Dosimetry of the fast neutron beam produced by the MRC cyclotron

The fast neutron beam produced by the Medical Research Council's cyclotron at Hammersmith Hospital, London, has been in use for radiotherapy since 1966 and for radiobiology for several years previous to that date. Since the inception of the fast neutron beam at Hammersmith we have been concerned particularly with maintaining reproducible and internally consistent dosimetry, with the knowledge that the absolute accuracy with which the accepted unit of absorbed dose, the rad, could be realized was poor.