DAHRT accelerators update and plans for initial operation

The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will use two perpendicular electron linear induction accelerators to produce intense, bremsstrahlung X-ray pulses for flash radiography. We intend to produce measurements containing 3D information with sub-millimeter spatial of the interior features of very dense explosively driven objects. The facility will be completed in two phases with the first operational by June 1999 utilizing a single-pulse, 19.8-MeV, 2 to 4-kA, 60-ns accelerator (activated in March 1999), a high-resolution electro-optical X-ray imaging system, and other hydrodynamics testing systems. The second phase will be operational by Sept. 2002 and features the addition of a 20-MeV, 2 to 4-kA, 2-microsecond accelerator. Four short electron micropulses of variable pulse-width and spacing will be chopped out of the original, long accelerator pulse for producing time-resolved X-ray images. The second phase also features an extended, high-resolution electro-optical X-ray system with a framing speed of about 2-MHz. In this paper we present a Figure-Of-Merit for a X-ray based flash radiography system to motivate the selection of accelerator parameters. We will then present sub-system performance measurements from Phase 1, the physics of the interaction of our high-intensity beams with the X-ray conversion target, initial Phase 1 accelerator measurements (if available), and plans for operation. We will also discuss designs and prototype testing results for the 2-microsecond Phase 2 accelerator, including prototype induction cells and pulsed power, prototype kicker magnet performance to chop the beam, and design considerations for a multipulse X-ray conversion target.