Pulse power performance of the Cygnus 1 and 2 radiographic sources

Cygnus is a two-axis radiographic X-ray facility designed to drive rod-pinch diode loads at 2.25 MV with a spot size of about 1 mm producing 4 Rads at 1 meter. This x-ray source was developed to support the Sub-Critical Experiments Program (SCE) at the Nevada Test Site (NTS) and is distinguished from other commercially available sources by a dramatically reduced spot size for high resolution radiography, higher reliability, and compact size and modularity for greater layout flexibility to fit within the size constraints of its ultimate under-ground site location [D. Weidenheimer et al., June 17-22, 2001]. The facility is composed of two virtually identical machines referred to as Cygnus 1 and Cygnus 2 that incorporate proven pulsed power technology. Each machine employs a Marx generator, pulse forming line (pfl), water coax transmission line, and inductive voltage adder (IVA) that drive a high vacuum rod-pinch diode. The pfl design was originally developed for the radiographic integrated test stand (RITS) [I. D. Smith et al., October 2002] and the IVA cells are from the Sandia SABRE [J. P. Corley et al., 1991] accelerator. The Cygnus 1 machine was constructed and fielded at the Los Alamos National Laboratory to undergo pulsed power component and reliability testing and for use to develop and optimize the rod-pinch diode load [J. R. Smith et al., June 23-28, 2002]. Later, Cygnus 2 was constructed and fielded at Titan-PSD for testing employing the changes and modifications that resulted from of the Cygnus 1 tests. At the time of this writing, Cygnus 2 has undergone testing of the pulsed power components up through the output of the water line where a dummy load was placed. A pulse has not yet been propagated through the water coax to the diode. This paper describes and compares the pulsed power performance of both Cygnus machines up to the output of the water line. The Cygnus testing program is a result of the cooperative effort of Titan PSD, Sandia National Laborato- y, Los Alamos National Laboratory, and Bechtel Nevada.