Measuring radiative losses in the globus-M spherical tokamak

We report on the first measurement of the absolute values of radiative losses in the Globus-M spherical tokamak. Measured by a wide-aperture pyroelectric bolometer, the radiative losses amount to about 30% of the total power deposited in the discharge, which is indicative of a sufficiently high purity of plasma in the experimental setup. Radiative losses on such a level have to be taken into account in determining the energy confinement time of the tokamak plasma. A new method is proposed for calibrating the bolometer using the data of other diagnostic techniques for the current ramp up stage, which provides for a coincidence up to within 15% with the calibration data obtained on a test bench.