Design And Experimental Study Of Multi-gap Gas Switch For LTD Module

Linear transformer driver(LTD)technology is the frontier and hottest area in development of Z pinch accelerator.It is also the best choice for Z-pinch Driven Fusion-Fission Reactor(Z-FFR)developing in China Academy of Engineering Physics.Energy oriented LTD drivers need up to hundreds of thousands of gas switches,resulting in a very stringent requirement on the performance of the switches.The self breakdown probability of each switch should be better than 10-7,and the lifetime must be more than 106.However,the performance of the gas switches used in the LTD stages currently is still far away from meeting the energy demand.In this paper,a±100kV multi-gap gas switch with low jitter and low self breakdown probability was developed.Mechanism of gas breakdown,as well as impact factors of breakdown delay and jitter,was analyzed.In order to reduce the breakdown delay and jitter,low field non-uniform coefficient and high field distortion ratio was designed,considering the electrode geometry and voltage distinguishing method.Experimental study and static-electric simulation on the corona current characteristics of the switch were carried out.Structure of the corona needle of the switch was optimized,and consistent corona currents in each gap were achieved,leading to a significant improvement of voltage distinguishing in each gap,as well as a good performance of self breakdown probability.An experimental platform for switch study was built.The platform was similar to a single branch in an LTD stage.A simple and reliable pulse trigger method was designed,and the switch was fired rep-ratedly.The switch has a delay time of 40.1 ns with 1.3 ns jitter when operated at ± 90kV,which was 60%of the self-breakdown voltage.It was operated more than 500 times without self breakdown at a repetition frequency of 0.1 Hz.