FERROUS SULPHATE G-VALUES FOR X-RAYS OF EFFECTIVE ENERGY 48-KEV AND 25-KEV

Measurements of ferrous sulphate G-values are described for X-ray beams of 250 and 50 kv, having mean photon energies of 48 and 25 kev. A Baldwin-Farmer ion chamber calibrated at N.P.L. was used at the higher energy, and a free air chamber at the lower energy. The results for 0.8N H2SO4 dosemeter solutions were 14.3 ± 0.3 and 13.7 ± 0.3 ions per 100 ev, while at 48 kev for 0.1N H2SO4 solutions the result was 14.1 ± 0.3 ions per 100 ev, with a G-value ratio for the two acid strengths of 1.011 ± 0.007. The G-value literature for photon energies below 100 kev is briefly reviewed and used as the basis for a table of recommended values in this photon energy range.