Absolute Measurement of Average Energy lost by Very Soft X-rays per Ion Pair in Air

FIG. 1 gives a survey of measurements made so far of W, the average energy lost by photons and particles per ion pair in air. At energies exceeding 10 keV. W is practically constant. At less than 10 keV. a tendency to higher values of W is indicated. The fairly large discrepancies between some of the results, especially at low energies, caused us to carry out an absolute measurement of W with very soft X-rays