Measurement of thermal wall-load distribution caused by the locked mode in a reversed-field pinch plasma

Spatially localized heat flux due to the locked mode in a reversed-field pinch device, TPE-RX, is investigated by using a multipoint vessel temperature monitoring system (VTMS) which has 268 thermocouples distributed on the outer surface of the vessel system. It is shown by two-dimensional mapping that the locally enhanced thermal wall load correlates closely with the mode locking positions. Heat flux shows spatial peaks (full width at half maximum) of ∼10° and ∼100° in the toroidal and poloidal directions, respectively. Typical heat flux at the locked position is estimated to be of the order of 100 MW/m2, and the increment of the vessel temperature on the plasma side-surface exceeds 1000° with 0.35 MA plasma current.