Design of a driver for the Cygnus x-ray source
Corcoran P., Altes R., Douglas J., Nishimoto H., Smith I., Stevens R., Weidenheimer D., Gustwiller J., Maenchen JE., Carlson R., Cooperstein G., Droemer D., Hunt E., Johnson DL., White R.
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.