Plasma position and shape control device

A signal of a magnetic sensor and a signal of a temperature sensor of a limiter or a Langmuir probe are used as a signal containing information of position and shape of plasmas. The magnetic sensor is disposed near the plasmas, and the limiter or the Langmuir probe are disposed near the magnetic surface of the outermost shell of plasmas. Since an error due to zero-point drift of an integrator of the magnetic sensor or change of magnetic field detection sensitivity can be removed by passing the magnetic signals through a high pass filter since the frequency is low. Accordingly, when an instruction value calculated from low frequency components of signals of the limiter temperature sensor or the Langmuir probe is added to the instruction value passed through the high pass filter, a plasma position and shape control coil instruction value can be obtained and accurate control can be conducted. In view of the above, plasmas can be kept stably for a long period of time without worry of causing local destruction or failure of reactor walls. (N.H.)