Split magnetically insulated transmission line experiments

The larger radiographic machines at AWE, Mogul E, Mogul D and Superswarfs produce a single source of X-rays. It has been proposed that a future multi-axis radiographic facility may use a single machine to drive two or more diodes. In order to design such a machine, the magnetically insulated transmission line (MITL) feed would have to be divided into a number of load MITLs. These would then either be shaped to point at a single object or the X-ray outputs would have to be angled from the axes of the load MITLs to point at a single object. In order to identify and address any problems associated with driving two diodes and splitting the MITL, two series of experiments were conducted on one of the Superswarfs. The Superswarf flash X-ray machine incorporates a Marx generator, consisting of 30 0.5 μF capacitors arranged around a single switch column made up of 15 SF₆ switch gaps. This is connected to a Blumlein pulse forming line to provide a 55 ns 5.5 MV pulse across a diode. The first series of experiments showed that it is possible to drive two diodes from a single MITL machine. It also showed that, at 5 MV, it is possible to change the angle of the diode relative to the MITL. The experiment with the single diode set at 72° to the MITL resulted in no loss of diode performance. The second series of experiments proved that it is possible to split the MITL without losing current at the junction. Therefore, if the diodes on the split MITL set-up were turned through 90°, such that the diode axis crossed in the centre, it would be possible to produce two simultaneous radiographs of an object