on plasma properties during the deposition of TiN films in reactive magnetron sputtering plasma measured using Langmuir probe measurement

NASA Astrophysics Data System (ADS)

How, Soo Ren; Nayan, Nafarizal; Khairul Ahmad, Mohd; Fhong Soon, Chin; Zainizan Sahdan, Mohd; Lias, Jais; Shuhaimi Abu Bakar, Ahmad; Arshad, Mohd Khairuddin Md; Hashim, Uda; Yazid Ahmad, Mohd

2018-04-01

The ion, electron density and electron temperature during formation of TiN films in reactive magnetron sputtering system have been investigated for various settings of radio frequency (RF) power and working pressure by using Langmuir probe measurements. The RF power and working pressure able to affect the densities and plasma properties during the deposition process. In this work, a working pressure (100 and 20 mTorr) and RF power (100, 150 and 200 W) have been used for data acquisition of probe measurement. Fundamental of studied on sputter deposition is very important for improvement of film quality and deposition rate. Higher working pressure and RF power able to produce a higher ion density and reduction of electron temperature.

Electron energy distribution function in the divertor region of the COMPASS tokamak during neutral beam injection heating

NASA Astrophysics Data System (ADS)

Hasan, E.; Dimitrova, M.; Havlicek, J.; Mitošinková, K.; Stöckel, J.; Varju, J.; Popov, Tsv K.; Komm, M.; Dejarnac, R.; Hacek, P.; Panek, R.; the COMPASS Team

2018-02-01

This paper presents the results from swept probe measurements in the divertor region of the COMPASS tokamak in D-shaped, L-mode discharges, with toroidal magnetic field BT = 1.15 T, plasma current Ip = 180 kA and line-average electron densities varying from 2 to 8×1019 m-3. Using neutral beam injection heating, the electron energy distribution function is studied before and during the application of the beam. The current-voltage characteristics data are processed using the first-derivative probe technique. This technique allows one to evaluate the plasma potential and the real electron energy distribution function (respectively, the electron temperatures and densities). At the low average electron density of 2×1019 m-3, the electron energy distribution function is bi-Maxwellian with a low-energy electron population with temperatures 4-6 eV and a high-energy electron group 12-25 eV. As the line-average electron density is increased, the electron temperatures decrease. At line-average electron densities above 7×1019 m-3, the electron energy distribution function is found to be Maxwellian with a temperature of 6-8.5 eV. The effect of the neutral beam injection heating power in the divertor region is also studied.

Determination of the coalescence temperature of latexes by environmental scanning electron microscopy.

PubMed

Gonzalez, Edurne; Tollan, Christopher; Chuvilin, Andrey; Barandiaran, Maria J; Paulis, Maria

2012-08-01

A new methodology for quantitative characterization of the coalescence process of waterborne polymer dispersion (latex) particles by environmental scanning electron microscopy (ESEM) is proposed. The experimental setup has been developed to provide reproducible latex monolayer depositions, optimized contrast of the latex particles, and a reliable readout of the sample temperature. Quantification of the coalescence process under dry conditions has been performed by image processing based on evaluation of the image autocorrelation function. As a proof of concept the coalescence of two latexes with known and differing glass transition temperatures has been measured. It has been shown that a reproducibility of better than 1.5 °C can be obtained for the measurement of the coalescence temperature.

Preliminary low temperature electron irradiation of triple junction solar cells

NASA Technical Reports Server (NTRS)

Stella, Paul M.; Mueller, Robert L.; Scrivner, Roy L.; Helizon, Roger S.

2005-01-01

JPL has routinely performed radiation testing on commercial solar cells and has also performed LILT testing to characterize cell performance under far sun operating conditions. This research activity was intended to combine the features of both capabilities to investigate the possibility of any room temperature annealing that might influence the measured radiation damage. Although it was not possible to maintain the test cells at a constant low temperature between irradiation and electrical measurements, it was possible to obtain measurements with the cell temperature kept well below room temperature.

Analysis of magnesium XI line profiles from solar active regions

NASA Technical Reports Server (NTRS)

Blake, R. L.; Cowan, R. D.; Felthauser, H.; Fenimore, E. E.; Hockaday, M. P.; Bely-Dubau, F.; Faucher, P.; Steenman-Clark, L.

1984-01-01

High-resolution solar spectra of the Mg XI 1s2 1S0-1s2p 1P1 resonance line at 9.169 A and the associated nearby satellite lines obtained from two rocket-borne crystal spectrometer measurements are presented. Comparisons with two independent sets of theoretical calculations for the 1s2nl-1s2pnl dielectronic satellite lines with n = 3-7 indicate electron temperatures of 4-4.5 million K. Measured line widths indicate either that the ion temperature exceeds the electron temperature by about a million K or that about 28 km/s of turbulence is present.

Plasma dynamics near critical density inferred from direct measurements of laser hole boring

NASA Astrophysics Data System (ADS)

Gong, Chao; Tochitsky, Sergei Ya.; Fiuza, Frederico; Pigeon, Jeremy J.; Joshi, Chan

2016-06-01

We have used multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, vHB, of the density cavity pushed forward by a train of C O2 laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the vHB falls rapidly as the laser pulse intensity falls at the back of the laser pulse train. A heuristic theory is presented that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. The measured values of vHB, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.

Plasma dynamics near critical density inferred from direct measurements of laser hole boring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Chao; Tochitsky, Sergei Ya.; Fiuza, Frederico

Here, we use multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, vHB, of the density cavity pushed forward by a train of CO 2 laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the vHB falls rapidly as the laser pulse intensity falls at the back of the laser pulsemore » train. We present a heuristic theory that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. Furthermore, the measured values of v HB, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.« less

Plasma dynamics near critical density inferred from direct measurements of laser hole boring.

PubMed

Gong, Chao; Tochitsky, Sergei Ya; Fiuza, Frederico; Pigeon, Jeremy J; Joshi, Chan

2016-06-01

We have used multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, v_{HB}, of the density cavity pushed forward by a train of CO_{2} laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the v_{HB} falls rapidly as the laser pulse intensity falls at the back of the laser pulse train. A heuristic theory is presented that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. The measured values of v_{HB}, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.

Plasma dynamics near critical density inferred from direct measurements of laser hole boring

DOE PAGES

Gong, Chao; Tochitsky, Sergei Ya.; Fiuza, Frederico; ...

2017-06-24

Here, we use multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, vHB, of the density cavity pushed forward by a train of CO 2 laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the vHB falls rapidly as the laser pulse intensity falls at the back of the laser pulsemore » train. We present a heuristic theory that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. Furthermore, the measured values of v HB, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.« less

Exploring the Electrical Conductivity of Cytochrome P450 by Nano-Electrode and Conductive Atomic Force Microscopy

NASA Astrophysics Data System (ADS)

Li, Debin; Gu, Jianhua; Chye, Yewhee; Lederman, David; Kabulski, Jarod; Gannett, Peter; Tracy, Timothy

2006-03-01

There is a growing interest in measuring the conductivity of electron-transfer proteins. The cytochrome P450 (CP450) enzymes represent an important class of heme-containing enzymes. Immobilizing CP450 enzymes on a surface can be used for studying a single enzyme with respect to electron transfer. The spin state of the heme iron can change upon binding of a substrate. In our experiment, CP450 (diameter ˜ 5 nm) has been bonded to a metal surface. Nano-electrodes (gap < 10 nm) were fabricated by defining a bridge via e-beam lithography and then breaking the junction by electromigration at low temperatures. We have examined the electronic properties of CP450 by itself and after binding CP450 with flurbiprofen. The room temperature I-V conductivity is reminiscent to cyclic voltammetry measurements, indicating the presence of strong ionic transfer. At lower temperatures (100 K) the I-V characteristics indicate electronic transport dominated by tunneling processes. The conductive AFM is an additional method used to examine the enzyme's electronic properties. The results from two methods will be discussed..

Development of Cryogenic Enhancement-Mode Pseudomorphic High-Electron-Mobility Transistor Amplifier

NASA Astrophysics Data System (ADS)

Hirata, T.; Okazaki, T.; Obara, K.; Yano, H.; Ishikawa, O.

2017-06-01

This paper reports the technical details of the development of a low-temperature amplifier for nuclear magnetic resonance measurements of superfluid {}^3He in very confined geometries. The amplifier consists of commercially available enhancement-mode pseudomorphic high-electron-mobility transistor devices and temperature-insensitive passive components with an operating frequency range of 0.2-6 MHz.

Electronically conductive ceramics for high temperature oxidizing environments

DOEpatents

Kucera, Gene H.; Smith, James L.; Sim, James W.

1986-01-01

A high temperature, ceramic composition having electronic conductivity as measured by resistivity below about 500 ohm-cm, chemical stability particularly with respect to cathode conditions in a molten carbonate fuel cell, and composed of an alkali metal, transition metal oxide containing a dopant metal in the crystalline structure to replace a portion of the alkali metal or transition metal.

Study of thermal-field emission properties and investigation of temperature dependent noise in the field emission current from vertical carbon nanotube emitters

NASA Astrophysics Data System (ADS)

Kolekar, Sadhu; Patole, S. P.; Patil, Sumati; Yoo, J. B.; Dharmadhikari, C. V.

2017-10-01

We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well-defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD) in order to understand the effect of temperature on distribution of electron emission spots and ring like structures in Field Emission Microscope (FEM) image. The FEM images could be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 from FEM image is typically, 4.5 × 107 and the actual number emitters per cm2 present as per Atomic Force Microscopy (AFM) data is 1.2 × 1012. The measured Current-Voltage (I-V) characteristics exhibit non linear Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current were recorded at different temperatures and Fast Fourier transformed into temperature dependent power spectral density. The latter was found to obey power law relation S(f) = A(Iδ/fξ), where δ and ξ are temperature dependent current and frequency exponents respectively.

Simultaneous imaging electron- and ion-feature Thomson scattering measurements of radiatively heated Xe.

PubMed

Pollock, B B; Meinecke, J; Kuschel, S; Ross, J S; Shaw, J L; Stoafer, C; Divol, L; Tynan, G R; Glenzer, S H

2012-10-01

Uniform density and temperature Xe plasmas have been produced over >4 mm scale-lengths using x-rays generated in a cylindrical Pb cavity. The cavity is 750 μm in depth and diameter, and is heated by a 300 J, 2 ns square, 1054 nm laser pulse focused to a spot size of 200 μm at the cavity entrance. The plasma is characterized by simultaneous imaging Thomson scattering measurements from both the electron and ion scattering features. The electron feature measurement determines the spatial electron density and temperature profile, and using these parameters as constraints in the ion feature analysis allows an accurate determination of the charge state of the Xe ions. The Thomson scattering probe beam is 40 J, 200 ps, and 527 nm, and is focused to a 100 μm spot size at the entrance of the Pb cavity. Each system has a spatial resolution of 25 μm, a temporal resolution of 200 ps (as determined by the probe duration), and a spectral resolution of 2 nm for the electron feature system and 0.025 nm for the ion feature system. The experiment is performed in a Xe filled target chamber at a neutral pressure of 3-10 Torr, and the x-rays produced in the Pb ionize and heat the Xe to a charge state of 20±4 at up to 200 eV electron temperatures.

Mapping Thermal Expansion Coefficients in Freestanding 2D Materials at the Nanometer Scale

NASA Astrophysics Data System (ADS)

Hu, Xuan; Yasaei, Poya; Jokisaari, Jacob; Öǧüt, Serdar; Salehi-Khojin, Amin; Klie, Robert F.

2018-02-01

Two-dimensional materials, including graphene, transition metal dichalcogenides and their heterostructures, exhibit great potential for a variety of applications, such as transistors, spintronics, and photovoltaics. While the miniaturization offers remarkable improvements in electrical performance, heat dissipation and thermal mismatch can be a problem in designing electronic devices based on two-dimensional materials. Quantifying the thermal expansion coefficient of 2D materials requires temperature measurements at nanometer scale. Here, we introduce a novel nanometer-scale thermometry approach to measure temperature and quantify the thermal expansion coefficients in 2D materials based on scanning transmission electron microscopy combined with electron energy-loss spectroscopy to determine the energy shift of the plasmon resonance peak of 2D materials as a function of sample temperature. By combining these measurements with first-principles modeling, the thermal expansion coefficients (TECs) of single-layer and freestanding graphene and bulk, as well as monolayer MoS2 , MoSe2 , WS2 , or WSe2 , are directly determined and mapped.

Mapping Thermal Expansion Coefficients in Freestanding 2D Materials at the Nanometer Scale.

PubMed

Hu, Xuan; Yasaei, Poya; Jokisaari, Jacob; Öğüt, Serdar; Salehi-Khojin, Amin; Klie, Robert F

2018-02-02

Two-dimensional materials, including graphene, transition metal dichalcogenides and their heterostructures, exhibit great potential for a variety of applications, such as transistors, spintronics, and photovoltaics. While the miniaturization offers remarkable improvements in electrical performance, heat dissipation and thermal mismatch can be a problem in designing electronic devices based on two-dimensional materials. Quantifying the thermal expansion coefficient of 2D materials requires temperature measurements at nanometer scale. Here, we introduce a novel nanometer-scale thermometry approach to measure temperature and quantify the thermal expansion coefficients in 2D materials based on scanning transmission electron microscopy combined with electron energy-loss spectroscopy to determine the energy shift of the plasmon resonance peak of 2D materials as a function of sample temperature. By combining these measurements with first-principles modeling, the thermal expansion coefficients (TECs) of single-layer and freestanding graphene and bulk, as well as monolayer MoS_{2}, MoSe_{2}, WS_{2}, or WSe_{2}, are directly determined and mapped.

Anharmonic Thermal Oscillations of the Electron Momentum Distribution in Lithium Fluoride

NASA Astrophysics Data System (ADS)

Erba, A.; Maul, J.; Itou, M.; Dovesi, R.; Sakurai, Y.

2015-09-01

Anharmonic thermal effects on the electron momentum distribution of a lithium fluoride single crystal are experimentally measured through high-resolution Compton scattering and theoretically modeled with ab initio simulations, beyond the harmonic approximation to the lattice potential, explicitly accounting for thermal expansion. Directional Compton profiles are measured at two different temperatures, 10 and 300 K, with a high momentum space resolution (0.10 a.u. in full width at half maximum), using synchrotron radiation. The effect of temperature on measured directional Compton profiles is clearly revealed by oscillations extending almost up to |p |=4 a .u . , which perfectly match those predicted from quantum-mechanical simulations. The wave-function-based Hartree-Fock method and three classes of the Kohn-Sham density functional theory (local-density, generalized-gradient, and hybrid approximations) are adopted. The lattice thermal expansion, as described with the quasiharmonic approach, is found to entirely account for the effect of temperature on the electron momentum density within the experimental accuracy.

Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giri, Ashutosh; Hopkins, Patrick E., E-mail: phopkins@virginia.edu

2015-12-07

Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot bemore » accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states.« less

Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Si, M. S.; Gao, Daqiang, E-mail: gaodq@lzu.edu.cn, E-mail: xueds@lzu.edu.cn; Yang, Dezheng

2014-05-28

Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstratemore » such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.« less

Development of Simple Designs of Multitip Probe Diagnostic Systems for RF Plasma Characterization

PubMed Central

Naz, M. Y.; Shukrullah, S.; Ghaffar, A.; Rehman, N. U.

2014-01-01

Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures. PMID:24683326

Methods and apparatus for cooling electronics

DOEpatents

Hall, Shawn Anthony; Kopcsay, Gerard Vincent

2014-12-02

Methods and apparatus are provided for choosing an energy-efficient coolant temperature for electronics by considering the temperature dependence of the electronics' power dissipation. This dependence is explicitly considered in selecting the coolant temperature T.sub.0 that is sent to the equipment. To minimize power consumption P.sub.Total for the entire system, where P.sub.Total=P.sub.0+P.sub.Cool is the sum of the electronic equipment's power consumption P.sub.0 plus the cooling equipment's power consumption P.sub.Cool, P.sub.Total is obtained experimentally, by measuring P.sub.0 and P.sub.Cool, as a function of three parameters: coolant temperature T.sub.0; weather-related temperature T.sub.3 that affects the performance of free-cooling equipment; and computational state C of the electronic equipment, which affects the temperature dependence of its power consumption. This experiment provides, for each possible combination of T.sub.3 and C, the value T.sub.0* of T.sub.0 that minimizes P.sub.Total. During operation, for any combination of T.sub.3 and C that occurs, the corresponding optimal coolant temperature T.sub.0* is selected, and the cooling equipment is commanded to produce it.

Low-temperature electronic transport in single K(0.27)MnO(2)·0.5H(2)O nanowires: enhanced electron-electron interaction.

PubMed

Long, Y Z; Yin, Z H; Chen, Z J; Jin, A Z; Gu, C Z; Zhang, H T; Chen, X H

2008-05-28

The current-voltage (I-V) characteristics and electrical resistivity of isolated potassium manganese oxide (K(0.27)MnO(2)·0.5H(2)O) nanowires prepared by a simple hydrothermal method were investigated over a wide temperature range from 300 to 4 K. With lowering temperature, a transition from linear to nonlinear I-V curves was observed around 50 K, and a clear zero bias anomaly (i.e., Coulomb gap-like structure) appeared on the differential conductance (dI/dV) curves, possibly due to enhanced electron-electron interaction at low temperatures. The temperature dependence of resistivity, [Formula: see text], follows the Efros-Shklovskii (ES) law, as expected in the presence of a Coulomb gap. Here we note that both the ES law and Coulomb blockade can in principle lead to a reduced zero bias conductance at low temperatures; in this study we cannot exclude the possibility of Coulomb-blockade transport in the measured nanowires, especially in the low-temperature range. It is still an open question how to pin down the origin of the observed reduction to a Coulomb gap (ES law) or Coulomb blockade.

DOE Office of Scientific and Technical Information (OSTI.GOV)

St Lishev, Stiliyan; Shivarova, Antonia P.

The study combines experiments on probe diagnostics with laser-photodetachment-technique and Faraday-cup measurements directed towards determination of the position of the extraction device and its influence on the discharge structure. The measurements have been carried out in the second chamber of an inductively-driven tandem plasma source performed as small scale arrangements, with a magnetic filter located just after the transition between the two chambers of the source. Results for the axial profiles of the plasma parameters display the correlation of the ratio n lowbar /n{sub e} of the densities of the negative hydrogen ions and of the electrons and of themore » concentration of the negative ions with the electron density and temperature: The maxima of the (n lowbar /n{sub e})-ratio and of the density of the negative ions obtained are located at the position of maximum of the electron density behind the filter, in the region of the low electron temperature. Results from probe diagnostics and laser photodetachment measurements at a given axial position for different positions of the Faraday cup show the changes in the spatial distribution of the electron density and temperature and the reduction of the (n lowbar /n{sub e})-ratio and of the density of the negative ions caused by the extraction device.« less

Ionospheric Measurements Using Environmental Sampling Techniques

NASA Technical Reports Server (NTRS)

Bourdeau, R. E.; Jackson, J. E.; Kane, J. A.; Serbu, G. P.

1960-01-01

Two rockets were flown to peak altitudes of 220 km in September 1959 to test various methods planned for future measurements of ionization parameters in the ionosphere, exosphere, and interplanetary plasma. The experiments used techniques which sample the ambient environment in the immediate vicinity of the research vehicle. Direct methods were chosen since indirect propagation techniques do not provide the temperatures of charged particles, are insensitive to ion densities, and cannot measure local electron densities under all conditions. Very encouraging results have been obtained from a preliminary analysis of data provided by one of the two flights. A new rf probe technique was successfully used to determine the electron density profile. This was indicated by its agreement with the results of a companion cw propagation experiment, particularly when the probe data were corrected for the effects of the ion sheath which surrounds the vehicle. The characteristics of this sheath were determined directly in flight by an electric field meter which provided the sheath field, and by a Langmuir probe which measured the total potential across the sheath. The electron temperatures deduced from the Langmuir probe data are greater than the neutral gas temperatures previously measured for the same location and season, but these measurements possibly were taken under different atmospheric conditions. Ion densities were calculated from the ion trap data for several altitudes ranging from 130 to 210 km and were found to be within 20 percent of the measured electron densities.

Ion and electron sheath characteristics in a low density and low temperature plasma

NASA Astrophysics Data System (ADS)

Borgohain, Binita; Bailung, H.

2017-11-01

Ion and electron sheath characteristics in a low electron temperature (Te ˜ 0.25-0.40 eV) and density (ne ˜ 106-107 cm-3) plasma are described. The plasma is produced in the experimental volume through diffusion from a hot cathode discharge plasma source by using a magnetic filter. The electron energy distribution function in the experimental plasma volume is measured to be a narrow Maxwellian distribution indicating the absence of primary and energetic electrons which are decoupled in the source side by the cusp magnetic field near the filter. An emissive probe is used to measure the sheath potential profiles in front of a metal plate biased negative and positive with respect to the plasma potential. For a positive plate bias, the electron density decreases considerably and the electron sheath expands with a longer presheath region compared to the ion sheath. The sheath potential structures are found to follow the Debye sheath model.

Photosynthesis and Photosynthetic Electron Flow in the Alpine Evergreen Species Quercus guyavifolia in Winter

PubMed Central

Huang, Wei; Hu, Hong; Zhang, Shi-Bao

2016-01-01

Alpine evergreen broadleaf tree species must regularly cope with low night temperatures in winter. However, the effects of low night temperatures on photosynthesis in alpine evergreen broadleaf tree species are unclear. We measured the diurnal photosynthetic parameters before and after cold snap for leaves of Quercus guyavifolia growing in its native habitat at 3290 m. On 11 and 12 December 2013 (before cold snap), stomatal and mesophyll conductances (gs and gm), CO2 assimilation rate (An), and total electron flow through PSII (JPSII) at daytime were maintained at high levels. The major action of alternative electron flow was to provide extra ATP for primary metabolisms. On 20 December 2013 (after cold snap), the diurnal values of gs, gm, An, and JPSII at daytime largely decreased, mainly due to the large decrease in night air temperature. Meanwhile, the ratio of photorespiration and alternative electron flow to JPSII largely increased on 20 December. Furthermore, the high levels of alternative electron flow were accompanied with low rates of extra ATP production. A quantitative limitation analysis reveals that the gm limitation increased on 20 December with decreased night air temperature. Therefore, the night air temperature was an important determinant of stomatal/mesophyll conductance and photosynthesis. When photosynthesis is inhibited following freezing night temperatures, photorespiration and alternative electron flow are important electron sinks, which support the role of photorespiration and alternative electron flow in photoportection for alpine plants under low temperatures. PMID:27812359

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klem, Michael

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory seeks to achieve thermonuclear ignition through inertial confinement fusion. The accurate assessment of the performance of each implosion experiment is a crucial step. Here we report on work to derive a reliable electron temperature for the cryogenic deuteriumtritium implosions completed on the NIF using the xray signal from the Ross filter diagnostic. These Xrays are dominated by bremsstrahlung emission. By fitting the xray signal measured through each of the individual Ross filters, the source bremsstrahlung spectrum can be inferred, and an electron temperature of the implosion hot spot inferred.more » Currently, each filter is weighted equally in this analysis. We present work quantifying the errors with such a technique and the results from investigating the contribution of each filter to the overall accuracy of the temperature inference. Using this research, we also compare the inferred electron temperature against other measured implosion quantities to develop a more complete understanding of the hotspot physics.« less

Validations of calibration-free measurements of electron temperature using double-pass Thomson scattering diagnostics from theoretical and experimental aspects.

PubMed

Tojo, H; Yamada, I; Yasuhara, R; Ejiri, A; Hiratsuka, J; Togashi, H; Yatsuka, E; Hatae, T; Funaba, H; Hayashi, H; Takase, Y; Itami, K

2016-09-01

This paper evaluates the accuracy of electron temperature measurements and relative transmissivities of double-pass Thomson scattering diagnostics. The electron temperature (T e ) is obtained from the ratio of signals from a double-pass scattering system, then relative transmissivities are calculated from the measured T e and intensity of the signals. How accurate the values are depends on the electron temperature (T e ) and scattering angle (θ), and therefore the accuracy of the values was evaluated experimentally using the Large Helical Device (LHD) and the Tokyo spherical tokamak-2 (TST-2). Analyzing the data from the TST-2 indicates that a high T e and a large scattering angle (θ) yield accurate values. Indeed, the errors for scattering angle θ = 135° are approximately half of those for θ = 115°. The method of determining the T e in a wide T e range spanning over two orders of magnitude (0.01-1.5 keV) was validated using the experimental results of the LHD and TST-2. A simple method to provide relative transmissivities, which include inputs from collection optics, vacuum window, optical fibers, and polychromators, is also presented. The relative errors were less than approximately 10%. Numerical simulations also indicate that the T e measurements are valid under harsh radiation conditions. This method to obtain T e can be considered for the design of Thomson scattering systems where there is high-performance plasma that generates harsh radiation environments.

Measurements of the structure of an ionizing shock wave in a hydrogen-helium mixture

NASA Technical Reports Server (NTRS)

Leibowitz, L. P.

1972-01-01

Shock structure during ionization of a hydrogen-helium mixture was studied using hydrogen line and continuum emission measurements. A reaction scheme is proposed which includes hydrogen dissociation and a two-step excitation-ionization mechanism for hydrogen ionization by atom-atom and atom-electron collisions. Agreement was achieved between numerical calculations and measurements of emission intensity as a function of time for shock velocities from 13 to 20 km/sec in a 0.208 H2 - 0.792 He mixture. The electron temperature was found to be significantly different from the heavy particle temperature during much of the ionization process. Similar time histories for H beta and continuum emission indicate upper level populations of hydrogen in equilibrium with the electron concentration during the relaxation process.

Measurements of the structure of an ionizing shock wave in a hydrogen-helium mixture.

NASA Technical Reports Server (NTRS)

Leibowitz, L. P.

1973-01-01

Shock structure during ionization of a hydrogen-helium mixture has been followed using hydrogen line and continuum emission measurements. A reaction scheme is proposed which includes hydrogen dissociation and a two-step excitation-ionization mechanism for hydrogen ionization by atom-atom and atom-electron collisions. Agreement has been achieved between numerical calculations and measurements of emission intensity as a function of time for shock velocities from 13 to 20 km/sec in a 0.208 H2-0.792 He mixture. The electron temperature was found to be significantly different from the heavy particle temperature during much of the ionization process. Similar time histories for H beta and continuum emission indicate upper level populations of hydrogen in equilibrium with the electron concentration during the relaxation process.

Radar and photometric measurements of an intense type A red aurora

NASA Technical Reports Server (NTRS)

Robinson, R. M.; Mende, S. B.; Vondrak, R. R.; Kozyra, J. U.; Nagy, A. F.

1985-01-01

On the evening of March 5, 1981, an intense, type A red aurora appeared over southern Alaska. Radar and photometric measurements were made of the aurora from the Chatanika radar site. The line of sight intensity of the 630.0-nm emissions exceeded 150 kR and was accompanied by enhanced emissions at 486.1 and 427.8 nm. The Chatanika radar measured electron densities of 10 to the 6th per cu cm and electron temperatures of 6000 K at an altitude of 400 km and an invariant latitude of 59 deg in association with the aurora. Comparison of optical and radar measurements indicated that the 630.0-nm emissions were produced to a large degree by thermal excitation of O(1D) in the region of high electron temperatures and densities. Model calculations indicate that the observed density and temperature enhancements and the related optical emissions were the results of a relatively short duration (5-10 min) pulse of precipitating, low-energy (about 30 eV) electrons. Whereas conventional stable auroral red arcs are associated with a gradual decrease in ring current energy density during the recovery phase of a magnetic storm, the type A red aurora may be produced by impulsive ring current energy loss during the main phase.

Ultrafast Gap Dynamics and Electronic Interactions in a Photoexcited Cuprate Superconductor

DOE PAGES

Parham, S.; Li, H.; Nummy, T. J.; ...

2017-10-20

We perform time- and angle-resolved photoemission spectroscopy (trARPES) on optimally doped Bi 2Sr 2CaCu 2O 8+δ (BSCCO-2212) using sufficient energy resolution (9 meV) to resolve the k-dependent near-nodal gap structure on time scales where the concept of an electronic pseudotemperature is a useful quantity, i.e., after electronic thermalization has occurred. We study the ultrafast evolution of this gap structure, uncovering a very rich landscape of decay rates as a function of angle, temperature, and energy. We explicitly focus on the quasiparticle states at the gap edge as well as on the spectral weight inside the gap that “fills” the gap—understoodmore » as an interaction, or self-energy effect—and we also make high resolution measurements of the nodal states, enabling a direct and accurate measurement of the electronic temperature (or pseudotemperature) of the electrons in the system. Rather than the standard method of interpreting these results using individual quasiparticle scattering rates that vary significantly as a function of angle, temperature, and energy, we show that the entire landscape of relaxations can be understood by modeling the system as following a nonequilibrium, electronic pseudotemperature that controls all electrons in the zone. Furthermore, this model has zero free parameters, as we obtain the crucial information of the SC gap Δ and the gap-filling strength Γ TDoS by connecting to static ARPES measurements. The quantitative and qualitative agreement between data and model suggests that the critical parameters and interactions of the system, including the pairing interactions, follow parametrically from the electronic pseudotemperature. In conclusion, we expect that this concept will be relevant for understanding the ultrafast response of a great variety of electronic materials, even though the electronic pseudotemperature may not be directly measurable.« less

Ultrafast Gap Dynamics and Electronic Interactions in a Photoexcited Cuprate Superconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parham, S.; Li, H.; Nummy, T. J.

We perform time- and angle-resolved photoemission spectroscopy (trARPES) on optimally doped Bi 2Sr 2CaCu 2O 8+δ (BSCCO-2212) using sufficient energy resolution (9 meV) to resolve the k-dependent near-nodal gap structure on time scales where the concept of an electronic pseudotemperature is a useful quantity, i.e., after electronic thermalization has occurred. We study the ultrafast evolution of this gap structure, uncovering a very rich landscape of decay rates as a function of angle, temperature, and energy. We explicitly focus on the quasiparticle states at the gap edge as well as on the spectral weight inside the gap that “fills” the gap—understoodmore » as an interaction, or self-energy effect—and we also make high resolution measurements of the nodal states, enabling a direct and accurate measurement of the electronic temperature (or pseudotemperature) of the electrons in the system. Rather than the standard method of interpreting these results using individual quasiparticle scattering rates that vary significantly as a function of angle, temperature, and energy, we show that the entire landscape of relaxations can be understood by modeling the system as following a nonequilibrium, electronic pseudotemperature that controls all electrons in the zone. Furthermore, this model has zero free parameters, as we obtain the crucial information of the SC gap Δ and the gap-filling strength Γ TDoS by connecting to static ARPES measurements. The quantitative and qualitative agreement between data and model suggests that the critical parameters and interactions of the system, including the pairing interactions, follow parametrically from the electronic pseudotemperature. In conclusion, we expect that this concept will be relevant for understanding the ultrafast response of a great variety of electronic materials, even though the electronic pseudotemperature may not be directly measurable.« less

Thermoluminescent response of LiF:Mg,Ti to 20 keV electrons.

PubMed

Mercado-Uribe, H; Brandan, M E

2002-01-01

The thermoluminescence response of LiF:Mg,Ti (TLD-100) to 20 keV electrons from a scanning electron microscope has been measured. Radiochromic dye films previously calibrated were used to determine the fluence incident on TLD-100 chips. The procedure for irradiation and glow curve deconvolution was adhered to the protocols previously determined in our laboratory for gamma rays and heavy charged particles. The response at electron fluences higher than 4 x 10(10) cm(-2) is supralinear, due to the increasingly relevant contribution of the high temperature peaks. The relative contribution of the high temperature peaks to the TL signal is abnormally small, about half that observed in gamma irradiation and four times smaller than what has been measured in low-energy X ray exposure.

The spatial effect of protein deuteration on nitroxide spin-label relaxation: Implications for EPR distance measurement

PubMed Central

El Mkami, Hassane; Ward, Richard; Bowman, Andrew; Owen-Hughes, Tom; Norman, David G.

2014-01-01

Pulsed electron–electron double resonance (PELDOR) coupled with site-directed spin labeling is a powerful technique for the elucidation of protein or nucleic acid, macromolecular structure and interactions. The intrinsic high sensitivity of electron paramagnetic resonance enables measurement on small quantities of bio-macromolecules, however short relaxation times impose a limit on the sensitivity and size of distances that can be measured using this technique. The persistence of the electron spin-echo, in the PELDOR experiment, is one of the most crucial limitations to distance measurement. At a temperature of around 50 K one of the predominant factors affecting persistence of an echo, and as such, the sensitivity and measurable distance between spin labels, is the electron spin echo dephasing time (Tm). It has become normal practice to use deuterated solvents to extend Tm and recently it has been demonstrated that deuteration of the underlying protein significantly extends Tm. Here we examine the spatial effect of segmental deuteration of the underlying protein, and also explore the concentration and temperature dependence of highly deuterated systems. PMID:25310878

Temperature dependence of the hydrated electron's excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

NASA Astrophysics Data System (ADS)

Farr, Erik P.; Zho, Chen-Chen; Challa, Jagannadha R.; Schwartz, Benjamin J.

2017-08-01

The structure of the hydrated electron, particularly whether it exists primarily within a cavity or encompasses interior water molecules, has been the subject of much recent debate. In Paper I [C.-C. Zho et al., J. Chem. Phys. 147, 074503 (2017)], we found that mixed quantum/classical simulations with cavity and non-cavity pseudopotentials gave different predictions for the temperature dependence of the rate of the photoexcited hydrated electron's relaxation back to the ground state. In this paper, we measure the ultrafast transient absorption spectroscopy of the photoexcited hydrated electron as a function of temperature to confront the predictions of our simulations. The ultrafast spectroscopy clearly shows faster relaxation dynamics at higher temperatures. In particular, the transient absorption data show a clear excess bleach beyond that of the equilibrium hydrated electron's ground-state absorption that can only be explained by stimulated emission. This stimulated emission component, which is consistent with the experimentally known fluorescence spectrum of the hydrated electron, decreases in both amplitude and lifetime as the temperature is increased. We use a kinetic model to globally fit the temperature-dependent transient absorption data at multiple temperatures ranging from 0 to 45 °C. We find the room-temperature lifetime of the excited-state hydrated electron to be 137 ±40 fs, in close agreement with recent time-resolved photoelectron spectroscopy (TRPES) experiments and in strong support of the "non-adiabatic" picture of the hydrated electron's excited-state relaxation. Moreover, we find that the excited-state lifetime is strongly temperature dependent, changing by slightly more than a factor of two over the 45 °C temperature range explored. This temperature dependence of the lifetime, along with a faster rate of ground-state cooling with increasing bulk temperature, should be directly observable by future TRPES experiments. Our data also suggest that the red side of the hydrated electron's fluorescence spectrum should significantly decrease with increasing temperature. Overall, our results are not consistent with the nearly complete lack of temperature dependence predicted by traditional cavity models of the hydrated electron but instead agree qualitatively and nearly quantitatively with the temperature-dependent structural changes predicted by the non-cavity hydrated electron model.

Evaluation of in vivo dose measurements for patients undergoing electron boost treatments.

PubMed

Verney, J N; Morgan, A M

2001-06-01

This study evaluated p-type silicon diodes for use in in vivo dosimetry in clinical electron beams. A calibrated p-type silicon diode detector was used to measure the dose received by the patient in the centre of the field. Readings were corrected for energy, temperature and stand-off of the electron applicator from the patient surface. The mean difference between measured and prescribed dose was 1.04% (95% CI 0.72 to 1.36 %).

Defects and Transport in Lithium Niobium Trioxide

NASA Astrophysics Data System (ADS)

Mehta, Apurva

1990-01-01

This dissertation presents work done on characterizing the defects and transport properties of congruent LiNbO _3. The focus of the study is the high temperature (800^circC to 1000^circC) equilibrium defect structure. The majority defects are described in terms of the 'LiNbO_3-ilmenite' defect model previously presented (26). Here the emphasis is placed on quantifying the defect concentrations. Congruent LiNbO_3 is highly nonstoichiometric. The large concentration of ionic defects present are mobile and contribute to electrical conduction. The ionic conduction was separated from the total conduction using defect chemistry and the transference number thus obtained was checked against the transference number obtained in a galvanic cell measurement. LiNbO_3 is an insulator (band gap = 4 eV). Hence one assumes that almost all of the conduction electrons are created by reduction. The degree of oxygen nonstoichiometry, a measure of the extent of chemical reduction, and the electron concentrations, were quantified as a function of oxygen partial pressure and the temperature by coulometric titration. The nonstoichiometry thus obtained was compared with nonstoichiometry obtained by TGA measurements. By fixing the phase composition of the sample in a buffered system, a set of constant composition measurements could be undertaken. These constant composition measurements were used to obtain the enthalpy of formation of conduction electrons, 1.95 eV, and the hopping energy for their motion at elevated temperatures, 0.55 eV, independently. The sum of the two energies was obtained by measuring the temperature dependence of the electronic conduction. The sum of the energies was found to be in excellent agreement with the energy obtained from equilibrium conduction. In conclusion, a quantitative and self-consistent picture of defects and their migration in LiNbO _3 was obtained.

Phonon exchange by two-dimensional electrons in intermediate magnetic fields

NASA Astrophysics Data System (ADS)

Gopalakrishnan, Gokul

The discovery of the integer and fractional quantum Hall effects have broadened the exploration of the two-dimensional electron gas to regimes where complex and exciting physics lay previously hidden. While many experimental investigations have focused on the regime of large magnetic fields where transport properties are determined by contributions from a single Landau level, the regime of intermediate fields, where multiple Landau levels are involved, has been much less explored. This dissertation is a report on a previously unobserved interaction probed by a novel type of magneto-transport measurement performed in this intermediate regime, in bilayer two-dimensional electron systems. This measurement technique, known as electron drag, directly measures interlayer electron-electron scattering rates, by measuring the voltage induced in one of the layers when a current is driven through the other. The scattering mechanism, which may be Coulomb or phonon mediated, depends critically on both the separation between the layers and the electron density. When electron drag is measured in the presence of a perpendicular magnetic field in suitable samples, the resulting magnetodrag signal reveals new information about the electronic states as well as properties of a phonon mediated scattering mechanism. This phonon scattering mechanism is reflected in previously unobserved oscillations. These oscillations, which are periodic in the inverse field, are argued to arise from a resonant interlayer exchange of 2 kF phonons. Measurements of the temperature, density and layer-spacing dependences of magnetodrag resistivity are reported and are shown to confirm this particular mechanism. Additionally, analysis of the temperature dependence reveals a strong sensitivity to Landau level widths. Based on this analysis, a means of characterizing the broadening of Landau levels and hence, electronic lifetimes in this regime, which are otherwise difficult to characterize, is proposed.

Single Crystal Diamond Needle as Point Electron Source

PubMed Central

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-01-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2–0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics. PMID:27731379

Thermoluminescent response of TLD-100 irradiated with 20 keV electrons and the use of radiochromic dye films for the fluence determination

NASA Astrophysics Data System (ADS)

Mercado-Uribe, H.; Brandan, M. E.

2004-07-01

We have measured the LiF:Mg,Ti (TLD-100) fluence response and supralinearity function to 20 keV electrons in the fluence interval between 5 × 10 9 and 4 × 10 12 cm -2. TLD-100 shows linear response up to 2 × 10 10 cm -2, followed by supralinearity and saturation after 10 12 cm -2. Peak 5 is slightly supralinear, f( n) max=1.1±0.1, while high temperature peaks reach up to f( n) max≈8. Peak 5 saturates at n≈1×10 11 cm -2, fluence smaller than any of the saturating fluences of the high temperature peaks. We have also measured the glow curve shape of TLD-100 irradiated with 40 keV electrons, beta particles from a 90Sr/ 90Y source and 1.3 and 6.0 MeV electrons from accelerators. Results are interesting and unexpected in that, for a given macroscopic dose, electrons show a smaller relative contribution of high-temperature peaks with respect to peak 5 than heavy ions or X- and γ-rays. The 20 and 40 keV electron irradiations were performed with a scanning electron microscope using radiochromic dye film to measure fluence. Since film calibrations were performed using 60Co γ-rays which expose the totality of the film volume, the use of this method with low energy electrons required to develop a formalism that takes into account the sensitive thickness of the film in relation to the range of the incident particles.

Intramolecular electron-transfer rates in mixed-valence triarylamines: measurement by variable-temperature ESR spectroscopy and comparison with optical data.

PubMed

Lancaster, Kelly; Odom, Susan A; Jones, Simon C; Thayumanavan, S; Marder, Seth R; Brédas, Jean-Luc; Coropceanu, Veaceslav; Barlow, Stephen

2009-02-11

The electron spin resonance spectra of the radical cations of 4,4'-bis[di(4-methoxyphenyl)amino]tolane, E-4,4'-bis[di(4-methoxyphenyl)amino]stilbene, and E,E-1,4-bis{4-[di(4-methoxyphenyl)amino]styryl}benzene in dichloromethane exhibit five lines over a wide temperature range due to equivalent coupling to two 14N nuclei, indicating either delocalization between both nitrogen atoms or rapid intramolecular electron transfer on the electron spin resonance time scale. In contrast, those of the radical cations of 1,4-bis{4-[di(4-methoxyphenyl)amino]phenylethynyl}benzene and E,E-1,4-bis{4-[di(4-n-butoxyphenyl)amino]styryl}-2,5-dicyanobenzene exhibit line shapes that vary strongly with temperature, displaying five lines at room temperature and only three lines at ca. 190 K, indicative of slow electron transfer on the electron spin resonance time scale at low temperatures. The rates of intramolecular electron transfer in the latter compounds were obtained by simulation of the electron spin resonance spectra and display an Arrhenius temperature dependence. The activation barriers obtained from Arrhenius plots are significantly less than anticipated from Hush analyses of the intervalence bands when the diabatic electron-transfer distance, R, is equated to the N[symbol: see text]N distance. Comparison of optical and electron spin resonance data suggests that R is in fact only ca. 40% of the N[symbol: see text]N distance, while the Arrhenius prefactor indicates that the electron transfer falls in the adiabatic regime.

Redox activity distinguishes solid-state electron transport from solution-based electron transfer in a natural and artificial protein: cytochrome C and hemin-doped human serum albumin.

PubMed

Amdursky, Nadav; Ferber, Doron; Pecht, Israel; Sheves, Mordechai; Cahen, David

2013-10-28

Integrating proteins in molecular electronic devices requires control over their solid-state electronic transport behavior. Unlike "traditional" electron transfer (ET) measurements of proteins that involve liquid environments and a redox cycle, no redox cofactor is needed for solid-state electron transport (ETp) across the protein. Here we show the fundamental difference between these two approaches by macroscopic area measurements, which allow measuring ETp temperature dependence down to cryogenic temperatures, via cytochrome C (Cyt C), an ET protein with a heme (Fe-porphyrin) prosthetic group as a redox centre. We compare the ETp to electrochemical ET measurements, and do so also for the protein without the Fe (with metal-free porphyrin) and without porphyrin. As removing the porphyrin irreversibly alters the protein's conformation, we repeat these measurements with human serum albumin (HSA), 'doped' (by non-covalent binding) with a single hemin equivalent, i.e., these natural and artificial proteins share a common prosthetic group. ETp via Cyt C and HSA-hemin are very similar in terms of current magnitude and temperature dependence, which suggests similar ETp mechanisms via these two systems, thermally activated hopping (with ~0.1 eV activation energy) >190 K and tunneling by superexchange <190 K. Also, ET rates to and from the Fe redox centres (Fe(2+) <=> Fe(3+) + e(-)), measured by electrochemistry of HSA-hemin are only 4 times lower than those for Cyt C. However, while removing the Fe redox centre from the porphyrin ring markedly affects the ET rate, it hardly changes the ETp currents through these proteins, while removing the macrocycle (from HSA, which retains its conformation) significantly reduces ETp efficiency. These results show that solid-state ETp across proteins does not require the presence of a redox cofactor, and that while for ET the Fe ion is the main electron mediator, for ETp the porphyrin ring has this function.

A Michelson Interferometer for Electron Cyclotron Emission Measurements on EAST

NASA Astrophysics Data System (ADS)

Liu, Yong; Stefan, Schmuck; Zhao, Hailin; John, Fessey; Paul, Trimble; Liu, Xiang; Zhu, Zeying; Zang, Qing; Hu, Liqun

2016-12-01

A Michelson interferometer, on loan from EFDA-JET (Culham, United Kingdom) has recently been commissioned on the experimental advanced superconducting tokamak (EAST, ASIPP, Hefei, China). Following a successful in-situ absolute calibration the instrument is able to measure the electron cyclotron emission (ECE) spectrum, from 80 GHz to 350 GHz in extraordinary mode (X-mode) polarization, with high accuracy. This allows the independent determination of the electron temperature profile from observation of the second harmonic ECE and the possible identification of non-Maxwellian features by comparing higher harmonic emission with numerical simulations. The in-situ calibration results are presented together with the initial measured temperature profiles. These measurements are then discussed and compared with other independent temperature profile measurements. This paper also describes the main hardware features of the diagnostic and the associated commissioning test results. supported by National Natural Science Foundation of China (Nos. 11405211, 11275233), and the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB106002, 2015GB101000), and the RCUK Energy Programme (No. EP/I501045), partly supported by the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics (NSFC: No. 11261140328)

[Comparison of different methods of temperature measurment in children].

PubMed

Pavlović, Momcilo; Radlović, Nedeljko; Leković, Zoran; Berenji, Karolina

2008-01-01

The consequences of failing to notice fever in children can be serious. On the other hand, false positive reading can result in unnecesery investigation or diagnostic approach. The aim of this study was to compare different ways of body temperature measurement. This prospective study was carried out on Pediatric Department of General Hospital in Subotica during 10 months (March-December 2006). In 263 children aged 1 month to 18 years of age, the body temperature was obtained from 4 measurement sites: tactile assesment, forehead and ear by electronic thermometer, rectal temperature in small children (up to 2 years of age) or axillar temperature in older children by mercury thermometer. Tympanic thermometry was considered as a standard for fever detection. The sensitivity of rectal temperature to detect fever is 46.67%, while specificity is 92.19%. The sensitivity of fever detection by electronic thermometry on the forehead is lower according to rectal thermometry - 36.08%, while specificity is 95.18%. The lowest values ofsensitivity are recorded in axillar thermometry (35.82%), specificity is 90.20%. The correlation coefficient is higher between tympanic and rectal temperature measurement (r=0.5076, p<0.0005), than between tympanic and forehead measurements (r=0.5076, p<0,0005), while the lowest was between tympanic and axillar mesurement sites (r=0.4933, p<0.0005). The results of our study and literature data show that the most accurate methods of thermometry are rectal measurement of body temperature in small children and tympanic thermometry in children over 2 years of age.

Optical diagnostics with radiation trapping effect in low density and low temperature helium plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Wonwook, E-mail: wwlee@kaeri.re.kr; Kwon, Duck-Hee; Park, Kyungdeuk

2016-06-15

Low density (n{sub e} < 10{sup 11 }cm{sup −3}) and low temperature (T{sub e} < 10 eV) helium plasma was generated by hot filament discharge. Electron temperature and density of neutral helium plasma were measured by Langmuir probe and were determined by line intensity ratio method using optical emission spectroscopy with population modelings. Simple corona model and collisional-radiative (CR) model without consideration for radiation trapping effect are applied. In addition, CR model taking into account the radiation trapping effect (RTE) is adopted. The change of single line intensity ratio as a function of electron temperature and density were investigated when the RTE is included and excluded.more » The changes of multi line intensity ratios as a function of electron temperature were scanned for various radiative-excitation rate coefficients from the ground state and the helium gas pressures related with the RTE. Our CR modeling with RTE results in fairly better agreement of the spectroscopic diagnostics for the plasma temperature or density with the Langmuir probe measurements for various helium gas pressures than corona modeling and CR modeling without RTE.« less

Comparative study of magnetic ordering in bulk and nanoparticles of Sm0.65Ca0.35MnO3: Magnetization and electron magnetic resonance measurements

NASA Astrophysics Data System (ADS)

Goveas, Lora Rita; Anuradha, K. N.; Bhagyashree, K. S.; Bhat, S. V.

2015-05-01

To explore the effect of size reduction to nanoscale on the hole doped Sm0.65Ca0.35MnO3 compound, dc magnetic measurements and electron magnetic resonance (EMR) were done on bulk and nanoparticle samples in the temperature range 10 ≤ T ≤ 300 K. Magnetization measurement showed that the bulk sample undergoes a charge ordering transition at 240 K and shows a mixed magnetic phase at low temperature. However, the nanosample underwent a ferromagnetic transition at 75 K, and the charge ordered state was destabilized on size reduction down to nanoscale. The low-temperature ferromagnetic component is found to be enhanced in nanoparticles as compared to their bulk counterpart. Interestingly around room temperature, bulk particles show higher magnetization where as at low temperature nanoparticles show higher magnetization. Ferromagnetism in the bulk is due to super exchange where as ferromagnetism in nanoparticles is due to uncompensated spins of the surface layer. Temperature variation of EMR parameters correlates well with the results of magnetic measurements. The magnetic behaviour of the nanoparticles is understood in terms of the core shell scenario.

Electron and thermal transport via variable range hopping in MoSe2 single crystals

NASA Astrophysics Data System (ADS)

Suri, Dhavala; Patel, R. S.

2017-06-01

Bulk single crystal molybdenum diselenide has been studied for its electronic and thermal transport properties. We perform resistivity measurements with current in-plane (CIP) and current perpendicular to plane (CPP) as a function of temperature. The CIP measurements exhibit metal to semiconductor transition at ≃31 K. In the semiconducting phase (T > 31 K), the transport is best explained by the variable range hopping (VRH) model. Large magnitude of resistivity in the CPP mode indicates strong structural anisotropy. The Seebeck coefficient as a function of temperature measured in the range of 90-300 K also agrees well with the VRH model. The room temperature Seebeck coefficient is found to be 139 μV/K. VRH fittings of the resistivity and the Seebeck coefficient data indicate high degree of localization.

First measurement of time evolution of electron temperature profiles with Nd:YAG Thomson scattering system on Heliotron J

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenmochi, N., E-mail: kemmchi.naoki.62r@st.kyoto-u.ac.jp; Tei, S.; Zang, L.

2014-11-15

A Nd:YAG Thomson scattering system has been developed for Heliotron J. The system consists of two 550 mJ 50 Hz lasers, large collection optics, and 25 radial channel (∼1 cm spatial resolution) interference polychromators. This measurement system achieves a S/N ratio of ∼50 for low-density plasma (n{sub e} ∼ 0.5 × 10{sup 19} m{sup −3}). A time evolution of electron temperature profiles was measured with this system for a high-intensity gas-puff (HIGP) fueling neutral-beam-injection plasma. The peripheral temperature of the higher-density phase after HIGP recovers to the low-density pre-HIGP level, suggesting that improving particle transport in the HIGP plasma maymore » be possible.« less

Measurement of turbulent electron temperature fluctuations on the ASDEX Upgrade tokamak using correlated electron cyclotron emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freethy, S. J., E-mail: simon.freethy@ipp.mpg.de; Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; Conway, G. D.

2016-11-15

Turbulent temperature fluctuations are measured on the ASDEX Upgrade tokamak using pairs of closely spaced, narrow-band heterodyne radiometer channels and a standard correlation technique. The pre-detection spacing and bandwidth of the radiometer channel pairs is chosen such that they are physically separated less than a turbulent correlation length, but do not overlap. The radiometer has 4 fixed filter frequency channels and two tunable filter channels for added flexibility in the measurement position. Relative temperature fluctuation amplitudes are observed in a helium plasma to be δT/T = (0.76 ± 0.02)%, (0.67 ± 0.02)%, and (0.59 ± 0.03)% at normalised toroidal fluxmore » radius of ρ{sub tor} = 0.82, 0.75, and 0.68, respectively.« less

Measurement of the electron-impact transfer rate coefficients between the Kr(1s) states in an afterglow discharge

NASA Astrophysics Data System (ADS)

Qiu, Jie; Cheng, Zhi-Wen; Zhu, Xi-Ming; Pu, Yi-Kang

2018-04-01

The rate coefficients for the electron-impact transfer from Kr(1s5) to Kr(1s4) and from Kr(1s3) to Kr(1s2) are measured in the electron temperature (T e) range between 0.07 eV and 1 eV. In the afterglow of a capacitive krypton discharge at a fixed pressure of 20 mTorr and a peak rf power ranging from 4 to 128 W, the densities of four krypton 1s states, the electron temperature and the electron density are measured by diode laser absorption, a Langmuir probe and a microwave interferometer, respectively. With these measured quantities, the rate coefficients are obtained from a population model for krypton metastable states. The measured rate coefficients are compared with those derived from the excitation cross sections of Kr metastable states calculated by different R-matrix models. It is found that our results agree best with that from Allan et al [1]. Moreover, we analyze the assumptions made in the population model and discuss their possible impact on the accuracy of the measured rate coefficients, especially for the low T e (0.1-0.2 eV) range and a higher T e (0.4-1 eV) range.

High-precision measurement of the electron spin g factor of trapped atomic nitrogen in the endohedral fullerene N@C60

NASA Astrophysics Data System (ADS)

Wittmann, J. J.; Can, T. V.; Eckardt, M.; Harneit, W.; Griffin, R. G.; Corzilius, B.

2018-05-01

The electronic g factor carries highly useful information about the electronic structure of a paramagnetic species, such as spin-orbit coupling and dia- or paramagnetic (de-)shielding due to local fields of surrounding electron pairs. However, in many cases, a near "spin-only" case is observed, in particular for light elements, necessitating accurate and precise measurement of the g factors. Such measurement is typically impeded by a "chicken and egg situation": internal or external reference standards are used for relative comparison of electron paramagnetic resonance (EPR) Larmor frequencies. However, the g factor of the standard itself usually is subject to a significant uncertainty which directly limits the precision and/or accuracy of the sought after sample g factor. Here, we apply an EPR reference-free approach for determining the g factor of atomic nitrogen trapped within the endohedral fullerene C60:N@C60 in its polycrystalline state by measuring the 1H NMR resonance frequency of dispersing toluene at room temperature. We found a value of g = 2.00204 (4) with a finally reached relative precision of ∼20 ppm. This accurate measurement allows us to directly compare the electronic properties of N@C60 to those found in atomic nitrogen in the gas phase or trapped in other solid matrices at liquid helium temperature. We conclude that spin-orbit coupling in N@C60 at room temperature is very similar in magnitude and of same sign as found in other inert solid matrices and that interactions between the quartet spin system and the C60 molecular orbitals are thus negligible.

A collective scattering system for measuring electron gyroscale fluctuations on the National Spherical Torus Experiment.

PubMed

Smith, D R; Mazzucato, E; Lee, W; Park, H K; Domier, C W; Luhmann, N C

2008-12-01

A collective scattering system has been installed on the National Spherical Torus Experiment (NSTX) to measure electron gyroscale fluctuations in NSTX plasmas. The system measures fluctuations with k( perpendicular)rho(e) less, similar0.6 and k( perpendicular) less, similar20 cm(-1). Up to five distinct wavenumbers are measured simultaneously, and the large toroidal curvature of NSTX plasmas provides enhanced spatial localization. Steerable optics can position the scattering volume throughout the plasma from the magnetic axis to the outboard edge. Initial measurements indicate rich turbulent dynamics on the electron gyroscale. The system will be a valuable tool for investigating the connection between electron temperature gradient turbulence and electron thermal transport in NSTX plasmas.

Electron-temperature dependence of the recombination of H3O+(H2O)n ions with electrons

NASA Technical Reports Server (NTRS)

Johnsen, R.

1993-01-01

The T(e) dependence of the recombination of H3O+(H2O)n cluster-ions with electrons has been measured in an afterglow experiment in which the electrons were heated by a radio-frequency electric field. The recombination coefficients were found to vary with T(e) as about T(e) exp -1/2 in better agreement with theoretical expectations than earlier results of microwave-afterglow measurements.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biewer, Theodore M.; Bigelow, Tim S.; Caneses Marin, Juan F.

The Prototype Material Plasma Exposure Experiment at the Oak Ridge National Laboratory utilizes a variety of power systems to generate and deliver a high heat flux plasma onto the surface of material targets. In the experiments described here, a deuterium plasma is produced via a ~100 kW, 13.56 MHz RF helicon source, to which ~20 kW of 28 GHz microwave power is applied. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is centrally peaked. In the core of the plasma column, the electron density is higher than themore » cut-off density (~0.9 × 1019 m -3) for the launched mixture of X- and O-mode electron cyclotron heating waves to propagate. TS measurements indicate electron temperature increases from ~5 eV to ~20 eV during 28 GHz power application when the neutral deuterium pressure is reduced below 0.13 Pa (~1 mTorr.).« less

Perturbative tests of theoretical transport models using cold pulse and modulated electron cyclotron heating experiments

NASA Astrophysics Data System (ADS)

Kinsey, J. E.; Waltz, R. E.; DeBoo, J. C.

1999-05-01

It is difficult to discriminate between various tokamak transport models using standardized statistical measures to assess the goodness of fit with steady-state density and temperature profiles in tokamaks. This motivates consideration of transient transport experiments as a technique for testing the temporal response predicted by models. Results are presented comparing the predictions from the Institute for Fusion Studies—Princeton Plasma Physics Laboratory (IFS/PPPL), gyro-Landau-fluid (GLF23), Multi-mode (MM), Current Diffusive Ballooning Mode (CDBM), and Mixed-shear (MS) transport models against data from ohmic cold pulse and modulated electron cyclotron heating (ECH) experiments. In ohmically heated discharges with rapid edge cooling due to trace impurity injection, it is found that critical gradient models containing a strong temperature ratio (Ti/Te) dependence can exhibit behavior that is qualitatively consistent both spatially and temporally with experimental observation while depending solely on local parameters. On the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)], off-axis modulated ECH experiments have been conducted in L-mode (low confinement mode) and the perturbed electron and ion temperature response to multiple heat pulses has been measured across the plasma core. Comparing the predicted Fourier phase of the temperature perturbations, it is found that no single model yielded agreement with both electron and ion phases for all cases. In general, it was found that the IFS/PPPL, GLF23, and MS models agreed well with the ion response, but not with the electron response. The CDBM and MM models agreed well with the electron response, but not with the ion response. For both types of transient experiments, temperature coupling between the electron and ion transport is found to be an essential feature needed in the models for reproducing the observed perturbative response.

Prompt increase of ultrashort laser pulse transmission through thin silver films

NASA Astrophysics Data System (ADS)

Bezhanov, S. G.; Danilov, P. A.; Klekovkin, A. V.; Kudryashov, S. I.; Rudenko, A. A.; Uryupin, S. A.

2018-03-01

We study experimentally and numerically the increase in ultrashort laser pulse transmissivity through thin silver films caused by the heating of electrons. Low to moderate energy femtosecond laser pulse transmission measurements through 40-125 nm thickness silver films were carried out. We compare the experimental data with the values of transmitted fraction of energy obtained by solving the equations for the field together with the two-temperature model. The measured values were fitted with sufficient accuracy by varying the electron-electron collision frequency whose exact values are usually poorly known. Since transmissivity experiences more pronounced changes with the increase in temperature compared to reflectivity, we suggest this technique for studying the properties of nonequilibrium metals.

Spatially resolved measurements of two-dimensional turbulent structures in DIII-D plasmas

DOE PAGES

Zemedkun, Samuel E.; Che, S.; Chen, Y.; ...

2015-12-21

Here, two-dimensional observations of spatially-coherent electron temperature fluctuations at drift wave scales (k ~1 cm -1) have been made using the electron cyclotron emission imaging (ECEI) diagnostic on the DIII-D tokamak. These measurements enable the extraction of spectral properties, including poloidal dispersion relations. Temperature fluctuation levels are found to be ˜ T e/< T e > = 1.2%, and the phase velocity of the fluctuations is found to be constant across frequencies, consistent with modes having real frequencies low compared to the rotation-induced Doppler shifts. Comparisons with radially global linear gyrokinetic simulations suggest that the observed modes may be trappedmore » electron modes (TEM).« less

Magnetic moment evolution and spin freezing in doped BaFe2As2

DOE PAGES

Pelliciari, Jonathan; Huang, Yaobo; Ishii, Kenji; ...

2017-08-14

Fe-K β X-ray emission spectroscopy measurements reveal an asymmetric doping dependence of the magnetic moments μ bare in electron- and hole-doped BaFe 2As 2. At low temperature, μ bare is nearly constant in hole-doped samples, whereas it decreases upon electron doping. Increasing temperature substantially enhances μ bare in the hole-doped region, which is naturally explained by the theoretically predicted crossover into a spin-frozen state. Our measurements demonstrate the importance of Hund’s-coupling and electronic correlations, especially for hole-doped BaFe 2As 2, as well as the inadequacy of a fully localized or fully itinerant description of the 122 family of Fe pnictides.

Fast-Ion Spectrometry of ICF Implosions and Laser-Foil Experiments at the Omega and MTW Laser Facilities

NASA Astrophysics Data System (ADS)

Sinenian, Nareg

Fast ions generated from laser-plasma interactions (LPI) have been used to study inertial confinement fusion (ICF) implosions and laser-foil interactions. LPI, which vary in nature depending on the wavelength and intensity of the driver, generate hot electrons with temperatures ranging from tens to thousands of kilo-electron-volts. These electrons, which accelerate the ions measured in this work, can be either detrimental or essential to implosion performance depending on the ICF scheme employed. In direct-drive hot-spot ignition, hot electrons can preheat the fuel and raise the adiabat, potentially degrading compression in the implosion. The amount of preheat depends on the hot-electron source characteristics and the time duration over which electrons can deposit energy into the fuel. This time duration is prescribed by the evolution of a sheath that surrounds the implosion and traps electrons. Fast-ion measurements have been used to develop a circuit model that describes the time decay of the sheath voltage for typical OMEGA implosions. In the context of electron fast ignition, the produced fast ions are considered a loss channel that has been characterized for the first time. These ions have also been used as a diagnostic tool to infer the temperature of the hot electrons in fast-ignition experiments. It has also been shown that the hot-electron temperature scales with laser intensity as expected, but is enhanced by a factor of 2-3. This enhancement is possibly due to relativistic effects and leads to poor implosion performance. Finally, fast-ion generation by ultra-intense lasers has also been studied using planar targets. The mean and maximum energies of protons and heavy ions has been measured, and it has been shown that a two-temperature hot-electron distribution affects the energies of heavy ions and protons. This work is important for advanced fusion concepts that utilize ion beams and also has applications in medicine. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)

Anomalous electronic heat capacity of copper nanowires at sub-Kelvin temperatures

NASA Astrophysics Data System (ADS)

Viisanen, K. L.; Pekola, J. P.

2018-03-01

We have measured the electronic heat capacity of thin film nanowires of copper and silver at temperatures 0.1-0.3 K; the films were deposited by standard electron-beam evaporation. The specific heat of the Ag films of sub-100-nm thickness agrees with the bulk value and the free-electron estimate, whereas that of similar Cu films exceeds the corresponding reference values by one order of magnitude. The origin of the anomalously high heat capacity of copper films remains unknown for the moment. Based on the small heat capacity at low temperatures and the possibility to devise a tunnel probe thermometer on it, metal films form a promising absorber material, e.g., for microwave photon calorimetry.

Electronically conductive ceramics for high temperature oxidizing environments

DOEpatents

Kucera, G.H.; Smith, J.L.; Sim, J.W.

1983-11-10

This invention pertains to a high temperature, ceramic composition having electronic conductivity as measured by resistivity below about 500 ohm-cm, chemical stability particularly with respect to cathode conditions in a molten carbonate fuel cell, and composed of an alkali metal, transition metal oxide containing a dopant metal in the crystalline structure to replace a portion of the alkali metal or transition metal.

Electronic effects on melting: Comparison of aluminum cluster anions and cations

NASA Astrophysics Data System (ADS)

Starace, Anne K.; Neal, Colleen M.; Cao, Baopeng; Jarrold, Martin F.; Aguado, Andrés; López, José M.

2009-07-01

Heat capacities have been measured as a function of temperature for aluminum cluster anions with 35-70 atoms. Melting temperatures and latent heats are determined from peaks in the heat capacities; cohesive energies are obtained for solid clusters from the latent heats and dissociation energies determined for liquid clusters. The melting temperatures, latent heats, and cohesive energies for the aluminum cluster anions are compared to previous measurements for the corresponding cations. Density functional theory calculations have been performed to identify the global minimum energy geometries for the cluster anions. The lowest energy geometries fall into four main families: distorted decahedral fragments, fcc fragments, fcc fragments with stacking faults, and "disordered" roughly spherical structures. The comparison of the cohesive energies for the lowest energy geometries with the measured values allows us to interpret the size variation in the latent heats. Both geometric and electronic shell closings contribute to the variations in the cohesive energies (and latent heats), but structural changes appear to be mainly responsible for the large variations in the melting temperatures with cluster size. The significant charge dependence of the latent heats found for some cluster sizes indicates that the electronic structure can change substantially when the cluster melts.

Spatially Resolved Nano-Scale Characterization of Electronic States in SrTiO3(001) Surfaces by STM/STS

NASA Astrophysics Data System (ADS)

Iwaya, Katsuya; Ohsawa, Takeo; Shimizu, Ryota; Hashizume, Tomihiro; Hitosugi, Taro

2012-02-01

We have performed low temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements on TiO2-terminated SrTiO3(001) thin film surfaces. The conductance map exhibited electronic modulations that were completely different from the surface structure. We also found that the electronic modulations were strongly dependent on temperature and the density of atomic defects associated with oxygen vacancies. These results suggest the existence of strongly correlated two-dimensional electronic states near the SrTiO3 surface, implying the importance of electron correlation at the interfaces of SrTiO3-related heterostructures.

Evidence of Collisionless Shocks in a Hall Thruster Plume

DTIC Science & Technology

2003-04-25

Triple Langmuir probes and emissive probes are used to measure the electron number density, electron temperature, and plasma potential downstream of a low-power Hall thruster . The results show a high density plasma core with elevated electron temperature and plasma potential along the thruster centerline. These properties are believed to be due to collisionless shocks formed as a result of the ion/ion acoustic instability. A simple model is presented that shows the existence of a collisionless shock to be consistent with the observed phenomena.

Angular sensitivity of modeled scientific silicon charge-coupled devices to initial electron direction

NASA Astrophysics Data System (ADS)

Plimley, Brian; Coffer, Amy; Zhang, Yigong; Vetter, Kai

2016-08-01

Previously, scientific silicon charge-coupled devices (CCDs) with 10.5-μm pixel pitch and a thick (650 μm), fully depleted bulk have been used to measure gamma-ray-induced fast electrons and demonstrate electron track Compton imaging. A model of the response of this CCD was also developed and benchmarked to experiment using Monte Carlo electron tracks. We now examine the trade-off in pixel pitch and electronic noise. We extend our CCD response model to different pixel pitch and readout noise per pixel, including pixel pitch of 2.5 μm, 5 μm, 10.5 μm, 20 μm, and 40 μm, and readout noise from 0 eV/pixel to 2 keV/pixel for 10.5 μm pixel pitch. The CCD images generated by this model using simulated electron tracks are processed by our trajectory reconstruction algorithm. The performance of the reconstruction algorithm defines the expected angular sensitivity as a function of electron energy, CCD pixel pitch, and readout noise per pixel. Results show that our existing pixel pitch of 10.5 μm is near optimal for our approach, because smaller pixels add little new information but are subject to greater statistical noise. In addition, we measured the readout noise per pixel for two different device temperatures in order to estimate the effect of temperature on the reconstruction algorithm performance, although the readout is not optimized for higher temperatures. The noise in our device at 240 K increases the FWHM of angular measurement error by no more than a factor of 2, from 26° to 49° FWHM for electrons between 425 keV and 480 keV. Therefore, a CCD could be used for electron-track-based imaging in a Peltier-cooled device.

High temperature irradiation induced creep in Ag nanopillars measured via in situ transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jawaharram, Gowtham Sriram; Price, Patrick M.; Barr, Christopher M.

Irradiation induced creep (IIC) rates are measured in compression on Ag nanopillar (square) beams in the sink-limited regime. The IIC rate increases linearly with stress at lower stresses, i.e. below ≈2/3 the high temperature yield stress and parabolically with pillar width, L, for L less than ≈300 nm. Here, the data are obtained by combining in situ transmission electron imaging with simultaneous ion irradiation, laser heating, and nanopillar compression. Results in the larger width regime are consistent with prior literature.

High temperature irradiation induced creep in Ag nanopillars measured via in situ transmission electron microscopy

DOE PAGES

Jawaharram, Gowtham Sriram; Price, Patrick M.; Barr, Christopher M.; ...

2018-01-30

Irradiation induced creep (IIC) rates are measured in compression on Ag nanopillar (square) beams in the sink-limited regime. The IIC rate increases linearly with stress at lower stresses, i.e. below ≈2/3 the high temperature yield stress and parabolically with pillar width, L, for L less than ≈300 nm. Here, the data are obtained by combining in situ transmission electron imaging with simultaneous ion irradiation, laser heating, and nanopillar compression. Results in the larger width regime are consistent with prior literature.

Integrated LTCC pressure/flow/temperature multisensor for compressed air diagnostics.

PubMed

Fournier, Yannick; Maeder, Thomas; Boutinard-Rouelle, Grégoire; Barras, Aurélie; Craquelin, Nicolas; Ryser, Peter

2010-01-01

We present a multisensor designed for industrial compressed air diagnostics and combining the measurement of pressure, flow, and temperature, integrated with the corresponding signal conditioning electronics in a single low-temperature co-fired ceramic (LTCC) package. The developed sensor may be soldered onto an integrated electro-fluidic platform by using standard surface mount device (SMD) technology, e.g., as a standard electronic component would be on a printed circuit board, obviating the need for both wires and tubes and thus paving the road towards low-cost integrated electro-fluidic systems. Several performance aspects of this device are presented and discussed, together with electronics design issues.

Integrated LTCC Pressure/Flow/Temperature Multisensor for Compressed Air Diagnostics†

PubMed Central

Fournier, Yannick; Maeder, Thomas; Boutinard-Rouelle, Grégoire; Barras, Aurélie; Craquelin, Nicolas; Ryser, Peter

2010-01-01

We present a multisensor designed for industrial compressed air diagnostics and combining the measurement of pressure, flow, and temperature, integrated with the corresponding signal conditioning electronics in a single low-temperature co-fired ceramic (LTCC) package. The developed sensor may be soldered onto an integrated electro-fluidic platform by using standard surface mount device (SMD) technology, e.g., as a standard electronic component would be on a printed circuit board, obviating the need for both wires and tubes and thus paving the road towards low-cost integrated electro-fluidic systems. Several performance aspects of this device are presented and discussed, together with electronics design issues. PMID:22163518

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope.

PubMed

Hieckmann, Ellen; Nacke, Markus; Allardt, Matthias; Bodrov, Yury; Chekhonin, Paul; Skrotzki, Werner; Weber, Jörg

2016-05-28

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

PubMed Central

Hieckmann, Ellen; Nacke, Markus; Allardt, Matthias; Bodrov, Yury; Chekhonin, Paul; Skrotzki, Werner; Weber, Jörg

2016-01-01

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared. PMID:27285177

A comparison of technologies used for estimation of body temperature.

PubMed

Mangat, Jasdip; Standley, Thomas; Prevost, Andrew; Vasconcelos, Joana; White, Paul

2010-09-01

Body temperature measurement is an important clinical parameter. The performance of a number of non-invasive thermometers was measured by comparing intra- and inter-operator variability (n = 100) and clinical accuracy (n = 61). Variability was elevated in febrile compared to normothermic subjects for axillary and oral electronic contact thermometer measures and a temporal artery thermometer (p < 0.001 for both). Temporal artery thermometry and one mode of an infrared tympanic thermometer demonstrated significant clinical inaccuracy (p < 0.001 for both). Electronic contact thermometer repeatability and reproducibility are highly variable in febrile adults both in the axilla and oral cavity. Infrared thermometry of the skin over the superficial temporal artery is unreliable for measuring core body temperature, particularly in febrile subjects and patients in theatre. The infrared tympanic thermometers tested are acceptable for clinical practice; however, care should be exercised with the different modes of operation offered.

Parametric scaling of neutral and ion excited state densities in an argon helicon source

NASA Astrophysics Data System (ADS)

McCarren, D.; Scime, E.

2016-04-01

We report measurements of the absolute density and temperature of ion and neutral excited states in an argon helicon source. The excited ion state density, which depends on ion density, electron density, and electron temperature, increases sharply with increasing magnetic field in the source. The neutral argon metastable density measurements are consistent with an increasing ionization fraction with increasing magnetic field strength. The ion temperature shows no evidence of increased heating with increasing magnetic field strength (which has only been observed in helicon sources operating at driving frequencies close to the lower hybrid frequency). The measurements were obtained through cavity ring down spectroscopy, a measurement technique that does not require the target excited state to be metastable or part of a fluorescence scheme; and is therefore applicable to any laser accessible atomic or ionic transition in a plasma.

Soft X-ray polychromator for the Solar Maximum Mission

NASA Astrophysics Data System (ADS)

Haisch, B. M.; Levay, M.; Stern, R. A.; Strong, K. T.; Wolfson, C. J.; Acton, L. W.

1984-12-01

The XRP was designed to measure the following temporal and spatial properties of the active and flaring Sun: electron temperature, departures from steady state, ion kinetic temperatures, and electron density. The Bent Crystal Spectrometer (BCS) is capable of measuring the broadening and blue shifts often observed in the impulsive phase of flares. The six simultaneous line fluxes indicative of six different temperatures of formation observable by the Flat Crystal Spectrometer (FCS) allows the derivation of the differential emission measure of the plasma at each raster point. During the operational periods of the XRP hundreds of flares of C-level (GOES classification) were observed and brighter in both the FCS and BCS, including 5 X-flares. Associated theoretical work in atomic physics, stimulated in part by the promise of XRP measurements, has benefitted from the experimental data on solar plasmas which the XRP has provided in abundance.

Soft X-ray polychromator for the Solar Maximum Mission

NASA Technical Reports Server (NTRS)

Haisch, B. M.; Levay, M.; Stern, R. A.; Strong, K. T.; Wolfson, C. J.; Acton, L. W.

1984-01-01

The XRP was designed to measure the following temporal and spatial properties of the active and flaring Sun: electron temperature, departures from steady state, ion kinetic temperatures, and electron density. The Bent Crystal Spectrometer (BCS) is capable of measuring the broadening and blue shifts often observed in the impulsive phase of flares. The six simultaneous line fluxes indicative of six different temperatures of formation observable by the Flat Crystal Spectrometer (FCS) allows the derivation of the differential emission measure of the plasma at each raster point. During the operational periods of the XRP hundreds of flares of C-level (GOES classification) were observed and brighter in both the FCS and BCS, including 5 X-flares. Associated theoretical work in atomic physics, stimulated in part by the promise of XRP measurements, has benefitted from the experimental data on solar plasmas which the XRP has provided in abundance.

A study of density measurements in hypersonic helium tunnels using an electron beam fluorescence technique

NASA Technical Reports Server (NTRS)

Honaker, W. C.; Hunter, W. W., Jr.; Woods, W. C.

1979-01-01

A series of experiments have been conducted at Langley Research Center to determine the feasibility of using electron-beam fluorescence to measure the free-stream static density of gaseous helium flow over a wide range of conditions. These experiments were conducted in the Langley hypersonic helium tunnel facility and its 3-inch prototype. Measurements were made for a range of stagnation pressures and temperatures and produced free-stream number densities of 1.53 x 10 to the 23rd to 1.25 x 10 to the 24th molecules/cu m and static temperatures from 2 K to 80 K. The results showed the collision quenching cross section to be 4.4 x 10 to the -15th sq cm at 1 K and to have a weak temperature dependence of T to the 1/6. With knowledge of these two values, the free-stream number density can be measured quite accurately.

Design and Implementation of High Precision Temperature Measurement Unit

NASA Astrophysics Data System (ADS)

Zeng, Xianzhen; Yu, Weiyu; Zhang, Zhijian; Liu, Hancheng

2018-03-01

Large-scale neutrino detector requires calibration of photomultiplier tubes (PMT) and electronic system in the detector, performed by plotting the calibration source with a group of designated coordinates in the acrylic sphere. Where the calibration source positioning is based on the principle of ultrasonic ranging, the transmission speed of ultrasonic in liquid scintillator of acrylic sphere is related to temperature. This paper presents a temperature measurement unit based on STM32L031 and single-line bus digital temperature sensor TSic506. The measurement data of the temperature measurement unit can help the ultrasonic ranging to be more accurate. The test results show that the temperature measurement error is within ±0.1°C, which satisfies the requirement of calibration source positioning. Take energy-saving measures, with 3.7V/50mAH lithium battery-powered, the temperature measurement unit can work continuously more than 24 hours.

Changes in divertor conditions in response to changing core density with RMPs

DOE PAGES

Briesemeister, Alexis R.; Ahn, Joon -Wook; Canik, John M.; ...

2017-06-07

The effects of changes in core density on divertor electron temperature, density and heat flux when resonant magnetic perturbations (RMPs) are applied are presented, notably a reduction in RMP induced secondary radial peaks in the electron temperature profile at the target plate is observed when the core density is increased, which is consistent with modeling. RMPs is used here to indicated non-axisymmetric magnetic field perturbations, created using in-vessel control coils, which have components which has at least one but typically many resonances with the rotational transform of the plasma. RMPs are found to alter inter-ELM heat flux to the divertormore » by modifying the core plasma density. It is shown that applying RMPs reduces the core density and increases the inter-ELM heat flux to both the inner and outer targets. Using gas puffing to return the core density to the pre-RMP levels more than eliminates the increase in inter-ELM heat flux, but a broadening of the heat flux to the outer target remains. These measurements were made at a single toroidal location, but the peak in the heat flux profile was found near the outer strike point where simulations indicate little toroidal variation should exist and tangentially viewing diagnostics showed no evidence of strong asymmetries. In experiments where divertor Thomson scattering measurements were available it is shown that, local secondary peaks in the divertor electron temperature profile near the target plate are reduced as the core density is increased, while peaks in the divertor electron density profile near the target are increased. Furthermore, these trends observed in the divertor electron temperature and density are qualitatively reproduced by scanning the upstream density in EMC3-Eirene modeling. Measurements are presented showing that higher densities are needed to induce detachment of the outer strike point in a case where an increase in electron temperature, likely due to a change in MHD activity, is seen after RMPs are applied.« less

Changes in divertor conditions in response to changing core density with RMPs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briesemeister, Alexis R.; Ahn, Joon -Wook; Canik, John M.

The effects of changes in core density on divertor electron temperature, density and heat flux when resonant magnetic perturbations (RMPs) are applied are presented, notably a reduction in RMP induced secondary radial peaks in the electron temperature profile at the target plate is observed when the core density is increased, which is consistent with modeling. RMPs is used here to indicated non-axisymmetric magnetic field perturbations, created using in-vessel control coils, which have components which has at least one but typically many resonances with the rotational transform of the plasma. RMPs are found to alter inter-ELM heat flux to the divertormore » by modifying the core plasma density. It is shown that applying RMPs reduces the core density and increases the inter-ELM heat flux to both the inner and outer targets. Using gas puffing to return the core density to the pre-RMP levels more than eliminates the increase in inter-ELM heat flux, but a broadening of the heat flux to the outer target remains. These measurements were made at a single toroidal location, but the peak in the heat flux profile was found near the outer strike point where simulations indicate little toroidal variation should exist and tangentially viewing diagnostics showed no evidence of strong asymmetries. In experiments where divertor Thomson scattering measurements were available it is shown that, local secondary peaks in the divertor electron temperature profile near the target plate are reduced as the core density is increased, while peaks in the divertor electron density profile near the target are increased. Furthermore, these trends observed in the divertor electron temperature and density are qualitatively reproduced by scanning the upstream density in EMC3-Eirene modeling. Measurements are presented showing that higher densities are needed to induce detachment of the outer strike point in a case where an increase in electron temperature, likely due to a change in MHD activity, is seen after RMPs are applied.« less

Electron temperature and heat load measurements in the COMPASS divertor using the new system of probes

NASA Astrophysics Data System (ADS)

Adamek, J.; Seidl, J.; Horacek, J.; Komm, M.; Eich, T.; Panek, R.; Cavalier, J.; Devitre, A.; Peterka, M.; Vondracek, P.; Stöckel, J.; Sestak, D.; Grover, O.; Bilkova, P.; Böhm, P.; Varju, J.; Havranek, A.; Weinzettl, V.; Lovell, J.; Dimitrova, M.; Mitosinkova, K.; Dejarnac, R.; Hron, M.; The COMPASS Team; The EUROfusion MST1 Team

2017-11-01

A new system of probes was recently installed in the divertor of tokamak COMPASS in order to investigate the ELM energy density with high spatial and temporal resolution. The new system consists of two arrays of rooftop-shaped Langmuir probes (LPs) used to measure the floating potential or the ion saturation current density and one array of Ball-pen probes (BPPs) used to measure the plasma potential with a spatial resolution of ~3.5 mm. The combination of floating BPPs and LPs yields the electron temperature with microsecond temporal resolution. We report on the design of the new divertor probe arrays and first results of electron temperature profile measurements in ELMy H-mode and L-mode. We also present comparative measurements of the parallel heat flux using the new probe arrays and fast infrared termography (IR) data during L-mode with excellent agreement between both techniques using a heat power transmission coefficient γ  =  7. The ELM energy density {{\\varepsilon }\\parallel } was measured during a set of NBI assisted ELMy H-mode discharges. The peak values of {{\\varepsilon }\\parallel } were compared with those predicted by model and with experimental data from JET, AUG and MAST with a good agreement.

Observations of electron heating during 28 GHz microwave power application in proto-MPEX

DOE PAGES

Biewer, Theodore M.; Bigelow, Tim S.; Caneses Marin, Juan F.; ...

2018-02-01

The Prototype Material Plasma Exposure Experiment at the Oak Ridge National Laboratory utilizes a variety of power systems to generate and deliver a high heat flux plasma onto the surface of material targets. In the experiments described here, a deuterium plasma is produced via a ~100 kW, 13.56 MHz RF helicon source, to which ~20 kW of 28 GHz microwave power is applied. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is centrally peaked. In the core of the plasma column, the electron density is higher than themore » cut-off density (~0.9 × 1019 m -3) for the launched mixture of X- and O-mode electron cyclotron heating waves to propagate. TS measurements indicate electron temperature increases from ~5 eV to ~20 eV during 28 GHz power application when the neutral deuterium pressure is reduced below 0.13 Pa (~1 mTorr.).« less

Observations of electron heating during 28 GHz microwave power application in proto-MPEX

NASA Astrophysics Data System (ADS)

Biewer, T. M.; Bigelow, T. S.; Caneses, J. F.; Diem, S. J.; Green, D. L.; Kafle, N.; Rapp, J.; Proto-MPEX Team

2018-02-01

The Prototype Material Plasma Exposure Experiment at the Oak Ridge National Laboratory utilizes a variety of power systems to generate and deliver a high heat flux plasma onto the surface of material targets. In the experiments described here, a deuterium plasma is produced via a ˜100 kW, 13.56 MHz RF helicon source, to which ˜20 kW of 28 GHz microwave power is applied. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is centrally peaked. In the core of the plasma column, the electron density is higher than the cut-off density (˜0.9 × 1019 m-3) for the launched mixture of X- and O-mode electron cyclotron heating waves to propagate. TS measurements indicate electron temperature increases from ˜5 eV to ˜20 eV during 28 GHz power application when the neutral deuterium pressure is reduced below 0.13 Pa (˜1 mTorr.).

Estimations of electron densities and temperatures in He-3 dominated plasmas. [in nuclear pumped lasers

NASA Technical Reports Server (NTRS)

Depaola, B. D.; Marcum, S. D.; Wrench, H. K.; Whitten, B. L.; Wells, W. E.

1979-01-01

It is very useful to have a method of estimation for electron temperature and electron densities in nuclear pumped plasmas because measurements of such quantities are very difficult. This paper describes a method, based on rate equation analysis of the ionized species in the plasma and the electron energy balance. In addition to the ionized species, certain neutral species must also be calculated. Examples are given for pure helium and a mixture of helium and argon. In the HeAr case, He(+), He2(+), He/2 3S/, Ar(+), Ar2(+), and excited Ar are evaluated.

Bloch-Grüneisen nonlinearity of electron transport in GaAs/AlGaAs heterostructures

DOE PAGES

Raichev, O. E.; Hatke, A. T.; Zudov, M. A.; ...

2017-08-22

We report on nonlinear transport measurements in a two-dimensional electron gas hosted in GaAs/AlGaAs heterostructures. Upon application of direct current, the low-temperature differential resistivity acquires a positive correction, which exhibits a pronounced maximum followed by a plateau. With increasing temperature, the nonlinearity diminishes and disappears. These observations can be understood in terms of a crossover from the Bloch-Gr¨uneisen regime to the quasielastic scattering regime as the electrons are heated by direct current. Calculations considering interaction of electrons with acoustic phonons provide reasonable description of our experimental findings.

The effect of reaction temperature on the room temperature ferromagnetic property of sol-gel derived tin oxide nanocrystal

NASA Astrophysics Data System (ADS)

Sakthiraj, K.; Hema, M.; Balachandra Kumar, K.

2018-06-01

In the present study, nanocrystalline tin oxide materials were prepared using sol-gel method with different reaction temperatures (25 °C, 50 °C, 75 °C & 90 °C) and the relation between the room temperature ferromagnetic property of the sample with processing temperature has been analysed. The X-ray diffraction pattern and infrared absorption spectra of the as-prepared samples confirm the purity of the samples. Transmission electron microscopy images visualize the particle size variation with respect to reaction temperature. The photoluminescence spectra of the samples demonstrate that luminescence process in materials is originated due to the electron transition mediated by defect centres. The room temperature ferromagnetic property is observed in all the samples with different amount, which was confirmed using vibrating sample magnetometer measurements. The saturation magnetization value of the as-prepared samples is increased with increasing the reaction temperature. From the photoluminescence & magnetic measurements we accomplished that, more amount of surface defects like oxygen vacancy and tin interstitial are created due to the increase in reaction temperature and it controls the ferromagnetic property of the samples.

Optical Diagnostics on HIT-SI3

NASA Astrophysics Data System (ADS)

Everson, Christopher; Jarboe, Thomas; Morgan, Kyle

2016-10-01

Interferometry and Thomson Scattering are implemented on the HIT-SI3 (Helicity Injected Torus - Steady Inductive 3) device to provide time resolved measurements of electron density and spatially resolved measurements of electron temperature, respectively. HIT-SI3 is a modification of the original HIT-SI apparatus that uses three injectors instead of two. The scientific aim of HIT-SI3 is to develop a deeper understanding of how injector behavior and interactions influence current drive and spheromak stability. The interferometer system makes use of an intermediate frequency between two parallel 184.3 μm Far-Infrared (FIR) laser cavities which are optically pumped by a CO2 laser. The phase shift in this beat frequency due to the plasma index of refraction is used to calculate the line-integrated electron density. To measure the electron temperature, Thomson Scattered light from a 20 J (1 GW pulse) Ruby laser off of free electrons in the HIT-SI3 plasma is measured simultaneously at four locations across the spheromak (nominally 23 cm minor radius). Polychromators bin the collected light into 3 spectral bands to detect the relative level of scattering. Work supported by the D.O.E.

Electron Profile Stiffness and Critical Gradient Length Studies in the Alcator C-Mod Tokamak

NASA Astrophysics Data System (ADS)

Houshmandyar, Saeid; Hatch, David R.; Liao, Kenneth T.; Zhao, Bingzhe; Phillips, Perry E.; Rowan, William L.; Cao, Norman; Ernst, Darin R.; Rice, John E.

2017-10-01

Electron temperature profile stiffness was investigated at Alcator C-Mod L-mode discharges. Electrons were heated by ion cyclotron range of frequencies (ICRF) through minority heating. The intent of the heating mechanism was to vary the heat flux and simultaneously, gradually change the local gradient. The electron temperature gradient scale length (LTe- 1 = | ∇Te |/Te) was accurately measured through a novel technique, using the high-resolution radiometer ECE diagnostic. The TRANSP power balance analysis (Q/QGB) and the measured scale length (a/LTe) result in critical scale length measurements at all major radius locations. These measurements suggest that the profiles are already at the critical values. Furthermore, the dependence of the stiffness on plasma rotation and magnetic shear will be discussed. In order to understand the underlying mechanism of turbulence for these discharges, simulations using the gyrokinetic code, GENE, were carried out. For linear runs at electron scales, it was found that the largest growth rates are very sensitive to a/LTe variation, which suggests the presence of ETG modes, while the sensitivity studies in the ion scales indicate ITG/TEM modes. Supported by USDoE awards DE-FG03-96ER54373 and DE-FC02-99ER54512.

Ultra-fast electron capture by electrosterically-stabilized gold nanoparticles.

PubMed

Ghandi, Khashayar; Findlater, Alexander D; Mahimwalla, Zahid; MacNeil, Connor S; Awoonor-Williams, Ernest; Zahariev, Federico; Gordon, Mark S

2015-07-21

Ultra-fast pre-solvated electron capture has been observed for aqueous solutions of room-temperature ionic liquid (RTIL) surface-stabilized gold nanoparticles (AuNPs; ∼9 nm). The extraordinarily large inverse temperature dependent rate constants (k(e)∼ 5 × 10(14) M(-1) s(-1)) measured for the capture of electrons in solution suggest electron capture by the AuNP surface that is on the timescale of, and therefore in competition with, electron solvation and electron-cation recombination reactions. The observed electron transfer rates challenge the conventional notion that radiation induced biological damage would be enhanced in the presence of AuNPs. On the contrary, AuNPs stabilized by non-covalently bonded ligands demonstrate the potential to quench radiation-induced electrons, indicating potential applications in fields ranging from radiation therapy to heterogeneous catalysis.

Investigation of the temperature dependent field emission from individual ZnO nanowires for evidence of field-induced hot electrons emission.

PubMed

Chen, Yicong; Zhang, Zhipeng; Li, Zhi-Bing; She, Juncong; Deng, Shaozhi; Xu, Ning-Sheng; Chen, Jun

2018-06-27

ZnO nanowires as field emitters have important applications in flat panel display and X-ray source. Understanding the intrinsic field emission mechanism is crucial for further improving the performance of ZnO nanowire field emitters. In this article, the temperature dependent field emission from individual ZnO nanowires was investigated by an in-situ measurement in ultra-high vacuum. The divergent temperature-dependent Fowler-Nordheim plots is found in the low field region. A field-induced hot electrons emission model that takes into account penetration length is proposed to explain the results. The carrier density and temperature dependence of the field-induced hot electrons emission current are derived theoretically. The obtained results are consistent with the experimental results, which could be attributed to the variation of effective electron temperature. All of these are important for a better understanding on the field emission process of semiconductor nanostructures. © 2018 IOP Publishing Ltd.

A compact new incoherent Thomson scattering diagnostic for low-temperature plasma studies

NASA Astrophysics Data System (ADS)

Vincent, Benjamin; Tsikata, Sedina; Mazouffre, Stéphane; Minea, Tiberiu; Fils, Jérôme

2018-05-01

Incoherent Thomson scattering (ITS) has a long history of application for the determination of electron density and temperature in dense fusion plasmas, and in recent years, has been increasingly extended to studies in low-temperature plasma environments. In this work, the design and preliminary implementation of a new, sensitive and uniquely compact ITS platform known as Thomson scattering experiments for low temperature ion sources are described. Measurements have been performed on a hollow cathode plasma source, providing access to electron densities as low as 1016 m‑3 and electron temperatures of a few eV and below. This achievement has been made possible by the implementation of a narrow volume Bragg grating notch filter for the attenuation of stray light, a feature which guarantees compactness and reduced transmission losses in comparison to standard ITS platforms.

A Two-Fluid, MHD Coronal Model

NASA Technical Reports Server (NTRS)

Suess, S. T.; Wang, A.-H.; Wu, S. T.; Poletto, G.; McComas, D. J.

1999-01-01

We describe first results from a numerical two-fluid MHD model of the global structure of the solar Corona. The model is two-fluid in the sense that it accounts for the collisional energy exchange between protons and electrons. As in our single-fluid model, volumetric heat and Momentum sources are required to produce high speed wind from Corona] holes, low speed wind above streamers, and mass fluxes similar to the empirical solar wind. By specifying different proton and electron heating functions we obtain a high proton temperature in the coronal hole and a relatively low proton temperature above the streamer (in comparison with the electron temperature). This is consistent with inferences from SOHO/UltraViolet Coronagraph Spectrometer instrument (UVCS), and with the Ulysses/Solar Wind Observations Over the Poles of the Sun instrument (SWOOPS) proton and electron temperature measurements which we show from the fast latitude scan. The density in the coronal hole between 2 and 5 solar radii (2 and 5 R(sub S)) is similar to the density reported from SPARTAN 201.-01 measurements by Fisher and Guhathakurta [19941. The proton mass flux scaled to 1 AU is 2.4 x 10(exp 8)/sq cm s, which is consistent with Ulysses observations. Inside the closed field region, the density is sufficiently high so that the simulation gives equal proton and electron temperatures due to the high collision rate. In open field regions (in the coronal hole and above the streamer) the proton and electron temperatures differ by varying amounts. In the streamer the temperature and density are similar to those reported empirically by Li et al. [1998], and the plasma beta is larger than unity everywhere above approx. 1.5 R(sub S), as it is in all other MHD coronal streamer models [e.g., Steinolfson et al., 1982; also G. A. Gary and D. Alexander, Constructing the coronal magnetic field, submitted to Solar Physics, 1998].

Laboratory plasma with cold electron temperature of the lower ionosphere

NASA Astrophysics Data System (ADS)

Dickson, Shannon; Robertson, Scott

2009-10-01

For the first time, plasma with cold electron temperatures less than 300K has been created continuously in the laboratory. The plasma is created in a cylindrical double-walled vacuum chamber in which the inner chamber (18cm in diameter and 30cm long) is wrapped in copper tubing through which vapor from liquid nitrogen flows, providing a cooling mechanism for the neutral gas. The inner chamber has two negatively-biased filaments for plasma generation and a platinum wire Langmuir probe for diagnostic measurements. Neutral gas pressures of 1.6mTorr and a total filament emission current of 2mA are used to obtain plasma densities near 4 x 10^8 cm-3. When carbon monoxide is used as the working gas, decreasing the neutral gas temperature also decreases the cold electron temperatures, yielding cold electrons with 21meV (240K) when the neutral CO is at 150K. The same experiment conducted with H2, He, or Ar results in a doubling of the cold electron temperatures, yielding 80meV (930K) when the neutral gas is at 150K. The lower electron temperature with CO is attributed to the asymmetric CO molecule having a nonzero electric dipole moment which increases the cross section for electron energy exchange. Nitric oxide, a dominant constituent of the ionosphere, has a similar dipole moment and collision cross section as carbon monoxide and is likely to be equally effective at cooling electrons.

Temperature dependence of Brillouin light scattering spectra of acoustic phonons in silicon

NASA Astrophysics Data System (ADS)

Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin

2015-02-01

Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. The need for a better understanding of such non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report the measured BLS spectra of silicon at different temperatures. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in order to evaluate their potential use as temperature sensors for acoustic phonons.

Adiabatic electron thermal pressure fluctuations in tokamak plasmas.

PubMed

Meier, M A; Bengtson, R D; Hallock, G A; Wootton, A J

2001-08-20

Electron thermal pressure fluctuations measured in the edge plasma of the Texas Experimental Tokamak Upgrade are a fundamental component of plasma turbulence on both sides of the velocity shear layer. The ratio of specific heats, estimated from fluctuations in electron temperature and electron number density measured simultaneously at the same electrode, indicates that observed fluctuations are adiabatic. The observations are made by means of a novel Langmuir probe technique, the time domain triple-probe method, which concurrently measures multiple plasma properties at each of two electrodes with the temporal and the spatial resolution required to estimate thermodynamic properties in a turbulent plasma.

Electron impact study of potassium hydroxide

NASA Technical Reports Server (NTRS)

Vuskovic, L.; Trajmar, S.

1979-01-01

An attempt is made to measure the sum of the elastic, rotational and vibrational scattering of electrons by KOH at low impact energies (5 to 20 eV) at angles from 10 to 120 deg. Energy loss spectra taken in the 0 to 18 eV range using an electron impact spectrometer are used to identify the species contributing to electric scattering. At temperatures between 300 and 500 C, only inelastic spectral features belonging to water are detected, while at temperatures from 500 to 800 C strong atomic K lines, indicative of molecular dissociation, and H2 energy loss features become prominent. No features attributable to KOH, the KOH dimer, O2 or potassium oxides were observed, due to the effects of the dissociation products, and it is concluded that another technique will have to be developed in order to measure electron scattering by KOH.

Simultaneous imaging electron- and ion-feature Thomson scattering measurements of radiatively heated Xe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pollock, B. B.; University of California, San Diego, 9500 Gilman Dr., La Jolla, California 92093; Meinecke, J.

2012-10-15

Uniform density and temperature Xe plasmas have been produced over >4 mm scale-lengths using x-rays generated in a cylindrical Pb cavity. The cavity is 750 {mu}m in depth and diameter, and is heated by a 300 J, 2 ns square, 1054 nm laser pulse focused to a spot size of 200 {mu}m at the cavity entrance. The plasma is characterized by simultaneous imaging Thomson scattering measurements from both the electron and ion scattering features. The electron feature measurement determines the spatial electron density and temperature profile, and using these parameters as constraints in the ion feature analysis allows an accuratemore » determination of the charge state of the Xe ions. The Thomson scattering probe beam is 40 J, 200 ps, and 527 nm, and is focused to a 100 {mu}m spot size at the entrance of the Pb cavity. Each system has a spatial resolution of 25 {mu}m, a temporal resolution of 200 ps (as determined by the probe duration), and a spectral resolution of 2 nm for the electron feature system and 0.025 nm for the ion feature system. The experiment is performed in a Xe filled target chamber at a neutral pressure of 3-10 Torr, and the x-rays produced in the Pb ionize and heat the Xe to a charge state of 20{+-}4 at up to 200 eV electron temperatures.« less

Measurement of Electron Density Using the Multipole Resonance Probe, Langmuir Probe and Optical Emission Spectroscopy in Low Pressure Plasmas with Different Electron Energy Distribution Functions

NASA Astrophysics Data System (ADS)

Oberberg, Moritz; Bibinov, Nikita; Ries, Stefan; Awakowicz, Peter; Institute of Electrical Engineering; Plasma Technology Team

2016-09-01

In recently publication, the young diagnostic tool Multipole Resonance Probe (MRP) for electron density measurements was introduced. It is based on active plasma resonance spectroscopy (APRS). The probe was simulated und evaluated for different devices. The geometrical and electrical symmetry simplifies the APRS model, so that the electron density can be easily calculated from the measured resonance. In this work, low pressure nitrogen mixture plasmas with different electron energy distribution functions (EEDF) are investigated. The results of the MRP measurement are compared with measurements of a Langmuir Probe (LP) and Optical Emission Spectroscopy (OES). Probes and OES measure in different regimes of kinetic electron energy. Both probes measure electrons with low kinetic energy (<10 eV), whereas the OES is influenced by electrons with high kinetic energy which are needed for transitions of molecule bands. By the determination of the absolute intensity of N2(C-B) and N2+(B-X)electron temperature and density can be calculated. In a non-maxwellian plasma, all plasma diagnostics need to be combined.

Estimations of Kappa parameter using quasi-thermal noise spectroscopy: Applications on Wind spacecraft

NASA Astrophysics Data System (ADS)

Martinović, M.

2017-12-01

Quasi-thermal noise (QTN) spectroscopy is an accurate technique for in situ measurements of electron density and temperature in space plasmas. The QTN spectrum has a characteristic noise peak just above the plasma frequency produced by electron quasi-thermal fluctuations, which allows a very accurate measurement of the electron density. The size and shape of the peak are determined by suprathermal electrons. Since this nonthermal electron population is well described by a generalized Lorentzian - Kappa velocity distribution, it is possible to determinate the distribution properties in the solar wind from a measured spectrum. In this work, we discuss some basic properties of the QTN spectrum dependence of the Kappa distribution parameters - total electron density, temperature and the Kappa index, giving an overview on how instrument characteristics and environment conditions affect quality of the measurements. Further on, we aim to apply the method to Wind Thermal Noise Receiver (TNR) measurements. However, the spectra observed by this instrument usually contain contributions from nonthermal phenomena, like ion acoustic waves below, or galactic noise above the plasma frequency. This is why, besides comparison of the theory with observations, work with Wind data requires development of a sophisticated algorithm that distinguish parts of the spectra that are dominated by the QTN, and therefore can be used in our study. Postulates of this algorithm, as well as major results of its implementation, are also presented.

Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research

NASA Astrophysics Data System (ADS)

Oh, Jaechul; Weaver, J. L.; Karasik, M.; Chan, L. Y.

2015-08-01

A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (˜1 ns FWHM) with the intensity of 1.1 × 1015 W/cm2. The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 1021 cm-3 with the density scale length of 120 μm along the plasma symmetry axis. The resulting ne and Te profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

The influence of the Ar/O2 ratio on the electron density and electron temperature in microwave discharges

NASA Astrophysics Data System (ADS)

Espinho, S.; Hofmann, S.; Palomares, J. M.; Nijdam, S.

2017-10-01

The aim of this work is to study the properties of Ar-O2 microwave driven surfatron plasmas as a function of the Ar/O2 ratio in the gas mixture. The key parameters are the plasma electron density and electron temperature, which are estimated with Thomson scattering (TS) for O2 contents up to 50% of the total gas flow. A sharp drop in the electron density from {10}20 {{{m}}}-3 to approximately {10}18 {{{m}}}-3 is estimated as the O2 content in the gas mixture is increased up to 15%. For percentages of O2 lower than 10%, the electron temperature is estimated to be about 2-3 times higher than in the case of a pure argon discharge in the same conditions ({T}{{e}}≈ 1 eV) and gradually decreases as the O2 percentage is raised to 50%. However, for O2 percentages above 30%, the scattering spectra become Raman dominated, resulting in large uncertainties in the estimated electron densities and temperatures. The influence of photo-detached electrons from negative ions caused by the typical TS laser fluences is also likely to contribute to the uncertainty in the measured electron densities for high O2 percentages. Moreover, the detection limit of the system is reached for percentages of O2 higher than 25%. Additionally, both the electron density and temperature of microwave discharges with large Ar/O2 ratios are more sensitive to gas pressure variations.

Quasi-optical design for systems to diagnose the electron temperature and density fluctuations on EAST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Qifo; Liu, Yong; Zhao, Hailin, E-mail: zhaohailin@ipp.ac.cn

A system to simultaneously diagnose the electron temperature and density fluctuations is proposed for Experimental Advanced Superconducting Tokamak device. This system includes a common quasi-optical antenna, a correlation electron cyclotron emission (CECE) system that is used to measure the electron temperature fluctuations and a Doppler backscattering (DBS) system that is used to measure the electron density fluctuations. The frequency range of the proposed CECE system is 108-120 GHz, and this corresponds to a radial coverage of normalized radius ((R − R{sub 0})/a, R{sub 0} = 1850 mm, a = 450 mm) from 0.2 to 0.67 for the plasma operation withmore » a toroidal magnetic field of 2.26 T. This paper focuses on the design of the quasi-optical antenna and aims at optimizing the poloidal resolution for different frequency bands. An optimum result gives the beam radius for the CECE system of 13-15 mm and this corresponds to a wave number range of k{sub θ} < 2.4 cm{sup −1}. The beam radius is 20-30 mm for V band (50-75 GHz) and 15-20 mm for W band (75-110 GHz).« less

High-resolution electron microscope observation of voids in amorphous Ge.

NASA Technical Reports Server (NTRS)

Donovan, T. M.; Heinemann, K.

1971-01-01

Electron micrographs have been obtained which clearly show the existence of a void network in amorphous Ge films formed at substrate temperatures of 25 and 150 C, and the absence of a void network in films formed at higher substrate temperatures of 200 and 250 C. These results correlate quite well with density measurements and predictions of void densities by indirect methods.

Effect of temperature on the electronic instability and the crystalline phase change at low temperature of V3Si type compounds

NASA Technical Reports Server (NTRS)

Labbe, J.; Friedel, J.

1977-01-01

Equations assuming a Jahn-Teller type effect for the d band electrons in V3Si compounds are given, and the results of free-energy change calculations by using some approximations based on these equations are depicted. The tetragonal structure is converted to cubic as the temperature rises past T sub m which is calculated as 13 K. by the Batterman-Barrett method and is measured to be 20-5 K. Other parameters such as change of C sub p with temperature are predicted better.

Temperature-induced band shift in bulk γ-InSe by angle-resolved photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Xu, Huanfeng; Wang, Wei; Zhao, Yafei; Zhang, Xiaoqian; Feng, Yue; Tu, Jian; Gu, Chenyi; Sun, Yizhe; Liu, Chang; Nie, Yuefeng; Edmond Turcu, Ion C.; Xu, Yongbing; He, Liang

2018-05-01

Indium selenide (InSe) has recently become popular research topics because of its unique layered crystal structure, direct band gap and high electron mobilities. In this work, we have acquired the electronic structure of bulk γ-InSe at various temperatures using angle-resolved photoemission spectroscopy (ARPES). We have also found that as the temperature decreases, the valence bands of γ-InSe exhibit a monotonic shift to lower binding energies. This band shift is attributed to the change of lattice parameters and has been validated by variable temperature X-ray diffraction measurements and theoretical calculations.

Electron-Beam Deposition of Superconducting Molybdenum Thin Films for the Development of Mo/Au TES X-Ray Microcalorimeter

NASA Technical Reports Server (NTRS)

Finkbeiner, Fred Michael; Adams, Joseph S.; Bandler, Simon R.; Betancour-Martinez, Gabriele L.; Brown, Ari David; Chang, Meng-Ping; Chervenak, James A.; Chiao, Meng P.; Datesman, Aaron; Eckart, Megan E.;

Temperature, illumination, and fluence dependence of current and voltage in electron irradiated solar cells

NASA Technical Reports Server (NTRS)

Faith, T. J.; Obenschain, A. F.

1974-01-01

Empirical equations have been derived from measurements of solar cell photovoltaic characteristics relating light-generated current and open circuit voltage to cell temperature, intensity of illumination and 1-MeV electron fluence. Both 2-ohm-cm and 10-ohm-cm cells were tested over the temperature range from 120 to 470 K, the illumination intensity range from 5 to 1830 mW/sq cm, and the electron fluence range from 1 x 10 to the 13th to 1 x 10 to the 16th electrons/sq cm. The normalized temperature coefficient of the light generated current varies as the 0.18 power of the fluence for temperatures above approximately 273 K and is independent of fluence at lower temperatures. At 140 mW/sq cm, a power law expression was derived which shows that the light-generated current decreases at a rate proportional to the 0.153 power of the fluence for both resistivities. The coefficient of the expression is larger for 2-ohm-cm cells; consequently, the advantage for 10-ohm-cm cells increased with increasing fluence.

Validations of calibration-free measurements of electron temperature using double-pass Thomson scattering diagnostics from theoretical and experimental aspects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tojo, H., E-mail: tojo.hiroshi@qst.go.jp; Hiratsuka, J.; Yatsuka, E.

2016-09-15

This paper evaluates the accuracy of electron temperature measurements and relative transmissivities of double-pass Thomson scattering diagnostics. The electron temperature (T{sub e}) is obtained from the ratio of signals from a double-pass scattering system, then relative transmissivities are calculated from the measured T{sub e} and intensity of the signals. How accurate the values are depends on the electron temperature (T{sub e}) and scattering angle (θ), and therefore the accuracy of the values was evaluated experimentally using the Large Helical Device (LHD) and the Tokyo spherical tokamak-2 (TST-2). Analyzing the data from the TST-2 indicates that a high T{sub e} andmore » a large scattering angle (θ) yield accurate values. Indeed, the errors for scattering angle θ = 135° are approximately half of those for θ = 115°. The method of determining the T{sub e} in a wide T{sub e} range spanning over two orders of magnitude (0.01–1.5 keV) was validated using the experimental results of the LHD and TST-2. A simple method to provide relative transmissivities, which include inputs from collection optics, vacuum window, optical fibers, and polychromators, is also presented. The relative errors were less than approximately 10%. Numerical simulations also indicate that the T{sub e} measurements are valid under harsh radiation conditions. This method to obtain T{sub e} can be considered for the design of Thomson scattering systems where there is high-performance plasma that generates harsh radiation environments.« less

Highly Conducting Molecular Crystals.

NASA Astrophysics Data System (ADS)

Whitehead, Roger James

Available from UMI in association with The British Library. Requires signed TDF. As the result of a wide ranging effort towards the preparation of new electrically conducting molecular crystals, high quality samples were prepared of the organic radical-ion salt (TMTSF)_2SbCl _2F_4 {bis-tetramethyltetraselenafulvalene-dichlorotetrafluoroantimonate(V) }. A collaborative effort to investigate the electronic and structural properties of this material has yielded the necessary depth of information required to give a satisfactory understanding of its rather complicated behaviour. The combination of x-ray structural studies with d.c. transport, reflectance and magnetic measurements has served to underline the importance of crystalline perfection, electronic dimensionality and conduction electron correlation in determining the materials overall behaviour. This thesis describes the method of preparation and characterization of (TMTSF)_2SbCl _2F_4 and the experimental arrangements used to determine the temperature dependence of its ambient pressure electrical conductivity, thermopower and electron spin resonance spectra. The crystal structure and optical reflectance measurements at room temperature are also presented. The results into a study of the low temperature diffraction pattern are described along with the temperature dependence in the static magnetic susceptibility and in the conductivity behaviour under elevated hydrostatic pressures. These findings are rationalized by reference to other materials which show similar behaviour in their electronic and/or structural properties, and also to the various theoretical models currently enjoying favour.

Size-dependent magnetic anisotropy of PEG coated Fe3O4 nanoparticles; comparing two magnetization methods

NASA Astrophysics Data System (ADS)

Nayek, C.; Manna, K.; Imam, A. A.; Alqasrawi, A. Y.; Obaidat, I. M.

2018-02-01

Understanding the size dependent magnetic anisotropy of iron oxide nanoparticles is essential for the successful application of these nanoparticles in several technological and medical fields. PEG-coated iron oxide (Fe3O4) nanoparticles with core diameters of 12 nm, 15 nm, and 16 nm were synthesized by the usual co-precipitation method. The morphology and structure of the nanoparticles were investigated using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray diffraction (XRD). Magnetic measurements were conducted using a SQUID. The effective magnetic anisotropy was calculated using two methods from the magnetization measurements. In the first method the zero-field-cooled magnetization versus temperature measurements were used at several applied magnetic fields. In the second method we used the temperature-dependent coercivity curves obtained from the zero-field-cooled magnetization versus magnetic field hysteresis loops. The role of the applied magnetic field on the effective magnetic anisotropy, calculated form the zero-field-cooled magnetization versus temperature measurements, was revealed. The size dependence of the effective magnetic anisotropy constant Keff obtained by the two methods are compared and discussed.

Characterization of a dielectric barrier discharge in contact with liquid and producing a plasma activated water

NASA Astrophysics Data System (ADS)

Neretti, G.; Taglioli, M.; Colonna, G.; Borghi, C. A.

2017-01-01

In this work a low-temperature plasma source for the generation of plasma activated water (PAW) is developed and characterized. The plasma reactor was operated by means of an atmospheric-pressure air dielectric barrier discharge (DBD). The plasma generated is in contact with the water surface and is able to chemically activate the liquid medium. Electrodes were supplied by both sinusoidal and nanosecond-pulsed voltage waveforms. Treatment times were varied from 2 to 12 min to increase the energy dose released to the water by the DBD plasma. The physics of the discharge was studied by means of electrical, spectroscopic and imaging diagnostics. The interaction between the plasma and the liquid was investigated as well. Temperature and composition of the treated water were detected. Images of the discharges showed a filamentary behaviour in the sinusoidal case and a more homogeneous behaviour in the nanosecond-pulsed one. The images and the electrical measurements allowed to evaluate an average electron number density of about 4  ×  1019 and 6  ×  1017 m-3 for the sinusoidal and nanosecond-pulsed discharges respectively. Electron temperatures in the range of 2.1÷2.6 eV were measured by using spectroscopic diagnostics. Rotational temperatures in the range of 318-475 K were estimated by fitting synthetic spectra with the measured ones. Water temperature and pH level did not change significantly after the exposure to the DBD plasma. The production of ozone and hydrogen peroxide within the water was enhanced by increasing the plasma treatment time and the energy dose. Numerical simulations of the nanosecond-pulsed discharge were performed by using a self-consistent coupling of state-to-state kinetics of the air mixture with the Boltzmann equation of free electron kinetics. Temporal evolution of the electron energy distribution function shows departure from the Maxwellian distribution especially during the afterglow phase of the discharge. When limited deviations from Maxwellian distribution were observed, calculated electron temperature is in good agreement with the one measured by means of spectroscopic diagnostics. Computed temporal evolution of the energy delivered to the discharge is comparable with the one obtained from electrical measurements. The electrical discharges supplied by both voltage waveforms produce plasma activated water with negligible thermal effects and pH variations.

Numerical Solution of the Electron Heat Transport Equation and Physics-Constrained Modeling of the Thermal Conductivity via Sequential Quadratic Programming Optimization in Nuclear Fusion Plasmas

NASA Astrophysics Data System (ADS)

Paloma, Cynthia S.

The plasma electron temperature (Te) plays a critical role in a tokamak nu- clear fusion reactor since temperatures on the order of 108K are required to achieve fusion conditions. Many plasma properties in a tokamak nuclear fusion reactor are modeled by partial differential equations (PDE's) because they depend not only on time but also on space. In particular, the dynamics of the electron temperature is governed by a PDE referred to as the Electron Heat Transport Equation (EHTE). In this work, a numerical method is developed to solve the EHTE based on a custom finite-difference technique. The solution of the EHTE is compared to temperature profiles obtained by using TRANSP, a sophisticated plasma transport code, for specific discharges from the DIII-D tokamak, located at the DIII-D National Fusion Facility in San Diego, CA. The thermal conductivity (also called thermal diffusivity) of the electrons (Xe) is a plasma parameter that plays a critical role in the EHTE since it indicates how the electron temperature diffusion varies across the minor effective radius of the tokamak. TRANSP approximates Xe through a curve-fitting technique to match experimentally measured electron temperature profiles. While complex physics-based model have been proposed for Xe, there is a lack of a simple mathematical model for the thermal diffusivity that could be used for control design. In this work, a model for Xe is proposed based on a scaling law involving key plasma variables such as the electron temperature (Te), the electron density (ne), and the safety factor (q). An optimization algorithm is developed based on the Sequential Quadratic Programming (SQP) technique to optimize the scaling factors appearing in the proposed model so that the predicted electron temperature and magnetic flux profiles match predefined target profiles in the best possible way. A simulation study summarizing the outcomes of the optimization procedure is presented to illustrate the potential of the proposed modeling method.

Correlation-driven insulator-metal transition in near-ideal vanadium dioxide films

DOE PAGES

Gray, A. X.; Jeong, J.; Aetukuri, N. P.; ...

2016-03-18

We use polarization- and temperature-dependent x-ray absorption spectroscopy, in combination with photoelectron microscopy, x-ray diffraction, and electronic transport measurements, to study the driving force behind the insulator-metal transition in VO 2. We show that both the collapse of the insulating gap and the concomitant change in crystal symmetry in homogeneously strained single-crystalline VO 2 films are preceded by the purely electronic softening of Coulomb correlations within V-V singlet dimers. Furthermore, this process starts 7 K (±0.3 K) below the transition temperature, as conventionally defined by electronic transport and x-ray diffraction measurements, and sets the energy scale for driving the near-room-temperaturemore » insulator-metal transition in this technologically promising material.« less

First quantitative measurements of charged-particle stopping and its dependence on electron temperature and density in Inertial-Confinement-Fusion plasmas

NASA Astrophysics Data System (ADS)

Frenje, J.; Li, C. K.; Séguin, F.; Zylstra, A.; Rinderknecht, H.; Petrasso, R.; Delettrez, J.; Glebov, V.; Sangster, T.

2013-10-01

We report on the first quantitative measurements of charged-particle stopping in Inertial-Confinement-Fusion (ICF) plasmas at various conditions. In these experiments, four charged fusion products from the DD and D3He reactions in D3He gas-filled filled implosions were used to determine the stopping power of ICF plasmas at electron temperatures (Te) , ion temperatures (Ti) , and areal densities (ρR) in the range of 0.6-4.0 keV, 3-14 keV and 2-10 mg/cm2, respectively. The resulting data, in the form of measured energy downshift of the charged fusion products, clearly indicate that the stopping-power function depends strongly on Te. It was also observed that the stopping-power function change in characteristics for higher-density implosions in which ions and electrons equilibrate faster, resulting in higher Te relative to Ti and higher ρR s. These results will be modelled by Landau-Spitzer theory and contrasted to different stopping-power models. This work was partially supported by the US DOE, NLUF, LLE, and GA.

Investigation of Room temperature Ferromagnetism in Mn doped Ge

NASA Astrophysics Data System (ADS)

Colakerol Arslan, Leyla; Toydemir, Burcu; Onel, Aykut Can; Ertas, Merve; Doganay, Hatice; Gebze Inst of Tech Collaboration; Research Center Julich Collaboration

2014-03-01

We present a systematic investigation of structural, magnetic and electronic properties of MnxGe1 -x single crystals. MnxGe1-x films were grown by sequential deposition of Ge and Mn by molecular-beam epitaxy at low substrate temperatures in order to avoid precipitation of ferromagnetic Ge-Mn intermetallic compounds. Reflected high energy electron diffraction and x-ray diffraction observations revealed that films are epitaxially grown on Si (001) substrates from the initial stage without any other phase formation. Magnetic measurements carried out using a physical property measurement system showed that all samples exhibited ferromagnetism at room temperature. Electron spin resonance indicates the presence of magnetically ordered localized spins of divalent Mn ions. X-ray absorption measurements at the Mn L-edge confirm significant substitutional doping of Mn into Ge-sites. The ferromagnetism was mainly induced by Mn substitution for Ge site, and indirect exchange interaction of these magnetic ions with the intrinsic charge carriers is the origin of ferromagnetism. The magnetic interactions were better understood by codoping with nonmagnetic impurities. This work was supported by Marie-Curie Reintegration Grant (PIRG08-GA-2010-276973).

Breathable and Stretchable Temperature Sensors Inspired by Skin.

PubMed

Chen, Ying; Lu, Bingwei; Chen, Yihao; Feng, Xue

2015-06-22

Flexible electronics attached to skin for healthcare, such as epidermal electronics, has to struggle with biocompatibility and adapt to specified environment of skin with respect to breath and perspiration. Here, we report a strategy for biocompatible flexible temperature sensors, inspired by skin, possessing the excellent permeability of air and high quality of water-proof by using semipermeable film with porous structures as substrate. We attach such temperature sensors to underarm and forearm to measure the axillary temperature and body surface temperature respectively. The volunteer wears such sensors for 24 hours with two times of shower and the in vitro test shows no sign of maceration or stimulation to the skin. Especially, precise temperature changes on skin surface caused by flowing air and water dropping are also measured to validate the accuracy and dynamical response. The results show that the biocompatible temperature sensor is soft and breathable on the human skin and has the excellent accuracy compared to mercury thermometer. This demonstrates the possibility and feasibility of fully using the sensors in long term body temperature sensing for medical use as well as sensing function of artificial skin for robots or prosthesis.

Brillouin light scattering as a probe for low frequency quasiparticles in solids

NASA Astrophysics Data System (ADS)

Klimovich, Nikita; Olson, Kevin; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin

2015-03-01

In increasingly small electronic and spintronic devices, electrons, optical phonons, acoustic phonons, and magnons are often driven out of local thermal equilibrium. Thermal transport based on equilibrium dynamics does not adequately describe these systems necessitating a better understanding of non-equilibrium transport processes. Measuring the specific temperatures of the different energy carriers is therefore crucial in understanding the thermal transport. Brillouin light scattering (BLS) has recently been explored as a temperature sensor for low frequency acoustic phonons in glass, and also magnons in metallic and insulating ferromagnetic materials. We report the measured BLS spectra of acoustic phonons in Silicon at different temperatures. The temperature dependence of the BLS peak frequency, linewidth, and integrated intensity are examined to evaluate their potential uses as temperature sensors of acoustic phonons. We also observe a large nonequilibrium in phonon-magnon temperature in YIG under the effects of laser heating and thereby extract a value for the phonon-magnon coupling coefficient. This work is funded by the National Science Foundation and the Army Research Office.

Thermomechanical and Thermochemical Behavior of a Hafnium-20 Percent Tantalum Alloy. Ph.D. Thesis - North Carolina State Univ., Raleigh

NASA Technical Reports Server (NTRS)

Howell, J. P.

1971-01-01

An investigation was conducted to determine the thermomechanical and thermochemical behavior of a high temperature, oxidation resistant, hafnium-20 percent tantalum alloy. The elastic and shear moduli of this alloy were determined in air up to 1000 C and in vacuum up to 2000 C using a mechanical resonance technique. The internal friction of the alloy was measured up to temperatures greater than 1400 C. Room temperature stress-strain behavior of the oxidized and unoxidized alloy was established. The effect of annealing on the elastic and shear moduli of the extruded rod material was investigated. The martensitic-type phase transformation occurring in the alloy was studied using hot stage metallography and electron microscopy. Static oxidation tests were conducted on the alloy at temperatures from 1000 C to 1700 C with weight gain measurements made as a function of time and temperatures. Surface morphology studies were conducted on the oxide coatings formed at the different temperatures using scanning electron microscopy and X-ray diffraction techniques.

Measurement of density and temperature in a hypersonic turbulent boundary layer using the electron beam fluorescence technique. Ph.D. Thesis. Final Report, 1 Oct. 1969 - 1 Sep. 1972

NASA Technical Reports Server (NTRS)

Mcronald, A. D.

1975-01-01

Mean density and temperature fluctuations were measured across the turbulent, cooled-wall boundary layer in a continuous hypersonic (Mach 9.4) wind tunnel in air, using the nitrogen fluorescence excited by a 50 kV electron beam. Data were taken at three values of the tunnel stagnation pressure, the corresponding free stream densities being equivalent to 1.2, 4.0, and 7.4 torr at room temperature, and the boundary layer thicknesses about 4.0, 4.5, and 6.0 inches. The mean temperature and density profiles were similar to those previously determined in the same facility by conventional probes (static and pitot pressure, total temperature). A static pressure variation of about 50% across the boundary layer was found, the shape of the variation changing somewhat for the three stagnation pressure levels. The quadrupole model for rotational temperature spectra gave closer agreement with the free stream isentropic level (approximately 44 K) than the dipole model.

Cross-field electron transport inside an insulating cylinder of a baffled probe

NASA Astrophysics Data System (ADS)

Raitses, Yevgeny; Alt, Andrew

2017-10-01

Plasma-immersed wall experiments have been performed in a magnetized xenon plasma in a cross-field Penning configuration with density around 1012 cm-3 and an electron temperature around a few eV. A cylinder with an open end and diameter of 1.4 mm was placed across field lines so that electrons were blocked from reaching a wire recessed behind the shield while ions were unimpeded. The reduction of electron current to the wire causes it to float closer to the plasma potential, possibly making a device that can passively measure plasma potential. However, the measured electron current was much higher than expected even when the wire was recessed several electron gyroradii behind the baffle. Possible mechanisms for this electron conduction causing the short circuiting to the bulk plasma have been studied with numerical approaches and with a dedicated experiment designed to isolate this short circuit effect. The obtained results may be important for cross-field transport in a variety of other configurations in magnetized, low-temperature plasmas. This work was supported by DOE contract DE-AC02-09CH11466.

Observation of microwave absorption and emission from incoherent electron tunneling through a normal-metal-insulator-superconductor junction.

PubMed

Masuda, Shumpei; Tan, Kuan Y; Partanen, Matti; Lake, Russell E; Govenius, Joonas; Silveri, Matti; Grabert, Hermann; Möttönen, Mikko

2018-03-02

We experimentally study nanoscale normal-metal-insulator-superconductor junctions coupled to a superconducting microwave resonator. We observe that bias-voltage-controllable single-electron tunneling through the junctions gives rise to a direct conversion between the electrostatic energy and that of microwave photons. The measured power spectral density of the microwave radiation emitted by the resonator exceeds at high bias voltages that of an equivalent single-mode radiation source at 2.5 K although the phonon and electron reservoirs are at subkelvin temperatures. Measurements of the generated power quantitatively agree with a theoretical model in a wide range of bias voltages. Thus, we have developed a microwave source which is compatible with low-temperature electronics and offers convenient in-situ electrical control of the incoherent photon emission rate with a predetermined frequency, without relying on intrinsic voltage fluctuations of heated normal-metal components or suffering from unwanted losses in room temperature cables. Importantly, our observation of negative generated power at relatively low bias voltages provides a novel type of verification of the working principles of the recently discovered quantum-circuit refrigerator.

Production of O2 on icy satellites by electronic excitation of low-temperature water ice.

PubMed

Sieger, M T; Simpson, W C; Orlando, T M

1998-08-06

The signature of condensed molecular oxygen has been reported in recent optical-reflectance measurements of the jovian moon Ganymede, and a tenuous oxygen atmosphere has been observed on Europa. The surfaces of these moons contain large amounts of water ice, and it is thought that O2 is formed by the sputtering of ice by energetic particles from the jovian magnetosphere. Understanding how O2 might be formed from low-temperature ice is crucial for theoretical and experimental simulations of the surfaces and atmospheres of icy bodies in the Solar System. Here we report laboratory measurements of the threshold energy, cross-section and temperature dependence of O2 production by electronic excitation of ice in vacuum, following electron-beam irradiation. Molecular oxygen is formed by direct excitation and dissociation of a stable precursor molecule, rather than (as has been previously thought) by diffusion and chemical recombination of precursor fragments. The large cross-section for O2 production suggests that electronic excitation plays an important part in the formation of O2 on Ganymede and Europa.

4 Kelvin Cryogenic Characterization of Commercial pHEMT Transistors at 9 kHz to 8.5 GHz Range

NASA Astrophysics Data System (ADS)

Ibarra-Medel, E.; Velázquez, M.; Ventura, S.; Ferrusca, D.; Gómez-Rivera, V.

2016-07-01

Nowadays, the technology innovations in large format array detectors at low temperature for millimetric observational astronomy demand the development of electronics capable to keep their functionality at cryogenic temperatures. In kinetic inductance detectors, the first stage of electronics readout requires high-bandwidth low-noise amplifiers (LNAs). These devices are commonly fabricated in monolithic microwave integrated circuit (MMIC) processes which commercially achieve a noise temperature level of 5 K. An alternative approach to the MMIC are the hybrid microwave circuit which mixes RF lumped elements and discrete electronic components. This paper describes the characterization of six commercial pHEMT transistors tested at cryogenic temperatures. DC properties such as I-V curves and transconductance (g_m) were measured for each transistor; these measurements allow us to calculate the best bias point versus gain, with the lowest noise figure and power consumption within the range of 9 kHz to 8.5 GHz at the operating temperature of 4 K. Experimental results suggest that the characterized pHEMTs have a noise figure that allow them to be used in hybrid LNAs arranges with a comparable MMIC performance.

High-frequency electron-spin-resonance measurements on Mn x Mg1-x O (x = 1.0×10-4) and DPPH at very low temperatures

NASA Astrophysics Data System (ADS)

Ishikawa, Y.; Ohya, K.; Miura, S.; Fujii, Y.; Mitsudo, S.; Mizusaki, T.; Fukuda, A.; Matsubara, A.; Kikuchi, H.; Asano, T.; Yamamori, H.; Lee, S.; Vasiliev, S.

2018-03-01

We have developed a millimeter-wave electron-spin-resonance (ESR) system for very low temperatures (T < 1 K) that can be employed for nuclear-magnetic-resonance measurements by using dynamic nuclear polarization. The system uses a Fabry-Pérot resonator that works in the frequency range of 125 – 130 GHz and covers the temperature range of 0.09 – 6.5 K. We have performed ESR measurements in the frequency around 128 GHz by using Mn x Mg1-x O (x = 1.0 × 10-4) and free-radical samples of 1, 1-diphenyl-2-picrylhydrazyl (DPPH), because these samples have been proposed as field and sensitivity markers. Temperature dependence of the ESR signal intensity for Mn x Mg1-x O shows anomalies originating from magnetic order are found around 3.5 – 4 K. We estimate the sensitivity of the system for ESR detections to be 6 × 1013 spins/G at 5.8 K. Because DPPH shows no observable shift in the magnetic field, we propose it as a useful standard marker for ESR measurements at very low temperatures.

Investigation of a possible electronic phase separation in the magnetic semiconductors Ga1 -xMnxAs and Ga1 -xMnxP by means of fluctuation spectroscopy

NASA Astrophysics Data System (ADS)

Lonsky, Martin; Teschabai-Oglu, Jan; Pierz, Klaus; Sievers, Sibylle; Schumacher, Hans Werner; Yuan, Ye; Böttger, Roman; Zhou, Shengqiang; Müller, Jens

2018-02-01

We present systematic temperature-dependent resistance noise measurements on a series of ferromagnetic Ga1 -xMnxAs epitaxial thin films covering a large parameter space in terms of the Mn content x and other variations regarding sample fabrication. We infer that the electronic noise is dominated by switching processes related to impurities in the entire temperature range. While metallic compounds with x >2 % do not exhibit any significant change in the low-frequency resistance noise around the Curie temperature TC, we find indications for an electronic phase separation in films with x <2 % in the vicinity of TC, manifesting itself in a maximum in the noise power spectral density. These results are compared with noise measurements on an insulating Ga1 -xMnxP reference sample, for which the evidence for an electronic phase separation is even stronger and a possible percolation of bound magnetic polarons is discussed. Another aspect addressed in this work is the effect of ion-irradiation-induced disorder on the electronic properties of Ga1 -xMnxAs films and, in particular, whether any electronic inhomogeneities can be observed in this case. Finally, we put our findings into the context of the ongoing debate on the electronic structure and the development of spontaneous magnetization in these materials.

Observations of temperature rise during electron cyclotron heating application in Proto-MPEX

NASA Astrophysics Data System (ADS)

Biewer, T. M.; Bigelow, T.; Caneses, J. F.; Diem, S. J.; Rapp, J.; Reinke, M.; Kafle, N.; Ray, H. B.; Showers, M.

2017-10-01

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at ORNL utilizes a variety of power systems to generate and deliver a high heat flux plasma (1 MW/m2 for these discharges) onto the surface of material targets. In the experiments described here, up to 120 kW of 13.56 MHz ``helicon'' waves are combined with 20 kW of 28 GHz microwaves to produce Deuterium plasma discharges. The 28 GHz waves are launched in a region of the device where the magnetic field is axially varying near 0.8 T, resulting in the presence of a 2nd harmonic electron cyclotron heating (ECH) resonance layer that transects the plasma column. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is radially peaked. In the core of the plasma column the electron density is higher than the cut-off density (0.9x1019 m-3) for ECH waves to propagate and O-X-B mode conversion into electron Bernstien waves (EBW) is expected. TS measurements indicate electron temperature increases during 28 GHz wave application, rising (from 5 eV to 20 eV) as the neutral Deuterium pressure is reduced below 1 mTorr. This work was supported by the US. D.O.E. contract DE-AC05-00OR22725.

Heating power at the substrate, electron temperature, and electron density in 2.45 GHz low-pressure microwave plasma

NASA Astrophysics Data System (ADS)

Kais, A.; Lo, J.; Thérèse, L.; Guillot, Ph.

2018-01-01

To control the temperature during a plasma treatment, an understanding of the link between the plasma parameters and the fundamental process responsible for the heating is required. In this work, the power supplied by the plasma onto the surface of a glass substrate is measured using the calorimetric method. It has been shown that the powers deposited by ions and electrons, and their recombination at the surface are the main contributions to the heating power. Each contribution is estimated according to the theory commonly used in the literature. Using the corona balance, the Modified Boltzmann Plot (MBP) is employed to determine the electron temperature. A correlation between the power deposited by the plasma and the results of the MBP has been established. This correlation has been used to estimate the electron number density independent of the Langmuir probe in considered conditions.

First-Principles Estimation of Electronic Temperature from X-Ray Thomson Scattering Spectrum of Isochorically Heated Warm Dense Matter

NASA Astrophysics Data System (ADS)

Mo, Chongjie; Fu, Zhenguo; Kang, Wei; Zhang, Ping; He, X. T.

2018-05-01

Through the perturbation formula of time-dependent density functional theory broadly employed in the calculation of solids, we provide a first-principles calculation of x-ray Thomson scattering spectrum of isochorically heated aluminum foil, as considered in the experiments of Sperling et al. [Phys. Rev. Lett. 115, 115001 (2015), 10.1103/PhysRevLett.115.115001], where ions were constrained near their lattice positions. From the calculated spectra, we find that the electronic temperature cannot exceed 2 eV, much smaller than the previous estimation of 6 eV via the detailed balance relation. Our results may well be an indication of unique electronic properties of warm dense matter, which can be further illustrated by future experiments. The lower electronic temperature predicted partially relieves the concern on the heating of x-ray free electron laser to the sample when used in structure measurement.

Electron density measurements in STPX plasmas

NASA Astrophysics Data System (ADS)

Clark, Jerry; Williams, R.; Titus, J. B.; Mezonlin, E. D.; Akpovo, C.; Thomas, E.

2017-10-01

Diagnostics have been installed to measure the electron density of Spheromak Turbulent Physics Experiment (STPX) plasmas at Florida A. & M. University. An insertable probe, provided by Auburn University, consisting of a combination of a triple-tipped Langmuir probe and a radial array consisting of three ion saturation current / floating potential rings has been installed to measure instantaneous plasma density, temperature and plasma potential. As the ramp-up of the experimental program commences, initial electron density measurements from the triple-probe show that the electron density is on the order of 1019 particles/m3. For a passive measurement, a CO2 interferometer system has been designed and installed for measuring line-averaged densities and to corroborate the Langmuir measurements. We describe the design, calibration, and performance of these diagnostic systems on large volume STPX plasmas.

Electron attachment to CF3 and CF3Br at temperatures up to 890 K: experimental test of the kinetic modeling approach.

PubMed

Shuman, Nicholas S; Miller, Thomas M; Viggiano, Albert A; Troe, Jürgen

2013-05-28

Thermal rate constants and product branching fractions for electron attachment to CF3Br and the CF3 radical have been measured over the temperature range 300-890 K, the upper limit being restricted by thermal decomposition of CF3Br. Both measurements were made in Flowing Afterglow Langmuir Probe apparatuses; the CF3Br measurement was made using standard techniques, and the CF3 measurement using the Variable Electron and Neutral Density Attachment Mass Spectrometry technique. Attachment to CF3Br proceeds exclusively by the dissociative channel yielding Br(-), with a rate constant increasing from 1.1 × 10(-8) cm(3) s(-1) at 300 K to 5.3 × 10(-8) cm(3) s(-1) at 890 K, somewhat lower than previous data at temperatures up to 777 K. CF3 attachment proceeds through competition between associative attachment yielding CF3 (-) and dissociative attachment yielding F(-). Prior data up to 600 K showed the rate constant monotonically increasing, with the partial rate constant of the dissociative channel following Arrhenius behavior; however, extrapolation of the data using a recently proposed kinetic modeling approach predicted the rate constant to turn over at higher temperatures, despite being only ~5% of the collision rate. The current data agree well with the previous kinetic modeling extrapolation, providing a demonstration of the predictive capabilities of the approach.

Understanding Bright 13 keV Kr K-shell X-ray Sources at the NIF

NASA Astrophysics Data System (ADS)

May, M. J.; Colvin, J. D.; Kemp, G. E.; Fournier, K. B.; Scott, H.; Patel, M.; Barrios, Widmann; Widmann, K.

2015-11-01

High x-ray conversion efficiency (CE) K-shell Kr sources are being investigated for High Energy Density experiments. These sources are 4.1 mm in diameter 4.4 mm tall hollow epoxy tubes having a 40 μm thick wall holding either 1.2 or 1.5 atm of Kr gas. The CE of K-shell Kr is dependent upon the peak electron temperature in the radiating plasma. In the NIF experiments, the available energy heats the source to Te = 6-7 keV, well below the temperature of Te ~25 keV needed to optimize the Kr CE. The CE is a steep function of the peak electron temperature. A spatially averaged electron temperature can be estimated from measured He(α) and Ly(α) line ratios. Some disagreement has been observed in the simulated and measured line ratios for some of these K-shell sources. Disagreements have been observed between the simulated and measured line ratios for some of these K-shell sources. To help understand this issue, Kr gas pipes have been shot with 3 ω light at ?750 kJ at ~210, ~140 TW and ~120 TW power levels with 3.7, 5.2 and 6.7 ns pulses, respectively. The power and pulse length scaling of the measured CE and K-shell line ratios and their comparison to simulations will be discussed. This work was performed under the auspic

Interaction of hydrogen chloride with alumina. [atmospheric effluent concentrations and interaction of solid rocket propellants used in space shuttle

NASA Technical Reports Server (NTRS)

Bailey, R. R.; Wightman, J. P.

1978-01-01

The influence of temperature, pressure, and outgas conditions on the absorption of hydrogen chloride and water vapor on both alpha and gamma alumina was studied. Characterization of the adsorbents was performed using X-ray powder diffraction, scanning electron microscopy (SEM), low temperature nitrogen adsorption desorption measurements, BET nitrogen surface area measurements and electron spectroscopy for chemical analysis (ESCA). Water vapor adsorption isotherms at 30, 40, and 50 C were measured on alpha and gamma alumina after outgassing at 80, 200, and 400 C. Both outgas temperature and adsorption temperature influenced the adsorption of water vapor on the aluminas. The water vapor adsorption was completely reversible. Alpha alumina absorbed more water per unit area than gamma alumina. Differences in the adsorption capacity for water vapor of the two aluminas were explained on the basis of ideal surface models of alpha and gamma alumina. Isosteric heats of adsorption for water vapor on the aluminas were determined over a limited range of surface coverage.

Barrier inhomogeneities and electronic transport of Pt contacts to relatively highly doped n-type 4H-SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Lingqin, E-mail: lqhuang@jsnu.edu.cn, E-mail: dwang121@dlut.edu.cn; Wang, Dejun, E-mail: lqhuang@jsnu.edu.cn, E-mail: dwang121@dlut.edu.cn

The barrier characteristics of Pt contacts to relatively highly doped (∼1 × 10{sup 18 }cm{sup −3}) 4H-SiC were investigated using current-voltage (I-V) and capacitance-voltage (C-V) measurements in the temperature range of 160–573 K. The barrier height and ideally factor estimated from the I-V characteristics based on the thermionic emission model are abnormally temperature-dependent, which can be explained by assuming the presence of a double Gaussian distribution (GD) of inhomogeneous barrier heights. However, in the low temperature region (160–323 K), the obtained mean barrier height according to GD is lower than the actual mean value from C-V measurement. The values of barrier height determined from themore » thermionic field emission model are well consistent with those from the C-V measurements, which suggest that the current transport process could be modified by electron tunneling at low temperatures.« less

On the design of the NIF Continuum Spectrometer

NASA Astrophysics Data System (ADS)

Thorn, D. B.; MacPhee, A.; Ayers, J.; Galbraith, J.; Hardy, C. M.; Izumi, N.; Bradley, D. K.; Pickworth, L. A.; Bachmann, B.; Kozioziemski, B.; Landen, O.; Clark, D.; Schneider, M. B.; Hill, K. W.; Bitter, M.; Nagel, S.; Bell, P. M.; Person, S.; Khater, H. Y.; Smith, C.; Kilkenny, J.

2017-08-01

In inertial confinement fusion (ICF) experiments on the National Ignition Facility (NIF), measurements of average ion temperature using DT neutron time of flight broadening and of DD neutrons do not show the same apparent temperature. Some of this may be due to time and space dependent temperature profiles in the imploding capsule which are not taken into account in the analysis. As such, we are attempting to measure the electron temperature by recording the free-free electron-ion scattering-spectrum from the tail of the Maxwellian temperature distribution. This will be accomplished with the new NIF Continuum Spectrometer (ConSpec) which spans the x-ray range of 20 keV to 30 keV (where any opacity corrections from the remaining mass of the ablator shell are negligible) and will be sensitive to temperatures between ˜ 3 keV and 6 keV. The optical design of the ConSpec is designed to be adaptable to an x-ray streak camera to record time resolved free-free electron continuum spectra for direct measurement of the dT/dt evolution across the burn width of a DT plasma. The spectrometer is a conically bent Bragg crystal in a focusing geometry that allows for the dispersion plane to be perpendicular to the spectrometer axis. Additionally, to address the spatial temperature dependence, both time integrated and time resolved pinhole and penumbral imaging will be provided along the same polar angle. The optical and mechanical design of the instrument is presented along with estimates for the dispersion, solid angle, photometric sensitivity, and performance.

Warming of infusion syringes caused by electronic syringe pumps.

PubMed

Cornelius, A; Frey, B; Neff, T A; Gerber, A C; Weiss, M

2003-05-01

To evaluate inadvertent warming of the infusion syringe in four different types of electronic syringe pumps. Ambient temperature and syringe surface temperature were simultaneously measured by two electronic temperature probes in four different models of commercially available syringe pumps. Experiments were performed at an infusion rate of 1 ml h(-1) using both battery-operated and main power-operated pumps. Measurements were repeated four times with two pumps from each of the four syringe pump types at a room temperature of approximately 23 degrees C. Differences among the four syringe pump brands regarding ambient to syringe temperature gradient were compared using ANOVA. A P-value of less than 0.05 was considered statistically significant. Syringe warming differed significantly between the four syringe brands for both the battery-operated and main power-operated mode (ANOVA, P< 0.001 for both modes). Individual differences between syringe surface and ambient temperature ranged from 0.3 to 1.9 degrees C for battery operation and from 0.5 to 11.2 degrees C during main-power operation. Infusion solutions can be significantly warmed by syringe pumps. This has potential impact on bacterial growth and the stability of drug solutions and blood products infused, as well as on the susceptibility to hydrostatic pressure changes within the infusion syringe.

Method to determine thermal profiles of nanoscale circuitry

DOEpatents

Zettl, Alexander K; Begtrup, Gavi E

2013-04-30

A platform that can measure the thermal profiles of devices with nanoscale resolution has been developed. The system measures the local temperature by using an array of nanoscale thermometers. This process can be observed in real time using a high resolution imagining technique such as electron microscopy. The platform can operate at extremely high temperatures.

Isolating lattice from electronic contributions in thermal transport measurements of metals and alloys above ambient temperature and an adiabatic model

NASA Astrophysics Data System (ADS)

Criss, Everett M.; Hofmeister, Anne M.

2017-06-01

From femtosecond spectroscopy (fs-spectroscopy) of metals, electrons and phonons reequilibrate nearly independently, which contrasts with models of heat transfer at ordinary temperatures (T > 100 K). These electronic transfer models only agree with thermal conductivity (k) data at a single temperature, but do not agree with thermal diffusivity (D) data. To address the discrepancies, which are important to problems in solid state physics, we separately measured electronic (ele) and phononic (lat) components of D in many metals and alloys over ˜290-1100 K by varying measurement duration and sample length in laser-flash experiments. These mechanisms produce distinct diffusive responses in temperature versus time acquisitions because carrier speeds (u) and heat capacities (C) differ greatly. Electronic transport of heat only operates for a brief time after heat is applied because u is high. High Dele is associated with moderate T, long lengths, low electrical resistivity, and loss of ferromagnetism. Relationships of Dele and Dlat with physical properties support our assignments. Although kele reaches ˜20 × klat near 470 K, it is transient. Combining previous data on u with each D provides mean free paths and lifetimes that are consistent with ˜298 K fs-spectroscopy, and new values at high T. Our findings are consistent with nearly-free electrons absorbing and transmitting a small fraction of the incoming heat, whereas phonons absorb and transmit the majority. We model time-dependent, parallel heat transfer under adiabatic conditions which is one-dimensional in solids, as required by thermodynamic law. For noninteracting mechanisms, k≅ΣCikiΣCi/(ΣCi2). For metals, this reduces to k = klat above ˜20 K, consistent with our measurements, and shows that Meissner’s equation (k≅klat + kele) is invalid above ˜20 K. For one mechanism with multiple, interacting carriers, k≅ΣCiki/(ΣCi). Thus, certain dynamic behaviors of electrons and phonons in metals have been misunderstood. Implications for theoretical models and technological advancements are briefly discussed.

Wireless monitoring of highways

NASA Astrophysics Data System (ADS)

Bennett, Richard; Hayes-Gill, Barrie; Crowe, John A.; Armitage, Robert; Rodgers, Dale; Hendroff, Adrian

1999-05-01

Electronic hardware has been developed to telemetrically transmit temperature and strain measurements from within a public highway in the UK. These measurements provide an important health check for monitoring fatigue damage in pavements. Previous attempts at measuring strain and temperature have required lengths of cable to be installed in the highway. The installation of these cables is both expensive and damaging to the pavement and provides potentially unreliable electrical connections. The new systems consist of a retrofitted instrumented asphalt core which is bonded into the pavement structure. The core contains all the electronics necessary to record two temperatures and two strains. An analogue front end provides signal conditioning which is digitized and passed to microcontroller for endcoding. From there the data is transmitted via a low power radio link to a receiver and data logger positioned by the side of the road. The system has an in-situ operating life of 6 months on AA alkaline batteries. Results are presented of power management and fault tolerant radio protocol techniques, long term temperature variations, dynamic strain measurements within the highway, and RF transmission capabilities through a layer of asphalt.

Electric property measurement of free-standing SrTiO3 nanoparticles assembled by dielectrophoresis

NASA Astrophysics Data System (ADS)

Budiman, Faisal; Kotooka, Takumi; Horibe, Yoichi; Eguchi, Masanori; Tanaka, Hirofumi

2018-06-01

Free-standing strontium titanate (SrTiO3/STO) nanoparticles (NPs) were synthesized by the sol–gel method. X-ray diffractometry revealed that the required minimum annealing temperature to synthesize pure and highly crystalline STO NPs was 500 °C. Moreover, morphological observation by field emission scanning electron microscopy showed that the STO NPs have a spherical structure and their size depended on annealing condition. Electrical properties were measured using a low-temperature probing system. Here, an electrode was fabricated by electron beam lithography and the synthesized STO NPs were aligned at the electrodes by dielectrophoresis. The conductance of a sample was proportional to temperature. Two conduction mechanisms originating from hopping and tunneling appeared in the Arrhenius plot.

Closed loop control of penetration depth during CO₂ laser lap welding processes.

PubMed

Sibillano, Teresa; Rizzi, Domenico; Mezzapesa, Francesco P; Lugarà, Pietro Mario; Konuk, Ali Riza; Aarts, Ronald; Veld, Bert Huis In 't; Ancona, Antonio

2012-01-01

In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth.

Closed Loop Control of Penetration Depth during CO2 Laser Lap Welding Processes

PubMed Central

Sibillano, Teresa; Rizzi, Domenico; Mezzapesa, Francesco P.; Lugarà, Pietro Mario; Konuk, Ali Riza; Aarts, Ronald; Veld, Bert Huis in 't; Ancona, Antonio

2012-01-01

In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth. PMID:23112646

Electron Spin Coherence Times in Si/SiGe Quantum Dots

NASA Astrophysics Data System (ADS)

Jock, R. M.; He, Jianhua; Tyryshkin, A. M.; Lyon, S. A.; Lee, C.-H.; Huang, S.-H.; Liu, C. W.

2014-03-01

Single electron spin states in silicon have shown a great deal of promise as qubits due to their long spin relaxation (T1) and coherence (T2) times. Recent results exhibit a T2 of 250 us for electrons confined in Si/SiGe quantum dots at 350 mK. These experiments used conventional X-band (10 GHz) pulsed Electron Spin Resonance on a large area (3.5 mm x 20 mm), dual-gated, undoped Si/SiGe heterostructure quantum dots. These dots are induced in a natural Si quantum well by e-beam defined gates having a lithographic radius of 150 nm and pitch of 700 nm. The relatively large size of these dots led to closely spaced energy levels and long T2's could only be measured at sub-Kelvin temperatures. At 2K confined electrons displayed a 3 us T2, which is comparable to that of 2D electrons at that temperature. Decreasing the quantum dot size increases the electron confinement and reduces the effects of valley-splitting and spin-orbit coupling on the electron spin coherence times. We will report results on dots with 80 nm lithographic radii and a 375 nm pitch. This device displays an extended electron coherence time of 30 us at 2K, suggesting tighter confinement of electrons. Further measurements at lower temperatures are in progress. This work was supported in part by NSF through the Materials World Network program (DMR-1107606) and the Princeton MRSEC (DMR-0819860), and in part by the U.S. Army Research Office (W911NF-13-1-0179).

Measurement of strains at high temperatures by means of a portable holographic moire camera

NASA Astrophysics Data System (ADS)

Sciammarella, C. A.; Bhat, G.; Shao, Y.

Electronic holographic moire is utilized to measure strains at temperatures up to 1000 C. A CW laser operating at 50 mW and at the wavelength of 632.8 nm is used to illuminate the objects under study. The main variables influencing the fringe patterns visibility are discussed and measurements are performed to obtain the values of these variables in the performed experiments. The coefficient of expansion of an alloy is measured at temperatures ranging from 797 C to 986 C. Excellent agreement is found between the measured values and those provided by the manufacturer.

Measurement of strains at high temperatures by means of a portable holographic moire camera

NASA Technical Reports Server (NTRS)

Sciammarella, C. A.; Bhat, G.; Shao, Y.

1989-01-01

Electronic holographic moire is utilized to measure strains at temperatures up to 1000 C. A CW laser operating at 50 mW and at the wavelength of 632.8 nm is used to illuminate the objects under study. The main variables influencing the fringe patterns visibility are discussed and measurements are performed to obtain the values of these variables in the performed experiments. The coefficient of expansion of an alloy is measured at temperatures ranging from 797 C to 986 C. Excellent agreement is found between the measured values and those provided by the manufacturer.

Refractory clad transient internal probe for magnetic field measurements in high temperature plasmas

NASA Astrophysics Data System (ADS)

Kim, Hyundae; Cellamare, Vincent; Jarboe, Thomas R.; Mattick, Arthur T.

2005-05-01

The transient internal probe (TIP) is a diagnostic for local internal field measurements in high temperature plasmas. A verdet material, which rotates the polarization angle of the laser light under magnetic fields, is launched into a plasma at about 1.8km/s. A linearly polarized Ar+ laser illuminates the probe in transit and the light retroreflected from the probe is analyzed to determine the local magnetic field profiles. The TIP has been used for magnetic field measurements on the helicity injected torus where electron temperature Te⩽80eV. In order to apply the TIP in higher temperature plasmas, refractory clad probes have been developed utilizing a sapphire tube, rear disc, and a MgO window on the front. The high melting points of these refractory materials should allow probe operation at plasma electron temperatures up to Te˜300eV. A retroreflecting probe has also been developed using "catseye" optics. The front window is replaced with a plano-convex MgO lens, and the back surface of the probe is aluminized. This approach reduces spurious polarization effects and provides refractory cladding for the probe entrance face. In-flight measurements of a static magnetic field demonstrate the ability of the clad probes to withstand gun-launch acceleration, and provide high accuracy measurements of magnetic field.

Thermoelectric Control Of Temperatures Of Pressure Sensors

NASA Technical Reports Server (NTRS)

Burkett, Cecil G., Jr.; West, James W.; Hutchinson, Mark A.; Lawrence, Robert M.; Crum, James R.

1995-01-01

Prototype controlled-temperature enclosure containing thermoelectric devices developed to house electronically scanned array of pressure sensors. Enclosure needed because (1) temperatures of transducers in sensors must be maintained at specified set point to ensure proper operation and calibration and (2) sensors sometimes used to measure pressure in hostile environments (wind tunnels in original application) that are hotter or colder than set point. Thus, depending on temperature of pressure-measurement environment, thermoelectric devices in enclosure used to heat or cool transducers to keep them at set point.

Electron Heating and Quasiparticle Tunnelling in Superconducting Charge Qubits

NASA Technical Reports Server (NTRS)

Shaw, M. D.; Bueno, J.; Delsing, P.; Echternach, P. M.

2008-01-01

We have directly measured non-equilibrium quasiparticle tunnelling in the time domain as a function of temperature and RF carrier power for a pair of charge qubits based on the single Cooper-pair box, where the readout is performed with a multiplexed quantum capacitance technique. We have extracted an effective electron temperature for each applied RF power, using the data taken at the lowest power as a reference curve. This data has been fit to a standard T? electron heating model, with a reasonable correspondence with established material parameters.

Annealing shallow traps in electron beam irradiated high mobility metal-oxide-silicon transistors

NASA Astrophysics Data System (ADS)

Kim, Jin-Sung; Tyryshkin, Alexei; Lyon, Stephen

In metal-oxide-silicon (MOS) quantum devices, electron beam lithography (EBL) is known to create defects at the Si/SiO2 interface which can be catastrophic for single electron control. Shallow traps ( meV), which only manifest themselves at low temperature ( 4 K), are especially detrimental to quantum devices but little is known about annealing them. In this work, we use electron spin resonance (ESR) to measure the density of shallow traps in two sets of high mobility (μ) MOS transistors. One set (μ=14,000 cm2/Vs) was irradiated with an EBL dose (10 kV, 40 μC/cm2) and was subsequently annealed in forming gas while the other remained unexposed (μ=23,000 cm2/Vs). Our ESR data show that the forming gas anneal is sufficient to remove shallow traps generated by the EBL dose over the measured shallow trap energy range (0.3-4 meV). We additionally fit these devices' conductivity data to a percolation transition model and extract a zero temperature percolation threshold density, n0 ( 9 ×1010 cm-2 for both devices). We find that the extracted n0 agrees within 15 % with our lowest temperature (360 mK) ESR measurements, demonstrating agreement between two independent methods of evaluating the interface.

Acceleration of auroral electrons in parallel electric fields

NASA Technical Reports Server (NTRS)

Kaufmann, R. L.; Walker, D. N.; Arnoldy, R. L.

1976-01-01

Rocket observations of auroral electrons are compared with the predictions of a number of theoretical acceleration mechanisms that involve an electric field parallel to the earth's magnetic field. The theoretical models are discussed in terms of required plasma sources, the location of the acceleration region, and properties of necessary wave-particle scattering mechanisms. We have been unable to find any steady state scatter-free electric field configuration that predicts electron flux distributions in agreement with the observations. The addition of a fluctuating electric field or wave-particle scattering several thousand kilometers above the rocket can modify the theoretical flux distributions so that they agree with measurements. The presence of very narrow energy peaks in the flux contours implies a characteristic temperature of several tens of electron volts or less for the source of field-aligned auroral electrons and a temperature of several hundred electron volts or less for the relatively isotropic 'monoenergetic' auroral electrons. The temperature of the field-aligned electrons is more representative of the magnetosheath or possibly the ionosphere as a source region than of the plasma sheet.

Thermoelectric power of PrMg3

NASA Astrophysics Data System (ADS)

Isikawa, Yosikazu; Somiya, Kazuya; Koyanagi, Huruto; Mizushima, Toshio; Kuwai, Tomohiko; Tayama, Takashi

2010-01-01

PrMg3 is supposed to be one of the strongly correlated electron systems originated from the hybridization between the Pr 4f and conduction electrons, because the gigantic electronic specific heat coefficient C/T was observed at low temperatures. However, a typical behaviour of - ln T dependence was not observed in the temperature dependence of the electrical resistivity. The thermoelectric power S is a powerful tool to investigate the density of states at the Fermi energy. We measured carefully the thermoelectric power of PrMg3 in the temperature range between 2 and 300 K. S is extremely small, ranged within ±1 μV/K over the whole temperature. The value of S/T at low temperature limit was also significantly smaller than expected from the specific heat results. We therefore conclude that the density of state at the Fermi level is not enhanced in PrMg3.

Measurement of threshold temperature effects in dissociative electron attachment to HI and DI

NASA Technical Reports Server (NTRS)

Chutjian, A.; Alajajian, S. H.; Man, K.-F.

1990-01-01

From accurate spectroscopic constants it is found that the thermal dissociative-attachment process (DA) in DI should be exothermic only for rotational levels J greater than 8 in v = O. Here, measurement of an enhancement of DA with rotational temperature T in the range 298-468 K is reported. The effect is easily accounted for by the increase in total fractional population of excited J levels in DI relative to HI. The effect affords a rotational analog to the use of vibrationally excited molecules (e.g., HCl) in a plasma to control electron conduction.

Near-infrared and ultraviolet spectrophotometry of the young planetary nebula Hubble 12

NASA Technical Reports Server (NTRS)

Rudy, Richard J.; Rossano, George S.; Erwin, Peter; Puetter, R. C.; Feibelman, Walter A.

1993-01-01

The young planetary nebula Hubble 12 is observed using near-IR and UV spectrophotometry. The brightness of the O I lines, which is greater than in any other planetary nebula yet measured, indicates that fluorescent excitation by stellar continuum is the principal mechanism generating these lines. Extinction, electron density, and electron temperature are determined using infrared measurements combined with UV data and published optical observations. The range in extinction, density, and temperature implies that, within the ionized region, pockets of emission with distinctly different conditions exist. Logarithmic abundances for helium, oxygen, and sulfur are presented.

Boiling Heat Transfer Measurements on Highly Conductive Surfaces Using Microscale Heater and Temperature Arrays

NASA Technical Reports Server (NTRS)

Kim, J.; Bae, S. W.; Whitten, M. W.; Mullen, J. D.; Quine, R. W.; Kalkur, T. S.

1999-01-01

Two systems have been developed to study boiling heat transfer on the microscale. The first system utilizes a 32 x 32 array of diodes to measure the local temperature fluctuations during boiling on a silicon wafer heated from below. The second system utilizes an array of 96 microscale heaters each maintained at constant surface temperature using electronic feedback loops. The power required to keep each heater at constant temperature is measured, enabling the local heat transfer coefficient to be determined. Both of these systems as well as some preliminary results are discussed.

Electron-ion temperature equilibration in warm dense tantalum

DOE PAGES

Doppner, T; LePape, S.; Ma, T.; ...

2014-11-05

We present measurements of electron-ion temperature equilibration in proton-heated tantalum, under warm dense matter conditions. Our results agree with theoretical predictions for metals calculated using input data from ab initio simulations. Furthermore, the fast relaxation observed in the experiment contrasts with much longer equilibration times found in proton heated carbon, indicating that the energy flow pathways in warm dense matter are far from being fully understood.

Room temperature spin diffusion in (110) GaAs/AlGaAs quantum wells

PubMed Central

2011-01-01

Transient spin grating experiments are used to investigate the electron spin diffusion in intrinsic (110) GaAs/AlGaAs multiple quantum well at room temperature. The measured spin diffusion length of optically excited electrons is about 4 μm at low spin density. Increasing the carrier density yields both a decrease of the spin relaxation time and the spin diffusion coefficient Ds. PMID:21711662

Geometry of phase-separated domains in phospholipid bilayers by diffraction-contrast electron microscopy.

PubMed Central

Hui, S W

1981-01-01

The sizes and shapes of solidus (gel) phase domains in the hydrated molecular bilayers of dilauroylphosphatidylcholine/dipalmitoylphasphatidylcholine (DLPC/DPPC) (1:1) and phosphatidylserine (PS)/DPPC (1:2) are visualized directly by low dose diffraction-contrast electron microscopy. The temperature and humidity of the bilayers are controlled by an environmental chamber set in an electron microscope. The contrast between crystalline domains is enhanced by electron optical filtering of the diffraction patterns of the bilayers. The domains are seen as a patchwork in the plane of the bilayer, with an average width of 0.2-0.5 micrometer. The percentage of solidus area measured from diffraction-contrast micrographs at various temperatures agrees in general with those depicted by known phase diagrams. The shape and size of the domains resemble those seen by freeze-fracture in multilamellar vesicles. Temperature-related changes in domain size and in phase boundary per unit area are more pronounced in the less miscible DLPC/DPPC mixture. No significant change in these geometric parameters with temperature is found in the PS/DPPC mixture. Mapping domains by their molecular diffraction signals not only verifies the existance of areas of different molecular packing during phase separation but also provides a quantitative measurement of structural boundaries and defects in lipid bilayers. Images FIGURE 1 FIGURE 3 FIGURE 6 PMID:6894707

Experimental investigation of adiabatic compression and heating using collision of an MHD-driven jet with a gas target cloud for magnetized target fusion

NASA Astrophysics Data System (ADS)

Seo, Byonghoon; Li, Hui; Bellan, Paul

2017-10-01

We are studying magnetized target fusion using an experimental method where an imploding liner compressing a plasma is simulated by a high-speed MHD-driven plasma jet colliding with a gas target cloud. This has the advantage of being non-destructive so orders of magnitude more shots are possible. Since the actual density and temperature are much more modest than fusion-relevant values, the goal is to determine the scaling of the increase in density and temperature when an actual experimental plasma is adiabatically compressed. Two new-developed diagnostics are operating and providing data. The first new diagnostic is a fiber-coupled interferometer which measures line-integrated electron density not only as a function of time, but also as a function of position along the jet. The second new diagnostic is laser Thomson scattering which measures electron density and temperature at the location where the jet collides with the cloud. These diagnostics show that when the jet collides with a target cloud the jet slows down substantially and both the electron density and temperature increase. The experimental measurements are being compared with 3D MHD and hybrid kinetic numerical simulations that model the actual experimental geometry.

Correlation of Coronal Plasma Properties and Solar Magnetic Field in a Decaying Active Region

NASA Technical Reports Server (NTRS)

Ko, Yuan-Kuen; Young, Peter R.; Muglach, Karin; Warren, Harry P.; Ugarte-Urra, Ignacio

2016-01-01

We present the analysis of a decaying active region observed by the EUV Imaging Spectrometer on Hinode during 2009 December 7-11. We investigated the temporal evolution of its structure exhibited by plasma at temperatures from 300,000 to 2.8 million degrees, and derived the electron density, differential emission measure, effective electron temperature, and elemental abundance ratios of Si/S and Fe/S (as a measure of the First Ionization Potential (FIP) Effect). We compared these coronal properties to the temporal evolution of the photospheric magnetic field strength obtained from the Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms. We find that, while these coronal properties all decreased with time during this decay phase, the largest change was at plasma above 1.5 million degrees. The photospheric magnetic field strength also decreased with time but mainly for field strengths lower than about 70 Gauss. The effective electron temperature and the FIP bias seem to reach a basal state (at 1.5 x 10(exp 6) K and 1.5, respectively) into the quiet Sun when the mean photospheric magnetic field (excluding all areas <10 G) weakened to below 35 G, while the electron density continued to decrease with the weakening field. These physical properties are all positively correlated with each other and the correlation is the strongest in the high-temperature plasma. Such correlation properties should be considered in the quest for our understanding of how the corona is heated. The variations in the elemental abundance should especially be considered together with the electron temperature and density.

Optical Diagnostics in the Gaseous Electronics Conference Reference Cell

PubMed Central

Hebner, G. A.; Greenberg, K. E.

1995-01-01

A number of laser-induced fluorescence and absorption spectroscopy studies have been conducted using Gaseous Electronics Conference Reference Cells. Laser-induced fluorescence has been used to measure hydrogen atom densities, to measure argon metastable spatial profiles, to determine the sheath electric field, and to infer the electron density and temperature. Absorption spectroscopy, using lamp sources and diode lasers, has been used to measure metastable atom densities in helium and argon discharges and fluorocarbon densities in silicon etching discharges. The experimental techniques and sample results of these investigations are reviewed. PMID:29151748

The Jupiter hot plasma torus - Observed electron temperature and energy flows

NASA Technical Reports Server (NTRS)

Brown, R. A.

1981-01-01

The detection of the optical emission /O I/ 6300 A (8 + or - 4 R) and /S III/ 6312 A (48 + or - 5 R) is reported. It is noted that these emissions are indicators of the ion source morphology and the plasma physical state and that the S III emitters have a kinetic temperature of approximately 10 to the 6th K. When combined with observations of UV lines from the same species, the optical measurements separately imply effective electron temperatures for radiative processes that are mutually consistent (approximately 50,000 K).

Transport and reconnection in tokamak sawteeth.

PubMed

Gentle, K W; Austin, M E; Phillips, P E

2003-12-19

The core of a tokamak discharge often undergoes periodic relaxation oscillations, sawteeth, as the steepening current and temperature profiles are flattened by fast reconnection events. Careful analysis of the electron temperature evolution over this cycle gives an estimate of the energy dissipated in the electrons during reconnection and a measure of the transport characteristic (energy flux versus temperature gradient) over the range of parameters occurring over the remainder of the cycle. The energy dissipated is consistent with estimates of the loss of poloidal magnetic energy. The transport characteristics exhibit a wide range of behaviors.

Temperature dependence of Brillouin light scattering spectra of acoustic phonons in silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo

2015-02-02

Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. The need for a better understanding of such non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report the measured BLS spectra of silicon at different temperatures. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in ordermore » to evaluate their potential use as temperature sensors for acoustic phonons.« less

Resistivity of a simple metal from room temperature to 10 to the 6th K

NASA Astrophysics Data System (ADS)

Milchberg, H. M.; Freeman, R. R.; Davey, S. C.; More, R. M.

1988-11-01

The resistivity of nearly solid-density Al was measured as a function of temperature over 4 orders of magnitude above ambient by observing the self-reflection of an intense, less than 0.5 psec, 308-nm light pulse incident on a planar Al target. As an increasing function of electron temperature, the resistivity is observed initially to increase, reach a maximum which is relatively constant over an extended temperature range, and then decrease at the highest temperatures. The broad maximum is interpreted as resistivity saturation, a condition in which the mean free path of the conduction electrons reaches a minimum value as a function of temperature, regardless of the extent of any further disorder in the material.

Temperature grid sensor for the measurement of spatial temperature distributions at object surfaces.

PubMed

Schäfer, Thomas; Schubert, Markus; Hampel, Uwe

2013-01-25

This paper presents results of the development and application of a new temperature grid sensor based on the wire-mesh sensor principle. The grid sensor consists of a matrix of 256 Pt1000 platinum chip resistors and an associated electronics that measures the grid resistances with a multiplexing scheme at high speed. The individual sensor elements can be spatially distributed on an object surface and measure transient temperature distributions in real time. The advantage compared with other temperature field measurement approaches such as infrared cameras is that the object under investigation can be thermally insulated and the radiation properties of the surface do not affect the measurement accuracy. The sensor principle is therefore suited for various industrial monitoring applications. Its applicability for surface temperature monitoring has been demonstrated through heating and mixing experiments in a vessel.

Electron beam fluorescence measurements in the Boeing hypersonic shock tunnel

NASA Technical Reports Server (NTRS)

Price, Linwood L.; Williams, W. Dan; Powell, H. M.

1992-01-01

The Calspan electron beam fluorescence (EBF) measurement system is described along with the results of measurements made in hypersonic flow. Numerous self-emitting metallic species were identified, many of which may be associated with an aging/erosion process within the B30HST. Because there were only 16 tunnel runs, it was only possible to obtain spectral measurements over a limited range of wavelengths and time sampling periods. Many spectral features of the flow remain uninvestigated. Because flow self-emission is important to all optical diagnostic techniques, it is recommended that additional spectral studies by performed. The three electron beam-excited species that were identified are nitrogen, helium, and nitric oxide. The high metallic radiation background interfered with attempts to obtain the time-wise variation of N2 density and He radiation with the optical fiber/PMT channels. In the case of the N2 density measurements the result of interference was increased uncertainty. Unfortunately, the interference caused the time-wise He measurements to fail completely. It is recommended that the electron beam be modulated to provide discrimination against the background radiation in future N2 density measurements. Careful data reduction produced useful measurements of N2 vibrational temperature, even though the high background from metallic species significantly increased measurement uncertainty. Perhaps the recommended additional spectral studies would reveal N2(+) First Negative System band-pair regions having less background. Detection of the He arrival was easily accomplished with the spectrometer/array detector system. Because of this, it is recommended that this means of detecting He arrival be used in the future. With proper calibrations of the system an He number density could be obtained. Although the flow conditions were out of limits for the run in which the NO spectrum was recorded, the usefulness of the NO spectrum for determination of free-stream rotational temperature was demonstrated and should be exploited in future experiments. Indeed, based on the strong NO signals, it is recommended that lower resolution NO spectra be obtained to provide a measure of NO vibrational temperature in the same manner that the N2 temperature was obtained.

Electron temperature maps of the low solar corona: ISCORE results from the total solar eclipse of 1 August 2008 in China

NASA Astrophysics Data System (ADS)

Reginald, Nelson L.; Davila, Joseph M.; St. Cyr, Orville C.; Rabin, Douglas M.

2017-06-01

We conducted an experiment in conjunction with the total solar eclipse of 1 August 2008 in China to determine the thermal electron temperature in the low solar corona close to the solar limb. The instrument, Imaging Spectrograph of Coronal Electrons (ISCORE), consisted of an 8 inch f/10 Schmidt Cassegrain telescope with a thermoelectrically cooled CCD camera at the focal plane. Results are electron temperatures of 1 MK at 1.08 R⊙ and 1.13 R⊙ from the Sun center in the polar and equatorial regions, respectively. This experiment confirms the results of an earlier experiment conducted in conjunction with the total eclipse of 29 March 2006 in Libya, and results are that at a given coronal height the electron temperature in the polar region is larger than at the equatorial region. In this paper we show the importance of using the correct photospheric spectrum pertinent to the solar activity phase at the time of the experiment, which is a required parameter for modeling the underlying theoretical concept for temperature interpretation of the measured intensity ratios using color filters.

Fluctuations in the electron system of a superconductor exposed to a photon flux

PubMed Central

de Visser, P. J.; Baselmans, J. J. A.; Bueno, J.; Llombart, N.; Klapwijk, T. M.

2014-01-01

In a superconductor, in which electrons are paired, the density of unpaired electrons should become zero when approaching zero temperature. Therefore, radiation detectors based on breaking of pairs promise supreme sensitivity, which we demonstrate using an aluminium superconducting microwave resonator. Here we show that the resonator also enables the study of the response of the electron system of the superconductor to pair-breaking photons, microwave photons and varying temperatures. A large range in radiation power (at 1.54 THz) can be chosen by carefully filtering the radiation from a blackbody source. We identify two regimes. At high radiation power, fluctuations in the electron system caused by the random arrival rate of the photons are resolved, giving a straightforward measure of the optical efficiency (48±8%) and showing an unprecedented detector sensitivity. At low radiation power, fluctuations are dominated by excess quasiparticles, the number of which is measured through their recombination lifetime. PMID:24496036

Mahan excitons in degenerate wurtzite InN: Photoluminescence spectroscopy and reflectivity measurements

NASA Astrophysics Data System (ADS)

Feneberg, Martin; Däubler, Jürgen; Thonke, Klaus; Sauer, Rolf; Schley, Pascal; Goldhahn, Rüdiger

2008-06-01

Unintentionally degenerately doped n -type hexagonal wurtzite InN samples were studied by using Fourier-transform photoluminescence spectroscopy and reflectivity measurements. We found in luminescence overlapping band acceptor (e,A0) transitions related to two different acceptors with a strong enhancement of their intensities close to the Fermi energy of the electrons recombining with the localized holes. Our explanation is in terms of a Fermi-edge singularity of the electrons due to strongly increased electron-hole scattering. Electron-hole pairs with such resonantly enhanced oscillator strengths have been referred to as Mahan excitons. Temperature-dependent reflectivity measurements confirm this interpretation.

New Thomson scattering diagnostic on RFX-mod.

PubMed

Alfier, A; Pasqualotto, R

2007-01-01

This article describes the completely renovated Thomson scattering (TS) diagnostic employed in the modified Reversed Field eXperiment (RFX-mod) since it restarted operation in 2005. The system measures plasma electron temperature and density profiles along an equatorial diameter, measuring in 84 positions with 7 mm spatial resolution. The custom built Nd:YLF laser produces a burst of 10 pulses at 50 Hz with energy of 3 J, providing ten profile measurements in a plasma discharge of about 300 ms duration. An optical delay system accommodates three scattering volumes in each of the 28 interference filter spectrometers. Avalanche photodiodes detect the Thomson scattering signals and allow them to be recorded by means of waveform digitizers. Electron temperature is obtained using an alternative relative calibration method, based on the use of a supercontinuum light source. Rotational Raman scattering in nitrogen has supplied the absolute calibration for the electron density measurements. During RFX-mod experimental campaigns in 2005, the TS diagnostic has demonstrated its performance, routinely providing reliable high resolution profiles.

High-temperature performance of MoS2 thin-film transistors: Direct current and pulse current-voltage characteristics

NASA Astrophysics Data System (ADS)

Jiang, C.; Rumyantsev, S. L.; Samnakay, R.; Shur, M. S.; Balandin, A. A.

2015-02-01

We report on fabrication of MoS2 thin-film transistors (TFTs) and experimental investigations of their high-temperature current-voltage characteristics. The measurements show that MoS2 devices remain functional to temperatures of at least as high as 500 K. The temperature increase results in decreased threshold voltage and mobility. The comparison of the direct current (DC) and pulse measurements shows that the direct current sub-linear and super-linear output characteristics of MoS2 thin-films devices result from the Joule heating and the interplay of the threshold voltage and mobility temperature dependences. At temperatures above 450 K, a kink in the drain current occurs at zero gate voltage irrespective of the threshold voltage value. This intriguing phenomenon, referred to as a "memory step," was attributed to the slow relaxation processes in thin films similar to those in graphene and electron glasses. The fabricated MoS2 thin-film transistors demonstrated stable operation after two months of aging. The obtained results suggest new applications for MoS2 thin-film transistors in extreme-temperature electronics and sensors.

Magnetic response of hybrid ferromagnetic and antiferromagnetic core-shell nanostructures

NASA Astrophysics Data System (ADS)

Khan, U.; Li, W. J.; Adeela, N.; Irfan, M.; Javed, K.; Wan, C. H.; Riaz, S.; Han, X. F.

2016-03-01

The synthesis of FeTiO3-Ni(Ni80Fe20) core-shell nanostructures by a two-step method (sol-gel and DC electrodeposition) has been demonstrated. XRD analysis confirms the rhombohedral crystal structure of FeTiO3(FTO) with space group R3&cmb.macr;. Transmission electron microscopy clearly depicts better morphology of nanostructures with shell thicknesses of ~25 nm. Room temperature magnetic measurements showed significant enhancement of magnetic anisotropy for the permalloy (Ni80Fe20)-FTO over Ni-FTO core-shell nanostructures. Low temperature magnetic measurements of permalloy-FeTiO3 core-shell structure indicated a strong exchange bias mechanism with magnetic coercivity below the antiferromagnetic Neel temperature (TN = 59 K). The exchange bias is attributed to the alignment of magnetic moments in the antiferromagnetic material at low temperature. Our scheme opens a path towards optimum automotive systems and wireless communications wherein broader bandwidths and smaller sizes are required.The synthesis of FeTiO3-Ni(Ni80Fe20) core-shell nanostructures by a two-step method (sol-gel and DC electrodeposition) has been demonstrated. XRD analysis confirms the rhombohedral crystal structure of FeTiO3(FTO) with space group R3&cmb.macr;. Transmission electron microscopy clearly depicts better morphology of nanostructures with shell thicknesses of ~25 nm. Room temperature magnetic measurements showed significant enhancement of magnetic anisotropy for the permalloy (Ni80Fe20)-FTO over Ni-FTO core-shell nanostructures. Low temperature magnetic measurements of permalloy-FeTiO3 core-shell structure indicated a strong exchange bias mechanism with magnetic coercivity below the antiferromagnetic Neel temperature (TN = 59 K). The exchange bias is attributed to the alignment of magnetic moments in the antiferromagnetic material at low temperature. Our scheme opens a path towards optimum automotive systems and wireless communications wherein broader bandwidths and smaller sizes are required. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07946b

Electrostatic and magnetic measurements of turbulence and transport in Extrap T2

NASA Astrophysics Data System (ADS)

Möller, Anders; Sallander, Eva

1999-10-01

Langmuir probe and magnetic pick-up coil measurements are used to study edge turbulence in the Extrap T2 reversed field pinch. Magnetic fluctuations resonant outside the toroidal field reversal surface are observed where previously only fluctuations in the spectra of potential and electron density and temperature have been measured. Results are presented which imply that these fluctuations are coupled to and also correlated to the internally resonant tearing mode fluctuations. Evidence of coupling between low-frequency (<100 kHz) and high-frequency fluctuations is also presented. The normalized floating potential fluctuations are seen to increase with the edge electron temperature. This causes an increase of the potential and density fluctuation driven transport with the temperature which is faster than linear. These results, in combination, are consistent with a picture where internally resonant fluctuations couple to edge fluctuations through radial heat conduction from the stochastic core to the edge.

Long Awaited Fundamental Measurement of the Martian Upper Atmosphere from the Langmuir Probe and Waves Instrument on the MAVEN Mission.

NASA Astrophysics Data System (ADS)

Andersson, Laila; Andrews, David; Ergun, Bob; Delory, Greg; Morooka, Michiko; Fowler, Chris; McEnulty, Tess; Weber, Tristan; Eriksson, Anders; Malaspina, David; Crary, Frank; Mitchell, David; McFadden, Jim; Halekas, Jasper; Larson, Davin; Connerney, Jack; Espley, Jared; Eparvies, Frank

2015-04-01

Electron temperature and density are critical quantities in understanding an upper atmosphere. Approximately 40 years ago, the Viking landers reached the Martian surface, measuring the first (and only) two temperature profiles during it's descent. With the MAVEN mission arriving at Mars details of the Martian ionosphere can agin be studied by a complete plasma package. This paper investigates the first few months of data from the MAVEN mission when the orbit is below 500 km and around the northern hemisphere's terminator. The fo-cus of this presentation is on the different measure-ments that the Langmuir probe and Waves (LPW) in-strument is making on the MAVEN mission. Some of the LPW highlights that will be presented: (a) the long awaited new the electron temperature profiles; (b) the structures observed on the nightside ionosphere; (c) wave-particle insteractions observed below 500 km; and (d) the observed dusty environment at Mars. This presentation is supported by measurements from the other Particle and Fileds (PF) measurements on MAVEN.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Application of two-colour pyrometry for measuring the surface temperature of a body activated by laser pulses

NASA Astrophysics Data System (ADS)

Kirillov, V. M.; Skvortsov, L. A.

2006-08-01

The features of contactless measurements of the surface temperature of bodies by the method of two-colour pyrometry of samples activated by periodic laser pulses are considered. The requirements imposed on the parameters of laser radiation and a measuring circuit are formulated. It is shown experimentally that surface temperatures close to room temperature can be measured with an error not exceeding 3% after elimination of the superfluous static component of the excess temperature. The sensitivity of the method is estimated. Advantages of laser photothermal radiometry with repetitively pulsed excitation of surfaces over the case when samples are subjected to harmonic amplitude-modulated laser radiation are discussed.

Resolving electrical conductivities from collisionally damped plasmons in isochorically heated warm dense aluminum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sperling, P.; Fletcher, L. B.; Chung, H. -K.

2016-03-29

We measure the highly-resolved inelastic x-ray scattering spectrum of isochorically ultrafast heated aluminum. In the x-ray forward scattering spectra the electron temperature could be measured from the down- and upshifted plasmon, where the electron density of ne = 1:8 1023 cm 3 is known a priori. We have studied the plasmon damping by applying electron-particle collision models beyond the Born approximation determining the electrical conductivity of warm dense aluminum.

Suprathermal plasma analyzer for the measurement of low-energy electron distribution in the ionosphere.

PubMed

Shimoyama, M; Oyama, K-I; Abe, T; Yau, A W

2011-07-01

It is commonly believed that an energy transfer from thermal to suprathermal electrons (

The radial gradients and collisional properties of solar wind electrons

NASA Technical Reports Server (NTRS)

Ogilvie, K. W.; Scudder, J. D.

1978-01-01

The plasma electron detector on Mariner 10 is used to obtain measurements of electron density and temperature in the interplanetary medium between heliocentric distances of 0.85 and 0.45 AU. The observations show quantitatively that the core of the electron distribution function can be described as collisional at least for radial distances within 1 AU, since with a very few well-marked exceptions associated with high-speed streams, the Coulomb collisional momentum relaxation length is less than the density scale height at all times and all radial distances at which data were obtained. It is found that the Coulomb energy exchange collisions between the core and the (test) halo population are negligible. The power law exponent of the core temperature is about -0.3, whereas the halo temperature is almost independent of heliocentric distance.

Thermoelectric effects in graphene at high bias current and under microwave irradiation.

PubMed

Skoblin, Grigory; Sun, Jie; Yurgens, August

2017-11-14

We use a split top gate to induce doping of opposite signs in different parts of a graphene field-effect transistor, thereby effectively forming a graphene thermocouple. The thermocouple is sensitive to the electronic temperature in graphene, which can be several hundred kelvin higher than the ambient one at sufficiently high bias current. Combined with the high thermoelectric power of graphene, this allows for i) simple measurements of the electronic temperature and ii) building thermoelectric radiation detectors. A simple prototype graphene thermoelectric detector shows a temperature-independent optical responsivity of around 400 V/W at 94 GHz at temperatures of 4-50 K.

Hopkins Ultraviolet Telescope determination of the Io torus electron temperature

NASA Technical Reports Server (NTRS)

Hall, D. T.; Bednar, C. J.; Durrance, S. T.; Feldman, P. D.; Mcgrath, M. A.; Moos, H. W.; Strobel, D. F.

1994-01-01

Sulfur ion emissions from the Io plasma torus observed by the Hopkins Ultraviolet Telescope (HUT) in 1990 December have been analyzed to determine the effective temperature of the exciting electrons. Spectra were obtained with a long slit that extended from 3.1 to 8.7 Jupiter radii R(sub J) on both dawn and dusk torus ansae. The average temperature of electrons exciting S(2+) emissions from the dawn ansa is (4800 +/- 2400) K lower than on the dusk ansa, a dawn-dusk asymmetry comparable in both sign and magnitude to that measured by the Voyager Ultraviolet Spectrograph (UVS) experiment. Emissions from S(2+) ions are generated in a source region with electron temperatures in the range 32,000-56,000 K; S(3+) ion emissions are excited by electrons that average 20,000-40,000 K hotter. This distinct difference suggests that the S(3+) emission source region is spatially separate from the S(2+) source region. Estimated relative aperture filling factors suggest that the S(3+) emissions originate from a region more extended out of the centrifugal plane than the S(2+) emissions.

Properties of the solar wind electrons between 1 and 3.3 AU from Ulysses thermal noise measurements

NASA Technical Reports Server (NTRS)

Maksimovic, M.; Hoang, S.; Bougeret, J. L.

1995-01-01

In order to describe the distribution function f(v) of the solar wind electrons, the simplest model which is commonly used consists of the sum of two Maxwellians representing two distinct populations: a core (density n(sub c), temperature T(sub c)) and a halo (density n(sub h), temperature T(sub h)). It is possible, with the latter assumptions on the electron f(v), to determine the quasi-thermal noise (QTN) induced on an antenna by the motion of the ambient electrons in the solar wind. Using this distribution and the spectroscopy of thermal noise measurements from the radio receiver on Ulysses in the ecliptic plane, we deduce the total electron density N(sub e), the core temperature T(sub c), and the core and halo kinetic pressures N(sub c)T(sub c) and N(sub h)T(sub h). From these electron parameters, we can define a 'global' electron temperature as T(sub e) = (N(sub c)T(sub c) + N(sub h)T(sub h))/N(sub e). Here we present different radial gradients of T(sub e), between 1 and 3.3 AU, as a function of three classes of N(sub e) at 1 AU: low, intermediate, and high densities. In general all these gradients are found to be positive with different polytrope power law indexes between N(sub e) and T(sub e), which are in general lower than unity. We also show different behaviors of the ratio N(sub h)T(sub h)/N(sub c)T(sub c) for each density class considered. Some possible interpretations for these observations are discussed.

Simulation study on the spatial and temporal characteristics of focused microwave beam discharge in nitrogen

NASA Astrophysics Data System (ADS)

Yang, Wei; Zhou, Qianhong; Dong, Zhiwei

2018-01-01

This paper reports a simulation study on a focused microwave (frequency 9.4 GHz, pulse width 2.5 μs, and peak electric field 1.2 kV/cm) discharge in 200 Pa nitrogen. A one-dimensional (1D) fluid model is based on the wave equation for the microwave field propagating through the gas breakdown plasma, the continuity equations for electron, ion and neutral particle densities, and the energy balance equations for mean electron temperature, and nitrogen vibrational and translational temperatures. These equations are numerically solved in a self-consistent manner with a simplified plasma chemistry set, in which the reaction rates involving electrons are calculated from the electron energy distribution function (EEDF) using a two-term expansion method. The spatial and temporal characteristics of the focused microwave breakdown in nitrogen are demonstrated, which include the amplitude of the microwave electric field, and the densities and temperatures of the plasma components. The temporal evolution of the plasma electron density agrees reasonably well with that measured with a microwave interferometer. The spatial-temporal distributions of metastable states are discussed on the plasma chemistry and the character of mean electron temperature. The spatially integrated N2(C3) density shows similar trends with the measured temporal intensity of optical emission spectroscopy, except for a time delay of 100-300 ns. The quantitative discrepancies are explained in light of limitations of the 1D model with a two-term expansion of EEDF. The theoretical model is found to describe the gas breakdown plasma generated by focused microwave beams at least qualitatively.

Electron temperature gradient scale at collisionless shocks.

PubMed

Schwartz, Steven J; Henley, Edmund; Mitchell, Jeremy; Krasnoselskikh, Vladimir

2011-11-18

Shock waves are ubiquitous in space and astrophysics. They transform directed flow energy into thermal energy and accelerate energetic particles. The energy repartition is a multiscale process related to the spatial and temporal structure of the electromagnetic fields within the shock layer. While large scale features of ion heating are known, the electron heating and smaller scale fields remain poorly understood. We determine for the first time the scale of the electron temperature gradient via electron distributions measured in situ by the Cluster spacecraft. Half of the electron heating coincides with a narrow layer several electron inertial lengths (c/ω(pe)) thick. Consequently, the nonlinear steepening is limited by wave dispersion. The dc electric field must also vary over these small scales, strongly influencing the efficiency of shocks as cosmic ray accelerators.

Electron temperature profiles in axial field 2.45 GHz ECR ion source with a ceramic chamber

NASA Astrophysics Data System (ADS)

Abe, K.; Tamura, R.; Kasuya, T.; Wada, M.

2017-08-01

An array of electrostatic probes was arranged on the plasma electrode of a 2.45 GHz microwave driven axial magnetic filter field type negative hydrogen (H-) ion source to clarify the spatial plasma distribution near the electrode. The measured spatial distribution of electron temperature indicated the lower temperature near the extraction hole of the plasma electrode corresponding to the effectiveness of the axial magnetic filter field geometry. When the ratio of electron saturation current to the ion saturation current was plotted as a function of position, the obtained distribution showed a higher ratio near the hydrogen gas inlet through which ground state hydrogen molecules are injected into the source. Though the efficiency in producing H- ions is smaller for a 2.45 GHz source than a source operated at 14 GHz, it gives more volume to measure spatial distributions of various plasma parameters to understand fundamental processes that are influential on H- production in this type of ion sources.

Characterization of spatially resolved high resolution x-ray spectrometers for HEDP and light-source experiments

NASA Astrophysics Data System (ADS)

Hill, K. W.; Bitter, M.; Delgado-Aparicio, L.; Efthimion, P.; Pablant, N.; Lu, J.; Beiersdorfer, P.; Chen, H.; Magee, E.

2014-10-01

A high resolution 1D imaging x-ray spectrometer concept comprising a spherically bent crystal and a 2D pixelated detector is being optimized for diagnostics of small sources such as high energy density physics (HEDP) and synchrotron radiation or x-ray free electron laser experiments. This instrument is used on tokamak experiments for measurement of spatial profiles of Doppler ion temperature and plasma flow velocity, as well as electron temperature. Laboratory measurements demonstrate a resolving power, E/ ΔE of 10,000 and spatial resolution better than 10 μm. Good performance is obtained for Bragg angles ranging from 23 to 63 degrees. Initial tests of the instrument on HEDP plasmas are being performed with a goal of developing spatially resolved ion and electron temperature diagnostics. This work was performed under the auspices of the US DOE by PPPL under Contract DE-AC02-09CH11466 and by LLNL under Contract DE-AC52-07NA27344.

Metallic-like Wilson ratio in the polyaniline hydrochloride conducting polymer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Limelette, P.; Schmaltz, B.; Tran Van, F.

2015-03-28

We report on the calorimetric and magnetic properties of the polyaniline hydrochloride in order to discuss its metallicity. Both the specific heat and the magnetic susceptibility χ have been investigated as a function of temperature from 300 K down to 2 K. The measurements of the specific heat have allowed us to determine the electronic Sommerfeld coefficient γ and the temperature dependence of the susceptibility has revealed a Pauli-like component. By combining χ and γ, the dimensionless Wilson ratio R{sub W}∝χ/γ demonstrates that the universal free electrons limit is reached above 100 K as a strong check of the metallicity of this conductingmore » polymer. By removing the Pauli component from the measured susceptibility, the resulting contribution displays below 100 K a well-defined Curie-like component in agreement with a few percents of spins localized by disorder at low temperatures. These results are therefore consistent with an electronic itinerancy, namely, a metallic state even in the presence of disorder.« less

Observing electron spin resonance between 0.1 and 67 GHz at temperatures between 50 mK and 300 K using broadband metallic coplanar waveguides

NASA Astrophysics Data System (ADS)

Wiemann, Yvonne; Simmendinger, Julian; Clauss, Conrad; Bogani, Lapo; Bothner, Daniel; Koelle, Dieter; Kleiner, Reinhold; Dressel, Martin; Scheffler, Marc

2015-05-01

We describe a fully broadband approach for electron spin resonance (ESR) experiments, where it is possible to tune not only the magnetic field but also the frequency continuously over wide ranges. Here, a metallic coplanar transmission line acts as compact and versatile microwave probe that can easily be implemented in different cryogenic setups. We perform ESR measurements at frequencies between 0.1 and 67 GHz and at temperatures between 50 mK and room temperature. Three different types of samples (Cr3+ ions in ruby, organic radicals of the nitronyl-nitroxide family, and the doped semiconductor Si:P) represent different possible fields of application for the technique. We demonstrate that an extremely large phase space in temperature, magnetic field, and frequency for ESR measurements, substantially exceeding the range of conventional ESR setups, is accessible with metallic coplanar lines.

Terahertz magneto-optical properties of bi- and tri-layer graphene

NASA Astrophysics Data System (ADS)

Mei, Hongying; Xu, Wen; Wang, Chao; Yuan, Haifeng; Zhang, Chao; Ding, Lan; Zhang, Jin; Deng, Chao; Wang, Yifan; Peeters, Francois M.

2018-05-01

Magneto-optical (MO) properties of bi- and tri-layer graphene are investigated utilizing terahertz time-domain spectroscopy (THz TDS) in the presence of a strong magnetic field at room-temperature. In the Faraday configuration and applying optical polarization measurements, we measure the real and imaginary parts of the longitudinal and transverse MO conductivities of different graphene samples. The obtained experimental data fits very well with the classical MO Drude formula. Thus, we are able to obtain the key sample and material parameters of bi- and tri-layer graphene, such as the electron effective mass, the electronic relaxation time and the electron density. It is found that in high magnetic fields the electronic relaxation time τ for bi- and tri-layer graphene increases with magnetic field B roughly in a form τ∼ B2 . Most importantly, we obtain the electron effective mass for bi- and tri-layer graphene at room-temperature under non-resonant conditions. This work shows how the advanced THz MO techniques can be applied for the investigation into fundamental physics properties of atomically thin 2D electronic systems.

Coherent band excitations in CePd 3: A comparison of neutron scattering and ab initio theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goremychkin, Eugene A.; Park, Hyowon; Osborn, Raymond

In common with many strongly correlated electron systems, intermediate valence compounds are believed to display a crossover from a high-temperature regime of incoherently fluctuating local moments to a low-temperature regime of coherent hybridized bands. In this work, we show that inelastic neutron scattering measurements of the dynamic magnetic susceptibility of CePd 3 provides a benchmark for ab initio calculations based on dynamical mean field theory. The magnetic response is strongly momentum dependent thanks to the formation of coherent f-electron bands at low temperature, with an amplitude that is strongly enhanced by local particle-hole interactions. Finally, the agreement between experiment andmore » theory shows that we have a robust first-principles understanding of the temperature dependence of f-electron coherence.« less

Analysis of hydrogen plasma in MPCVD reactor

NASA Astrophysics Data System (ADS)

Shivkumar, Gayathri

The aim of this work is to build a numerical model that can predict the plasma properties of hydrogen plasmas inside a Seki Technotron Corp. AX5200S MPCVD system so that it may be used to understand and optimize the conditions for the growth of carbon nanostructures. A 2D model of the system is used in the finite element high frequency Maxwell solver and heat trasfer solver in COMSOL Multiphysics, where the solvers are coupled with user defined functions to analyze the plasma. A simplified chemistry model is formulated in order to determine the electron temperature in the plasma. This is used in the UDFs which calculate the electron number density as well as electron temperature. A Boltzmann equation solver for electrons in weakly ionized gases under uniform electric fields, called BOLSIG+, is used to obtain certain input parameters required for these UDFs. The system is modeled for several reactor geometries at pressures of 10 Torr and 30 Torr and powers ranging from 300 W to 700 W. The variation of plasma characteristics with changes in input conditions is studied and the electric field, electron number density, electron temperature and gas temperature are seen to increase with increasing power. Electric field, electron number density and electron temperature decrease and gas temperature increases with increasing pressure. The modeling results are compared with experimental measurements and a good agreement is found after calibrating the parameter gamma in Funer's model to match experimental electron number densities. The gas temperature is seen to have a weak dependence on power and a strong dependence on gas pressure. On an average, the gas temperature at a point 5 mm above the center of the puck increases from about 1000 K at a pressure of 10 Torr to about 1500 K at 30 Torr. The inclusion of the pillar produces an increase in the maximum electron number density of approximately 50%; it is higher under some conditions. It increases the maximum electron temperature by about 70% and at 500 W and 30 Torr, the maximum gas temperature is seen to increase by 50%. The effect of susceptor position is studied and it is seen that the only condition favorable to growth would be to raise it by less than 25 mm from the initial reference position or to maintain it at the same level.

A frequency tunable, eight-channel correlation ECE system for electron temperature turbulence measurements on the DIII-D tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sung, C., E-mail: csung@physics.ucla.edu; Peebles, W. A.; Wannberg, C.

2016-11-15

A new eight-channel correlation electron cyclotron emission diagnostic has recently been installed on the DIII-D tokamak to study both turbulent and coherent electron temperature fluctuations under various plasma conditions and locations. This unique system is designed to cover a broad range of operation space on DIII-D (1.6-2.1 T, detection frequency: 72-108 GHz) via four remotely selected local oscillators (80, 88, 96, and 104 GHz). Eight radial locations are measured simultaneously in a single discharge covering as much as half the minor radius. In this paper, we present design details of the quasi-optical system, the receiver, as well as representative datamore » illustrating operation of the system.« less

Low Noise in a Diffusion-Cooled Hot-Electron Mixer at 2.5 THz

NASA Technical Reports Server (NTRS)

Karasik, B. S.; Gaidis, M. C.; McGrath, W. R.; Bumble, B.; LeDuc, H. G.

1997-01-01

The noise performance of a Nb hot-electron bolometer mixer at 2.5 THz has been investigated. The devices are fabricated from a 12-nm-thick Nb film, and have a 0.30 micrometer x 0.15 micrometer in-plane size, thus exploiting diffusion as the electron cooling mechanism. The rf coupling was provided by a twin-slot planar antenna on an elliptical Si lens. The experimentally measured double sideband noise temperature of the receiver was as low as 2750 +/- 250 K with an estimated mixer noise temperature of approximately equal 900 K. The mixer bandwidth derived from both noise bandwidth and IF impedance measurements was approximately equal 1.4 GHz. These results demonstrate the low-noise operation of the diffusion-cooled bolometer mixer above 2 THz.

Pioneer Venus Orbiter planar retarding potential analyzer plasma experiment

NASA Technical Reports Server (NTRS)

Knudsen, W. C.; Bakke, J.; Spenner, K.; Novak, V.

1980-01-01

The retarding potential analyzer (RPA) on the Pioneer Venus Orbiter Mission measures most of the thermal plasma parameters within and near the Venusian ionosphere. Parameters include total ion concentration, concentrations of the more abundant ions, ion temperatures, ion drift velocity, electron temperature, and low-energy (0-50 eV) electron distribution function. Several functions not previously used in RPA's were developed and incorporated into this instrument to accomplish these measurements on a spinning spacecraft with a small bit rate. The more significant functions include automatic electrometer ranging with background current compensation; digital, quadratic retarding potential step generation for the ion and low-energy electron scans; a current sampling interval of 2 ms throughout all scans; digital logic inflection point detection and data selection; and automatic ram direction detection.

Design and first plasma measurements of the ITER-ECE prototype radiometer.

PubMed

Austin, M E; Brookman, M W; Rowan, W L; Danani, S; Bryerton, E W; Dougherty, P

2016-11-01

On ITER, second harmonic optically thick electron cyclotron emission (ECE) in the range of 220-340 GHz will supply the electron temperature (T e ). To investigate the requirements and capabilities prescribed for the ITER system, a prototype radiometer covering this frequency range has been developed by Virginia Diodes, Inc. The first plasma measurements with this instrument have been carried out on the DIII-D tokamak, with lab bench tests and measurements of third through fifth harmonic ECE from high T e plasmas. At DIII-D the instrument shares the transmission line of the Michelson interferometer and can simultaneously acquire data. Comparison of the ECE radiation temperature from the absolutely calibrated Michelson and the prototype receiver shows that the ITER radiometer provides accurate measurements of the millimeter radiation across the instrument band.

Anisotropic electron temperature measurements without knowing the spectral transmissivity for a JT-60SA Thomson scattering diagnostic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tojo, H.; Hatae, T.; Yatsuka, E.

2012-10-15

This paper focuses on a method for measuring the electron temperature (T{sub e}) without knowing the transmissivity using Thomson scattering diagnostic with a double-pass scattering system. Application of this method for measuring the anisotropic T{sub e}, i.e., the T{sub e} in the directions parallel (T{sub e Double-Vertical-Line Double-Vertical-Line }) and perpendicular (T{sub e Up-Tack }) to the magnetic field, is proposed. Simulations based on the designed parameters for a JT-60SA indicate the feasibility of the measurements except in certain T{sub e} ranges, e.g., T{sub e Double-Vertical-Line Double-Vertical-Line }{approx} 3.5T{sub e Up-Tack} at 120 Degree-Sign of the scattering angle.

Magnetism of epitaxial Tb films on W(110) studied by spin-polarized low-energy electron microscopy

NASA Astrophysics Data System (ADS)

Prieto, J. E.; Chen, Gong; Schmid, A. K.; de la Figuera, J.

2016-11-01

Thin epitaxial films of Tb metal were grown on a clean W(110) substrate in ultrahigh vacuum and studied in situ by low-energy electron microscopy. Annealed films present magnetic contrast in spin-polarized low-energy electron microscopy. The energy dependence of the electron reflectivity was determined and a maximum value of its spin asymmetry of about 1% was measured. The magnetization direction of the Tb films is in-plane. Upon raising the temperature, no change in the domain distribution is observed, while the asymmetry in the electron reflectivity decreases when approaching the critical temperature, following a power law ˜(1-T /TC) β with a critical exponent β of 0.39.

Effect of calcination routes on phase formation of BaTiO3 and their electronic and magnetic properties

NASA Astrophysics Data System (ADS)

Majumder, Supriyo; Choudhary, R. J.; Tripathi, M.; Phase, D. M.

2018-05-01

We have investigated the phase formation and correlation between electronic and magnetic properties of oxygen deficient BaTiO3 ceramics, synthesized by solid state reaction method, following different calcination paths. The phase analysis divulge that a higher calcination temperature above 1000° C is favored for tetragonal phase formation than the cubic phase. The core level X-ray photo electron spectroscopy measurements confirm the presence of oxygen vacancies and oxygen vacancy mediated Ti3+ states. As the calcination temperature and calcination time increases these oxygen vacancies and hence Ti3+ concentrations reduce in the sample. The temperature dependent magnetization curves suggest unexpected magnetic ordering, which may be due to the presence of unpaired electron at the t2g state (d1) of nearest-neighbor Ti atoms. In magnetization vs magnetic field isotherms, the regular decrease of saturation moment value with increasing calcination temperature and calcination time, can be discussed considering the amount of oxygen deficiency induced Ti3+ concentrations, present in the sample.

The effects of measurement site and ambient temperature on body temperature values in healthy older adults: a cross-sectional comparative study.

PubMed

Lu, Shu-Hua; Dai, Yu-Tzu; Yen, Chung-Jen

2009-11-01

Accurate baseline body temperature measurement is essential for assessment. Tympanic membrane temperature (TMT) measurement is popular, but there is no consensus on whether it is as accurate as oral temperature (OT) for use with the elderly at varying ambient temperature levels. To test agreement between TMT and OT measurement of body temperature among an elderly population; and to explore whether agreement between the two sites depends on ambient temperature. A cross-sectional comparison study. Two samples of older community-dwelling adults were recruited from 17 community senior citizen centers in Taipei, Taiwan in winter (n=262) and summer (n=257) of 2007. TMT and OT were simultaneously measured by electronic infrared ear thermometer and electronic digital thermometer. Ambient temperatures measured by digital thermo-hygrometer of the data collection setting were recorded when body temperature was taken. In winter mean TMT was 36.64 degrees C (S.D. 0.37), and mean OT was 36.74 degrees C (S.D. 0.18). In summer, the mean TMT was 37.05 degrees C (S.D. 0.30) and mean OT was 36.85 degrees C (S.D. 0.22). The relationship between TMT and OT were r=0.42 (p<0.001) in winter and r=0.57 (p<0.001) in summer. The values of OT were used as standard to assess the accuracy of the measurement. The bias between TMT and OT was -0.10 degrees C (S.D. 0.34) and 95% limits of agreement were 0.57 and -0.77 degrees C in winter; and bias was 0.20 degrees C (S.D. 0.25) and 95% limits of agreement were 0.69 and -0.29 degrees C in summer. The findings of this study demonstrate that the TMT has high variability that may under or over estimate body temperatures. There is a lack of agreement in body temperatures values between TMT and OT in community-dwelling elderly in both winter and summer. OT was more stable than TMT regardless of ambient temperature influences. Therefore, the oral cavity is preferable to the TM site for temperature measurement in alert elderly. The limitation of this study is that hospitalized patients who are most likely to need temperature measurement are not included in this study.

MAVEN Observations of the Effects of Crustal Magnetic Fields on the Mars Ionosphere

NASA Astrophysics Data System (ADS)

Vogt, M. F.; Flynn, C. L.; Withers, P.; Andersson, L.; Girazian, Z.; Mitchell, D. L.; Xu, S.; Connerney, J. E. P.; Espley, J. R.

2017-12-01

Mars lacks a global intrinsic magnetic field but possesses regions of strong crustal magnetic field that influence the planetary interaction with the solar wind and affect the structure and dynamics of the ionosphere. Since entering Mars orbit in 2014, the MAVEN spacecraft has collected comprehensive measurements of the local plasma and magnetic field properties in the Martian dayside ionosphere. Here we discuss how crustal magnetic fields affect the structure, composition, and electrodynamics of the Martian ionosphere as seen by MAVEN. We present a survey of 17 months of MAVEN LPW measurements of the electron density and temperature in the dayside ionosphere and show that, above 200 km altitude, regions of strong crustal magnetic fields feature cooler electron temperatures and enhanced electron densities compared to regions with little or no crustal magnetic field. We also report on the influence of the magnetic field direction and topology on MAVEN electron density measurements in the southern crustal field areas, particularly in magnetic cusp regions. Finally, we discuss the effects of crustal magnetic fields on plasma boundaries like the ionopause, located at the top of the ionosphere and marked by a sharp and substantial gradient in the electron density.

Improved electron collisional line broadening for low-temperature ions and neutrals in plasma modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johns, H. M.; Kilcrease, D. P.; Colgan, J.

In this study, electron collisional broadening of observed spectral lines depends on plasma electron temperature and density. Including this effect in models of measured spectra is necessary to determine plasma conditions; however, computational limits make accurate line broadening treatments difficult to implement in large-scale plasma modeling efforts. In this paper, we report on improvements to the treatment of electron collisional line broadening and illustrate this with calculations using the Los Alamos ATOMIC code. We implement the Dimitrijevic and Konjevic modified semi-empirical model Dimitrijevic and Konjevic (1986 Astron. and Astrophy. 163 297 and 1987 Astron. Astrophys. 172 345), which we amendmore » by employing oscillator strengths from Hartree–Fock calculations. This line broadening model applies to near-neutral plasmas with electron temperatures of Te ~ 1 eV and electron densities of N e ~10 17 cm -3. We evaluate the D.K.-inspired model against the previous hydrogenic approach in ATOMIC through comparison to NIST-rated measurements for selected neutral and singly-ionized Ca, O, Fe, and Sn lines using both fine-structure and configuration-averaged oscillator strengths. The new D.K.-inspired model is significantly more accurate than the previous hydrogenic model and we find the use of configuration-averaged oscillator strengths a good approximation for applications such as LIBS (laser induced breakdown spectroscopy), for which we demonstrate the use of the D.K.-inspired model.« less

Improved electron collisional line broadening for low-temperature ions and neutrals in plasma modeling

DOE PAGES

Johns, H. M.; Kilcrease, D. P.; Colgan, J.; ...

2015-09-29

In this study, electron collisional broadening of observed spectral lines depends on plasma electron temperature and density. Including this effect in models of measured spectra is necessary to determine plasma conditions; however, computational limits make accurate line broadening treatments difficult to implement in large-scale plasma modeling efforts. In this paper, we report on improvements to the treatment of electron collisional line broadening and illustrate this with calculations using the Los Alamos ATOMIC code. We implement the Dimitrijevic and Konjevic modified semi-empirical model Dimitrijevic and Konjevic (1986 Astron. and Astrophy. 163 297 and 1987 Astron. Astrophys. 172 345), which we amendmore » by employing oscillator strengths from Hartree–Fock calculations. This line broadening model applies to near-neutral plasmas with electron temperatures of Te ~ 1 eV and electron densities of N e ~10 17 cm -3. We evaluate the D.K.-inspired model against the previous hydrogenic approach in ATOMIC through comparison to NIST-rated measurements for selected neutral and singly-ionized Ca, O, Fe, and Sn lines using both fine-structure and configuration-averaged oscillator strengths. The new D.K.-inspired model is significantly more accurate than the previous hydrogenic model and we find the use of configuration-averaged oscillator strengths a good approximation for applications such as LIBS (laser induced breakdown spectroscopy), for which we demonstrate the use of the D.K.-inspired model.« less

In Situ Irradiation and Measurement of Triple Junction Solar Cells at Low Intensity, Low Temperature (LILT) Conditions

NASA Technical Reports Server (NTRS)

Harris, R.D.; Imaizumi, M.; Walters, R.J.; Lorentzen, J.R.; Messenger, S.R.; Tischler, J.G.; Ohshima, T.; Sato, S.; Sharps, P.R.; Fatemi, N.S.

2008-01-01

The performance of triple junction InGaP/(In)GaAs/Ge space solar cells was studied following high energy electron irradiation at low temperature. Cell characterization was carried out in situ at the irradiation temperature while using low intensity illumination, and, as such, these conditions reflect those found for deep space, solar powered missions that are far from the sun. Cell characterization consisted of I-V measurements and quantum efficiency measurements. The low temperature irradiations caused substantial degradation that differs in some ways from that seen after room temperature irradiations. The short circuit current degrades more at low temperature while the open circuit voltage degrades more at room temperature. A room temperature anneal after the low temperature irradiation produced a substantial recovery in the degradation. Following irradiation at both temperatures and an extended room temperature anneal, quantum efficiency measurement suggests that the bulk of the remaining damage is in the (In)GaAs sub-cell

Cryogenic Multichannel Pressure Sensor With Electronic Scanning

NASA Technical Reports Server (NTRS)

Hopson, Purnell, Jr.; Chapman, John J.; Kruse, Nancy M. H.

1994-01-01

Array of pressure sensors operates reliably and repeatably over wide temperature range, extending from normal boiling point of water down to boiling point of nitrogen. Sensors accurate and repeat to within 0.1 percent. Operate for 12 months without need for recalibration. Array scanned electronically, sensor readings multiplexed and sent to desktop computer for processing and storage. Used to measure distributions of pressure in research on boundary layers at high Reynolds numbers, achieved by low temperatures.

Electron-Beam Diagnostic Methods for Hypersonic Flow Diagnostics

NASA Technical Reports Server (NTRS)

1994-01-01

The purpose of this work was the evaluation of the use of electron-bean fluorescence for flow measurements during hypersonic flight. Both analytical and numerical models were developed in this investigation to evaluate quantitatively flow field imaging concepts based upon the electron beam fluorescence technique for use in flight research and wind tunnel applications. Specific models were developed for: (1) fluorescence excitation/emission for nitrogen, (2) rotational fluorescence spectrum for nitrogen, (3) single and multiple scattering of electrons in a variable density medium, (4) spatial and spectral distribution of fluorescence, (5) measurement of rotational temperature and density, (6) optical filter design for fluorescence imaging, and (7) temperature accuracy and signal acquisition time requirements. Application of these models to a typical hypersonic wind tunnel flow is presented. In particular, the capability of simulating the fluorescence resulting from electron impact ionization in a variable density nitrogen or air flow provides the capability to evaluate the design of imaging instruments for flow field mapping. The result of this analysis is a recommendation that quantitative measurements of hypersonic flow fields using electron-bean fluorescence is a tractable method with electron beam energies of 100 keV. With lower electron energies, electron scattering increases with significant beam divergence which makes quantitative imaging difficult. The potential application of the analytical and numerical models developed in this work is in the design of a flow field imaging instrument for use in hypersonic wind tunnels or onboard a flight research vehicle.

Rapid mortality of pest arthropods by direct exposure to a dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Bures, Brian Lee

The spread of arthropods due to trade of agricultural commodities and travel of humans is a significant problem in many countries. Limiting the movement of pest species is commonly achieved by the use of chemical pesticides at quarantine facilities. One potential alternative to chemical pesticides is direct exposure of contaminated commodities to ambient pressure electrical discharges. The arthropods are directly exposed to a 5.0 cm helium discharge with power densities on the order of 60 mW/cm3. Direct measurement of chemical species and ambient gas temperature shows the DBD treatment remains effective when the chemically reactive species are suppressed by helium, and when the ambient gas temperature of the discharge is below 40°C. In addition to gas temperature measurements and chemical species identification, the electron temperature and electron density were measured using the neutral bremsstrahlung continuum technique. This study is the first successful implementation of the neutral bremsstrahlung continuum emission diagnostic to a barrier discharge. The primary advantages of the diagnostic for barrier discharges are the measurement is passive and the spatial resolution is only limited by the collimation of the light and the sensitivity of the detector. Although the electron temperature (1.0--1.5 eV) and electron density (˜108 cm-3) are modest, non-chemical dielectric barrier discharge (DBD) treatment of arthropods has proven effective in significantly reducing the population of some arthropods including human body lice, green peach aphids, and western flower thrips. However, the treatment was not universally effective on all arthropod species. German cockroaches and citrus mealy bugs showed substantial resistance to the treatment. The study has shown the treatment does not always induce instant mortality: however, the mortality increases over a 24 hr-period after treatment. Based upon visual observation and the time after treatment to reach maximum mortality, the mode of action is either direct damage to the nervous system or changes to the hydrocarbon layer that protects the arthropods from dehydration.

Reliability of body temperature measurements in hospitalised older patients.

PubMed

Giantin, Valter; Toffanello, Elena D; Enzi, Giuliano; Perissinotto, Egle; Vangelista, Stefania; Simonato, Matteo; Ceccato, Corrado; Manzato, Enzo; Sergi, Giuseppe

2008-06-01

To compare different body temperature assessment methods in older people and to assess the role of cognitive and functional characteristics in temperature recordings. Axillary gallium-in-glass thermometers are commonly used. Their accuracy depends on the proper placement of the device and their permanence in place for eight minutes. With adequate instruction, well-functioning patients can measure their axillary temperature by themselves, while in cognitively and functionally impaired older people, inadequate understanding of instructions and misplacement of the thermometer might determine significant recording errors. Electronic ear and axillary temperature measurements are faster, but their accuracy has not been demonstrated convincingly with older people. Patients (n = 107; aged 65-104 years) were recruited. Barthel Index and Short Portable Mental Status Questionnaire (SPMSQ) scores were obtained for each patient. Temperature readings were obtained using: the axillary gallium-in-glass thermometer, with (T(nurse)) and without (T(self)) the nurse's assistance; the electronic axillary thermometer (T(el)) and the infrared tympanic thermometer (T(tymp)). The T(nurse) was considered as the reference method. Mean difference and standard deviation (mean +/- SD) in temperature recordings between the different techniques and T(nurse) differed significantly from zero for T(self) (-0.40 SD 0.42) and T(tymp) (+0.19 SD 0.48). No significant differences in temperature recordings emerged between T(nurse) and T(el). In simple linear regression models, the difference between T(self) and T(nurse) significantly correlated with age, gender, SPMSQ score and Barthel Index. Multiple linear regression analysis showed an underestimation of body temperature in older patients with cognitive impairments. Unassisted gallium-in-glass axillary temperature assessment is inadequate, in older patients. The differences between T(self) and T(nurse) are significantly influenced by age and mental decline. T(el) provides adequate accuracy. Relevance to clinical practice. In geriatric settings, the electronic axillary thermometer is a safe and accurate alternative to the more traditional gallium-in-glass thermometer, with the advantage of saving time (five seconds in recording vs. eight minutes).

Operation of SOI P-Channel Field Effect Transistors, CHT-PMOS30, under Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2009-01-01

Electronic systems are required to operate under extreme temperatures in NASA planetary exploration and deep space missions. Electronics on-board spacecraft must also tolerate thermal cycling between extreme temperatures. Thermal management means are usually included in today s spacecraft systems to provide adequate temperature for proper operation of the electronics. These measures, which may include heating elements, heat pipes, radiators, etc., however add to the complexity in the design of the system, increases its cost and weight, and affects its performance and reliability. Electronic parts and circuits capable of withstanding and operating under extreme temperatures would reflect in improvement in system s efficiency, reducing cost, and improving overall reliability. Semiconductor chips based on silicon-on-insulator (SOI) technology are designed mainly for high temperature applications and find extensive use in terrestrial well-logging fields. Their inherent design offers advantages over silicon devices in terms of reduced leakage currents, less power consumption, faster switching speeds, and good radiation tolerance. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. Experimental investigation on the operation of SOI, N-channel field effect transistors under wide temperature range was reported earlier [1]. This work examines the performance of P-channel devices of these SOI transistors. The electronic part investigated in this work comprised of a Cissoid s CHT-PMOS30, high temperature P-channel MOSFET (metal-oxide semiconductor field-effect transistor) device [2]. This high voltage, medium-power transistor is designed for geothermal well logging applications, aerospace and avionics, and automotive industry, and is specified for operation in the temperature range of -55 C to +225 C. Table I shows some specifications of this transistor [2]. The CHT-PMOS30 device was characterized at various temperatures over the range of -190 C to +225 C in terms of its voltage/current characteristic curves. The test temperatures included +22, -50, -100, -150, -175, -190, +50, +100, +150, +175, +200, and +225 C. Limited thermal cycling testing was also performed on the device. These tests consisted of subjecting the transistor to a total of twelve thermal cycles between -190 C and +225 C. A temperature rate of change of 10 C/min and a soak time at the test temperature of 10 minutes were used throughout this work. Post-cycling measurements were also performed at selected temperatures. In addition, re-start capability at extreme temperatures, i.e. power switched on while the device was soaking for a period of 20 minutes at the test temperatures of -190 C and +225 C, was investigated.

Measurement of atmospheric pressure microplasma jet with Langmuir probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Kunning G., E-mail: gabe.xu@uah.edu; Doyle, Steven J.

2016-09-15

A radio frequency argon microplasma jet at atmospheric-pressure is characterized using Langmuir probes. While optical methods are the typical diagnostic for these small scale plasmas, the simplicity and low cost of Langmuir probes makes them an attractive option. The plasma density and electron temperature are measured using existing high-pressure Langmuir probe theories developed for flames and arcs. The density and temperature vary from 1 × 10{sup 16} to 1 × 10{sup 19} m{sup −3} and 2.3 to 4.4 eV, respectively, depending on the operating condition. The density decreases while the electron temperature increases with axial distance from the jet exit. Themore » applicability of the probe theories as well as the effect of collisionality and jet mixing is discussed.« less

Thomson scattering diagnostics of steady state and pulsed welding processes without and with metal vapor

NASA Astrophysics Data System (ADS)

Kühn-Kauffeldt, M.; Marqués, J.-L.; Schein, J.

2015-01-01

Thomson scattering is applied to measure temperature and density of electrons in the arc plasma of the direct current gas tungsten arc welding (GTAW) process and pulsed gas metal arc welding (GMAW) process. This diagnostic technique allows to determine these plasma parameters independent from the gas composition and heavy particles temperature. The experimental setup is adapted to perform measurements on stationary as well as transient processes. Spatial and temporal electron temperature and density profiles of a pure argon arc in the case of the GTAW process and argon arc with the presence of aluminum metal vapor in the case of the GMAW process were obtained. Additionally the data is used to estimate the concentration of the metal vapor in the GMAW plasma.

Improved Estimation of Electron Temperature from Rocket-borne Impedance Probes

NASA Astrophysics Data System (ADS)

Rowland, D. E.; Wolfinger, K.; Stamm, J. D.

2017-12-01

The impedance probe technique is a well known method for determining high accuracy measurements of electron number density in the Earth's ionosphere. We present analysis of impedance probe data from several sounding rockets at low, mid-, and auroral latitudes, including high cadence estimates of the electron temperature, derived from analytical fits to the antenna impedance curves. These estimates compare favorably with independent estimates from Langmuir Probes, but at much higher temporal and spatial resolution, providing a capability to resolve small-scale temperature fluctuations. We also present some considerations for the design of impedance probes, including assessment of the effects of resonance damping due to rocket motion, effects of wake and spin modulation, and aspect angle to the magnetic field.

Multi-channel electronically scanned cryogenic pressure sensor

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Hopson, Purnell, Jr. (Inventor); Kruse, Nancy M. H. (Inventor)

1995-01-01

A miniature, multi-channel, electronically scanned pressure measuring device uses electrostatically bonded silicon dies in a multielement array. These dies are bonded at specific sites on a glass, prepatterned substrate. Thermal data is multiplexed and recorded on each individual pressure measuring diaphragm. The device functions in a cryogenic environment without the need of heaters to keep the sensor at constant temperatures.

Compton scattering measurements from dense plasmas

DOE PAGES

Glenzer, S. H.; Neumayer, P.; Doppner, T.; ...

2008-06-12

Here, Compton scattering techniques have been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, whilemore » in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.« less

Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research.

PubMed

Oh, Jaechul; Weaver, J L; Karasik, M; Chan, L Y

2015-08-01

A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (∼1 ns FWHM) with the intensity of 1.1 × 10(15) W/cm(2). The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 10(21) cm(-3) with the density scale length of 120 μm along the plasma symmetry axis. The resulting n(e) and T(e) profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

High-mobility strained organic semiconductors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Takeya, Jun; Matsui, H.; Kubo, T.; Hausermann, Roger

2016-11-01

Small molecular organic semiconductor crystals form interesting electronic systems of periodically arranged "charge clouds" whose mutual electronic coupling determines whether or not electronic states can be coherent over fluctuating molecules. This presentation focuses on two methods to reduce molecular fluctuation, which strongly restricts mobility of highly mobile charge in single-crystal organic transistors. The first example is to apply external hydrostatic pressure. Using Hall-effect measurement for pentacene FETs, which tells us the extent of the electronic coherence, we found a crossover from hopping-like transport of nearly localized charge to band transport of delocalized charge with full coherence. As the result of temperature dependence measurement, it turned out that reduced molecular fluctuation is mainly responsible for the crossover. The second is to apply uniaxial strain to single-crystal organic FETs. We applied stain by bending thin films of newly synthesized decyldinaphthobenzodithiophene (C10-DNBDT) on plastic substrate so that 3% strain is uniaxially applied. As the result, the room-temperature mobility increased by the factor of 1.7. In-depth analysis using X-ray diffraction (XRD) measurements and density functional theory (DFT) calculations reveal the origin to be the suppression of the thermal fluctuation of the individual molecules, which is confirmed by temperature dependent measurements. Our findings show that compressing the crystal structure directly restricts the vibration of the molecules, thus suppressing dynamic disorder, a unique mechanism in organic semiconductors. Since strain can easily be induced during the fabrication process, these findings can directly be exploited to build high performance organic devices.

RF Shot Noise Measurements in Au Atomic-scale Junctions

NASA Astrophysics Data System (ADS)

Chen, Ruoyu

Conduction electrons are responsible for many physical or chemical phenomena in condensed matter systems, and their behavior can be directly studied by electronic transport measurements. In conventional transport measurements, conductance or resistance is usually the focus. Such a measurement can be as simple as a quick two terminal DC check by a multi-meter, or a more sophisticated lock-in measurement of multiple higher harmonic signals synchronized to different frequencies. Conductance carries direct information about the quasi-particle density of states and the local electronic distributions, which are usually Fermi-Dirac distribution. Conductance is modified or dominated by scattering from defacts or interfaces, and could also reflect the spin-spin exchange interactions or inelastic couplings with phonons and photons. Naturally one can ask the question: is there anything else we can measure electronically, which carries extra information that a conductance measurement does not provide? One answer to this question is the electronic noise. While the conductance reflects the average charge conduction ability of a system, noise describes how the physical quantities fluctuate around their average values. Some of the fluctuations carry information about their physical origins. This thesis will focus on one particular type of the electronic noise shot noise, but other types of noise will also be introduced and discussed. We choose to measure the radio frequency component of shot noise, combining with a modulated lock-in detection technique, which provides a method to largely get rid of other unwanted low-frequency noise signals. Au atomic-scale junctions are the systems we studied here. Au is relatively well understood and will not generate too many complications, so it's ideal as the first platform for us to understand both shot noise itself and our RF technique. On the other hand, the atomic scale raises fundamental questions about electronic transport and local energy exchange and dissipation, which make our measurements fundamentally interesting. We employed two different types of mechanical controlled Au break junctions: the Scanning Tunneling Microscope(STM)-style Au break junctions, and the mechanically bending Au break junctions. We studied shot noise behaviors of individual configurations or ensemble averages over all the accessible configurations. Measurements were conducted at both room temperature and liquid He temperature. High quality shot noise measurements were demonstrated. New phenomena like anomalous excess noise enhancement at high bias voltages and non-zero shot noise variance below 1G0 were seen. We also found shot noise to be surprisingly insensitive to temperatures between 4.2K and 100K, and can be well described by the non-interacting approximation.

Quartz Crystal Microbalance Electronic Interfacing Systems: A Review.

PubMed

Alassi, Abdulrahman; Benammar, Mohieddine; Brett, Dan

2017-12-05

Quartz Crystal Microbalance (QCM) sensors are actively being implemented in various fields due to their compatibility with different operating conditions in gaseous/liquid mediums for a wide range of measurements. This trend has been matched by the parallel advancement in tailored electronic interfacing systems for QCM sensors. That is, selecting the appropriate electronic circuit is vital for accurate sensor measurements. Many techniques were developed over time to cover the expanding measurement requirements (e.g., accommodating highly-damping environments). This paper presents a comprehensive review of the various existing QCM electronic interfacing systems. Namely, impedance-based analysis, oscillators (conventional and lock-in based techniques), exponential decay methods and the emerging phase-mass based characterization. The aforementioned methods are discussed in detail and qualitatively compared in terms of their performance for various applications. In addition, some theoretical improvements and recommendations are introduced for adequate systems implementation. Finally, specific design considerations of high-temperature microbalance systems (e.g., GaPO₄ crystals (GCM) and Langasite crystals (LCM)) are introduced, while assessing their overall system performance, stability and quality compared to conventional low-temperature applications.

Quartz Crystal Microbalance Electronic Interfacing Systems: A Review

PubMed Central

Benammar, Mohieddine; Brett, Dan

2017-01-01

Quartz Crystal Microbalance (QCM) sensors are actively being implemented in various fields due to their compatibility with different operating conditions in gaseous/liquid mediums for a wide range of measurements. This trend has been matched by the parallel advancement in tailored electronic interfacing systems for QCM sensors. That is, selecting the appropriate electronic circuit is vital for accurate sensor measurements. Many techniques were developed over time to cover the expanding measurement requirements (e.g., accommodating highly-damping environments). This paper presents a comprehensive review of the various existing QCM electronic interfacing systems. Namely, impedance-based analysis, oscillators (conventional and lock-in based techniques), exponential decay methods and the emerging phase-mass based characterization. The aforementioned methods are discussed in detail and qualitatively compared in terms of their performance for various applications. In addition, some theoretical improvements and recommendations are introduced for adequate systems implementation. Finally, specific design considerations of high-temperature microbalance systems (e.g., GaPO4 crystals (GCM) and Langasite crystals (LCM)) are introduced, while assessing their overall system performance, stability and quality compared to conventional low-temperature applications. PMID:29206212

Ion Thermalization and Electron Heating across Quasi-Perpendicular Shocks Observed by the MMS Mission

NASA Astrophysics Data System (ADS)

Chen, L.-J.; Wilson, L. B., III; Wang, S.; Bessho, N.; Viñas, A. F.-; Lai, H.; Russell, C. T.; Schwartz, S. J.; Hesse, M.; Moore, T. E.; Burch, J. L.; Gershman, D. J.; Giles, B. L.; Torbert, R. B.; Ergun, R. E.; Dorelli, J.; Strangeway, R. J.; Paterson, W. R.; Lavraud, B.; Khotyaintsev, Yu. V.

2017-12-01

Collisionless shocks often involve intense plasma heating in space and astrophysical systems. Despite decades of research, a number of key questions concerning electron and ion heating across collisionless shocks remain unanswered. We 'image' 20 supercritical quasi-perpendicular bow shocks encountered by the Magnetospheric Multiscale (MMS) spacecraft with electron and ion distribution functions to address how ions are thermalized and how electrons are heated. The continuous burst measurements of 3D plasma distribution functions from MMS reveal that the primary thermalization phase of ions occurs concurrently with the main temperature increase of electrons as well as large-amplitude wave fluctuations. Approaching the shock from upstream, the ion temperature (Ti) increases due to the reflected ions joining the incoming solar wind population, as recognized by prior studies, and the increase of Ti precedes that of the electrons. Thermalization in the form of merging between the decelerated solar wind ions and the reflected component often results in a decrease in Ti. In most cases, the Ti decrease is followed by a gradual increase further downstream. Anisotropic, energy-dependent, and/or nongyrotropic electron energization are observed in association with large electric field fluctuations in the main electron temperature (Te) gradient, motivating a renewed scrutiny of the effects from the electrostatic cross-shock potential and wave fluctuations on electron heating. Particle-in-cell (PIC) simulations are carried out to assist interpretations of the MMS observations. We assess the roles of instabilities and the cross-shock potential in thermalizing ions and heating electrons based on the MMS measurements and PIC simulation results. Challenges will be posted for future computational studies and laboratory experiments on collisionless shocks.

Ion Thermalization and Electron Heating across Quasi-Perpendicular Shocks Observed by the MMS Mission

NASA Astrophysics Data System (ADS)

Chen, L. J.; Wilson, L. B., III; Wang, S.; Bessho, N.; Figueroa-Vinas, A.; Lai, H.; Russell, C. T.; Schwartz, S. J.; Hesse, M.; Moore, T. E.; Burch, J.; Gershman, D. J.; Giles, B. L.; Torbert, R. B.; Ergun, R.; Dorelli, J.; Strangeway, R. J.; Paterson, W. R.; Lavraud, B.; Khotyaintsev, Y. V.

2017-12-01

Collisionless shocks often involve intense plasma heating in space and astrophysical systems. Despite decades of research, a number of key questions concerning electron and ion heating across collisionless shocks remain unanswered. We `image' 20 supercritical quasi-perpendicular bow shocks encountered by the Magnetospheric Multiscale (MMS) spacecraft with electron and ion distribution functions to address how ions are thermalized and how electrons are heated. The continuous burst measurements of 3D plasma distribution functions from MMS reveal that the primary thermalization phase of ions occurs concurrently with the main temperature increase of electrons as well as large-amplitude wave fluctuations. Approaching the shock from upstream, the ion temperature (Ti) increases due to the reflected ions joining the incoming solar wind population, as recognized by prior studies, and the increase of Ti precedes that of the electrons. Thermalization in the form of merging between the decelerated solar wind ions and the reflected component often results in a decrease in Ti. In most cases, the Ti decrease is followed by a gradual increase further downstream. Anisotropic, energy-dependent, and/or nongyrotropic electron energization are observed in association with large electric field fluctuations in the main electron temperature (Te) gradient, motivating a renewed scrutiny of the effects from the electrostatic cross-shock potential and wave fluctuations on electron heating. Particle-in-cell (PIC) simulations are carried out to assist interpretations of the MMS observations. We assess the roles of instabilities and the cross-shock potential in thermalizing ions and heating electrons based on the MMS measurements and PIC simulation results. Challenges will be posted for future computational studies and laboratory experiments on collisionless shocks.

Fundamental Experiments at Liquid Helium Temperatures (Low Temperature Studies of Anomalous Surface Shielding and Related Phenomena).

DTIC Science & Technology

1984-09-30

EXPERIMENT BACKGROUND Motivated by the desire to measure for the first time the force of 27 gravity on antimatter , Witteborn and Fairbank (WF...and antimatter . There are, however, no direct experimental tests of the gravitational forces on antimatter . Having measured the force of gravity on...electrons, a measurement using positrons would give the first measurement of the force of gravity on antimatter as well as giving a definitive value for

Ultrafast X-Ray Absorption Spectroscopy of Isochorically Heated Warm Dense Matter

NASA Astrophysics Data System (ADS)

Engelhorn, Kyle Craig

This dissertation will present a series of new tools, together with new techniques, focused on the understanding of warm and dense matter. We report on the development of a high time resolution and high detection efficiency x-ray camera. The camera is integrated with a short pulse laser and an x-ray beamline at the Advanced Light Source synchrotron. This provides an instrument for single shot, broadband x-ray absorption spectroscopy of warm and dense matter with 2 picosecond time resolution. Warm and dense matter is created by isochorically heating samples of known density with an ultrafast optical laser pulse, and X-ray absorption spectroscopy probes the unoccupied electronic density of states before the onset of hydrodynamic expansion and electron-ion equilibrium is reached. Measured spectra from a variety of materials are compared with first principle molecular dynamics and density functional theory calculations. In heated silicon dioxide spectra, two novel pre-edge features are observed, a peak below the band gap and absorption within the band gap, while a reduction was observed in the features above the edge. From consideration of the calculated spectra, the peak below the gap is attributed to valence electrons that have been promoted to the conduction band, the absorption within the gap is attributed to broken Si-O bonds, and the reduction above the edge is attributed to an elevated ionic temperature. In heated copper spectra, a time-dependent shift and broadening of the absorption edge are observed, consistent with and elevated electron temperature. The temporal evolution of the electronic temperature is accurately determined by fitting the measured spectra with calculated spectra. The electron-ion equilibration is studied with a two-temperature model. In heated nickel spectra, a shift of the absorption edge is observed. This shift is found to be inconsistent with calculated spectra and independent of incident laser fluence. A shift of the chemical potential is applied to the calculated spectra to obtain satisfactory agreement with measured spectra.

Temperature Measurements in Compressed and Uncompressed SPECTOR Plasmas at General Fusion

NASA Astrophysics Data System (ADS)

Young, William; Carter, Neil; Howard, Stephen; Carle, Patrick; O'Shea, Peter; Fusion Team, General

2017-10-01

Accurate temperature measurements are critical to establishing the behavior of General Fusion's SPECTOR plasma injector, both before and during compression. As compression tests impose additional constraints on diagnostic access to the plasma, a two-color, filter-based soft x-ray electron temperature diagnostic has been implemented. Ion Doppler spectroscopy measurements also provide impurity ion temperatures on compression tests. The soft x-ray and ion Doppler spectroscopy measurements are being validated against a Thomson scattering system on an uncompressed version of SPECTOR with more diagnostic access. The multipoint Thomson scattering diagnostic also provides up to a six point temperature and density profile, with the density measurements validated against a far infrared interferometer. Temperatures above 300 eV have been demonstrated to be sustained for over 500 microseconds in uncompressed plasmas. Optimization of soft x-ray filters is ongoing, in order to balance blocking of impurity line radiation with signal strength.

Gas temperature measurements in deuterium hollow cathode glow discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majstorović, Gordana, E-mail: gordana.majstorovic@va.mod.gov.rs; Šišović, Nikola, E-mail: nikolas@ff.bg.ac.rs

2016-03-25

We report results of optical emission spectroscopy measurements of rotational T{sub rot} and translational (gas) temperature of deuterium molecules in a hollow cathode (HC) glow discharge. The rotational temperature of excited electronic state of D{sub 2} was determined from the intensity distribution in the rotational structure of Q branch of the two Fulcher-α diagonal bands: (ν’=ν”=2) and (ν’=ν”=3). The population of excited energy levels, determined from relative line intensities, was used to derive radial rotational temperature distributions as well as gas temperature distribution of deuterium molecule.

Profile measurements in the plasma edge of mega amp spherical tokamak using a ball pen probe

NASA Astrophysics Data System (ADS)

Walkden, N. R.; Adamek, J.; Allan, S.; Dudson, B. D.; Elmore, S.; Fishpool, G.; Harrison, J.; Kirk, A.; Komm, M.

2015-02-01

The ball pen probe (BPP) technique is used successfully to make profile measurements of plasma potential, electron temperature, and radial electric field on the Mega Amp Spherical Tokamak. The potential profile measured by the BPP is shown to significantly differ from the floating potential both in polarity and profile shape. By combining the BPP potential and the floating potential, the electron temperature can be measured, which is compared with the Thomson scattering (TS) diagnostic. Excellent agreement between the two diagnostics is obtained when secondary electron emission is accounted for in the floating potential. From the BPP profile, an estimate of the radial electric field is extracted which is shown to be of the order ˜1 kV/m and increases with plasma current. Corrections to the BPP measurement, constrained by the TS comparison, introduce uncertainty into the ER measurements. The uncertainty is most significant in the electric field well inside the separatrix. The electric field is used to estimate toroidal and poloidal rotation velocities from E × B motion. This paper further demonstrates the ability of the ball pen probe to make valuable and important measurements in the boundary plasma of a tokamak.

Electronic Tongue Containing Redox and Conductivity Sensors

NASA Technical Reports Server (NTRS)

Buehler, Martin

2007-01-01

The Electronic Tongue (E-tongue 2) is an assembly of sensors for measuring concentrations of metal ions and possibly other contaminants in water. Potential uses for electronic tongues include monitoring the chemical quality of water in a variety of natural, industrial, and laboratory settings, and detecting micro-organisms indirectly by measuring microbially influenced corrosion. The device includes a heater, a temperature sensor, an oxidation/reduction (redox) sensor pair, an electrical sensor, an array of eight galvanic cells, and eight ion-specific electrodes.

Disordered crystals from first principles I: Quantifying the configuration space

NASA Astrophysics Data System (ADS)

Kühne, Thomas D.; Prodan, Emil

2018-04-01

This work represents the first chapter of a project on the foundations of first-principle calculations of the electron transport in crystals at finite temperatures. We are interested in the range of temperatures, where most electronic components operate, that is, room temperature and above. The aim is a predictive first-principle formalism that combines ab-initio molecular dynamics and a finite-temperature Kubo-formula for homogeneous thermodynamic phases. The input for this formula is the ergodic dynamical system (Ω , G , dP) defining the thermodynamic crystalline phase, where Ω is the configuration space for the atomic degrees of freedom, G is the space group acting on Ω and dP is the ergodic Gibbs measure relative to the G-action. The present work develops an algorithmic method for quantifying (Ω , G , dP) from first principles. Using the silicon crystal as a working example, we find the Gibbs measure to be extremely well characterized by a multivariate normal distribution, which can be quantified using a small number of parameters. The latter are computed at various temperatures and communicated in the form of a table. Using this table, one can generate large and accurate thermally-disordered atomic configurations to serve, for example, as input for subsequent simulations of the electronic degrees of freedom.

Breathable and Stretchable Temperature Sensors Inspired by Skin

NASA Astrophysics Data System (ADS)

Chen, Ying; Lu, Bingwei; Chen, Yihao; Feng, Xue

2015-06-01

Flexible electronics attached to skin for healthcare, such as epidermal electronics, has to struggle with biocompatibility and adapt to specified environment of skin with respect to breath and perspiration. Here, we report a strategy for biocompatible flexible temperature sensors, inspired by skin, possessing the excellent permeability of air and high quality of water-proof by using semipermeable film with porous structures as substrate. We attach such temperature sensors to underarm and forearm to measure the axillary temperature and body surface temperature respectively. The volunteer wears such sensors for 24 hours with two times of shower and the in vitro test shows no sign of maceration or stimulation to the skin. Especially, precise temperature changes on skin surface caused by flowing air and water dropping are also measured to validate the accuracy and dynamical response. The results show that the biocompatible temperature sensor is soft and breathable on the human skin and has the excellent accuracy compared to mercury thermometer. This demonstrates the possibility and feasibility of fully using the sensors in long term body temperature sensing for medical use as well as sensing function of artificial skin for robots or prosthesis.

Breathable and Stretchable Temperature Sensors Inspired by Skin

PubMed Central

Chen, Ying; Lu, Bingwei; Chen, Yihao; Feng, Xue

2015-01-01

Flexible electronics attached to skin for healthcare, such as epidermal electronics, has to struggle with biocompatibility and adapt to specified environment of skin with respect to breath and perspiration. Here, we report a strategy for biocompatible flexible temperature sensors, inspired by skin, possessing the excellent permeability of air and high quality of water-proof by using semipermeable film with porous structures as substrate. We attach such temperature sensors to underarm and forearm to measure the axillary temperature and body surface temperature respectively. The volunteer wears such sensors for 24 hours with two times of shower and the in vitro test shows no sign of maceration or stimulation to the skin. Especially, precise temperature changes on skin surface caused by flowing air and water dropping are also measured to validate the accuracy and dynamical response. The results show that the biocompatible temperature sensor is soft and breathable on the human skin and has the excellent accuracy compared to mercury thermometer. This demonstrates the possibility and feasibility of fully using the sensors in long term body temperature sensing for medical use as well as sensing function of artificial skin for robots or prosthesis. PMID:26095941

Electrical transport, electrothermal transport, and effective electron mass in single-crystalline In2O3 films

NASA Astrophysics Data System (ADS)

Preissler, Natalie; Bierwagen, Oliver; Ramu, Ashok T.; Speck, James S.

2013-08-01

A comprehensive study of the room-temperature electrical and electrothermal transport of single-crystalline indium oxide (In2O3) and indium tin oxide (ITO) films over a wide range of electron concentrations is reported. We measured the room-temperature Hall mobility μH and Seebeck coefficient S of unintentionally doped and Sn-doped high-quality, plasma-assisted molecular-beam-epitaxy-grown In2O3 for volume Hall electron concentrations nH from 7×1016 cm-3 (unintentionally doped) to 1×1021 cm-3 (highly Sn-doped, ITO). The resulting empirical S(nH) relation can be directly used in other In2O3 samples to estimate the volume electron concentration from simple Seebeck coefficient measurements. The mobility and Seebeck coefficient were modeled by a numerical solution of the Boltzmann transport equation. Ionized impurity scattering and polar optical phonon scattering were found to be the dominant scattering mechanisms. Acoustic phonon scattering was found to be negligible. Fitting the temperature-dependent mobility above room temperature of an In2O3 film with high mobility allowed us to find the effective Debye temperature (ΘD=700 K) and number of phonon modes (NOPML=1.33) that best describe the polar optical phonon scattering. The modeling also yielded the Hall scattering factor rH as a function of electron concentration, which is not negligible (rH≈1.4) at nondegenerate electron concentrations. Fitting the Hall-scattering-factor corrected concentration-dependent Seebeck coefficient S(n) for nondegenerate samples to the numerical solution of the Boltzmann transport equation and to widely used, simplified equations allowed us to extract an effective electron mass of m*=(0.30±0.03)me (with free electron mass me). The modeled mobility and Seebeck coefficient based on polar optical phonon and ionized impurity scattering describes the experimental results very accurately up to electron concentrations of 1019 cm-3, and qualitatively explains a mobility plateau or local maximum around 1020 cm-3. Ionized impurity scattering with doubly charged donors best describes the mobility in our unintentionally doped films, consistent with oxygen vacancies as unintentional shallow donors, whereas singly charged donors best describe our Sn-doped films. Our modeling yields a (phonon-limited) maximum theoretical drift mobility and Hall mobility of μ=190 cm2/Vs and μH=270 cm2/Vs, respectively. Simplified equations for the Seebeck coefficient describe the measured values in the nondegenerate regime using a Seebeck scattering parameter of r=-0.55 (which is consistent with the determined Debye temperature), and provide an estimate of the Seebeck coefficient to lower electron concentrations. The simplified equations fail to describe the Seebeck coefficient around the Mott transition (nMott=5.5×1018 cm-3) from nondegenerate to degenerate electron concentrations, whereas the numerical modeling accurately describes this region.

Rocket-borne thermal plasma instrument "MIPEX" for the ionosphere D, E layer in-situ measurements

NASA Astrophysics Data System (ADS)

Fang, H. K.; Chen, A. B. C.; Lin, C. C. H.; Wu, T. J.; Liu, K. S.; Chuang, C. W.

2017-12-01

In this presentation, the design concepts, performances and status of a thermal plasma particle instrument package "Mesosphere and Ionosphere Plasma Exploration complex (MIPEX)", which is going to be installed onboard a NSPO-funded hybrid rocket, to investigate the electrodynamic processes in ionosphere D, E layers above Taiwan are reported. MIPEX is capable of measuring plasma characteristics including ion temperature, ion composition, ion drift, electron temperature and plasma density at densities as low as 1-10 cm-1. This instrument package consists of an improved retarding potential analyzer with a channel electron multiplier (CEM), a simplified ion drift meter and a planar Langmuir probe. To achieve the working atmospheric pressure of CEM at the height of lower D layer ( 70km), a portable vacuum pump is also placed in the package. A prototype set of the MIPEX has been developed and tested in the Space Plasma Operation Chamber (SPOC) at NCKU, where in ionospheric plasma is generated by back-diffusion plasma sources. A plasma density of 10-106 cm-1, ion temperature of 300-1500 K and electron temperature of 1000-3000K is measured and verified. Limited by the flight platform and the performance of the instruments, the in-situ plasma measurements at the Mesosphere and lower Thermosphere is very challenging and rare. MIPEX is capable of extending the altitude of the effective plasma measurement down to 70 km height and this experiment can provide unique high-quality data of the plasma environment to explore the ion distribution and the electrodynamic processes in the Ionosphere D, E layers at dusk.

The role of fiberoptics in remote temperature measurement

NASA Technical Reports Server (NTRS)

Vanzetti, Riccardo

1988-01-01

The use of optical fibers in conjunction with infrared detectors and signal processing electronics represents the latest advance in the field of non-contact temperature measurement and control. The operating principles and design of fiber-optic radiometric systems are discussed and the advantages and disadvantages of using optical fibers are addressed. Signal processing requirements and various infrared detector types are also described. Several areas in which infrared fiber-optic instrumentation is used for temperature monitoring and control are discussed.

Fluctuation-exchange study of antiferromagnetism in disordered electron-doped cuprate superconductors.

PubMed

Yan, Xin-Zhong; Ting, C S

2006-08-11

On the basis of the Hubbard model, we extend the fluctuation-exchange (FLEX) approach to investigating the properties of the antiferromagnetic (AF) phase in electron-doped cuprate superconductors. Furthermore, by incorporating the effect of scatterings due to the disordered dopant atoms into the FLEX formalism, our numerical results show that the antiferromagnetic transition temperature, the onset temperature of pseudogap due to spin fluctuations, the spectral density of the single particle near the Fermi surface, and the staggered magnetization in the AF phase as a function of electron doping can consistently account for the experimental measurements.

Ultrafast hopping dynamics of 5f electrons in the Mott insulator UO₂ studied by femtosecond pump-probe spectroscopy.

PubMed

An, Yong Q; Taylor, Antoinette J; Conradson, Steven D; Trugman, Stuart A; Durakiewicz, Tomasz; Rodriguez, George

2011-05-20

We describe a femtosecond pump-probe study of ultrafast hopping dynamics of 5f electrons in the Mott insulator UO₂ following Mott-gap excitation at temperatures of 5-300 K. Hopping-induced response of the lattice and electrons is probed by transient reflectivity at mid- and above-gap photon energies, respectively. These measurements show an instantaneous hop, subsequent picosecond lattice deformation, followed by acoustic phonon emission and microsecond relaxation. Temperature-dependent studies indicate that the slow relaxation results from Hubbard excitons formed by U³⁺-U⁵⁺ pairs.

A Harsh Environment Wireless Pressure Sensing Solution Utilizing High Temperature Electronics

PubMed Central

Yang, Jie

2013-01-01

Pressure measurement under harsh environments, especially at high temperatures, is of great interest to many industries. The applicability of current pressure sensing technologies in extreme environments is limited by the embedded electronics which cannot survive beyond 300 °C ambient temperature as of today. In this paper, a pressure signal processing and wireless transmission module based on the cutting-edge Silicon Carbide (SiC) devices is designed and developed, for a commercial piezoresistive MEMS pressure sensor from Kulite Semiconductor Products, Inc. Equipped with this advanced high-temperature SiC electronics, not only the sensor head, but the entire pressure sensor suite is capable of operating at 450 °C. The addition of wireless functionality also makes the pressure sensor more flexible in harsh environments by eliminating the costly and fragile cable connections. The proposed approach was verified through prototype fabrication and high temperature bench testing from room temperature up to 450 °C. This novel high-temperature pressure sensing technology can be applied in real-time health monitoring of many systems involving harsh environments, such as military and commercial turbine engines. PMID:23447006

A harsh environment wireless pressure sensing solution utilizing high temperature electronics.

PubMed

Yang, Jie

2013-02-27

Pressure measurement under harsh environments, especially at high temperatures, is of great interest to many industries. The applicability of current pressure sensing technologies in extreme environments is limited by the embedded electronics which cannot survive beyond 300 °C ambient temperature as of today. In this paper, a pressure signal processing and wireless transmission module based on the cutting-edge Silicon Carbide (SiC) devices is designed and developed, for a commercial piezoresistive MEMS pressure sensor from Kulite Semiconductor Products, Inc. Equipped with this advanced high-temperature SiC electronics, not only the sensor head, but the entire pressure sensor suite is capable of operating at 450 °C. The addition of wireless functionality also makes the pressure sensor more flexible in harsh environments by eliminating the costly and fragile cable connections. The proposed approach was verified through prototype fabrication and high temperature bench testing from room temperature up to 450 °C. This novel high-temperature pressure sensing technology can be applied in real-time health monitoring of many systems involving harsh environments, such as military and commercial turbine engines.

Containerless high temperature property measurements by atomic fluorescence

NASA Technical Reports Server (NTRS)

Schiffman, R. A.; Walker, C. A.

1984-01-01

Laser induced fluorescence (LIF) techniques for containerless study of high temperature processes and material properties was studied. Gas jet and electromagnetic levitation and electromagnetic and laser heating techniques are used with LIF in earth-based containerless high temperature experiments. Included are the development of an apparatus and its use in the studies of (1) chemical reactions on Al2O3, molybdenum, tungsten and LaB6 specimens, (2) methods for noncontact specimen temperature measurement, (3) levitation jet properties and (4) radiative lifetime and collisional energy transfer rates for electronically excited atoms.

Positron Annihilation Measurements of High Temperature Superconductors

NASA Astrophysics Data System (ADS)

Jung, Kang

1995-01-01

The temperature dependence of positron annihilation parameters has been measured for basic YBCO, Dy-doped, and Pr-doped superconducting compounds. The physical properties, such as crystal structure, electrical resistance, and critical temperature, have been studied for all samples. In the basic YBCO and Dy-doped samples, the defect -related lifetime component tau_{2 } was approximately constant from room temperature to above the critical temperature and then showed a step -like decrease in the temperature range 90K { ~} 40K. No significant temperature dependence was found in the short- and long-lifetime components, tau_{1} and tau_{3}. The x-ray diffraction data showed that the crystal structure of these two samples was almost the same. These results indicated that the electronic structure changed below the critical temperature. No transition was observed in the Pr-doped YBCO sample. The advanced computer program "PFPOSFIT" for positron lifetime analysis was modified to run on the UNIX system of the University of Utah. The destruction of superconductivity with Pr doping may be due to mechanisms such as hole filling or hole localization of the charge carriers and may be related to the valence state of the Pr ion. One-parameter analyses like the positron mean lifetime parameter and the Doppler line shape parameter S also have been studied. It was found that a transition in Doppler line shape parameter S was associated with the superconducting transition temperature in basic YBCO, Dy -doped, and 0.5 Pr-doped samples, whereas no transition was observed in the nonsuperconducting Pr-doped sample. The Doppler results indicate that the average electron momentum at the annihilation sites increases as temperature is lowered across the superconducting transition range and that electronic structure change plays an important role in high temperature superconductivity.

Langmuir probe diagnostics of an atmospheric pressure, vortex-stabilized nitrogen plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prevosto, L.; Mancinelli, B. R.; Kelly, H.

Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non-transferred arc torch with a rod-type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min{sup -1}. A flat ion saturation region was found in the current-voltage curve of the probe. The ion saturation current to a cylindrical probe in a high-pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processesmore » inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 Multiplication-Sign 10{sup 22} m{sup -3}, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying-type plasma jets characterized by electron temperatures in the range 9000-14 000 K.« less

Electron-temperature dependence of dissociative recombination of electrons with CO/+/./CO/n-series ions

NASA Technical Reports Server (NTRS)

Whitaker, M.; Biondi, M. A.; Johnsen, R.

1981-01-01

The dependence on electron temperature of the coefficients for electron recombination with molecular cluster ions of the carbon monoxide series, CO(+).(CO)n, is determined. A microwave discharge lasting approximately 0.1 msec was applied in 5-20 Torr neon containing a few tenths percent CO in an afterglow mass spectrometer apparatus, and the time histories of the various afterglow ions were measured. Expressions for the dependence of the recombination coefficients of the dimer and trimer ions CO(+).CO and CO(+).(CO)2 are obtained which are found to be significantly different from those previously obtained for hydronium and ammonium series polar cluster ions, but similar to those of simple diatomic ions.

Statistics of excitations in the electron glass model

NASA Astrophysics Data System (ADS)

Palassini, Matteo

2011-03-01

We study the statistics of elementary excitations in the classical electron glass model of localized electrons interacting via the unscreened Coulomb interaction in the presence of disorder. We reconsider the long-standing puzzle of the exponential suppression of the single-particle density of states near the Fermi level, by measuring accurately the density of states of charged and electron-hole pair excitations via finite temperature Monte Carlo simulation and zero-temperature relaxation. We also investigate the statistics of large charge rearrangements after a perturbation of the system, which may shed some light on the slow relaxation and glassy phenomena recently observed in a variety of Anderson insulators. In collaboration with Martin Goethe.

Observations of reduced electron Gyroscale fluctuations in national spherical torus experiment H-mode plasmas with large ExB flow shear.

PubMed

Smith, D R; Kaye, S M; Lee, W; Mazzucato, E; Park, H K; Bell, R E; Domier, C W; Leblanc, B P; Levinton, F M; Luhmann, N C; Menard, J E; Yuh, H

2009-06-05

Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in National Spherical Torus Experiment plasmas with neutral beam injection generates ExB flow shear rates comparable to ETG linear growth rates. Enhanced fluctuations occur when the electron temperature gradient is marginally stable with respect to the ETG linear critical gradient. Fluctuation amplitudes decrease when the ExB flow shear rate exceeds ETG linear growth rates. The observations indicate that ExB flow shear can be an effective suppression mechanism for ETG turbulence.

Theoretical and Experimental Beam Plasma Physics (TEBPP)

NASA Technical Reports Server (NTRS)

Roberts, W. T.

1985-01-01

The theoretical and experimental beam plasma physics (TEBPP) consists of a package of five instruments to measure electric and magnetic fields, plasma density and temperature, neutral density, photometric emissions, and energetic particle spectra during firings of the particle injector (SEPAC) electron beam. The package is deployed on a maneuverable boom (or RMS) and is used to measure beam characteristics and induced perturbations in the near field ( 10 m) and mid field (10 m to 100 m) along the electron beam. The TEBPP package will be designed to investigate induced oscillations and induced electromagnetic mode waves, neutral and ion density and temperature effects, and beam characteristics as a function of axial distance.

Theoretical and Experimental Beam Plasma Physics (TEBPP)

NASA Technical Reports Server (NTRS)

Roberts, B.

1986-01-01

The theoretical and experimental beam plasma physics (TEBPP) consists of a package of five instruments to measure electric and magnetic fields, plasma density and temperature, neutral density, photometric emissions, and energetic particle spectra during firings of the particle injector (SEPAC) electron beam. The package is developed on a maneuverable boom (or RMS) and is used to measure beam characteristics and induced perturbations field ( 10 m) and mid field ( 10 m to 100 m) along the electron beam. The TEBPP package will be designed to investigate induced oscillations and induced electromagnetic mode waves, neutral and ion density and temperature effects, and beam characteristics as a function of axial distance.

In-place recalibration technique applied to a capacitance-type system for measuring rotor blade tip clearance

NASA Technical Reports Server (NTRS)

Barranger, J. P.

1978-01-01

The rotor blade tip clearance measurement system consists of a capacitance sensing probe with self contained tuning elements, a connecting coaxial cable, and remotely located electronics. Tests show that the accuracy of the system suffers from a strong dependence on probe tip temperature and humidity. A novel inplace recalibration technique was presented which partly overcomes this problem through a simple modification of the electronics that permits a scale factor correction. This technique, when applied to a commercial system significantly reduced errors under varying conditions of humidity and temperature. Equations were also found that characterize the important cable and probe design quantities.

Qualification and implementation of line ratio spectroscopy on helium as plasma edge diagnostic at ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Griener, M.; Muñoz Burgos, J. M.; Cavedon, M.; Birkenmeier, G.; Dux, R.; Kurzan, B.; Schmitz, O.; Sieglin, B.; Stroth, U.; Viezzer, E.; Wolfrum, E.; the ASDEX Upgrade Team

2018-02-01

A new thermal helium beam diagnostic has been implemented as plasma edge diagnostic at the ASDEX Upgrade (AUG) tokamak. The helium beam is built to measure the electron density n e and temperature T e simultaneously with high spatial and temporal resolution in order to investigate steady-state as well as fast transport processes in the plasma edge region. For the thermal helium beam emission line ratio spectroscopy, neutral helium is locally injected into the plasma by a piezo valve. This enabled the measurement of the line resolved emission intensities of seven He I lines for different plasma scenarios in AUG. The different line ratios can be used together with a collisional-radiative model (CRM) to reconstruct the underlying electron temperature and density. Ratios from the same spin species are used for the electron density reconstruction, whereas spin mixed ratios are sensitive to electron temperature changes. The different line ratios as well as different CRMs are tested for their suitability for diagnostic applications. Furthermore their consistency in calculating identical parameters is validated and the resulting profiles are compared to other available diagnostics at AUG.

Electrical characterization of HgTe nanowires using conductive atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gundersen, P.; Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim; Kongshaug, K. O.

Self-organized HgTe nanowires grown by molecular beam epitaxy (MBE) have been characterized using conductive atomic force microscopy. As HgTe will degrade or evaporate at normal baking temperatures for electron beam lithography (EBL) resists, an alternative method was developed. Using low temperature optical lithography processes, large Au contacts were deposited on a sample covered with randomly oriented, lateral HgTe nanowires. Nanowires partly covered by the large electrodes were identified with a scanning electron microscope and then localized in the atomic force microscope (AFM). The conductive tip of the AFM was then used as a movable electrode to measure current-voltage curves atmore » several locations on HgTe nanowires. The measurements revealed that polycrystalline nanowires had diffusive electron transport, with resistivities two orders of magnitude larger than that of an MBE-grown HgTe film. The difference can be explained by scattering at the rough surface walls and at the grain boundaries in the wires. The method can be a solution when EBL is not available or requires too high temperature, or when measurements at several positions along a wire are required.« less

Empirical models of the electron temperature and density in the nightside venus ionosphere.

PubMed

Brace, L H; Theis, R F; Niemann, H B; Mayr, H G; Hoegy, W R; Nagy, A F

1979-07-06

Empirical models of the electron temperature and electron density of the late afternoon and nightside Venus ionosphere have been derived from Pioneer Venus measurements acquired between 10 December 1978 and 23 March 1979. The models describe the average ionosphere conditions near 18 degrees N latitude between 150 and 700 kilometers altitude for solar zenith angles of 80 degrees to 180 degrees . The average index of solar flux was 200. A major feature of the density model is the factor of 10 decrease beyond 90 degrees followed by a very gradual decrease between 120 degrees and 180 degrees . The density at 150 degrees is about five times greater than observed by Venera 9 and 10 at solar minimum (solar flux approximately 80), a difference that is probably related to the effects of increased solar activity on the processes that maintain the nightside ionosphere. The nightside electron density profile from the model (above 150 kilometers) can be reproduced theoretically either by transport of 0(+) ions from the dayside or by precipitation of low-energy electrons. The ion transport process would require a horizontal flow velocity of about 300 meters per second, a value that is consistent with other Pioneer Venus observations. Although currently available energetic electron data do not yet permit the role of precipitation to be evaluated quantitatively, this process is clearly involved to some extent in the formation of the nightside ionosphere. Perhaps the most surprising feature of the temperature model is that the electron temperature remains high throughout the nightside ionosphere. These high nocturnal temperatures and the existence of a well-defined nightside ionopause suggest that energetic processes occur across the top of the entire nightside ionosphere, maintaining elevated temperatures. A heat flux of 2 x 10(10) electron volts per square centimeter per second, introduced at the ionopause, is consistent with the average electron temperature profile on the nightside at a solar zenith angle of 140 degrees .

Self-Correcting Electronically-Scanned Pressure Sensor

NASA Technical Reports Server (NTRS)

Gross, C.; Basta, T.

1982-01-01

High-data-rate sensor automatically corrects for temperature variations. Multichannel, self-correcting pressure sensor can be used in wind tunnels, aircraft, process controllers and automobiles. Offers data rates approaching 100,000 measurements per second with inaccuracies due to temperature shifts held below 0.25 percent (nominal) of full scale over a temperature span of 55 degrees C.

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

NASA Astrophysics Data System (ADS)

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.

Carrier multiplication and charge transport in artificial quantum-dot solids probed by ultrafast photocurrent spectroscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Klimov, Victor I.

2017-05-01

Understanding and controlling carrier transport and recombination dynamics in colloidal quantum dot films is key to their application in electronic and optoelectronic devices. Towards this end, we have conducted transient photocurrent measurements to monitor transport through quantum confined band edge states in lead selenide quantum dots films as a function of pump fluence, temperature, electrical bias, and surface treatment. Room temperature dynamics reveal two distinct timescales of intra-dot geminate processes followed by non-geminate inter-dot processes. The non-geminate kinetics is well described by the recombination of holes with photoinjected and pre-existing electrons residing in mid-gap states. We find the mobility of the quantum-confined states shows no temperature dependence down to 6 K, indicating a tunneling mechanism of early time photoconductance. We present evidence of the importance of the exciton fine structure in controlling the low temperature photoconductance, whereby the nanoscale enhanced exchange interaction between electrons and holes in quantum dots introduces a barrier to charge separation. Finally, side-by-side comparison of photocurrent transients using excitation with low- and high-photon energies (1.5 vs. 3.0 eV) reveals clear signatures of carrier multiplication (CM), that is, generation of multiple excitons by single photons. Based on photocurrent measurements of quantum dot solids and optical measurements of solution based samples, we conclude that the CM efficiency is unaffected by strong inter-dot coupling. Therefore, the results of previous numerous spectroscopic CM studies conducted on dilute quantum dot suspensions should, in principle, be reproducible in electronically coupled QD films used in devices.

Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature

NASA Astrophysics Data System (ADS)

Willa, K.; Diao, Z.; Campanini, D.; Welp, U.; Divan, R.; Hudl, M.; Islam, Z.; Kwok, W.-K.; Rydh, A.

2017-12-01

Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification of beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-δ crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.

Low energy electron beam processing of YBCO thin films

NASA Astrophysics Data System (ADS)

Chromik, Š.; Camerlingo, C.; Sojková, M.; Štrbík, V.; Talacko, M.; Malka, I.; Bar, I.; Bareli, G.; Jung, G.

2017-02-01

Effects of low energy 30 keV electron irradiation of superconducting YBa2Cu3O7-δ thin films have been investigated by means of transport and micro-Raman spectroscopy measurements. The critical temperature and the critical current of 200 nm thick films initially increase with increasing fluency of the electron irradiation, reach the maximum at fluency 3 - 4 × 1020 electrons/cm2, and then decrease with further fluency increase. In much thinner films (75 nm), the critical temperature increases while the critical current decreases after low energy electron irradiation with fluencies below 1020 electrons/cm2. The Raman investigations suggest that critical temperature increase in irradiated films is due to healing of broken Cusbnd O chains that results in increased carrier's concentration in superconducting CuO2 planes. Changes in the critical current are controlled by changes in the density of oxygen vacancies acting as effective pinning centers for flux vortices. The effects of low energy electron irradiation of YBCO turned out to result from a subtle balance of many processes involving oxygen removal, both by thermal activation and kick-off processes, and ordering of chains environment by incident electrons.

Observation of inhibited electron-ion coupling in strongly heated graphite

PubMed Central

White, T. G.; Vorberger, J.; Brown, C. R. D.; Crowley, B. J. B.; Davis, P.; Glenzer, S. H.; Harris, J. W. O.; Hochhaus, D. C.; Le Pape, S.; Ma, T.; Murphy, C. D.; Neumayer, P.; Pattison, L. K.; Richardson, S.; Gericke, D. O.; Gregori, G.

2012-01-01

Creating non-equilibrium states of matter with highly unequal electron and lattice temperatures (Tele≠Tion) allows unsurpassed insight into the dynamic coupling between electrons and ions through time-resolved energy relaxation measurements. Recent studies on low-temperature laser-heated graphite suggest a complex energy exchange when compared to other materials. To avoid problems related to surface preparation, crystal quality and poor understanding of the energy deposition and transport mechanisms, we apply a different energy deposition mechanism, via laser-accelerated protons, to isochorically and non-radiatively heat macroscopic graphite samples up to temperatures close to the melting threshold. Using time-resolved x ray diffraction, we show clear evidence of a very small electron-ion energy transfer, yielding approximately three times longer relaxation times than previously reported. This is indicative of the existence of an energy transfer bottleneck in non-equilibrium warm dense matter. PMID:23189238

Effect of molecular desorption on the electronic properties of self-assembled polarizable molecular monolayers.

PubMed

Wang, Gunuk; Jeong, Hyunhak; Ku, Jamin; Na, Seok-In; Kang, Hungu; Ito, Eisuke; Jang, Yun Hee; Noh, Jaegeun; Lee, Takhee

2014-04-01

We investigated the interfacial electronic properties of self-assembled monolayers (SAM)-modified Au metal surface at elevated temperatures. We observed that the work functions of the Au metal surfaces modified with SAMs changed differently under elevated-temperature conditions based on the type of SAMs categorized by three different features based on chemical anchoring group, molecular backbone structure, and the direction of the dipole moment. The temperature-dependent work function of the SAM-modified Au metal could be explained in terms of the molecular binding energy and the thermal stability of the SAMs, which were investigated with thermal desorption spectroscopic measurements and were explained with molecular modeling. Our study will aid in understanding the electronic properties at the interface between SAMs and metals in organic electronic devices if an annealing treatment is applied. Copyright © 2013 Elsevier Inc. All rights reserved.

A 2.5-2.7 THz Room Temperature Electronic Source

NASA Technical Reports Server (NTRS)

Maestrini, Alain; Mehdi, Imran; Lin, Robert; Siles, Jose Vicente; Lee, Choonsup; Gill, John; Chattopadhyay, Goutam; Schlecht, Erich; Bertrand, Thomas; Ward, John

2011-01-01

We report on a room temperature 2.5 to 2.7 THz electronic source based on frequency multipliers. The source utilizes a cascade of three frequency multipliers with W-band power amplifiers driving the first stage multiplier. Multiple-chip multipliers are utilized for the two initial stages to improve the power handling capability and a sub-micron anode is utilized for the final stage tripler. Room temperature measurements indicate that the source can put out a peak power of about 14 microwatts with more than 4 microwatts in the 2.5 to 2.7 THz range.

Columnar recombination for X-ray generated electron-holes in amorphous selenium and its significance in a-Se x-ray detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bubon, O.; Thunder Bay Regional Research Institute, Thunder Bay, Ontario, P7A 7T1; Jandieri, K.

Although amorphous selenium (a-Se) has a long and successful history of application in optical and X-ray imaging, some of its fundamental properties are still puzzling. In particularly, the mechanism of carrier recombination following x-ray excitation and electric field and temperature dependences of the electron-hole pair creation energy (W{sub ehp}) remain unclear. Using the combination of X-ray photocurrent and pulse height spectroscopy measurements, we measure W{sub ehp} in a wide range of temperatures (218–320 K) and electric fields (10–100 V/µm) and show that the conventional columnar recombination model which assumes Langevin recombination within a column (a primary electron track) fails to explain experimentalmore » results in a wide range of electric fields and temperatures. The reason for the failure of the conventional model is revealed in this work, and the theory of the columnar recombination is modified to include the saturation of the recombination rate at high electric field in order to account for the experimental results in the entire range of fields and temperatures.« less

Structural, transport and magnetotransport properties of Ru-doped La0.5Sr0.5Mn1-xRuxO3 (x = 0.0 & 0.05) manganite

NASA Astrophysics Data System (ADS)

Jethva, Sadaf; Katba, Savan; Udeshi, Malay; Kuberkar, D. G.

2017-09-01

We report the results of the structural, transport and magnetotransport studies on polycrystalline La0.5Sr0.5Mn1-xRuxO3 (x = 0.0 and 0.05) manganite investigated using XRD and resistivity (with and without field) measurements. Rietveld refinement of XRD patterns confirms the single phasic tetragonal structure for both the samples crystalizing in I4/mcm space group (No. 140). Low-temperature resistivity and MR measurements with H = 0 T & 5 T field show thermal hysteresis which has been attributed to the first order phase transition. The increase in resistivity and decrease in metal - insulator transition temperature (TMI) with Ru - doping concentration in La0.5Sr0.5MnO3 (LSMO) has been understood in the context of superexchange interaction between Mn and Ru ions. The observed upturn in resistivity at low temperature under field has been explained using combined effect of electron - electron (e - e) interaction, Kondo-like spin-dependent scattering and electron - phonon interaction while the variation in resistivity at high temperature (T > Tp) has been explained using adiabatic small polaron hopping model.

Analysis of the coupled electron-ripplon oscillations resonance spectra in the Wigner solid at different temperatures and modeling of the excitation process

NASA Astrophysics Data System (ADS)

Syvokon, V. E.; Sharapova, I. V.

2018-05-01

The spectrum of coupled electron-ripplon oscillations in a Wigner crystal on the surface of superfluid helium at various temperatures and excitation voltages, leading to spectrum distortion, was studied experimentally. It was shown that at all temperatures, increasing excitation voltage leads to the appearance of non-axisymmetric vibrational modes, which indicates distortions of the crystal lattice. The possibility of excitation of the non-axisymmetric modes in a cell was demonstrated by modeling electronic crystal oscillations using the molecular dynamics method. At several fixed frequencies, the amplitudes of the response of the electronic crystal to external excitation were measured as a function of the magnitude of excitation voltage, and jumps were detected at certain critical voltages. Using the Lindemann criterion, a correlation was found between the critical stress and stability limit of the crystal lattice. It was concluded that when the critical voltage is reached, dynamic melting of the electronic crystal occurs.