Precision 25 kV Pulse and RF Suppression in a 75 kHz Kicker

An international collaboration plans to measure the lifetime (~2 mus) of the muon to a precision of 1 ppm. The "MuLan" experiment is in progress at the Paul Scherrer Institut (PSI) in Switzerland. This experiment requires a fast beam line kicker, which can turn the beam on and off, to invoke an artificial time structure on the continuous beam which has a 50.6 MHz time microstructure. The kicker was designed and built at TRIUMF and installed at PSI in June 2003. Tests at PSI showed that RF from the kicker interfered with experimental detectors. Also it was realized that the specification for the flattop of the voltage pulse was not adequate for this precision experiment. Significant reduction in the RF and improvement in the pulse flattop were required. The kicker was returned to TRIUMF, and extensive changes were made, based on detailed measurements and PSpice simulations. After the changes the RF was reduced by a factor of more than 5000. The flattop variation, for a 22 mus pulse duration, was reduced from 0.18% to less than 0.001%: in addition the pulse overshoot was reduced from 10% to 2%.