[Table of Contents]

Plasma and Fusion Research

Volume 9, 1302057 (2014)

Letters

Effect on Plasma Performance of a Single MHD Mode Feedback Control in Low-Aspect-Ratio RFP RELAX
Hiroyuki TANAKA, Sadao MASAMUNE, Seiya NAKAKI, Akio SANPEI, Kanae NISHIMURA, Ryosuke KODERA, Ryota UEBA, Go ISHII, Haruhiko HIMURA and Roberto PACCAGNELLA1)
Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
1)
Consorzio RFX, Associazione EURATOM-ENEA sulla Fusione, I-35127 Padova, Italy
(Received 29 August 2013 / Accepted 12 March 2014 / Published 10 June 2014)

Abstract

A feedback control system for the stabilization of resistive wall mode (RWM) was applied to a low-aspect-ratio reversed field pinch (RFP) with minimum power supply capabilities to control the single mode. The system consists of 64 saddle coils (4 and 16 in poloidal and toroidal direction, respectively) in the actuator covering the whole torus on the outer surface of the vacuum vessel. The sensor coils also have the same structure. The saddle coils are connected in series to control the single m/n = 1/2 mode, which has the largest growth rate in RELAX. The radial component of the magnetic field from the sensor coils was suppressed to the preset level and the m/n = 1/2 magnetic mode, which otherwise grows with field penetration time of the vessel, was reduced to 0.1% of the edge poloidal field throughout the discharge. The RFP discharge duration has been extended to ∼3.5 ms, the upper bound determined by the saturation of the iron core. Finally, the MHD control issues in a low-A machine are discussed.

Keywords

reversed field pinch (RFP), resistive wall mode (RWM), active MHD control

DOI: 10.1585/pfr.9.1302057

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This paper may be cited as follows:

Hiroyuki TANAKA, Sadao MASAMUNE, Seiya NAKAKI, Akio SANPEI, Kanae NISHIMURA, Ryosuke KODERA, Ryota UEBA, Go ISHII, Haruhiko HIMURA and Roberto PACCAGNELLA, Plasma Fusion Res. 9, 1302057 (2014).