The 200kV Gas Spark Switch Design And Breakdown Characteristic Research For Fast Linear Transformer Driver

Modular linear transformer driver (LTD) is a novel fast discharge high power pulsed source on primary storage energy. It can realize many LTD modules in series or parallel connection conveniently. During the last few years, the LTD can acquire the rise time of 100～200ns of high power pulse in abroad. It is probably that LTD can directly drive the high power laser, microwave, electron beam, ion beam diode and the Z–pinch plasma radiation load etc. The primary discharge switch is one of the key devices in LTD. For acquiring a short rise time of the LTD pulse current, it requests the switch inductance is possibly small. Because the LTD primary adopts many bricks parallel working, a number of switches must discharge synchronous and each switch requests a low jitter. Therefore solved the switch low inductance and low jitter is the key that the LTD acquires short pulse and synchronous triggering.According to the latest progress and direct-drive request of domestic and international modularization fast LTD, this paper develops a±100kV multi-gap multi-channel switch suitable for modularization fast LTD, the switch self inductance less than 50nH. Analyzed the main influence factor of spark switch inductance and jitter, the method to reduce inductance and jitter of the gas spark switch is putted forward. Designed a kind of insulator structure that dig a slot plane inside to support the middle electrode of the multi-gap switch, it solves middle electrode of the multi-electrode switch fix hardly parallelism and coaxial. The experiment studies the self-breakdown characteristic of the switch, the research results indicate that baking the switch electrode can raise self-breakdown voltage and its stability. The experiment studies the influence of the switch triggering breakdown characteristic of the switch with the working voltage ratio, trigger voltage, polarity and insulate resistance. The typical results are shown as follows: the postponing time as well as its jitter is decreasing while the working voltage ratio is increasing. The switch postponing time can achieve less than 60 ns with jitter less than 4 ns while the working voltage ratio larger than 75% and trigger voltage larger than 70kV. Faster voltage rise speed of switch gap can be gained from reducing the trigger resistance, therefore a small postponing time and jitter will be obtained. The postponing time and jitter falls dramatically with the increase of trigger voltage, it should be better to choose a trigger voltage as high as possible. The experiment studies the influence of the switch multi-channel formation with the switch operating voltage, triggering voltage through the method that the short discharge current estimates the switch inductance in different state. The experiment result shows that the switch inductance decreases with the increase of operating voltage and triggering voltage, from self-breakdown about 46nH to about 21nH. The operating voltage and trigger voltage is higher, the discharge channel is formed easier. The multi-gap multi-channel switch has already used for fast LTD module brick experiment. LTD brick short current rise time (10%～90%) is about the 86 ns. The brick inductance is about the 270nH. The experiment indicates the designed switch satisfies the requirement of the fast modular LTD.