An advanced rotating T-R mapping and its diagnoses of TESLA 9-cell superconducting cavity

An advanced rotating temperature and radiation mapping has been developed for investigation of field emission and thermal breakdown of TESLA 9-cell superconducting cavities in superfluid He. More than 10,000 spots on cavity surfaces can be investigated in one turn with 5/spl deg/ angular stepping. We locate a heated area with maximum /spl Delta/T=3.3 K around the 5th cell's equator. A heat flux density of 5 W/cm/sup 2/ in the region /spl Delta/T=3 K and total heat power Q/spl sim/100 W going to LHe from the area were calculated. An emitter responsible for the heating was identified at the iris area (So=8 cm) of the same cell according to T-maps associated with a simulation of impacting electron trajectories. The cavity reached Eacc=20 MV/m. We briefly introduce the technical layout, experimental data and analysis results.