In situ Resonant Ultrasound Spectroscopy during irradiation of solids with relativistic heavy ions

Samples of steel, fused silica, CaF2, NaCl, and a (La,Eu)PO4 monazite ceramic were irradiated with 209Bi (130 GeV) and 238U (60 GeV) ions up to total fluences of 6×1011cm-2. During beam exposure, resonant ultrasound spectra were recorded. No radiation-induced changes in the density and elastic stiffness coefficients were observed when comparing samples before and after irradiation. The irradiation caused fully reversible shifts of the resonance frequencies in all samples except NaCl, silica and monazite irradiated with U ions. These reversible shifts are due to a temperature increase during irradiation. The heating process was modelled quantitatively by an energy balance model. The average thickness traversed by the ions was estimated from geometrical considerations and the energy deposition was calculated with the SRIM software. The results from the model and these calculations are in good agreement. For NaCl, silica and monazite, a degradation of the samples was observed. Hence, in situ Resonant Ultrasound Spectroscopy can be used to monitor sample integrity and temperatures in harsh radiation environments.