MSE thermal birefringence and shot to shot reproducibility Motivation: MSE has poor reproducibility in q measurements Last campaign we determined this was caused by birefringence in L2 from temperature changes throughout the run day (1080523) Bench experiments support this hypothesis 20090401, Alcator Ideas Forum: MSE reproducibility, B. Mumgaard, S Scott, J. Ko, S Shiraiwa

Thermal Management Actions taken MSE thermal shield L2 mount O-ring seat Actions taken New L2 mount to thermally isolate lens from the MSE canister New heat shield for temperature control of entire canister Proposal A few identical shots throughout a run day to check reproducibility Preferably run days with significant RF heating for worst possible thermal environment 20090401, Alcator Ideas Forum: MSE reproducibility, B. Mumgaard, S Scott, J. Ko, S Shiraiwa