New TL detectors for personal neutron dosimetry

One of the main objectives in the application of TL detectors to neutron dosimetry is to obtain a high ratio of neutron to gamma response for a better separation of the neutron component. In the case of 6LiF, one may reduce the effective thickness of the detector in order to exploit the difference between neutron and gamma absorption, either by making the sensitive layer of TL chip thinner or by reducing its transparency to TL light. Two new types of sintered 6LiF:Mg,Ti detectors have been developed: a sandwich detector with a non-thermoluminescent LiF base, and a detector in which the phosphor is mixed with graphite. Three thicknesses of the sensitive layer (45, 60, 80 mg.cm-2) and two carbon concentrations (1%, 4%) were tested. The detectors were irradiated by moderated neutrons from Pu-Be and 252Cf sources and by thermal neutrons from a nuclear research reactor. Results of measurements indicate that for the detector of thickness 45 mg.cm-2 the ratio of neutron to gamma response increases 2-4 times, compared with the Harshaw TLD-600 while the neutron sensitivity is maintained. Other dosimetric characteristics of the detector remain unchanged, making it possible to use standard annealing and readout procedures. The new detectors will be applied in a personal neutron albedo dosemeter with a detection limit better than 100 μSv in a gamma background of the range of several mSv. (author)