Performance Comparison of Three Models of Thyratron in LINAC Coherent Light Source

Three different models of high voltage thyratrons, CX1937AX, L4SSS and L4SSSS, are utilized as high voltage switches in eighty modulators which provide high power pulses to klystrons for the LINAC Coherent Light Source (LCLS) at SLAC. The L4SSS thyratron is hydrogen-filled and the CX1937AX and L4888S thyratrons are deuterium filled. The three models of thyratrons perform differently regarding to standard maintenance, jitter, end-of-life symptoms, and lifetime when used functionally identical modulators. In this paper, these behaviors and data will be compared, and characteristic waveforms will be presented. Some experimental and theoretical explanations for similarities and discrepancies will be briefly discussed.