First Measurement of Electron Temperature and Density Profiles for Spherical Tokamak Plasmas Sustained by Lower Hybrid Waves

Togashi, H.; Ejiri, A.; Homma, H.; Shinya, Takahiro; Takase, Y.; Toida, K.; Tsujii, N.; Yamaguchi, Takashi; Yoshida, Yusuke; Hasegawa, Makoto; Nagashima, Yoshihiko; Furui, H.; Nakamura, Kenta; Takahashi, Wataru; Takeuchi, Takamasa; Sonehara, Makoto; Yajima, S.; Yamazaki, H.

doi:10.1585/pfr.10.1202082

Cited by 12 publications

(12 citation statements)

References 11 publications

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“…In the figure, only 8 points are plotted, because the TS signal intensities for the other 2 points (R = 481 and 526 mm) seemed to be not sufficient due to strong stray light, small LΩ, and the low-density. The shape of each profile is similar to that obtained in the previous experiment, where I p was about 5 kA and the LHW power was about 15 kW [4], although n e and p e in the present experiment are more than two times higher than those in the previous experiment due to the higher LHW input power.…”

Section: Thomson Scattering Measurement For Lhw-driven Plasmassupporting

confidence: 85%

Thomson scattering measurements in low-density plasmas in the TST-2 spherical tokamak

et al. 2015

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Section: Thomson Scattering Measurement For Lhw-driven Plasmassupporting

confidence: 85%

Thomson scattering measurements in low-density plasmas in the TST-2 spherical tokamak

et al. 2015

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“…In addition, it is not disappeared when the voltage sources for the APDs and the amplifier were replaced by stable DC power supplies, suspecting the voltage drop of the batteries. According to Togashi [5], the change of the bias voltage to hold an initial gain of the APD increases proportional to the temperature with the slope of ∼ 2.5 V/ • C. The ambient temperature of the laboratory is controlled as 19 • C by the air conditioner during the experiment. It seems to take some time for the APD temperature to reach an equilibrium, since the APDs are cased in double-layered aluminium boxes to shield them from…”

Section: Jinst 12 C12013mentioning

confidence: 99%

Calibration of Thomson scattering system on VEST

et al. 2017

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The Thomson scattering system has been recently installed on Versatile Experiment Spherical Torus (VEST) to measure the electron temperature and the density of the core plasmas. Since the calibration of the system is required for the accurate measurement of these parameters, a polychromator and the system efficiency are calibrated. The bias voltage of the detector is optimized and the relative responsivity of the polychromator is measured to analyse the spectral broadening. The tendency of decreasing responsivity because of the ambient temperature change is addressed together. The efficiencies of the alignments using HeNe laser and Nd:YAG laser are compared. After the alignment using Rayleigh scattering, it is improved ∼ 7 times while the peak signal of the stray light is decreased. To evaluate the efficiencies of the alignment using HeNe laser, it is compared with the efficiency of the fine alignment by Rayleigh scattering. After absolute calibration is done, the Thomson scattering signal is estimated theoretically. The Bayesian analysis is tried using the synthetic data, and the results show that the input temperature and the density are inside the contour of the 90% confident level. The calibrated Thomson scattering system will provide the meaningful information of the core plasma of the VEST.

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“…On TS systems on other devices, ray tracing calculations with an assumption on the beam divergence are often used to design the apertures [3][4][5]. In our case, the density of RF driven TST-2 plasma is much lower than typical densities on other tokamaks [6,7]. Therefore, it is necessary to reduce the stray light as much as possible by improving the aperture configuration.…”

Section: Introductionmentioning

confidence: 99%

Improvement of Aperture Configuration to Reduce the Stray Light for Thomson Scattering Measurement Using a Peripheral Beam Profile Monitor

Kawamata

Ejiri

Matsuzaki

et al. 2019

Plasma and Fusion Research

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The stray light is a major problem in Thomson scattering (TS) measurements. The main cause of stray light is unnecessary divergence of the incident laser beam and an aperture is a standard component to reduce it. In order to improve the aperture configuration (including size, number and position in the laser injection tube), a peripheral beam profile monitor, consisting of a screen with a through hole for the laser beam and a CMOS camera, was developed. Instead of the actual laser injection tube a mock-up tube was used to measure the peripheral beam profiles under various aperture configurations. The configuration with four 15 mm diameter apertures was chosen and installed on the TS system for the TST-2 spherical tokamak. The stray light was reduced to about 4% compared to the smaller diameter injection tube with no apertures. As a result, it became possible to make TS measurements in the electron density range above 1.0 × 10 17 m −3 .

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First Measurement of Electron Temperature and Density Profiles for Spherical Tokamak Plasmas Sustained by Lower Hybrid Waves

Cited by 12 publications

References 11 publications

Thomson scattering measurements in low-density plasmas in the TST-2 spherical tokamak

Thomson scattering measurements in low-density plasmas in the TST-2 spherical tokamak

Calibration of Thomson scattering system on VEST

Improvement of Aperture Configuration to Reduce the Stray Light for Thomson Scattering Measurement Using a Peripheral Beam Profile Monitor

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