Neutron dosimetry with spherical ionisation chambers V. Experimental measurements and comparison with calculations of the cavity size dependence of the specific ionisation

For pt.IV see ibid., vol.27, p.1455, 1982. An experiment is described in which the cavity size dependence of the ionisation per unit mass was investigated in three different neutron beams for chambers with tissue equivalent walls filled with tissue equivalent gas or air and for graphite chambers filled with carbon dioxide. Different cavity sizes were achieved by changing the gas pressure in the ionisation chamber. Special care was taken with the measurement and analysis of saturation curves. It was found that the specific charge, q, changed with cavity size by 2% for the chambers with tissue equivalent walls and by more than 10% for the C/CO₂ chamber for mass diameters, tau , from 0.1 to 3 mg cm^-2. These results are in agreement with the results calculated in parts III and IV (Rubach and Bichsel 1982).