Influence of the electron velocity spread and the beam width on the efficiency and mode competition in the high-power pulsed gyrotron for 300 GHz band collective Thomson scattering diagnostics in the large helical device

2016 ◽  
Vol 23 (9) ◽  
pp. 093109 ◽  
Author(s):  
O. Dumbrajs ◽  
T. Saito ◽  
Y. Tatematsu ◽  
Y. Yamaguchi
Keyword(s):  
High Power ◽  
Beam Width ◽  
Thomson Scattering ◽  
Electron Velocity ◽  
Mode Competition ◽  
Velocity Spread ◽  
Collective Thomson Scattering

scholarly journals Developments for collective Thomson scattering equipment with a sub-THz gyrotron in LHD

2019 ◽  
Vol 203 ◽  
pp. 03012
Author(s):  
Teruo Saito ◽  
Yoshinori Tatematsu ◽  
Yuusuke Yamaguchi ◽  
Masafumi Fukunari ◽  
Takumi Hirobe ◽  
...  
Keyword(s):  
Thomson Scattering ◽  
Pulse Mode ◽  
Loss Coefficient ◽  
Mode Competition ◽  
Low Loss ◽  
Plasma Parameters ◽  
Corrugated Waveguides ◽  
Collective Thomson Scattering ◽  
77 Ghz ◽  
Transmission Test

Plan of collective Thomson scattering (CTS) experiment for the Large Helical Device (LHD) in NIFS with a 303 GHz gyrotron is under way. Use of a sub-THz gyrotron expands the CTS-applicable region of plasma parameters. In LHD, sub-THz CTS can be applied to the high density operation region, plasmas with impurity hole, etc. Moreover, sub-THz CTS is expected to be free from ECE noise. Its “collective” use with 77 GHz and 154 GHz CTS will compose a powerful diagnostic system. A high power sub-THz gyrotron with a frequency of 303 GHz has been developed. Its maximum power is 320 kW. It oscillates in pulse mode and the maximum pulse width is around 100 μs, which is sufficient for use in CTS experiments. A whispering gallery mode TE22,2 was adopted for this gyrotron to avoid mode competition. Careful frequency measurement has proved purely single mode oscillation of the TE22,2 mode including turn-on and turn-off phases of the oscillation pulse. This is consistent with mode competition calculations taking account of a finite voltage rise time. A low loss transmission line is necessary for CTS. We have two possibilities. One is a new line with 1.25 inch corrugated waveguides that are optimized for the 300 GHz band. Transmission test with the 303 GHz gyrotron has been carried out and a sufficiently low loss coefficient has been confirmed. The other is to use an existing line with 3.5 inch corrugated waveguides for lower frequencies such as 77 GHz and 154 GHz. Transmission test has been carried out with the 303 GHz gyrotron and a sufficiently low loss coefficient has been confirmed also for 3.5 inch corrugated waveguides. An existing line with 3.5 inch corrugated waveguides will be used in the initial phase of 303 GHz CTS experiment.

Scattering volume in the collective Thomson scattering measurement using high power gyrotron in the LHD

2016 ◽  
Vol 11 (06) ◽  
pp. C06005-C06005 ◽  
Author(s):  
S. Kubo ◽  
M. Nishiura ◽  
K. Tanaka ◽  
D. Moseev ◽  
S. Ogasawara ◽  
...  
Keyword(s):  
High Power ◽  
Thomson Scattering ◽  
Collective Thomson Scattering ◽  
Scattering Volume ◽  
Scattering Measurement

Collective Thomson scattering of 77 GHz high power ECRH beam in LHD

2009 ◽  
Author(s):  
S. Kubo ◽  
M. Nishiura ◽  
K. Tanaka ◽  
T. Shimozuma ◽  
Y. Yoshimura ◽  
...  
Keyword(s):  
High Power ◽  
Thomson Scattering ◽  
Collective Thomson Scattering ◽  
77 Ghz

High-power pulsed gyrotron for 300 GHz-band collective Thomson scattering diagnostics in the Large Helical Device

2014 ◽  
Vol 55 (1) ◽  
pp. 013002 ◽  
Author(s):  
Yuusuke Yamaguchi ◽  
Teruo Saito ◽  
Yoshinori Tatematsu ◽  
Shinji Ikeuchi ◽  
Vladimir N. Manuilov ◽  
...  
Keyword(s):  
High Power ◽  
Thomson Scattering ◽  
Collective Thomson Scattering

scholarly journals Computer Simulation for Evaluating Ion Temperature by Means of Collective Thomson Scattering Using a High Power, Multi-Mode D2O Laser.

1992 ◽  
Vol 68 (3) ◽  
pp. 279-297
Author(s):  
Masaaki Nagatsu ◽  
Yuichi Tsubouchi ◽  
Noriharu Takada ◽  
Koichi Sasaki ◽  
Takashige Tsukishima
Keyword(s):  
Computer Simulation ◽  
High Power ◽  
Thomson Scattering ◽  
Ion Temperature ◽  
Collective Thomson Scattering ◽  
Multi Mode
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