K. "Ohno

M. Matsuoka

M." Kawaguchi

"Ohno,  K.

Matsuoka,  M.

Kawaguchi,  M."

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§23. Development of Capacitively-Coupled RF lon Source Ohno, K, Matsuoka, M, KaWclglrlll, M, (IXtX IOOus. & Tech Edu Mie Univ.) Plasna in NBI ion~ has Inn rro.itred by a <k arc &dmge up to rre;em. sm rot ~ filaments required for an arc disimge have a short life time, it is difficult to tre tJ:e conventional arc discharge in future NBI systems, \\hich will re installed in a rndiooctive enviromnent To solve this publem, ~eral ~\\ere }Xffonned to pOOoce tJ:e source plasma inch.dively by rf JXl~. Here, \\e exp.Timentally testOO th! awlicability of a capritively-couJied plasma to future NBI systems. We exru.nined ~ kirxis of JXmlllel-plate el~ with diffi:rent si2e (20nnn X 30inn\ 40mm X rotnm, 60tmn X ~)and diffennt springs (20,40,60mm) to get a unifonn plasma We attached a 1rnnspna1t witmw irntead of an extraction grid am dmved visible lights from tJ:e plasma with CCD camem. ~ sourre plasma chunb:l" taxi in th! p-erent exp:Iimem WclS of magretic-multiplle ~ a00 had lxen taxi in th! NBI fe)t starKi in IPP Nagoya CW rf JX)\\ef up to 100 W with 13.56 MHz in freqtrocy ~ fed via a matching box We taxi t\\0 of tre many feed.ti1rougrn, \\hich had reen taxi for filaments, for the rf Sl.Wly. No filaments \\ere attached in this~~ filling~ was argoo. with~ fum 2.66 Pa to 133 Pa Figure 1 sm\\S the J11.<N unifoon plasma obtained in the exp;::riment. ~ exrefimental conditions~ filling~ 13.3 Pa rf!Xl~ 80W electrode size 60 mm X ~nun electrode distance 40 rrnn wren th! filling ~ was high, tre disimge WclS quite localized at the taxi feai-throughs, ~and wires~ trem With a~ in tJ:e ~' tJ:e disimge grndually bxame diffusive. The most unifonn plasma WclS obtained at ~of 13.3 Pa for all configuratiorn ofth! antenm The rf disimge in Fig 1 can re divickrlinto ~~a bright area surrourxting ~with thi~ of about 1 em, a bright area at th! ~ a bright area rear some pu1s of the wires bet\\ecrlthe pates and the~ and a diffusive plasma. exterrl:rl through th! \\hole chunb:l". The bright area near the right-buxl plate in the figure WclS yellowish, which may indicate tJ:e exis1eoce of spJttcrimg from the~ plate. wren \\e dxreased tre filling ~ to 0.266 Pa, and irx.Teased the rf JX)\\ef, \\e dmved localized arcing on the mill one after anc:Jtln. Figure 2 sho\\S the time tmce of the flooting JUentia1 ~ by one of the untaxi feed-\\hn arcing occurred and stillenly dxreased at each arcing In oooclusion, \\e dmved the extent of uniformity of the ~-coutied plasmas from visible light and sho\\00 1hat l.mifotm plasmas can re obtained with a low filling ~re. Wrth simp.e JXmlllel-plate antenm, ho~, the flootingJUential of the plasma is fru:rl tore significantly high, \\hich ~ freqw1t rurings. We plan to modi1)rthe anterma to avoild this publem, as \\ell as to~ the lnJU JXMef. 250 ~ 200 -"' ·.;:; 150 c:: ID .... &. 100 1:10 c:: .... 50 "' 0 u: 0 Fig 1. 1:re moot unifoon plasma h1r~ ____......-h~ r ~ ----------I ·II' ·- ,··-T i I ~ ~ I i I 0 0.2 0. 4 0.6 0.8 Time [s] Fig 2. ~time trnce of the f1ooting JUentia1 Refureoce 1 )M Monte, M Matsuoka, and M KaWclglrlll, Proc. of the 7th Jntem Symp. on the Scienx & Teclmology of light Soui1Ces, w.85-86, Kyoto, 1995. 127 

Development of Capacitively-Coupled RF Ion Source

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