Doping concentration dependence on VUV luminescence of Tm:CaF2

Luminescence and scintillation properties of Tm3+ 0.1–15% doped CaF2 crystals were systematically investigated. The crystals were grown by a simple solidification method which allowed us to obtain single crystals conveniently. In X-ray induced radio luminescence spectra, the luminosity of the self-trapped-exciton (STE) emission of CaF2 at 270 nm decreased with increasing of Tm3+ concentration. The Tm3+ 5d-4f transition based emission lines appeared at 175 nm (4f115d high spin state (HS) → 3H6) and at 165 nm (low spin state (LS) to 3H6). Pulse height spectra were measured under α-ray irradiation by using vacuum ultra-violet (VUV) sensitive photomultiplier tube (PMT) R8778 and Tm3+ 0.1% doped specimen exhibited the highest light yield.

► Luminescence and scintillation properties of Tm3+ doped CaF2 were investigated.
► Tm3+ 0.1–15 mol% doped CaF2 crystals were grown by a simple solidification method.
► The self-trapped-exciton emission in CaF2 decreased with increasing of Tm3+ ions.
► Tm 0.1% doped CaF2 exhibited the highest light yield under alpha-ray excitation.