Surface Doses in the Cobalt-60 Facility at Armed Forces Radiobiology Research Institute.
Abstract
The surface doses in the Cobalt-60 Facility at the Armed Forces Radiobiology Research Institute were measured using a Capentec Model PS-033 0.5 cm cu parallel plate ionization chamber. With the source in the unilateral mode, the dose in the buildup region (0-5 mm depth) was measured and compared to the equilibrium dose for exposure rates ranging from 5 to 3500 roentgen/minute. It was determined that the usual 'skin-sparing' effect of cobalt-60 beams does not exist in the AFRRI Cobalt-60 Facility; in fact, the dose at a depth of 1 mm was as high as 137% of the equilibrium dose. The surface dose increased relative to the equilibrium dose as the source was moved closer to the chamber, indicating that the increased skin dose is due to the secondary electrons arising within the cobalt-60 structural components. These dose gradients in the buildup region should be considered when using the Cobalt-60 Facility for experimental irradiations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1984
- Accession Number
- ADA141109
Entities
People
- G. H. Zeman
Organizations
- Armed Forces Radiobiology Research Institute