DESIGN OF A BENCHTOP ALPHA-PARTICLE IRRADIATOR

The design, construction and calibration of a convenient irradiator is described that provides controlled exposure to a uniform external sou rce of well-characterized alpha particles at a dose-rate of 0.99 cGy m in(-1). The use of a precis- ion photographic shutter allows the accur ate delivery of doses as low as 0.01 mGy (1 mrad) to cultured cells. S pecial features also include a helium environment and reciprocal colli mator that permits the use of collimators with different transmission factors to achieve differing dose-rates. A simple method is described to characterize the energy spectrum of alpha particles by use of parti cle range as measured by track etch.