Plasma current and position feedback control in ADITYA Tokamak

Ohmic heating power supply is used in ADITYA Tokamak for plasma breakdown and current drive. Presently the ohmic coils store a magnetic flux of 0.40 V s and high di/dt is created for the required loop voltage. After the plasma breakdown the plasma current control is made active with the difference of reference plasma current and measured plasma current to drive the PI regulator, which regulates the ohmic falling current. The vertical field current is also made proportional to plasma current by feedback control at appropriate time. The control scheme adopted and the results with the feedback control are described in this paper. We could improve the plasma current as well as plasma current flattop by employing the plasma current feed back control. Further to correct the radial position in fast time scale, four-quadrant transistor switched bridge inverter power supply by plasma position feedback control is proposed. On line +/-DeltaX (by position coils) position signal is given to PI control and polarity detector accordingly the current is amplified by the bridge inverter and fed to the four set of feedback coils which shifts the plasma position on radial directions. (C) 2003 Elsevier Science B.V. All rights reserved.