“…Thus CaF, : Mn discs can be used with polythene covers to measure the neutron component of the field, and with non-hydrogenous covers to measure the y-ray component. The short range of the recoil protons gives rise to an angular-dependent response which makes the system unsuitable for clinical use during fast neutron radiotherapy (Blum, Bewley and Heather 1972). An additional problem is insufficient sensitivity for use outside the main radiation field.…”