Neutron sensitivity of Geiger-Muller photon dosemeters for neutron energies between 100 keV and 19 MeV

Because of its low fast neutron sensitivity the energy compensated Geiger-Muller (GM) counter is a useful photon dosemeter for mixed neutron-photon dosimetry. The ratio of the neutron sensitivity to the photon sensitivity, the ksub(u)ksub(u)ksub(u)ksub(u)-value, has recently been measured by various authors. The agreement between the results obtained with different methods is not always satisfactory. Recently a time-of-flight technique was developed to measure the -value accurately. Based on this technique the energy dependence of the -value of two different GM's (neutron energies of 0.1; 0.25; 0.57; 1.0; 2.5; 4.2; 5.0; 15.5 and 19.0 MeV) is reported. The -value measured by the time-of-flight technique is deduced from the prompt neutron response of the GM (i.e. the response within about 30 ns). A delayed neutron response results from activation of the GM components. Two Geiger-Muller counters, one with and one without the energy compensating tin filter, were irradiated with 15.5 MeV neutrons. Comparing their activations, we conclude that the activation of the tin filter is small compared with the activation in the Geiger-Muller counter tube itself. An analysis of the decay times and the saturation activities is presented. As conclusion, parameters necessary for the use of GM's in mixed neutron-photon field dosimetry are reported. (author)