Improvements to the High-Field-Side Transient CHI System on QUEST

Kuroda, Kengoh; Raman, R.; Hasegawa, Makoto; Onchi, Takumi; Hanada, K.; Ono, M.; Nelson, B. A.; Rogers, John A.; Ikezoe, Ryuya; Idei, H.; Ido, T.; Mitarai, O.; Nagata, Masayoshi; Shoji, K.; Nagata, T.; Higashijima, A.; Shimabukuro, Shun; Niiya, Isao; Sekiya, I.; Kojima, Shinichiro; Nakamura, K.; Takase, Y.; Murakami, S.

doi:10.1007/s10894-022-00338-4

Cited by 1 publication

(2 citation statements)

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“…The first application of CHI on QUEST used a configuration referred to as low field side injection in which the CHI electrode was biased with respect to the outer vessel wall of QUEST [17]. In this configuration, as the CHI plasma filled the vessel, it was found that the injector flux footprint locations on the electrodes moved away from each other [18]. As described below, this condition is not suitable for the formation of closed flux surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…Biasing the CHI electrode with respect to the inner wall in a configuration referred to as high field side (HFS) injection was a potential way to resolve this issue. However, as the required modifications to the QUEST divertor region were substantial, to assess its potential, in a subsequent study, a simpler version of the HFS configuration was tested [18]. While this configuration demonstrated discharge evolution into the vessel, and suggested the potential for closed flux formation, it was plagued by spurious arcs.…”

Section: Introductionmentioning

confidence: 99%

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Demonstration of transient CHI startup using a floating biased electrode configuration

Kuroda,

Raman,

Onchi

et al. 2023

Nucl. Fusion

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Results from the successful solenoid-free plasma startup using the method of transient Coaxial Helicity Injection (Transient CHI) in the QUEST Spherical Tokamak (ST) are reported. Unlike previous applications of CHI on HIT-II and on NSTX which required two toroidal insulating breaks to the vacuum vessel, QUEST uses a first of its kind, Floating Single Biased (FSB) electrode configuration, which does not use such a vacuum break. Instead, the CHI electrode is simply insulated from the outer lower divertor plate support structure. This configuration is much more suitable for implementation in a fusion reactor than the previous configurations. Transient CHI generated toroidal currents of 135 kA were obtained. The toroidal current during the formation of a closed flux configuration was over 50 kA. These results bode well for the application of transient CHI in a new generation of compact high-field STs and tokamaks in which the space for the central solenoid is very restricted.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%