Development of an air insulated fast LTD pulser for radiography application

Abstract

AWE is looking to replace its current Mevex X-ray machine (~800kV, 35kA, 60ns pulse) to improve reliability and maintainability. A design using an LTD insulated with dry air at atmospheric pressure has been proposed by ITHPP. A testbed using 3 cavities, made from 2 bricks of two GA35460M 8nF, 100kV capacitors, a multigap multichannel switch and a magnetic core, has been developed and extensively tested. The 3 cavities have been fired on a single low inductance resistive load made from a single volume of electrolytic solution. With a ~4.2Ω load, the 3 cavities deliver under vacuum ~145kV, 35kA, in a 84ns pulse (at FWHM). The system proves to operate with high reliability, high reproducibility (<0.4%, 1σ in power) and very low jitter (<2ns, 1σ for the full system). The system and its subsidiaries (trigger system, premagnetization generator, charge and dump system, command-control) will be described and the experimental results presented. The design of the full generator, that will use 17 cavities in series to produce the 800kV output voltage on a vacuum insulated line and a 23-25Ω diode, is on-going and will also be presented. The machine should be capable of operating in negative and positive polarity to satisfy operational requirements given by AWE.