Design of a driver for the Cygnus x-ray source
Cygnus is a prototype of a radiographic x-ray source leveraging existing hardware and designs to drive a rod-pinch diode at 2.2 MV. This high-resolution x-ray source is being developed to support the Sub-Critical Experiments Program at the Nevada Test Site, and as such employs a modular technology that is scaleable to higher voltages and can be readily deployed underground. The diode is driven by three Induction Voltage Adder (IVA) cells from the Sandia SABRE accelerator; threaded by a positive polarity vacuum coax that extends 2 m to the diode and is designed to operate below electron emission on the anodized outer electrode. The ∼40 ohm diode impedance requires a 40/(3*3)∼ 4.5 ohm source to drive the three IVA cavities in parallel, a convenient impedance for a single water coax. The water coax is further designed to serve as a long, passive water cable accommodating several bends to allow independent positioning of the pulse generator that drives the coax, the IVA, and diode x-ray source at the far end. This long water coax is driven by a water pulse-forming line originally developed for Sandia's Radiographic Integrated Test Stand (RITS). A low inductance commercial Marx charges the single PFL in times similar to the charge-times of parallel sets of PFLs driven by intermediate stores in larger IVA systems such as RITS, Hermes-III. The paper describes the Cygnus accelerator design and presents test results for some components.