Application of the thermoluminescent dosimetry to a pion beam.

The thermoluminescent dosimetry is currently applied to radiation therapy in order to measure dose distributions on phantoms or to control the dose in vivo for special procedures or critical organs. The application of this method to the SIN's (Switzerland) pion beam has been studied. Measurements have been made on the following thermoluminescent materials: 7LiF, 6LiF, Li(nat)F, Li2B4O7, CaF2 : Mn, and CaF2 : Dy. Except for the last one a reduction (10%) of the sensitivity of the phosphors has been observed in the peak relative to the plateau region. An increase of the 6LiF sensitivity relative to that of 7LiF has been pointed out due to the neutron background through the (n, alpha) reaction on 6Li. Glow curves of the LiF phosphors have been measured. A reduction (5%) of the intensities of peak 3 and 4 relative to peak 5 has been observed for irradiation in the peak region. This effect however can't be used in order to localize the dosimeter in the beam because the intensity of the thermoluminescence peaks shows a larger variability in a batch of dosimeters.