Transfer dosemeters for fast neutron sources

The increasing use of fast neutron sources in radiobiology, radiotherapy, etc. makes dosimetry intercomparisons (intercalibrations) by mail desirable. After comparing the relative advantages and disadvantages of the various available integrating fast neutron detectors, fission fragment track etching was chosen because such detectors can be made sufficiently small, rugged, fading resistant, inexpensive and accurate. Using several combinations of 232Th or 237Np as fissile materials, and organic and inorganic track detectors, it was established that both automatic spark counting and visual track counting techniques can be developed to cover the desirable dose range (approximately 50 to 500 rad) with sufficient accuracy (sigma <= 5%). One possible source of errors is the overlapping size distributions of fission fragment and recoil particle tracks in organic foils exposed at high neutron energies. Several approaches to reduce this problem are discussed. (author)