Seminar: Developments, features and prospects of crystal scintillators of the Cs2MCl6 family (M = Hf or Zr) to search for rare nuclear processes (Serge Nagorny)

Date

Jan 30, 2025

Time

3:00 PM - 4:00 PM

Language

en

Main Topic

Willkommen

Other Topics

Physik, Willkommen

Description

Recently, considerable interest has arisen in the development of crystal scintillators of the metal hexachlorides Cs2MCl6 (M = Hf or Zr) family thanks to their exceptional properties: a high light yield (up to 50,000 photons/MeV), good linearity in the energy response (down to 100 keV), good energy resolution (< 3.5% at 662 keV in the best configuration) and excellent pulse shape discrimination (PSD) between β/γ and α particles. Thanks to a high hafnium (27%) and zirconium (16%) containment these crystals are considered as promising detectors for studying the neutrinoless double beta decay (0ν2β) of 94,96Zr, as well as rare alpha decay of 174Hf and other Hf isotopes.

At the same time, currently-running experiments aiming to search for 0ν2β decay, rare or forbidden β and α decays reach an experimental sensitivity in terms of half-life at the order of 1016–1026 yr. This became feasible mainly due to the significant progress in detector techniques (bolometers, scintillating bolometers, semiconductor detectors, scintillators, and time-projection chambers) along with the development of high quality crystalline materials with tailored characteristics such as a high chemical- and radiopurity.
Therefore, here I will present results of the recent experiment that was performed using a Cs2HfCl6 (CHC) crystal scintillator in the “source = detector” experimental approach at the STELLA facility of Gran Sasso Underground Laboratory (Italy). In 2848 hours of data taking, α decay of 174Hf to the ground state of its daughter nuclide was observed with T1/2 = (7.0±1.2)×1016 yr. Experimental limits on rare processes in other Hf isotopes, such as the α decay to the ground state and the first excited states, were established at the level T1/2 ∼ 1015–1020 yr (90% C.L.) and presented here together with the future prospect of these measurements.
I will be also presenting the first complex study of Cs2ZrCl6 (CZC) scintillating crystals in terms of their chemical- and radio-purity, scintillating performance and pulse-shape discrimination ability. The low-background measurements with two CZC crystals (11 g and 24 g) over 456.5 days, supported their substantial radiopurity leading to a counting rate of 0.17 event/(kg⋅keV⋅yr) at the Qββ of 96Zr. Thus, experimental limits on different double beta decay modes of 94Zr and 96Zr were set at the level T1/2 ∼ 1017–1020 yr (90% C.L.). The detailed analysis of the internal background components, scintillating and thermodynamics properties was performed to be used in further developments of Cs2ZrCl6 detectors and to optimize the future large scale experiment.

Links

• Termindetails auf den Webseiten der TU Dresden (https://tu-dresden.de)

Last modified: Jan 30, 2025, 7:35:16 AM