Commutation losses of a multigap high voltage thyratron

Commutation loss measurements have been made on an EEV CX1171 three gap ceramic thyratron. It was operated in a 15 Ω impedance system, switching square pulses derived from a cable pulse forming network (PFN) directly into a matched load. The flat top current reached 1.6 kA at 80 kV charging voltage with a rise time of about 35 ns. Losses were measured from fu.i.dt, u and i being the tube voltage drop and current, respectively. Variable parameters were PFN voltage and reservoir voltage. Further investigation of voltages appearing on the intermediate gradient grids has allowed a better understanding of the commutation process and a localization of the losses within the tube. Ferrite saturable reactors have been series connected to the thyratron, primarily to reduce the commutation loss, but also to improve the di/dt. Both single-turn an multi-turn devices have been tested. At best a reduction in the commutation loss by almost an order of magnitude has been obtained. A comparison of thyratron losses as a function of PFN voltage is given for both single-turn and multi-turn reactors and also without saturable reactor