Measurement of the Local Current Density Inside a Current Sheet Using a Rogowski Coil Array on UTST Merging Plasmas

Yamazaki, H.; Furui, H.; Yamasaki, K.; Ushiki, Tomohiko; Ejiri, A.; Inomoto, Michiaki; Takase, Y.; Ono, Yasushi; Tsujii, N.

doi:10.1585/pfr.13.1202093

Cited by 4 publications

(1 citation statement)

References 10 publications

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“…Surprisingly, the hot spot size was not much different in START and MAST. Direct measurements of the properties of the current sheet have been recently performed on UTST using in-vessel pick-up coil arrays [35] showing thickness of the current sheet in UTST of 3-4 cm for R direction, and 2 cm for Z direction, which again is not far from that observed on START and MAST, and a maximum current density value ~2.5 MA m −2 .…”

Section: Stage 2: Merging Of Two Rings Reconnection and Formation Of ...mentioning

confidence: 89%

Merging-compression formation of high temperature tokamak plasma

Gryaznevich

Sykes

2017

Nucl. Fusion

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Merging-compression is a solenoid-free plasma formation method used in spherical tokamaks (STs). Two plasma rings are formed and merged via magnetic reconnection into one plasma ring that then is radially compressed to form the ST configuration. Plasma currents of several hundred kA and plasma temperatures in the keV-range have been produced using this method, however until recently there was no full understanding of the merging-compression formation physics. In this paper we explain in detail, for the first time, all stages of the merging-compression plasma formation. This method will be used to create ST plasmas in the compact (R ~ 0.4-0.6 m) high field, high current (3 T/2 MA) ST40 tokamak. Moderate extrapolation from the available experimental data suggests the possibility of achieving plasma current ~2 MA, and 10 keV range temperatures at densities ~1-5 × 10 20 m −3 , bringing ST40 plasmas into a burning plasma (alpha particle heating) relevant conditions directly from the plasma formation. Issues connected with this approach for ST40 and future ST reactors are discussed

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Section: Stage 2: Merging Of Two Rings Reconnection and Formation Of ...mentioning

confidence: 89%

Merging-compression formation of high temperature tokamak plasma

Gryaznevich

Sykes

2017

Nucl. Fusion

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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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Measurement of the Lower Hybrid Wave Using RF Magnetic Probes on the TST-2 Spherical Tokamak

Tsujii

Yajima

et al. 2019

Plasma and Fusion Research

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Polarization-resolved spatial distribution of waves in the lower hybrid frequency range was measured using radio frequency magnetic probes (RFMPs) in the TST-2 spherical tokamak. Thirteen RFMPs were installed inside of the vacuum vessel, eight on the inboard-side, three on the outboard-side and two on the bottom-side. In TST-2, the lower hybrid wave (LHW) is excited by the outboard-launch antenna and the top-launch antenna. Higher plasma currents can be achieved using the top-launch antenna. Bottom-launch can be simulated by reversing the direction of the toroidal magnetic field. Propagation and absorption of the LHW were investigated numerically for outboard-, top-, and simulated bottom-launch at low and high plasma currents. Results of the wave measurement revealed different propagation characteristics for different launching, which agree partially with the results of numerical calculation.

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Measurement of the Local Current Density Inside a Current Sheet Using a Rogowski Coil Array on UTST Merging Plasmas

Cited by 4 publications

References 10 publications

Merging-compression formation of high temperature tokamak plasma

Merging-compression formation of high temperature tokamak plasma

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

Measurement of the Lower Hybrid Wave Using RF Magnetic Probes on the TST-2 Spherical Tokamak

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