[en] The separation of the contributions of thermal neutrons and gamma rays when performing dosimetry is of high importance, since gamma rays are always present in neutron fields. Johnson and Luersen used pairs of 6^LiF + 7^LiF for albedo neutron dosimetry. They pointed out that the fading of 6^LiF for high LET radiation from the reaction (n,α) is considerably greater than for gamma rays, especially for longer storage periods. If not taken into account, this difference can cause significant errors in the determination of neutron and gamma ray doses. Thermoluminescent dosimetry in mixed neutron-gamma radiation fields can be performed by the pair method. Two LiF crystals are used, one containing mainly 6^Li and the other 7^Li. 6^Li detects gamma rays and low energy neutrons via the 6^Li(n,α)3^H reaction, whereas 7^Li responds almost exclusively to gamma rays. The difference between the two indicates the contribution due to slow neutrons. However, variations in the crystals' composition and hence different individual behavior, may pose significant practical problems