C. Suzuki

G. Matsunaga

T. Shoji

T. Toi

Y. Sakawa

National Institute for Fusion Science (NIFS-Repository)

§ 23. Microwave Heating of Whistler WavePlasmas in CHS2)Nishimura, K., Shoji, T., et al., Fusion Tech.17(1990)8615050 100PRF [kW]5 10 15 20 25 30 35t[ms]P[2.45G]= 18kW, P =2x1 O\orr, Bt=613GHe000 0 0: ;0 _ •. : ; ..1 1-..I 0 I··..·..········..·..····r··..·······..·····.."··········..···· ..OL.l.........L..L.&...I-........L.&..L..L.&...I-&...I-.......L...L.L..L.&...I-.......L.L.Ia150Fig. 2 rf power dependence of averaged densitywith and without ECH power.Fig. 1 Time evolution of line averaged density,plasma edge density and electron temperature withand without ECH power for He plasma. f=9MHz..AcGl50V....................o 100oF"C140,.....,15'CCDc· 80,....., 60.....EIQ400........It..20iPlasma production by whistler wavesThe rf power of 500kW, pulse duration of 10msec and thefrequency of 9MHz is used in this experiment. Nagoya typeIII antenna is used The plasma rensity, electron temperatureare measured by the 2mm microwave interferometer andLangmuire probe. For the electron heating of whistler waveplasma, the microwave power of 2.450Hz and 20kW isused. The time evolution of the line averaged rensity, <ne>,the edge rensity ne(edge) and electron temperature Te(edge) atoutmost magnetic surface and with rf and microwave powersfor helium discharge is shown in Fig.I. The toroidalmagnetic field strength Bt is 6130. The plasma with peakedcensity profile is produced initially by the rf power of105kW. At the last 4msec of the rf pulse, microwave powerof 18kW is applied on the plasma. Adtitional microwavepower which is 17% of rf power causes the increase inaverage censity of 20%, while ne(edge) increases three timesas much as the rf plasma. After rf pulse is shut off, themicrowave discharge can sustain the plasma but ne(edge)jumps up to show more wirer plasma profile than thar ofthe rf plasma. It is also shown that the plasma rensity isdifficult to start up when the microwave power is appliedonly. The initial plasma production by the rf can start upthe microwave discharge easily. The cepenrence of rf andmicrowave powers on <ne> are shown in Fig.2 It is shownthat the increase in <ne> with the microwave heating isobserved above the cut-off density for 2.450Hz microwave.Shoji, T., Sakawa, Y. (Dept. Energy Eng. and Sci.,Nagoya Univ.)Suzuki, C., Matsunaga, G., Toi, T.IntroductionFor the purpose of discharge cleaning and high beta relatedstudies in a low magnetic field strengths of kO range, theplasma production using whistler waves in radio frequency(rt) range [1-2] is useful because high power rf sources arecheaper than microwave ones and plasma production in awide range of magnetic field strength is available for fixedfrequency. The microwave power of 2.450Hz is applied tothe whistler wave plasmas to study the effect of additionalelectron heating on the plasma production.ReferenceI)Shoji, T., Nishimura, K, et al., Nagoya Univ.Ann.Report 6(1989)1283

Microwave Heating of Whistler Wave Plasmas in CHS

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