Angle and Distance Resolved Dosimetry from a Linear Induction Accelerator Target Chamber.

The Dual Axis Radiographic Test Facility (DARHT) contains two linear induction

accelerators that utilize currents of 1.6-2 kA and beam energies of 16-20 MeV to produce

Bremsstrahlung x-rays after striking a heavy metal target. When interacting with nearby matter,

the x-rays deliver an initial dose of radiation along with some background scatter. This initial dose

can be determined through various methods of dosimetry. Measurements collected using direct-

reading dosimeters (DRD) indicated that at 3.18 m from the assumed source of radiation, the dose

was 0 rads/mC ±1.5 rads/mC at 90° from the electron beam direction and at 0.68 m the dose was

about 16 rads/mC ±2.4 rads/mC over an arc from 90° to about 43°. In trying to calculate a r-2

radiation decrease, it was found that there was a significant amount of scattered background

radiation. Due to the limitations of the DRDs, another dosimetry technique using the

photoactivation of thin metal foils is being developed. Using the photon flux and associated

energies detected from the activated foil, the initial doses will be calculated for Zn-64, Cu-63, Cu-

65, Mo-92, Ag-107, and In-115. Combining knowledge and calculations from the DRD and

activation methods, a safe distance from the source can be determined for present and future

electronics, equipment, and workers.