Design and first results of a 4 MA strip line generator to produce magnetic pressure for material studies

Abstract

The key issues in high power, high energy applications such as electromagnetic launchers include safety,reliability, flexibility, efficiency, compactness, and cost. To explore some of the issues, a control scheme for a large current wave forming was designed, built and experimentally verified using a 2.4MJ capacitor bank. The capactior bank was made up of eight capacitor bank unit, each containing six capacitors connected in parallel. Therfore there were 48 capacitors in total, with ratings of 22kV and 5OkJ each. Each unit is charged through a charging switch that is operated by air pressure. For discharging each unit has a triggered vacuum switch(TVS) with ratings of 200kA and 25kV. Hence, flexibility of wave forming can be obtained by controlling the charging voltage and the discharging timings. The whole control system includes a personal computer, RS232 and RS485 converters, electrical/optical signal converters anf eight 80196 micro controller baesd capacitor-bank unit controllers. Hence, the PC besed controller can set the capacitor charging voltages and the TVS triggering timings of each capacitor-bank unit controller for the current wave forming. It also monitors and records the system status data. The RS232 and 485 converters minimize the use optical cables without reducing EM1 noise immunity and reliability, this resulting in cost reduction. The paper contains the complete control scheme and details of each subsystem unit. Some experimental current wave forming results are also included.The main goal of the presented HPP generator is to produce quasi-isentropic magnetic pressure ramps. This magnetic pressure should reach several hundreds of kbar for a generic copper sample of several tenth of mm2. This device will be a proof of principle of the use of compact (and then low cost) HPP generator to study high pressure dynamic behavior of materials. The peak current will reach at least 4 MA for a rise time varying from 180 ns to 300 ns. The dimensions of the generator will be a 5m*5m square based on a strip line design with solid dielectric insulation. 26 to 28 elementary generators made by HCEI, including multi gaps, multi channels switches, will be connected in parallel around the strip line. The technology used allows compactness of the pressurized gas, oil and vacuum. A peaking capacitor can be used to shape the current pulse. The paper present the features and the technology of the generator. Also, the first experimental results will be shown and the potentialities for material studies will be described. This work is supported by DGA/CEG under contract nOOO 25 044 ~ E mD Ec, m mat mi = generator and minimizes side equipment, avoiding use of mi 437