Improvement of radiopurity level of enriched 116CdWO4 and ZnWO4 crystal scintillators by recrystallization

Low background techniques in bolometers for double-beta decay search

“…An evident increase of the residual radioactive contamination along the 116 CdWO 4 crystal boule 76,85,86,117 demonstrates the segregation of U/Th during the CdWO 4 growth. This fact has been recently used to improve the radiopurity of one sample by recrystallization, 121 in particular the 228 Th content was reduced by a factor ≈10, down to the level 0.01 mBq/kg. The 113 Cd issue of the 116 CdWO 4 scintillator has been solved by using highly enriched 116 Cd in the production of the 0.4-kg 116…”

New development of radiopure ZnWO4 crystal scintillators

“…This offers a possibility to point out the presence of heavy ionizing particles with a preferred direction (such as recoil nuclei induced by DM candidates interaction) with respect to the electromagnetic background by comparing the low energy distributions measured using different orientations of the crystal axes during the day [7][8][9]. The ZnWO 4 is a very promising crystal for this purpose offering suitable features [9][10][11][12][13][14][15]. This motivated the proposal of ADAMO (Anisotropic detectors for DArk Matter Observation), a project to perform an R&D to develop low background, high quality ZnWO 4 crystals for a pioneering experiment to investigate the directionality [9,[15][16][17][18].…”

Radiopure tungstate and molybdate crystal scintillators for double beta decay experiments

“…1 in [82]) by the low-thermal-gradient Czochralski method. The total α activity of uranium and thorium daughters was reduced by a factor ≈ 3, down to 1.6 mBq/kg [84].…”