Lower hybrid heating experiment in JFT-2 tokamak

International Nuclear Information System (INIS)

Uchara, K.; Nagashima, T.

1982-01-01

Lower hybrid heating experiments in JFT-2 are reviewed. Good maintenance and controlling of the coupling structure are very important in the injection of RF power before heating experiments. Accessibility of waves and the existence of the mode conversion region are necessary for ion heating in the main plasma. Parametric instabilities which may bring undesirable power deposition are suppressed by enough electron heating in the boundary region. Optimizing the Nsub(z) spectrum and the improvement of the plasma confinement may lead the electron heating in the high density region. Current generation by use of quasi-linear Landau damping is confirmed and is suggested to bring the improvement of plasma confinement. High power and long pulse klystrons may be expected to open a frontier toward a stational reactor plasma in tokamaks. (author)

High Energy Antimatter Telescope (HEAT) Balloon Experiment

Science.gov (United States)

Beatty, J. J.

1995-01-01

This grant supported our work on the High Energy Antimatter Telescope(HEAT) balloon experiment. The HEAT payload is designed to perform a series of experiments focusing on the cosmic ray positron, electron, and antiprotons. Thus far two flights of the HEAT -e+/- configuration have taken place. During the period of this grant major accomplishments included the following: (1) Publication of the first results of the 1994 HEAT-e+/- flight in Physical Review Letters; (2) Successful reflight of the HEAT-e+/- payload from Lynn Lake in August 1995; (3) Repair and refurbishment of the elements of the HEAT payload damaged during the landing following the 1995 flight; and (4) Upgrade of the ground support equipment for future flights of the HEAT payload.

Electron heating in JET by ICRH

International Nuclear Information System (INIS)

Cordey, J.G.; Christiansen, J.P.; Core, W.G.F.; Cotrell, G.A.; Eriksson, L.G.; Kovanen, M.A.; Lomas, P.; Start, D.F.H.; Taroni, A.; Tibone, F.

1991-01-01

Several ICRH experiments carried out on JET during the period 1988-90 have been directed specifically at raising the electron temperature to a high value by maximizing the total input power per particle (P tot /n). It has been found that the electron temperature saturates around 12-14 keV in sharp contrast to NBI ion heating experiments in which ion temperatures exceed 25 keV. Initial calculations suggested that this saturation was due to strongly enhanced transport in the central region. It is shown in this paper that the saturation is due to a lack of heating in the plasma center. The power input to electrons in an ICRF minority heating scheme is mainly via collisional transfer from the minority fast ions and a main problem is to maintain a peaked profile of fast ions. In the present experiments the highest fast ion energy content 4MJ has been achieved with a He 3 minority scheme, the equivalent fast ion toroidal β is 8%; electron temperatures in the range 11-14 keV are attained in these pulses. There are several possible physical effects that can give rise to the broadening of the fast ion radial profile: sawteeth, fishbones, fast ion finite orbit effects and Alfven or drift wave turbulence driven by the large gradients of fast ion pressure (discussed in section IV). The existence of such phenomena in many JET pulses means that the calculation of the power input profile by codes which contain purely classical collisional processes can be misleading. Hence an alternative approach is developed in section II; the measured fast ion energy is used directly to evaluate the power input to the central region; the scaling of the electron temperature with the actual power per particle can therefore be determined (section III). (author) 6 refs., 5 figs

Experiments on hot-electron ECRH in the Tandem Mirror Experiment-Upgrade

International Nuclear Information System (INIS)

Stallard, B.W.

1983-01-01

Experiments have begun on the Tandem Mirror Experiment Upgrade (TMX-U) using electron-cyclotron resonant heating (ECRH) to generate the hot electron populations required for thermal barrier operation (Energy E/sub eh/ approx. 50 keV, density n/sub eh/ 12 , and hot-to-cold fraction n/sub eh/n approx. 0.9). For this operation, rf power produced by 28-GHz gyrotrons is injected with extraordinary mode polarization at both fundamental and second harmonic locations. Our initial experiments, which concentrated on startup of the hot electrons, were carried out at low density ( 12 cm - 3 ) where Fokker-Planck calculations predict high heating efficiency when the electron temperature (T/sub e/) is low. Under these conditions, we produced substantial hot electron populations (diamagnetic energy > 400 J, E/sub eh/ in the range of 15 to 50 keV, and n/sub eh//n > 0.5)

Circular waveguide systems for electron-cyclotron-resonant heating of the tandem mirror experiment-upgrade

International Nuclear Information System (INIS)

Felker, B.; Calderon, M.O.; Chargin, A.K.

1983-01-01

Extensive use of electron cyclotron resonant heating (ECRH) in the Tandem Mirror Experiment-Upgrade (TMX-U) requires continuous development of components to improve efficiency, increase reliability, and deliver power to new locations with respect to the plasma. We have used rectangular waveguide components on the experiment and have developed, tested, and installed circular waveguide components. We replaced the rectangular with the circular components because of the greater transmission efficiency and power-handling capability of the circular ones. Design, fabrication, and testing of all components are complete for all systems. In this paper we describe the design criteria for the system

Electron Heating of LHCD Plasma in HT-7 Tokamak

International Nuclear Information System (INIS)

Ding Yonghua; Wan Baonian; Lin Shiyao; Chen Zhongyong; Hu Xiwei; Shi Yuejiang; Hu Liqun; Kong Wei; Zhang Xiaoqing

2006-01-01

Electron heating via lower hybrid current drive (LHCD) has been investigated in HT-7 superconducting tokamak. Experiments show that the central electron temperature T e0 , the volume averaged electron temperature e > and the peaking factor of the electron temperature Q Te = T e0 / e > increase with the lower hybrid wave (LHW) power. Simultaneously the electron heating efficiency and the electron temperature as the function of the central line-averaged electron density (n e ) and the plasma current (I p ) have also been investigated. The experimental results are in a good agreement with those of the classical collision theory and the LHW power deposition theory

Thermal electron heating rate: a derivation

International Nuclear Information System (INIS)

Hoegy, W.R.

1983-11-01

The thermal electron heating rate is an important heat source term in the ionospheric electron energy balance equation, representing heating by photoelectrons or by precipitating higher energy electrons. A formula for the thermal electron heating rate is derived from the kinetic equation using the electron-electron collision operator as given by the unified theory of Kihara and Aono. This collision operator includes collective interactions to produce a finite collision operator with an exact Coulomb logarithm term. The derived heating rate O(e) is the sum of three terms, O(e) O(p) + S + O(int), which are respectively: (1) primary electron production term giving the heating from newly created electrons that have not yet suffered collisions with the ambient electrons, (2) a heating term evaluated on the energy surface m(e)/2 E(T) at the transition between Maxwellian and tail electrons at E(T), and (3) the integral term representing heating of Maxwellian electrons by energetic tail electrons at energies ET. Published ionospheric electron temperature studies used only the integral term O(int) with differing lower integration limits. Use of the incomplete heating rate could lead to erroneous conclusions regarding electron heat balance, since O(e) is greater than O(int) by as much as a factor of two

Tokamak startup with electron cyclotron heating

International Nuclear Information System (INIS)

Holly, D.J.; Prager, S.C.; Shepard, D.A.; Sprott, J.C.

1980-04-01

Experiments are described in which the startup voltage in a tokamak is reduced by approx. 60% by the use of a modest amount of electron cyclotron resonance heating power for preionization. A 50% reduction in volt-second requirement and impurity reflux are also observed

Tokamak startup with electron cyclotron heating

Energy Technology Data Exchange (ETDEWEB)

Holly, D J; Prager, S C; Shepard, D A; Sprott, J C

1980-04-01

Experiments are described in which the startup voltage in a tokamak is reduced by approx. 60% by the use of a modest amount of electron cyclotron resonance heating power for preionization. A 50% reduction in volt-second requirement and impurity reflux are also observed.

Studies of electron and proton isochoric heating for fast ignition

International Nuclear Information System (INIS)

Mackinnon, A; Key, M; Akli, K; Beg, F; Clarke, R; Clarke, D; Chen, M; Chung, H; Chen, S; Freeman, R; Green, J; Gu, P; Gregori, G; Highbarger, K; Habara, H; Hatchett, S; Hey, D; Heathcote, R; Hill, J; King, J; Kodama, R; Koch, J; Lancaster, K; Langdon, B; Murphy, C; Norreys, P; Neely, D; Nakatsutsumi, M; Nakamura, H; Patel, N; Patel, P; Pasley, J; Snavley, R; Stephens, R; Stoeckl, C; Foord, M; Tabak, M; Theobald, W; Storm, M; Tanaka, K; Tempo, M; Toley, M; Town, R; Wilks, S; VanWoerkom, L; Weber, R; Yabuuchi, T; Zhang, B

2006-01-01

Isochoric heating of inertially confined fusion plasmas by laser driven MeV electrons or protons is an area of great topical interest in the inertial confinement fusion community, particularly with respect to the fast ignition (FI) proposal to use this technique to initiate burn in a fusion capsule. Experiments designed to investigate electron isochoric heating have measured heating in two limiting cases of interest to fast ignition, small planar foils and hollow cones. Data from Cu Kα fluorescence, crystal x-ray spectroscopy of Cu K shell emission, and XUV imaging at 68eV and 256 eV are used to test PIC and Hybrid PIC modeling of the interaction. Isochoric heating by focused proton beams generated at the concave inside surface of a hemi-shell and from a sub hemi-shell inside a cone have been studied with the same diagnostic methods plus imaging of proton induced Kα. Conversion efficiency to protons has also been measured and modeled. Conclusions from the proton and electron heating experiments will be presented. Recent advances in modeling electron transport and innovative target designs for reducing igniter energy and increasing gain curves will also be discussed

Lower hybrid heating experiments in tokamaks: an overview

International Nuclear Information System (INIS)

Porkolab, M.

1985-10-01

Lower hybrid wave propagation theory relevant to heating fusion grade plasmas (tokamaks) is reviewed. A brief discussion of accessibility, absorption, and toroidal ray propagation is given. The main part of the paper reviews recent results in heating experiments on tokamaks. Both electron and ion heating regimes will be discussed. The prospects of heating to high temperatures in reactor grade plasmas will be evaluated

Plasma wave observations during electron and ion gun experiments

International Nuclear Information System (INIS)

Olsen, R.C.; Lowery, D.R.; Weddle, L.E.

1988-01-01

Plasma wave instruments with high temporal and frequency resolution in the 0-6 kHz frequency range have been used to monitor electron gun-employing charge control experiments with the USAF/NASA p78-2 satellite, in order to determine whether plasma wave signatures consistent with the previous inference of electron heating were present. Strong plasma waves were noted near the electron gyrofrequency; these waves can heat ambient low energy electrons, as previously inferred. Attention is given to the two distinct classes of behavior revealed by the ion gun experiments. 16 references

Electron and ion heat transport with lower hybrid current drive and neutral beam injection heating in ASDEX

International Nuclear Information System (INIS)

Soeldner, F.X.; Pereverzev, G.V.; Bartiromo, R.; Fahrbach, H.U.; Leuterer, F.; Murmann, H.D.; Staebler, A.; Steuer, K.H.

1993-01-01

Transport code calculations were made for experiments with the combined operation of lower hybrid current drive and heating and of neutral beam injection heating on ASDEX. Peaking or flattening of the electron temperature profile are mainly explained by modifications of the MHD induced electron heat transport. They originate from current profile changes due to lower hybrid and neutral beam current drive and to contributions from the bootstrap current. Ion heat transport cannot be described by one single model for all heating scenarios. The ion heat conductivity is reduced during lower hybrid heated phases with respect to Ohmic and neutral beam heating. (author). 13 refs, 5 figs

Phased-array antenna system for electron Bernstein wave heating and current drive experiments in QUEST

International Nuclear Information System (INIS)

Idei, H.; Sakaguchi, M.; Kalinnikova, E.I.

2010-11-01

The phased-array antenna system for Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments has been developed in the QUEST. The antenna was designed to excite a pure O-mode wave in the oblique injection for the EBWH/CD experiments, and was tested at a low power level. The measured two orthogonal fields were in excellent agreements with the fields evaluated by a developed Kirchhoff code. The heat load and thermal stress in CW 200 kW operation were analyzed with finite element codes. The phased array has been fast scanned [∼10 4 degree/s] to control the incident polarization and angle to follow time evolutions of the plasma current and density. The RF startup and sustainment experiments were conducted using the developed antenna system. The plasma current (< ∼15 kA) with an aspect ratio of 1.5 was started up and sustained by only RF injection. The long pulse discharge of 10 kA was attained for 40 s with the 30 kW injection. (author)

Advanced electron cyclotron heating and current drive experiments on the stellarator Wendelstein 7-X

Directory of Open Access Journals (Sweden)

Stange Torsten

2017-01-01

Full Text Available During the first operational phase (OP 1.1 of Wendelstein 7-X (W7-X electron cyclotron resonance heating (ECRH was the exclusive heating method and provided plasma start-up, wall conditioning, heating and current drive. Six gyrotrons were commissioned for OP1.1 and used in parallel for plasma operation with a power of up to 4.3 MW. During standard X2-heating the spatially localized power deposition with high power density allowed controlling the radial profiles of the electron temperature and the rotational transform. Even though W7-X was not fully equipped with first wall tiles and operated with a graphite limiter instead of a divertor, electron densities of n e > 3·1019 m-3 could be achieved at electron temperatures of several keV and ion temperatures above 2 keV. These plasma parameters allowed the first demonstration of a multipath O2-heating scenario, which is envisaged for safe operation near the X-cutoff-density of 1.2·1020 m-3 after full commissioning of the ECRH system in the next operation phase OP1.2.

ICRF heating and current drive experiments on TFTR

International Nuclear Information System (INIS)

Rogers, J.H.; Hosea, J.C.; Phillips, C.K.

1996-01-01

Recent experiments in the Ion Cyclotron Range of Frequencies (ICRF) at TFTR have focused on the RF physics relevant to advanced tokamak D-T reactors. Experiments performed either tested confinement in reactor relevant plasmas or tested specific ICRF heating scenarios under consideration for reactors. H-minority heating was used to supply identical heating sources for matched D-T and D only L-mode plasmas to determine the species scaling for energy confinement. Second harmonic tritium heating was performed with only thermal tritium ions in an L-mode target plasma, verifying a possible start-up scenario for the International Thermonuclear Experimental Reactor (ITER). Direct electron heating in Enhanced Reverse Shear (ERS) plasmas has been found to delay the back transition out of the ERS state. D-T mode conversion of the fast magnetosonic wave to an Ion Berstein Wave (IBW) for off-axis heating and current drive has been successfully demonstrated for the first time. Parasitic Li 7 cyclotron damping limited the fraction of the power going to the electrons to less than 30%. Similar parasitic damping by Be 9 could be problematic in ITER. Doppler shifted fundamental resonance heating of beam ions and alpha particles has also been observed

Heat transfer between adsorbate and laser-heated hot electrons

International Nuclear Information System (INIS)

Ueba, H; Persson, B N J

2008-01-01

Strong short laser pulses can give rise to a strong increase in the electronic temperature at metal surfaces. Energy transfer from the hot electrons to adsorbed molecules may result in adsorbate reactions, e.g. desorption or diffusion. We point out the limitations of an often used equation to describe the heat transfer process in terms of a friction coupling. We propose a simple theory for the energy transfer between the adsorbate and hot electrons using a newly introduced heat transfer coefficient, which depends on the adsorbate temperature. We calculate the transient adsorbate temperature and the reaction yield for a Morse potential as a function of the laser fluency. The results are compared to those obtained using a conventional heat transfer equation with temperature-independent friction. It is found that our equation of energy (heat) transfer gives a significantly lower adsorbate peak temperature, which results in a large modification of the reaction yield. We also consider the heat transfer between different vibrational modes excited by hot electrons. This mode coupling provides indirect heating of the vibrational temperature in addition to the direct heating by hot electrons. The formula of heat transfer through linear mode-mode coupling of two harmonic oscillators is applied to the recent time-resolved study of carbon monoxide and atomic oxygen hopping on an ultrafast laser-heated Pt(111) surface. It is found that the maximum temperature of the frustrated translation mode can reach high temperatures for hopping, even when direct friction coupling to the hot electrons is not strong enough

Electron thermal conductivity from heat wave propagation in Wendelstein 7-AS

Energy Technology Data Exchange (ETDEWEB)

Giannone, L.; Erckmann, V; Gasparino, U; Hartfuss, H J; Kuehner, G; Maassberg, H; Stroth, U; Tutter, M [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); W7-AS Team; ECRH Group IPF Stuttgart; Gyrotron Group KFK Karlsruhe

1992-11-01

Heat wave propagation experiments have been carried out on the Wendelstein 7-AS stellarator. The deposition of electron cyclotron resonance heating power is highly localized in the plasma centre, so that power modulation produces heat waves which propagate away from the deposition volume. Radiometry of the electron cyclotron emission is used to measure the generated temperature perturbation. The propagation time delay of the temperature perturbation as a function of distance to the power deposition region is used to determine the electron thermal conductivity [chi][sub e]. This value is then compared with the value determined by global power balance. In contrast to sawtooth propagation experiments in tokamaks, it is found that the value of [chi][sub e] from heat wave propagation is comparable to that calculated by power balance. In addition, inward propagating waves were produced by choosing a power deposition region away from the plasma centre. Experiments were carried out at 70 GHz in the ordinary mode and at 140 GHz in the extraordinary mode. Variations of the modulation power amplitude have demonstrated that the inferred value of [chi][sub e] is independent of the amplitude of the induced temperature perturbations. (author). 29 refs, 11 figs, 5 tabs.

Thermal insulation of high confinement mode with dominant electron heating in comparison to dominant ion heating and corresponding changes of torque input

International Nuclear Information System (INIS)

Sommer, Fabian H.D.

2013-01-01

The ratio of heating power going to electrons and ions will undergo a transition from mixed electron and ion heating as it is in current fusion experiments to dominant electron heating in future experiments and reactors. In order to make valid projections towards future devices the connected changes in plasma response and performance are important to be study and understand: Do electron heated plasmas behave systematically different or is the change of heated species fully compensated by heat exchange from electrons to ions? How does particle transport influence the density profile? Is the energy confinement and the H-mode pedestal reduced with reduced torque input? Does the turbulent transport regime change fundamentally? The unique capabilities of the ECRH system at ASDEX Upgrade enable this change of heated species by replacing NBI with ECRH power and thereby offer the possibility to discuss these and other questions. For low heating powers corresponding to high collisionalities the transition from mixed electron and ion heating to pure electron heating showed next to no degradation of the global plasma parameters and no change of the edge values of kinetic profiles. The electron density shows an increased central peaking with increased ECRH power. The central electron temperature stays constant while the ion temperature decreases slightly. The toroidal rotation decreases with reduced NBI fraction, but does not influence the profile stability. The power balance analysis shows a large energy transfer from electrons to ions, so that the electron heat flux approaches zero at the edge whereas the ion heat flux is independent of heating mix. The ion heat diffusivity exceeds the electron one. For high power, low collisionality discharges global plasma parameters show a slight degradation with increasing electron heating. The density profile shows a strong peaking which remains unchanged when modifying the heating mix. The electron temperature profile is unchanged

Diffusive and convective transport modelling from analysis of ECRH-stimulated electron heat wave propagation

International Nuclear Information System (INIS)

Erckmann, V.; Gasparino, U.; Giannone, L.

1992-01-01

ECRH power modulation experiments in toroidal devices offer the chance to analyze the electron heat transport more conclusively: the electron heat wave propagation can be observed by ECE (or SX) leading to radial profiles of electron temperature modulation amplitude and time delay (phase shift). Taking also the stationary power balance into account, the local electron heat transport can be modelled by a combination of diffusive and convective transport terms. This method is applied to ECRH discharges in the W7-AS stellarator (B=2.5T, R=2m, a≤18 cm) where the ECRH power deposition is highly localized. In W7-AS, the T e modulation profiles measured by a high resolution ECE system are the basis for the local transport analysis. As experimental errors limit the separation of diffusive and convective terms in the electron heat transport for central power deposition, also ECRH power modulation experiments with off-axis deposition and inward heat wave propagation were performed (with 70 GHz o-mode as well as with 140 GHz x-mode for increased absorption). Because collisional electron-ion coupling and radiative losses are only small, low density ECRH discharges are best candidates for estimating the electron heat flux from power balance. (author) 2 refs., 3 figs

High efficiency confinement mode by electron cyclotron heating

International Nuclear Information System (INIS)

Funahashi, Akimasa

1987-01-01

In the medium size nuclear fusion experiment facility JFT-2M in the Japan Atomic Energy Research Institute, the research on the high efficiency plasma confinement mode has been advanced, and in the experiment in June, 1987, the formation of a high efficiency confinement mode was successfully controlled by electron cyclotron heating, for the first time in the world. This result further advanced the control of the formation of a high efficiency plasma confinement mode and the elucidation of the physical mechanism of that mode, and promoted the research and development of the plasma heating by electron cyclotron heating. In this paper, the recent results of the research on a high efficiency confinement mode at the JFT-2M are reported, and the role of the JFT-2M and the experiment on the improvement of core plasma performance are outlined. Now the plasma temperature exceeding 100 million deg C has been attained in large tokamaks, and in medium size facilities, the various measures for improving confinement performance are to be brought forth and their scientific basis is elucidated to assist large facilities. The JFT-2M started the operation in April, 1983, and has accumulated the results smoothly since then. (Kako, I.)

Electron heat transport studies using transient phenomena in ASDEX Upgrade

International Nuclear Information System (INIS)

Jacchia, A.; Angioni, C.; Manini, A.; Ryter, F.; Apostoliceanu, M.; Conway, G.; Fahrbach, H.-U.; Kirov, K.K.; Leuterer, F.; Reich, M.; Sutttrop, W.; Cirant, S.; Mantica, P.; De Luca, F.; Weiland, J.

2005-01-01

Experiments in tokamaks suggest that a critical gradient length may cause the resilient behavior of T e profiles, in the absence of ITBs. This agrees in general with ITG/TEM turbulence physics. Experiments in ASDEX Upgrade using modulation techniques with ECH and/or cold pulses demonstrate the existence of a threshold in R/L Te when T e >T i and T e ≤T i . For T e >T i linear stability analyses indicate that electron heat transport is dominated by TEM modes. They agree in the value of the threshold (both T e and n e ) and for the electron heat transport increase above the threshold. The stabilization of TEM modes by collisions yielded by gyro-kinetic calculations, which suggests a transition from TEM to ITG dominated transport at high collisionality, is experimentally demonstrated by comparing heat pulse and steady-state diffusivities. For the T e ∼T i discharges above the threshold the resilience, normalized by T e 3/2 , is similar to that of the TEM dominated cases, despite very different conditions. The heat pinch predicted by fluid modeling of ITG/TEM turbulence is investigated by perturbative transport in off-axis ECH-heated discharges. (author)

Electron temperature measurements during electron cyclotron heating on PDX using a ten channel grating polychromator

International Nuclear Information System (INIS)

Cavallo, A.; Hsuan, H.; Boyd, D.; Grek, B.; Johnson, D.; Kritz, A.; Mikkelsen, D.; LeBlanc, B.; Takahashi, H.

1984-10-01

During first harmonic electron cyclotron heating (ECH) on the Princeton Divertor Experiment (PDX) (R 0 = 137 cm, a = 40 cm), electron temperature was monitored using a grating polychromator which measured second harmonic electron cyclotron emission from the low field side of the tokamak. Interference from the high power heating pulse on the broadband detectors in the grating instrument was eliminated by using a waveguide filter in the transmission line which brought the emission signal to the grating instrument. Off-axis (approx. 4 cm) location of the resonance zone resulted in heating without sawtooth or m = 1 activity. However, heating with the resonance zone at the plasma center caused very large amplitude sawteeth accompanied by strong m = 1 activity: ΔT/T/sub MAX/ approx. = 0.41, sawtooth period approx. = 4 msec, m = 1 period approx. = 90 μ sec, (11 kHz). This is the first time such intense MHD activity driven by ECH has been observed. (For both cases there was no sawtooth activity in the ohmic phase of the discharge before ECH.) At very low densities there is a clear indication that a superthermal electron population is created during ECH

Development of Thermal Design Program for an Electronic Telecommunication System Using Heat Sink

International Nuclear Information System (INIS)

Lee, Jung Hwan; Kim, Jong Man; Chun, Ji Hwan; Bae, Chul Ho; Suh, Myung Won

2007-01-01

The purpose of this study is to investigate the cooling performance of heat sinks for an electronic telecommunication system by adequate natural convection. Heat generation rates of electronic components and the temperature distributions of heat sinks and surrounding air are analyzed experimentally and numerically. In order to perform the heat transfer analysis for the thermal design of telecommunication system, a program is developed. The program used the graphic user interface environment to determine the arrangement of heat sources, interior fan capacity, and heat sink configuration. The simulation results showed that the heat sinks were able to achieve a cooling capacity of up to 230W at the maximum temperature difference of 19 .deg. C. To verify the results from the numerical simulation, an experiment was conducted under the same condition as the numerical simulation, and their results were compared. The design program gave good prediction of the effects of various parameters involved in the design of a heat sinks for an electronic telecommunication system

Hybrid simulation of electron cyclotron resonance heating

Energy Technology Data Exchange (ETDEWEB)

Ropponen, T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, FI-40014 (Finland)], E-mail: tommi.ropponen@phys.jyu.fi; Tarvainen, O. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Suominen, P. [CERN Geneve 23, CH-1211 (Switzerland); Koponen, T.K. [Department of Physics, University of Jyvaeskylae, Nanoscience Center, P.O. Box 35, FI-40014 (Finland); Kalvas, T.; Koivisto, H. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, FI-40014 (Finland)

2008-03-11

Electron Cyclotron Resonance (ECR) heating is a fundamentally important aspect in understanding the physics of Electron Cyclotron Resonance Ion Sources (ECRIS). Absorption of the radio frequency (RF) microwave power by electron heating in the resonance zone depends on many parameters including frequency and electric field strength of the microwave, magnetic field structure and electron and ion density profiles. ECR absorption has been studied in the past by e.g. modelling electric field behaviour in the resonance zone and its near proximity. This paper introduces a new ECR heating code that implements damping of the microwave power in the vicinity of the resonance zone, utilizes electron density profiles and uses right hand circularly polarized (RHCP) electromagnetic waves to simulate electron heating in ECRIS plasma.

Induction-linac based free-electron laser amplifiers for plasma heating

International Nuclear Information System (INIS)

Jong, R.A.

1988-01-01

We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging form 280 to 560 GHz. 7 refs., 1 tab

Plasma heating by a relativistic electron beam

International Nuclear Information System (INIS)

Janssen, G.C.A.M.

1983-01-01

This thesis is devoted to the interaction of a Relativistic Electron Beam (REB) with a plasma. The goal of the experiment described herein is to study in detail the mechanism of energy transfer from the beam to the plasma. The beam particles have an energy of 800 keV, a current of 6 kA, a diameter of 3 cm and an adjustable pulse length of 50-150 ns. This beam is injected into cold hydrogen and helium plasmas with densities ranging from 10 18 to 10 20 m -3 . First, the technical aspects of the experiment are described. Then measurements on the hf fields excited by the REB-plasma are presented (optical line profiles and spectra of beam electrons). The final section is devoted to plasma heating. (Auth.)

Electron-cyclotron-resonant-heated electron distribution functions

International Nuclear Information System (INIS)

Matsuda, Y.; Nevins, W.M.; Cohen, R.H.

1981-01-01

Recent studies at Lawrence Livermore National Laboratory (LLNL) with a bounce-averaged Fokker-Planck code indicate that the energetic electron tail formed by electron-cyclotron resonant heating (ECRH) at the second harmonic is not Maxwellian. We present the results of our bounce-averaged Fokker-Planck code along with some simple analytic models of hot-electron distribution functions

Electron velocity-space diffusion in a micro-unstable ECRH [electron cyclotron resonance heated] mirror plasma

International Nuclear Information System (INIS)

Hokin, S.A.

1987-09-01

An experimental study of the velocity-space diffusion of electrons in an electron cyclotron resonance heated (ECRH) mirror plasma, in the presence of micro-unstable whistler rf emission, is presented. It is found that the dominant loss mechanism for hot electrons is endloss produced by rf diffusion into the mirror loss cone. In a standard case with 4.5 kW of ECRH power, this loss limits the stored energy to 120 J with an energy confinement time of 40 ms. The energy confinement time associated with collisional scattering is 350 ms in this case. Whistler microinstability rf produces up to 25% of the rf-induced loss. The hot electron temperature is not limited by loss of adiabaticity, but by rf-induced loss of high energy electrons, and decreases with increasing rf power in strong diffusion regimes. Collisional loss is in agreement with standard scattering theory. No super-adiabatic effects are clearly seen. Experiments in which the vacuum chamber walls are lined with microwave absorber reveal that single pass absorption is limited to less than 60%, whereas experiments with reflecting walls exhibit up to 90% absorption. Stronger diffusion is seen in the latter, with a hot electron heating rate which is twice that of the absorber experiments. This increase in diffusion can be produced by two distinct aspects of wall-reflected rf: the broader spatial rf profile, which enlarges the resonant region in velocity space, or a reduction in super-adiabatic effects due to randomization of the electron gyrophase. Since no other aspects of super-adiabaticity are observed, the first mechanism appears more likely. 39 refs., 54 figs

Extreme Ultraviolet Imaging of Electron Heated Targets in Petawatt Laser Experiments

International Nuclear Information System (INIS)

Ma, T.; MacPhee, A.; Key, M.; Akli, K.; Mackinnon, A.; Chen, C.; Barbee, T.; Freeman, R.; King, J.; Link, A.; Offermann, D.; Ovchinnikov, V.; Patel, P.; Stephens, R.; VanWoerkom, L.; Zhang, B.; Beg, F.

2007-01-01

The study of the transport of electrons, and the flow of energy into a solid target or dense plasma, is instrumental in the development of fast ignition inertial confinement fusion. An extreme ultraviolet (XUV) imaging diagnostic at 256 eV and 68 eV provides information about heating and energy deposition within petawatt laser-irradiated targets. XUV images of several irradiated solid targets are presented

High power electron cyclotron heating in ISX and ORMAK Upgrade at ORNL

International Nuclear Information System (INIS)

England, A.C.; Eldridge, O.C.; Marcus, F.B.; Sprott, J.C.; Namkung, W.; Wilgen, J.B.

1976-05-01

A phased program of plasma heating at the electron cyclotron frequency is proposed for the Oak Ridge tokamaks ISX and ORMAK Upgrade. The past history of the program of electron cyclotron heating (ECH) at ORNL on mirrors and in the ELMO Bumpy Torus has been successful. Future technological developments in the production of high power high frequency microwave tubes look promising at this time. The physics of wave propagation and particle heating are fairly well understood and indicate the viability of this technique. Studies on breakdown and on runaway electron reduction will provide useful information for larger machines. Recent experiments in the USSR on small tokamaks have shown that ECH is a viable heating technique. Providing that the microwave tubes become available, the engineering considerations suggest that the technique is practical and workable, based on present day technology

Study of electronic heat transport in plasma through diagnosis based on modulated electron cyclotron heating; Etudes de transport de la chaleur electronique par injection modulee d'ondes a la frequence cyclotronique electronique

Energy Technology Data Exchange (ETDEWEB)

Clemencon, A.; Guivarch, C

2003-07-01

In order to make nuclear fusion energetically profitable, it is crucial to heat and confine the plasma efficiently. Studying the behavior of the heat diffusion coefficient is a key issue in this matter. The use of modulated electron cyclotron heating as a diagnostic has suggested the existence of a transport barrier under certain plasma conditions. We have determined the solution to the heat transport equation, for several heat diffusion coefficient profiles. By comparing the analytical solutions with experimental data; we are able to study the heat diffusion coefficient profile. Thus, in certain experiments, we can confirm that the heat diffusion coefficient switches from low to high values at the radius where the electron cyclotron heat deposition is made. (authors)

Density response to central electron heating: theoretical investigations and experimental observations in ASDEX Upgrade

Science.gov (United States)

Angioni, C.; Peeters, A. G.; Garbet, X.; Manini, A.; Ryter, F.; ASDEX Upgrade Team

2004-08-01

Theory of ion temperature gradient (ITG) and trapped electron modes (TEMs) is applied to the study of particle transport in experimental conditions with central electron heating. It is shown that in the unstable domain of TEMs, the electron thermodiffusive flux is directed outwards. By means of such a flux, a mechanism is identified likely to account for density flattening with central electron heating. Theoretical predictions are compared with experimental observations in ASDEX Upgrade. A parameter domain (including L- and H-mode plasmas) is identified, in which flattening with central electron heating is observed in the experiments. In general, this domain turns out to be the same domain in which the dominant plasma instability is a TEM. On the contrary, the dominant instability is an ITG in plasmas whose density profile is not affected significantly by central electron heating. The flattening predicted by quasi-linear theory for low density L-mode plasmas is too small compared to the experimental observations. At very high density, even when the dominant instability is an ITG, electron heating can provide density flattening, via the coupling with the ion heat channel. In these conditions the anomalous diffusivity increases in response to the increased ion heat flux, while the large collisionality makes the anomalous pinch small and the Ware pinch important.

X-ray imaging studies of electron cyclotron microwave-heated plasmas in the Tandem Mirror Experiment-Upgrade

International Nuclear Information System (INIS)

Failor, B.H.

1986-02-01

An x-ray pinhole camera designed to efficiently detect photons with energies between 5 and 250 keV was built to image bremsstrahlung emission from a microwave-heated hot electron plasma. This plasma is formed at one of the thermal barrier locations in the Tandem Experiment-Upgrade at Lawrence Livermore National Laboratory. The instrument consists of a lead aperture, an x-ray converter in the form of a sodium-activated cesium iodide scintillator, light intensifier electronics, and a recording medium that may either be high speed film or a CCD array. The nominal spatial and temporal resolutions are one part in 40 and 17 msec, respectively. The component requirements for optimum performance were determined both analytically and by computer simulation, and were verified experimentally. The details of these results are presented. The instrument has been used to measure x-ray emission from the TMX-U west end cell. Data acquired with the x-ray camera has allowed us to infer the temporal evolution of the mirror-trapped electron radial profile

Electronic specific heats in metal--hydrogen systems

International Nuclear Information System (INIS)

Flotow, H.E.

1979-01-01

The electronic specific heats of metals and metal--hydrogen systems can in many cases be evaluated from the measured specific heats at constant pressure, C/sub p/, in the temperature range 1 to 10 K. For the simplest case, C/sub p/ = γT + βT 3 , where γT represents the specific heat contribution associated with the conduction electrons, and βT 3 represents lattice specific heat contribution. The electronic specific heat coefficient, γ, is important because it is proportional to electron density of states at the Fermi surface. A short description of a low temperature calorimetric cryostat employing a 3 He/ 4 He dilution refrigeration is given. Various considerations and complications encountered in the evaluation of γ from specific heat data are discussed. Finally, the experimental values of γ for the V--Cr--H system and for the Lu--H system are summarized and the variations of γ as function of alloy composition are discussed

Progress of High Heat Flux Component Manufacture and Heat Load Experiments in China

Energy Technology Data Exchange (ETDEWEB)

Liu, X.; Lian, Y.; Xu, Z.; Chen, J.; Chen, L.; Wang, Q.; Duan, X., E-mail: xliu@swip.ac.cn [Southwestern Institute of Physics, Chengu (China); Luo, G. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Yan, Q. [University of Science and Technology Beijing, Beijing (China)

2012-09-15

Full text: High heat flux components for first wall and divertor are the key subassembly of the present fusion experiment apparatus and fusion reactors in the future. It is requested the metallurgical bonding among the plasma facing materials (PFMs), heat sink and support materials. As to PFMs, ITER grade vacuum hot pressed beryllium CN-G01 was developed in China and has been accepted as the reference material of ITER first wall. Additionally pure tungsten and tungsten alloys, as well as chemical vapor deposition (CVD) W coating are being developed for the aims of ITER divertor application and the demand of domestic fusion devices, and significant progress has been achieved. For plasma facing components (PFCs), high heat flux components used for divertor chamber are being studied according to the development program of the fusion experiment reactor of China. Two reference joining techniques of W/Cu mockups for ITER divertor chamber are being developed, one is mono-block structure by pure copper casting of tungsten surface following by hot iso-static press (HIP), and another is flat structure by brazing. The critical acceptance criteria of high heat flux components are their high heat load performance. A 60 kW Electron-beam Material testing Scenario (EMS-60) has been constructed at Southwestern Institute of Physics (SWIP),which adopts an electron beam welding gun with maximum energy of 150 keV and 150 x 150 mm{sup 2} scanning area by maximum frame rate of 30 kHz. Furthermore, an Engineering Mockup testing Scenario (EMS-400) facility with 400 kW electron-beam melting gun is under construction and will be available by the end of this year. After that, China will have the comprehensive capability of high heat load evaluation from PFMs and small-scale mockups to engineering full scale PFCs. A brazed W/CuCrZr mockup with 25 x 25 x 40 mm{sup 3} in dimension was tested at EMS-60. The heating and cooling time are 10 seconds and 15 seconds, respectively. The experiment

Observations of electron heating during 28 GHz microwave power application in proto-MPEX

Science.gov (United States)

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.).

Study of plasma start-up initiated by second harmonic electron cyclotron resonance heating on WEGA experiment

International Nuclear Information System (INIS)

Preynas, M.; Laqua, H. P.; Otte, M.; Stange, T.; Aßmus, D.; Wauters, T.

2014-01-01

Although both 1st harmonic ordinary mode (O1) and 2nd harmonic extra-ordinary mode (X2) have been successfully used to initiate pre-ionization and breakdown in many devices, a complete theoretical model is still missing to explain the success of this method. Moreover, some experimental observations are not completely understood, such as what occurs during the delay time between the turn-on of ECRH power and first signals of density or light measurements. Since during this free period the ECRH power has to be absorbed by in-vessel components, it is of prime importance to know what governs this delay time. Recently, dedicated start-up experiments have been performed on WEGA, using a 28 GHz ECRH system in X2-mode. This machine has the interesting capability to be run also as a tokamak allowing comparative experiments between stellarator (ι/2π > 0) and tokamak (ι/2π = 0) configurations. Different scans in heating power, neutral gas pressure, and rotational transform (ι) show clearly that the start-up is a two step process. A first step following the turn-on of the ECRH power during which no measurable electron density (or just above the noise level in some cases), ECE and radiated power is detected. Its duration depends strongly on the level of injected power. The second step corresponds to the gas ionization and plasma expansion phase, with a velocity of density build-up and filling-up of the vessel volume depending mainly on pressure, gas and rotational transform. Moreover, an interesting scenario of ECRH pre-ionization without loop voltage in tokamak configuration by applying a small optimal vertical field is relevant for start-up assistance on future experiments like ITER. The results from this experimental parametric study are useful for the modeling of the start-up assisted by the second harmonic electron cyclotron resonance heating. The aim of this work is to establish predictive scenarios for both ITER and W7-X operation

Study of plasma start-up initiated by second harmonic electron cyclotron resonance heating on WEGA experiment

Energy Technology Data Exchange (ETDEWEB)

Preynas, M.; Laqua, H. P.; Otte, M.; Stange, T.; Aßmus, D. [Max Planck Institut für Plasmaphysik, EURATOM Association, D-17491 Greifswald (Germany); Wauters, T. [Association Euratom-Belgian State, LPP-ERM/KMS, 1000 Brussels (Belgium)

2014-02-12

Although both 1st harmonic ordinary mode (O1) and 2nd harmonic extra-ordinary mode (X2) have been successfully used to initiate pre-ionization and breakdown in many devices, a complete theoretical model is still missing to explain the success of this method. Moreover, some experimental observations are not completely understood, such as what occurs during the delay time between the turn-on of ECRH power and first signals of density or light measurements. Since during this free period the ECRH power has to be absorbed by in-vessel components, it is of prime importance to know what governs this delay time. Recently, dedicated start-up experiments have been performed on WEGA, using a 28 GHz ECRH system in X2-mode. This machine has the interesting capability to be run also as a tokamak allowing comparative experiments between stellarator (ι/2π > 0) and tokamak (ι/2π = 0) configurations. Different scans in heating power, neutral gas pressure, and rotational transform (ι) show clearly that the start-up is a two step process. A first step following the turn-on of the ECRH power during which no measurable electron density (or just above the noise level in some cases), ECE and radiated power is detected. Its duration depends strongly on the level of injected power. The second step corresponds to the gas ionization and plasma expansion phase, with a velocity of density build-up and filling-up of the vessel volume depending mainly on pressure, gas and rotational transform. Moreover, an interesting scenario of ECRH pre-ionization without loop voltage in tokamak configuration by applying a small optimal vertical field is relevant for start-up assistance on future experiments like ITER. The results from this experimental parametric study are useful for the modeling of the start-up assisted by the second harmonic electron cyclotron resonance heating. The aim of this work is to establish predictive scenarios for both ITER and W7-X operation.

Theory of ionospheric heating experiments

International Nuclear Information System (INIS)

Cragin, B.L.

1975-01-01

A brief description of the F region ionospheric heating experiments is given including some historical notes and a brief summary of the observations. A theory for the phenomenon of ''artificial spread F'' is presented. The explanation is in terms of scattering by approximately field-aligned, large scale ionization density irregularities, which are produced by a thermal version of the stimulated Brillouin scattering instability in which the heating wave decays into another electromagnetic wave and an electrostatic wave of very low frequency. This thermal instability differs from conventional stimulated Brillouin scattering in that the low frequency wave is driven by differential heating in the interference pattern of the two electromagnetic waves, rather than by the usual ponderomotive force. Some aspects of the theory of the phenomenon of ''wide-band attenuation'' or ''anomalous absorption'' of a probing electromagnetic wave. Some general results from the theory of wave propagation in a random medium are used to derive equations describing the absorption of a probing electromagnetic wave due to scattering (by large scale irregularities) into new electromagnetic waves or (by small scale irregularities) into electron plasma oscillations

Heated electron distributions from resonant absorption

International Nuclear Information System (INIS)

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

1975-01-01

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

Temporal evolutions of electron temperature and density of turbulently-heated tokamak plasmas in TRIAM-1

Energy Technology Data Exchange (ETDEWEB)

Hiraki, N; Nakamura, K; Nakamura, Y; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1981-04-01

The temporal evolution of the electron temperature and density are measured in a turbulent heating experiment in TRIAM-1. Skin-like profiles of the electron temperature and density are clearly observed. The anomality in the electrical resistivity of the plasma in this skin-layer is estimated, and the plasma heating in this skin-layer is regarded as being due to anomalous joule heating arising from this anomalous resistivity. The ratio of drift velocity to electron thermal velocity in the layer is also calculated, and it is shown that the conditions needed to make the current-driven ion-acoustic instability triggerable are satisfied.

Electron cyclotron heating in the TARA axiplug

International Nuclear Information System (INIS)

Mauel, M.E.

1983-01-01

The ecrh system for TARA's axiplug has been designed to maximize the plug's central-cell confining potential. This requires high RF field energy to strongly distort the electron velocity distribution. Two cases were considered: (1) single-frequency heating of both the plug at omega = omega/sub c/ and the barrier at omega = 2 omega/sub c/ as used in TMX-U, and (2) two frequency heating with both the plug and the barrier illuminated at omega = omega/sub c/. The second approach appeared more promising for the TARA parameters although the experiment is designed to investigate both. Numerical ray-tracing and Fokker-Planck calculations were performed to aid with the design. The gyrotrons and their transmission systems will also be discussed in terms of the μ-wave absorption and propagation in both the initial and steady-state electron distributions. In particular, the cavity launching system in the barrier is described which should give high RF field energy at high efficiency even at the low absorption characteristic of the steady-state RF-equilibrium

Design and fabrication of circular and rectangular components for electron-cyclotron-resonant heating of tandem mirror experiment-upgrade

International Nuclear Information System (INIS)

Felker, B.; Calderon, M.O.; Chargin, A.K.

1983-01-01

The electron-cyclotron-resonant heating (ECRH) systems of rectangular waveguides on Tandem Mirror Experiment-Upgrade (TMX-U) operated with a overall efficiency of 50%, each system using a 28-GHz, 200-kW pulsed gyrotron. We designed and built four circular-waveguide systems with greater efficiency and greater power-handling capabilities to replace the rectangular waveguides. Two of these circular systems, at the 5-kG second-harmonic heating locations, have a total transmission efficiency of >90%. The two systems at the 10-kG fundamental heating locations have a total transmission efficiency of 80%. The difference in efficiency is due to the additional components required to launch the microwaves in the desired orientation and polarization with respect to magnetic-field lines at the 10-kG points. These systems handle the total power available from each gyrotron but do not have the arcing limitation problem of the rectangular waveguide. Each system requires several complex components. The overall physical layout and the design considerations for the rectangular and circular waveguide components are described here

Design and fabrication of circular and rectangular components for electron-cyclotron-resonant heating of tandem mirror experiment-upgrade

Energy Technology Data Exchange (ETDEWEB)

Felker, B.; Calderon, M.O.; Chargin, A.K.; Coffield, F.E.; Lang, D.D.; Rubert, R.R.; Pedrotti, L.R.; Stallard, B.W.; Gallagher, N.C. Jr.; Sweeney, D.W.

1983-11-18

The electron-cyclotron-resonant heating (ECRH) systems of rectangular waveguides on Tandem Mirror Experiment-Upgrade (TMX-U) operated with a overall efficiency of 50%, each system using a 28-GHz, 200-kW pulsed gyrotron. We designed and built four circular-waveguide systems with greater efficiency and greater power-handling capabilities to replace the rectangular waveguides. Two of these circular systems, at the 5-kG second-harmonic heating locations, have a total transmission efficiency of >90%. The two systems at the 10-kG fundamental heating locations have a total transmission efficiency of 80%. The difference in efficiency is due to the additional components required to launch the microwaves in the desired orientation and polarization with respect to magnetic-field lines at the 10-kG points. These systems handle the total power available from each gyrotron but do not have the arcing limitation problem of the rectangular waveguide. Each system requires several complex components. The overall physical layout and the design considerations for the rectangular and circular waveguide components are described here.

Heating experiments of JT-60

International Nuclear Information System (INIS)

1987-01-01

In JT-60, after the finish of the first stage Joule experiment, the heating facilities were installed, and the heating experiment was started in August, 1986. As to neutral beam injection, the beam injection experiment at the maximum rating 20 MW carried out, and also as to RF, the injection experiment up to 1.4 MW was carried out in both ion cyclotron and low band hybrid waves. The results worthy of special mention in the heating experiment were the success in the current drive up to 1.7 MA at maximum using low band hybrid waves and the improvement of plasma confinement characteristics obtained by the compound heating of NBI and RF. In this paper, the main results of these heating experiments and their significance are explained. The JT-60 is the testing facilities for attaining the critical plasma condition by additionally heating the plasma which is generated by Joule electric discharge with NBI and RF heatings. The experimental operation cycle of the JT-60 consists of the unit cycle of two weeks, and the number of days in operation is nine days. The temperature of heated plasma rose to 70 million deg C in the 20 MW NBI heating. Hereafter, the improvement of confinement time by increasing the stored energy of plasma is attempted. (Kako, I.)

Electron and ion cyclotron heating calculations in the tandem-mirror modeling code MERTH

International Nuclear Information System (INIS)

Smith, G.R.

1985-01-01

To better understand and predict tandem-mirror experiments, we are building a comprehensive Mirror Equilibrium Radial Transport and Heating (MERTH) code. In this paper we first describe our method for developing the code. Then we report our plans for the installation of physics packages for electron- and ion-cyclotron heating of the plasma

Localized Electron Heating by Strong Guide-Field Magnetic Reconnection

Science.gov (United States)

Guo, Xuehan; Sugawara, Takumichi; Inomoto, Michiaki; Yamasaki, Kotaro; Ono, Yasushi; UTST Team

2015-11-01

Localized electron heating of magnetic reconnection was studied under strong guide-field (typically Bt 15Bp) using two merging spherical tokamak plasmas in Univ. Tokyo Spherical Tokamak (UTST) experiment. Our new slide-type two-dimensional Thomson scattering system documented for the first time the electron heating localized around the X-point. The region of high electron temperature, which is perpendicular to the magnetic field, was found to have a round shape with radius of 2 [cm]. Also, it was localized around the X-point and does not agree with that of energy dissipation term Et .jt . When we include a guide-field effect term Bt / (Bp + αBt) for Et .jt where α =√{ (vin2 +vout2) /v∥2 } , the energy dissipation area becomes localized around the X-point, suggesting that the electrons are accelerated by the reconnection electric field parallel to the magnetic field and thermalized around the X-point. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus,'' a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Fellows 15J03758.

Inside launch electron cyclotron heating and current drive on DITE

International Nuclear Information System (INIS)

Ashraf, M.; Deliyanakis, N.

1989-01-01

Electron cyclotron resonance heating at 60 GHz has been carried out on DITE (R = 1.2 m, a = 0.24 m) to investigate heating and current drive using the extraordinary mode launched with finite k parallel from the high field side. The first clear evidence of Doppler shifted resonance absorption in a near-thermal plasma is obtained. The heating efficiency is observed to fall sharply at densities above cut-off for the wave. At lower densities the increment in power to the limiter is measured during ECRH and is compared with that expected from the global power balance. The degradation in particle confinement often associated with ECRH is observed as an increased particle flux at the boundary driven by local electrostatic fluctuations. Initial experiments on the electron cyclotron wave driven current at the second harmonic show effects that are consistent with the low efficiency expected from theory including trapped particle effects. (author). 9 refs, 4 figs

Heat load of a GaAs photocathode in an SRF electron gun

International Nuclear Information System (INIS)

Wang Erdong; Zhao Kui; Jorg Kewisch; Ilan Ben-Zvi; Andrew Burrill; Trivini Rao; Wu Qiong; Animesh Jain; Ramesh Gupta; Doug Holmes

2011-01-01

A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs. (authors)

Results from transient transport experiments in Rijnhuizen tokamak project: Heat convection, transport barriers and 'non-local' effects

International Nuclear Information System (INIS)

Mantica, P.; Gorini, G.; Hogeweij, G.M.D.; Kloe, J. de; Lopez Cardozo, N.J.; Schilham, A.M.R.

2001-01-01

An overview of experimental transport studies performed on the Rijnhuizen Tokamak Project (RTP) using transient transport techniques in both Ohmic and ECH dominated plasmas is presented. Modulated Electron Cyclotron Heating (ECH) and oblique pellet injection (OPI) have been used to induce electron temperature (T e ) perturbations at different radial locations. These were used to probe the electron transport barriers observed near low order rational magnetic surfaces in ECH dominated steady-state RTP plasmas. Layers of inward electron heat convection in off-axis ECH plasmas were detected with modulated ECH. This suggests that RTP electron transport barriers consist of heat pinch layers rather than layers of low thermal diffusivity. In a different set of experiments, OPI triggered a transient rise of the core T e due to an increase of the T e gradient in the 1< q<2 region. These transient transport barriers were probed with modulated ECH and found to be due to a transient drop of the electron heat diffusivity, except for off-axis ECH plasmas, where a transient inward pinch is also observed. Transient transport studies in RTP could not solve this puzzling interplay between heat diffusion and convection in determining an electron transport barrier. They nevertheless provided challenging experimental evidence both for theoretical modelling and for future experiments. (author)

Development of laser heated high current DC electron gun

International Nuclear Information System (INIS)

Banerjee, Srutarshi; Bhattacharjee, Dhruva; Kandaswamy, E.; Ghodke, S.R.; Tiwari, Rajnish; Bakhtsingh, R.I.

2015-01-01

The paper deals with the development of a Laser heated cathode for Electron Accelerator. The electron gun is meant for Megawatt-class DC Accelerator for Electron Beam Flue Gas Treatment applications. Conventionally, LaB 6 cathode is indirectly heated by tungsten filaments whereas in the newly proposed gun, Laser is utilized for heating. A Nd:YAG Laser is used to heat the LaB 6 cathode to emission temperatures. The characterization of cathode heating at various Laser powers has been carried out. In initial trials, it has been observed that with 125 W of Laser power, the LaB 6 pellet was heated to 1315 ° C. Based on these experimental results, an electron gun rated for 30 kV, 350 mA CW has been designed. The optimization of gun electrode geometry has been done using CST Particle Studio in order to tune the various electron gun parameters. The beam diameter obtained in simulation is 8 mm at 100 mm from the LaB 6 cathode. The perveance obtained is 7.1 x 10 -8 A/V 3/2 . The Laser heated cathode has the advantages of eliminating the magnetic field effects of filament on the electron beam, electrical isolation needed for gun filament power supplies and better electron beam emittances. (author)

Formation of stable, high-beta, relativistic-electron plasmas using electron cyclotron heating

International Nuclear Information System (INIS)

Guest, G.E.; Miller, R.L.

1988-01-01

A one-dimensional, steady-state, relativistic Fokker-Planck model of electron cyclotron heating (ECH) is used to analyse the heating kinetics underlying the formation of the two-component hot-electron plasmas characteristic of ECH in magnetic mirror configurations. The model is first applied to the well diagnosed plasmas obtained in SM-1 and is then used to simulate the effective generation of relativistic electrons by upper off-resonant heating (UORH), as demonstrated empirically in ELMO. The characteristics of unstable whistler modes and cyclotron maser modes are then determined for two-component hot-electron plasmas sustained by UORH. Cyclotron maser modes are shown to be strongly suppressed by the colder background electron species, while the growth rates of whistler modes are reduced by relativistic effects to levels that may render them unobservable, provided the hot-electron pressure anisotropy is below an energy dependent threshold. (author). 29 refs, 10 figs, 1 tab

A megawatt-level 28 GHz heating system for the National Spherical Torus Experiment Upgrade

Directory of Open Access Journals (Sweden)

Taylor G.

2015-01-01

Full Text Available The National Spherical Torus Experiment Upgrade (NSTX-U will operate at axial toroidal fields of ≤ 1 T and plasma currents, Ip ≤ 2 MA. The development of non-inductive (NI plasmas is a major long-term research goal for NSTX-U. Time dependent numerical simulations of 28 GHz electron cyclotron (EC heating of low density NI start-up plasmas generated by Coaxial Helicity Injection (CHI in NSTX-U predict a significant and rapid increase of the central electron temperature (Te(0 before the plasma becomes overdense. The increased Te(0 will significantly reduce the Ip decay rate of CHI plasmas, allowing the coupling of fast wave heating and neutral beam injection. A megawatt-level, 28 GHz electron heating system is planned for heating NI start-up plasmas in NSTX-U. In addition to EC heating of CHI start-up discharges, this system will be used for electron Bernstein wave (EBW plasma start-up, and eventually for EBW heating and current drive during the Ip flattop.

Theory of free-electron-laser heating and current drive in magnetized plasmas

International Nuclear Information System (INIS)

Cohen, B.I.; Cohen, R.H.; Nevins, W.M.; Rognlien, T.D.

1991-01-01

The introduction of a powerful new microwave source, the free-electron laser, provides new opportunities for novel heating and current-drive schemes to be used in toroidal fusion devices. This high-power, pulsed source has a number of technical advantages for these applications, and its use is predicted to lead to improved current-drive efficiencies and opacities in reactor-grade fusion plasmas in specific cases. The Microwave Tokamak Experiment at the Lawrence Livermore National Laboratory will provide a test for some of these new heating and current-drive schemes. Although the motivation for much of this research has derived from the application of a free-electron laser to the heating of a tokamak plasma at a frequency near the electron cyclotron frequency, the underlying physics, i.e., the highly nonlinear interaction of an intense, pulsed, coherent electromagnetic wave with an electron in a magnetized plasma including relativistic effects, is of general interest. Other relevant applications include ionospheric modification by radio-frequency waves, high-energy electron accelerators, and the propagation of intense, pulsed electromagnetic waves in space and astrophysical plasmas. This review reports recent theoretical progress in the analysis and computer simulation of the absorption and current drive produced by intense pulses, and of the possible complications that may arise, e.g., parametric instabilities, nonlinear self-focusing, trapped-particle sideband instability, and instabilities of the heated plasma

Tokamak start-up with electron-cyclotron heating

International Nuclear Information System (INIS)

Holly, D.J.; Prager, S.C.; Shepard, D.A.; Sprott, J.C.

1981-01-01

Experiments are described in which the start-up voltage in a tokamak is reduced by about a factor of two by the use of a modest amount of electron cyclotron resonance heating power for pre-ionization. The solution of the zero-dimensional start-up equations indicates that the effect is due to the high initial density which increases the rate at which the conductivity increases in the neutral-dominated initial plasma. The effect extrapolates favourably to larger tokamaks. A 50% reduction in the start-up volt-second requirement and impurity reflux is also observed. (author)

Tokamak start-up with electron-cyclotron heating

Energy Technology Data Exchange (ETDEWEB)

Holly, D J; Prager, S C; Shepard, D A; Sprott, J C [Wisconsin Univ., Madison (USA)

1981-11-01

Experiments are described in which the start-up voltage in a tokamak is reduced by about a factor of two by the use of a modest amount of electron cyclotron resonance heating power for pre-ionization. The solution of the zero-dimensional start-up equations indicates that the effect is due to the high initial density which increases the rate at which the conductivity increases in the neutral-dominated initial plasma. The effect extrapolates favourably to larger tokamaks. A 50% reduction in the start-up volt-second requirement and impurity reflux is also observed.

Review of preliminary additional heating experiments in JT-60 (Aug. - Nov., 1986)

International Nuclear Information System (INIS)

1987-03-01

This is a prompt report on preliminary additional heating experiments in JT-60 from August to November in 1986. Neutral beam heating power was raised up to 20 MW in about a month. Plasma stored energy is about 2 MJ and energy confinement time is 0.1 ∼ 0.12 sec with the maximum heating power. The energy confinement time shows L-mode like deterioration with power, while it has little dependence on electron density. The maximum ion temperature of ∼ 7 keV and electron temperature of 4.5 keV were obtained at relatively low electron density (n-bar e = 2 - 3 x 10 19 m -3 ). Lower hybrid wave could efficiently drive plasma current up to 1.7 MA with 1.2 MW LH power. The current drive efficiency is 1 ∼ 1.7 in ohmically heated plasmas and 2 ∼ 2.8 in NB heated plasmas. Futhermore the energy confinement was improved when neutral beam was injected into entirely current driven discharges of 1 MA by LH in contrast to inductively driven target plasmas. Similar improvement in energy confinement was observed during combined heating with NB and ion cyclotron wave. (author)

Production of hot electrons in mirror systems associated with ECR heating with longitudinal input of microwaves

International Nuclear Information System (INIS)

Zhil'tsov, V.A.; Skovoroda, A.A.; Timofeev, A.V.; Kharitonov, K.Yu.; Shcherbakov, A.G.

1991-01-01

Almost all experiments on ECR plasma heating are accompanied by the formation of hot electrons (i.e., electrons with energy substantially greater than the average of the bulk population). In mirror systems these electrons may determine the basic energy content (β) of the plasma. In this paper, results are presented from experimental measurements of the hot electron population resulting from ECR heating of the plasma in OGRA-4. A theoretical model is developed which describes the hot electron dynamics and the propagation of electromagnetic oscillations in the plasma self-consistently. The results obtained with this model are in agreement with experimental data

Electron cyclotron resonance heating on the W VII A-stellarator

International Nuclear Information System (INIS)

Wilhelm, R.; Erckmann, V.; Janzen, G.

1985-01-01

Plasma build-up and heating of OH-current free plasmas by ECR-wave irradiation were investigated on the WENDELSTEIN VII-A stellarator using three kinds of wave launching: direct irradiation of the gyrotron modes from the low field side, or advanced wave launching in 0-mode polarization from the low field side, the nonabsorbed fraction being reflected back to the plasma from the high field side in X-mode polarization. An increase of the central electron temperature from 0.7 keV (TE 02 mode) to 1.2 keV (TE 11 , HE 11 mode) was observed which is explained by the narrow and well centred power deposition profiles for TE 11 , HE 11 modes. However, there is only a slight increase of the heating efficiency from 40% to 50%. The reflected X-mode fraction does not contribute to bulk plasma heating via Bernstein wave conversion and absorption as expected. The reason seems to be local absorption of the arising electron Bernstein waves due to a macroscopically turbulent structure around the upper hybrid resonance layer. Correlated with X-mode irradiation direct ion heating was observed (500 eV ion tail), possibly due to low frequency decay waves. In all ECRH experiments a toroidal plasma current was generated due to asymmetrically confined fast electrons. Optimum confinement in the shearless l=2 configuration was achieved at most irrational values of the rotational transform with small toroidal net current. It can be concluded from a numerical 1D-transport analysis that neoclassical electron confinement seems to be dominant in the hot central plasma core

Neoclassical electron heat conduction in tokamaks performed by the ions

International Nuclear Information System (INIS)

Ware, A.A.

1987-07-01

The increment to neoclassical ion heat conduction caused by electron collisions is shown to act like electron heat conduction since the energy is taken from and given back to the electrons at each diffusion step length. It can exceed electron neoclassical heat conduction by an order of magnitude

High Harmonic Fast Wave Heating Experiments on NSTX

International Nuclear Information System (INIS)

Wilson, J.R.; Bell, R.; Bitter, M.; Bonoli, P.

2000-01-01

A radio frequency (rf) system has been installed on the National Spherical Torus Experiment (NSTX) with the aim of heating the plasma and driving plasma current. The system consists of six rf transmitters, a twelve element antenna and associated transmission line components to distribute and couple the power from the transmitters to the antenna elements in a fashion to allow control of the antenna toroidal wavenumber spectrum. To date, power levels up to 3.85 MW have been applied to the NSTX plasmas. The frequency and spectrum of the rf waves has been selected to heat electrons via Landau damping and transit time magnetic pumping. The electron temperature has been observed to increase from 400 to 900 eV with little change in plasma density resulting in a plasma stored energy of 59 kJ and a toroidal beta, bT , =10% and bn = 2.7

High harmonic fast wave heating experiments on NSTX

International Nuclear Information System (INIS)

Wilson, J.R.; Bell, R.; Bitter, M.

2001-01-01

A radio frequency (rf) system has been installed on the National Spherical Torus Experiment (NSTX) with the aim of heating the plasma and driving plasma current. The system consists of six rf transmitters, a twelve element antenna and associated transmission line components to distribute and couple the power from the transmitters to the antenna elements in a fashion to allow control of the antenna toroidal wavenumber spectrum. To date, power levels up to 3.85 MW have been applied to the NSTX plasmas. The frequency and spectrum of the rf waves has been selected to heat electrons via Landau damping and transit time magnetic pumping. The electron temperature has been observed to increase from 400 to 900 eV with little change in plasma density resulting in a plasma stored energy of 59 kJ , a toroidal beta, β T =10% and a normalized beta, β n =2.7. (author)

Role of Density Gradient Driven Trapped Electron Modes in the H-Mode Inner Core with Electron Heating

Science.gov (United States)

Ernst, D.

2015-11-01

We present new experiments and nonlinear gyrokinetic simulations showing that density gradient driven TEM (DGTEM) turbulence dominates the inner core of H-Mode plasmas during strong electron heating. Thus α-heating may degrade inner core confinement in H-Mode plasmas with moderate density peaking. These DIII-D low torque quiescent H-mode experiments were designed to study DGTEM turbulence. Gyrokinetic simulations using GYRO (and GENE) closely match not only particle, energy, and momentum fluxes, but also density fluctuation spectra, with and without ECH. Adding 3.4 MW ECH doubles Te /Ti from 0.5 to 1.0, which halves the linear TEM critical density gradient, locally flattening the density profile. Density fluctuations from Doppler backscattering (DBS) intensify near ρ = 0.3 during ECH, displaying a band of coherent fluctuations with adjacent toroidal mode numbers. GYRO closely reproduces the DBS spectrum and its change in shape and intensity with ECH, identifying these as coherent TEMs. Prior to ECH, parallel flow shear lowers the effective nonlinear DGTEM critical density gradient 50%, but is negligible during ECH, when transport displays extreme stiffness in the density gradient. GS2 predictions show the DGTEM can be suppressed, to avoid degradation with electron heating, by broadening the current density profile to attain q0 >qmin > 1 . A related experiment in the same regime varied the electron temperature gradient in the outer half-radius (ρ ~ 0 . 65) using ECH, revealing spatially coherent 2D mode structures in the Te fluctuations measured by ECE imaging. Fourier analysis with modulated ECH finds a threshold in Te profile stiffness. Supported by the US DOE under DE-FC02-08ER54966 and DE-FC02-04ER54698.

Electron cyclotron resonance heating and current drive

Energy Technology Data Exchange (ETDEWEB)

Fidone, I.; Castejon, F.

1992-07-01

A brief summary of the theory and experiments on electron- cyclotron heating and current drive is presented. The general relativistic formulation of wave propagation and linear absorption is considered in some detail. The O-mode and the X-mode for normal and oblique propagation are investigated and illustrated by several examples. The experimental verification of the theory in T-10 and D- III-D is briefly discussed. Quasilinear evolution of the momentum distribution and related applications as, for instance, non linear wave, damping and current drive, are also considered for special cases of wave frequencies, polarization and propagation. In the concluding section we present the general formulation of the wave damping and current drive in the absence of electron trapping for arbitrary values of the wave frequency. (Author) 13 refs.

Electron - cyclotron resonance heating and current drive

International Nuclear Information System (INIS)

Fidone, I.; Castejon, F.

1992-01-01

A brief summary of the theory and experiments on electron- cyclotron heating and current drive is presented. The general relativistic formulation of wave propagation and linear absorption is considered in some detail. The O-mode and the X-mode for normal and oblique propagation are investigated and illustrated by several examples. The experimental verification of the theory in T-10 and D- III-D is briefly discussed. Quasilinear evolution of the momentum distribution and related applications as, for instance, non linear wave, damping and current drive, are also considered for special cases of wave frequencies, polarization and propagation. In the concluding section we present the general formulation of the wave damping and current drive in the absence of electron trapping for arbitrary values of the wave frequency. (Author) 13 refs

Electron-cyclotron resonance heating and current drive

International Nuclear Information System (INIS)

Filone, I.

1992-01-01

A brief summary of the theory and experiments on electron-cyclotron heating and current drive is presented. the general relativistic formulation of wave propagation and linear absorption is considered in some detail. The O-mode and the X-mode for normal and oblique propagation are investigated and illustrated by several examples. The experimental verification of the theory in T-10 and D-III-D is briefly discussed. Quasilinear evolution of the momentum distribution and related applications as, for instance, non linear wave damping and current drive, are also considered for special cases of wave frequencies, polarization and propagation. In the concluding section we present the general formulation of the wave damping and current drive in the absence of electron trapping for arbitrary values of the wave frequency. (author) 8 fig. 13 ref

Observations of temperature rise during electron cyclotron heating application in Proto-MPEX

Science.gov (United States)

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.

The capacitor banks for the text diagnostic neutral beam and electron cyclotron heating experiments

International Nuclear Information System (INIS)

Nelin, K.; Jagger, J.; Baker, M.; Ourou, A.; De Turk, P.

1986-01-01

The Texas Experimental Tokamak (TEXT) has been operational since November of 1980. Since that time, many experimental systems have been added to the machine. Currently, two major experiments are being added to compliment the diagnostics already online. These systems, the Diagnostic Neutral Beam (DNB) and the Electron Cyclotron Heating (ECH) experiments are described in separate papers. A set of five modular, bipolar capacitor banks are used to power both the DNB and the ECH. The total capacitance of the banks is 92μF. The stored energy is about 500kJ at+or-100kV. The banks are built as five identical, interchangeable modules. One module is adequate to run the DNB. Up to four banks are used to power the ECH. The banks are portable so that they can be moved to the open end of the laboratory for maintenance. This gives much better access for repair work and allows the experiments to continue to run with the remaining banks. Due to budgetary constraints, these banks were constructed in the most economical manner possible consistent with worker safety and long term reliability. The capacitors themselves are on loan from Los Alamos National Labs. They are rated at 1.85μF at 60kV. Our application requires that they be used in a series/parallel configuration with a peak voltage of 50kV each. This paper describes the electrical, mechanical and control design considerations required to achieve a working set of banks

Beam heating in solar flares - Electrons or protons?

International Nuclear Information System (INIS)

Brown, J.C.; Karlicky, M.; Mackinnon, A.L.; Van Den Oord, G.H.J.

1990-01-01

The current status of electron and proton beam models as candidates for the impulsive phase heating of solar flares is discussed in relation to observational constants and theoretical difficulties. It is concluded that, while the electron beam model for flare heating still faces theoretical and observational problems, the problems faced by low and high energy proton beam models are no less serious, and there are facets of proton models which have not yet been studied. At the present, the electron beam model remains the most viable and best developed of heating model candidates. 58 refs

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

CERN Document Server

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

2003-01-01

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

Electron distribution function in laser heated plasmas

International Nuclear Information System (INIS)

Fourkal, E.; Bychenkov, V. Yu.; Rozmus, W.; Sydora, R.; Kirkby, C.; Capjack, C. E.; Glenzer, S. H.; Baldis, H. A.

2001-01-01

A new electron distribution function has been found in laser heated homogeneous plasmas by an analytical solution to the kinetic equation and by particle simulations. The basic kinetic model describes inverse bremsstrahlung absorption and electron--electron collisions. The non-Maxwellian distribution function is comprised of a super-Gaussian bulk of slow electrons and a Maxwellian tail of energetic particles. The tails are heated due to electron--electron collisions and energy redistribution between superthermal particles and light absorbing slow electrons from the bulk of the distribution function. A practical fit is proposed to the new electron distribution function. Changes to the linear Landau damping of electron plasma waves are discussed. The first evidence for the existence of non-Maxwellian distribution functions has been found in the interpretation, which includes the new distribution function, of the Thomson scattering spectra in gold plasmas [Glenzer , Phys. Rev. Lett. 82, 97 (1999)

Analysis of performance degradation in an electron heating dominant H-mode plasma after ECRH termination in EAST

Science.gov (United States)

Du, Hongfei; Ding, Siye; Chen, Jiale; Wang, Yifeng; Lian, Hui; Xu, Guosheng; Zhai, Xuemei; Liu, Haiqing; Zang, Qing; Lyu, Bo; Duan, Yanmin; Qian, Jinping; Gong, Xianzu

2018-06-01

In recent EAST experiments, significant performance degradation accompanied by a decrease of internal inductance is observed in an electron heating dominant H-mode plasma after the electron cyclotron resonance heating termination. The lower hybrid wave (LHW) deposition and effective electron heat diffusivity are calculated to explain this phenomenon. Analysis shows that the changes of LHW heating deposition rather than the increase of transport are responsible for the significant decrease in energy confinement (). The reason why the confinement degradation occurred on a long time scale could be attributed to both good local energy confinement in the core and also the dependence of LHW deposition on the magnetic shear. The electron temperature profile shows weaker stiffness in near axis region where electron heating is dominant, compared to that in large radius region. Unstable electron modes from low to high k in the core plasma have been calculated in the linear GYRO simulations, which qualitatively agree with the experimental observation. This understanding of the plasma performance degradation mechanism will help to find ways of improving the global confinement in the radio-frequency dominant scenario in EAST.

Observation of the skin-like profiles of electron temperature and density of turbulently heated plasmas in the TRIAM-1 tokamak

International Nuclear Information System (INIS)

Hiraki, Naoji; Nakamura, Kazuo; Toi, Kazuo; Itoh, Satoshi

1980-01-01

The time evolution of electron temperature and density profiles are measured on the turbulent heating experiment in the TRIAM-1 tokamak. The skin-like profiles of electron temperature and density are observed just after the application of the pulsed electric field for turbulent heating. The width of the skin layer of the electron temperature profile is about 1 cm, and agrees well with the theoretical value. The above mentioned skin heating of electrons just after the heating pulse is also spectroscopically confirmed by the remarkable decrease of the volume emission of visible lines which is localized at the outer plasma region. (author)

Observation of the skin-like profiles of electron temperature and density of turbulently heated plasmas in the TRIAM-1 tokamak

Energy Technology Data Exchange (ETDEWEB)

Hiraki, N; Nakamura, K; Toi, K; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1980-07-01

The time evolution of electron temperature and density profiles are measured on the turbulent heating experiment in the TRIAM-1 tokamak. The skin-like profiles of electron temperature and density are observed just after the application of the pulsed electric field for turbulent heating. The width of the skin layer of the electron temperature profile is about 1 cm, and agrees well with the theoretical value. The above mentioned skin heating of electrons just after the heating pulse is also spectroscopically confirmed by the remarkable decrease of the volume emission of visible lines which is localized at the outer plasma region.

Electron heating in low pressure capacitive discharges revisited

Energy Technology Data Exchange (ETDEWEB)

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J. [Department of Electrical Engineering and Computer Sciences University of California, Berkeley, California 94720 (United States)

2014-12-15

The electrons in capacitively coupled plasmas (CCPs) absorb energy via ohmic heating due to electron-neutral collisions and stochastic heating due to momentum transfer from high voltage moving sheaths. We use Particle-in-Cell (PIC) simulations to explore these heating mechanisms and to compare the PIC results with available theories on ohmic and stochastic heating. The PIC results for ohmic heating show good agreement with the ohmic heating calculation of Lafleur et al. [Phys. Plasmas 20, 124503 (2013)]. The PIC results for stochastic heating in low pressure CCPs with collisionless sheaths show good agreement with the stochastic heating model of Kaganovich et al. [IEEE Trans. Plasma Sci. 34, 696 (2006)], which revises the hard wall asymptotic model of Lieberman [IEEE Trans. Plasma Sci. 16, 638 (1988)] by taking current continuity and bulk oscillation into account.

Electron heating in low pressure capacitive discharges revisited

International Nuclear Information System (INIS)

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

2014-01-01

The electrons in capacitively coupled plasmas (CCPs) absorb energy via ohmic heating due to electron-neutral collisions and stochastic heating due to momentum transfer from high voltage moving sheaths. We use Particle-in-Cell (PIC) simulations to explore these heating mechanisms and to compare the PIC results with available theories on ohmic and stochastic heating. The PIC results for ohmic heating show good agreement with the ohmic heating calculation of Lafleur et al. [Phys. Plasmas 20, 124503 (2013)]. The PIC results for stochastic heating in low pressure CCPs with collisionless sheaths show good agreement with the stochastic heating model of Kaganovich et al. [IEEE Trans. Plasma Sci. 34, 696 (2006)], which revises the hard wall asymptotic model of Lieberman [IEEE Trans. Plasma Sci. 16, 638 (1988)] by taking current continuity and bulk oscillation into account

Electron heating in low pressure capacitive discharges revisited

Science.gov (United States)

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

2014-12-01

The electrons in capacitively coupled plasmas (CCPs) absorb energy via ohmic heating due to electron-neutral collisions and stochastic heating due to momentum transfer from high voltage moving sheaths. We use Particle-in-Cell (PIC) simulations to explore these heating mechanisms and to compare the PIC results with available theories on ohmic and stochastic heating. The PIC results for ohmic heating show good agreement with the ohmic heating calculation of Lafleur et al. [Phys. Plasmas 20, 124503 (2013)]. The PIC results for stochastic heating in low pressure CCPs with collisionless sheaths show good agreement with the stochastic heating model of Kaganovich et al. [IEEE Trans. Plasma Sci. 34, 696 (2006)], which revises the hard wall asymptotic model of Lieberman [IEEE Trans. Plasma Sci. 16, 638 (1988)] by taking current continuity and bulk oscillation into account.

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

International Nuclear Information System (INIS)

Stange, Torsten

2014-01-01

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

Modeling ambipolar potential formation due to ICRF heating effects on electrons

International Nuclear Information System (INIS)

Johnson, J.W.; Callen, J.D.; Hershkowitz, N.

1985-08-01

A mechanism for the potential bump observed near the region of ICRF heating in the endplugs of the Phaedrus tandem mirror experiment is investigated by numerical simulation of electron orbits in a simple mirror geometry. Given initial magnetic and ambipolar potential wells that trap the electrons, the ''near field'' parallel electric field E-tilde/sub z/e/sup -iωt/, which is localized near and due to the ICRF heating, tends to eject electrons from the region where E-tilde/sub z/ is nonzero. This depletion of the local electron population causes a local increase in the ambipolar potential. The rate at which the electrons are ejected, (dn/dt), is calculated from the electron orbit computation for a given potential well depth. The rate at which passing particles ''fill in'' the potential well can also be calculated. An estimate of how large the bump in the ambipolar potential becomes is obtained by finding the well depth at which (dn/dt) approximately equals the ''filling'' rate. For Phaedrus parameters (n 0 approx. = 4.0 x 10 12 cm -3 , T/sub e/ = 20 eV, E-tilde/sub z/ approx. = 1.0 V/cm) the electron pumping rate balances the ''filling'' rate at a potential well depth of approximately 40 V, consistent with experimental results

Plasma heating in the TM-3 Tokamak at electron-cyclotron resonance with magnetic fields up to 25 ke

International Nuclear Information System (INIS)

Alikaev, V.V.; Bobrovskii, G.A.; Poznyak, V.I.; Razumova, K.A.; Sannikov, V.V.; Sokolov, Yu.A.; Shmarin, A.A.

Experiments were conducted in heating plasma at electron-cyclotron resonance (ECR) with longitudinal magnetic fields up to 25 ke. It was shown by the aid of laser diagnosis that the temperature of the basic component of the electrons increases in accordance with the classical mechanism of heating at ECR in the process of electron-cyclotron heating (ECH). The distribution of the temperature of electrons with respect to radius was measured. The relationship of energetic lifetime in the Tokamak and electron temperature was obtained and the magnitude of energetic lifetime of accelerated electrons in the function of their energy was estimated. The value β/sub tau/ approximately equal to 2.2 was obtained by the aid of ECH in a regime with small discharge currents

Ion Thermalization and Electron Heating across Quasi-Perpendicular Shocks Observed by the MMS Mission

Science.gov (United States)

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.

High power plasma heating experiments on the Proto-MPEX facility

Science.gov (United States)

Bigelow, T. S.; Beers, C. J.; Biewer, T. M.; Caneses, J. F.; Caughman, J. B. O.; Diem, S. J.; Goulding, R. H.; Green, D. L.; Kafle, N.; Rapp, J.; Showers, M. A.

2017-10-01

Work is underway to maximize the power delivered to the plasma that is available from heating sources installed on the Prototype Materials Plasma Exposure eXperiment (Proto-MPEX) at ORNL. Proto-MPEX is a linear device that has a >100 kW, 13.56 MHz helicon plasma generator available and is intended for material sample exposure to plasmas. Additional plasma heating systems include a 10 kW 18 GHz electron cyclotron heating (ECH) system, a 25 kW 8 MHz ion cyclotron heating ICH system, and a 200 kW 28 GHz electron Bernstein wave (EBW) and ECH system. Most of the heating systems have relatively good power transmission efficiency, however, the 28 GHz EBW system has a lower efficiency owing to stringent requirements on the microwave launch characteristics for EBW coupling combined with the lower output mode purity of the early-model gyrotron in use and its compact mode converter system. A goal for the Proto-MPEX is to have a combined heating power of 200 kW injected into the plasma. Infrared emission diagnostics of the target plate combined with Thomson Scattering, Langmuir probe, and energy analyzer measurements near the target are utilized to characterize the plasmas and coupling efficiency of the heating systems. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC-05-00OR22725.

Heat- and radiation-resistant scintillator for electron microscopes

International Nuclear Information System (INIS)

Kosov, A.V.; Petrov, S.A.; Puzyr', A.P.; Chetvergov, N.A.

1987-01-01

The use of a scintillator consisting of a single crystal of bismuth orthogermanate, which has high heat and radiation resistance, in REM-100, REM-200, and REM-100U electron microscopes is described. A study of the heat and radiation stabilities of single crystals of bismuth orthogermanate (Bi 4 Ge 3 O 12 ) has shown that they withstood multiple electron-beam heating redness (T ∼ 800 0 C) without changes in their properties

Solutions to mitigate heat loads due to electrons on sensitive components of ITER HNB beamlines

Energy Technology Data Exchange (ETDEWEB)

Sartori, Emanuele, E-mail: emanuele.sartori@gmail.com [Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova (Italy); Veltri, Pierluigi; Dalla Palma, Mauro; Agostinetti, Piero [Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova (Italy); Hemsworth, Ronald; Singh, Mahendrajit [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Serianni, Gianluigi [Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova (Italy)

2016-11-01

Highlights: • Energetic electrons leaking out of the ITER HNB accelerator are simulated. • Electrons generated along the ITER HNB beamline are simulated. • Heat loads and heat load maps on cryopumps are calculated for ITER HNB and test facility. • Protection solutions that will be installed are presented and their effect discussed. - Abstract: The operation of neutral beam injectors for plasma heating and current drive in a fusion device provides challenges in the thermal management of beamline components. Sensitive components such as the cryogenic pumps at beamline periphery shall be protected from the heat flux due to stray electrons. These are emitted by the negative ion accelerator or generated along the beamline by interaction of fast electrons, ions or atoms with background gas and surfaces. In this article the case of the ITER Heating Neutral Beam (HNB) and its test facility MITICA is discussed, for which the beam parameters and the required pulse length of one hour is a major leap forward with respect to the present experience with neutral beam systems. The engineering solutions adopted for effective cryopump protection against the heat load from electrons are described. The use of three-dimensional numerical simulations of particle trajectories in the complex geometry of the beamline was needed for the quantitative estimations of the heat loads. The presented solutions were optimized to minimize the impact on gas pumping and on the functionality of other components.

Electron Heating at Kinetic Scales in Magnetosheath Turbulence

International Nuclear Information System (INIS)

Chasapis, Alexandros; Matthaeus, W. H.; Parashar, T. N.; LeContel, O.; Retinò, A.; Breuillard, H.; Khotyaintsev, Y.; Vaivads, A.; Eriksson, E.; Lavraud, B.; Moore, T. E.; Burch, J. L.; Torbert, R. B.; Chutter, M.; Needell, J.; Lindqvist, P.-A.; Marklund, G.; Ergun, R. E.; Goodrich, K. A.; Wilder, F. D.

2017-01-01

We present a statistical study of coherent structures at kinetic scales, using data from the Magnetospheric Multiscale mission in the Earth’s magnetosheath. We implemented the multi-spacecraft partial variance of increments (PVI) technique to detect these structures, which are associated with intermittency at kinetic scales. We examine the properties of the electron heating occurring within such structures. We find that, statistically, structures with a high PVI index are regions of significant electron heating. We also focus on one such structure, a current sheet, which shows some signatures consistent with magnetic reconnection. Strong parallel electron heating coincides with whistler emissions at the edges of the current sheet.

Electron heating and energy inventory during asymmetric reconnection in a laboratory plasma

Science.gov (United States)

Yoo, J.; Na, B.; Jara-Almonte, J.; Yamada, M.; Ji, H.; Roytershteyn, V.; Argall, M. R.; Fox, W.; Chen, L. J.

2017-12-01

Electron heating and the energy inventory during asymmetric reconnection are studied in the Magnetic Reconnection Experiment (MRX) [1]. In this plasma, the density ratio is about 8 across the current sheet. Typical features of asymmetric reconnection such as the large density gradients near the low-density-side separatrices, asymmetric in-plane electric field, and bipolar out-of-plane magnetic field are observed. Unlike the symmetric case [2], electrons are also heated near the low-density-side separatrices. The measured parallel electric field may explain the observed electron heating. Although large fluctuations driven by lower-hybrid drift instabilities are also observed near the low-density-side separatrices, laboratory measurements and numerical simulations reported here suggest that they do not play a major role in electron energization. The average electron temperature increase in the exhaust region is proportional to the incoming magnetic energy per an electron/ion pair but exceeds the scaling of the previous space observations [3]. This discrepancy is explained by differences in the boundary condition and system size. The profile of electron energy gain from the electric field shows that there is additional electron energy gain associated with the electron diamagnetic current besides a large energy gain near the X-line. This additional energy gain increases electron enthalpy, not the electron temperature. Finally, a quantitative analysis of the energy inventory during asymmetric reconnection is conducted. Unlike the symmetric case where the ion energy gain is about twice more than the electron energy gain [4], electrons and ions obtain a similar amount of energy during asymmetric reconnection. [1] J. Yoo et al., accepted for a publication in J. Geophys. Res. [2] J. Yoo et al., Phys. Plasmas 21, 055706 (2014). [3] T. Phan et al., Geophys. Res. Lett. 40, 4475 (2013). [4] M. Yamada et al., Nat. Comms. 5, 4474 (2014).

THE ELECTRONIC COURSE OF HEAT AND MASS TRANSFER

Directory of Open Access Journals (Sweden)

Alexander P. Solodov

2013-01-01

Full Text Available The Electronic course of heat and mass transfer in power engineering is presented containing the full Electronic book as the structured hypertext document, the full set of Mathcad-documents with the whole set of educative computer models of heat and mass transfer, the computer labs, and selected educational presentations. 

HEATING AND CURRENT DRIVE BY ELECTRON CYCLOTRON WAVES

International Nuclear Information System (INIS)

Prater, R.

2003-01-01

OAK-B135 The physics model of electron cyclotron heating (ECH) and current drive (ECCD) is becoming well validated through systematic comparisons of theory and experiment. This work has shown that ECH and ECCD can be highly localized and robustly controlled in toroidal plasma confinement systems, leading to applications including stabilization of magnetohydrodynamic (MHD) instabilities like neoclassical tearing modes, control and sustainment of desired profiles of current density and plasma pressure, and studies of localized transport in laboratory plasmas. The experimental work was supported by a broad base of theory based on first principles which is now well encapsulated in linear ray tracing codes describing wave propagation, absorption, and current drive and in fully relativistic quasilinear Fokker-Planck codes describing in detail the response of the electrons to the energy transferred from the wave. The subtle balance between wave-induced diffusion and Coulomb relaxation in velocity space provides an understanding of the effects of trapping of current-carrying electrons in the magnetic well. Strong quasilinear effects and radial transport of electrons, which may broaden the driven current profile, have also been observed under some conditions and appear to be consistent with theory, but in large devices these are usually insignificant. The agreement of theory and experiment, the wide range of established applications, and the technical advantages of ECH support the application of ECH in next-step tokamaks and stellarators

Antenna loading and electron heating experiments of ICRF wave in TNT-A tokamak

International Nuclear Information System (INIS)

Shinohara, Shunjiro; Asakura, Nobuyuki; Naito, Masahiro; Miyamoto, Kenro

1984-01-01

Antenna loading resistance and electron heating effects of ICRF wave were investigated in TNT-A tokamak. Lodaing resistance increased with the mean plasma density and decreased with the input power. The effect of the distance between the plasma and antenna surface on loading resistance was studied and had good agreements with the calculated results. The increase in the soft Xray emissivity was larger in the presence of ion-ion hybrid and/or ion cyclotron resonance layer in the plasma than that in the absence of them. With the absorbed power up to two times of the ohmic power, the central electron temperature increased by 20%, the soft Xray emissivity increased by 80% and the mean plasma density decreased by 10%, while the total radiation loss increased slightly (by 15%). (author)

Three-wave interaction during electron cyclotron resonance heating and current drive

DEFF Research Database (Denmark)

Nielsen, Stefan Kragh; Jacobsen, Asger Schou; Hansen, Søren Kjer

2016-01-01

Non-linear wave-wave interactions in fusion plasmas, such as the parametric decay instability (PDI) of gyrotron radiation, can potentially hamper the use of microwave diagnostics. Here we report on anomalous scattering in the ASDEX Upgrade tokamak during electron cyclotron resonance heating...... experiments. The observations can be linked to parametric decay of the gyrotron radiation at the second harmonic upper hybrid resonance layer....

Space chamber experiments of ohmic heating by high power microwave from the solar power satellite

Energy Technology Data Exchange (ETDEWEB)

Kaya, N.; Matsumoto, H.

1981-12-01

It is quantitatively predicted that a high power microwave from the Solar Power Satellite (SPS) nonlinearly interacts with the ionospheric plasma. The possible nonlinear interactions are ohmic heating, self-focusing and parametric instabilities. A rocket experiment called MINIX (Microwave-Ionosphere Nonlinear Interaction Experiment) has been attempted to examine these effects, but is note reported here. In parallel to the rocket experiment, a laboratory experiment in a space plasma simulation chamber has been carried out in order to examine ohmic heating in detail and to develop a system of the rocket experiment. Interesting results were observed and these results were utilized to revise the system of the rocket experiments. A significant microwave heating of plasma up to 150% temperature increase was observed with little electron density decrease. It was shown that the temperature increase is not due to the RF breakdown but to the ohmic heating in the simulated ionospheric plasma. These microwave effects have to be taken into account in the SPS Project in the future.

Analysis of core plasma heating and ignition by relativistic electrons

International Nuclear Information System (INIS)

Nakao, Y.

2002-01-01

Clarification of the pre-compressed plasma heating by fast electrons produced by relativistic laser-plasma interaction is one of the most important issues of the fast ignition scheme in ICF. On the basis of overall calculations including the heating process, both by relativistic hot electrons and alpha-particles, and the hydrodynamic evolution of bulk plasma, we examine the feature of core plasma heating and the possibility of ignition. The deposition of the electron energy via long-range collective mode, i.e. Langmuir wave excitation, is shown to be comparable to that through binary electron-electron collisions; the calculation neglecting the wave excitation considerably underestimates the core plasma heating. The ignition condition is also shown in terms of the intensity I(h) and temperature T(h) of hot electrons. It is found that I(h) required for ignition increases in proportion to T(h). For efficiently achieving the fast ignition, electron beams with relatively 'low' energy (e.g.T(h) below 1 MeV) are desirable. (author)

A MEMS-based heating holder for the direct imaging of simultaneous in-situ heating and biasing experiments in scanning/transmission electron microscopes.

Science.gov (United States)

Mele, Luigi; Konings, Stan; Dona, Pleun; Evertz, Francis; Mitterbauer, Christoph; Faber, Pybe; Schampers, Ruud; Jinschek, Joerg R

2016-04-01

The introduction of scanning/transmission electron microscopes (S/TEM) with sub-Angstrom resolution as well as fast and sensitive detection solutions support direct observation of dynamic phenomena in-situ at the atomic scale. Thereby, in-situ specimen holders play a crucial role: accurate control of the applied in-situ stimulus on the nanostructure combined with the overall system stability to assure atomic resolution are paramount for a successful in-situ S/TEM experiment. For those reasons, MEMS-based TEM sample holders are becoming one of the preferred choices, also enabling a high precision in measurements of the in-situ parameter for more reproducible data. A newly developed MEMS-based microheater is presented in combination with the new NanoEx™-i/v TEM sample holder. The concept is built on a four-point probe temperature measurement approach allowing active, accurate local temperature control as well as calorimetry. In this paper, it is shown that it provides high temperature stability up to 1,300°C with a peak temperature of 1,500°C (also working accurately in gaseous environments), high temperature measurement accuracy (in-situ S/TEM imaging experiments, but also elemental mapping at elevated temperatures using energy-dispersive X-ray spectroscopy (EDS). Moreover, it has the unique capability to enable simultaneous heating and biasing experiments. © 2016 Wiley Periodicals, Inc.

Stabilization of electron-scale turbulence by electron density gradient in national spherical torus experiment

Energy Technology Data Exchange (ETDEWEB)

Ruiz Ruiz, J.; White, A. E. [MIT-Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Ren, Y.; Guttenfelder, W.; Kaye, S. M.; Leblanc, B. P.; Mazzucato, E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Lee, K. C. [National Fusion Research Institute, Daejeon (Korea, Republic of); Domier, C. W. [University of California at Davis, Davis, California 95616 (United States); Smith, D. R. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yuh, H. [Nova Photonics, Inc., Princeton, New Jersey 08540 (United States)

2015-12-15

Theory and experiments have shown that electron temperature gradient (ETG) turbulence on the electron gyro-scale, k{sub ⊥}ρ{sub e} ≲ 1, can be responsible for anomalous electron thermal transport in NSTX. Electron scale (high-k) turbulence is diagnosed in NSTX with a high-k microwave scattering system [D. R. Smith et al., Rev. Sci. Instrum. 79, 123501 (2008)]. Here we report on stabilization effects of the electron density gradient on electron-scale density fluctuations in a set of neutral beam injection heated H-mode plasmas. We found that the absence of high-k density fluctuations from measurements is correlated with large equilibrium density gradient, which is shown to be consistent with linear stabilization of ETG modes due to the density gradient using the analytical ETG linear threshold in F. Jenko et al. [Phys. Plasmas 8, 4096 (2001)] and linear gyrokinetic simulations with GS2 [M. Kotschenreuther et al., Comput. Phys. Commun. 88, 128 (1995)]. We also found that the observed power of electron-scale turbulence (when it exists) is anti-correlated with the equilibrium density gradient, suggesting density gradient as a nonlinear stabilizing mechanism. Higher density gradients give rise to lower values of the plasma frame frequency, calculated based on the Doppler shift of the measured density fluctuations. Linear gyrokinetic simulations show that higher values of the electron density gradient reduce the value of the real frequency, in agreement with experimental observation. Nonlinear electron-scale gyrokinetic simulations show that high electron density gradient reduces electron heat flux and stiffness, and increases the ETG nonlinear threshold, consistent with experimental observations.

The effect of electron cyclotron heating on density fluctuations at ion and electron scales in ITER baseline scenario discharges on the DIII-D tokamak

Science.gov (United States)

Marinoni, A.; Pinsker, R. I.; Porkolab, M.; Rost, J. C.; Davis, E. M.; Burrell, K. H.; Candy, J.; Staebler, G. M.; Grierson, B. A.; McKee, G. R.; Rhodes, T. L.; The DIII-D Team

2017-12-01

Experiments simulating the ITER baseline scenario on the DIII-D tokamak show that torque-free pure electron heating, when coupled to plasmas subject to a net co-current beam torque, affects density fluctuations at electron scales on a sub-confinement time scale, whereas fluctuations at ion scales change only after profiles have evolved to a new stationary state. Modifications to the density fluctuations measured by the phase contrast imaging diagnostic (PCI) are assessed by analyzing the time evolution following the switch-off of electron cyclotron heating (ECH), thus going from mixed beam/ECH to pure neutral beam heating at fixed βN . Within 20 ms after turning off ECH, the intensity of fluctuations is observed to increase at frequencies higher than 200 kHz in contrast, fluctuations at lower frequency are seen to decrease in intensity on a longer time scale, after other equilibrium quantities have evolved. Non-linear gyro-kinetic modeling at ion and electron scales scales suggest that, while the low frequency response of the diagnostic is consistent with the dominant ITG modes being weakened by the slow-time increase in flow shear, the high frequency response is due to prompt changes to the electron temperature profile that enhance electron modes and generate a larger heat flux and an inward particle pinch. These results suggest that electron heated regimes in ITER will feature multi-scale fluctuations that might affect fusion performance via modifications to profiles.

High frequency ion Bernstein wave heating experiment on JIPP T-IIU tokamak

International Nuclear Information System (INIS)

Seki, T.; Kumazawa, R.; Watari, T.

1992-08-01

An experiment in a new regime of ion Bernstein wave (IBW) heating has been carried out using 130 MHz high power transmitters in the JIPP T-IIU tokamak. The heating regime utilized the IBW branch between the 3rd and 4th harmonics of the hydrogen ion cyclotron frequencies. This harmonic number is the highest among those used in the IBW experiments ever conducted. The net radio-frequency (RF) power injected into the plasma is around 400 kW, limited by the transmitter output power. Core heating of ions and electrons was confirmed in the experiment and density profile peaking was found to feature the IBW heating (IBWH). The peaking of the density profile was also found when IBW was applied to the neutral beam injection heated discharges. An analysis by use of a transport code with these experimental data indicates that the particle confinement should be improved in the plasma core region on the application of IBWH. It is also found that the ion energy distribution function observed during IBWH has less high energy tail than those in conventional ion cyclotron range of frequency heating regimes. The observed IBWH-produced ion energy distribution function is in a reasonable agreement with the calculation based on the quasi-linear RF diffusion / Fokker-Planck model. (author)

Investigation of electron heating in laser-plasma interaction

Directory of Open Access Journals (Sweden)

A Parvazian

2013-03-01

Full Text Available  In this paper, stimulated Raman scattering (SRS and electron heating in laser plasma propagating along the plasma fusion is investigated by particle-in cell simulation. Applying an external magnetic field to plasma, production of whistler waves and electron heating associated with whistler waves in the direction perpendicular to external magnetic field was observed in this simulation. The plasma waves with low phase velocities, generated in backward-SRS and dominateing initially in time and space, accelerated the backward electrons by trapping them. Then these electrons promoted to higher energies by the forward-SRS plasma waves with high phase velocities. This tow-stage electron acceleration is more efficient due to the coexistence of these two instabilities.

Investigation of electron heating in laser-plasma interaction

International Nuclear Information System (INIS)

Parvazian, A.; Haji Sharifi, K.

2013-01-01

In this paper, stimulated Raman scattering and electron heating in laser plasma propagating along the plasma fusion is investigated by particle-in cell simulation. Applying an external magnetic field to plasma, production of whistler waves and electron heating associated with whistler waves in the direction perpendicular to external magnetic field was observed in this simulation. The plasma waves with low phase velocities, generated in backward-stimulated Raman scattering and dominating initially in time and space, accelerated the backward electrons by trapping them. Then these electrons promoted to higher energies by the forward-stimulated Raman scattering plasma waves with high phase velocities. This two-stage electron acceleration is more efficient due to the coexistence of these two instabilities.

Heat load of a P-doped GaAs photocathode in SRF electron gun

International Nuclear Information System (INIS)

Wang, E.; Ben-Zvi, I.; Kewisch, J.; Burrill, A.; Rao, T.; Wu, Q.; Jain, A.; Gupta, R.; Holmes, D.

2010-01-01

Many efforts were made over the last decades to develop a better polarized electron source for the high energy physics. Several laboratories operate DC guns with the Gallium-Arsenide photo-cathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved using a Superconducting RF electron gun, which delivers beams of higher brightness than DC guns does, because the field gradient at the cathode is higher. SRF guns with metal cathodes and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since the cathode will be normal conducting, the problem about the heat load stemming from the cathode arises. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and the verification by measuring the quality factor of the gun with and without cathode.

Tokamak electron heat transport by direct numerical simulation of small scale turbulence

International Nuclear Information System (INIS)

Labit, B.

2002-10-01

In a fusion machine, understanding plasma turbulence, which causes a degradation of the measured energy confinement time, would constitute a major progress in this field. In tokamaks, the measured ion and electron thermal conductivities are of comparable magnitude. The possible sources of turbulence are the temperature and density gradients occurring in a fusion plasma. Whereas the heat losses in the ion channel are reasonably well understood, the origin of the electron losses is more uncertain. In addition to the radial velocity associated to the fluctuations of the electric field, electrons are more affected than ions by the magnetic field fluctuations. In experiments, the confinement time can be conveniently expressed in terms of dimensionless parameters. Although still somewhat too imprecise, these scaling laws exhibit strong dependencies on the normalized pressure β or the normalized Larmor radius, ρ * . The present thesis assesses whether a tridimensional, electromagnetic, nonlinear fluid model of plasma turbulence driven by a specific instability can reproduce the dependence of the experimental electron heat losses on the dimensionless parameters β and ρ * . The investigated interchange instability is the Electron Temperature Gradient driven one (ETG). The model is built by using the set of Braginskii equations. The developed simulation code is global in the sense that a fixed heat flux is imposed at the inner boundary, leaving the gradients free to evolve. From the nonlinear simulations, we have put in light three characteristics for the ETG turbulence: the turbulent transport is essentially electrostatic; the potential and pressure fluctuations form radially elongated cells called streamers; the transport level is very low compared to the experimental values. The thermal transport dependence study has shown a very small role of the normalized pressure, which is in contradiction with the Ohkama's formula. On the other hand, the crucial role of the

Real time plasma control experiments using the JET auxiliary plasma heating systems as the actuator

International Nuclear Information System (INIS)

Zornig, N.H.

1999-01-01

The role of the Real Time Power Control system (RTPC) in the Joint European Torus (JET) is described in depth. The modes of operation are discussed in detail and a number of successful experiments are described. These experiments prove that RTPC can be used for a wide range of experiments, including: (1) Feedback control of plasma parameters in real time using Ion Cyclotron Resonance Heating (ICRH) or Neutral Beam Heating (NBH) as the actuator in various JET operating regimes. It is demonstrated that in a multi-parameter space it is not sufficient to control one global plasma parameter in order to avoid performance limiting events. (2) Restricting neutron production and subsequent machine activation resulting from high performance pulses. (3) The simulation of α-particle heating effects in a DT-plasma in a D-only plasma. The heating properties of α-particles are simulated using ICRH-power, which is adjusted in real time. The simulation of α-particle heating in JET allows the effects of a change in isotopic mass to be separated from α-particle heating. However, the change in isotopic mass of the plasma ions appears to affect not only the global energy confinement time (τ E ) but also other parameters such as the electron temperature at the plasma edge. This also affects τ E , making it difficult to make a conclusive statement about any isotopic effect. (4) For future JET experiments a scheme has been designed which simulates the behaviour of a fusion reactor experimentally. The design parameters of the International Thermonuclear Experimental Reactor (ITER) are used. In the proposed scheme the most relevant dimensionless plasma parameters are similar in JET and ITER. It is also shown how the amount of heating may be simulated in real time by RTPC using the electron temperature and density as input parameters. The results of two demonstration experiments are presented. (author)

Improvements in electron beam monitoring and heat flux flatness at the JUDITH 2-facility

Energy Technology Data Exchange (ETDEWEB)

Weber, Thomas, E-mail: weber.th@gmx.de [Forschungszentrum Jülich, Institute of Energy and Climate Research, Jülich (Germany); Bürger, Andreas; Dominiczak, Karsten; Pintsuk, Gerald [Forschungszentrum Jülich, Institute of Energy and Climate Research, Jülich (Germany); Banetta, Stefano; Bellin, Boris [Fusion for Energy, Josep Pla, 2, Torres Diagonal Litoral B3, 08019 Barcelona (Spain); Mitteau, Raphael; Eaton, Russell [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France)

2015-10-15

Highlights: • Monitoring of the much faster electron beam motion by IR camera through a synchronized frame triggering. • Estimation of the heat flux generated by electron beam guns based on calorimetry and FEM simulations. • Consideration of the inclined electron beam loading of rectangular-shaped objects. - Abstract: Three beryllium-armoured small-scale mock-ups and one semi-prototype for the ITER first wall were tested by the electron beam facility JUDITH 2 at Forschungszentrum Jülich. Both testing campaigns with cyclic loads up to 2.5 MW/m{sup 2} are carried out in compliance with the extensive quality and management specifications of ITER Organization (IO) and Fusion for Energy (F4E). Several dedicated calibration experiments were performed before the actual testing in order to fulfil the testing requirements and tolerances. These quality requests have been the motivation for several experimental setup improvements. The most relevant results of these activities, being the electron beam monitoring and the heat flux flatness verification, will be presented.

Improvements in electron beam monitoring and heat flux flatness at the JUDITH 2-facility

International Nuclear Information System (INIS)

Weber, Thomas; Bürger, Andreas; Dominiczak, Karsten; Pintsuk, Gerald; Banetta, Stefano; Bellin, Boris; Mitteau, Raphael; Eaton, Russell

2015-01-01

Highlights: • Monitoring of the much faster electron beam motion by IR camera through a synchronized frame triggering. • Estimation of the heat flux generated by electron beam guns based on calorimetry and FEM simulations. • Consideration of the inclined electron beam loading of rectangular-shaped objects. - Abstract: Three beryllium-armoured small-scale mock-ups and one semi-prototype for the ITER first wall were tested by the electron beam facility JUDITH 2 at Forschungszentrum Jülich. Both testing campaigns with cyclic loads up to 2.5 MW/m"2 are carried out in compliance with the extensive quality and management specifications of ITER Organization (IO) and Fusion for Energy (F4E). Several dedicated calibration experiments were performed before the actual testing in order to fulfil the testing requirements and tolerances. These quality requests have been the motivation for several experimental setup improvements. The most relevant results of these activities, being the electron beam monitoring and the heat flux flatness verification, will be presented.

Comparison of transient electron heat transport in LHD helical and JT-60U tokamak plasmas

International Nuclear Information System (INIS)

Inagaki, S.; Ida, K.; Tamura, N.; Shimozuma, T.; Kubo, S.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Ohkubo, K.; Takenaga, H.; Isayama, A.; Takizuka, T.; Kamada, Y.; Miura, Y.

2005-01-01

Transient transport experiments are performed in plasmas with and without Internal Transport Barrier (ITB) on LHD and JT-60U. The dependence of χ e on electron temperature, T e , and electron temperature gradient, ∇T e , is analyzed by an empirical non-linear heat transport model. In plasmas without ITB, two different types of non-linearity of the electron heat transport are observed from cold/heat pulse propagation. The χ e depends on T e and ∇T e in JT-60U, while the ∇T e dependence is weak in LHD. Inside the ITB region, there is no or weak ∇T e dependence both in LHD and JT-60U. A cold pulse growing driven by the negative T e dependence of χ e is observed inside the ITB region (LHD) and near the boundary of the ITB region (JT-60U). (author)

Experiments on nucleate boiling heat transfer with a highly-wetting dielectric fluid

International Nuclear Information System (INIS)

You, S.M.; Simon, T.W.; Bar-Cohen, A.

1990-01-01

This paper reports on experiments on pool boiling heat transfer in an electronic cooling fluid (Fluorinert, FC-72) that were conducted using a 0.51 mm diameter cylindrical heater. The effects of pressure, subcooling and dissolved gas content on nucleate boiling heat transfer are investigated. When boiling with dissolved gas in the bulk fluid, the fluid in the vicinity of the heating element appears to be liberated of dissolved gas by boiling. Thus, boiling under these conditions appears to be similar to subcooled boiling without dissolved gas. Nucleate boiling hysteresis is observed for subcooled and gassy-subcooled situations

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

Science.gov (United States)

Testa, D.; Albergante, M.

2012-08-01

In the so-called ‘alpha-heating’ experiment performed on the JET tokamak during the deuterium-tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s. Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code. We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the so

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

International Nuclear Information System (INIS)

Testa, D.; Albergante, M.

2012-01-01

In the so-called ‘alpha-heating’ experiment performed on the JET tokamak during the deuterium–tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s. Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code. We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the

ICRF heating experiments in JFT-2 tokamak

International Nuclear Information System (INIS)

Matsumoto, Hiroshi

1986-01-01

This is an experimental study of ICRF heating on JFT-2 Tokamak in Japan Atomic Energy Research Institute. In this study, we first clarified physical and engineering problems of ICRF heating of tokamak plasma. Next, we optimized the design of the ICRF heating system, and the plasma parameters for the heating. Finally, we could demonstrate a high efficiency of this additional heating method by launching RF power which is two or three times as large as an ohmic input power to a plasma. And we achieved following things. (1) We optimized a design of an antenna, and we improved a durability of the system for high voltage. With the result that we achieved the maximum power density on an antenna. (2) We demonstrated that electron heating regime and ion heating regime can be easily accessed by controlling plasma parameters. Also we found the optimum heating conditions in each heating regime. (3) We experimentally clarified the production mechanism of impurities during ICRF heating. We could reduce the influx of metal impurity ions to a plasma by employing low z materials for limiters and antenna shields. Consequently, we improved a heating efficiency of electrons. Next, we studied a power balance of plasma during ICRF heating, and we could compare heating characteristics of ICRF with other additional heatings on JFT-2. (author)

Fast-wave ICRF minority-regime heating experiments on the Tore Supra tokamak

Energy Technology Data Exchange (ETDEWEB)

Agarici, G; Beaumont, B; Becoulet, A; Kuus, H; Saoutic, B; Martin, G [Association Euratom-CEA, Centre d` Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (FR). Dept. de Recherches sur la Fusion Controlee; Shepard, T D; Haste, G R; Baity, F W [Oak Ridge National Lab., TN (US); Evans, T E [General Atomics, San Diego, CA (US)

1992-12-31

Up to 4 MW of rf power at 57 MHz has been coupled to Ohmic target plasmas during the first ICRF heating experiments on Tore Supra. A total of 12 MW of rf power will ultimately be available from six tetrode amplifiers and will be coupled to the plasmas using three ORNL/CEA-designed resonant double-loop antennas. During these first experiments, two antennas were used, with one or two energized at a time. The antenna loading with plasma was observed to be well over an order of magnitude greater than that without plasma. In addition, one kilo-electron-volt of electron heating, significant minority nonthermal ions, and significant increases in diamagnetic stored energy were observed. A comparison of in-phase and out-of-phase antenna operation showed the same increase in stored energy, less radiated power, and a larger drop in loop voltage for out-of-phase operation. Confinement scaling agrees with the ITER scaling law.

Anomalous Behavior of Electronic Heat Capacity of Strongly Correlated Iron Monosilicide

Science.gov (United States)

Povzner, A. A.; Volkov, A. G.; Nogovitsyna, T. A.

2018-04-01

The paper deals with the electronic heat capacity of iron monosilicide FeSi subjected to semiconductor-metal thermal transition during which the formation of its spintronic properties is observed. The proposed model which considers pd-hybridization of strongly correlated d-electrons with non-correlated p-electrons, demonstrates a connection of their contribution to heat capacity in the insulator phase with paramagnon effects and fluctuations of occupation numbers for p- and d-states. In a slitless state, the temperature curve of heat capacity is characterized by a maximum appeared due to normalization of the electron density of states using fluctuating exchange fields. At higher temperatures, a linear growth in heat capacity occurs due to paramagnon effects. The correlation between the model parameters and the first-principles calculation provides the electron contribution to heat capacity, which is obtained from the experimental results on phonon heat capacity. Anharmonicity of phonons is connected merely with the thermal expansion of the crystal lattice.

Computer simulations of upper-hybrid and electron cyclotron resonance heating

International Nuclear Information System (INIS)

Lin, A.T.; Lin, C.C.

1983-01-01

A 2 1/2 -dimensional relativistic electromagnetic particle code is used to investigate the dynamic behavior of electron heating around the electron cyclotron and upper-hybrid layers when an extraordinary wave is obliquely launched from the high-field side into a magnetized plasma. With a large angle of incidence most of the radiation wave energy converts into electrostatic electron Bernstein waves at the upper-hybrid layer. These mode-converted waves propagate back to the cyclotron layer and deposit their energy in the electrons through resonant interactions dominated first by the Doppler broadening and later by the relativistic mass correction. The line shape for both mechanisms has been observed in the simulations. At a later stage, the relativistic resonance effects shift the peak of the temperature profile to the high-field side. The heating ultimately causes the extraordinary wave to be substantially absorbed by the high-energy electrons. The steep temperature gradient created by the electron cyclotron heating eventually reflects a substantial part of the incident wave energy. The diamagnetic effects due to the gradient of the mode-converted Bernstein wave pressure enhance the spreading of the electron heating from the original electron cyclotron layer

Effect of re-heating on the hot electron temperature

International Nuclear Information System (INIS)

Estabrook, K.; Rosen, M.

1980-01-01

Resonant absorption is the direct conversion of the transverse laser light to longitudinal electron plasma waves (epw) at the critical density [10 21 (1.06 μm/lambda 0 ) 2 cm -3 ]. The oscillating longitudinal electric field of the epw heats the electrons by accelerating them down the density gradient to a temperature of approximately 21T/sub e/ 0 25 ([I(W/cm 2 )/10 16 ](lambda 0 /1.06 μm) 2 ) 0 4 . This section extends the previous work by studying the effects of magnetic fields and collisions (albedo) which return the heated electrons for further heating. A magnetic field increases their temperature and collisions do not

Hot-electron-plasma accumulation in the CIRCE mirror experiment

International Nuclear Information System (INIS)

Bardet, R.; Briand, P.; Dupas, L.; Gormezano, C.; Melin, G.

1975-01-01

In the CIRCE experiment, the plasma is obtained by the trapping of a plasma injected into a magnetic bottle by electron heating at cyclotron resonance. The plasma density lies between 5x10 11 cm -3 and 10 12 cm -3 , the electron temperature is about 100 keV and the ion temperature is in the range of few hundred electronvolts. Gross instabilities are not observed. The ratio of the plasma density to the neutral-gas density inside the plasma is higher than 100. A few kilowatts of r.f. power at 8 GHz are sufficient to obtain these results, a fact which looks encouraging as far as the creation of a more effective fast-neutral-target plasma using the CIRCE-experiment concept is concerned. (author)

Perturbative Heat Transport Experiments on TJ-II

International Nuclear Information System (INIS)

Eguilor, S.; Castejon, F.; Luna, E. de la; Cappa, A.; Likin, K.; Fernandez, A.; Tj-II, T.

2002-01-01

Heat wave experiments are performed on TJ-II stellarator plasmas to estimate both heat diffusivity and power deposition profiles. High frequency ECRH modulation experiments are used to obtain the power deposition profiles, which is observed to be wider and duller than estimated by tracing techniques. The causes of this difference are discussed in the paper. Fourier analysis techniques are used to estimate the heat diffusivity in low frequency ECRH modulation experiments. This include the power deposition profile as a new ingredient. ECHR switch on/off experiments are exploited to obtain power deposition and heat diffusivities profile. Those quantities are compared with the obtained by modulation experiments and transport analysis, showing a good agreement. (Author) 18 refs

Perturbative Heat Transport Experiments on TJ-II

Energy Technology Data Exchange (ETDEWEB)

Eguilor, S.; Castejon, F.; Luna, E. de la; Cappa, A.; Likin, K.; Fernandez, A.; Tj-II, T.

2002-07-01

Heat wave experiments are performed on TJ-II stellarator plasmas to estimate both heat diffusivity and power deposition profiles. High frequency ECRH modulation experiments are used to obtain the power deposition profiles, which is observed to be wider and duller than estimated by tracing techniques. The causes of this difference are discussed in the paper. Fourier analysis techniques are used to estimate the heat diffusivity in low frequency ECRH modulation experiments. This include the power deposition profile as a new ingredient. ECHR switch on/off experiments are exploited to obtain power deposition and heat diffusivities profile. Those quantities are compared with the obtained by modulation experiments and transport analysis, showing a good agreement. (Author) 18 refs.

Theory of hysteresis during electron heating of electromagnetic wave scattering by self-organized dust structures in complex plasmas

Energy Technology Data Exchange (ETDEWEB)

Tsytovich, Vadim, E-mail: tsytov@lpi.ru [A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Vavilova str. 38, Moscow 119991 (Russian Federation); Max Planck Institute for Extraterrestrial Physics, Garching (Germany); Gusein-zade, Namik; Ignatov, Alexander [A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Vavilova str. 38, Moscow 119991 (Russian Federation); Medicobiologic Faculty, Pirogov Russian National Research Medical University, Moscow (Russian Federation)

2015-07-15

Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, the total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.

Lunar heat-flow experiment

Science.gov (United States)

Langseth, M. G.

1977-01-01

The principal components of the experiment were probes, each with twelve thermometers of exceptional accuracy and stability, that recorded temperature variations at the surface and in the regolith down to 2.5 m. The Apollo 15 experiment and the Apollo 17 probes recorded lunar surface and subsurface temperatures. These data provided a unique and valuable history of the interaction of solar energy with lunar surface and the effects of heat flowing from the deep interior out through the surface of the moon. The interpretation of these data resulted in a clearer definition of the thermal and mechanical properties of the upper two meters of lunar regolith, direct measurements of the gradient in mean temperature due to heat flow from the interior and a determination of the heat flow at the Apollo 15 and Apollo 17 sites.

Simultaneous Propagation of Heat Waves Induced by Sawteeth and Electron-Cyclotron Heating Power Modulation in the Rtp Tokamak

NARCIS (Netherlands)

Gorini, G.; Mantica, P.; Hogeweij, G. M. D.; De Luca, F.; Jacchia, A.; Konings, J. A.; Cardozo, N. J. L.; Peters, M.

1993-01-01

The incremental electron heat diffusivity chi(inc) is determined in Rijnhuizen Tokamak Project plasmas by measurements of simultaneous heat pulses due to (1) the sawtooth instability and (2) modulated electron cyclotron heating. No systematic difference is observed between the two measured chi(inc)

Modeling of N2 and O optical emissions for ionosphere HF powerful heating experiments

Science.gov (United States)

Sergienko, T.; Gustavsson, B.

Analyses of experiments of F region ionosphere modification by HF powerful radio waves show that optical observations are very useful tools for diagnosing of the interaction of the probing radio wave with the ionospheric plasma Hitherto the emissions usually measured in the heating experiment have been the 630 0 nm and the 557 7 nm lines of atomic oxygen Other emissions for instance O 844 8 nm and N2 427 8 nm have been measured episodically in only a few experiments although the very rich optical spectrum of molecular nitrogen potentially involves important information about ionospheric plasma in the heated region This study addresses the modeling of optical emissions from the O and the N2 triplet states first positive second positive Vegard-Kaplan infrared afterglow and Wu-Benesch band systems excited under a condition of the ionosphere heating experiment The auroral triplet state population distribution model was modified for the ionosphere heating conditions by using the different electron distribution functions suggested by Mishin et al 2000 2003 and Gustavsson at al 2004 2005 Modeling results are discussed from the point of view of efficiency of measurements of the N2 emissions in future experiments

Characterization of a high performance ultra-thin heat pipe cooling module for mobile hand held electronic devices

Science.gov (United States)

Ahamed, Mohammad Shahed; Saito, Yuji; Mashiko, Koichi; Mochizuki, Masataka

2017-11-01

In recent years, heat pipes have been widely used in various hand held mobile electronic devices such as smart phones, tablet PCs, digital cameras. With the development of technology these devices have different user friendly features and applications; which require very high clock speeds of the processor. In general, a high clock speed generates a lot of heat, which needs to be spreaded or removed to eliminate the hot spot on the processor surface. However, it is a challenging task to achieve proper cooling of such electronic devices mentioned above because of their confined spaces and concentrated heat sources. Regarding this challenge, we introduced an ultra-thin heat pipe; this heat pipe consists of a special fiber wick structure named as "Center Fiber Wick" which can provide sufficient vapor space on the both sides of the wick structure. We also developed a cooling module that uses this kind of ultra-thin heat pipe to eliminate the hot spot issue. This cooling module consists of an ultra-thin heat pipe and a metal plate. By changing the width, the flattened thickness and the effective length of the ultra-thin heat pipe, several experiments have been conducted to characterize the thermal properties of the developed cooling module. In addition, other experiments were also conducted to determine the effects of changes in the number of heat pipes in a single module. Characterization and comparison of the module have also been conducted both experimentally and theoretically.

Design of a cavity heat pipe receiver experiment

Science.gov (United States)

Schneider, Michael G.; Brege, Mark H.; Greenlee, William J.

1992-01-01

A cavity heat pipe experiment has been designed to test the critical issues involved with incorporating thermal energy storage canisters into a heat pipe. The experiment is a replication of the operation of a heat receiver for a Brayton solar dynamic power cycle. The heat receiver is composed of a cylindrical receptor surface and an annular heat pipe with thermal energy storage canisters and gaseous working fluid heat exchanger tubes surrounding it. Hardware for the cavity heat pipe experiment will consist of a sector of the heat pipe, complete with gas tube and thermal energy storage canisters. Thermal cycling tests will be performed on the heat pipe sector to simulate the normal energy charge/discharge cycle of the receiver in a spacecraft application.

The kinetics of low-temperature electron-phonon relaxation in a metallic film following instantaneous heating of the electrons

International Nuclear Information System (INIS)

Bezuglyi, A.I.; Shklovskii, V.A.

1997-01-01

The theoretical analysis of experiments on pulsed laser irradiation of metallic films sputtered on insulating supports is usually based on semiphenomenological dynamical equations for the electron and phonon temperatures, an approach that ignores the nonuniformity and the nonthermal nature of the phonon distribution function. In this paper we discuss a microscopic model that describes the dynamics of the electron-phonon system in terms of kinetic equations for the electron and phonon distribution functions. Such a model provides a microscopic picture of the nonlinear energy relaxation of the electron-phonon system of a rapidly heated film. We find that in a relatively thick film the energy relaxation of electrons consists of three stages: the emission of nonequilibrium phonons by 'hot' electrons, the thermalization of electrons and phonons due to phonon reabsorption, and finally the cooling of the thermalized electron-phonon system as a result of phonon exchange between film and substrate. In thin films, where there is no reabsorption of nonequilibrium phonons, the energy relaxation consists of only one stage, the first. The relaxation dynamics of an experimentally observable quantity, the phonon contribution to the electrical conductivity of the cooling film, is directly related to the dynamics of the electron temperature, which makes it possible to use the data of experiments on the relaxation of voltage across films to establish the electron-phonon and phonon-electron collision times and the average time of phonon escape from film to substrate

Understanding the role of fast electrons in the heating of dense matter: experimental techniques and recent results

International Nuclear Information System (INIS)

Freeman, R.; Anderson, C.; Hill, J.M.; King, J.; Snavely, R.; Hatchett, S.; Key, M.; Koch, J.; MacKinnon, A.; Stephens, R.; Cowan, T.

2003-01-01

An intense laser impinging upon dense matter converts a large fraction of its energy into fast electrons. (Here we take 'fast' to mean electrons that are much more energetic than the normal Boltzmann-like distribution measured in the tens to hundreds of eV.) Upon transiting the interior of the dense matter, these electrons are responsible for isochoric heating of the material. Just how these electrons traverse the material, and various interfaces within the material, is a subject of substantial amounts of computation and theory, and recently, experiments. Here we outline the nature of the heating mechanisms, and the current level of understanding of the complex physical processes. In particular we discuss new experimental techniques to record essential features of this transport problem

Hot-electron plasma formation and confinement in the Tandem Mirror Experiment-Upgrade

International Nuclear Information System (INIS)

Ress, D.B.

1988-01-01

Electron-cyclotron range-of-frequency heating (ECRH) at 28 GHz is used to create a population of mirror-confined hot electrons in the Tandem Mirror Experiment-Upgrade (TMX-U). Generation of a large fraction of such electrons within each end-cell of TMX-U is essential to the formation of the desired electrostatic potential profile of the thermal-barrier tandem mirror. The formation and confinement of the ECRH-generated hot-electron plasma was investigated with a variety of diagnostic instruments, including a novel instrumented limiter probe. The author characterized the spatial structure of the hot-electron plasma. Details of the heating process cause the plasma to separate into two regions: a halo, consisting entirely of energetic electrons, and a core, which is dominated by cooler electrons. The plasma structure forms rapidly under the action of second-harmonic ECRH. Fundamental ECRH, which is typically applied simultaneously, is only weakly absorbed and generally does not create energetic electrons. The ECRH-generated plasma displays several loss mechanisms. Hot electrons in the halo region, with T e ∼ 30 keV, are formed by localized ECRH near the plasma boundary, and are lost through a radial process involving open magnetic-curvature-drift surfaces

Heat pipe with PCM for electronic cooling

International Nuclear Information System (INIS)

Weng, Ying-Che; Cho, Hung-Pin; Chang, Chih-Chung; Chen, Sih-Li

2011-01-01

This article experimentally investigates the thermal performances of a heat pipe with phase change material for electronic cooling. The adiabatic section of heat pipe is covered by a storage container with phase change material (PCM), which can store and release thermal energy depending upon the heating powers of evaporator and fan speeds of condenser. Experimental investigations are conducted to obtain the system temperature distributions from the charge, discharge and simultaneous charge/discharge performance tests. The parameters in this study include three kinds of PCMs, different filling PCM volumes, fan speeds, and heating powers in the PCM cooling module. The cooling module with tricosane as PCM can save 46% of the fan power consumption compared with the traditional heat pipe.

JET ({sup 3}He)-D scenarios relying on RF heating: survey of selected recent experiments

Energy Technology Data Exchange (ETDEWEB)

Van Eester, D; Lerche, E; Andrew, Y; Biewer, T M; Casati, A; Crombe, K; De la Luna, E; Ericsson, G; Felton, R; Giacomelli, L; Giroud, C; Hawkes, N; Hellesen, C; Hjalmarsson, A; Joffrin, E; Kaellne, J; Kiptily, V; Lomas, P; Mantica, P; Marinoni, A [JET-EFDA Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)] (and others)

2009-04-15

Recent JET experiments have been devoted to the study of ({sup 3}He)-D plasmas involving radio frequency (RF) heating. This paper starts by discussing the RF heating efficiency theoretically expected in such plasmas, covering both relevant aspects of wave and of particle dynamics. Then it gives a concise summary of the main conclusions drawn from recent experiments that were either focusing on studying RF heating physics aspects or that were adopting RF heating as a tool to study plasma behavior. Depending on the minority concentration chosen, different physical phenomena are observed. At very low concentration (X[{sup 3}He] < 1%), energetic tails are formed which trigger MHD activity and result in loss of fast particles. Alfven cascades were observed and gamma ray tomography indirectly shows the impact of sawtooth crashes on the fast particle orbits. Low concentration (X[{sup 3}He] < 10%) favors minority heating while for X[{sup 3}He] >> 10% electron mode conversion damping becomes dominant. Evidence for the Fuchs et al standing wave effect (Fuchs et al 1995 Phys. Plasmas 2 1637-47) on the absorption is presented. RF induced deuterium tails were observed in mode conversion experiments with large X[{sup 3}He] ({approx}18%). As tentative modeling shows, the formation of these tails can be explained as a consequence of wave power absorption by neutral beam particles that efficiently interact with the waves well away from the cold D cyclotron resonance position as a result of their substantial Doppler shift. As both ion and electron RF power deposition profiles in ({sup 3}He)-D plasmas are fairly narrow-giving rise to localized heat sources-the RF heating method is an ideal tool for performing transport studies. Various of the experiments discussed here were done in plasmas with internal transport barriers (ITBs). ITBs are identified as regions with locally reduced diffusivity, where poloidal spinning up of the plasma is observed. The present know-how on the role of

X-ray analysis of electron Bernstein wave heating in MST

Energy Technology Data Exchange (ETDEWEB)

Seltzman, A. H., E-mail: seltzman@wisc.edu; Anderson, J. K.; DuBois, A. M.; Almagri, A.; Forest, C. B. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)

2016-11-15

A pulse height analyzing x-ray tomography system has been developed to detect x-rays from electron Bernstein wave heated electrons in the Madison symmetric torus reversed field pinch (RFP). Cadmium zinc telluride detectors are arranged in a parallel beam array with two orthogonal multi-chord detectors that may be used for tomography. In addition a repositionable 16 channel fan beam camera with a 55° field of view is used to augment data collected with the Hard X-ray array. The chord integrated signals identify target emission from RF heated electrons striking a limiter located 12° toroidally away from the RF injection port. This provides information on heated electron spectrum, transport, and diffusion. RF induced x-ray emission from absorption on harmonic electron cyclotron resonances in low current (<250 kA) RFP discharges has been observed.

Direct electronic measurement of Peltier cooling and heating in graphene.

Science.gov (United States)

Vera-Marun, I J; van den Berg, J J; Dejene, F K; van Wees, B J

2016-05-10

Thermoelectric effects allow the generation of electrical power from waste heat and the electrical control of cooling and heating. Remarkably, these effects are also highly sensitive to the asymmetry in the density of states around the Fermi energy and can therefore be exploited as probes of distortions in the electronic structure at the nanoscale. Here we consider two-dimensional graphene as an excellent nanoscale carbon material for exploring the interaction between electronic and thermal transport phenomena, by presenting a direct and quantitative measurement of the Peltier component to electronic cooling and heating in graphene. Thanks to an architecture including nanoscale thermometers, we detected Peltier component modulation of up to 15 mK for currents of 20 μA at room temperature and observed a full reversal between Peltier cooling and heating for electron and hole regimes. This fundamental thermodynamic property is a complementary tool for the study of nanoscale thermoelectric transport in two-dimensional materials.

Modeling of high power ICRF heating experiments on TFTR

International Nuclear Information System (INIS)

Phillips, C.K.; Wilson, J.R.; Bell, M.; Fredrickson, E.; Hosea, J.C.; Majeski, R.; Ramsey, A.; Rogers, J.H.; Schilling, G.; Skinner, C.; Stevens, J.E.; Taylor, G.; Wong, K.L.; Murakami, M.

1993-01-01

Over the past two years, ICRF heating experiments have been performed on TFTR in the hydrogen minority heating regime with power levels reaching 11.2 MW in helium-4 majority plasmas and 8.4 MW in deuterium majority plasmas. For these power levels, the minority hydrogen ions, which comprise typically less than 10% of the total electron density, evolve into la very energetic, anisotropic non-Maxwellian distribution. Indeed, the excess perpendicular stored energy in these plasmas associated with the energetic minority tail ions is often as high as 25% of the total stored energy, as inferred from magnetic measurements. Enhanced losses of 0.5 MeV protons consistent with the presence of an energetic hydrogen component have also been observed. In ICRF heating experiments on JET at comparable and higher power levels and with similar parameters, it has been suggested that finite banana width effects have a noticeable effect on the ICRF power deposition. In particular, models indicate that finite orbit width effects lead to a reduction in the total stored energy and of the tail energy in the center of the plasma, relative to that predicted by the zero banana width models. In this paper, detailed comparisons between the calculated ICRF power deposition profiles and experimentally measured quantities will be presented which indicate that significant deviations from the zero banana width models occur even for modest power levels (P rf ∼ 6 MW) in the TFTR experiments

ECRH and electron heat transport in tokamaks

International Nuclear Information System (INIS)

Zou, X.L.; Giruzzi, G.; Dumont, R.J.

2003-01-01

It has been observed during the ECRH experiments in tokamaks that the shape of the electron temperature profile in stationary regimes is not very sensitive to the ECRH power deposition i.e. the temperature profile remains peaked at the center even though the ECRH power deposition is off-axis. Various models have been invoked for the interpretation of this profile resilience phenomenon: the inward heat pinch, the critical temperature gradient, the Self-Organized Criticality, etc. Except the pinch effect, all of these models need a specific form of the diffusivity in the heat transport equation. In this work, our approach is to solve a simplified time-dependent heat transport equation analytically in cylindrical geometry. The features of this analytical solution are analyzed, in particular the relationship between the temperature profile resilience and the Eigenmode of the physical system with respect to the heat transport phenomenon. Finally, applications of this analytical solution for the determination of the transport coefficient and the polarization of the EC waves are presented. It has been shown that the solution of the simplified transport equation in a finite cylinder is a Fourier-Bessel series. This series represents in fact a decomposition of the heat source in Eigenmode, which are characterized by the Bessel functions of order 0. The physical interpretation of the Eigenmodes is the following: when the heat source is given by a Bessel function of order 0, the temperature profile has exactly the same form as the source at every time. At the beginning of the power injection, the effectiveness of the temperature response is the same for each Eigenmode, and the response in temperature, having the same form as the source, is local. Conversely, in the later phase of the evolution, the effectiveness of the temperature response for each Eigenmode is different: the higher the order, the lower the effectiveness. In this case the response in temperature appears as

Fast wave heating experiments in the ion cyclotron range of frequencies on ATF

Energy Technology Data Exchange (ETDEWEB)

Kwon, M; Shepard, T D; Goulding, R H [Oak Ridge National Lab., TN (United States); and others

1992-07-01

Fast wave heating experiments in the ion cyclotron range of frequencies (ICRF) were performed on target plasmas produced by 350 kW of electron cyclotron heating at 53 GHz and also by neutral beam injection in the Advanced Toroidal Facility (ATF). Various heating regimes were investigated in the frequency range between 9.2 MHz and 28.8 MHz with magnetic fields of 0.95 T and 1.9 T on axis. The nominal pulse lengths of up to 200 kW RF power were in the range between 100 and 400 ms. Data from spectroscopy, loading measurements, and edge RF and Langmuir probes were used to characterize the RF induced effects on the ATF plasma. In the hydrogen minority regime at low plasma density, large suprathermal ion tails were observed with a neutral particle analyser. At high density (n-bar{sub e} {>=} 5.0 x 10{sup 13} cm{sup -3}) substantial increases in antenna loading were observed, but ICRF power was insufficient to produce definitive heating results. A two-dimensional RF heating code, ORION, and a Fokker-Planck code, RFTRANS, were used to simulate these experiments. A simulation of future high power, higher density experiments in ATF indicates improved bulk heating results due to the improved loading and more efficient thermalization of the minority tail. (author). 29 refs, 16 figs, 3 tabs.

Plasma heating via electron Bernstein wave heating using ordinary and extraodinary mode

Directory of Open Access Journals (Sweden)

A. Parvazian

2008-03-01

Full Text Available Magnetically confined plasma can be heated with high power microwave sources. In spherical torus the electron plasma frequency exeeds the electron cyclotron frequency (EC and, as a consequence, electromagnetic waves at fundamental and low harmonic EC cannot propagate within the plasma. In contrast, electron Bernstein waves (EBWs readily propagate in spherical torus plasma and are absorbed strongly at the electron cyclotron resonances. In order to proagate EBWs beyond the upper hybrid resonance (UHR, that surrounds the plasma, the EBWs must convert via one of two processes to either ordinary (O-mode or extraordinary (X-mode electromagnetic waves. O-mode and X-mode electromagnetic waves lunched at the plasma edge can convert to the electron Bernstein waves (EBWs which can propagate without and cut-off into the core of the plasma and damp on electrons. Since the electron Bernstein wave (EBW has no cut-off limits, it is well suited to heat an over-dense plasma by resonant absorption. An important problem is to calculate mode conversion coefficient that is very sensitive to density. Mode conversion coefficient depends on Budden parameter ( ñ and density scale length (Ln in upper hybrid resonance (UHR. In Mega Ampere Spherical Tokamak (MAST, the optimized conversion efficiency approached 72.5% when Ln was 4.94 cm and the magnetic field was 0.475 Tesla in the core of the plasma.

Transitions to improved core electron heat confinement triggered by low order rational magnetic surfaces in the stellarator TJ-II

International Nuclear Information System (INIS)

Estrada, T.; Medina, F.; Lopez-Bruna, D.; AscasIbar, E.; BalbIn, R.; Cappa, A.; Castejon, F.; Eguilior, S.; Fernandez, A.; Guasp, J.; Hidalgo, C.; Petrov, S.

2007-01-01

Transitions to improved core electron heat confinement are triggered by low order rational magnetic surfaces in TJ-II electron cyclotron heated (ECH) plasmas. Experiments are performed changing the magnetic shear around the rational surface n = 3/m = 2 to study its influence on the transition; ECH power modulation is used to look at transport properties. The improvement in the electron heat confinement shows no obvious dependence on the magnetic shear. Transitions triggered by the rational surface n = 4/m = 2 show, in addition, an increase in the ion temperature synchronized with the increase in the electron temperature. Ion temperature changes had not been previously observed either in TJ-II or in any other helical device. SXR measurements demonstrate that, under certain circumstances, the rational surface positioned inside the plasma core region precedes and provides a trigger for the transition

X-ray Heating and Electron Temperature of Laboratory Photoionized Plasmas

Science.gov (United States)

Mancini, Roberto; Lockard, Tom; Mayes, Daniel C.; Loisel, Guillaume; Bailey, James E.; Rochau, Gregory; Abdallah, J.; Golovkin, I.

2018-06-01

In separate experiments performed at the Z facility of Sandia National Laboratories two different samples were employed to produce and characterize photoionized plasmas. One was a gas cell filled with neon, and the other was a thin silicon layer coated with plastic. Both samples were driven by the broadband x-ray flux produced at the collapse of a wire array z-pinch implosion. Transmission spectroscopy of a narrowband portion of the x-ray flux was used to diagnose the charge state distribution, and the electron temperature was extracted from a Li-like ion level population ratio. To interpret the temperature measurement, we performed Boltzmann kinetics and radiation-hydrodynamic simulations. We found that non-equilibrium atomic physics and the coupling of the radiation flux to the atomic level population kinetics play a critical role in modeling the x-ray heating of photoionized plasmas. In spite of being driven by similar x-ray drives, differences of ionization and charged state distributions in the neon and silicon plasmas are reflected in the plasma heating and observed electron temperatures.This work was sponsored in part by DOE Office of Science Grant DE-SC0014451, and the Z Facility Fundamental Science Program of SNL.

Observations of rotation in JET plasmas with electron heating by ion cyclotron resonance heating

DEFF Research Database (Denmark)

Hellsten, T.; Johnson, T. J.; Van Eester, D.

2012-01-01

The rotation of L-mode plasmas in the JET tokamak heated by waves in the ion cyclotron range of frequencies (ICRF) damped on electrons, is reported. The plasma in the core is found to rotate in the counter-current direction with a high shear and in the outer part of the plasma with an almost......, electron absorption of the fast magnetosonic wave by transit time magnetic pumping and electron Landau damping (TTMP/ELD) is the dominating absorption mechanism. Inverted mode conversion is done in (He-3)-H plasmas where the mode converted waves are essentially absorbed by electron Landau damping. Similar...... rotation profiles are seen when heating at the second harmonic cyclotron frequency of He-3 and with mode conversion at high concentrations of He-3. The magnitude of the counter-rotation is found to decrease with an increasing plasma current. The correlation of the rotation with the electron temperature...

Thermal characterization of indirectly heated axi-symmetric solid cathode electron beam gun for melting application

International Nuclear Information System (INIS)

Prakash, B.; Gupta, S.; Malik, P.; Mishra, K.K.; Jha, M.N.; Kandaswamy, E.; Martin, M.

2015-01-01

Electron beam melting gun with indirectly heated axi-symmetric solid cathode was designed, fabricated and characterized experimentally. The thermal simulation and optical analysis of the electron gun was carried out to estimate the power required to achieve the emission temperature of the solid cathode, to obtain the temperature distribution in the assembly and the beam transportation. On the basis of the thermal simulation and electron optics, the electron gun design was finalised. The electron gun assembly was fabricated and installed in the vacuum chamber for carrying out the experiment to find the actual temperature distribution. Thermocouple and two colour pyrometer were used to measure the temperature at various locations in the electron gun. The attenuation effect of the viewing port glass of the vacuum chamber was compensated in the final reading of the temperature measured by the pyrometer. The temperature of solid cathode obtained by the experiment was found to be 2800K which is the emission temperature of solid cathode. (author)

Electron cyclotron heating and current drive: Present experiments to ITER. Revision 1

International Nuclear Information System (INIS)

Harvey, R.W.; Nevins, W.M.; Smith, G.R.; Lloyd, B.; O'Brien, M.R.; Warrick, C.D.

1995-08-01

Electron cyclotron (EC) power has technological and physics advantages for heating and current drive in a tokamak reactor, and advances in source development make it credible for applications in ITER. Strong single pass absorption makes heating to ignition particularly simple. The optimized EC current drive (ECCD) efficiency (left-angle n right-angle IR/P) shows a linear temperature scaling at temperatures up to ∼ 15 keV. For temperatures above 30 keV, the efficiency saturates at approximately 0.3·10 20 A/(m 2 W) for a frequency of 220 GHz in an ITER target plasma with toroidal field of 6 T, due primarily to harmonic overlap [G.R. Smith et al., Phys. Fluids 30 3633 (1987)] and to a lesser extent due to limitations arising from relativistic effects [N.J. Fisch, Phys. Rev. A 24 3245 (1981)]. The same efficiency can also be obtained at 170 GHz for the same plasma equilibrium except that the magnetic field is reduced to (170/220) x 6 T = 4.6 T. The ECCD efficiencies are obtained with the comprehensive 3D, bounce-averaged Fokker-Planck CQL3D codes [R.W. Harvey and M.G. McCoy, Proc. IAEA TCM/Advances in Simulation and Modeling in Thermonuclear Plasmas 1992, Montreal], and BANDIT3D [M.R. O'Brien, M. Cox, C.D. Warrick, and F. S. Zaitsev, ibid.

Electron cyclotron heating calculations for ATF

International Nuclear Information System (INIS)

Goldfinger, R.C.; Batchelor, D.B.

1986-03-01

The RAYS geometrical optics code has been used to calculate electron cyclotron wave propagation and heating in the Advanced Toroidal Facility (ATF) device under construction at Oak Ridge National Laboratory (ORNL). The intent of this work is to predict the outcome of various heating scenarios and to give guidance in designing an optimum heating system. Particular attention is paid to the effects of wave polarization and antenna location. We investigate first and second harmonic cyclotron heating with the parameters predicted for steady-state ATF operation. We also simulate the effect of wall reflections by calculating a uniform, isotropic flux of power radiating from the wall. These results, combined with the first-pass calculations, give a qualitative picture of the heat deposition profiles. From these results we identify the compromises that represent the optimum heating strategies for the ATF model considered here. Our basic conclusions are that second harmonic heating with the extraordinary mode (X-mode) gives the best result, with fundamental ordinary mode (O-mode) heating being slightly less efficient. Assuming the antenna location is restricted to the low magnetic field side, the antenna should be placed at phi = 0 0 (the toroidal angle where the helical coils are at the sides) for fundamental heating and at phi = 15 0 (where the helical coils are at the top and bottom) for second harmonic heating. These recommendations come directly from the ray tracing results as well as from a theoretical identification of the relevant factors affecting the heating

Studies of improved electron confinement in low density L-mode National Spherical Torus Experiment discharges

International Nuclear Information System (INIS)

Stutman, D.; Finkenthal, M.; Tritz, K.; Redi, M. H.; Kaye, S. M.; Bell, M. G.; Bell, R. E.; LeBlanc, B. P.; Hill, K. W.; Medley, S. S.; Menard, J. E.; Rewoldt, G.; Wang, W. X.; Synakowski, E. J.; Levinton, F.; Kubota, S.; Bourdelle, C.; Dorland, W.; The NSTX Team

2006-01-01

Electron transport is rapid in most National Spherical Torus Experiment, M. Ono et al., Nucl. Fusion 40, 557 (2000) beam heated plasmas. A regime of improved electron confinement is nevertheless observed in low density L-mode (''low-confinement'') discharges heated by early beam injection. Experiments were performed in this regime to study the role of the current profile on thermal transport. Variations in the magnetic shear profile were produced by changing the current ramp rate and onset of neutral beam heating. An increased electron temperature gradient and local minimum in the electron thermal diffusivity were observed at early times in plasmas with the fastest current ramp and earliest beam injection. In addition, an increased ion temperature gradient associated with a region of reduced ion transport is observed at slightly larger radii. Ultrasoft x-ray measurements of double-tearing magnetohydrodynamic activity, together with current diffusion calculations, point to the existence of negative magnetic shear in the core of these plasmas. Discharges with slower current ramp and delayed beam onset, which are estimated to have more monotonic q-profiles, do not exhibit regions of reduced transport. The results are discussed in the light of the initial linear microstability assessment of these plasmas, which suggests that the growth rate of all instabilities, including microtearing modes, can be reduced by negative or low magnetic shear in the temperature gradient region. Several puzzles arising from the present experiments are also highlighted

Study of electron and proton isochoric heating for fast ignition

International Nuclear Information System (INIS)

Key, M.H.; Chen, M.H.; Chung, H.K.; Foord, M.E.; Gregori, G.; Hatchett, S.P.; Koch, J.A.; Lasinski, B.F.; Langdon, B.; MacKinnon, A.J.; Patel, P.; Snavely, R.A.; Tabak, M.; Town, R.; Wilks, S.C.; Akli, K.; Freeman, R.R.; Gu, P.; Hey, D.; Hill, J.M.; King, J.A.; Patel, N.; Zhang, B.; Freeman, R.R.; Stephens, R.B.; Beg, F.; Pasley, J.; Green, J.S.; Lancaster, K.; Murphy, C.D.; Norreys, P.A.; Green, J.S.; Murphy, C.D.; Habara, H.; Kodama, R.; Tanaka, K.; Yabuuchi, T.; Stoeckl, C.; Theobald, W.

2006-01-01

Isochoric heating by electrons has been measured in the two limiting cases of small area thin foils with dominant refluxing and cone-long-wire geometry with negligible refluxing in the wire. Imaging of Cu Kα cone fluorescence, crystal X-ray spectroscopy of Cu K shell emission, and X UV imaging at 68 eV and 256 eV are discussed. Laser power on target was typically 0.5 PW in 0.7 ps. Heating by focused proton beams generated at the concave inside surface of a hemi-shell and from a sub hemi-shell inside 30 degrees cone has been studied with the same diagnostic methods plus imaging of proton induced Kα. Conversion efficiency to protons has been measured and modeled. Conclusions from the experiments, links to theoretical understanding and relevance to fast ignition are outlined. (authors)

TRIAM-1 turbulent heating experiment

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Yukio; Hiraki, Naoji; Nakamura, Kazuo; Kikuchi, Mitsuru; Nagao, Akihiro [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1983-02-01

The experimental studies on the containment of high temperature plasma and turbulent heating using the tokamak device with strong magnetic field (TRIAM-1) started in 1977 have achieved much results up to fiscal 1979, and the anticipated objectives were almost attained. The results of these studies were summarized in the ''Report of the results of strong magnetic field tokamak TRIAM-1 experiment''. In this report, the results obtained by the second stage project of the TRIAM-1 project are summarized. The second stage was the two-year project for fiscal 1980 and 81. In the second stage project, by the complete preparation of measuring instrument and the improvement of the experimental setup, the carefully planned experiment on turbulent heating was performed, in particular, the clarification of the mechanism of turbulent heating was the central theme. As the important results obtained, the detection of ion sound waves at the time of turbulent heating, the formation of high energy ions by wave-particle interaction and the clarification of the process of their energy relaxation, and the verification of the effectiveness of double pulse turbulent heating are enumerated.

TRIAM-1 turbulent heating experiment

International Nuclear Information System (INIS)

Nakamura, Yukio; Hiraki, Naoji; Nakamura, Kazuo; Kikuchi, Mitsuru; Nagao, Akihiro

1983-01-01

The experimental studies on the containment of high temperature plasma and turbulent heating using the tokamak device with strong magnetic field (TRIAM-1) started in 1977 have achieved much results up to fiscal 1979, and the anticipated objectives were almost attained. The results of these studies were summarized in the ''Report of the results of strong magnetic field tokamak TRIAM-1 experiment''. In this report, the results obtained by the second stage project of the TRIAM-1 project are summarized. The second stage was the two-year project for fiscal 1980 and 81. In the second stage project, by the complete preparation of measuring instrument and the improvement of the experimental setup, the carefully planned experiment on turbulent heating was performed, in particular, the clarification of the mechanism of turbulent heating was the central theme. As the important results obtained, the detection of ion sound waves at the time of turbulent heating, the formation of high energy ions by waveparticle interaction and the clarification of the process of their energy relaxation, and the verification of the effectiveness of double pulse turbulent heating are enumerated. (Kako, I.)

Experience and Prospects of Nuclear Heat Application

International Nuclear Information System (INIS)

Woite, G.; Konishi, T.; Kupitz, J.

1998-01-01

Relevant technical characteristics of nuclear reactors and heat application facilities for district heating, process heat and seawater desalination are presented and discussed. The necessity of matching the characteristics of reactors and heat applications has consequences for their technical and economic viability. The world-wide operating experience with nuclear district heating, process heating, process heat and seawater desalination is summarised and the prospects for these nuclear heat applications are discussed. (author)

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

International Nuclear Information System (INIS)

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

1993-10-01

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

Coupling between particle and heat transport during power modulation experiments in Tore Supra

International Nuclear Information System (INIS)

Zou, X.L.; Giruzzi, G.; Artaud, J.F.; Bouquey, F.; Bremond, S.; Clary, J.; Darbos, C.; Eury, S.P.; Lennholm, M.; Magne, R.; Segui, J.L.

2004-01-01

Power modulations are a powerful tool often used to investigate heat transport processes in tokamaks. In some situations, this could also be an interesting method for the investigation of the particle transport due to the anomalous pinch. Low frequency (∼ 1 Hz) power modulation experiments, using both electron cyclotron resonance heating (ECRH) and ion cyclotron resonance heating (ICRH), have been performed in the Tore Supra tokamak. Strong coupling has been observed between the temperature and density modulations during the low frequency ECRH and ICRH modulation experiments. It has been shown that mechanisms as outgassing, Ware pinch effect, curvature driven pinch are not likely to be responsible for this density modulation. Because of its dependence on temperature or temperature gradient, the thermodiffusion is a serious candidate to be the driving source for this density modulation. This analysis shows that low frequency power modulation experiments have a great potential for the investigation of the anomalous particle pinch in tokamaks. Future plans will include the use of more precise density profile measurements using X-mode reflectometry

Coupling between particle and heat transport during power modulation experiments in Tore Supra

Energy Technology Data Exchange (ETDEWEB)

Zou, X.L.; Giruzzi, G.; Artaud, J.F.; Bouquey, F.; Bremond, S.; Clary, J.; Darbos, C.; Eury, S.P.; Lennholm, M.; Magne, R.; Segui, J.L

2004-07-01

Power modulations are a powerful tool often used to investigate heat transport processes in tokamaks. In some situations, this could also be an interesting method for the investigation of the particle transport due to the anomalous pinch. Low frequency ({approx} 1 Hz) power modulation experiments, using both electron cyclotron resonance heating (ECRH) and ion cyclotron resonance heating (ICRH), have been performed in the Tore Supra tokamak. Strong coupling has been observed between the temperature and density modulations during the low frequency ECRH and ICRH modulation experiments. It has been shown that mechanisms as outgassing, Ware pinch effect, curvature driven pinch are not likely to be responsible for this density modulation. Because of its dependence on temperature or temperature gradient, the thermodiffusion is a serious candidate to be the driving source for this density modulation. This analysis shows that low frequency power modulation experiments have a great potential for the investigation of the anomalous particle pinch in tokamaks. Future plans will include the use of more precise density profile measurements using X-mode reflectometry.

Extension of electron cyclotron heating at ASDEX Upgrade with respect to high density operation

Directory of Open Access Journals (Sweden)

Schubert Martin

2017-01-01

Full Text Available The ASDEX Upgrade electron cyclotron resonance heating operates at 105 GHz and 140 GHz with flexible launching geometry and polarization. In 2016 four Gyrotrons with 10 sec pulse length and output power close to 1 MW per unit were available. The system is presently being extended to eight similar units in total. High heating power and high plasma density operation will be a part of the future ASDEX Upgrade experiment program. For the electron cyclotron resonance heating, an O-2 mode scheme is proposed, which is compatible with the expected high plasma densities. It may, however, suffer from incomplete single-pass absorption. The situation can be improved significantly by installing holographic mirrors on the inner column, which allow for a second pass of the unabsorbed fraction of the millimetre wave beam. Since the beam path in the plasma is subject to refraction, the beam position on the holographic mirror has to be controlled. Thermocouples built into the mirror surface are used for this purpose. As a protective measure, the tiles of the heat shield on the inner column were modified in order to increase the shielding against unabsorbed millimetre wave power.

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

International Nuclear Information System (INIS)

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

1987-11-01

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

Micro-Columnated Loop Heat Pipe: The Future of Electronic Substrates

Science.gov (United States)

Dhillon, Navdeep Singh

The modern world is run by semiconductor-based electronic systems. Due to continuous improvements in semiconductor device fabrication, there is a clear trend in the market towards the development of electronic devices and components that not only deliver enhanced computing power, but are also more compact. Thermal management has emerged as the primary challenge in this scenario where heat flux dissipation of electronic chips is increasing exponentially, but conventional cooling solutions such as conduction and convection are no longer feasible. To keep device junction temperatures within the safe operating limit, there is an urgent requirement for ultra-high-conductivity thermal substrates that not only absorb and transport large heat fluxes, but can also provide localized cooling to thermal hotspots. This dissertation describes the design, modeling, and fabrication of a phase change-based, planar, ultra-thin, passive thermal transport system that is inspired by the concept of loop heat pipes and capillary pumped loops. Fabricated on silicon and Pyrex wafers using microfabrication techniques, the micro-columnated loop heat pipe (muCLHP) can be integrated directly with densely packed or multiply-stacked electronic substrates, to provide localized high-heat-flux thermal management. The muCLHP employs a dual-scale coherent porous silicon(CPS)-based micro-columnated wicking structure, where the primary CPS wick provides large capillary forces for fluid transport, while a secondary surface-wick maximizes the rate of thin-film evaporation. To overcome the wick thickness limitation encountered in conventional loop heat pipes, strategies based on MEMS surface micromachining techniques were developed to reduce parasitic heat flow from the evaporator to the compensation chamber of the device. Finite element analysis was used to confirm this reduction in a planar evaporator design, thus enabling the generation of a large motive temperature head for continuous device operation

Diamond-based heat spreaders for power electronic packaging applications

Science.gov (United States)

Guillemet, Thomas

As any semiconductor-based devices, power electronic packages are driven by the constant increase of operating speed (higher frequency), integration level (higher power), and decrease in feature size (higher packing density). Although research and innovation efforts have kept these trends continuous for now more than fifty years, the electronic packaging technology is currently facing a challenge that must be addressed in order to move toward any further improvements in terms of performances or miniaturization: thermal management. Thermal issues in high-power packages strongly affect their reliability and lifetime and have now become one of the major limiting factors of power modules development. Thus, there is a strong need for materials that can sustain higher heat flux levels while safely integrating into the electronic package architecture. In such context, diamond is an attractive candidate because of its outstanding thermal conductivity, low thermal expansion, and high electrical resistivity. Its low heat capacity relative to metals such as aluminum or copper makes it however preferable for heat spreading applications (as a heat-spreader) rather than for dissipating the heat flux itself (as a heat sink). In this study, a dual diamond-based heat-spreading solution is proposed. Polycrystalline diamond films were grown through laser-assisted combustion synthesis on electronic substrates (in the U.S) while, in parallel, diamond-reinforced copper-matrix composite films were fabricated through tape casting and hot pressing (in France). These two types of diamond-based heat-spreading films were characterized and their microstructure and chemical composition were related to their thermal performances. Particular emphasize was put on the influence of interfaces on the thermal properties of the materials, either inside a single material (grain boundaries) or between dissimilar materials (film/substrate interface, matrix/reinforcement interface). Finally, the packaging

Experiments on two-step heating of a dense plasma in the GOL-3 facility

International Nuclear Information System (INIS)

Astrelin, V.T.; Burdakov, A.V.; Koidan, V.S.; Mekler, K.I.; Mel'nikov, P.I.; Postupaev, V.V.; Shcheglov, M.A.

1998-01-01

This paper presents the results of experiments on two-stage heating of a dense plasma by a relativistic electron beam in the GOL-3 facility. A dense plasma with a length of about a meter and a hydrogen density up to 10 17 cm -3 was created in the main plasma, whose density was 10 15 cm -3 . In the process of interacting with the plasma, the electron beam (1 MeV, 40 kA, 4 μs) imparts its energy to the electrons of the main plasma through collective effects. The heated electrons, as they disperse along the magnetic field lines, in turn reach the region of dense plasma and impart their energy to it by pairwise collisions. Estimates based on experimental data are given for the parameters of the flux of hot plasma electrons, the energy released in the dense plasma, and the energy balance of the beam-plasma system. The paper discusses the dynamics of the plasma, which is inhomogeneous in density and temperature, including the appearance of pressure waves

Heat wave experiments on the W7-AS stellarator

International Nuclear Information System (INIS)

Hartfuss, H.J.; Erckmann, V.; Gasparino, U.; Giannone, L.; Maassberg, H.; Tutter, M.

1993-01-01

Power modulation with well localized ECRH power deposition at both 70 and 140 GHz, has been used to generate temperature perturbations which propagate away from the deposition region. Radiometry of the ECE is used to diagnose the generated temperature perturbation as a function of distance to the deposition zone. The decay of the amplitude and the delay of the wave provide the information to determine the electron thermal diffusivity. This value is then compared with the one derived from a global power balance. It is found that both values agree with the error bars. The technique has also been applied in recent experiments during L-H-mode transitions in W7-AS demonstrating a significant reduction in the effective heat diffusivity in the plasma core during the H-phase. The modulated ECRH causes a modulation of the Shafranov shift. Interference of the prompt shift with the heat wave results in an apparent asymmetry of the decay length of the heat wave with respect to the plasma centre. (orig.)

First-principles calculations of heat capacities of ultrafast laser-excited electrons in metals

International Nuclear Information System (INIS)

Bévillon, E.; Colombier, J.P.; Recoules, V.; Stoian, R.

2015-01-01

Ultrafast laser excitation can induce fast increases of the electronic subsystem temperature. The subsequent electronic evolutions in terms of band structure and energy distribution can determine the change of several thermodynamic properties, including one essential for energy deposition; the electronic heat capacity. Using density functional calculations performed at finite electronic temperatures, the electronic heat capacities dependent on electronic temperatures are obtained for a series of metals, including free electron like, transition and noble metals. The effect of exchange and correlation functionals and the presence of semicore electrons on electronic heat capacities are first evaluated and found to be negligible in most cases. Then, we tested the validity of the free electron approaches, varying the number of free electrons per atom. This shows that only simple metals can be correctly fitted with these approaches. For transition metals, the presence of localized d electrons produces a strong deviation toward high energies of the electronic heat capacities, implying that more energy is needed to thermally excite them, compared to free sp electrons. This is attributed to collective excitation effects strengthened by a change of the electronic screening at high temperature

Impact of nonlocal electron heat transport on the high temperature plasmas of LHD

International Nuclear Information System (INIS)

Tamura, N.; Inagaki, S.; Tokuzawa, T.

2006-10-01

Edge cooling experiments with a tracer-encapsulated solid pellet in the Large Helical Device (LHD) show a significant rise of core electron temperature (the maximum rise is around 1 keV) as well as in many tokamaks. This experimental result indicates the possible presence of the nonlocality of electron heat transport in plasmas where turbulence as a cause of anomalous transport is dominated. The nonlocal electron temperature rise in the LHD takes place in almost the same parametric domain (e.g. in a low density) as in the tokamaks. Meanwhile, the experimental results of LHD show some new aspects of nonlocal electron temperature rise, for example the delay of the nonlocal rise of core electron temperature relative to the pellet penetration time increases with the increase in collisionality in the core plasma and the decrease in electron temperature gradient scale length in the outer region of the plasma. (author)

Impact of nonlocal electron heat transport on the high temperature plasmas of LHD

International Nuclear Information System (INIS)

Tamura, N.; Inagaki, S.; Tanaka, K.; Michael, C.; Tokuzawa, T.; Shimozuma, T.; Kubo, S.; Sakamoto, R.; Ida, K.; Itoh, K.; Kalinina, D.; Sudo, S.; Nagayama, Y.; Kawahata, K.; Komori, A.

2007-01-01

Edge cooling experiments with a tracer-encapsulated solid pellet in the large helical device (LHD) show a significant rise in core electron temperature (the maximum rise is around 1 keV) as well as in many tokamaks. This experimental result indicates the possible presence of the nonlocality of electron heat transport in plasmas where turbulence as a cause of anomalous transport dominates. The nonlocal electron temperature rise in the LHD takes place in almost the same parametric domain (e.g. in a low density) as in the tokamaks. Meanwhile, the experimental results of LHD show some new aspects of nonlocal electron temperature rise, for example the delay in the nonlocal rise of core electron temperature relative to the pellet penetration time increases with the increase both in the collisionality in the core plasma and the electron temperature gradient scale length in the outer region of the plasma

Heating of a plasma by a powerful relativistic electron beam in a strong magnetic field

International Nuclear Information System (INIS)

Arzhannikov, A.V.; Brejzman, B.N.; Vyacheslavov, L.N.; Kojdan, V.S.; Konyukhov, V.V.; Ryutov, D.D.

1975-01-01

The results of an experimental investigation into the interaction of a powerful relativistic electron beam with plasma in the INAR apparatus are presented. The relativistic electron beam had initial energy of 1 MeV, maximum injection current of 10 kA, duration of 70 ns, and diameter of 2 cm. The total beam energy at entry into the plasma was approximately 300 J. The beam was injected into the column of a hydrogen plasma 230 cm long, 8 cm in diameter, and with a density of 3 x 10 14 cm -3 . The magnetic field had mirror-trap geometry (mirror ratio 1.7, intensity in the uniform portion up to 15 kOe). In the experiments, various diagnostic methods were used, making it possible to measure the beam current, the total current within the plasma, the total energy of the beam entering and leaving the plasma, and the distribution of beam current over the cross-section at the plasma outlet; opposing high-energy electrons were recorded. The density of the preliminary plasma was controlled during the experiment; the energy content of the plasma was determined from diamagnetic measurements; the electron distribution function was analysed by the method of Thomson scattering of light at 90deg. From an analysis of the shape of the diamagnetic signals and distribution of diamagnetism along the length of the apparatus it was established that under the assumption of predominant electron heating, the temperature of plasma electrons in order of magnitude equals 1 keV for a plasma density of 5 x 10 13 cm -3 . The cause of heating cannot be dissipation of the reversed current. According to Thomson scattering of laser radiation, the authors established the presence of a comparatively cold plasma component with temperature of 25 eV. High-energy electrons moving from the opposite direction toward the beam were recorded; their appearance evidently was associated with acceleration of plasma electrons in the induction fields. Mechanisms which can provide effective heating of the whole mass of

Electron cyclotron heating and supra-thermal electron dynamics in the TCV Tokamak

Energy Technology Data Exchange (ETDEWEB)

Gnesin, S.

2011-10-15

enhancing its potential for full spectral analysis in high-fluency scenarios. Additional flexibility is afforded by the possibility to rotate the orientation of two of the cameras, permitting the crucial comparison of radiation emitted perpendicular and parallel to the primary magnetic field. The design of the HXR system was optimized through an extensive iterative simulation process with the aid of tomographic reconstruction codes as well as quasilinear Fokker- Planck modeling of ECH-driven TCV plasmas. In parallel, the selection of the detectors for this system was performed through comprehensive laboratory testing of several candidate detectors available on the market. While the design was completed in the course of the thesis work, commissioning of the system has only commenced recently with one of the four cameras installed on TCV. The first preliminary results, discussed in the last part of this thesis, include basic parameter scans of ECH wave-plasma interaction and the investigation of the dynamic response of supra-thermal electrons to modulated ECH. In addition, the cameras possess the novel ability to discriminate against very high-energy γ-ray radiation that cannot be collimated and must thus be excluded from spatial distribution analysis. A basic study of the conditions for γ-ray suppression was conducted in preparation for future experiments. The Fokker-Planck modeling tool used in this diagnostic development was acquired through a collaboration with CEA-Cadarache, initially with the primary motivation of studying the simultaneous plasma heating by 2{sup nd} and 3{sup rd} harmonic electron cyclotron waves that is uniquely possible on TCV. This motivated a dedicated study, both theoretical and experimental, of one particular instance of this combined heating, which became a second primary subject of this thesis work. The particular scenario studied here is one in which a single ECH frequency is resonant at both harmonics in the same plasma. The primary

Electron cyclotron heating and supra-thermal electron dynamics in the TCV Tokamak

International Nuclear Information System (INIS)

Gnesin, S.

2011-10-01

enhancing its potential for full spectral analysis in high-fluency scenarios. Additional flexibility is afforded by the possibility to rotate the orientation of two of the cameras, permitting the crucial comparison of radiation emitted perpendicular and parallel to the primary magnetic field. The design of the HXR system was optimized through an extensive iterative simulation process with the aid of tomographic reconstruction codes as well as quasilinear Fokker- Planck modeling of ECH-driven TCV plasmas. In parallel, the selection of the detectors for this system was performed through comprehensive laboratory testing of several candidate detectors available on the market. While the design was completed in the course of the thesis work, commissioning of the system has only commenced recently with one of the four cameras installed on TCV. The first preliminary results, discussed in the last part of this thesis, include basic parameter scans of ECH wave-plasma interaction and the investigation of the dynamic response of supra-thermal electrons to modulated ECH. In addition, the cameras possess the novel ability to discriminate against very high-energy γ-ray radiation that cannot be collimated and must thus be excluded from spatial distribution analysis. A basic study of the conditions for γ-ray suppression was conducted in preparation for future experiments. The Fokker-Planck modeling tool used in this diagnostic development was acquired through a collaboration with CEA-Cadarache, initially with the primary motivation of studying the simultaneous plasma heating by 2 nd and 3 rd harmonic electron cyclotron waves that is uniquely possible on TCV. This motivated a dedicated study, both theoretical and experimental, of one particular instance of this combined heating, which became a second primary subject of this thesis work. The particular scenario studied here is one in which a single ECH frequency is resonant at both harmonics in the same plasma. The primary objective of this

Electron Heating and Saturation of Self-regulating Magnetorotational Instability in Protoplanetary Disks

Science.gov (United States)

Mori, Shoji; Muranushi, Takayuki; Okuzumi, Satoshi; Inutsuka, Shu-ichiro

2017-11-01

Magnetorotational instability (MRI) has the potential to generatevigorous turbulence in protoplanetary disks, although its turbulence strength and accretion stress remain debatable because of the uncertainty of MRI with a low ionization fraction. We focus on the heating of electrons by strong electric fields, which amplifies nonideal magnetohydrodynamic effects. The heated electrons frequently collide with and stick to dust grains, which in turn decreases the ionization fraction and is expected to weaken the turbulent motion driven by MRI. In order to quantitatively investigate the nonlinear evolution of MRI, including the electron heating, we perform magnetohydrodynamical simulation with the unstratified shearing box. We introduce a simple analytic resistivity model depending on the current density by mimicking the resistivity given by the calculation of ionization. Our simulation confirms that the electron heating suppresses magnetic turbulence when the electron heating occurs with low current density. We find a clear correlation between magnetic stress and current density, which means that the magnetic stress is proportional to the squared current density. When the turbulent motion is completely suppressed, laminar accretion flow is caused by an ordered magnetic field. We give an analytical description of the laminar stateusing a solution of linear perturbation equations with resistivity. We also propose a formula that successfully predicts the accretion stress in the presence of the electron heating.

Electron-cyclotron current drive in the tokamak physics experiment

International Nuclear Information System (INIS)

Smith, G.R.; Kritz, A.H.; Radin, S.H.

1992-01-01

Ray-tracking calculations provide estimates of the electron-cyclotron heating (ECH) power required to suppress tearing modes near the q=2 surface in the Tokamak Physics Experiment. Effects of finite beam width and divergence are included, as are the effects of scattering of the ECH power by drift-wave turbulence. A frequency of about 120 GHz allows current drive on the small-R (high-B) portion of q=2, while 80 GHz drives current on the large-R (low-B) portion. The higher frequency has the advantages of less sensitivity to wave and plasma parameters and of no trapped-electron degradation of current-drive efficiency. Less than 1 MW suffices to suppress tearing modes even with high turbulence levels

Electron heating caused by the ion-acoustic decay instability in a finite-length system

International Nuclear Information System (INIS)

Rambo, P.W.; Woo, W.; DeGroot, J.S.; Mizuno, K.

1984-01-01

The ion-acoustic decay instability is investigated for a finite-length plasma with density somewhat below the cutoff density of the electromagnetic driver (napprox.0.7n/sub c/). For this regime, the heating in a very long system can overpopulate the electron tail and cause linear saturation of the low phase velocity electron plasma waves. For a short system, the instability is nonlinearly saturated at larger amplitude by ion trapping. Absorption can be significantly increased by the large-amplitude ion waves. These results compare favorably with microwave experiments

Numerical analysis of sawtooth oscillation during electron cyclotron heating phases

International Nuclear Information System (INIS)

Wang Shiqing; Jin Yaqiu

2001-01-01

By employing two models, namely the reconnection model and the turbulence model, the authors present a transport code simulation of sawtooth discharges in T-10 Tokamak in the electron cyclotron heating phases, and the trigger conditions are also coupled into the transport code. In one discharge, ECRH was located nearly on-axis, and in another ECRH was located well off-axis. The comparison of numerical results and experiment data show that good prediction was obtained with the turbulence model. In contrast, due to some fundamental shortcoming of the reconnection model, no satisfactory fit could be obtained using the latter

Electron cyclotron heating of plasmas

International Nuclear Information System (INIS)

Guest, Gareth

2009-01-01

As nuclear fusion becomes an increasingly important potential energy source in these times of global oil and energy crises, the development of technologies that can lead to the realization of this virtually inexhaustible source of energy takes on ever greater urgency. Over the past decade electron cyclotron heating has undergone a significant maturation and has emerged as an essential component of the major approaches to achieving controlled nuclear fusion. The gyrotron, first developed in the Soviet Union, has made it possible to employ ECH in large tokamak and stellarator fusion devices by providing megawatts of microwave power at frequencies above 100 GHz. A contemporary VGT-8110 gyrotron, for example, shown here with Kevin Felch and Pat Cahalan of Communications and Power Industries, is capable of delivering 10 second pulses of 1 MW of power at 110 GHz. The present monograph addresses the ECH physics critical to the international fusion reactor experiment, ITER, but also presents the fundamentals of ECH that are essential to its successful implementation in applications that range from active experiments in planetary magnetospheres to commercial plasma sources for the manufacture of computer chips. The book seeks to convey the physics of ECH in an orderly and coherent fashion to a professional audience by presenting the basic theoretical foundations and then using the theory to interpret a number of established experimental results. Exercises are included to aid the reader in making the theory more concrete. (orig.)

Rapid plasma heating by collective interactions, using strong turbulence and relativistic electron beams

International Nuclear Information System (INIS)

Wharton, C.B.

1977-01-01

A multi-kilovolt, moderate density plasma was generated in a magnetic mirror confinement system by two methods: turbulent heating and relativistic electron beam. Extensive diagnostic development permitted the measurement of important plasma characteristics, leading to interesting and novel conclusions regarding heating and loss mechanisms. Electron and ion heating mechanisms were categorized, and parameter studies made to establish ranges of importance. Nonthermal ion and electron energy distributions were measured. Beam propagation and energy deposition studies yielded the spatial dependence of plasma heating

Electron thermal energy transport research based on dynamical relationship between heat flux and temperature gradient

International Nuclear Information System (INIS)

Notake, Takashi; Inagaki, Shigeru; Tamura, Naoki

2008-01-01

In the nuclear fusion plasmas, both of thermal energy and particle transport governed by turbulent flow are anomalously enhanced more than neoclassical levels. Thus, to clarify a relationship between the turbulent flow and the anomalous transports has been the most worthwhile work. There are experimental results that the turbulent flow induces various phenomena on transport processes such as non-linearity, transition, hysteresis, multi-branches and non-locality. We are approaching these complicated problems by analyzing not conventional power balance but these phenomena directly. They are recognized as dynamical trajectories in the flux and gradient space and must be a clue to comprehend a physical mechanism of arcane anomalous transport. Especially, to elucidate the mechanism for electron thermal energy transport is critical in the fusion plasma researches because the burning plasmas will be sustained by alpha-particle heating. In large helical device, the dynamical relationships between electron thermal energy fluxes and electron temperature gradients are investigated by using modulated electron cyclotron resonance heating and modern electron cyclotron emission diagnostic systems. Some trajectories such as hysteresis loop or line segments with steep slope which represent non-linear property are observed in the experiment. (author)

Additional heating experiments of FRC plasmas

International Nuclear Information System (INIS)

Okada, S.; Asai, T.; Kodera, F.; Kitano, K.; Suzuki, T.; Yamanaka, K.; Kanki, T.; Inomoto, M.; Yoshimura, S.; Okubo, M.; Sugimoto, S.; Ohi, S.; Goto, S.

2001-01-01

Additional heating experiments of neutral beam (NB) injection and application of low frequency wave on a plasma with extremely high averaged beta value of about 90% - a field reversed configuration (FRC) plasma - are carried out on the FRC Injection experiment (FIX) apparatus. These experiments are made possible by translating the FRC plasma produced in a formation region of a theta pinch to a confinement region in order to secure better accessibility to heating facilities and to control plasma density. By appropriate choice of injection geometry and the mirror ratio of the confinement region, the NB with the energy of 14keV and the current of 23A is enabled to be injected into the FRC in the solenoidal confining field of only 0.04-0.05T. Confinement is improved by this experiment. Ion heating is observed by the application of low frequency (80kHz ; about 1/4 of the ion gyro frequency) compressional wave. A shear wave, probably mode converted from the compressional wave, is detected to propagate axially. (author)

Numerical simulation of electron behavior and beam heating on a material surface

International Nuclear Information System (INIS)

Shioda, K.; Hashidate, Y.; Kumagai, M.

1991-01-01

A method of numerical analysis is investigated for the manufacturing processes employing electron beam heating, such as hardening, cutting, and welding. High-energy electrons (10 ∼ 50 keV) impinge upon the surface of a material and diffuse by multiple elastic/nonelastic scattering caused by atoms. Although the electron collisions with atomic nuclei can be treated approximately as elastic, collisions with orbital electrons of atoms are nonelastic. Fast electrons are decelerated in the course of atomic excitation or X-ray radiation, transferring their kinetic energy to the lattice system as thermal energy. In this paper, the difference between the heat-generating density and the electron density is clarified numerically, as well as the penetration depth and the reflection ratio of the electron beam. Calculated results for these quantities show good agreement with the referenced data. In addition, the difference between the penetration depth of the electrons and that of the heat, which has never been discussed in detail before, is clarified

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Directory of Open Access Journals (Sweden)

H. Y. Fu

2015-08-01

Full Text Available Observations of secondary radiation, stimulated electromagnetic emission (SEE, produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF radio waves are considered. The High Frequency Active Auroral Research Program (HAARP facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS and stimulated ion Bernstein scatter (SIBS in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

Experiments on FW-IBW mode conversion heating combined with LHCD on Tore Supra

International Nuclear Information System (INIS)

Basiuk, V.; Becoulet, A.; Imbeaux, F.; Nguyen, F.; Peysson, Y.; Monakhov, I.; Petrov, Y.; Petrov, Y.

1999-01-01

Recent RF heating and current drive investigations revealed a growing interest in a scheme based on mode conversion (MC) of externally excited fast waves (FW) to ion Bernstein waves (IBW). Suitability of MC scheme for on/off axis electron heating has already been reported on Tore Supra. New results, which were obtained during MC experiments combined with Low Hybrid Current Drive (LHCD) are presented in this paper. Application of new experimental tools and numerical techniques provided better insight into the problem of MC power deposition. an outcome of active search for synergistic LHCD-IBW current drive effects is also reported

High average power CW FELs [Free Electron Laser] for application to plasma heating: Designs and experiments

International Nuclear Information System (INIS)

Booske, J.H.; Granatstein, V.L.; Radack, D.J.; Antonsen, T.M. Jr.; Bidwell, S.; Carmel, Y.; Destler, W.W.; Latham, P.E.; Levush, B.; Mayergoyz, I.D.; Zhang, Z.X.

1989-01-01

A short period wiggler (period ∼ 1 cm), sheet beam FEL has been proposed as a low-cost source of high average power (1 MW) millimeter-wave radiation for plasma heating and space-based radar applications. Recent calculation and experiments have confirmed the feasibility of this concept in such critical areas as rf wall heating, intercepted beam (''body'') current, and high voltage (0.5 - 1 MV) sheet beam generation and propagation. Results of preliminary low-gain sheet beam FEL oscillator experiments using a field emission diode and pulse line accelerator have verified that lasing occurs at the predicted FEL frequency. Measured start oscillation currents also appear consistent with theoretical estimates. Finally, we consider the possibilities of using a short-period, superconducting planar wiggler for improved beam confinement, as well as access to the high gain, strong pump Compton regime with its potential for highly efficient FEL operation

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

International Nuclear Information System (INIS)

Wilson, J.R.; Bell, R.E.; Bernabei, S.; Bitter, M.; Gates, D.; Hosea, J.; Le Blanc, B.; Medley, S.; Menard, J.; Mueller, D.; Ono, M.; Phillips, C.K.; Rosenberg, A.; Bonoli, P.; Mau, T.K.; Pinsker, R.I.; Raman, R.; Ryan, P.; Swain, D.; Wilgen, J.

2003-01-01

High harmonic fast wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, S. Neumeyer et al., in Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999 (IEEE, Piscataway, NJ, 1999), p. 53] is such a device. An rf heating system has been installed on the NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge

Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment

International Nuclear Information System (INIS)

Wilson, J.R.; Bell, R.E.; Bernabei, S.; Bitter, M.; Bonoli, P.; Gates, D.; Hosea, J.; LeBlanc, B.; Mau, T.K.; Medley, S.; Menard, J.; Mueller, D.; Ono, M.; Phillips, C.K.; Pinsker, R.I.; Raman, R.; Rosenberg, A.; Ryan, P.; Sabbagh, S.; Stutman, D.; Swain, D.; Takase, Y.; Wilgen, J.

2003-01-01

High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge

Large power electron tubes for high frequency heating

International Nuclear Information System (INIS)

Okamoto, Tadashi; Sato, Hisaaki.

1988-01-01

On the large power electron tubes used for electron cyclotron heating, lower hybrid resonance frequency heating, and ion cyclotron range of frequency heating, namely gyrotron, klystron and quadrupole tube, the features, the present status of development, the construction, the principle and so on are explained. The research and development of gyrotrons are most advanced in USSR, the inventor. The course of the development of gyrotrons in foreign countries and in Japan is described. There are many variants of gyrotrons, for example whispering gallery mode, klystron type, backward wave oscillator type, gyro-peniotron and others. The principle of gyrotrons is explained, and about the examples of the developed gyrotrons, the design parameters are shown. For the purpose of using for the LHRF heating in JT-60, a superlarge power klystron of 1 MW output at 2 GHz frequency, which is the largest class in the world, has been developed. Its total length is 2.7 m, and weight is 1.5 t. It features, construction, function and performance are reported. The trend of large power quadrupole tubes is toward stable action with large power in VHF zone, and the typical products in USA and Europe are shown. (Kako, I.)

Electron beam welding of iridium heat source capsules

International Nuclear Information System (INIS)

Mustaleski, T.M.; Yearwood, J.C.; Burgan, C.E.; Green, L.A.

1991-01-01

The development of the welding procedures for the production of DOP-26 iridium alloy cups for heat source encapsulation is described. All the final assembly welds were made using the electron beam welding process. The welding of the 0.13-mm weld shield required the use of computer controlled X-Y table and a run-off tab. Welding of the frit vent to the cup required that a laser weld be made to hold the frit assembly edges together for the final electron beam weld. Great care is required in tooling design and beam placement to achieve acceptable results. Unsuccessful attempts to use laser beam welding for heat shield butt weld are discussed

Hot-electron plasma formation and confinement in the tandem mirror experiment-upgrade

International Nuclear Information System (INIS)

Ress, D.B.

1988-06-01

The tandem mirror experiment-upgrade (TMX-U) at the Lawrence Livermore National Laboratory (LLNL) is the first experiment to investigate the thermal-barrier tandem-mirror concept. One attractive feature of the tandem magnetic mirror as a commercial power reactor is that the fusion reactions occur in an easily accessible center-cell. On the other hand, complicated end-cells are necessary to provide magnetohydrodynamic (MHD) stability and improved particle confinement of the center-cell plasma. In these end-cells, enhanced confinement is achieved with a particular axial potential profile that is formed with electron-cyclotron range-of-frequency heating (ECRF heating, ECRH). By modifying the loss rates of electrons at spatially distinct locations within the end-cells, the ECRH can tailor the plasma potential profile in the desired fashion. Specifically, the thermal-barrier concept requires generation of a population of energetic electrons near the midplane of each end-cell. To be effective, the transverse (to the magnetic field) spatial structure of the hot-electron plasma must be fairly uniform. In this dissertation we characterize the spatial structure of the ECRH-generated plasma, and determine how the structure builds up in time. Furthermore, the plasma should efficiently absorb the ECRF power, and a large fraction of the electrons must be well confined near the end-cell midplane. Therefore, we also examine in detail the ECRH power balance, determining how the ECRF power is absorbed by the plasma, and the processes through which that power is confined and lost. 43 refs., 69 figs., 6 tabs

Experimental and numerical investigation of flow field and heat transfer from electronic components in a rectangular channel with an impinging jet

Directory of Open Access Journals (Sweden)

Calisir Tamer

2015-01-01

Full Text Available Thermal control of electronic components is a continuously emerging problem as power loads keep increasing. The present study is mainly focused on experimental and numerical investigation of impinging jet cooling of 18 (3 × 6 array flash mounted electronic components under a constant heat flux condition inside a rectangular channel in which air, following impingement, is forced to exit in a single direction along the channel formed by the jet orifice plate and impingement plate. Copper blocks represent heat dissipating electronic components. Inlet flow velocities to the channel were measured by using a Laser Doppler Anemometer (LDA system. Flow field observations were performed using a Particle Image Velocimetry (PIV and thermocouples were used for temperature measurements. Experiments and simulations were conducted for Re = 4000 – 8000 at fixed value of H = 10 × Dh. Flow field results were presented and heat transfer results were interpreted using the flow measurement observations. Numerical results were validated with experimental data and it was observed that the results are in agreement with the experiments.

Electron heat conduction and suprathermal particles

International Nuclear Information System (INIS)

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

1991-01-01

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

Electron-beam welding of the grill flanges of the FTU additional heating system

International Nuclear Information System (INIS)

Cucchiaro, A.; Marra, A.

1994-10-01

The research and development program of the fusion sector of ENEA (Italian Agency for New Technologies, Energy and Environment) Frascati center is mainly based on experiments on the Frascati Tokamak Upgrade (FTU) machine. The FTU is a medium-high magnetic field (8 T) tokamak with a radio-frequency (RF) additional heating system (8 MW, 8 GHz) that can heat the plasma to temperatures of fusionistic interest. The RF power is coupled to the plasma by a coupling structure consisting of three grills, each formed of an array of waveguides welded at the terminal flanges by an electron-beam technique. This solution allows highly accurate dimensions and optimum clean-surface conditions of the welded copper joints

Electron Currents and Heating in the Ion Diffusion Region of Asymmetric Reconnection

Science.gov (United States)

Graham, D. B.; Khotyaintsev, Yu. V.; Norgren, C.; Vaivads, A.; Andre, M.; Lindqvist, P. A.; Marklund, G. T.; Ergun, R. E.; Paterson, W. R.; Gershman, D. J.;

Solar heating for an electronics manufacturing plant--Blue Earth, Minnesota

Science.gov (United States)

1981-01-01

Partial space heating for 97,000 square foot plant is supplied by 360 flat plate solar collectors; energy is sorted as heat in indoor 20,000 gallon water tank. System includes all necessary control electronics for year round operation. During December 1978, solar energy supplied 24.4 percent of building's space heating load.

Heat transfer in underground heating experiments in granite, Stipa, Sweden

International Nuclear Information System (INIS)

Chan, T.; Javandel, I.; Witherspoon, P.A.

1980-04-01

Electrical heater experiments have been conducted underground in granite at Stripa, Sweden, to investigate the effects of heating associated with nuclear waste storage. Temperature data from these experiments are compared with closed-form and finite-element solutions. Good agreement is found between measured temperatures and both types of models, but especially for a nonlinear finite-element heat conduction model incorporating convective boundary conditions, measured nonuniform initial rock temperature distribution, and temperature-dependent thermal conductivity. In situ thermal properties, determined by least-squares regression, are very close to laboratory values. A limited amount of sensitivity analysis is undertaken

Electron cyclotron current drive experiments on DIII-D

International Nuclear Information System (INIS)

James, R.A.; Giruzzi, G.; Gentile, B. de; Rodriguez, L.; Fyaretdinov, A.; Gorelov, Yu.; Trukhin, V.; Harvey, R.; Lohr, J.; Luce, T.C.; Matsuda, K.; Politzer, P.; Prater, R.; Snider, R.; Janz, S.

1990-05-01

Electron Cyclotron Current Drive (ECCD) experiments on the DIII-D tokamak have been performed using 60 GHz waves launched from the high field side of the torus. Preliminary analysis indicates rf driven currents between 50 and 100 kA in discharges with total plasma currents between 200 and 500 kA. These are the first ECCD experiments with strong first pass absorption, localized deposition of the rf power, and τ E much longer than the slowing-down time of the rf generated current carriers. The experimentally measured profiles for T e , η e and Z eff are used as input for a 1D transport code and a multiply-ray, 3D ray tracing code. Comparisons with theory and assessment of the influence of the residual electric field, using a Fokker-Planck code, are in progress. The ECH power levels were between 1 and 1.5 MW with pulse lengths of about 500 msec. ECCD experiments worldwide are motivated by issues relating to the physics and technical advantages of the use of high frequency rf waves to drive localized currents. ECCD is accomplished by preferentially heating electrons moving in one toroidal direction, reducing their collisionality and thereby producing a non-inductively driven toroidal current. 6 refs., 4 figs

Electron cyclotron current drive experiments on DIII-D

Energy Technology Data Exchange (ETDEWEB)

James, R.A. (Lawrence Livermore National Lab., CA (USA)); Giruzzi, G.; Gentile, B. de; Rodriguez, L. (Association Euratom-CEA, Centre d' Etudes Nucleaires de Cadarache, 13 - Saint-Paul-les-Durance (France)); Fyaretdinov, A.; Gorelov, Yu.; Trukhin, V. (Kurchatov Inst. of Atomic Energy, Moscow (USSR)); Harvey, R.; Lohr, J.; Luce, T.C.; Matsuda, K.; Politzer, P.; Prater, R.; Snider, R. (General Atomics, San Di

1990-05-01

Electron Cyclotron Current Drive (ECCD) experiments on the DIII-D tokamak have been performed using 60 GHz waves launched from the high field side of the torus. Preliminary analysis indicates rf driven currents between 50 and 100 kA in discharges with total plasma currents between 200 and 500 kA. These are the first ECCD experiments with strong first pass absorption, localized deposition of the rf power, and {tau}{sub E} much longer than the slowing-down time of the rf generated current carriers. The experimentally measured profiles for T{sub e}, {eta}{sub e} and Z{sub eff} are used as input for a 1D transport code and a multiply-ray, 3D ray tracing code. Comparisons with theory and assessment of the influence of the residual electric field, using a Fokker-Planck code, are in progress. The ECH power levels were between 1 and 1.5 MW with pulse lengths of about 500 msec. ECCD experiments worldwide are motivated by issues relating to the physics and technical advantages of the use of high frequency rf waves to drive localized currents. ECCD is accomplished by preferentially heating electrons moving in one toroidal direction, reducing their collisionality and thereby producing a non-inductively driven toroidal current. 6 refs., 4 figs.

Design and Development of a CPCI-Based Electronics Package for Space Station Experiments

Science.gov (United States)

Kolacz, John S.; Clapper, Randy S.; Wade, Raymond P.

2006-01-01

The NASA John H. Glenn Research Center is developing a Compact-PCI (CPCI) based electronics package for controlling space experiment hardware on the International Space Station. Goals of this effort include an easily modified, modular design that allows for changes in experiment requirements. Unique aspects of the experiment package include a flexible circuit used for internal interconnections and a separate enclosure (box in a box) for controlling 1 kW of power for experiment fuel heating requirements. This electronics package was developed as part of the FEANICS (Flow Enclosure Accommodating Novel Investigations in Combustion of Solids) mini-facility which is part of the Fluids and Combustion Facility s Combustion Integrated Rack (CIR). The CIR will be the platform for future microgravity combustion experiments and will reside on the Destiny Module of the International Space Station (ISS). The FEANICS mini-facility will be the primary means for conducting solid fuel combustion experiments in the CIR on ISS. The main focus of many of these solid combustion experiments will be to conduct applied scientific investigations in fire-safety to support NASA s future space missions. A description of the electronics package and the results of functional testing are the subjects of this report. The report concludes that the use of innovative packaging methods combined with readily available COTS hardware can provide a modular electronics package which is easily modified for changing experiment requirements.

Electron-phonon heat exchange in quasi-two-dimensional nanolayers

Science.gov (United States)

Anghel, Dragos-Victor; Cojocaru, Sergiu

2017-12-01

We study the heat power P transferred between electrons and phonons in thin metallic films deposited on free-standing dielectric membranes. The temperature range is typically below 1 K, such that the wavelengths of the excited phonon modes in the system is large enough so that the picture of a quasi-two-dimensional phonon gas is applicable. Moreover, due to the quantization of the components of the electron wavevectors perpendicular to the metal film's surface, the electrons spectrum forms also quasi two-dimensional sub-bands, as in a quantum well (QW). We describe in detail the contribution to the electron-phonon energy exchange of different electron scattering channels, as well as of different types of phonon modes. We find that heat flux oscillates strongly with thickness of the film d while having a much smoother variation with temperature (Te for the electrons temperature and Tph for the phonons temperature), so that one obtains a ridge-like landscape in the two coordinates, (d, Te) or (d, Tph), with crests and valleys aligned roughly parallel to the temperature axis. For the valley regions we find P ∝ Te3.5 - Tph3.5. From valley to crest, P increases by more than one order of magnitude and on the crests P cannot be represented by a simple power law. The strong dependence of P on d is indicative of the formation of the QW state and can be useful in controlling the heat transfer between electrons and crystal lattice in nano-electronic devices. Nevertheless, due to the small value of the Fermi wavelength in metals, the surface imperfections of the metallic films can reduce the magnitude of the oscillations of P vs. d, so this effect might be easier to observe experimentally in doped semiconductors.

Nonlinear charge transport in bipolar semiconductors due to electron heating

International Nuclear Information System (INIS)

Molina-Valdovinos, S.; Gurevich, Yu.G.

2016-01-01

It is known that when strong electric field is applied to a semiconductor sample, the current voltage characteristic deviates from the linear response. In this letter, we propose a new point of view of nonlinearity in semiconductors which is associated with the electron temperature dependence on the recombination rate. The heating of the charge carriers breaks the balance between generation and recombination, giving rise to nonequilibrium charge carriers concentration and nonlinearity. - Highlights: • A new mechanism of nonlinearity of current-voltage characteristic (CVC) is proposed. • The hot electron temperature violates the equilibrium between electrons and holes. • This violation gives rise to nonequilibrium concentration of electrons and holes. • This leads to nonlinear CVC (along with the heating nonlinearity).

Nonlinear charge transport in bipolar semiconductors due to electron heating

Energy Technology Data Exchange (ETDEWEB)

Molina-Valdovinos, S., E-mail: sergiom@fisica.uaz.edu.mx [Universidad Autónoma de Zacatecas, Unidad Académica de Física, Calzada Solidaridad esq. Paseo, La Bufa s/n, CP 98060, Zacatecas, Zac, México (Mexico); Gurevich, Yu.G. [Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física, Av. IPN 2508, México D.F., CP 07360, México (Mexico)

2016-05-27

It is known that when strong electric field is applied to a semiconductor sample, the current voltage characteristic deviates from the linear response. In this letter, we propose a new point of view of nonlinearity in semiconductors which is associated with the electron temperature dependence on the recombination rate. The heating of the charge carriers breaks the balance between generation and recombination, giving rise to nonequilibrium charge carriers concentration and nonlinearity. - Highlights: • A new mechanism of nonlinearity of current-voltage characteristic (CVC) is proposed. • The hot electron temperature violates the equilibrium between electrons and holes. • This violation gives rise to nonequilibrium concentration of electrons and holes. • This leads to nonlinear CVC (along with the heating nonlinearity).

Study of the electron heat transport in Tore-Supra tokamak

International Nuclear Information System (INIS)

Harauchamps, E.

2004-01-01

This work presents analytical solutions to the electron heat transport equation involving a damping term and a convection term in a cylindrical geometry. These solutions, processed by Matlab, allow the determination of the evolution of the radial profile of electron temperature in tokamaks during heating. The modulated injection of waves around the electron cyclotron frequency is an efficient tool to study heat transport experimentally in tokamaks. The comparison of these analytical solutions with experimental results from Tore-Supra during 2 discharges (30550 and 31165) shows the presence of a sudden change for the diffusion and damping coefficients. The hypothesis of the presence of a pinch spread all along the plasma might explain the shape of the experimental temperature profiles. These analytical solutions could be used to determine the time evolution of plasma density as well or of any parameter whose evolution is governed by a diffusion-convection equation. (A.C.)

An electron-beam-heating model for the Gamble II rod pinch

International Nuclear Information System (INIS)

Mosher, David; Schumer, Joseph; Hinshelwood, David; Weber, Bruce; Stephanakis, Stavros; Swanekamp, Stephen; Young, Frank

2002-01-01

The rod-pinch diode concentrates electron deposition onto the tip of a high-atomic-number, mm-dia. anode rod to create an ultra-bright x-ray source for multi-MV radiography. Here, a technique is presented whereby line-spread functions acquired on-axis and at 90 deg. to the rod are used to determine the electron-deposition distribution. Results show that the smaller measured on-axis spot size for heated rods on Gamble II is due to pinching closer to the tapered tip. For a diode power of 6x1010 W, peak electron heating of 1x1014 W/cm 3 is calculated. MHD calculations of the e-beam-heated rod response agree with Schlieren measurements of plasma expansion

Electron heat flux instabilities in the solar wind

International Nuclear Information System (INIS)

Gary, S.P.; Feldman, W.C.; Forslund, D.W.; Montgomery, M.D.

1975-01-01

There are at least three plasma instabilities associated with the electron heat flux in the solar wind. This letter reports the study of the unstable fast magnetosonic, Alfven and whistler modes via a computer code which solves the full electromagnetic, linear, Vlasov dispersion relation. Linear theory demonstrates that both the magnetosonic and Alfven instabilities are candidates for turbulent limitation of the heat flux in the solar wind at 1 A.U

Electronics for LHC Experiments

Energy Technology Data Exchange (ETDEWEB)

NONE

2004-07-01

This document gathers the abstracts of most presentations made at this workshop on electronics for the large hadron collider (LHC) experiments. The presentations were arranged into 6 sessions: 1) electronics for tracker, 2) trigger electronics, 3) detector control systems, 4) data acquisition, 5) electronics for calorimeters and electronics for muons, and 6) links, power systems, grounding and shielding, testing and quality assurance.

Electronics for LHC Experiments

International Nuclear Information System (INIS)

2004-01-01

This document gathers the abstracts of most presentations made at this workshop on electronics for the large hadron collider (LHC) experiments. The presentations were arranged into 6 sessions: 1) electronics for tracker, 2) trigger electronics, 3) detector control systems, 4) data acquisition, 5) electronics for calorimeters and electronics for muons, and 6) links, power systems, grounding and shielding, testing and quality assurance

Electron acceleration observed by the FAST satellite within the IAR during a 3 Hz modulated EISCAT heater experiment

Directory of Open Access Journals (Sweden)

S. R. Cash

2002-09-01

Full Text Available A quantitative analysis is presented of the FAST satellite electric field and particle flux data during an EISCAT heating experiment run on 8 October 1998. Radio frequency heating, modulated at 3 Hz, launched ULF waves from the ionosphere into the lower magnetosphere. The ULF waves were observed in FAST data and constituted the first satellite detection of artificially excited Alfvénic ULF waves. The downward electron flux data for this event contain the first observations of electrons undergoing acceleration within the Ionospheric Alfvén Resonator (IAR due to parallel electric fields associated with an artificially stimulated Alfvén wave. The time history and spectral content of the observed down-ward electron fluxes is investigated by considering the effects of a localised parallel electric field. Furthermore, it is demonstrated that a power law electron energy distribution describes the time-variable observed fluxes better than a Maxwellian distribution.Key words. Ionosphere (active experiments; particle acceleration – Magnetospheric physics (electric fields

Electron acceleration observed by the FAST satellite within the IAR during a 3 Hz modulated EISCAT heater experiment

Directory of Open Access Journals (Sweden)

S. R. Cash

Full Text Available A quantitative analysis is presented of the FAST satellite electric field and particle flux data during an EISCAT heating experiment run on 8 October 1998. Radio frequency heating, modulated at 3 Hz, launched ULF waves from the ionosphere into the lower magnetosphere. The ULF waves were observed in FAST data and constituted the first satellite detection of artificially excited Alfvénic ULF waves. The downward electron flux data for this event contain the first observations of electrons undergoing acceleration within the Ionospheric Alfvén Resonator (IAR due to parallel electric fields associated with an artificially stimulated Alfvén wave. The time history and spectral content of the observed down-ward electron fluxes is investigated by considering the effects of a localised parallel electric field. Furthermore, it is demonstrated that a power law electron energy distribution describes the time-variable observed fluxes better than a Maxwellian distribution.

Key words. Ionosphere (active experiments; particle acceleration – Magnetospheric physics (electric fields

Cooling of high-density and power electronics by means of heat pipes

International Nuclear Information System (INIS)

Hubbeling, L.

1980-06-01

This report describes how heat pipes can be used for cooling modern electronic equipment, with numerous advantages over air-cooled systems. A brief review of heat-pipe properties is given, with a detailed description of a functioning prototype. This is a single-width CAMAC unit containing high-density electronic circuits cooled by three heat pipes, and allowing a dissipation of over 120 W instead of the normal maximum of 20 W. (orig.)

The role of electron heat flux in guide-field magnetic reconnection

International Nuclear Information System (INIS)

Hesse, Michael; Kuznetsova, Masha; Birn, Joachim

2004-01-01

A combination of analytical theory and particle-in-cell simulations are employed in order to investigate the electron dynamics near and at the site of guide field magnetic reconnection. A detailed analysis of the contributions to the reconnection electric field shows that both bulk inertia and pressure-based quasiviscous processes are important for the electrons. Analytic scaling demonstrates that conventional approximations for the electron pressure tensor behavior in the dissipation region fail, and that heat flux contributions need to be accounted for. Based on the evolution equation of the heat flux three tensor, which is derived in this paper, an approximate form of the relevant heat flux contributions to the pressure tensor is developed, which reproduces the numerical modeling result reasonably well. Based on this approximation, it is possible to develop a scaling of the electron current layer in the central dissipation region. It is shown that the pressure tensor contributions become important at the scale length defined by the electron Larmor radius in the guide magnetic field

Reversible electron heating vs. wave-particle interactions in quasi-perpendicular shocks

Science.gov (United States)

Veltri, P.; Mangeney, A.; Scudder, J. D.

1992-01-01

The energy necessary to explain the electron heating in quasi-perpendicular collisionless shocks can be derived either from the electron acceleration in the d.c. cross shock electric potential, or by the interactions between the electrons and the waves existing in the shock. A Monte Carlo simulation has been performed to study the electron distribution function evolution through the shock structure, with and without particle diffusion on waves. This simulation has allowed us to clarify the relative importance of the two possible energy sources; in particular it has been shown that the electron parallel temperature is determined by the d.c. electromagnetic field and not by any wave-particle-induced heating. Wave particle interactions are effective in smoothing out the large gradients in phase space produced by the 'reversible' motion of the electrons, thus producing a 'cooling' of the electrons.

Electron cyclotron heating for current profile control of non-circular plasmas

International Nuclear Information System (INIS)

Chan, V.S.; Davidson, R.; Guest, G.; Hacker, M.; Miller, L.

1981-01-01

Electron Cyclotron Heating (ECH) offers a promising approach to modifying the radial profiles of electron temperature and plasma current in tokamaks to increase the ideal MHD beta limits and permit experimental access to particular noncircular cross-section tokamaks that cannot be achieved with the peaked current profiles characteristic of ohmically heated tokamaks. We use a one-and-one-half-dimensional, time-dependent transport model that incorporates a self-consistent model of electron cyclotron power absorption to study the temporal evolution of electron temperature and plasma current profiles and the resulting noncircular equilibria. Startup scenarios for high-beta dees and doublets are investigated with this transport modeling

Cornish heat transfer experiment - final report

International Nuclear Information System (INIS)

Bourke, P.J.; Hodgkinson, D.P.

1985-01-01

The transfer of heat released in an in-site heating experiment simulating high level radioactive waste packages in granite in Cornwall has been found to be mainly by conduction but some appreciable convection does occur. Interim analysis of the data suggests that the latter may account for about 20% of the total. (author)

Demonstration of Electron Bernstein Wave Heating in a Reversed Field Pinch

Science.gov (United States)

Seltzman, Andrew H.

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

Understanding Solar Coronal Heating through Atomic and Plasma Physics Experiments

Science.gov (United States)

Savin, Daniel Wolf; Arthanayaka, Thusitha; Bose, Sayak; Hahn, Michael; Beiersdorfer, Peter; Brown, Gregory V.; Gekelman, Walter; Vincena, Steve

2017-08-01

Recent solar observations suggest that the Sun's corona is heated by Alfven waves that dissipate at unexpectedly low heights in the corona. These observations raise a number of questions. Among them are the problems of accurately quantifying the energy flux of the waves and that of describing the physical mechanism that leads to the wave damping. We are performing laboratory experiments to address both of these issues.The energy flux depends on the electron density, which can be measured spectroscopically. However, spectroscopic density diagnostics have large uncertainties, because they depend sensitively on atomic collisional excitation, de-excitation, and radiative transition rates for multiple atomic levels. Essentially all of these data come from theory and have not been experimentally validated. We are conducting laboratory experiments using the electron beam ion trap (EBIT) at Lawrence Livermore National Laboratory that will provide accurate empirical calibrations for spectroscopic density diagnostics and which will also help to guide theoretical calculations.The observed rapid wave dissipation is likely due to inhomogeneities in the plasma that drive flows and currents at small length scales where energy can be more efficiently dissipated. This may take place through gradients in the Alfvén speed along the magnetic field, which causes wave reflection and generates turbulence. Alternatively, gradients in the Alfvén speed across the field can lead to dissipation through phase-mixing. Using the Large Plasma Device (LAPD) at the University of California Los Angeles, we are studying both of these dissipation mechanisms in the laboratory in order to understand their potential roles in coronal heating.

Laser ablation under different electron heat conduction models in inertial confinement fusion

Science.gov (United States)

Li, Shuanggui; Ren, Guoli; Huo, Wen Yi

2018-06-01

In this paper, we study the influence of three different electron heat conduction models on the laser ablation of gold plane target. Different from previous studies, we concentrate on the plasma conditions, the conversion efficiency from laser into soft x rays and the scaling relation of mass ablation, which are relevant to hohlraum physics study in indirect drive inertial confinement fusion. We find that the simulated electron temperature in corona region is sensitive to the electron heat conduction models. For different electron heat conduction models, there are obvious differences in magnitude and spatial profile of electron temperature. For the flux limit model, the calculated conversion efficiency is sensitive to flux limiters. In the laser ablation of gold, most of the laser energies are converted into x rays. So the scaling relation of mass ablation rate is quite different from that of low Z materials.

Microwave Tokamak Experiment

International Nuclear Information System (INIS)

Anon.

1988-01-01

The Microwave Tokamak Experiment, now under construction at the Laboratory, will use microwave heating from a free-electron laser. The intense microwave pulses will be injected into the tokamak to realize several goals, including a demonstration of the effects of localized heat deposition within magnetically confined plasma, a better understanding of energy confinement in tokamaks, and use of the new free-electron laser technology for plasma heating. The experiment, soon to be operational, provides an opportunity to study dense plasmas heated by powers unprecedented in the electron-cyclotron frequency range required by the especially high magnetic fields used with the MTX and needed for reactors. 1 references, 5 figures, 3 tables

Stable solutions of nonlocal electron heat transport equations

International Nuclear Information System (INIS)

Prasad, M.K.; Kershaw, D.S.

1991-01-01

Electron heat transport equations with a nonlocal heat flux are in general ill-posed and intrinsically unstable, as proved by the present authors [Phys. Fluids B 1, 2430 (1989)]. A straightforward numerical solution of these equations will therefore lead to absurd results. It is shown here that by imposing a minimal set of constraints on the problem it is possible to arrive at a globally stable, consistent, and energy conserving numerical solution

Electronic specific heat of transition metal carbides

International Nuclear Information System (INIS)

Conte, R.

1964-07-01

The experimental results that make it possible to define the band structure of transition metal carbides having an NaCI structure are still very few. We have measured the electronic specific heat of some of these carbides of varying electronic concentration (TiC, either stoichiometric or non-stoichiometric, TaC and mixed (Ti, Ta) - C). We give the main characteristics (metallography, resistivity, X-rays) of our samples and we describe the low temperature specific heat apparatus which has been built. In one of these we use helium as the exchange gas. The other is set up with a mechanical contact. The two use a germanium probe for thermometer. The measurement of the temperature using this probe is described, as well as the various measurement devices. The results are presented in the form of a rigid band model and show that the density of the states at the Fermi level has a minimum in the neighbourhood of the group IV carbides. (author) [fr

Millimeter wave free electron laser amplifiers: Experiments and designs

International Nuclear Information System (INIS)

Bidwell, S.W.; Zhang, Z.X.; Antonsen, T.M. Jr.; Bensen, D.M.; Destler, W.W.; Granatstein, V.L.; Lantham, P.E.; Levush, B.; Rodgers, J.

1991-01-01

Free electron laser amplifies are investigated as sources of high- average-power (1 MW) millimeter to submillimeter wave radiation (200 GHz - 600 GHz) for application to electron cyclotron resonance heating of magnetically confined fusion plasmas. As a stepping-stone to higher frequencies and cw operation a pulsed amplifier (τ pulse ≅ 80 ns) at 98 GHz is being developed. Status is reported on this experiment which investigates linear gain amplification with use of sheet electron beam (transverse cross section = 0.1 cm x 2.0 cm, V beam = 440 keV, I beam ≅ 10 A) and short-period wiggler (ell w = 0.96 cm) and with expected output of 140 W. Predictions of gain and efficiency from a 1-D universal formulation are presented. Beam propagation results, with wiggler focusing as a means of sheet beam confinement in both transverse dimensions, through the 54 cm (56 period) pulsed electromagnet wiggler are discussed. Peak wiggler fields of 5.1 kG on-axis have been achieved

Anomalous heat evolution of deuteron implanted Al on electron bombardment

International Nuclear Information System (INIS)

Kamada, K.; Kinoshita, H.; Takahashi, H.

1994-05-01

Anomalous heat evolution was observed in deuteron implanted Al foils on 175 keV electron bombardment. Local regions with linear dimension of several 100nm showed simultaneous transformation from single crystalline to polycrystalline structure instantaneously on the electron bombardment, indicating the temperature rise up to more than melting point of Al from room temperature. The amount of energy evolved was more than 180 MeV for each transformed region. The transformation was never observed in proton implanted Al foils. The heat evolution was considered due to a nuclear reaction in D 2 molecular collections. (author)

ICRF heating experiments on JIPP T-II

International Nuclear Information System (INIS)

Ichimura, M.; Fujita, J.; Hirokura, S.

1983-10-01

Data of JIPP T-II ICRF heating experiments are presented. The experiment covers three typical cases: the low concentration hydrogen minority case, the high concentration hydrogen minority case, and the 3 He minority case. The best heating efficiency is obtained for the 3 Heminority case. It is shown through power balance analysis that the two H-minority cases are different in the wave energy deposition profile. The difference is explained by the presence of local cavity mode for the high concentration minority case. The ion temperature stops rising at the power density level of 0.65 W/cm 3 . An analytic solution of the Fokker-Planck equation is derived to interpret the deterioration of heating efficiency. (author)

Combined Steady-State and Dynamic Heat Exchanger Experiment

Science.gov (United States)

Luyben, William L.; Tuzla, Kemal; Bader, Paul N.

2009-01-01

This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…

Fundamental experiment of potassium heat exchanger using principle of heat pipe

International Nuclear Information System (INIS)

Sumida, Isao; Kotani, Koichi

1976-01-01

In order to provide compact and reliable sodium equipments including a steam generator, performance tests are conducted with a potassium heat exchanger, which is featured by the separate construction of primary and secondary coolant systems. A small amount of potassium plays a role as an intermediate media of heat transportation between these two coolant systems. Heat is transferred by evaporation and condensation of potassium on the surface of the primary and the secondary coolant pipings, respectively. The tests are performed in the temperature range of 200 -- 300 0 C and the maximum heat transfer reaches 1.3kW (heat transfer rate at the primary heating source: 8.6W/cm 2 at 300 0 C). The experimental results are analyzed by using Langmuir's and Schrage's equation and close agreement between experiment and theory is obtained. (auth.)

Adiabatic theory of nonlinear electron cyclotron resonance heating

International Nuclear Information System (INIS)

Kotel'nikov, I.A.; Stupakov, G.V.

1989-01-01

Plasma heating at electron frequency by an ordinary wave propagating at right angle to unidirectional magnetic field is treated. Injected microwave power is assumed to be so large that relativistic change of electron gyrofrequency during one flight thorugh the wave beam is much greater than inverse time of flight. The electron motion in the wave field is described using Hamiltonian formalism in adiabatic approximation. It is shown that energy coupling from the wave to electrons is due to a bifurcation of electron trajectory which results in a jumpm of the adiabatic invariant. The probability of bifurcational transition from one trajectory to another is calculated analytically and is used for the estimation of the beam power absorbed in plasma. 6 refs.; 2 figs

Electron cyclotron heating and current drive approach for low-temperature startup plasmas using O-X-EBW mode conversion

International Nuclear Information System (INIS)

Batchelor, D.B.; Bigelow, T.S.

1997-01-01

A mechanism for heating and driving currents in very overdense plasmas is considered based on a double-mode conversion: Ordinary mode to Extraordinary mode to electron Bernstein wave. The possibility of using this mechanism for plasma buildup and current ramp in the National Spherical Torus Experiment is investigated

Microwave free-electron laser applications for electron cyclotron heating of plasmas

International Nuclear Information System (INIS)

Thomassen, K.

1990-01-01

Millimeter wave power may be the ideal source of heat for the plasma, but advances in technology are needed to meet requirements of next generation fusion devices. Free electron lasers (FEL) are one candidate for such sources, and this paper reviews the progress, issues of physics and technology, and potential benefits for fusion from these devices

Investigation of Heat Sink Efficiency for Electronic Component Cooling Applications

DEFF Research Database (Denmark)

Staliulionis, Ž.; Zhang, Zhe; Pittini, Riccardo

2014-01-01

Research and optimisation of cooling of electronic components using heat sinks becomes increasingly important in modern industry. Numerical methods with experimental real-world verification are the main tools to evaluate efficiency of heat sinks or heat sink systems. Here the investigation...... of relatively simple heat sink application is performed using modeling based on finite element method, and also the potential of such analysis was demonstrated by real-world measurements and comparing obtained results. Thermal modeling was accomplished using finite element analysis software COMSOL and thermo...

Stochastic heating in the cyclotron resonance of electrons

International Nuclear Information System (INIS)

Gutierrez T, C.; Hernandez A, O.

1999-01-01

The study of the different schemes of plasma heating by radiofrequency waves is a very actual problem related with the plasma heating in different machines and the particle acceleration mechanisms. In this work, it is obtained the expression for the temporal evolution of the energy absorbed in the cyclotron resonance of electrons where it is showed the stochastic character of the energy absorption. It is obtained the stochastic criteria in a magnetic configuration of an Ecr type plasma source. (Author)

Heating of a plasma by a powerful relativistic electron beam in a strong magnetic field

International Nuclear Information System (INIS)

Arzhannikov, A.V.; Brejzman, B.N.; Vyacheslavov, L.N.; Kojdan, V.S.; Konyukhov, V.V.; Ryutov, D.D.

1975-01-01

The results of an experimental investigation into the interaction of a powerful relativistic electron beam with plasma in the INAR apparatus are presented. The relativistic electron beam had initial energy of 1 MeV, maximum injection current of 10 kA, duration of 70 ns, and diameter of 2 cm. The total beam energy at entry into the plasma was approximately 300 J. The beam was injected into the column of a hydrogen plasma 230 cm long, 8 cm in diameter, and with a density of 3x10 14 cm -3 . The magnetic field had mirror-trap geometry (mirror ratio 1.7, intensity in the uniform region up to 15 kOe). In the experiments various diagnostic methods were used, making it possible to measure the beam current, the total current within the plasma, the total energy of the beam entering and leaving the plasma, and the distribution of beam current over the cross-section at the plasma outlet; the energy content of the plasma was determined from diamagnetic measurements; the electron distribution function was analysed by the method of Thomson scattering of light at 90 0 . From an analysis of the shape of the diamagnetic signals and distribution of diamagnetism along the length of the apparatus it was established that under the assumption of predominant electron heating, the temperature of plasma electrons in order of magnitude equals 1 keV for a plasma density of 5x10 13 cm -3 . The cause of heating cannot be dissipation of the reversed current. Thomson scattering of laser radiation indicated the presence of a comparatively cold plasma component with a temperature of 25 eV. High-energy electrons moving from the opposite direction toward the beam were recorded; their appearance evidently was associated with acceleration of plasma electrons in the induction fields. Mechanisms which can provide effective heating of the whole mass of electrons under conditions in which pair collisions are minor are indicated. (author)

Impact of plasma triangularity and collisionality on electron heat transport in TCV L-mode plasmas

International Nuclear Information System (INIS)

Camenen, Y.; Pochelon, A.; Behn, R.; Bottino, A.; Bortolon, A.; Coda, S.; Karpushov, A.; Sauter, O.; Zhuang, G.

2007-01-01

The impact of plasma shaping on electron heat transport is investigated in TCV L-mode plasmas. The study is motivated by the observation of an increase in the energy confinement time with decreasing plasma triangularity which may not be explained by a change in the temperature gradient induced by changes in the geometry of the flux surfaces. The plasma triangularity is varied over a wide range, from positive to negative values, and various plasmas conditions are explored by changing the total electron cyclotron (EC) heating power and the plasma density. The mid-radius electron heat diffusivity is shown to significantly decrease with decreasing triangularity and, for similar plasma conditions, only half of the EC power is required at a triangularity of -0.4 compared with +0.4 to obtain the same temperature profile. Besides, the observed dependence of the electron heat diffusivity on the electron temperature, electron density and effective charge can be grouped in a unique dependence on the plasma effective collisionality. In summary, the electron heat transport level exhibits a continuous decrease with decreasing triangularity and increasing collisionality. Local gyro-fluid and global gyro-kinetic simulations predict that trapped electron modes are the most unstable modes in these EC heated plasmas with an effective collisionality ranging from 0.2 to 1. The modes stability dependence on the plasma triangularity is investigated

Electron and ion heating by whistler turbulence: Three-dimensional particle-in-cell simulations

International Nuclear Information System (INIS)

Hughes, R. Scott; Gary, S. Peter; Wang, Joseph

2014-01-01

Three-dimensional particle-in-cell simulations of decaying whistler turbulence are carried out on a collisionless, homogeneous, magnetized, electron-ion plasma model. In addition, the simulations use an initial ensemble of relatively long wavelength whistler modes with a broad range of initial propagation directions with an initial electron beta β e = 0.05. The computations follow the temporal evolution of the fluctuations as they cascade into broadband turbulent spectra at shorter wavelengths. Three simulations correspond to successively larger simulation boxes and successively longer wavelengths of the initial fluctuations. The computations confirm previous results showing electron heating is preferentially parallel to the background magnetic field B o , and ion heating is preferentially perpendicular to B o . The new results here are that larger simulation boxes and longer initial whistler wavelengths yield weaker overall dissipation, consistent with linear dispersion theory predictions of decreased damping, stronger ion heating, consistent with a stronger ion Landau resonance, and weaker electron heating

Fabrication experiments for large helix heat exchangers

International Nuclear Information System (INIS)

Burgsmueller, P.

1978-01-01

The helical tube has gained increasing attention as a heat transfer element for various kinds of heat exchangers over the last decade. Regardless of reactor type and heat transport medium, nuclear steam generators of the helix type are now in operation, installlation, fabrication or in the project phase. As a rule, projects are based on the extrapolation of existing technologies. In the particlular case of steam generators for HTGR power stations, however, existing experience is with steam generators of up to about 2 m diameter whereas several projects involve units more than twice as large. For this reason it was felt that a fabrication experiment was necessary in order to verify the feasibility of modern steam generator designs. A test rig was erected in the SULZER steam generator shops at Mantes, France, and skilled personnel and conventional production tools were employed in conducting experiments relating to the coiling, handling and threading of large helices. (Auth.)

Empirical scaling for present ohmic heated tokamaks

International Nuclear Information System (INIS)

Daughney, C.

1975-06-01

Empirical scaling laws are given for the average electron temperature and electron energy confinement time as functions of plasma current, average electron density, effective ion charge, toroidal magnetic field, and major and minor plasma radius. The ohmic heating is classical, and the electron energy transport is anomalous. The present scaling indicates that ohmic-heating becomes ineffective with larger experiments. (U.S.)

Electron heating of voltage-driven and matched dual frequency discharges

International Nuclear Information System (INIS)

Lieberman, M A; Lichtenberg, A J

2010-01-01

In a dual frequency capacitive sheath, a high frequency uniform sheath motion is coupled with a low frequency Child law sheath motion. For current-driven high and low frequency sheaths, the high frequency sheath motion generates most of the ohmic and stochastic heating of the discharge electrons. The low frequency motion, in addition to its primary purpose of establishing the ion bombarding energy, also increases the heating by widening the sheath width and transporting the oscillating electrons to regions of lower plasma density, and hence higher sheath velocity. In this work, we show that for voltage-driven high and low frequency sheaths, increasing the low frequency voltage reduces the heating, due to the reduced high frequency current that flows through the sheath under voltage-driven conditions. We determine the dependence of the heating on various parameters and compare the results with the current-driven case. Particle-in-cell simulations are used to confirm this result. Discharges generally employ a matching network to maximize the power transmitted to the plasma. We obtain analytic expressions for the effect of the low frequency source under matched conditions and, again, find that the low frequency source reduces the heating.

Experimental measurements of deep directional columnar heating by laser-generated relativistic electrons at near-solid density

International Nuclear Information System (INIS)

Koch, J.A.; Key, M.H.; Hatchett, S.P.; Lee, R.W.; Pennington, D.; Tabak, M.; Freeman, R.R.; Stephens, R.B.

2002-01-01

In our experiments, we irradiated solid CH targets with a 400 J, 5 ps, 3x10 19 W/cm 2 laser, and we used x-ray imaging and spectroscopic diagnostics to monitor the keV x-ray emission from thin Al or Au tracer layers buried within the targets. The experiments were designed to quantify the spatial distribution of the thermal electron temperature and density as a function of buried layer depth; these data provide insights into the behavior of relativistic electron currents which flow within the solid target and are directly and indirectly responsible for the heating. We measured ∼200-350 eV temperatures and near-solid densities at depths ranging from 5 to 100 μm beneath the target surface. Time-resolved x-ray spectra from Al tracers indicate that the tracers emit thermal x rays and cool slowly compared to the time scale of the laser pulse. Most intriguingly, we consistently observe annular x-ray images in all buried tracer-layer experiments, and these data show that the temperature distribution is columnar, with enhanced heating along the edges of the column. The ring diameters are much greater than the laser focal spot diameter and do not vary significantly with the depth of the tracer layer for depths greater than 30 μm. The local temperatures are 200-350 eV for all tracer depths. We discuss recent simulations of the evolution of electron currents deep within solid targets irradiated by ultra-high-intensity lasers, and we discuss how modeling and analytical results suggest that the annular patterns we observe may be related to locally strong growth of the Weibel instability. We also suggest avenues for future research in order to further illuminate the complex physics of relativistic electron transport and energy deposition inside ultra-high-intensity laser-irradiated solid targets

Microwave free-electron laser applications for electron cyclotron heating of plasmas

International Nuclear Information System (INIS)

Thomassen, K.I.

1990-01-01

Millimeter wave power may be the ideal source of heat for a plasma, but advances in technology are needed to meet requirements of next generation fusion devices. Free electron lasers (FEL) are one candidate for such sources, and this paper reviews the progress, issues of physics and technology, and potential benefits for fusion from these devices. 15 refs., 13 figs

Control Mechanisms of the Electron Heat Flux in the Solar Wind: Observations in Comparison to Numerical Simulations

Science.gov (United States)

Stverak, S.; Hellinger, P.; Landi, S.; Travnicek, P. M.; Maksimovic, M.

2017-12-01

Recent understanding of the heat transport and dissipation in the expanding solar wind propose number of complex control mechanisms down to the electron kinetic scales. We investigate the evolution of electron heat flux properties and constraints along the expansion using in situ observations from Helios spacecraft in comparison to numerical kinetic simulations. In particular we focus on the roles of Coulomb collisions and wave-particle interactions in shaping the electron velocity distribution functions and thus controlling the heat transported by the electron heat flux. We show the general evolution of the electron heat flux to be driven namely by the Coulomb collisions. Locally we demonstrate the wave-particle interactions related to the kinetic plasma instabilities to be providing effective constraints in case of extreme heat flux levels.

Balmer line diagnostic of electron heating at collisionless shocks in supernova remnants

International Nuclear Information System (INIS)

Rakowski, C.

2008-01-01

The mechanism and extent of electron heating at collisionless shocks has recently been under intense investigation. H α Balmer line emission is excited immediately behind the shock front and provides the best diagnostic for the electron to proton temperature ratio at supernova remnant shocks. Two components of emission are produced, a narrow component from electron and proton impact excitation of cold neutrals, and a broad component produced through charge exchange between the cold neutrals and the shock heated protons. Thus the broad and narrow component fluxes reflect the competition between electron and proton impact ionization, electron and proton impact excitation and charge exchange. This diagnostic has led to the discovery of an approximate inverse square relationship between the electron to proton temperature ratio and the shock velocity. In turn, this implies a constant level of electron heating, independent of shock speed above ∼ 450 km/s. In this talk I will present the observational evidence to date. Time permitting, I will introduce how lower-hybrid waves in an extended cosmic ray precursor could explain such a relationship, and how this and other parameters in the H α profile might relate to properties of cosmic rays and magnetic field amplification ahead of the shock. (author)

Transition of radial electric field by electron cyclotron heating in stellarator plasmas

International Nuclear Information System (INIS)

Idei, H.; Ida, K.; Sanuki, H.

1993-06-01

The transition of a radial electric field from a negative to a positive value is observed in Compact Helical System when the electron loss is sufficiently enhanced by the superposition of the off-axis second harmonic electron cyclotron heating on the neutral beam heated plasmas. The observed threshold for the enhanced particle flux required to cause the transition is compared with a theoretical prediction. (author)

Heat shrinkage of electron beam modified EVA

International Nuclear Information System (INIS)

Datta, S.K.; Chaki, T.K.; Bhowmick, A.K.

1997-01-01

Heat shrinkage of electron beam modified ethylene vinyl acetate copolymer (EVA) has been investigated over a range of times, temperatures, stretching, irradiation doses and trimethylolpropane trimethacrylate (TMPTMA) levels. The irradiated (radiation dose 50 kGy and TMPTMA level 1%) and stretched (100% elongation) sample shrinks to a maximum level when kept at 453K temperature for 60 s. The heat shrinkage of samples irradiated with radiation doses of 20, 50, 100 and 150 kGy increases sharply with increasing stretching in the initial stage. Amnesia rating decreases with increasing radiation dose and TMPTMA level as well as gel content. The high radiation dose and TMPTMA level lower the heat shrinkage due to the chain scission. The effect of temperature at which extension is carried out on heat shrinkage is marginal. The irradiated (radiation dose 50 kGy and TMPTMA level 1%) EVA tubes of different dimensions expanded in a laboratory grade tube expander show similar behaviour at 453K and 60 s. The X-ray and DSC studies reveal that the crystallinity increases on stretching due to orientation of chains and it decreases to a considerable extent on heat shrinking. The theoretical and experimental values of heat shrinkage for tubes and rectangular strips are in good accord, when the radiation dose is 50 kGy and TMPTMA level 1%. (author)

Heat shrinkage of electron beam modified EVA

Energy Technology Data Exchange (ETDEWEB)

Datta, S.K.; Chaki, T.K.; Bhowmick, A.K. [Indian Institute of Technology, Kharagpur (India). Rubber Technology Center; Tikku, V.K.; Pradhan, N.K. [NICCO Corporation Ltd., (Cable Div.), Calcutta (India)

1997-10-01

Heat shrinkage of electron beam modified ethylene vinyl acetate copolymer (EVA) has been investigated over a range of times, temperatures, stretching, irradiation doses and trimethylolpropane trimethacrylate (TMPTMA) levels. The irradiated (radiation dose 50 kGy and TMPTMA level 1%) and stretched (100% elongation) sample shrinks to a maximum level when kept at 453K temperature for 60 s. The heat shrinkage of samples irradiated with radiation doses of 20, 50, 100 and 150 kGy increases sharply with increasing stretching in the initial stage. Amnesia rating decreases with increasing radiation dose and TMPTMA level as well as gel content. The high radiation dose and TMPTMA level lower the heat shrinkage due to the chain scission. The effect of temperature at which extension is carried out on heat shrinkage is marginal. The irradiated (radiation dose 50 kGy and TMPTMA level 1%) EVA tubes of different dimensions expanded in a laboratory grade tube expander show similar behaviour at 453K and 60 s. The X-ray and DSC studies reveal that the crystallinity increases on stretching due to orientation of chains and it decreases to a considerable extent on heat shrinking. The theoretical and experimental values of heat shrinkage for tubes and rectangular strips are in good accord, when the radiation dose is 50 kGy and TMPTMA level 1%. (author).

Optimising electron microscopy experiment through electron optics simulation

Energy Technology Data Exchange (ETDEWEB)

Kubo, Y. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Hitachi High-Technologies Corporation, 882, Ichige, Hitachinaka, Ibaraki 312-8504 (Japan); Gatel, C.; Snoeck, E. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Houdellier, F., E-mail: florent.houdellier@cemes.fr [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France)

2017-04-15

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

Optimising electron microscopy experiment through electron optics simulation

International Nuclear Information System (INIS)

Kubo, Y.; Gatel, C.; Snoeck, E.; Houdellier, F.

2017-01-01

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

Rectification of electronic heat current by a hybrid thermal diode.

Science.gov (United States)

Martínez-Pérez, Maria José; Fornieri, Antonio; Giazotto, Francesco

2015-04-01

Thermal diodes--devices that allow heat to flow preferentially in one direction--are one of the key tools for the implementation of solid-state thermal circuits. These would find application in many fields of nanoscience, including cooling, energy harvesting, thermal isolation, radiation detection and quantum information, or in emerging fields such as phononics and coherent caloritronics. However, both in terms of phononic and electronic heat conduction (the latter being the focus of this work), their experimental realization remains very challenging. A highly efficient thermal diode should provide a difference of at least one order of magnitude between the heat current transmitted in the forward temperature (T) bias configuration (Jfw) and that generated with T-bias reversal (Jrev), leading to ℛ = Jfw/Jrev ≫ 1 or ≪ 1. So far, ℛ ≈ 1.07-1.4 has been reported in phononic devices, and ℛ ≈ 1.1 has been obtained with a quantum-dot electronic thermal rectifier at cryogenic temperatures. Here, we show that unprecedentedly high ratios of ℛ ≈ 140 can be achieved in a hybrid device combining normal metals tunnel-coupled to superconductors. Our approach provides a high-performance realization of a thermal diode for electronic heat current that could be successfully implemented in true low-temperature solid-state thermal circuits.

Joule heating and runaway electron acceleration in a solar flare

Science.gov (United States)

Holman, Gordon D.; Kundu, Mukul R.; Kane, Sharad R.

1989-01-01

The hard and soft x ray and microwave emissions from a solar flare (May 14, 1980) were analyzed and interpreted in terms of Joule heating and runaway electron acceleration in one or more current sheets. It is found that all three emissions can be generated with sub-Dreicer electric fields. The soft x ray emitting plasma can only be heated by a single current sheet if the resistivity in the sheet is well above the classical, collisional resistivity of 10(exp 7) K, 10(exp 11)/cu cm plasma. If the hard x ray emission is from thermal electrons, anomalous resistivity or densities exceeding 3 x 10(exp 12)/cu cm are required. If the hard x ray emission is from nonthermal electrons, the emissions can be produced with classical resistivity in the current sheets if the heating rate is approximately 4 times greater than that deduced from the soft x ray data (with a density of 10(exp 10)/cu cm in the soft x ray emitting region), if there are at least 10(exp 4) current sheets, and if the plasma properties in the sheets are characteristic of the superhot plasma observed in some flares by Lin et al., and with Hinotori. Most of the released energy goes directly into bulk heating, rather than accelerated particles.

Third harmonic X-mode electron cyclotron resonance heating on TCV using top launch

International Nuclear Information System (INIS)

Porte, L.; Alberti, S.; Arnoux, G.; Martin, Y.; Hogge, J.P.; Goodman, T.P.; Henderson, M.A.; Nelson-Melby, E.; Pochelon, A.; Tran, M.Q.

2003-01-01

A third harmonic electron cyclotron resonance heating system (X3) has been installed, commissioned and brought into service on the Tokamak a Configuration Variable (TCV). It comprises three 118 GHz, 0.5 MW gyrotrons designed to produce pulses up to 2 seconds long. In the present configuration, 1.0MW is launched vertically from the top of the vessel into the plasma and the remaining 0.5MW is launched horizontally from the low field side. X3 has been used to heat plasmas at density exceeding the 2 nd harmonic cut-off significantly extending the operational space of additionally heated TCV plasmas. Studies have been performed to determine the optimal plasma/launcher configuration for X3 absorption for various plasma conditions and to find methods for real time feedback control of the X3 launcher. First experiments have been performed aimed at heating H-mode plasmas on TCV. First results show that the ELMs in TCV ohmic H-mode plasmas exhibit all characteristics of Type III ELMs. If, at moderate X3 power ( 0.45MW) the Type III ELMs disappear and the H-mode discharge exhibits different MHD phenomena eventually disrupting. (author)

ECRH [electron-cyclotron resonance heating]-heated distributions in thermal-barrier tandem mirrors

International Nuclear Information System (INIS)

Cohen, R.H.; LoDestro, L.L.

1987-01-01

The distribution function is calculated for electrons subjected to strong electron-cyclotron resonance heating (ECRH) at the plug and barrier in a tandem-mirror thermal-barrier cell. When ECRH diffusion locally dominates over collisions and a boundary condition (associated with electrons passing to the center cell) imposes variations on the distribution function rapid compared to the variation of the ECRH and collisional diffusion coefficients, the kinetic equation can be reduced approximately to Laplace's equation. For the typical case where velocity space is divided into distinct regions in which plug and barrier ECRH dominate, the solution in each region can be expressed in terms of the plasma dispersion function or exponential integrals, according to whether the passing electrons are dominated by collisions or ECRH, respectively. The analytic results agree well with Fokker-Planck code results, in terms of both velocity-space structure and values of moments. 10 refs., 4 figs

ICRF power deposition profile and determination of the electron thermal diffusivity by modulation experiments in JET

International Nuclear Information System (INIS)

Gambier, D.J.; Evrard, M.P.; Adam, J.

1990-01-01

The power deposition profile in the ion cyclotron range of frequencies (ICRF) has been investigated experimentally in JET by means of a square wave modulated RF perturbation. The study has been conducted in D(H) and D( 3 He) plasmas for two heating scenarios. In D( 3 He) plasmas and for central heating in a scenario where mode conversion to Bernstein waves is accessible, the direct power deposition profile on electrons has been derived. It accounts for 15% of the total coupled power and extends over 25% of the minor radius. Outside the RF power deposition zone, the electron thermal diffusivity χ e inside the inversion radius surface (r i ) can be estimated through observation of the diffusive electronic transport. In discharges without monster sawteeth and for a low central temperature gradient (∇T e (r ≤ r i ) ≤ ∇T e (r ≥ r i ) approx. = 5 keV·m -1 ) the value obtained is small (approx. =0.24 +- 0.05 m 2 · s -1 ), typically ten times lower than χ e values deduced from heat pulse propagation in similar discharges at radii larger than the inversion radius. For the D(H) minority heating scheme, a large fraction of the ICRF modulated power is absorbed by minority ions, and the minority tail is modulated with a characteristic ion-electron (i-e) slowing-down time. In this scheme, electron heating occurs only through collisions with the minority ion tail and no modulation of the electron temperature is observed in sawtoothing discharges. This is interpreted as a consequence of the long i-e equipartition time, acting as an integrator for the modulated ICRF signal. Finally, a correlation between the time of the sawtooth crash and the periodic turn-off of the ICRF power is found and its consequence for modulation experiments is reviewed. (author). 22 refs, 16 figs

Fast wave direct electron heating in advanced inductive and ITER baseline scenario discharges in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Pinsker, R. I.; Jackson, G. L.; Luce, T. C.; Politzer, P. A. [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States); Austin, M. E. [University of Texas at Austin, Austin, Texas 78712 (United States); Diem, S. J.; Kaufman, M. C.; Ryan, P. M. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Doyle, E. J.; Zeng, L. [University of California Los Angeles, Los Angeles, California 90095 (United States); Grierson, B. A.; Hosea, J. C.; Nagy, A.; Perkins, R.; Solomon, W. M.; Taylor, G. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Maggiora, R.; Milanesio, D. [Politecnico di Torino, Dipartimento di Elettronica, Torino (Italy); Porkolab, M. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Turco, F. [Columbia University, New York, New York 10027 (United States)

2014-02-12

Fast Wave (FW) heating and electron cyclotron heating (ECH) are used in the DIII-D tokamak to study plasmas with low applied torque and dominant electron heating characteristic of burning plasmas. FW heating via direct electron damping has reached the 2.5 MW level in high performance ELMy H-mode plasmas. In Advanced Inductive (AI) plasmas, core FW heating was found to be comparable to that of ECH, consistent with the excellent first-pass absorption of FWs predicted by ray-tracing models at high electron beta. FW heating at the ∼2 MW level to ELMy H-mode discharges in the ITER Baseline Scenario (IBS) showed unexpectedly strong absorption of FW power by injected neutral beam (NB) ions, indicated by significant enhancement of the D-D neutron rate, while the intended absorption on core electrons appeared rather weak. The AI and IBS discharges are compared in an effort to identify the causes of the different response to FWs.

[Scanning electron microscopy of heat-damaged bone tissue].

Science.gov (United States)

Harsanyl, L

1977-02-01

Parts of diaphyses of bones were exposed to high temperature of 200-1300 degrees C. Damage to the bone tissue caused by the heat was investigated. The scanning electron microscopic picture seems to be characteristic of the temperature applied. When the bones heated to the high temperature of 700 degrees C characteristic changes appear on the periostal surface, higher temperatura on the other hand causes damage to the compact bone tissue and can be observed on the fracture-surface. Author stresses the importance of this technique in the legal medicine and anthropology.

Experimental Study of RF Pulsed Heating on Oxygen Free Electronic Copper

Energy Technology Data Exchange (ETDEWEB)

Pritzkau, David P.

2003-02-10

When the thermal stresses induced by RF pulsed heating are larger than the elastic limit, microcracks and surface roughening will occur due to cyclic fatigue. Therefore, pulsed heating limits the maximum surface magnetic field and through it the maximum achievable accelerating gradient. An experiment using circularly cylindrical cavities operating in the TE{sub 011} mode at a resonant frequency of 11.424 GHz was designed to study pulsed heating on Oxygen Free Electronic (OFE) copper. An X-band klystron delivered up to 10 MW to the cavities in 1.5 {micro}s pulses at 60 Hz repetition rate. One run was executed at a temperature rise of 120 K for 56 x 10{sup 6} pulses. Cracks at grain boundaries, slip bands and cracks associated with these slip bands were observed. The second run consisted of 86 x 10{sup 6} pulses with a temperature rise of 82 K, and cracks at grain boundaries and slip bands were seen. Additional information can be derived from the power-coupling iris, and we conclude that a pulsed temperature rise of 250 K for several million pulses leads to destruction of copper. These results can be applied to any mode of any OFE copper cavity.

Electron heat flux dropouts in the solar wind: Evidence for interplanetary magnetic field reconnection?

International Nuclear Information System (INIS)

McComas, D.J.; Gosling, J.T.; Phillips, J.L.; Bame, S.J.; Luhmann, J.G.; Smith, E.J.

1989-01-01

Electron heat flux dropout events have been observed in the solar wind using the ISEE 3 plasma electron data set. These events manifest themselves as dropouts of the solar wind halo electrons which are normally found streaming outward along the local magnetic field. These dropouts leave nearly isotropic distributions of solar wind halo electrons, and consequently, the heat flux in these events is reduced to near the observational noise level. We have examined ISEE 3 data from shortly after launch (August 16, 1978) through the end of 1978 and identified 25 such events ranging in duration from 20 min to over 11 hours. Comparison with the ISEE 3 magnetometer data indicates that these intervals nearly always occur in conjunction with large rotations of the interplanetary magnetic field. Statistical analyses of the plasma and magnetic field data for the 25 dropout intervals indicate that heat flux dropouts generally occur in association with high plasma densities low plasma velocities, low ion and electron temperatures, and low magnetic field magnitudes. A second set of 25 intervals chosen specifically to lie at large field rotations, but at times at which not heat flux dropouts were observed, do not show these characteristic plalsma variations. This suggests that the dropout intervals comprise a unique set of events. Since the hot halo electrons normally found streaming outward from the Sun along the interplanetary magnetic field (the solar wind electron heat flux) are a result of direct magnetic connection to the hot solar corona, heat flux dropout intervals may indicate that the spacecraft is sampling plasma regimes which are magnetically disconnected from the Sun and instead are connected to the outer heliosphere at both ends

A line-of-sight electron cyclotron emission receiver for electron cyclotron resonance heating feedback control of tearing modes

DEFF Research Database (Denmark)

Oosterbeek, J.W.; Bürger, A.; Westerhof, E.

2008-01-01

An electron cyclotron emission (ECE) receiver inside the electron cyclotron resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as a Fabry-Perot interferometer under an angle inside the electron cyclotron wave (ECW) bea...

Acceleration of runaway electrons and Joule heating in solar flares

Science.gov (United States)

Holman, G. D.

1985-01-01

The electric field acceleration of electrons out of a thermal plasma and the simultaneous Joule heating of the plasma are studied. Acceleration and heating timescales are derived and compared, and upper limits are obtained on the acceleration volume and the rate at which electrons can be accelerated. These upper limits, determined by the maximum magnetic field strength observed in flaring regions, place stringent restrictions upon the acceleration process. The role of the plasma resistivity in these processes is examined, and possible sources of anomalous resistivity are summarized. The implications of these results for the microwave and hard X-ray emission from solar flares are examined.

Controlled fusion and plasma heating

International Nuclear Information System (INIS)

1990-06-01

The contributions presented in the 17th European Conference on Controlled Fusion and Plasma Heating were focused on Tore Supra investigations. The following subjects were presented: ohmic discharges, lower hybrid experiments, runaway electrons, Thomson scattering, plasma density measurements, magnetic fluctuations, polarization scattering, plasma currents, plasma fluctuation measurements, evaporation of hydrogen pellets in presence of fast electrons, ripple induced stochastic diffusion of trapped particles, tearing mode stabilization, edge effects on turbulence behavior, electron cyclotron heating, micro-tearing modes, divertors, limiters

Transport in Auxiliary Heated NSTX Discharges

International Nuclear Information System (INIS)

LeBlanc, B.P.; Bell, M.G.; Bell, R.E.; Bitte, M.L.; Bourdelle, C.; Gates, D.A.; Kaye, S.M.; Maingi, R.; Menard, J.E.; Mueller, D.; Ono, M.; Paul, S.F.; Redi, M.H.; Roquemore, A.L.; Rosenberg, A.; Sabbagh, S.A.; Stutman, D.; Synakowski, E.J.; Soukhanovskii, V.A.; Wilson, J.R.

2003-01-01

The NSTX spherical torus (ST) provides a unique platform to investigate magnetic confinement in auxiliary-heated plasmas at low aspect ratio. Auxiliary power is routinely coupled to ohmically heated plasmas by deuterium neutral-beam injection (NBI) and by high-harmonic fast waves (HHFW) launch. While theory predicts both techniques to preferentially heat electrons, experiment reveals the electron temperature is greater than the ion temperature during HHFW, but the electron temperature is less than the ion temperature during NBI. In the following we present the experimental data and the results of transport analyses

Full-scale and time-scale heating experiments at Stripa: preliminary results

International Nuclear Information System (INIS)

Cook, N.G.W.; Hood, Michael; California Univ., Berkeley

1978-01-01

Two full-scale heating experiments and a time-scale heating experiment have recently been started in granite 340 meters below surface. The purpose of the full-scale heating experiments is to assess the near-field effects of thermal loading for the design of an underground repository of nuclear wastes. That of the time-scale heating experiments is to obtain field data of the interaction between heaters and its effect on the rock mass during a period of about two years, which corresponds to about twenty years of full-scale operation. Geological features of the rock around each experiment have been mapped carefully, and temperatures, stresses and displacements induced in the rock by heating have been calculated in advance of the experiments. Some 800 different measurements are recorded at frequent intervals by a computer system situated underground. These data can be compared at any time with predictions made earlier on video display units underground

Electron Energy Confinement for HHFW Heating and Current Drive Phasing on NSTX

International Nuclear Information System (INIS)

Hosea, J.C.; Bernabei, S.; Biewer, T.; LeBlanc, B.; Phillips, C.K.; Wilson, J.R.; Stutman, D.; Ryan, P.; Swain, D.W.

2005-01-01

Thomson scattering laser pulses are synchronized relative to modulated HHFW power to permit evaluation of the electron energy confinement time during and following HHFW pulses for both heating and current drive antenna phasing. Profile changes resulting from instabilities require that the total electron stored energy, evaluated by integrating the midplane electron pressure P(sub)e(R) over the magnetic surfaces prescribed by EFIT analysis, be used to derive the electron energy confinement time. Core confinement is reduced during a sawtooth instability but, although the electron energy is distributed outward by the sawtooth, the bulk electron energy confinement time is essentially unaffected. The radial deposition of energy into the electrons is noticeably more peaked for current drive phasing (longer wavelength excitation) relative to that for heating phasing (shorter wavelength excitation) as is expected theoretically. However, the power delivered to the core plasma is reduced consider ably for the current drive phasing, indicating that surface/peripheral damping processes play a more important role for this case

Mixed-mode distribution systems for high average power electron cyclotron heating

International Nuclear Information System (INIS)

White, T.L.; Kimrey, H.D.; Bigelow, T.S.

1984-01-01

The ELMO Bumpy Torus-Scale (EBT-S) experiment consists of 24 simple magnetic mirrors joined end-to-end to form a torus of closed magnetic field lines. In this paper, we first describe an 80% efficient mixed-mode unpolarized heating system which couples 28-GHz microwave power to the midplane of the 24 EBT-S cavities. The system consists of two radiused bends feeding a quasi-optical mixed-mode toroidal distribution manifold. Balancing power to the 24 cavities is determined by detailed computer ray tracing. A second 28-GHz electron cyclotron heating (ECH) system using a polarized grid high field launcher is described. The launcher penetrates the fundamental ECH resonant surface without a vacuum window with no observable breakdown up to 1 kW/cm 2 (source limited) with 24 kW delivered to the plasma. This system uses the same mixed-mode output as the first system but polarizes the launched power by using a grid of WR42 apertures. The efficiency of this system is 32%, but can be improved by feeding multiple launchers from a separate distribution manifold

Fast wave ion cyclotron resonance heating experiments on the Alcator C tokamak

International Nuclear Information System (INIS)

Shepard, T.D.

1988-09-01

Minority regime fast wave ICRF heating experiments have been conducted on the Alcator C tokamak at rf power levels sufficient to produce significant changes in plasma properties, and in particular to investigate the scaling to high density of the rf heating efficiency. Up to 450 kW of rf power at frequency f = 180 MHz, was injected into plasmas composed of deuterium majority and hydrogen minority ion species at magnetic field B 0 = 12 T, density 0.8 ≤ /bar n/sub e// ≤ 5 /times/ 10 20 m -3 , ion temperature T/sub D/(0) /approximately/ 1 keV, electron temperature T/sub e/(0) /approximately/ 1.5--2.5 keV, and minority concentration 0.25 /approx lt/ /eta/sub H// ≤ 8%. Deuterium heating ΔT/sub D/(0) = 400 eV was observed at /bar n/sub e// = 1 /times/ 10 20 m -3 , with smaller temperature increases at higher density. However, there was no significant change in electron temperature and the minority temperatures were insufficient to account for the launched rf power. Minority concentration scans indicated most efficient deuterium heating at the lowest possible concentration, in apparent contradiction with theory. Incremental heating /tau/sub inc// /equivalent to/ ΔW/ΔP up to 5 ms was independent of density, in spite of theoretical predictions of favorable density scaling of rf absorption and in stark contrast to Ohmic confinement times /tau/sub E// /equivalent to/ W/P. After accounting for mode conversion and minority losses due to toroidal field ripple, unconfined orbits, asymmetric drag, neoclassical and sawtooth transport, and charge-exchange, it was found that the losses as well as the net power deposition on deuterium do scale very favorably with density. Nevertheless, when the net rf and Ohmic powers deposited on deuterium are compared, they are found to be equally efficient at heating the deuterium. 139 refs

Efficient electron heating in relativistic shocks and gamma-ray-burst afterglow.

Science.gov (United States)

Gedalin, M; Balikhin, M A; Eichler, D

2008-02-01

Electrons in shocks are efficiently energized due to the cross-shock potential, which develops because of differential deflection of electrons and ions by the magnetic field in the shock front. The electron energization is necessarily accompanied by scattering and thermalization. The mechanism is efficient in both magnetized and nonmagnetized relativistic electron-ion shocks. It is proposed that the synchrotron emission from the heated electrons in a layer of strongly enhanced magnetic field is responsible for gamma-ray-burst afterglows.

Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics.

Science.gov (United States)

Surducan, E; Surducan, V; Limare, A; Neamtu, C; Di Giuseppe, E

2014-12-01

We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm(3) convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

Sheath and heat flow of a two-electron-temperature plasma in the presence of electron emission

International Nuclear Information System (INIS)

Sato, Kunihiro; Miyawaki, Fujio

1992-01-01

The electrostatic sheath and the heat flow of a two-electron-temperature plasma in the presence of electron emission are investigated analytically. It is shown that the energy flux is markedly enhanced to a value near the electron free-flow energy flux as a result of considerable reduction of the sheath potential due to electron emission if the fraction of hot electrons at the sheath edge is much smaller than one. If the hot- to cold-electron temperature ratio is of the order of ten and the hot electron density is comparable to the cold electron density, the action of the sheath as a thermal insulator is improved as a result of suppression of electron emission due to the space-charge effect of hot electrons. (author)

Dependence of core heating properties on heating pulse duration and intensity

Science.gov (United States)

Johzaki, Tomoyuki; Nagatomo, Hideo; Sunahara, Atsushi; Cai, Hongbo; Sakagami, Hitoshi; Mima, Kunioki

2009-11-01

In the cone-guiding fast ignition, an imploded core is heated by the energy transport of fast electrons generated by the ultra-intense short-pulse laser at the cone inner surface. The fast core heating (˜800eV) has been demonstrated at integrated experiments with GEKKO-XII+ PW laser systems. As the next step, experiments using more powerful heating laser, FIREX, have been started at ILE, Osaka university. In FIREX-I (phase-I of FIREX), our goal is the demonstration of efficient core heating (Ti ˜ 5keV) using a newly developed 10kJ LFEX laser. In the first integrated experiments, the LFEX laser is operated with low energy mode (˜0.5kJ/4ps) to validate the previous GEKKO+PW experiments. Between the two experiments, though the laser energy is similar (˜0.5kJ), the duration is different; ˜0.5ps in the PW laser and ˜ 4ps in the LFEX laser. In this paper, we evaluate the dependence of core heating properties on the heating pulse duration on the basis of integrated simulations with FI^3 (Fast Ignition Integrated Interconnecting) code system.

Abnormal excess heat observed during Mizuno-type experiments

International Nuclear Information System (INIS)

Fauvarque, Jean-Francois; Clauzon, Pierre Paul; Lalleve, Gerard Jean-Michel

2006-01-01

A simple calorimeter has been designed that works at constant temperature; that of boiling water. Heat Losses can be estimated accurately with an ohmic heater. As expected, losses are independent of the electric power input to the heater and the amount of evaporated water is linearly dependant on the power input. The device has been used to determine the heating power of a plasma electrolysis (the Ohmori-Mizuno experiment). We confirm that in this experiment, the heat output from electrolysis is greater than the electrical power input. The excess energy increases as the electrolysis voltage is increased from 200 up to 350 V (400 V input). The excess energy may be as high as 120 W. (author)

Ionospheric Electron Heating Associated With Pulsating Auroras: Joint Optical and PFISR Observations

Science.gov (United States)

Liang, Jun; Donovan, E.; Reimer, A.; Hampton, D.; Zou, S.; Varney, R.

2018-05-01

In a recent study, Liang et al. (2017, https://doi.org/10.1002/2017JA024127) repeatedly identified strong electron temperature (Te) enhancements when Swarm satellites traversed pulsating auroral patches. In this study, we use joint optical and Poker Flat Incoherent Scatter Radar (PFISR) observations to further investigate the F region plasma signatures related to pulsating auroras. On 19 March 2015 night, which contained multiple intervals of pulsating auroral activities, we identify a statistical trend, albeit not a one-to-one correspondence, of strong Te enhancements ( 500-1000 K) in the upper F region ionosphere during the passages of pulsating auroras over PFISR. On the other hand, there is no discernible and repeatable density enhancement in the upper F region during pulsating auroral intervals. Collocated optical and NOAA satellite observations suggest that the pulsating auroras are composed of energetic electron precipitation with characteristic energy >10 keV, which is inefficient in electron heating in the upper F region. Based upon PFISR observations and simulations from Liang et al. (2017) model, we propose that thermal conduction from the topside ionosphere, which is heated by precipitating low-energy electrons, offers the most likely explanation for the observed electron heating in the upper F region associated with pulsating auroras. Such a heating mechanism is similar to that underlying the "stable auroral red arcs" in the subauroral ionosphere. Our proposal conforms to the notion on the coexistence of an enhanced cold plasma population and the energetic electron precipitation, in magnetospheric flux tubes threading the pulsating auroral patch. In addition, we find a trend of enhanced ion upflows during pulsating auroral intervals.

Study of the heat flux generated by accelerated electrons on the components near the plasma

International Nuclear Information System (INIS)

Laugier, J.

2003-01-01

Experimental data have shown that a heat flux appears on components situated near the wave guide of the lower hybrid antenna of Tore-Supra. This heat flux is due to the energy release during collisions that occur between the component surface and the electrons accelerated by the high frequency field generated by the antenna. Simulations show that the electrons may reach an energy of 2-3 keV and that the heat flux generated in the shield may reach 10 MW/m 2 . In this work a correlation has been established between the local heat flux due to electron impact and the mean electrical field near the antenna: Φ (W/m 2 ) = 4.10 -4 x E -6 (10 5 V/m). It is also shown that the ratio of electrons that reach the shield is roughly not dependent on the value of the mean electrical field. In the hypothesis of a Gaussian distribution of electron initial velocities this ratio is 10%. (A.C.)

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

International Nuclear Information System (INIS)

Giri, Ashutosh; Hopkins, Patrick E.

2015-01-01

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 be 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

A ferroelectric electron gun in a free-electron maser experiment

International Nuclear Information System (INIS)

Einat, M.; Jerby, E.; Rosenman, G.

2002-01-01

An electron-gun based on a ferroelectric cathode is studied in a free-electron maser (FEM) experiment. In this gun, the electrons are separated from the cathode surface plasma, and are accelerated in two stages. The electron energy-spread is reduced sufficiently for an FEM operation in the microwave regime. A 14 keV, 1-2 A e-beam is obtained in a 0.1-2.1 μs pulse width. The pulse repetition frequency attains 3.1 MHz in ∼50% duty-cycle. This gun is implemented in an FEM oscillator experiment operating around 3 GHz. The paper presents experimental results and discusses the applicability of ferroelectric guns in free-electron laser devices

A ferroelectric electron gun in a free-electron maser experiment

CERN Document Server

Einat, M; Rosenman, G

2002-01-01

An electron-gun based on a ferroelectric cathode is studied in a free-electron maser (FEM) experiment. In this gun, the electrons are separated from the cathode surface plasma, and are accelerated in two stages. The electron energy-spread is reduced sufficiently for an FEM operation in the microwave regime. A 14 keV, 1-2 A e-beam is obtained in a 0.1-2.1 mu s pulse width. The pulse repetition frequency attains 3.1 MHz in approx 50% duty-cycle. This gun is implemented in an FEM oscillator experiment operating around 3 GHz. The paper presents experimental results and discusses the applicability of ferroelectric guns in free-electron laser devices.

Wave trajectory and electron cyclotron heating in toroidal plasmas

International Nuclear Information System (INIS)

Maekawa, T.; Tanaka, S.; Terumichi, Y.; Hamada, Y.

1977-12-01

Wave trajectories propagating obliquely to magnetic field in toroidal plasmas are studied theoretically. Results show that the ordinary wave at appropriate incident angle is mode-converted to the extraordinary wave at first turning point and is further converted to the electron Bernstein wave during passing a loop or a hooked nail curve near second turning point and is cyclotron-damped away, resulting in local electron heating, before arriving at cyclotron resonance layer. (auth.)

The generation of intense heat fluxes by electron bombardment to evaluate the use of swirl flow in the cooling of accelerator targets

International Nuclear Information System (INIS)

Genis, G.J.

1985-11-01

The thermal performance of isotope production targets for accelerators has been shown to be the limiting factor with regard to the cost of isotopes and the specific activity achievable. To allow the investigation of basic aspects of target cooling and the evaluation of certain target concepts off-line from accelerators, an electron bombardment system, including a radial electron accelerator (REA) in a diode configuration, was developed as heat source. Methods were developed to characterise the performance of the REA to supply a homogeneous heat flux to an axial target by which a technique for the construction of thermocouple placement holes in the body of the target can be evaluated from the measured temperatures. Having identified high velocity swirl flow as the most suitable technique to enhance the convective heat transfer in targets, experiments were conducted to determine the heat-transfer coefficient at high heat fluxes to high velocity swirl flow. The heat-transfer results substantiate the advantages of swirl flow for target cooling. Different correlations obtained indicate the importance of using the film properties instead of the bulk coolant properties in correlations and identify centrifugal convection as one of the most important heat transfer mechanisms in swirl flow

Simulation of D and E region high-power microwave heating with HF ionospheric modification experiments

International Nuclear Information System (INIS)

Meltz, G.; Rush, C.M.; Violette, E.J.

1981-01-01

The microwave power beam from a Solar Power Satellite (SPS) is sufficiently intense to cause large changes in the properties of the lower ionosphere by ohmic heating of the plasma. Power is absorbed from the beam at a rate that is proportional to the ratio of the flux s and the square of an effective frequency f/sub e/. Throughout most of the lower ionosphere f/sub e/ = f -+ f/sub L/, where f is the wave frequency and f/sub L is a reduced electron gyrofrequency. It follows that SPS equivalent heating can be simulated at much lower power fluxes with HF radio waves. A detailed examination of the frequency scaling, based on fluid and kinetic theory estimates of the change in electron temperature and density, shows that the high-power HF facility at Platteville, CO, can simulate or exceed the ohmic effects of the SPS beam up to 90 km. This paper describes the results of a series of 5.2 and 9.9 MHz underdense heating experiments undertaken to study the effect of high-power microwaves on the lower ionosphere. A pulsed ionosonde probe, located nearly below the most intense portion of the high-power beam, was used to observe the changes in the D and lower E region. Both phase and amplitude measurements were recorded during CW and intermittent heating

The DNA electronic specific heat at low temperature: The role of aperiodicity

Energy Technology Data Exchange (ETDEWEB)

Sarmento, R.G. [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Mendes, G.A. [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Albuquerque, E.L., E-mail: eudenilson@gmail.com [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Fulco, U.L. [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Vasconcelos, M.S. [Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN (Brazil); Ujsághy, O. [Department of Theoretical Physics and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budapest University of Technology and Economics, Budafoki út 8, H-1521 Budapest (Hungary); Freire, V.N. [Departamento de Física, Universidade Federal do Ceará, 60455-760, Fortaleza, CE (Brazil); Caetano, E.W.S. [Instituto Federal de Educação, Ciência e Tecnologia do Ceará, 60040-531, Fortaleza, CE (Brazil)

2012-07-16

The electronic specific heat spectra at constant volume (C{sub V}) of a long-range correlated extended ladder model, mimicking a DNA molecule, is theoretically analyzed for a stacked array of a double-stranded structure made up from the nucleotides guanine G, adenine A, cytosine C and thymine T. The role of the aperiodicity on C{sub V} is discussed, considering two different nucleotide arrangements with increasing disorder, namely the Fibonacci and the Rudin–Shapiro quasiperiodic structures. Comparisons are made for different values of the band fillings, considering also a finite segment of natural DNA, as part of the human chromosome Ch22. -- Highlights: ► Quasiperiodic sequence to mimic the DNA nucleotides arrangement. ► Electronic tight-binding Hamiltonian model. ► Electronic density of states. ► Electronic specific heat spectra.

TEM heat transport and fluctuations in the HSX stellarator: experiments and comparison with gyrokinetic simulation

Science.gov (United States)

Smoniewski, J.; Faber, B. J.; Sánchez, E.; Calvo, I.; Pueschel, M. J.; Likin, K. M.; Deng, C. B.; Talmadge, J. N.

2017-10-01

The Helically Symmetric eXperiment (HSX) has demonstrated reduced neoclassical transport in the plasma core with quasi-symmetry [Lore Thesis 2010], while outside this region the electron thermal diffusivity is well above the neoclassical level, likely due to the Trapped Electron Mode (TEM) [Weir PoP 2015, Faber PoP 2015]. We compare gyrokinetic simulations of the TEM to experimental heat flux and density fluctuation measurements for two configurations: Quasi-Helical Symmetry (QHS) and broken symmetry (Mirror). Both experiment and simulation show that the heat flux for Mirror is larger than for QHS by about a factor of two. Initial interferometer measurements provide evidence that density-gradient-driven TEMs are driving turbulence. Calculations of the collisionless damping of zonal flows provide another perspective into the difference between geometries. Similar to other stellarators [Monreal PPCF 2016], the zonal flow residual goes to zero at long wavelengths in both configurations. Additionally, the very short time decay of the zonal flow due to neoclassical polarization is constant between configurations. However, the collisionless damping time is longer and the zonal flow oscillation frequency is smaller in QHS than Mirror, consistent with reduced radial particle drifts. Work supported by the US DOE under Grant DE-FG02-93ER54222.

The RF voltage dependence of the electron sheath heating in low pressure capacitively coupled rf discharges

International Nuclear Information System (INIS)

Buddemeier, U.; Kortshagen, U.; Pukropski, I.

1995-01-01

In low pressure capacitively coupled RF discharges two competitive electron heating mechanisms have been discussed for some time now. At low pressures the stochastic sheath heating and for somewhat higher pressures the Joule heating in the bulk plasma have been proposed. When the pressure is increased at constant RF current density a transition from concave electron distribution functions (EDF) with a pronounced cold electron group to convex EDFs with a missing strong population of cold electrons is found. This transition was interpreted as the transition from dominant stochastic to dominant Joule heating. However, a different interpretation has been given by Kaganovich and Tsendin, who attributed the concave shaped EDFs to the spatially inhomogeneous RF field in combination with the nonlocality of the EDF

A study on experiment and numerical simulation of heat exchanger in heating furnace

Directory of Open Access Journals (Sweden)

Z. C. Lv

2018-01-01

Full Text Available In this paper, air preheater is used the research object and its heat transfer law is studied by experiment and numerical simulation. The experimental data showed that with the increases of inlet air velocity, the comprehensive heat transfer coefficient and heat transfer efficiency increase, but the temperature efficiency decreases and the resistance loss on the air side increases. The numerical simulation results showed that the larger the diameter of the tube, the better the heat transfer effect. When horizontal spacing in the range of 290 - 305 mm and longitudinal spacing is 70 - 90 mm, the heat transfer effect is best. The optimized heat exchanger structure is that diameter is 60 mm, horizontal spacing is 300 mm, longitudinal spacing is 90 mm. As the inlet air flow rate increases, the heat transfer efficiency increases, but the temperature efficiency decreases and the resistance loss on the air side increases.

Coupling heat and chemical tracer experiments for estimating heat transfer parameters in shallow alluvial aquifers.

Science.gov (United States)

Wildemeersch, S; Jamin, P; Orban, P; Hermans, T; Klepikova, M; Nguyen, F; Brouyère, S; Dassargues, A

2014-11-15

Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54MJ/m(3)/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for

Hollow density profile on electron cyclotron resonance heating JFT-2M plasma

International Nuclear Information System (INIS)

Yamauchi, Toshihiko; Hoshino, Katsumichi; Kawashima, Hisato; Ogawa, Toshihide; Kawakami, Tomohide; Shiina, Tomio; Ishige, Youichi

1998-01-01

The first hollow electron density profile in the central region on the JAERI Fusion Torus-2M (JFT-2M) is measured during electron cyclotron resonance heating (ECRH) with a TV Thomson scattering system (TVTS). The peripheral region is not hollow but is accumulated due to pump-out from the central region. The hollowness increases with time but is saturated at ∼40 ms and maintains a constant hollow ratio. The hollowness is strongly related to the steep temperature gradient of the heated zone. (author)

Subseabed Disposal Program In-Situ Heat Transfer Experiment (ISHTE)

International Nuclear Information System (INIS)

Percival, C.M.

1983-05-01

A heat transfer experiment is being developed in support of the Subseabed Disposal Program. The primary objectives of this experiment are: to provide information on the in situ response of seabed sediment to localized heating; to provide an opportunity to evaluate theoretical models of the response and to observe any unanticipated phenomena which may occur; and to develop and demonstrate the technology necessary to perform waste isolation oriented experiments on the seafloor at depths up to 6000 m. As presently envisaged, the heat transfer experiment will be conducted at a location in the central North Pacific though it could be performed anywhere that the ocean bottom is of the type deemed suitable for the disposal of nuclear waste material. The experiment will be conducted of the seafloor from a recoverable space-frame platform at a depth of approximately 6000 m. A 400-W isotopic heat source will be implanted in the illite sediment and the subsequent response of the sediment to the induced thermal field evaluated. After remote initiation of the experiment, a permanent record of the data obtained will be recorded on board the platform, with selected information transmitted to a surface vessel by acoustic telemetry. The experiment will be operational for one year, after which the entire platform will be recovered. Current plans call for the deployment of the experiment in 1986. Specific activities which will be pursued during the course of the experiment include: measurement of the thermal field; determination of the effective thermal conductivity of the sediment; measurement of pore pressure; evaluation of radionuclide migration processes; pore water sampling; sediment chemistry studies; sediment shear strength measurements; and coring operations in the immediate vicinity of the experiment for postexperiment analysis

HF heating of a plasma column at frequencies below the electron cyclotron frequency

International Nuclear Information System (INIS)

Datlov, J.; Kopecky, V.; Musil, J.; Zacek, F.; Novik, K.

1978-02-01

The dispersion of waves, excited by the helical structure in a plasma column and the heating of a tail of the electron distribution function is studied at frequencies below the electron plasma frequency and the electron cyclotron frequency. (author)

Remote Joule heating by a carbon nanotube.

Science.gov (United States)

Baloch, Kamal H; Voskanian, Norvik; Bronsgeest, Merijntje; Cumings, John

2012-04-08

Minimizing Joule heating remains an important goal in the design of electronic devices. The prevailing model of Joule heating relies on a simple semiclassical picture in which electrons collide with the atoms of a conductor, generating heat locally and only in regions of non-zero current density, and this model has been supported by most experiments. Recently, however, it has been predicted that electric currents in graphene and carbon nanotubes can couple to the vibrational modes of a neighbouring material, heating it remotely. Here, we use in situ electron thermal microscopy to detect the remote Joule heating of a silicon nitride substrate by a single multiwalled carbon nanotube. At least 84% of the electrical power supplied to the nanotube is dissipated directly into the substrate, rather than in the nanotube itself. Although it has different physical origins, this phenomenon is reminiscent of induction heating or microwave dielectric heating. Such an ability to dissipate waste energy remotely could lead to improved thermal management in electronic devices.

Thermal modeling of multi-shape heating sources on n-layer electronic board

Directory of Open Access Journals (Sweden)

Monier-Vinard Eric

2017-01-01

Full Text Available The present work completes the toolbox of analytical solutions that deal with resolving steady-state temperatures of a multi-layered structure heated by one or many heat sources. The problematic of heating sources having non-rectangular shapes is addressed to enlarge the capability of analytical approaches. Moreover, various heating sources could be located on the external surfaces of the sandwiched layers as well as embedded at interface of its constitutive layers. To demonstrate its relevance, the updated analytical solution has been compared with numerical simulations on the case of a multi-layered electronic board submitted to a set of heating source configurations. The comparison shows a high agreement between analytical and numerical calculations to predict the centroid and average temperatures. The promoted analytical approach establishes a kit of practical expressions, easy to implement, which would be cumulated, using superposition principle, to help electronic designers to early detect component or board temperatures beyond manufacturer limit. The ability to eliminate bad concept candidates with a minimum of set-up, relevant assumptions and low computation time can be easily achieved.

Microwave measurement test results of circular waveguide components for electron cyclotron resonant heating (ECRH) of the Tandem Mirror Experiment-Upgrade (TMX-U)

International Nuclear Information System (INIS)

Williams, C.W.; Rubert, R.R.; Coffield, F.E.; Felker, B.; Stallard, B.W.; Taska, J.

1983-01-01

Development of high-power components for electron cyclotron resonant heating (ECRH) applications requires extensive testing. In this paper we describe the high-power testing of various circular waveguide components designed for application on the Tandem Mirror Experiment-Upgrade (TMX-U). These include a 2.5-in. vacuum valve, polarizing reflectors, directional couplers, mode converters, and flexible waveguides. All of these components were tested to 200 kW power level with 40-ms pulses. Cold tests were used to determine field distribution. The techniques used in these tests are illustrated. The new high-power test facility at Lawrence Livermore National Laboratory (LLNL) is described and test procedures are discussed. We discuss the following test results: efficiency at high power of mode converters, comparison of high power vs low power for waveguide components, and full power tests of the waveguide system. We also explain the reasons behind selection of these systems for use on TMX-U

Heat storage in the Hettangian aquifer in Berlin - results from a column experiment

Science.gov (United States)

Milkus, Chri(Sch)augott

2015-04-01

Aquifer Thermal Energy Storage (ATES) is a sustainable alternative for storage and seasonal availability of thermal energy. However, its impact on the subsurface flow regime is not well known. In Berlin (Germany), the Jurassic (Hettangian) sandstone aquifer with highly mineralized groundwater (TDS 27 g/L) is currently used for heat storage. The aim of this study was to examine the hydrogeochemical changes that are caused by the induced temperature shift and its effects on the hydraulic permeability of the aquifer. Column experiments were conducted, in which stainless steel columns were filled with sediment from the aquifer and flushed with native groundwater for several weeks. The initial temperature of the experiment was 20°C, comparable to the in-situ conditions within the aquifer. After reaching equilibrium between sediment and water, the temperature was increased to simulate heating of the aquifer. During the experiment, physical and chemical parameters (pH, ORP, dissolved oxygen and dissolved carbon dioxide) were measured at the outflow of the column and the effluent water was sampled. Using a Scanning Electron Microscope, the deposition of precipitated minerals and biofilm on sediment grains was analyzed. Changes in hydraulic properties of the sediment were studied by the use of tracer tests with Uranin.

Nuclear heat applications in Russia: Experience, status and prospects

International Nuclear Information System (INIS)

Mitenkov, F.M.; Kusmartsev, E.V.

1998-01-01

The extensive experience gained with nuclear district heating in Russia is described. Most of the WWER reactors in Russia are cogeneration plants. Steam is extracted through LP turbine bleeders and condensed in intermediate heat exchangers to hot water which is then supplied to DH grids. Also some small dedicated nuclear heating plants are operated. (author)

FWCD (fast wave current drive) and ECCD (electron cyclotron current drive) experiments on DIII-D

International Nuclear Information System (INIS)

Prater, R.; Austin, M.; Baity, F.W.

1994-01-01

Fast wave current drive and electron cyclotron current drive experiments have been performed on the DIII-D tokamak as part of the advanced tokamak program. The goal of this program is to develop techniques for controlling the profile of the current density in order to access regimes of improved confinement and stability. The experiments on fast wave current drive used a four strap antenna with 90deg phasing between straps. A decoupler was used to help maintain the phasing, and feedback control of the plasma position was used to keep the resistive loading constant. RF pickup loops demonstrate that the directivity of the antenna is as expected. Plasma currents up to 0.18 MA were driven by 1.5 MW of fast wave power. Electron cyclotron current drive experiments at 60 GHz have shown 0.1 MA of plasma current driven by 1 MW of power. New fast wave and electron cyclotron heating systems are in development for DIII-D, so that the goals of the advanced tokamak program can be carried out. (author)

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Electron Cyclotron Resonance Heating of a High-Density Plasma

DEFF Research Database (Denmark)

Hansen, F. Ramskov

1986-01-01

Various schemes for electron cyclotron resonance heating of tokamak plasmas with the ratio of electron plasma frequency to electron cyclotron frequency, "»pe/^ce* larger than 1 on axis, are investigated. In particular, a mode conversion scheme is investigated using ordinary waves at the fundamental...... of the electron cyclotron frequency. These are injected obliquely from the outside of the tokamak near an optimal angle to the magnetic field lines. This method involves two mode conversions. The ordinary waves are converted into extraordinary waves near the plasma cut-off layer. The extraordinary waves...... are subsequently converted into electrostatic electron Bernstein waves at the upper hybrid resonance layer, and the Bernstein waves are completely absorbed close to the plasma centre. Results are presented from ray-tracinq calculations in full three-dimensional geometry using the dispersion function for a hot non...

Data analysis for electronic experiments

International Nuclear Information System (INIS)

Grote, H.

1981-01-01

In this lecture I schell attempt to cover the principal off-line software aspects in electronic experiments. Of course, this is too ambitious an undertaking for two reasons: Firstly the field is vast, and some important aspect will certainly have escaped my attention. Secondly, the choice of methods, features, algorithms, and packages presented will be biased through my personal opinion and experience, although to some extent it is influenced as well by the opinion and experience of my colleagues, who, like myself, are working in this field at CERN. Therefore, beware. Whenever I shall claim something to be evident, a matter of experience -- a fact --it ain't necessarily so. On the other hand, it will not be entirely wrong, since our experience is based on something like 30 experiments in high-energy physics using electronic for other people, and although these people are of course misled, one has to admit their existence. (orig.)

The International Heat Stress Genotype Experiment for modeling wheat response to heat: field experiments and AgMIP-Wheat multi-model simulations

NARCIS (Netherlands)

Martre, P.; Reynolds, M.P.; Asseng, S.; Ewert, F.; Alderman, P.D.; Cammarano, D.; Maiorano, Andrea; Ruane, A.C.; Aggarwal, P.K.; Anothai, J.; Supit, I.; Wolf, J.

2017-01-01

The data set contains a portion of the International Heat Stress Genotype Experiment (IHSGE) data used in the AgMIP-Wheat project to analyze the uncertainty of 30 wheat crop models and quantify the impact of heat on global wheat yield productivity. It includes two spring wheat cultivars grown during

Electronics for LHC experiments

International Nuclear Information System (INIS)

Bourgeois, Francois

1995-01-01

Full text: A major effort is being mounted to prepare the way handling the high interaction rates expected from CERN's new LHC proton-proton collider (see, for example, November, page 6). September saw the First Workshop on Electronics for LHC Experiments, organized by Lisbon's Particle Physics Instrumentation Laboratory (LIP) on behalf of CERN's LHC Electronics Review Board (LERB - March, page 2). Its purpose was not only for the LERB to have a thorough review of ongoing activities, but also to promote cross fertilization in the engineering community involved in electronics design for LHC experiments. The Workshop gathered 187 physicists and engineers from 20 countries including USA and Japan. The meeting comprised six sessions and 82 talks, with special focus on radiation-hard microelectronic processes, electronics for tracking, calorimetry and muon detectors, optoelectronics, trigger and data acquisition systems. Each topic was introduced by an invited speaker who reviewed the requirements set by the particular detector technology at LHC. At the end of each session, panel discussions were chaired by each invited speaker. Representatives from four major integrated circuit manufacturers covered advanced radiation hard processes. Two talks highlighted the importance of obsolescence and quality systems in the long-lived and demanding environment of LHC. The Workshop identified areas and encouraged efforts for rationalization and common developments within and between the different detector groups. As a result, it will also help ensure the reliability and the long term maintainability of installed equipment. The proceedings of the Workshop are available from LIP Lisbon*. The LERB Workshop on Electronics for LHC Experiments will become a regular event, with the second taking place in Hungary, by Lake Balaton, from 23-27 September 1996. The Hungarian institutes KFKIRMKI have taken up the challenge of being as successful as LIP Lisbon in the organization

Heat transfer and critical heat flux in a asymmetrically heated tube helicoidal flow

International Nuclear Information System (INIS)

Boscary, J.

1995-10-01

The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs

Heat-induced electron emission in paraelectric phase of triglycine sulfate heated with great rate

CERN Document Server

Sidorkin, A A; Rogazinskaya, O V; Milovidova, S D

2002-01-01

One recorded experimentally heat-induced electron emission in ferroelectric triglycine sulfate (TGS) crystal within temperature range exceeding the Curie point by 10-15 K. One studied cases of q = dT/dt various rates of linear heating of specimens of TGS nominally pure crystal and TGS crystal with chromium impurity. Increase of heating rate is shown to result in increase of emission current density within the whole investigated range of temperatures. Temperature of emission occurrence depends on q rate negligibly. At the same time, temperature of emission disappearance monotonically increases with q growth. At q below 1 K/min it is localized below the Curie point. At q = 4-5 K/min the mentioned temperature reaches 60-65 deg C. In TGS crystal with chromium impurity the temperature of emission occurrence is close to the case of pure TGS. In this case, the range of emission drawing in paraphase here is by about 2 times narrower in contrast to the case of pure TGS heated with the same rate

Electron heating via self-excited plasma series resonance in geometrically symmetric multi-frequency capacitive plasmas

International Nuclear Information System (INIS)

Schüngel, E; Brandt, S; Schulze, J; Donkó, Z; Korolov, I; Derzsi, A

2015-01-01

The self-excitation of plasma series resonance (PSR) oscillations plays an important role in the electron heating dynamics in capacitively coupled radio-frequency (CCRF) plasmas. In a combined approach of PIC/MCC simulations and a theoretical model based on an equivalent circuit, we investigate the self-excitation of PSR oscillations and their effect on the electron heating in geometrically symmetric CCRF plasmas driven by multiple consecutive harmonics. The discharge symmetry is controlled via the electrical asymmetry effect (EAE), i.e. by varying the total number of harmonics and tuning the phase shifts between them. It is demonstrated that PSR oscillations will be self-excited under both symmetric and asymmetric conditions, if (i) the charge–voltage relation of the plasma sheaths deviates from a simple quadratic behavior and (ii) the inductance of the plasma bulk exhibits a temporal modulation. These two effects have been neglected up to now, but we show that they must be included in the model in order to properly describe the nonlinear series resonance circuit and reproduce the self-excitation of PSR oscillations, which are observed in the electron current density resulting from simulations of geometrically symmetric CCRF plasmas. Furthermore, the effect of PSR self-excitation on the discharge current and the plasma properties, such as the potential profile, is illustrated by applying Fourier analysis. High-frequency oscillations in the entire spectrum between the applied frequencies and the local electron plasma frequency are observed. As a consequence, the electron heating is strongly enhanced by the presence of PSR oscillations. A complex electron heating dynamics is found during the expansion phase of the sheath, which is fully collapsed, when the PSR is initially self-excited. The nonlinear electron resonance heating (NERH) associated with the PSR oscillations causes a spatial asymmetry in the electron heating. By discussing the resulting ionization

Experimental comparison between different configurations of PCM based heat sinks for cooling electronic components

International Nuclear Information System (INIS)

Gharbi, Salma; Harmand, Souad; Jabrallah, Sadok Ben

2015-01-01

The thermal control of electronic components is aimed at ensuring their use in a temperature range compatible with their performances. This paper presents an experimental study of the behavior of phase change materials (PCMs) as the cooling system for electronic devices. Four configurations are used to control the increase in the system temperature: pure PCM, PCM in a silicone matrix, PCM in a graphite matrix and pure PCM in a system of fins. Thermo-physical properties of different PCMs are determined and found to be desirable for application in this study. Solid liquid interface visualization and temperature evolution are employed to understand the mechanism of heat transfer during the different stages. Results indicated that the inclusion of PCM can lower component increase temperature and extends twice the critical time of the heat sink. The use of Graphite matrix filled by PCM showed more improvement on system thermal performance than silicon matrix. Also, for the same fraction of copper, it was found that incorporating long copper fins with suitable spacing into PCM, can enhance heat distribution into PCM leading to longer remain component temperature below the critical limit. This work therefore shows that the combination of PCM and long, well-spaced fins presents an effective means for thermal control of electronic devices. - Highlights: • Study on thermal performance of different PCM based heat sink in electronic cooling. • Examination of heat transfer mechanism into heat sink for different conditions. • Graphite matrix shows more efficiency than silicon. • Inclusion PCM can reduce temperature increasing. • Heat sink with longer well spaced fins can extend longer the critical time

Quantum Optical Heating in Sonoluminescence Experiments

International Nuclear Information System (INIS)

Kurcz, Andreas; Capolupo, Antonio; Beige, Almut

2009-01-01

Sonoluminescence occurs when tiny bubbles rilled with noble gas atoms are driven by a sound wave. Each cycle of the driving field is accompanied by a collapse phase in which the bubble radius decreases rapidly until a short but very strong light flash is emitted. The spectrum of the light corresponds to very high temperatures and hints at the presence of a hot plasma core. While everyone accepts that the effect is real, the main energy focussing mechanism is highly controversial. Here we suggest that the heating of the bubble might be due to a weak but highly inhomogeneous electric field as it occurs during rapid bubble deformations [A. Kurcz et al.(submitted)]. It is shown that such a field couples the quantised motion of the atoms to their electronic states, thereby resulting in very high heating rates.

Electron spin resonance and its application to heat treated carbonaceous materials

International Nuclear Information System (INIS)

Emmerich, Francisco Guilherme

1993-01-01

This work presents the basic characteristics of the electron spin resonance technique, also called paramagnetic resonance, being discussed its application to heat treated carbonaceous materials. In the low heat treatment temperature (HTT) range (below 700 deg C) the organic free radical are the predominant unpaired spin center, which play a key role in the process of carbonization and meso phase formation. At higher temperatures, it is possible to make correlations between the low H T T range and the high HTT range (above 130 deg C), where the predominant unpaired spin center are the free charge carriers (free electrons) of the graphite like crystallites of the material, which are formed by the carbonization process. (author)

Impact of the amount of working fluid in loop heat pipe to remove waste heat from electronic component

Directory of Open Access Journals (Sweden)

Smitka Martin

2014-03-01

Full Text Available One of the options on how to remove waste heat from electronic components is using loop heat pipe. The loop heat pipe (LHP is a two-phase device with high effective thermal conductivity that utilizes change phase to transport heat. It was invented in Russia in the early 1980’s. The main parts of LHP are an evaporator, a condenser, a compensation chamber and a vapor and liquid lines. Only the evaporator and part of the compensation chamber are equipped with a wick structure. Inside loop heat pipe is working fluid. As a working fluid can be used distilled water, acetone, ammonia, methanol etc. Amount of filling is important for the operation and performance of LHP. This work deals with the design of loop heat pipe and impact of filling ratio of working fluid to remove waste heat from insulated gate bipolar transistor (IGBT.

Preliminary results from the Arecibo Heating Experiment (HEX): HF to GNSS

Science.gov (United States)

Jackson-Booth, N.; Penney, R.; Bernhardt, P. A.; Martin, P. L.; Buckland, R.; Morton-Orr, T.; Nossa, E.; Buckland, R.

2017-12-01

The ionosphere is subject to many solar and terrestrial influences that can generate disturbances, causing degradation to modern communication and navigational systems. Whilst the disturbances are normally caused by natural phenomena such as hurricanes, earthquakes and solar storms; they can also be generated by artificially modifying the ionosphere. Artificial Ionospheric Modification (AIM) attempts to alter a small region of the ionosphere in order to perturb the RF propagation environment. This can be achieved through injecting the ionosphere with aerosols, chemicals or radio signals. The effects of any such modification can be detected through the deployment of sensors, including ground based high-frequency (HF) sounders and dual-band Global Navigation Satellite System (GNSS) receivers. HF sounders allow measurements of the bottom-side of the ionosphere. GNSS receivers offer a convenient means of obtaining information about the ionosphere, including ionospheric disturbances through changes in the derived total electron content information. The Heating EXperiment (HEX), which took place in March and May 2017, was designed to further our understanding of the phenomena caused by artificially heating a small region of the ionosphere, using the Arecibo facility in Puerto Rico. This was achieved by utilizing a HF measurement experiment spread between Texas and Trinidad and the deployment of a small scale travelling ionospheric disturbance (TID) network near the heater. The TID network comprised three GNSS receivers along baselines of approximately 4 km, located 20 km north of the heater. This paper presents preliminary results from the HEX campaign, including evidence of heating-induced disturbances enhancing propagation between Virginia and Trinidad. The implications of generated irregularities on GNSS will also be discussed.

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

Science.gov (United States)

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

2016-06-01

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

Analysis of plasma dynamic response to modulated electron cyclotron heating in TCV tokamak

International Nuclear Information System (INIS)

Pavlov, I.

2008-01-01

The need of durable, economically acceptable and safe energy sources continues to stimulate studies in the field of thermonuclear fusion. The most successful solution for controlled magnetic fusion is the tokamak. The improvement of tokamak performance depends on the optimization of pressure and current density spatial distributions which can be modified by means of an auxiliary heating and a current drive. In particular, electron cyclotron heating (ECH) is a very important tool for the study and control of basic physical processes governing plasma confinement and stability, particularly because it allows the injection of highly localized intense power. ECH power deposition location plays a crucial role in sawtooth control and suppression, it is also important for tearing mode stabilization, and for implementation of closed loop systems for automatic control/suppression of magnetohydrodynamic activity. A part of the ECH power can be modulated (MECH), and used to identify where the ECH power has been deposited, and can also be useful in the experimental analysis of the electron transport in general. Nevertheless, despite the goal of MECH being a diagnostic and analysis tool, MECH can couple to plasma oscillations, such as sawteeth. MECH-sawtooth phase coupling adds significant complications in ECH deposition location and transport analysis, in some cases making the interpretations of results misleading. This is why it is important to get an insight into the phenomenon of MECH-sawtooth interaction, and to establish the boundaries where conventional types of modulation analysis can be successfully implemented. This thesis presents the analysis and interpretation of perturbative MECH experiments performed in the TCV tokamak with particular attention paid to the non-linear phase coupling of heat waves. TCV is equipped with a very flexible and high power ECH system. Two independent ECH systems permit MECH to be deposited at two different spatial locations, with two

Experiment on transient heat transfer in closed narrow channel

International Nuclear Information System (INIS)

Ochiai, Masaaki

1985-01-01

Heat transfer coefficients and transient pressures in closed narrow channels were obtained experimentally, in order to assess the gap heat transfer models in the computer code WTRLGD which were devised to analyze the internal pressure behavior of waterlogged fuel rods. Gap widths of channels are 0.1--0.5mm to simulate the gap region of waterlogged fuel rods, and test fluids are water (7--89.2 0 C) and Freon-113 (9.2 0 C). The results show that the heater temperature and the pressure measured in the experiments without the DNB occurrence are simulated fairly well by the calculational model of WTRLGD where the heat transfer in a closed narrow channel is evaluated with one-dimensional transient thermal conduction equation and Jens and Lottes' correlation for nucleate boiling. Consequently, it is also suggested that the above equations are available for evaluation of heat flux from fuel to internal water of waterlogged fuel rods. The film boiling heat transfer coefficient was in the same order of that evaluated by Bromley's correlation and the DNB heat flux was smaller than that obtained in quasi-steady experiments with ordinary systems, although the experimental data for them were not enough. (author)

Particle simulation of intense electron cyclotron heating and beat-wave current drive

International Nuclear Information System (INIS)

Cohen, B.I.

1987-01-01

High-power free-electron lasers make new methods possible for heating plasmas and driving current in toroidal plasmas with electromagnetic waves. We have undertaken particle simulation studies with one and two dimensional, relativistic particle simulation codes of intense pulsed electron cyclotron heating and beat-wave current drive. The particle simulation methods here are conventional: the algorithms are time-centered, second-order-accurate, explicit, leap-frog difference schemes. The use of conventional methods restricts the range of space and time scales to be relatively compact in the problems addressed. Nevertheless, experimentally relevant simulations have been performed. 10 refs., 2 figs

THEMIS Observations of the Magnetopause Electron Diffusion Region: Large Amplitude Waves and Heated Electrons

Science.gov (United States)

Tang, Xiangwei; Cattell, Cynthia; Dombeck, John; Dai, Lei; Wilson, Lynn B. III; Breneman, Aaron; Hupack, Adam

2013-01-01

We present the first observations of large amplitude waves in a well-defined electron diffusion region based on the criteria described by Scudder et al at the subsolar magnetopause using data from one Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite. These waves identified as whistler mode waves, electrostatic solitary waves, lower hybrid waves, and electrostatic electron cyclotron waves, are observed in the same 12 s waveform capture and in association with signatures of active magnetic reconnection. The large amplitude waves in the electron diffusion region are coincident with abrupt increases in electron parallel temperature suggesting strong wave heating. The whistler mode waves, which are at the electron scale and which enable us to probe electron dynamics in the diffusion region were analyzed in detail. The energetic electrons (approx. 30 keV) within the electron diffusion region have anisotropic distributions with T(sub e(right angle))/T(sub e(parallel)) > 1 that may provide the free energy for the whistler mode waves. The energetic anisotropic electrons may be produced during the reconnection process. The whistler mode waves propagate away from the center of the "X-line" along magnetic field lines, suggesting that the electron diffusion region is a possible source region of the whistler mode waves.

Electron Heating and Quasiparticle Tunnelling in Superconducting Charge Qubits

Science.gov (United States)

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.

Experimental study of humidity distribution inside electronic enclosure and effect of internal heating

DEFF Research Database (Denmark)

Conseil, Helene; Jellesen, Morten Stendahl; Ambat, Rajan

2016-01-01

on the humidity and temperature profile inside typical electronic enclosures. Defined parameters include external temperature and humidity conditions, temperature and time of the internal heat cycle, thermal mass, and ports/openings size. The effect of the internal humidity on electronic reliability has been......Corrosion reliability of electronic products is a key factor for electronics industry, and today there is a large demand for performance reliability in a wide range of temperature and humidity during day and night time periods. Corrosion failures are still a challenge due to the combined effects...... of temperature, humidity and corrosion accelerating species in the atmosphere. Moreover the surface region of printed circuit board assemblies is often contaminated by various aggressive chemical species.This study describes the overall effect of the exposure to severe climate conditions and internal heat cycles...

Heating power at the substrate, electron temperature, and electron density in 2.45 GHz low-pressure microwave plasma

Science.gov (United States)

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.

Time development of a blast wave with shock heated electrons

International Nuclear Information System (INIS)

Edgar, R.J.; Cox, D.P.

1983-01-01

Accurate approximations are presented for the time development of both edge conditions and internal structures of a blast wave with shock heated electrons, and equal ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform ambient density case) and have negligible external pressure. Account is taken of possible saturation of the thermal conduction flux. The structures evolve smoothly to the adiabatic structures

ELECTRON TEMPERATURE FLUCTUATIONS AND CROSS-FIELD HEAT TRANSPORT IN THE EDGE OF DIII-D

International Nuclear Information System (INIS)

RUDAKOV, DL; BOEDO, JA; MOYER, RA; KRASENINNIKOV, S; MAHDAVI, MA; McKEE, GR; PORTER, GD; STANGEBY, PC; WATKINS, JG; WEST, WP; WHYTE, DG.

2003-01-01

OAK-B135 The fluctuating E x B velocity due to electrostatic turbulence is widely accepted as a major contributor to the anomalous cross-field transport of particles and heat in the tokamak edge and scrape-off layer (SOL) plasmas. This has been confirmed by direct measurements of the turbulent E x B transport in a number of experiments. Correlated fluctuations of the plasma radial velocity v r , density n, and temperature T e result in time-average fluxes of particles and heat given by (for electrons): Equation 1--Λ r ES = r > = 1/B varφ θ ; Equation 2--Q r ES = e (tilde v) r > ∼ 3/2 kT e Λ r ES + 3 n e /2 B varφ e (tilde E) θ > Q conv + Q cond . The first term in Equation 2 is referred to as convective and the second term as conductive heat flux. Experimental determination of fluxes given by Equations 1 and 2 requires simultaneous measurements of the density, temperature and poloidal electric field fluctuations with high spatial and temporal resolution. Langmuir probes provide most readily available (if not the only) tool for such measurements. However, fast measurements of electron temperature using probes are non-trivial and are not always performed. Thus, the contribution of the T e fluctuations to the turbulent fluxes is usually neglected. Here they report results of the studies of T e fluctuations and their effect on the cross-field transport in the SOL of DIII-D

Performance evaluation of a wavy-fin heat sink for power electronics

International Nuclear Information System (INIS)

Lorenzini, Marco; Fabbri, Giampietro; Salvigni, Sandro

2007-01-01

The almost daily increase in dissipated power per unit area of electronic components sets higher and higher demands on the performance of the heat sinks. These must not only be able to dissipate high heat fluxes, but must also keep costs to a minimum and exhibit a reliable behaviour. In this paper a novel, modular heat sink consisting of elements with wavy fin profile which can be pressed together to construct the component is presented. Its performance under steady-state conditions are assessed for the case of forced convection in terms of velocity distribution in the channels and global thermal resistance. Configurations with uniform and non-uniform heat flux are studied and some considerations are made as to the influence of the spacers between fan and heat sink proper

Particle simulation study of electron heating by counter-streaming ion beams ahead of supernova remnant shocks

International Nuclear Information System (INIS)

Dieckmann, M E; Sarri, G; Kourakis, I; Borghesi, M; Bret, A; Perez Alvaro, E

2012-01-01

The growth and saturation of Buneman-type instabilities is examined with a particle-in-cell (PIC) simulation for parameters that are representative for the foreshock region of fast supernova remnant shocks. A dense ion beam and the electrons correspond to the upstream plasma and a fast ion beam to the shock-reflected ions. The purpose of the 2D simulation is to identify the nonlinear saturation mechanisms, the electron heating and potential secondary instabilities that arise from anisotropic electron heating and result in the growth of magnetic fields. We confirm that the instabilities between both ion beams and the electrons saturate by the formation of phase space holes by the beam-aligned modes. The slower oblique modes accelerate some electrons, but they cannot heat up the electrons significantly before they are trapped by the faster beam-aligned modes. Two circular electron velocity distributions develop, which are centred around the velocity of each ion beam. They develop due to the scattering of the electrons by the electrostatic wave potentials. The growth of magnetic fields is observed, but their amplitude remains low. (paper)

Ignition and burn propagation with suprathermal electron auxiliary heating

International Nuclear Information System (INIS)

Han Shensheng; Wu Yanqing

2000-01-01

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

Benchmarking of codes for electron cyclotron heating and electron cyclotron current drive under ITER conditions

NARCIS (Netherlands)

Prater, R.; Farina, D.; Gribov, Y.; Harvey, R. W.; Ram, A. K.; Lin-Liu, Y. R.; Poli, E.; Smirnov, A. P.; Volpe, F.; Westerhof, E.; Zvonkovo, A.

2008-01-01

Optimal design and use of electron cyclotron heating requires that accurate and relatively quick computer codes be available for prediction of wave coupling, propagation, damping and current drive at realistic levels of EC power. To this end, a number of codes have been developed in laboratories

rf experiments on PLT

International Nuclear Information System (INIS)

Hosea, J.; Wilson, J.R.; Hooke, W.

1986-01-01

A variety of rf experiments are being conducted on PLT in order to explore rf techniques which could improve tokamak performance parameters. Of special importance are the studies of ion Bernstein wave (IBW) heating, lower hybrid MHD stabilization and electron heating, down-shifted electron cyclotron heating, and fast wave current drive. Ion Bernstein wave heating results at modest power indicate that the particle confinement time could be enhanced relative to that for fast wave heating in the ion cyclotron range of frequencies (ICRF) and neutral beam heating. At these power levels a conclusive determination of energy confinement scaling with power cannot yet be given. Central sawtooth and m = 1 MHD stabilization is being obtained with centrally peaked lower hybrid (LH) current drive and the central electron temperature is peaking to values (approx.5 keV) well outside the bounds of ''profile consistency.'' In this case the electron energy confinement is apparently increased relative to the ohmic value. The production of relativistic electrons via heating at the down-shifted electron cyclotron (EC) frequency is found to be consistent with theoretical predictions and lends support to the use of this method for heating in relatively high magnetic field devices

Nonlocal heat transport and improved target design for x-ray heating studies at x-ray free electron lasers

Science.gov (United States)

Hoidn, Oliver; Seidler, Gerald T.

2018-01-01

The extremely high-power densities and short durations of single pulses of x-ray free electron lasers (XFELs) have opened new opportunities in atomic physics, where complex excitation-relaxation chains allow for high ionization states in atomic and molecular systems, and in dense plasma physics, where XFEL heating of solid-density targets can create unique dense states of matter having temperatures on the order of the Fermi energy. We focus here on the latter phenomena, with special emphasis on the problem of optimum target design to achieve high x-ray heating into the warm dense matter (WDM) state. We report fully three-dimensional simulations of the incident x-ray pulse and the resulting multielectron relaxation cascade to model the spatial energy density deposition in multicomponent targets, with particular focus on the effects of nonlocal heat transport due to the motion of high energy photoelectrons and Auger electrons. We find that nanoscale high-Z /low-Z multicomponent targets can give much improved energy density deposition in lower-Z materials, with enhancements reaching a factor of 100. This has three important benefits. First, it greatly enlarges the thermodynamic parameter space in XFEL x-ray heating studies of lower-Z materials. Second, it allows the use of higher probe photon energies, enabling higher-information content x-ray diffraction (XRD) measurements such as in two-color XFEL operations. Third, while this is merely one step toward optimization of x-ray heating target design, the demonstration of the importance of nonlocal heat transport establishes important common ground between XFEL-based x-ray heating studies and more traditional laser plasma methods.

In situ heating experiments in hard rock: their objectives and design

International Nuclear Information System (INIS)

Cook, N.G.W.; Witherspoon, P.A.; California Univ., Berkeley

1978-01-01

Of the many alternatives that are being considered for the disposal of nuclear wastes, deep underground burial is favored. The wealth of experience concerning the design and construction of underground excavations does not include the unique effects of heating excavations by radioactive decay, nor the issue of long-term isolation. The effects of heating are important in establishing the feasibility of this method of disposal and are essential for the design of an underground repository. Near-field phenomena around individual canisters can be studied by full-scale experiments, using electrical heaters. The thermal diffusivity of rock is so low that information concerning the interaction between full-scale heaters and of the effects of heating a large volume of rock cannot be measured in full-scale experiments lasting less than a few decades. To overcome this difficulty, a time-scaled heating experiment has been developed in which a reduction in linear scale is accompanied by an acceleration of the time scale to the second power. In this experiment, the linear scale is about a third, so that the time scale is about ten fold

In situ heating experiments in hard rock: their objectives and design

International Nuclear Information System (INIS)

Cook, N.G.W.; Witherspoon, P.A.

1978-01-01

Of the many alternatives that are being considered for the disposal of nuclear wastes, deep underground burial is favored. The wealth of experience concerning the design and construction of underground excavations does not include the unique effects of heating excavations by radioactive decay, nor the issue of long-term isolation. The effects of heating are important in establishing the feasibility of this method of disposal, and are essential for the design of an underground repository. Near-field phenomena around individual canisters can be studied by full-scale experiments, using electrical heaters. The thermal diffusivity of rock is so low that information concerning the interaction between full-scale heaters and of the effects of heating a large volume of rock cannot be measured in full-scale experiments lasting less than a few decades. To overcome this difficulty, a time-scaled heating experiment has been developed in which a reduction in linear scale is accompanied by an acceleration of the time scale to the second power. In this experiment, the linear scale is about a third, so that the time scale is about ten fold

Theory and experiments on RF plasma heating, current drive and profile control in TORE SUPRA

International Nuclear Information System (INIS)

Moreau, D.

1994-01-01

This paper reviews the main experimental and theoretical achievements related to the study of RF heating and non-inductive current drive and particularly phenomena related to the current density profile control and the potentiality of producing stationary enhanced performance regimes: description of the Lower Hybrid (LH) and Ion Cyclotron Resonant Frequency (ICRF) systems; long pulse coupling performance of the RF systems; observation of the transition to the so-called ''stationary LHEP regime'' in which the (flat) central current density and (peaked) electron temperature profiles are fully decoupled; experiments on ICRF sawtooth stabilization with the combined effect of LHCD modifying the current density profile; diffusion of fast electrons generated by LH waves; ramp-up experiments in which the LH power provided a significant part of the resistive poloidal flux and flux consumption scaling; theory of spectral wave diffusion and multipass absorption; fast wave current drive modelling with the Alcyon full wave code; a reflector LH antenna concept. 18 figs., 48 refs

Hot electron plasma equilibrium and stability in the Constance B mirror experiment

International Nuclear Information System (INIS)

Chen, Xing.

1988-04-01

An experimental study of the equilibrium and macroscopic stability property of an electron cyclotron resonance heating (ECRH) generated plasma in a minimum-B mirror is presented. The Constance B mirror is a single cell quadrupole magnetic mirror in which high beta (β ≤ 0.3) hot electron plasmas (T/sub e/≅400 keV) are created with up to 4 kW of ECRH power. The plasma equilibrium profile is hollow and resembles the baseball seam geometry of the magnet which provides the confining magnetic field. This configuration coincides with the drift orbit of deeply trapped particles. The on-axis hollowness of the hot electron density profile is 50 /+-/ 10%, and the pressure profile is at least as hollow as, if not more than, the hot electron density profile. The hollow plasma equilibrium is macroscopically stable and generated in all the experimental conditions in which the machine has been operated. Small macroscopic plasma fluctuations in the range of the hot electron curvature drift frequency sometimes occur but their growth rate is small (ω/sub i//ω/sub r/ ≤ 10 -2 ) and saturate at very low level (δB//bar B/ ≤ 10 -3 ). Particle drift reversal is predicted to occur for the model pressure profile which best fits the experimental data under the typical operating conditions. No strong instability is observed when the plasma is near the drift reversal parameter regime, despite a theoretical prediction of instability under such conditions. The experiment shows that the cold electron population has no stabilizing effect to the hot electrons, which disagrees with current hot electron stability theories and results of previous maximum-B experiments. A theoretical analysis using MHD theory shows that the compressibility can stabilize a plasma with a hollowness of 20--30% in the Constance B mirror well. 57 refs

Suppression of cyclotron instability in Electron Cyclotron Resonance ion sources by two-frequency heating

International Nuclear Information System (INIS)

Skalyga, V.; Izotov, I.; Mansfeld, D.; Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J.; Tarvainen, O.

2015-01-01

Multiple frequency heating is one of the most effective techniques to improve the performance of Electron Cyclotron Resonance (ECR) ion sources. The method increases the beam current and average charge state of the extracted ions and enhances the temporal stability of the ion beams. It is demonstrated in this paper that the stabilizing effect of two-frequency heating is connected with the suppression of electron cyclotron instability. Experimental data show that the interaction between the secondary microwave radiation and the hot electron component of ECR ion source plasmas plays a crucial role in mitigation of the instabilities

Heating tokamaks via the ion-cyclotron and ion-ion hybrid resonances

International Nuclear Information System (INIS)

Perkins, F.W.

1977-04-01

For the ion-ion hybrid resonance it is shown that: (1) the energy absorption occurs via a sequence of mode conversions; (2) a poloidal field component normal to the ion-ion hybrid mode conversion surface strongly influences the mode conversion process so that roughly equal electron and ion heating occurs in the present proton-deuterium experiments, while solely electron heating is predicted to prevail in deuterium-tritium reactors; (3) the ion-ion hybrid resonance suppresses toroidal eigenmodes; and (4) wave absorption in minority fundamental ion-cyclotron heating experiments will be dominated by ion-ion hybrid mode conversion absorption for minority concentrations exceeding roughly 1 percent. For the ion-cyclotron resonance, it is shown that: (1) ion-cyclotron mode conversion leads to surface electron heating; and (2) ion-cyclotron mode conversion absorption dominates fundamental ion-cyclotron absorption thereby preventing efficient ion heating

Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics

Energy Technology Data Exchange (ETDEWEB)

Surducan, E.; Surducan, V.; Neamtu, C., E-mail: camelia.neamtu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies (INCDTIM), 67-103 Donat St., 400293, Cluj‑Napoca (Romania); Limare, A.; Di Giuseppe, E. [Institut de Physique du Globe de Paris (IPGP), Univ. Paris Diderot, UMR CNRS 7154, 1 rue Jussieu, 75005, Paris (France)

2014-12-15

We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm{sup 3} convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

High temperature heat pipe experiments in low earth orbit

International Nuclear Information System (INIS)

Woloshun, K.; Merrigan, M.A.; Sena, J.T.; Critchley, E.

1993-01-01

Although high temperature, liquid metal heat pipe radiators have become a standard component on most high power space power system designs, there is no experimental data on the operation of these heat pipes in a zero gravity or micro-gravity environment. Experiments to benchmark the transient and steady state performance of prototypical heat pipe space radiator elements are in preparation for testing in low earth orbit. It is anticipated that these heat pipes will be tested aborad the Space Shuttle in 1995. Three heat pipes will be tested in a cargo bay Get Away Special (GAS) canister. The heat pipes are SST/potassium, each with a different wick structure; homogeneous, arterial, and annular gap, the heat pipes have been designed, fabricated, and ground tested. In this paper, the heat pipe designs are specified, and transient and steady-state ground test data are presented

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

Science.gov (United States)

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.

Electron Heating and Acceleration in a Reconnecting Magnetotail

Science.gov (United States)

El-Alaoui, M.; Zhou, M.; Lapenta, G.; Berchem, J.; Richard, R. L.; Schriver, D.; Walker, R. J.

2017-12-01

Electron heating and acceleration in the magnetotail have been investigated intensively. A major site for this process is the reconnection region. However, where and how the electrons are accelerated in a realistic three-dimensional X-line geometry is not fully understood. In this study, we employed a three-dimensional implicit particle-in-cell (iPIC3D) simulation and large-scale kinetic (LSK) simulation to address these problems. We modeled a magnetotail reconnection event observed by THEMIS in an iPIC3D simulation with initial and boundary conditions given by a global magnetohydrodynamic (MHD) simulation of Earth's magnetosphere. The iPIC3D simulation system includes the region of fast outflow emanating from the reconnection site that drives dipolarization fronts. We found that current sheet electrons exhibit elongated (cigar-shaped) velocity distributions with a higher parallel temperature. Using LSK we then followed millions of test electrons using the electromagnetic fields from iPIC3D. We found that magnetotail reconnection can generate power law spectra around the near-Earth X-line. A significant number of electrons with energies higher than 50 keV are produced. We identified several acceleration mechanisms at different locations that were responsible for energizing these electrons: non-adiabatic cross-tail drift, betatron and Fermi acceleration. Relative contributions to the energy gain of these high energy electrons from the different mechanisms will be discussed.

Heat transfer and critical heat flux in a spiral flow in an asymmetrical heated tube

International Nuclear Information System (INIS)

Boscary, J.; Association Euratom-CEA, Centre d'Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance

1997-03-01

The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author)

Comparison of electron cloud simulation and experiments in the high-current experiment

International Nuclear Information System (INIS)

Cohen, R.H.; Friedman, A.; Covo, M. Kireeff; Lund, S.M.; Molvik, A.W.; Bieniosek, F.M.; Seidl, P.A.; Vay, J.-L.; Verboncoeur, J.; Stoltz, P.; Veitzer, S.

2004-01-01

A set of experiments has been performed on the High-Current Experiment (HCX) facility at LBNL, in which the ion beam is allowed to collide with an end plate and thereby induce a copious supply of desorbed electrons. Through the use of combinations of biased and grounded electrodes positioned in between and downstream of the quadrupole magnets, the flow of electrons upstream into the magnets can be turned on or off. Properties of the resultant ion beam are measured under each condition. The experiment is modeled via a full three-dimensional, two species (electron and ion) particle simulation, as well as via reduced simulations (ions with appropriately chosen model electron cloud distributions, and a high-resolution simulation of the region adjacent to the end plate). The three-dimensional simulations are the first of their kind and the first to make use of a timestep-acceleration scheme that allows the electrons to be advanced with a timestep that is not small compared to the highest electron cyclotron period. The simulations reproduce qualitative aspects of the experiments, illustrate some unanticipated physical effects, and serve as an important demonstration of a developing simulation capability

Electron cyclotron heating of a tokamak reactor at down-shifted frequencies

International Nuclear Information System (INIS)

Fidone, I.; Giruzzi, G.; Mazzucato, E.

1985-01-01

The absorption of electron cyclotron waves in a hot and dense tokamak plasma is investigated for the case of the extraordinary mode for outside launching. It is shown that, for electron temperatures T/sub e/ greater than or equal to 5 keV, strong absorption occurs for oblique propagation at frequencies significantly below the electron gyrofrequency at the plasma center. A new density dependence of the wave absorption is found which is more favorable for plasma heating than the familiar n/sub e/ -1 scaling

Proceedings of the 12. Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Heating

International Nuclear Information System (INIS)

Giruzzi, Gerardo

2003-01-01

The 12. Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Heating was held in Aix-en-Provence (France) from 13 to 16 May 2002. The meeting was hosted by the Association Euratom-CEA sur la Fusion (CEA/Cadarache, France), with additional financial support from: - Region Provence-Alpes Cote d'Azur - The City of Aix-en-Provence - Communaute de l'Agglomeration du Pays d'Aix - Thales Electron Devices (France) - Alstom Magnets and Superconductors (France) - Spinner GmbH (Germany). The members of the local organizing committee were: G. Giruzzi, M. Lennholm, R. Magne and V. Poli, from CEA/Cadarache. The composition of the International Programme Committee was the following: M. Bornatici (Italy), A. Costley (ITER), E. de la Luna (Spain), G. Giruzzi (France), W. Kasparek (Germany), B. Lloyd (UK), J. Lohr (USA), K. Sakamoto (Japan). The subjects of the meeting were classified in four main topics: Electron Cyclotron Theory; Electron Cyclotron Emission; Electron Cyclotron Heating and Current Drive Experiments; Electron Cyclotron Technology. The results presented in these topics have been summarised in the closing session by E. Westerhof, A. Kraemer-Flecken, T. Goodman and G. Bosia, respectively. The workshop was attended by 85 participants from 18 countries, providing 10 invited talks, 30 oral presentations and 50 posters. The success of the workshop is mainly due to the amount and quality of their work and of their presentations. The generosity of the sponsors, the selection and advice work of the International Programme Committee, as well as the contribution of the chairmen and of the summary speakers should also be warmly acknowledged. The papers in this collection have been reproduced directly from the authors' manuscripts, provided either as camera-ready texts or as pdf files. The constraints on the papers lengths and formats have been kept to a minimum, on purpose. This series of workshops has now reached a good level of maturity, with well established

The Cryogenic Test Bed experiments: Cryogenic heat pipe flight experiment CRYOHP (STS-53). Cryogenic two phase flight experiment CRYOTP (STS-62). Cryogenic flexible diode flight experiment CRYOFD

Science.gov (United States)

Thienel, Lee; Stouffer, Chuck

1995-09-01

This paper presents an overview of the Cryogenic Test Bed (CTB) experiments including experiment results, integration techniques used, and lessons learned during integration, test and flight phases of the Cryogenic Heat Pipe Flight Experiment (STS-53) and the Cryogenic Two Phase Flight Experiment (OAST-2, STS-62). We will also discuss the Cryogenic Flexible Diode Heat Pipe (CRYOFD) experiment which will fly in the 1996/97 time frame and the fourth flight of the CTB which will fly in the 1997/98 time frame. The two missions tested two oxygen axially grooved heat pipes, a nitrogen fibrous wick heat pipe and a 2-methylpentane phase change material thermal storage unit. Techniques were found for solving problems with vibration from the cryo-collers transmitted through the compressors and the cold heads, and mounting the heat pipe without introducing parasitic heat leaks. A thermally conductive interface material was selected that would meet the requirements and perform over the temperature range of 55 to 300 K. Problems are discussed with the bi-metallic thermostats used for heater circuit protection and the S-Glass suspension straps originally used to secure the BETSU PCM in the CRYOTP mission. Flight results will be compared to 1-g test results and differences will be discussed.

Cryogenic systems for proof of the principle experiment of coherent electron cooling at RHIC

Energy Technology Data Exchange (ETDEWEB)

Huang, Yuenian; Belomestnykh, Sergey; Brutus, Jean Clifford; Lederle, Dewey; Orfin, Paul; Skaritka, John; Soria, Victor; Tallerico, Thomas; Than, Roberto [Collider Accelerator Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)

2014-01-29

The Coherent electron Cooling (CeC) Proof of Principle (PoP) experiment is proposed to be installed in the Relativistic Heavy Ion Collider (RHIC) to demonstrate proton and ion beam cooling with this new technique that may increase the beam luminosity in certain cases, by as much as tenfold. Within the scope of this project, a 112 MHz, 2MeV Superconducting Radio Frequency (SRF) electron gun and a 704 MHz 20MeV 5-cell SRF cavity will be installed at IP2 in the RHIC ring. The superconducting RF electron gun will be cooled in a liquid helium bath at 4.4 K. The 704 MHz 5-cell SRF cavity will be cooled in a super-fluid helium bath at 2.0 K. This paper discusses the cryogenic systems designed for both cavities. For the 112 MHz cavity cryogenic system, a condenser/boiler heat exchanger is used to isolate the cavity helium bath from pressure pulses and microphonics noise sources. For the 704 MHz 5-cell SRF cavity, a heat exchanger is also used to isolate the SRF cavity helium bath from noise sources in the sub-atmospheric pumping system operating at room temperature. Detailed designs, thermal analyses and discussions for both systems will be presented in this paper.

Influence of non-collisional laser heating on the electron dynamics in dielectric materials

Science.gov (United States)

Barilleau, L.; Duchateau, G.; Chimier, B.; Geoffroy, G.; Tikhonchuk, V.

2016-12-01

The electron dynamics in dielectric materials induced by intense femtosecond laser pulses is theoretically addressed. The laser driven temporal evolution of the energy distribution of electrons in the conduction band is described by a kinetic Boltzmann equation. In addition to the collisional processes for energy transfer such as electron-phonon-photon and electron-electron interactions, a non-collisional process for photon absorption in the conduction band is included. It relies on direct transitions between sub-bands of the conduction band through multiphoton absorption. This mechanism is shown to significantly contribute to the laser heating of conduction electrons for large enough laser intensities. It also increases the time required for the electron distribution to reach the equilibrium state as described by the Fermi-Dirac statistics. Quantitative results are provided for quartz irradiated by a femtosecond laser pulse with a wavelength of 800 nm and for intensities in the range of tens of TW cm-2, lower than the ablation threshold. The change in the energy deposition induced by this non-collisional heating process is expected to have a significant influence on the laser processing of dielectric materials.

Characteristics of plasma in uranium atomic beam produced by electron-beam heating

International Nuclear Information System (INIS)

Ohba, Hironori; Shibata, Takemasa

2000-08-01

The electron temperature of plasma and the ion flux ratio in the uranium atomic beam produced by electron-beam heating were characterized with Langmuir probes. The electron temperature was 0.13 eV, which was lower than the evaporation surface temperature. The ion flux ratio to atomic beam flux was more than 3% at higher evaporation rates. The ion flux ratio has increased with decreasing acceleration energy of the electron-beam under constant electron-beam power. This is because of an increase of electron-beam current and a large ionization cross-section of uranium by electron-impact. It was confined that the plasma is produced by electron-impact ionization of the evaporated atoms at the evaporation source. (author)

Experiments and procedures for bottom-heating heat-transfer experiments through UO2 debris beds in sodium

International Nuclear Information System (INIS)

Sowa, E.S.; Pedersen, D.R.; Pavlik, J.; Purviance, R.

1982-01-01

Real materials experiments in heat transfer through beds of UO 2 in sodium have been performed at Argonne National Laboratory over a period of years. The most recent method utilizes the resistive heating in a sheet tungsten filament located at the base of the debris container. A schematic diagram of the apparatus is shown. The tungsten is clamped between two water cooled copper electrodes. The filament is a sheet of tungsten 0.15 mm thick, 5 cm wide and 18 cm long. Two 6.5 mm thick sheets of boron nitride sandwich the filament. The upper face of the upper boron nitride sheet is in intimate contact with the bottom of the debris container. Temperatures are measured at various levels in the bed as well as in the boron nitride plate. In addition, the sodium pool temperature is measured by the thermocouple. The heat transferral through the bed is measured by the temperature difference and mass flowrate in a NaK condenser located above the debris bed. The NaK inlet and outlet temperatures are recorded individually, as well as, differentially

Recent DIII-D high power heating and current drive experiments

International Nuclear Information System (INIS)

Simonen, T.C.; Jackson, G.L.; Mahdavi, M.A.; Petrie, T.W.; Politzer, P.A.; Taylor, T.S.; Lazarus, E.A.

1994-02-01

This paper describes recent DIII-D high power heating and current drive experiments. Describes are experiments with improved wall conditioning, divertor particle pumping, radiative divertor experiments, studies of plasma shape and high poloidal beta

The design of a heat transfer liquid metal MHD experiment for ALEX [Argonne Liquid-Metal Experiment

International Nuclear Information System (INIS)

Picologlou, B.F.; Reed, C.B.; Hua, T.Q.; Lavine, A.S.

1988-01-01

An experiment to study heat transfer in liquid metal MHD flow, under conditions relevant to coolant channels for tokamak first wall and high heat flux devices, is described. The experimental configuration is a rectangular duct in a transverse magnetic field, heated on one wall parallel to the field. The specific objective of the experiment is to resolve important issues related to the presence and heat transfer characteristics of wall jets and flow instabilities in MHD flows in rectangular duct with electrically conducting walls. Available analytical tools for MHD thermal hydraulics have been used in the design of the test article and its instrumentation. Proposed tests will cover a wide range of Peclet and Hartmann numbers and interaction parameters. 14 refs., 3 figs., 1 tab

The effect of quantum correction on plasma electron heating in ultraviolet laser interaction

Energy Technology Data Exchange (ETDEWEB)

Zare, S.; Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir; Anvari, A. [Department of Physics, Sharif University of Technology, P.O. Box 11365-9567, Tehran (Iran, Islamic Republic of); Yazdani, E. [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Hora, H. [Department of Theoretical Physics, University of New South Wales, Sydney 2052 (Australia)

2015-04-14

The interaction of the sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in the collision frequency, the electron heating and the ion block generation in plasma are studied. It is found that due to the quantum correction, the electron heating increases considerably and the electron temperature uniformly reaches up to the maximum value of 4.91 × 10{sup 7 }K. Considering the quantum correction, the electron temperature at the laser initial coupling stage is improved more than 66.55% of the amount achieved in the classical model. As a consequence, by the modified collision frequency, the ion block is accelerated quicker with higher maximum velocity in comparison with the one by the classical collision frequency. This study proves the necessity of considering a quantum mechanical correction in the collision frequency at high plasma temperatures.

The Laser ablation of a metal foam: The role of electron-phonon coupling and electronic heat diffusivity

Science.gov (United States)

Rosandi, Yudi; Grossi, Joás; Bringa, Eduardo M.; Urbassek, Herbert M.

2018-01-01

The incidence of energetic laser pulses on a metal foam may lead to foam ablation. The processes occurring in the foam may differ strongly from those in a bulk metal: The absorption of laser light, energy transfer to the atomic system, heat conduction, and finally, the atomistic processes—such as melting or evaporation—may be different. In addition, novel phenomena take place, such as a reorganization of the ligament network in the foam. We study all these processes in an Au foam of average porosity 79% and an average ligament diameter of 2.5 nm, using molecular dynamics simulation. The coupling of the electronic system to the atomic system is modeled by using the electron-phonon coupling, g, and the electronic heat diffusivity, κe, as model parameters, since their actual values for foams are unknown. We show that the foam coarsens under laser irradiation. While κe governs the homogeneity of the processes, g mainly determines their time scale. The final porosity reached is independent of the value of g.

Thermal management of electronics using phase change material based pin fin heat sinks

International Nuclear Information System (INIS)

Baby, R; Balaji, C

2012-01-01

This paper reports the results of an experimental study carried out to explore the thermal characteristics of phase change material based heat sinks for electronic equipment cooling. The phase change material (PCM) used in this study is n – eicosane. All heat sinks used in the present study are made of aluminium with dimensions of 80 × 62 mm 2 base with a height of 25 mm. Pin fins acts as the thermal conductivity enhancer (TCE) to improve the distribution of heat more uniformly as the thermal conductivity of the PCM is very low. A total of three different pin fin heat sink geometries with 33, 72 and 120 pin fins filled with phase change materials giving rise to 4%, 9% and 15% volume fractions of the TCE respectively were experimentally investigated. Baseline comparisons are done with a heat sink filled with PCM, without any fin. Studies are conducted for heat sinks on which a uniform heat load is applied at the bottom for the finned and unfinned cases. The effect of pin fins of different volume fractions with power levels ranging from 4 to 8 W corresponding to a heat flux range of 1. 59 to 3.17 kW/m 2 , was explored in this paper. The volume fraction of the PCM (PCM volume / (Total volume – fin volume)) is also varied as 0. 3, 0.6 and 1 to determine the effect of PCM volume on the overall performance of the electronic equipment.

Recent DIII-D high power heating and current drive experiments

International Nuclear Information System (INIS)

Simonen, T.C.; Jackson, G.L.; Lazarus, E.A.; Mahdavi, M.A.; Petrie, T.W.; Politzer, P.A.; Taylor, T.S.

1995-01-01

This paper describes recent DIII-D high power heating and current drive experiments. Described are experiments with improved wall conditioning, divertor particle pumping, radiative divertor experiments, studies of plasma shape and high poloidal β. ((orig.))

Recent DIII-D high power heating and current drive experiments

Energy Technology Data Exchange (ETDEWEB)

Simonen, T.C. [General Atomics, San Diego, CA (United States); Jackson, G.L. [General Atomics, San Diego, CA (United States); Lazarus, E.A. [Oak Ridge National Lab., TN (United States); Mahdavi, M.A. [General Atomics, San Diego, CA (United States); Petrie, T.W. [General Atomics, San Diego, CA (United States); Politzer, P.A. [General Atomics, San Diego, CA (United States); Taylor, T.S. [General Atomics, San Diego, CA (United States); DIII-D Team

1995-01-01

This paper describes recent DIII-D high power heating and current drive experiments. Described are experiments with improved wall conditioning, divertor particle pumping, radiative divertor experiments, studies of plasma shape and high poloidal {beta}. ((orig.)).

Observation of Ω mode electron heating in dusty argon radio frequency discharges

Energy Technology Data Exchange (ETDEWEB)

Killer, Carsten; Bandelow, Gunnar; Schneider, Ralf; Melzer, André [Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, 17489 Greifswald (Germany); Matyash, Konstantin [Universitätsrechenzentrum, Ernst-Moritz-Arndt-Universität Greifswald, 17489 Greifswald (Germany)

2013-08-15

The time-resolved emission of argon atoms in a dusty plasma has been measured with phase-resolved optical emission spectroscopy using an intensified charge-coupled device camera. For that purpose, three-dimensional dust clouds have been confined in a capacitively coupled rf argon discharge with the help of thermophoretic levitation. While electrons are exclusively heated by the expanding sheath (α mode) in the dust-free case, electron heating takes place in the entire plasma bulk when the discharge volume is filled with dust particles. Such a behavior is known as Ω mode, first observed in electronegative plasmas. Furthermore, particle-in-cell simulations have been carried out, which reproduce the trends of the experimental findings. These simulations support previous numerical models showing that the enhanced atomic emission in the plasma can be attributed to a bulk electric field, which is mainly caused by the reduced electrical conductivity due to electron depletion.

Transitions to improved core electron heat confinement in JT-II plasmas

International Nuclear Information System (INIS)

Estrada, T.; Medina, F.; Ascasibar, E.; Balbin, R.; Castejon, F.; Hidalgo, C.; Lopez-Bruna, D.; Petrov, S.

2008-01-01

Transitions to improved core electron heat confinement are triggered by low order rational magnetic surfaces in TJ-II ECH plasmas. Transitions triggered by the rational surface n=4/m=2 show an increase in the ion temperature synchronized with the increase in the electron temperature. SXR measurements demonstrate that, under certain circumstances, the rational surface positioned inside the plasma core region precedes and provides a trigger for the transition. (author)

Anomalous heating and plasmoid formation in pulsed power driven magnetic reconnection experiments

Science.gov (United States)

Hare, Jack

2017-10-01

Magnetic reconnection is an important process occurring in various plasma environments, including high energy density plasmas. In this talk we will present results from a recently developed magnetic reconnection platform driven by the MAGPIE pulsed power generator (1 MA, 250 ns) at Imperial College London. In these experiments, supersonic, sub-Alfvénic plasma flows collide, bringing anti-parallel magnetic fields into contact and producing a well-defined, elongated reconnection layer. This layer is long-lasting (>200 ns, > 10 hydrodynamic flow times) and is diagnosed using a suite of high resolution, spatially and temporally resolved diagnostics which include laser interferometry, Thomson scattering and Faraday rotation imaging. We observe significant heating of the electrons and ions inside the reconnection layer, and calculate that the heating must occur on time-scales far faster than can be explained by classical mechanisms. Possible anomalous mechanisms include in-plane electric fields caused by two-fluid effects, and enhanced resistivity and viscosity caused by kinetic turbulence. We also observe the repeated formation of plasmoids in the reconnection layer, which are ejected outwards along the layer at super-Alfvénic velocities. The O-point magnetic field structure of these plasmoids is determined using in situ magnetic probes, and these plasmoids could also play a role in the anomalous heating of the electrons and ions. In addition, we present further modifications to this experimental platform which enable us to study asymmetric reconnection or measure the out-of-plane magnetic field inside the plasmoids. This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) Grant No. EP/N013379/1, and by the U.S. Department of Energy (DOE) Awards No. DE-F03-02NA00057 and No. DE-SC-0001063.

Preliminary experiments of electronic duplication

International Nuclear Information System (INIS)

Fay, Bernard

1974-01-01

Systems of electron sputtering (at the unit scale) use as master mask a photocathode with localized emitting zones. Emitted electrons are accelerated and focussed on a silicon substrate covered with an electrosensitive resin. The very high definition associated with electron masking is obtained whatever the complexity of the master mask is, for a printing duration of the order of the minute. This is a duplication method without any contact that prevents the master mask from any mechanical erosion. Alignment of the successive masks is obtained from an electric signal directly usable through an automatic alignment system. Experiments using the apparatus for reproducing masks through an electronic image or ''electronic duplicator'' developed in Thomson-CSF Laboratory at Corbeville, are presented [fr

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

International Nuclear Information System (INIS)

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

1996-05-01

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

Transient cooling of electronics using phase change material (PCM)-based heat sinks

International Nuclear Information System (INIS)

Kandasamy, Ravi; Wang Xiangqi; Mujumdar, Arun S.

2008-01-01

Use of a phase change material (PCM)-based heat sink in transient thermal management of plastic quad flat package (QFP) electronic devices was investigated experimentally and numerically. Results show that increased power inputs enhance the melting rate as well as the thermal performance of the PCM-based heat sinks until the PCM is fully melted. A three-dimensional computational fluid dynamics model was proposed to simulate the problem and demonstrated good agreement with experimental data. Results indicate the potential for PCM-based heat sinks for use in intermittent-use devices

Capillary Pumped Heat Transfer (CHT) Experiment

Science.gov (United States)

Hallinan, Kevin P.; Allen, J. S.

1998-01-01

The operation of Capillary Pumped Loops (CPL's) in low gravity has generally been unable to match ground-based performance. The reason for this poorer performance has been elusive. In order to investigate the behavior of a CPL in low-gravity, an idealized, glass CPL experiment was constructed. This experiment, known as the Capillary-driven Heat Transfer (CHT) experiment, was flown on board the Space Shuttle Columbia in July 1997 during the Microgravity Science Laboratory mission. During the conduct of the CHT experiment an unexpected failure mode was observed. This failure mode was a result of liquid collecting and then eventually bridging the vapor return line. With the vapor return line blocked, the condensate was unable to return to the evaporator and dry-out subsequently followed. The mechanism for this collection and bridging has been associated with long wavelength instabilities of the liquid film forming in the vapor return line. Analysis has shown that vapor line blockage in present generation CPL devices is inevitable. Additionally, previous low-gravity CPL tests have reported the presence of relatively low frequency pressure oscillations during erratic system performance. Analysis reveals that these pressure oscillations are in part a result of long wavelength instabilities present in the evaporator pores, which likewise lead to liquid bridging and vapor entrapment in the porous media. Subsequent evaporation to the trapped vapor increases the vapor pressure. Eventually the vapor pressure causes ejection of the bridged liquid. Recoil stresses depress the meniscus, the vapor pressure rapidly increases, and the heated surface cools. The process then repeats with regularity.

Propagation of a surface electromagnetic wave in a plasma with allowance for electron heating

International Nuclear Information System (INIS)

Boev, A.G.; Prokopov, A.V.

1978-01-01

Considered is propagation of a surface high-frequency wave in a semibounded plasma, which electron component is heated within the wave field. Dissipative effects are considered small, that is possible if wave frequency is much higher than the collision frequency and phase velocity of wave considerably exceeds electron heat velocity. Under conditions of anomalous skin-effect the distributions of electron temperature and wave damping have been found. It is established, that higher electron temperature on the boundary results in a higher decrease of temperature inside a plasma, far from the boundary temperature decreases exponentially; damping coefficient under anomalous skin-effect conditions is characterized by a stronger dependence not only on the wave amplitude, but as well as on gas pressure and wave frequency in comparison with normal conditions

TMX-U thermal-barrier experiments

International Nuclear Information System (INIS)

Simonen, T.C.; Allen, S.L.; Barter, J.D.

1988-01-01

This review of thermal-barrier experiments in the Tandem Mirror Experiment Upgrade (TMX-U) describes our progress at Lawrence Livermore National Laboratory in plasma confinement and central-cell heating. Thermal barriers in TMX-U improved axial confinement by two orders of magnitude over a limited range of densities, compared with confinement in single-cell mirrors at the same ion temperature. Our study shows that central-cell radial nonambipolar confinement scales as neoclassical theory and can be eliminated by floating the end walls. Radial ambipolar losses can also be measured and reduced. The electron energy balance is improved in tandem mirrors to near classical, resulting in T/sub e/ up to 0.28 keV. Electron cyclotron heating (ECH) efficiencies up to 42 percent, with low levels of electron microinstability, were achieved when hot electrons in the thermal barrier were heated to average betas as large as 15 percent. The hot-electron distribution is measured from X rays and is modeled by a Fokker-Planck code that includes heating from cavity radio-frequency (RF) fields. Neutral-beam injection in the central cell created average ion betas up to 5 percent with radial profiles of hot ions that are modeled accurately by a radial Fokker-Planck code. Gas fueling between two fundamental ion cyclotron heating (ICH) resonances resulted in symmetrical heating of passing ions toward both ends

Plasma density profiles and finite bandwidth effects on electron heating

International Nuclear Information System (INIS)

Spielman, R.B.; Mizuno, K.; DeGroot, J.S.; Bollen, W.M.; Woo, W.

1980-01-01

Intense, p-polarized microwaves are incident on an inhomogeneous plasma in a cylindrical waveguide. Microwaves are mainly absorbed by resonant absorption near the critical surface (where the plasma frequency, ω/sub pe/, equals the microwave frequency, ω/sub o/). The localized plasma waves strongly modify the plasma density. Step-plateau density profiles or a cavity are created depending on the plasma flow speed. Hot electron production is strongly affected by the microwave bandwidth. The hot electron temperature varies as T/sub H/ is proportional to (Δ ω/ω) -0 25 . As the hot electron temperature decreases with increasing driver bandwidth, the hot electron density increases. This increase is such that the heat flux into the overdense region (Q is proportional to eta/sub H/T/sub H/ 3 2 ) is nearly constant

Stochastic heating in the cyclotron resonance of electrons; Calentamiento estocastico en la resonancia ciclotronica de los electrones

Energy Technology Data Exchange (ETDEWEB)

Gutierrez T, C.; Hernandez A, O. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

1999-07-01

The study of the different schemes of plasma heating by radiofrequency waves is a very actual problem related with the plasma heating in different machines and the particle acceleration mechanisms. In this work, it is obtained the expression for the temporal evolution of the energy absorbed in the cyclotron resonance of electrons where it is showed the stochastic character of the energy absorption. It is obtained the stochastic criteria in a magnetic configuration of an Ecr type plasma source. (Author)

Operational experience with SLAC's beam containment electronics

International Nuclear Information System (INIS)

Constant, T.N.; Crook, K.; Heggie, D.

1977-03-01

Considerable operating experience was accumulated at SLAC with an extensive electronic system for the containment of high power accelerated beams. Average beam power at SLAC can approach 900 kilowatts with the potential for burning through beam stoppers, protection collimators, and other power absorbers within a few seconds. Fast, reliable, and redundant electronic monitoring circuits have been employed to provide some of the safeguards necessary for minimizing the risk to personnel. The electronic systems are described, and the design philosophy and operating experience are discussed

Wave trajectory and electron cyclotron heating in tokamak plasmas

International Nuclear Information System (INIS)

Tanaka, S.; Maekawa, T.; Terumichi, Y.; Hamada, Y.

1980-01-01

Wave trajectories in high density tokamak plasmas are studied numerically. Results show that the ordinary wave injected at an appropriate incident angle can propagate into the dense plasmas and is mode-converted to the extraordinary wave at the plasma cutoff, is further converted to the electron Bernstein wave during passing a loop or a folded curve near the upper hybrid resonance layer, and is cyclotron damped away, resulting in local electron heating before arriving at the cyclotron resonance layer. Similar trajectory and damping are obtained when a microwave in a form of extraordinary wave is injected quasi-perpendicularly in the direction of decreasing toroidal field

Mixed convection heat transfer experiments using analogy concept

International Nuclear Information System (INIS)

Ko, Bong Jin; Chung, Bum Jin; Lee, Won Jea

2009-01-01

A Series of the turbulent mixed convective heat transfer experiments in a vertical cylinder was carried out. In order to achieve high Gr and/or Ra with small scale test rigs, the analogy concept was adopted. Using the concept, heat transfer systems were simulated by mass transfer systems, and large Grashof numbers could be achieved with reasonable facility heights. The tests were performed with buoyancy-aided flow and opposed flow for Reynolds numbers from 4,000 to 10,000 with a constant Grashof number, Gr H of 6.2 x 10 9 and Prandtl number of about 2,000. The test results reproduced the typical of the mixed convection heat transfer phenomena in a turbulent situation and agree well with the experimental study performed by Y. Palratan et al. The analogy experimental method simulated the mixed convection heat transfer phenomena successfully and seems to be a useful tool for heat transfer studies for VHTR as well as the systems with high buoyancy condition and high Prandtl number

Ion-electron recombination in merged-beams experiments

International Nuclear Information System (INIS)

Schmidt, H.T.

1994-01-01

In the present thesis, studies of recombination processes applying the technique of merged beams of fast ions and electrons are described. The main advantage of this technique is that the low relative velocity of ions and electrons necessary for these investigations can be achieved, at the same time as the velocity of the ions relative to the molecules of the residual gas is high. The high ion velocity leads to a very low reaction cross section for the leading contribution to the background signal, the capture of electrons in collisions with residual gas molecules. The experimental technique is described, emphasizing the electron beam velocity distribution and its relation to the energy resolution of the experiments. The presentation of the process of electron cooling is aimed at introducing this process as a tool for merged-beams experiments in storage rings rather than investigating the process itself. The non-resonant process of radiative recombination for non-fully stripped ions, showing evidence of incomplete screening is presented. Experimental investigation of dielectronic recombination is presented. Results of measurements of this process for He-like ions form the Aarhus single-pass experiment and the Heidelberg storage ring experiment are compared. Recombination is reduced from being the aim of the investigation to being a tool for high-precision measurements of the lifetimes of the 1s2s 3 S metastable states of HE-like ions of boron, carbon, and nitrogen, performed at the Heidelberg storage ring. The experiment is concerned with the process of dissociative recombination of molecular hydrogen ions. The discussion of this experiment emphasizes the distribution of population on the different vibrational levels of the ions in the initial state. In particular, a laser photo-dissociation technique was introduced to reduce the number of initial levels in the experiment. (EG) 24 refs

First Experience from the World Largest fully commercial Solar Heating Plant

DEFF Research Database (Denmark)

Heller, Alfred; Furbo, Simon

1997-01-01

The first experience from the largest solar heating plant in the world is given. The plant is situated in Marstal and is has a total area of 8000 square m.......The first experience from the largest solar heating plant in the world is given. The plant is situated in Marstal and is has a total area of 8000 square m....

Magnetic behaviors of cataclasites within Wenchuan earthquake fault zone in heating experiments

Science.gov (United States)

Zhang, L.; Li, H.; Sun, Z.; Chou, Y. M.; Cao, Y., Jr.; Huan, W.; Ye, X.; He, X.

2017-12-01

Previous rock magnetism of fault rocks were used to trace the frictional heating temperature, however, few studies are focus on different temperatures effect of rock magnetic properties. To investigate rock magnetic response to different temperature, we conducted heating experiments on cataclasites from the Wenchuan earthquake Fault Scientific Drilling borehole 2 (WFSD-2) cores. Samples of cataclasites were obtained using an electric drill with a 1 cm-diameter drill pipe from 580.65 m-depth. Experiments were performed by a Thermal-optical measurement system under argon atmosphere and elevated temperatures. Both microstructural observations and powder X-ray diffraction analyses show that feldspar and quartz start to melt at 1100 ° and 1300 ° respectively. Magnetic susceptibility values of samples after heating are higher than that before heating. Samples after heating at 700 and 1750 ° have the highest values of magnetic susceptibility. Rock magnetic measurements show that the main ferromagnetic minerals within samples heated below 1100 ° (400, 700, 900 and 1100 °) are magnetite, which is new-formed by transformation of paramagnetic minerals. The χferri results show that the quantity of magnetite is bigger at sample heated by 700° experiment than by 400, 900 and 1100° experiments. Based on the FORC diagrams, we consider that magnetite grains are getting finer from 400 to 900°, and growing coarser when heated from 900 to 1100 °. SEM-EDX results indicate that the pure iron are formed in higher temperature (1300, 1500 and 1750 °), which present as framboids with size values of samples when heated at 400, 700, 900 and 1100°, while the neoformed pure iron is responsible to the higher magnetic susceptibility values of samples when heated at 1300, 1500 and 1750°.

New operational spaces for the electron cyclotron resonance heating at ASDEX upgrade

International Nuclear Information System (INIS)

Hoehnle, Hendrik Sebastian

2012-01-01

In this thesis, new electron cyclotron resonance heating (ECRH) scenarios were developed for an extension of the operational space at the tokamak ASDEX Upgrade in view of ITER compatibility. In the last years, the first wall material at ASDEX Upgrade was changed from graphite to tungsten, and the ECRH is needed to control the tungsten concentration in the plasma core. But, in ITER-like plasma discharges at ASDEX Upgrade, the usage of the ECRH in the typically used second harmonic extraordinary polarised mode (X2 mode) is limited. In these ITER-scenarios a small safety factor should be achieved, which implements an increase of the plasma current at ASDEX Upgrade. A higher plasma current and a high confinement lead to a raised density and for the ITER scenario to an electron density above the cutoff of the X2 mode at ASDEX Upgrade. Therefore, the X2 mode is reflected at the cutoff layer and cannot be used for central heating and the control of the tungsten concentration. One possibility to overcome this problem is to apply the third harmonic mode at reduced magnetic field. Here the cutoff is increased by 33% due to the dependence on the magnetic field. However, at the reachable plasma parameters at the reduced field the absorption of the X3 mode is incomplete (60-70 %) and the shine-trough power can destroy microwave sensitive components in ASDEX Upgrade. To solve this problem the magnetic field has to be optimized. A slightly increased magnetic field from 1.7 T to 1.8 T moves the second harmonic resonance in the region of confined plasma with high temperatures and density, so that this resonance can act as beam dump. The deposition in the plasma core is still central enough for the tungsten control ability of the ECRH. The benefit of the beam dump was verified in experiments with two different magnetic fields (1.7 T and 1.8 T). In case of the higher magnetic field, the stray radiation was reduced; simultaneously the electron temperature was increased. In addition

The Compact Ignition Tokamak and electron cyclotron heating: Description of need; assessment of prospects

International Nuclear Information System (INIS)

Ignat, D.W.; Cohn, D.R.; Woskov, P.P.

1989-01-01

The CIT will benefit from auxiliary heating of 10 to 40 MW. The schedules of both the CIT construction project and the operating plan contain adequate time to develop and implement ECH systems based on the gyrotron and the induction free electron laser (IFEL). Each approach has advantages and is the object of R and D at the level of many millions of dollars per year. While the gyrotron is further advanced in terms of power and pulse length achieved, rapid progress is scheduled for the IFEL, including experiments on tokamaks. Plans of CIT, gyrotron, and IFEL make 1992 an appropriate time frame to commit to one or both systems. 12 refs., 8 figs., 2 tabs

Blowdown heat transfer experiment, (1)

International Nuclear Information System (INIS)

Soda, Kunihisa; Yamamoto, Nobuo; Osaki, Hideki; Shiba, Masayoshi

1976-09-01

Blowdown heat transfer experiment has been carried out with a transparent test section to observe phenomena in coolant behavior during blowdown process. Experimental parameters are discharge position, initial system pressure, initial coolant temperature, power supply to heater rods and number of heater rods. At initial pressure 7-12 ata and initial power 6-50 kw per one heater rod, the flow condition in the test section is a major factor in determining time of DNB occurrence and physical process to DNB during blowdown. (auth.)

ECR heating in L-2M stellarator

International Nuclear Information System (INIS)

Grebenshchikov, S.E.; Batanov, G.M.; Fedyanin, O.I.

1995-01-01

The first results of ECH experiments in the L-2M stellarator are presented. The main goal of the experiments is to investigate the physics of ECH and plasma confinement at very high values of the volume heating power density. A current free plasma is produced and heated by extraordinary waves at the second harmonic of the electron cyclotron frequency. The experimental results are compared with the numerical simulations of plasma confinement and heating processes based on neoclassical theory using the full matrix of transport coefficients and with LHD-scaling. 4 refs., 2 figs

High-efficiency free-electron-laser experiments

International Nuclear Information System (INIS)

Boyer, K.; Brau, C.A.; Goldstein, J.C.; Hohla, K.L.; Newnam, B.E.; Stein, W.E.; Warren, R.W.; Winston, J.G.

1983-01-01

Experiments with a tapered-wiggler free-electron laser have demonstrated extraction of about 3% of the energy from the electron beam and measured the corresponding optical emission. These results are in excellent agreement with theory and represent an order-of-magnitude improvement over all previous results

Recent {sup 3}He radio frequency heating experiments on JET

Energy Technology Data Exchange (ETDEWEB)

Van Eester, D. [Association Euratom-Belgian State, LPP-ERM/KMS, TEC, Brussels (Belgium); Imbeaux, F.; Joffrin, E. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France)] [and others

2003-07-01

Various ITER relevant experiments using {sup 3}He in a majority D plasma were performed in the recent JET campaigns. Two types can be distinguished: dedicated studies of the various RF heating scenarios which rely on the presence of {sup 3}He, and physics studies using RF heating as a working tool to provide a tunable heat source. As the success of a number of these experiments depended on the capability to keep the {sup 3}He concentration fixed, real time control of the {sup 3}He concentration was developed and used. This paper presents a brief overview of the results obtained, zooms in on some of the more interesting recent findings and discusses some of the theoretical background. (authors)

Fabrication and performance evaluation of flexible heat pipes for potential thermal control of foldable electronics

International Nuclear Information System (INIS)

Yang, Chao; Chang, Chao; Song, Chengyi; Shang, Wen; Wu, Jianbo; Tao, Peng; Deng, Tao

2016-01-01

Highlights: • A flexible and high-performance heat pipe is fabricated. • Bending effect on thermal performance of flexible heat pipes is evaluated. • Theoretical analysis is carried out to reveal the change of thermal resistance with bending. • Thermal control of foldable electronics with flexible heat pipes is demonstrated. - Abstract: In this work, we report the fabrication and thermal performance evaluation of flexible heat pipes prepared by using a fluororubber tube as the connector in the adiabatic section and using strong base treated hydrophilic copper meshes as the wick structure. Deionized water was chosen as working fluid and three different filling ratios (10%, 20%, and 30%) of working fluid were loaded into the heat pipe to investigate its impact on thermal performance. The fabricated heat pipes can be easily bended from 0"o to 180"o in the horizontal operation mode and demonstrated consistently low thermal resistances after repeated bending. It was found that with optimized amount of working fluid, the thermal resistance of flexible heat pipes increased with larger bending angles. Theoretical analysis reveals that bending disturbs the normal vapor flow from evaporator to condenser in the heat pipe, thus leads to increased liquid–vapor interfacial thermal resistance in the evaporator section. The flexible heat pipes have been successfully applied for thermal control of foldable electronic devices showing superior uniform heat-transfer performance.

Heating in toroidal plasmas

International Nuclear Information System (INIS)

Knoepfel, H.; Mazzitelli, G.

1984-01-01

The article is a rather detailed report on the highlights in the area of the ''Heating in toroidal plasmas'', as derived from the presentations and discussions at the international symposium with the same name, held in Rome, March 1984. The symposium covered both the physics (experiments and theory) and technology of toroidal fusion plasma heating. Both large fusion devices (either already in operation or near completion) requiring auxiliary heating systems at the level of tens of megawatts, as well as physics of their heating processes and their induced side effects (as studied on smaller devices), received attention. Substantial progress was reported on the broad front of auxiliary plasma heating and Ohmic heating. The presentation of the main conclusions of the symposium is divided under the following topics: neutral-beam heating, Alfven wave heating, ion cyclotron heating, lower hybrid heating, RF current drive, electron cyclotron heating, Ohmic heating and special contributions

Experiments on the indirect heating of low density aerogels for applications in heavy ion stopping in plasma

International Nuclear Information System (INIS)

Rosmej, O.N.; Blazevic, A.; Suslov, N.; Kunin, A.; Pinegin, A.; Schaefer, D.; Nisius, Th.; Zhao, Y.; Rinecker, T.; Wiechula, J.

2010-01-01

Complete text of publication follows. The unique combination of a Petawatt High-Energy Laser System for Ion beam eXperiments - 'Phelix' (Nd:glass, 1053 nm, 300-500 J, 1-15 ns) and intense heavy ion beams of the UNILAC accelerator at GSI-Darmstadt allow creating and probing of hot plasma with a density of some percentage of solid-state density. The experimental program aims at the investigation of fundamental features of heavy ion stopping in ionized matter in view of promising applications for the Heavy Ion Fusion and astrophysics. For combined experiments on the interaction of heavy ion beams with ionized matter (GSI) a high density plasma target with homogeneous in time (∼ 5 ns) and space (∼ 1 mm) plasma parameters in required. For these purposes we are developing the combined target which consists on the Gold hohlraum (converter) and low Z foam target heated by the hohlraum radiation before probed by an ion bunch. Foam targets are rather promising due to the effective conversion of the deposited radiation energy into the internal plasma energy and slow hydrodynamic response on the heating. Direct irradiation of the Gold converter walls with a nanosecond pulse delivered by the PHELIX-laser system (GSI) leads to hohlraum radiation spectra in the photon energy range of 50-500 eV. Expected temperatures of the foam targets heated by this radiation amount to 20-30 eV at electron densities of 10 21 cm -3 . The results of the last hohlraum experiments carried out at PHELIX-laser energies of 200-250 J will be presented. In experiments the hohlraum radiation field, the conversion efficiency of the laser energy into soft X-rays, duration of the soft X-ray pulse, and parameters of the heated with X-rays foam targets have been measured. Acknowledgements. This work is supported by ISTC 2264 grant.

Nonlocal electron heat relaxation in a plasma shock at arbitrary ionization number

International Nuclear Information System (INIS)

Ramirez, J.; Sanmartin, J.R.; Fernandez-Feria, R.

1993-01-01

A recently obtained nonlocal expression for the electron heat flux valid for arbitrary ionization numbers Z is used to study the structure of a plane shock wave in a fully ionized plasma. Nonlocal effects are only important in the foot of the electronic preheating region, where the electron temperature gradient is the steepest. The results are quantified as a function of a characteristic Knudsen number of that region. This work also generalizes to arbitrary values of Z previous results on plasma shock wave structure

Studies of Electron Transport and Isochoric Heating and Their Applicability to Fast Ignition

International Nuclear Information System (INIS)

Key, M H; Amiranoff, F; Andersen, C; Batani, D; Baton, S D; Cowan, T; Fisch, N; Freeman, R; Gremillet, L; Hall, T; Hatchett, S; Hill, J; King, J; Kodama, R; Koch, J; Koenig, M; Lasinski, B; Langdon, B; MacKinnon, A; Martinolli, E; Norreys, P; Parks, P; Perrelli-Cippo, E; Rabec Le Gloahec, M; Rosenbluth, M; Rousseaux, C; Santon, J J; Scianitti, F; Snavely, R; Tabak, M; Tanaka, K; Town, R; Tsutumi, T; Stephens, R

2003-01-01

Experimental measurements of electron transport and isochoric heating in 100 J, 1 ps laser irradiation of solid A1 targets are presented. Modeling with a hybrid PIC code is compared with the data and good agreement is obtained using a heuristic model for the electron injection. The relevance for fast ignition is discussed

Microwave Tokamak Experiment: Overview and status

International Nuclear Information System (INIS)

1990-05-01

The Microwave Tokamak Experiment, now under construction at the Laboratory, will use microwave heating from a free-electron laser. The intense microwave pulses will be injected into the tokamak to realize several goals, including a demonstration of the effects of localized heat deposition within magnetically confined plasma, a better understanding of energy confinement in tokamaks, and use of the new free-electron laser technology for plasma heating. 3 figs., 3 tabs

Tunable electron heating induced giant magnetoresistance in the high mobility GaAs/AlGaAs 2D electron system.

Science.gov (United States)

Wang, Zhuo; Samaraweera, R L; Reichl, C; Wegscheider, W; Mani, R G

2016-12-07

Electron-heating induced by a tunable, supplementary dc-current (I dc ) helps to vary the observed magnetoresistance in the high mobility GaAs/AlGaAs 2D electron system. The magnetoresistance at B = 0.3 T is shown to progressively change from positive to negative with increasing I dc , yielding negative giant-magnetoresistance at the lowest temperature and highest I dc . A two-term Drude model successfully fits the data at all I dc and T. The results indicate that carrier heating modifies a conductivity correction σ 1 , which undergoes sign reversal from positive to negative with increasing I dc , and this is responsible for the observed crossover from positive- to negative- magnetoresistance, respectively, at the highest B.