Single crystals were irradiated at room temperature and at 8K with energetic heavy ions (12C, 50Ti, 58Ni, 74Kr, 152Sm, 197Au, 208Pb and 238U) at 50 to 2600MeV. This provided mean electronic energy loss values ranging from 0.7 to 19keV/nm. The creation and evolution of color centers were investigated as a function of fluence and temperature by in situ absorption spectroscopy and thermo-stimulated luminescence, complemented by thermal annealing and optical bleaching. For irradiation at 8K, primary hole centers were observed which typically annihilated at between 10 and 80K. The efficiency of color center creation at 8K depended strongly upon the energy loss of the ions and was several times higher for U and Au ions than for C and Ti ions. Thermal spike estimations, taking account of the finite velocity of heat propagation, attributed these effects to the thermally stimulated separation of color centers in the genetic Frenkel pairs.

Thermal Spike Effect on Defect Evolution in NaCl Irradiated with Light and Heavy Ions at 8 and 300K. K.Schwartz, A.E.Volkov, K.O.Voss, M.V.Sorokin, C.Trautmann, R.Neumann: Nuclear Instruments and Methods in Physics Research B, 2006, 245[1], 204-9