Bolometer measurements of the radiated power and estimates of the effective ion charge Zeff on the Keda Torus eXperiment

Abstract We have measured the power radiated by the plasma in the Keda Torus eXperiment (KTX) using a 20-channel AXUV bolometer. The bolometer has a frequency response bandwidth of 40 kHz, spatial resolution better than 40 mm, and overlap between adjacent channels of about 20%. For an ultra-low q discharge, the radiated power obtained from the bolometer measurements is about 8.0% of the ohmic heating input power. In addition, together with the Hα-emission data, we have used the bolometer data to calculate the effective ion charge Zeff profile, which proves to agree well with a plasma-resistivity calculation and which is hollow in the central region of a poloidal cross-section of the KTX.