Thermal/structural Analysis of a Scrf Photocathode Electron Gun Cavity

The novel Superconducting Photocathode Electron Gun being developed by Advanced Energy Systems and Brookhaven National Laboratory was analyzed to determine surface temperature and stress levels from RF and laser heat loads while being cooled in a helium bath. Optimization of geometry with respect to thermal loads was required when looking at 4.2K vs. 1.8K bath temperature. Heat loads were developed from a SUPERFISH model and were determined for surface temperatures between 2K and 8K. These heat loads were included in the model as a function of the RF surface temperature requiring a non-linear solution. Material properties such as thermal conductivity were also included as a function of temperature. The laser load on the cathode surface dominates the loads from RF and therefore, a constant load is used in this region. Results show that the temperature of the cathode will not adversely affect the superconductivity of the cavity. Uncertainty of the coolant effectiveness requires that the laser power be increased at a slow rate. The geometry of the back of the cathode where it is in contact with the helium bath is critical and will be evaluated during the testing phase of the program.