Feedback control experiments on 1.0 and 1.5 cycle ac operations in the STOR-M tokamak

Abstract

Complete one cycle and 1.5 cycle ac operations are performed in the STOR-M tokamak with the plasma current of ∼20 kA using newly developed feedback control and Ohmic heating circuits. Bias voltage adjustment is installed in the plasma position circuit to optimize the plasma position in the second negative plasma current phase for multicycle ac operation. The key to successful, reproducible multicycle ac tokamak operations on STOR-M is to control both the total vertical field by the feedback control system and the plasma position by application of the bias voltage.

Modification of toroidal flow velocity through momentum Injection by compact torus injection into the STOR-M tokamak

“…While maintaining the toroidal field in the CCW direction (top view), the toroidal plasma current direction can be easily reversed by changing the current direction in the primary windings. The horizontal position feedback control system was already designed for alternating current operation in STOR-M and is able to handle the normal (CCW) and reversed (CW) tokamak discharge current directions in STOR-M without any further modifications [15].…”

Quasi-steady-state ac plasma current operation in HT-7 tokamak

“…AC operation was first demonstrated on a STOR-1M tokamak with a plasma current of 4 kA [1]. Plasma properties when the plasma current crosses zero and some key technologies have been introduced in several papers [2][3][4][5]. JET has demonstrated a full cycle of ac operation with a reactorrelevant plasma current of 2 MA, but with a dwell time between two half-cycles from 50 ms to 6 s, which means the ionization was lost when the plasma current crosses zero [6].…”

Investigation of Plasma Equilibrium in the Saskatchewan Torus‐Modified (STOR‐M) during Alternating Current Operation

“…To mitigate this problem, several square voltage pulses, marked as dist in Fig. 1, from a set of signal generators were added to the ∆H signal during the current crossing phases based on our best guess of the polarity of the ∆H signal saturation and the required current in the feedback windings [21]. This improved feedback position control system, combined with careful control of gas puffing pulses, significantly reduced the adjusting time required when the operation circuit is converted from the normal mode to the AC mode of operation as compared with the previous AC operation campaigns on STOR-M.…”