Development and test of two high power conventional pulsers for radiography application

Abstract

This work concerns the development and testing of 2 radiography pulsers (~2MV, 650kA, ~100ns) to enhance the hydrodynamic testing capabilities of the Atomic Weapons Establishment (AWE) in Aldermaston (UK). The generators have to fire on a Plasma Filled Rod Pinch diode (PFRP) to provide two ultra-bright X-ray sources on 2 radiography axis separated by 45°. The design uses a high voltage high-energy 20-stage balanced Marx charged up to +/-100kV. It uses specifically developed switches operating under pressurized dry air. The machines do not use any SF6. This Marx is fired with a small jitter to charge a ~50ns deionized water Pulse Forming Line (PFL) up to an operating voltage of ~4.3MV (at +/-90kV Marx charge). The discharge of this line occurs thanks to a multi-channel triggered oil switch providing a low inductance and associated fast switching. The ~100ns width pulse generated is transmitted by a water transmission line to a vacuum chamber using a radial monolithic interface. This output is similar to the Naval Research Laboratory Gamble II generator on which was developed and tested the AWE’s PFRP diode. Initially, the generator fired on a resistive load prior to using a Large Area Diode (LAD) providing the ~3Ohm expected impedance. The Marx tank has a hydraulically operated side door under which the Marx can slide out and hang for ease of assembly and maintenance. So, the 2 machines have a handed design to accommodate their installation in a refurbished building. The general electrical and mechanical design of these generators, as well as the main problems encountered during the testing phase, have already been presented in [1]. This publication will therefore just remind the definition of the system and focus on the latest optimizations and results of the 2 machines, both on the resistive load and on the LAD. The operation of the main oil switch will also be described in detail.