Thermographic study of heat load asymmetries during MAST L-mode discharges

A long wavelength range infrared (LWIR) camera has been installed on MAST to compliment the existing medium wave infrared (MWIR) system. Simultaneous LWIR/MWIR temperature measurements have been made in the lower and upper divertors of MAST. As expected, the LWIR system is less sensitive to disturbances from hot spots on the surface. A thorough correction of the surface effects using both systems has improved the reliability of the heat flux calculations in MAST. A careful assessment of the heat load asymmetries as a function of the magnetic geometry has been carried out during a variety of L-mode discharges (single and double null, reversed and forward field). In all cases, most of the energy arriving in the scrape-off layer goes to the outer divertor. The in/out power ratio is found to be different for lower and upper single-null discharges with more power going to the outer divertor in the latter case. In addition, it is found that the heat flux profile width is different in the upper and lower divertor. The heat flux profile width at the secondary strike point increases with increasing vertical bar delta r(sep)vertical bar.