[en] Two strong thermal peaks in the wavelength range 220-420 nm have been detected at 128 and 140 K in LiF:Mg,Cu, at 123 and 135 K in LiF:Mg,Cu,P and at 125 and 133 K in LiF:Mg,Cu,Si, respectively. The origin of these main TL peaks is discussed in terms of defect perturbed H-F and V_K-e type recombination, respectively. The relative intensity between the two peaks in each sample and the emission spectra are dependent on the dopants. Annealing at 240-390 deg. C can modify the low temperature TL features, especially in those samples doped with three impurities. The low temperature data give some clues to select most favourable dopants for future LiF-type dosimeters