Optical transmission radiation damage and recovery stimulation of DSB:Ce 3+ inorganic scintillation material V. Dormenev a, A. Borisevich b,v. Mechinsky b, M. Korjik b, D. Kozlov b, R.W. Novotny a a II. Physikalisches Institut Justus-Liebig-Universität, Gießen, Germany b Institute for Nuclear Problems, Minsk, Belarus
Introduction Content Radiation damage and recovery processes in heavy scintillation materials by the example of lead tungstate PbWO 4 New material DSB:Ce 3+ Properties Light Yield test results Optical Transmittance measurements Radiation induced absorption coefficient Recovery of the radiation damage Conclusions and Outlook
Radiation damage of inorganic scintillation materials Radiation damage of the optical transmittance of the scintilator leads to the degradation of the energy resolution of the electromagnetic calorimeter (EMC) The radiation damage of scintillation materials can be subdivided on two components: Electromagnetic component (g-quanta, e-, e+) Hadron component (p, n, and fragments due to interaction with heavy nuclei) Possible ways to recover the damage: Spontaneous recovery due to thermodynamical processes (suppressed at low temperatures) Annealing at temperatures >50 C can reduce the recovery time from weeks to days and even hours (difficulties with implementation in EMC) Stimulated recovery with illumination of the light in visible and IR range (can be easily implemented in EMC)
Damage of PbWO 4 crystal under g-irradiation 60 Co (E g 1.25 MeV) source, Dose rate = 2 Gy/min.
Damage of PbWO 4 crystal 24 GeV/c protons Integral fluence = 3*10 13 protons/cm 2 Length of the sample = 22 cm Longer annealing at 350 C allows to reach a full recovery G. Dissertori et al. NIM A 684 (2012) pp.57-62
Damage of PbWO 4 crystal 150 MeV protons Integral fluence = 1.8*10 13 protons/cm 2 Length of the sample = 5 cm Shift of the optical transmittance edge is observed after irradiation with integral fluence > 10 12 protons/cm 2
Stimulated recovery of the radiation damage of PbWO 4 crystal 60 Co (E g 1.25 MeV) source, Dose rate = 2 Gy/min Integral dose = 30 Gy Intensity of the stimulated recovery depends on wavelength
New scintillation material: DSB Ce 3+ Recently, a new scintillation material, DSB:Ce 3+, was announced [Baker Hughes International Information, 2013]. DSB is obtained by standard glass production technology in the dual system containing more than 50% of SiO 2 with successive thermal annealing. It can be produced in bulk and fiber forms with diameter up to 2mm and length up to 2000 mm. Mother glass is produced in the mold from the molten glass mass. Then it is subjected to annealing according to temperature program to improve its properties. ρ, g/cm 3 Zeff X o, cm λ max, nm LY, pe/mev LY(T),%/ o C Averaged scintillation decay time, ns Cutoff of undoped material, nm 3.8 51 3.3 420-440 100 0.05 40 310 Aim of research programm: to characterize first set of the samples; First batch of the materials to study radiation damage and recovery effects in DSB:Ce scintillation material
DSB tests: Light Yield measurements PMT: Hamamatsu R2059 (bialcali photocathode) T= +18 C Time gate: 4000 ns
DSB tests: Light Yield vs timegate Am-241 (E g = 59.5 kev)
DSB tests: Light Yield vs Temperature Temperature coefficient = +0.05%/ C for 10 microsecond timegate. It is less for all smaller time gates and it's definition is limited by the measurement error. timegate= 10 ms timegate= 4 ms timegate= 1 ms timegate= 500 ns timegate= 200 ns timegate= 100 ns timegate= 60 ns Temperature stabilization of the calorimeter is not necessary
DSB tests: Optical Transmittance Measurements of optical transmittance were done with Cary Varian 4000 spectrophotometer Irradiation conditions: 60 Co (E g 1.25 MeV) source, dose rate = 2 Gy/min. Some Admixture of Pr 3+ to Ce 3+ activator 500 Gy dose was chosen as working dose for the recovery tests
DSB tests: Radiation induced absorption coefficient dk = [Ln(T before /T after )]/d 500 Gy dose was chosen as working dose for the recovery tests
DSB tests: Recovery of radiation induced damage Radiation induced coefficient was normalized relatively value measured after irradiation with 500 Gy dose of g-irradiation Thermal annealing speeds up the recovery processes
DSB tests: Recovery of radiation induced damage
DSB tests: Recovery of radiation induced damage Intensity of the stimulated recovery depends on wavelength
DSB tests: Recovery of radiation induced damage Intensity of the stimulated recovery depends on wavelength
Tests results of DSB: Ce material: Conclusion and Outlook Light yield is around 100 phe/mev. It is comparable with LY value of PbWO 4 at -25 C It is no dependence of the Light Yield on the temperature in the range from at +25 C down to -45 C Spontaneous recovery of the radiation damage after g-irradiation was observed at room temperature Recovery processes can be speeded up by the illumination with light in visible- IR wavelength range. Future plans: Tests after proton irradiation @KVI (Groningen, Netherlands) E p 150 MeV, Integral fluence 10 14 protons/cm 2 @CERN (Geneve, Switzerland) E p = 24 GeV, Integral fluence 10 13 protons/cm 2