Electrostatic modelling of critical electrical components of the Mevex X-ray machine

Mevex is a type of X-ray machine used at AWE for flash radiography since the early 1980s. The operating principle of the machine is to switch charge, stored in a Mark bank, into a Blumlein pulse-forming line. This causes the inner Blumlein conductor to rise in voltage to about -800 kV, driving a self-magnetic pinch diode (SMP) to produce a 60-ns X-ray pulse of dose 1.4 Rad at 1 m, with an effective source size of 1.9 mm. The machine design is currently being adapted to enhance operability and extend operating life [1]. It is important, therefore, to ensure that the replacement design is resistant to electrical breakdown and so electrostatic modelling software (Opera-3D [2]) has been used to determine electric fields in the system and breakdown calculations performed.