Design of a radiographic integrated test stand (RITS) based on a voltage adder, to drive a diode immersed in a high magnetic field

Recent experiments [1] have adapted existing magnetically insulated inducti on voltage adders.(Sabre, Hermes III) to drive a 10-MV diode immersed in ma gnetic fields as high as 50 T. In such a diode, an electron beam of tens of kiloamperes can be confined by the magnetic field to a diameter of about 1 mm, and when it strikes a high-Z anode, it can create a bremsstrahlung X-r ay source intense enough to radiograph massive objects with high resolution . The radiographic integrated test stand (RITS) is an adder system designed specially to drive such diodes, and it will be used to develop and exploit them. As in other adder-based pulsers, such as Sabre, Hermes III, and Kalif-Helia , the induction cells have amorphous-iron cores, and the pulse-forming syst em consists of water dielectric pulselines and self-closing water snitches that are pulse-charged from Marx-charged intermediate water capacitors thro ugh laser-triggered Rimfire snitches. An oil prepulse switch in series with each pulseline is designed to reduce cathode prepulse to less than +/-5 kV , and a means is provided to bias the cathode and avoid negative prepulse e ntirely. The RITS pulse-forming system consists of two modules. Each module has one Marx that charges two 3-MV intermediate stores, each of which char ges three 7.8-Omega pulselines, making sis pulselines per module. The two m odules in concert can supply 1.35-MV, 50-ns pulses to a 12-cell adder and t hus drive a 16-MV diode with a single pulse. The 1.35-MV induction cells ea ch have a single-point feed, from which a single, slotted azimuthal oil tra nsmission line distributes energy uniformly around the cell. The modules ca n also be pulsed separately at different times, either to power two 8-MV ad ders that each drive one of two closely spaced cathodes immersed in a commo n magnetic field or to provide two separate pulses to a common six-cell add er and a single 8-MV diode; in these two-pulse modes, the spacing of the tw o 50-ns pulses may be chosen to be anything from a fe rv hundred nanosecond s upward. The use of only one pulseline per cell has been shown to increase the exten t to which the cell voltages can vary with the timing of closure of the wat er sn itches. This and all other functions of RITS have been simulated in d etail, and a conservative electrical design has been developed. This will b e illustrated, along with the conceptual design of a pulse-sorting network that can couple two pulselines efficiently to one cell when the two RITS mo dules drive a common adder in two-pulse mode.