Design criteria and performance parameters of an alpha irradiation device for cell studies

An alpha irradiation device is described that utilises a
commercially available disc-shaped americium-241 source of 8 cm
diameter. The alpha particles traverse a moving collimator and the
source is rotated to reduce the influence of source
inhomogeneities. Source, collimator and a shutter disc are mounted
in a container which is flushed with helium to reduce energy losses
of the alpha particles before reaching the exit foil. The shutter
disc is activated by a computer-controlled step motor. The broad
beam of alpha particles emerges from the exit window of the
container with a remaining range in tissue of about 15 mu m. An
intermittent computer-controlled use of a preabsorber makes it
possible to reduce dose differences within a depth up to 12.5 mu m
to not more than +or-3%. With the commercially available americium
sources a dose rate of 0.2 Gy min-1 is reached; this can be
increased by utilising a somewhat wider collimator.