Discharge at the pillbox window for an LHRF launcher

Author

Ikeda, Yoshitaka ; Imai, Tsuyoshi ; Sakamoto, Keishi

Author_Institution

Naka Fusion Res. Establ., JAERI, Ibaraki, Japan

Volume

17

Issue

3

fYear

1989

fDate

6/1/1989 12:00:00 AM

Firstpage

534

Lastpage

540

Abstract

The discharge at a pillowbox-type waveguide vacuum window for a lower hybrid resonant frequency (LHRF) launcher at 2 GHz is studied experimentally. A discharge is observed near the window at a pressure below 10^-2 Pa. The discharge has little or no effect on the RF-transmission waveform; however, the temperature rise of the ceramic due to the discharge reaches about 100 times higher than that in the no-discharge case. Moreover, the breakdown of gas in the waveguide is enhanced by the discharge. The discharge can be suppressed by sufficient RF conditioning and/or by coating the window with materials having a low secondary electron emission ratio such as carbon or TiN. These results are accurately explained by the theory of single-surface multipactoring discharge induced by an electric field perpendicular to the ceramic and the space charge

Keywords

discharges (electric); electromagnetic launchers; waveguides; 2 GHz; C; LHRF launcher; RF conditioning; RF-transmission waveform; TiN; breakdown; ceramic; discharge; electric field; gas; low secondary electron emission ratio; lower hybrid resonant frequency launcher; no-discharge case; pillbox window; pillowbox-type waveguide vacuum window; pressure; single-surface multipactoring discharge; space charge; temperature rise; waveguide; Carbon dioxide; Ceramics; Coatings; Electric breakdown; Electron emission; Organic materials; Radio frequency; Resonant frequency; Temperature; Tin;

fLanguage

English

Journal_Title

Plasma Science, IEEE Transactions on

Publisher

ieee

ISSN

0093-3813

Type

jour

DOI

10.1109/27.32267

Filename

32267