E Minor upgrade

The E Minor machine at AWE Aldermaston was originally designed and built as a test-bed for the Marx generator of the 10MV, 80ns Mogul E Flash X-Ray machine. For this purpose it had a short (40ns) oil insulated Blumlein, which originally fed a resistive load. After Mogul E was completed, E Minor was converted into a flash X-Ray machine using an existing, surplus insulator stack from another machine on site (EROS). Unfortunately this insulator stack is only capable of holding off 5.5MV, well below the maximum possible output of the E-Minor Marx. To continue the X-ray diode development work required for the proposed Hydrodynamics Research Facility (HRF), E Minor needs to be upgraded so that it can deliver a 10MV pulse. E Minor will be upgraded to full voltage operation by fitting a Mogul-E-style insulator stack, requiring modifications to the front end of the machine and to the building in which it is housed. 2d electrostatic modelling software has been used to design the new front end the machine. The pre-pulse switch has been enlarged for the higher voltage operation, the toroid on the intermediate cylinder of the Blumlein will increase in radius for the same reason and the field shapers that flatten the electric field across the insulator stack have been optimised.