Suppression of spurious mode oscillation in mega-watt 77-GHz gyrotron as a high quality probe beam source for the collective Thomson scattering in LHD

2012 ◽  
Vol 83 (10) ◽  
pp. 10D731 ◽  
Author(s):  
S. Ogasawara ◽  
S. Kubo ◽  
M. Nishiura ◽  
Y. Tatematsu ◽  
T. Saito ◽  
...  
Keyword(s):  
Probe Beam ◽  
Thomson Scattering ◽  
High Quality ◽  
Beam Source ◽  
Spurious Mode ◽  
Mode Oscillation ◽  
Collective Thomson Scattering ◽  
77 Ghz

scholarly journals Design and development of the ITER CTS diagnostic

2019 ◽  
Vol 203 ◽  
pp. 03002 ◽  
Author(s):  
Søren B. Korsholm ◽  
Bruno Gonçalves ◽  
Heidi E. Gutierrez ◽  
Elsa Henriques ◽  
Virginia Infante ◽  
...  
Keyword(s):  
Probe Beam ◽  
Electron Cyclotron Resonance ◽  
Thomson Scattering ◽  
Alpha Particles ◽  
60 Ghz ◽  
Plasma Edge ◽  
Minor Radius ◽  
Front End ◽  
The Status ◽  
Collective Thomson Scattering

The Collective Thomson Scattering (CTS) diagnostic will be a primary diagnostic for measuring the dynamics of the confined fusion born alpha particles in ITER and will be the only diagnostic for alphas below 1.7 MeV [1]. The probe beam of the CTS diagnostic comes from a 60 GHz 1 MW gyrotron operated in a ~100 Hz modulation sequence. In the plasma, the probing beam will be scattered off fluctuations primarily due to the dynamics of the ions. Seven fixed receiver mirrors will pick up scattered radiation (the CTS signal) from seven measurement volumes along the probe beam covering the cross section of the plasma. The diagnostic is planned to provide a temporal resolution of ~100 ms and a spatial resolution of ~a/4 in the core and ~a/20 near the plasma edge where a = 2.0 m is the nominal minor radius of ITER. The front-end quasi-optics will be installed in an equatorial port plug (EPP#12). A particular challenge will be to pass the probing beam through the fundamental electron cyclotron resonance, which is located in the port plug (R=10.3 m) for the nominal magnetic field Bt = 5.3 T. Hence, particular mitigation actions against arcing have to be applied. The status of the design and specific challenges will be discussed.

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.

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

Design of collective Thomson scattering system using 77 GHz gyrotron for bulk and tail ion diagnostics in the large helical device

2008 ◽  
Vol 79 (10) ◽  
pp. 10E731 ◽  
Author(s):  
M. Nishiura ◽  
K. Tanaka ◽  
S. Kubo ◽  
T. Saito ◽  
Y. Tatematsu ◽  
...  
Keyword(s):  
Thomson Scattering ◽  
Scattering System ◽  
Collective Thomson Scattering ◽  
77 Ghz

Collective Thomson Scattering of 77 GHz High-Power ECRH Beam in LHD

2010 ◽  
Vol 50 (6-7) ◽  
pp. 624-628 ◽  
Author(s):  
S. Kubo ◽  
M. Nishiura ◽  
K. Tanaka ◽  
N. Tamura ◽  
T. Shimozuma ◽  
...  
Keyword(s):  
High Power ◽  
Thomson Scattering ◽  
Collective Thomson Scattering ◽  
77 Ghz

scholarly journals Optimization of Megawatt 77-GHz Gyrotron Operation for Collective Thomson Scattering in LHD

2013 ◽  
Vol 8 (0) ◽  
pp. 2402069-2402069
Author(s):  
Shinya OGASAWARA ◽  
Shin KUBO ◽  
Masaki NISHIURA ◽  
Yoshinori TATEMATSU ◽  
Teruo SAITO ◽  
...  
Keyword(s):  
Thomson Scattering ◽  
Collective Thomson Scattering ◽  
77 Ghz

scholarly journals Identification of Spurious Modes of High-Power 77-GHz Gyrotron for Collective Thomson Scattering in LHD

2012 ◽  
Vol 7 (0) ◽  
pp. 2405061-2405061 ◽  
Author(s):  
Shinya OGASAWARA ◽  
Shin KUBO ◽  
Masaki NISHIURA ◽  
Yoshinori TATEMATSU ◽  
Teruo SAITO ◽  
...  
Keyword(s):  
High Power ◽  
Thomson Scattering ◽  
Collective Thomson Scattering ◽  
Spurious Modes ◽  
77 Ghz
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