RadChem 2018

Production of cosmogenic radionuclides in Ge spectrometers placed in deep underground: a comparison of measurements with Monte-Carlo simulations

16 May 2018, 09:15

15m

Marble Hall (Casino Conference Centre)

Verbal Radionuclides in the Environment, Radioecology RER 2

Speaker

Robert Breier (Comenium University, Bratislava)

Description

Environmental and rare nuclear physics experiments require operation of Ge spectrometers in deep underground laboratories. Cosmic-ray background of Ge gamma-spectrometers is decreased to such low-levels that observation of cosmogenic radionuclides produced e.g. in germanium (${}^{68}$Ge, ${}^{60}$Co, ${}^{65}$Zn, ${}^{54}$Mn) and copper (${}^{54}$Mn, ${}^{57}$Co, ${}^{60}$Co, ${}^{58}$Co) is possible. There are several ways of activation of construction materials by cosmic rays:

1. during production of Ge crystals and cryostats in the factory and
   their transport to an underground laboratory all the construction
   materials are irradiated by secondary cosmic rays (nucleons, muons)
2. after installation of the Ge spectrometer in a deep underground
   laboratory the cosmogenic radionuclides produced at sea level
   (mainly the short-lived ones) are decaying
3. new generation of cosmogenic radionuclides may be produced even at
   deep underground by penetrating muons and their secondaries, as well
   as by neutrons originating from radioactive contamination of Ge
   spectrometer construction materials, detector shielding, and
   surrounding environment.

In thiswork wepresent experimental background gamma-ray spectra of the large-volume OBELIX Ge spectrometer operating in the deepest underground laboratory in Europe (LaboratoireSouterrain de Modane, 4,800 m w.e) just after its installation and several years later, and compare them with Monte Carlo simulations. The background simulation model is based on GEANT4 software package.