Electron cyclotron heating in the WT-1 tokamak

Cho, T.; Kubo, S.; Ikeda, M.; Nakamura, Masahiko; Terumichi, Y.; Hamada, Y.; Tanaka, Shigetoshi

doi:10.1016/0375-9601(80)90019-5

Cited by 13 publications

(11 citation statements)

References 4 publications

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“…This is explained as follows: The maximum energy gain AW lmax due to ECH is limited by the detuning (out of phase) between the electron gyration and the wavefield, which is caused by the third term in Eq. ( 4); AW ±max is given by [13,37] AW lmax (eV) = elEl mwc 2/3 (8) Assuming E = 100 V-cnr 1 , AW lmax is estimated to be about 1 keV. The perpendicular heating of AW leads to an increase of 0:…”

Section: Production Mechanism Of Hot Electronsmentioning

confidence: 99%

“…Research related to electron cyclotron heating (ECH) has recently been intensified for several types of plasma confinement devices because of the development of a high power microwave source (gyrotron) [1][2][3][4][5][6][7][8]. Plasmas produced by injecting microwaves near the electron cyclotron resonance (ECR, a?…”

Section: Introductionmentioning

confidence: 99%

“…Plasmas produced by injecting microwaves near the electron cyclotron resonance (ECR, a? = fi e ) have been utilized in stellarators [6,7] and for preionization of discharges in tokamaks [8,9]. High energy (hot) electrons produced by ECH play an important role in maintaining MHD stability in bumpy tori [10] and as resonant particles for radiofrequency (RF) current startup without Ohmic heating [11][12][13] as well as for ECH current drive [14] in tokamaks.…”

Section: Introductionmentioning

confidence: 99%

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Observation of hot electrons produced by second harmonic electron cyclotron heating in the axisymmetric tandem mirror GAMMA 10

et al. 1987

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Microwave power, P ECH < 140 kW, has been injected at 28 GHz into the axisymmetric plug/barrier cell in the axisymmetrized tandem mirror GAMMA 10. As observed by soft X-ray measurements, the microwaves generate a hot (50-60 keV) electron population, radially peaked on the magnetic axis, which results in the formation of a thermal barrier. The production mechanism of these hot electrons is found to be second harmonic electron cyclotron heating (ECH), corrected for the effects of the relativistic mass variation and the Doppler shift. This mechanism also explains the first experimental observation of a saturation of the single-component hot electron temperature T eh as being caused by the finite width of the incident microwave lobe. The dependence of the plasma parameters on the filling gas pressure, the plasma density and the ECH power is studied. It is found that the heating process can be interpreted as a competition between electron acceleration by the incident wave, electron deceleration by collisions, and the mirror trapping efficiency of the source electrons for hot electrons. The axial profile of the soft X-rays is investigated in relation to the mechanism of the second harmonic ECH. The heating process is discussed in terms of the electron pitch angle and the magnetic field intensity.

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Section: Production Mechanism Of Hot Electronsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Observation of hot electrons produced by second harmonic electron cyclotron heating in the axisymmetric tandem mirror GAMMA 10

et al. 1987

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“…In this case, the electron transit time r r rotating from the upper half plane to the lower one in the poloidal section should be smaller than the collision time T U , i.e. T T <T V (14) r r can be expressed in terms of the safety factor q as (15) where T e is in eV, while T J ,= 5.9Xl(T 9 T e 3/2 (16) Substituting Eqs ( 15) and ( 16) into Eq. ( 14), we obtain the condition for instability suppression as q < T | / 3 5 0…”

Section: Suppression Of the Macroinstability By Lh-driven Currentmentioning

confidence: 99%

“…In stellarators [13] and in heliotrons [14], a currentless plasma is produced by an ECR discharge. In tokamaks, pre-ionization by ECH is effective for reduction of the breakdown voltage in the initial stage of the discharge, where the volt-seconds of the transformer are saved and the production of runaway electrons is suppressed in WT-1 [15] and ISX-B [16]. High-energy electrons in ECR plasma have played an important role in the toroidal plasma current startup and sustainment by ECH and the lower-hybrid current drive (LHCD) without Ohmic heating in WT-2 tokamak (RF tokamak), where high-energy electrons of about 1 keV in the ECR plasma interact resonantly with LHW and a plasma current I p is produced [17,18].…”

Section: Introductionmentioning

confidence: 99%

Toroidal plasma production by electron cyclotron heating in the WT-2 device

Cho¹,

Ogura²,

Andõ³

et al. 1986

Nucl. Fusion

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By injecting microwave power (120 kW, 35.6 GHz) into the WT-2 device, a toroidal plasma is produced by electron cyclotron heating near the upper-hybrid resonance. (1) The production mechanism is interpreted as the result of damping of electron Bernstein waves and described by a ray-tracing code. (2) The production mechanism of high-energy electrons in such a plasma is studied and interpreted as a competition between electron acceleration by the incident wave and deceleration by collisions. These electrons interact resonantly with the lower hybrid wave during the startup of an RF tokamak discharge. (3) The first experimental observation, in an ECR plasma, of the resulting macroinstability, consistent with a theory suggested by Peng et al., is reported. (4) This instability is suppressed by the lower-hybrid driven current, the required rotational transform being produced by this current.

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Propagation and Absorption of ECR Waves in a Low Temperature Toroidal Plasma of Small Size and Magnetic Field

Someșan

1985

Contrib Plasma Phys

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The propngntion nnd nbsorption of ECR wnves in n toknmnk plasma with sm;ill size and low values of the elertron temperature and the toroidal mngnetic field is studied numerically. The cold plasma dispersion equation is solved and my tracing calculations are prformcd to find thc nccessibility conditions nnd the optimal tingle of wnve launching for maximal ECR absorption.Absorption coefficients nre computed in the high density approximation. In troduc t,ionAs it has been shown by analizing the power balance of a tokamak type plasriia it is not possible to obtain t hernionuclenr ignition by mere ohniic heating. Therefore various scheiires have been developed in the last years in view of auxiliary heating of hot plasmns. Among them the methods based on launching of high power microwaves in the tokamak plasma showed to be very efficient. Progress in this field is related on one hand to the development of high power techniqurs of generation, transmission and launching of niicrowaves and on the other hand to a n extensive theoretical work elucidating the niechanimis of the energy transfer from the electromagnetic field to t,he plasma.Wave injection near the electron cyclot.ron resonance (ECR) frequency has been theoreticly stidied [ 1-81 and successfully applied to heat the plasiila in varioris toroiclal devices as TM-3, T-10, ISX-B, TFR, PLT, WT-1, ,JIPPT-11, JFT-2, Tosca etc. [9-191. The heating efficiences are of 5-7 eV/kW by using the extraordinarl\. oscillation nrode (with elliptical polarization perpendicrilar to the toroitlnl inagnct ic field) and of 2-4 eV/kW for the ordinary oscillation mode (with linenr polarization parnllcl t o the 1i1ag-nntic field). The ternperatlire growth is of 40--609/, (from 1,5 keV to 2,3 kc\-in T-10, 0,fi to 1 krV in JFT-2, 0,7 to 0,9 keV in Tosca, 0,8 to 1,3 keV in ISX-I3 etc.). The prtwnee of nn ECR wave in the plasma seems to be harmleas from the point of vien Wlierens in tokaniaks of sufficiently great tliniensions, a high teriiperntrire plasiirii itlap absorb conipletely the incident energy arid 1000/, cfficiencies of energy transfer are obtained without iiiajor difficulties, the heating rates have less encorrraging values for plasmas of modest sizes and temperatures; Good efficiencies niay be obtained in

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Electron cyclotron heating in the WT-1 tokamak

Cited by 13 publications

References 4 publications

Observation of hot electrons produced by second harmonic electron cyclotron heating in the axisymmetric tandem mirror GAMMA 10

Observation of hot electrons produced by second harmonic electron cyclotron heating in the axisymmetric tandem mirror GAMMA 10

Toroidal plasma production by electron cyclotron heating in the WT-2 device

Propagation and Absorption of ECR Waves in a Low Temperature Toroidal Plasma of Small Size and Magnetic Field

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