RECENT ADVANCED TECHNOLOGY IN ELECTRON-CYCLOTRON HEATING-SYSTEMS

被引:42
作者
THUMM, M
KASPAREK, W
机构
[1] UNIV KARLSRUHE,INST HOCHFREQUENZTECH & ELEKTR,KARLSRUHE,GERMANY
[2] UNIV STUTTGART,INST PLASMAFORSCH,D-70569 STUTTGART,GERMANY
关键词
D O I
10.1016/0920-3796(94)00196-E
中图分类号
TL [原子能技术]; O571 [原子核物理学];
学科分类号
0827 ; 082701 ;
摘要
Electron cyclotron resonance heating and electron cyclotron current drive are of growing importance among the heating and current drive methods for fusion plasmas. To obtain full advantage of the two main features of these techniques, namely the absence of antenna structures near the plasma boundary and the possibility of localized power deposition, the launching of a well-collimated beam with a controlled direction and polarization is necessary. This requires the generation and transmission of high power millimetre waves with high mode purity. Step-tunable single-mode gyrotron oscillators capable of high average power (1 MW unit(-1)) continuous operation in the millimetre wave range (100 GHz-180 GHz) are currently under development. 140 GHz gyrotrons with 0.58 MW output power in the gaussian free space TEM(00) mode with pulse length tau up to 2.0 s and efficiency eta = 34% are commercially available. The corresponding parameters of a 159 GHz gyrotron are P-out = 0.5 MW, tau = 0.7 s and eta = 30%. High order rotating TE modes (e.g. TE(22,6) at 140 GHz) are used as working modes in the cavities of the tubes. Improved internal quasi-optical mode transducers generate the TEM(00) output mode with efficiencies of 90%-95% and separate the electron beam from the r.f. beam, thus allowing large continuous wave relevant collectors compatible with designs providing potential depression. Face-cooled double-disc sapphire windows, cryogenically edge-cooled single-disc sapphire windows (liquid N-2, liquid Ne or liquid He cooling), distributed windows (metal-ceramics) and single-disc diamond windows are under investigation in order to solve the window problem. Long-distance high power millimetre wave transmission from the source to the plasma device with very low ohmic losses and high mode purity can be accomplished by (1) open, quasi-optical TEM(00) transmission through a gaussian beam waveguide using focusing reflectors as phase correcting elements, and (2) closed, highly overmoded, circumferentially corrugated or dielectrically lined, tubular HE(11) mode waveguide. In this paper we report the state of the art in the development of high power millimetre wave sources and windows and discuss the components and the characteristics of TEM(00) and HE(11) transmission systems and antennas.
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页码:291 / 317
页数:27
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