Characteristics of laser-triggered vacuum switch

A bidirectional pulse generator system is under development to obtain a high-current charged particle beam using a linear induction accelerator without induction magnetic cores, which are usually loaded in an accelerating cavity. Experimental results obtained by using a conventional trigatron gas-filled gap switch have shown that it is necessary to reduce the inductance of switch to get an ideal bidirectional pulse. As a low-inductance gap switch, a laser-triggered multi-arc vacuum switch was adopted and its electrical characteristics and the behavior of ablated plasma in the gap were investigated. The switch electrodes were made of copper or aluminum, the surfaces of which were irradiated through lenses by the fundamental (1064 nm) or the third harmonics (355 nm) of Q-switched Nd:YAG laser. The maximum output energy and the pulse width of the laser are 650 mJ and 4-7 ns, respectively. Experimental results show that the laser-triggered multi-arc vacuum switch is adequate for a main switch of a bidirectional pulse generator.