Neutron dosimetry with 6LiF-rich TL sheet.

A (6)LiF-rich thermoluminescent sheet-type dosemeter ((6)LiF-rich NTL sheet) was developed for neutron 2D dosimetry. The dosemeter utilises the (6)Li(n, alpha)(3)H reaction to detect thermal neutrons. Responses of the (6)LiF-rich NTL sheet to neutrons were measured at the neutron beam irradiation facility for BNCT in JRR-4 Research Reactor at the Japan Atomic Energy Research Institute. Placement of a multi-leaf collimator at the output port of the neutron (beam) irradiation facility, produced either stripe- or round-shaped neutron distributions; the spatial distribution was measured using the developed NTL sheets. Direct measurements of neutron attenuation in water were also carried out using the developed NTL sheet, submersed in a water phantom. In each experiment, NTL sheets having natural abundance (7.9%) of LiF, and (6)LiF-enriched NTL (18.94%) sheet were irradiated under the same conditions. The ratio of thermoluminescence intensities of the (6)LiF-rich NTL sheet to that of the normal NTL sheet was compared to a theoretically calculated value. The experimental measurements are shown to be in good agreement with the calculations.