First measurements of the radiated power in MAST Upgrade using bolometry

MAST Upgrade features a suite of diagnostics to measure the power radiated by the plasma. There are arrays of resistive bolometers which provide both poloidal and toroidal coverage of the main chamber. There are also arrays of resistive bolometers in the lower Super-X divertor chamber which measure the radiated power from the outer leg of the divertor in both conventional and Super-X configurations. The bolometer sensors are connected to an FPGA-based electronics system which manages the excitation and calibration of the sensors as well as data acquisition.

In addition to the resistive bolometer arrays, a prototype infra-red video bolometer (IRVB) has been installed. This system has a 2D field of view covering the lower half of the main chamber, the lower X point, and also the lower divertor chamber with a tangential view. The IRVB has a higher equivalent channel count than the resistive bolometer arrays and has coverage in certain regions which is lacking the in resistive bolometer system.

We present here the first measurements taken with these diagnostics in the MU01 experimental campaign. Techniques to overcome high noise levels on the resistive bolometers due to pickup from MAST Upgrade’s switched-mode power supplies are presented, along with comparisons of the levels of radiated power in the main chamber and divertor. 2D emissivity profiles from the IRVB are shown, including radiation at the X point and divertor throat. A direct comparison of the radiation measurements from the resistive bolometers and IRVB in areas where these systems share coverage is also presented, and the implications for using both diagnostics in an integrated manner for improved overall coverage of the radiated power are explored.