procedure for the quantitative study of a material on a stoffeigenschaft, a change in the properties of a certain type of ionizing radiation effect

摘要

1284295 Radiation detection TROXLER ELECTRONIC LABORATORIES Inc 9 Sept 1969 [19 Dec 1968] 44472/69 Heading G1A In an arrangement for investigating a test sample 11, fast neutrons from a radio-isotope source 10 irradiate both the test and reference samples 11, 12 wherein they are converted to slow neutrons which produce output pulses from the detectors D1, D2 the reference output being used to gate the test output so that the counter 17 records the number of pulses produced by detector D1 in the same time period that D2 produces a pre-set number of pulses. A shield 13 transparent to fast neutrons but opaque to slow neutrons prevents interference between the test and reference channels. The divider 15 is set to a predetermined number, e.g. 250, 000, and on receipt of the first reference pulse a gate 16 is opened. Receipt of the 250,000th pulse closes the gate, and the accumulated test sample count in counter 17, which may be of the gas discharge tube type, can be read off. The neutron-moderating property of hydrogen in soil is the basis of a portable instrument, Fig. 6, for determining the hydrogen content of soils. Here the test sample is a layer of the soil, which may be a top layer or at some distance within the soil. The irradiated volume is defined by collimators on the source 10 and test detector D1. In other embodiments of the invention the property of the test specimen chosen for comparison with a reference specimen may be its absorption or scattering of -rays. In all cases a plurality of sources may be used to irradiate both the test and reference samples.