F. Shimpo

G. Nomura

R. Kumazawa

R. Sakamoto

T. "Mutoh

T. Ido

T. Seki

T." Watari

National Institute for Fusion Science (NIFS-Repository)

§ 15. Development of Steady State Operation of ICRF Fast Wave Loop Antenna for the LHD Mutoh,T., Kumazawa,R., Seki,T., Sakamoto,R. Nomura,G. , Shimpo,F., Ido,T., Watari,T. The fast-wave loop antenna for LHD is planned to be used as the steady state heating tools. The oovelopment program was started in 19931). In the test stand, high voltage and long pulse operation had been tested by using the realistic R&D antenna. Due to the low loss and high VSWR circuit, the high voltage and high current test was carried out by the relatively low RF power of lower than 100 kW. The results of the test set operations is shown in Fig.1. The vertical axes indicate the maximum RF voltage and current on the vacuum coaxial line. The figure shows two series of test using two kinds of ceramic fee<hhrough. In both cases, we successfully achieved high voltageicurrent tests at around 40kV/800A. These operations were limited by the outgas inside the vacuum chamber which finally caused the RF discharge and sucti!n impedance mismatching. In the case of LHD heating experiment, several ohms coupling resistance is expected and impedance matching must be more easy. These steady state operation test confirms the reliability of the present system design. 0: 0 6 0 r--T""T"T'M'T'm"'-...,.-nM'TTTTy-""""'T"".,..,.,M'TTI-r-.,..-,."TT'1'TTTI 1 2 0 0 > ~ ~ ~ 1000 ~ (/) 50 .~ E ~ 40 (l) 0 g 30 (l) ~20 0 > u.. 10 a: E 0 1~~~~~~~W-~~ww~~~.w ~ ru 800 0 c .., o; 3. 600 ~ 400 ~ 0 ~ 200 Fig.1 Long pulse test records of the R&D antenna are plotted. Two kinds of ceramic feedthrough were used in the ·tests. The design work of the LHD steady state antenna images about 500 kW operation for 30 minutes per single loop. At this operation level, RF dissipation loss can be removed by the circulating water. The severest heat load is the charged particle influx to t.l-te carbon protectors along the magnetic field lines on the both antenna sires. On the assumed plasma heat load distribution, the temperature increments of the carbon plates are calculated by using the finite element calculation codeANSYS . It consiOOred the radiation power, the particle flux along the magnetic field and the RF dissipation l0ss of the induction current. Figure 2 shows the temperatum distribution of the carbon protector and cooling water channel. The temperatures of the top edge and lower edge of the pr Jtector are shown in Fig.3 by changing the antenna position winch can be controlled by the swing motion. The calculation condition corresponds to the 3MW CW input power to the plclSma The top edge temperature can be suppressed below 500°C by increasing the distance between plasma and top edge of the protector of over 3 em. It is still reasonable distance to get the substantial plasma coupling resistance. =~=~::~:::~ OG~C.CDet--r--\OtO • . .. .. .. .. .. .. . .. .. .. ~~=:::.::::~~: "'"-- · "'~~~"""'·· 1111111111 ... ... .. o ......... o • •IAO\Ori ..... ft. O.Ori..,.NC'I.,._..., ............ ririri..-000 Fig.2 Temperature profile calculation of the carbon 6 -2..-0 protector of loop antenna by ANSYS code. 2ooo~~~~~~~~~~~~~~aoo I (l) ~ 1500 ~ 600 11 c X 0 a: _g 1 OOOt--...... _,. .... \ ............... ..l. ..................... .L .. .. ............ .... ].. 0 (ij" 400 s: 0" ~ () 0 ci.. E Q) 1-l j . of i Lower Edg~ 0 5 10 15 s. 5' ~ 200~ ()' ~ Position/Distance from Plasma Eclge (em) Fig.3 Calculated temperature increments of the carbon side protector by ANSYS code are shown by changing the top edge position of the antenna. Reference 1) T. Mutoh, et.al. , Journal of Plasma and Fusion Research. SERIES, Vol. I, (1998) 334 101 

Development of Steady State Operation of ICRF Fast Wave Loop Antenna for the LHD

Development of Steady State Operation of ICRF Fast Wave Loop Antenna for the LHD

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