C. Suzuki

G. Matsunaga

K. Toi

M. Takeuchi

R. Ikeda

National Institute for Fusion Science (NIFS-Repository)

+:••..... ,.-.. . ..1°f·06 0.2 0.4 0:6 0:8 1 1.2P,0[. _ .Fig. 2 Radial profiles ofTe,lle and Vs at lOOms, 150ms,and 200ms.60[.....40l301·;;.. 20l20.,..., 15llol';;(-;" slO.. f' ···..,.·······,_···_··1········,,·····10.4 !.!::I: 0.2f0.1 .. ,at ; j.100 _..__Fig. 1 Time evolution ofTe ,lle , H Q and the ratio ofincident and reflected ECWpower in Rax=92.1cm,Bt=612G, the probe positionPLp =0.7, PEcR=8.7kW, andgas filling pressurePH2= 3.6x10-sTorr.Fig. 3 The generation regime of the plasma obtained byBcscan.[1] K. Toi et aI., 29th EPS on Plasma Physics and ControlledFusion, Montreau, 2001, paper No. P4-061.....:.;:.. 10 . .:' j:ii· .! I .lJ! , .The radial profiles of Te, lle and space potential (Vs)are shown in Fig. 2 at three timings. Note that both Te andne profiles tend to become peaky toward the end of thedischarge. The above-mentioned dimensionless parametersat t=200ms are as follows: {31 =0.02%, P; =0.05 andv' =0.05, where the last two parameters are evaluated atP=0.7. The achieved range of Te and n;1I11t1 for hydrogenplasma is shown in Fig. 3, where Te is evaluated at p =0.7.These data were taken by the Bcscan from 612G to 1050G.This graph shows that the plasmas in this experiment areexpected to go into the plateau to 1/ v - helical rippletransport regime.vEnergy and particle transport in high temperatureplasma is very complicated and the basic understanding isstill insufficient. One reason is caused by difficulty ofmeasurements of turbulent fluctuations in such plasma.Transport in high temperature plasma may be simulated withlow temperature plasma if these plasmas have similarfollowing dimensionless parameters[l]. That is, they areelectron-ion collision frequency normalized by transitfrequency, normalized ion gyro-radius evaluated withelectron temperature (Te), and the toroidal beta valueevaluated with electron pressure:Ikeda, R. (Dep. Energy Eng. Sci., Nagoya Univ.),Takeuchi, M. (Dep. Energy Eng. Sci., Nagoya Univ.),Matsunaga, G., Suzuki, C., Toi, K.§ 20. Plasma Production with 2.45GHzElectron Cyclotron Waves• PsPs = (a) ,andI B12 //2 Itowhere Bb lle, q, R, <a>, V ei ' Ville' Ito' and <Pe> arerespectively the toroidal field, electron density, safety factor,major radius, averaged minor radius, electron-ion collisionfrequency, electron thermal velocity, vacuum magneticpermeability, and averaged electron pressure. In CHS, thesimulation experiment is proceeded using a plasma producedby 2.45 GHz electron cyclotron wave (ECW) and 9MHzwhistler waves at low toroidal field Bt<O.lT. A key issueof this project is to demonstrate that low collisionalityplasmas are routinely produced having high ionizationdegree. In the experiment, radial profiles of Te, lle and soon were measured with the triple-Langmuir probe (LP). Inorder to calibrate the LP data, the line average electrondensity (n;lIJlIJ) was measured with 2mm microwaveinterferometer with high precision phase counter.ECW was injected into filled hydrogen gas for180ms in the magnetic configuration ofRax=92.1cm, whereBt (R=Rax):::::: 612G. A typical time evolution is shown inFig. 1. In this shot, Te rises continuously during the ECW.pulse and reaches about 18eV at the radial location ofP=0.7. On the other hand, electron densitY(lle) at P=0.7stays almost constant after lOOms. In the latter half of thedischarge, Te and lle fluctuations are considerably enhanced.280

Plasma Production with 2.45GHz Electron Cyclotron Waves

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)