Absorbed dose measurement and LET determination with TLDs in space

For determination of the average LET in complex mixed radiation fields, a new method was developed using the LET dependent changes of the peak height ratios in thermoluminescence glow curves (HTR). Various types of standard and laboratory made TLDs were calibrated in alpha, beta, gamma and neutron fields and in heavy charged particles beams. These calibrated TL phosphors were used on space station MIR in order to determine the equivalent dose. During the long-term mission of 5 months in the summer of 1991 the dose rate was 0.24 ± 0.01 mGy.d-1 with an average LET (tissue) of 6.2 ± 0.25 keV.μm-1, and during an 8 day short-term mission October 1991 0.204 ± 0.003 mGy.d-1 with a LET of 6.5 ± 0.30 keV.μm-1. The new method was alos used for measurements carried out on satellite PHOTON-8 (1992) and on satellite BION-10 (1993) to obtain more information about the changes of the average LET of space radiation with the variation of the shielding. An increase in the average LET from 0.35 to 10 keV.μ-1 dependent on the absorber thickness from 1.14 mg.cm-2 to 2.5 g.cm-2 was measured. The method was also used for determination of the characteristics of the low energy electron component of space radiation on BION-10 and for the determination of the average LET on board high altitude aircraft. (author)