Directed current shedding experiments from a magnetically insulated transmission line

Summary form only given. For the next generation radiography machines at AWE it is planned to move to an inductive voltage adder (IVA) design running at 14 MV and over 100 kA. The high impedance diodes proposed to be used on this machine, such as the paraxial diode, need 30-40 kA of current. The excess current is currently shed into the vacuum chamber walls by the field shaper situated directly before the diode region. The greater currents and energy of the new IVA machine means that this shed current produces a significant secondary X-ray source which is costly to shield against. These experiments were aimed at moving this secondary source back from near the X-ray diode to a position where it could be more easily dealt with. The X-ray machine Mogul E was used as it has the longest magnetically insulated transmission line (MITL) of the machines at AWE of 4 m. The vacuum envelope is made of two parts, which allows the use of a second current monitor without the need for reworking of the MITL. A new 4" MITL stalk was constructed to accommodate the additional field shaper half way along to dump the excess current, which has the option of different stalks for the diode feed after the current dump.