Speaker
Description
Rare event search experiments, like the experiments searching for a direct evidence of dark matter and those searching for the neutrinoless double beta decay (0υDBD), are among the most exciting challenges of the modern physics. The sensitivity of such experiments is driven by the background, which depends substantially on the radio-purity of the materials used for the construction of the experimental apparatus. When scintillating crystals are used as detectors, dedicated production lines need to be conceived for the entire manufacturing process from the synthesis and conditioning of the powder used for crystal growth to the cutting and surface processing of the finished crystal, compliant with radio-purity constraints specific to rare event physics application. Besides routine check of impurities concentration, high sensitivity measurements are made for radio-isotope concentrations in raw materials, reactants, consumables, ancillaries and intermediary products.
When very expensive isotopically enriched materials are used for 0υDBD experiments, special precautions are taken for acquiring the maximum yield in the mass balance of all production stages.
The current work will make a review of scientific and technological aspects related to the crystal production for 0υDBD and dark matter search applications. Details will be given on the production of enriched zinc selenide (Zn82Se) and tellurium dioxide (130TeO2) crystals for 0υDBD experiments together with the performance of these crystals used as scintillating and Cerenkov bolometers respectively. The synthesis of ultrapure NaI powder and the growth and processing of NaI:Tl crystals for possible use in experiments dedicated to the direct detection of dark matter will also be described. In this case, given the chemical affinity between sodium and potassium, dedicated measures will be discussed for the reduction of potassium content below 10-8 g/g limit, imposed by radio-purity constraints. The work will also describe improvements brought to cutting edge measurement techniques like mass spectrometry (MS) for a fast, sensitive and efficient screening of the materials used for the production of crystals and the certification of the whole crystal production process in a reliable and reproducible way.
Acknowledgements
This work was made with the contribution of the Ministry of Education, Universities and Research of the Italian Republic, MAECI-PGR04136
