Abstract
Background coming from the ^{42}Ar decay chain is considered to be one of the most relevant for the Gerda experiment, which searches for the neutrinoless double beta decay of ^{76}Ge. The sensitivity strongly relies on the absence of background around the Q-value of the decay. Background coming from ^{42}K, a progeny of ^{42}Ar, can contribute to that background via electrons from the continuous spectrum with an endpoint at 3.5 MeV. Research and development on the suppression methods targeting this source of background were performed at the low-background test facility LArGe . It was demonstrated that by reducing ^{42}K ion collection on the surfaces of the broad energy germanium detectors in combination with pulse shape discrimination techniques and an argon scintillation veto, it is possible to suppress ^{42}K background by three orders of magnitude. This is sufficient for Phase II of the Gerda experiment.
Highlights
In Gerda bare germanium diodes immersed in liquid argon (LAr) are used both as a source and the detector of the neutrinoless double beta (0 ν β β) decay of 76Ge [1]
To improve the performance of the nylon mini-shroud we increased the concentration of TPB and replaced toluene by dichloromethane (DCM), the latter of which is used for the production of the reflector foils in Gerda Phase II [14]
In order to enhance the 42K signal, two 42Ar sources with activities of (5.18 ± 0.91) Bq and (79 ± 15) Bq were produced by irradiating a cell filled with gaseous nat Ar at the accelerator operated in the Maier-Leibnitz Laboratory (MLL) of the Technische Universität München (TUM) via the reaction 40Ar(7Li,α p)42Ar
Summary
In Gerda bare germanium diodes immersed in liquid argon (LAr) are used both as a source and the detector of the neutrinoless double beta (0 ν β β) decay of 76Ge [1]. BEGe detectors have better energy resolution and a significantly thinner dead layer than semi-coaxial detectors [3] The latter makes them prone to surface events from the beta particles, which can penetrate the dead layer. This kind of background is considered to be one of the most dangerous in Gerda Phase II. Cosmogenic 42Ar poses an additional source of background It is present in natural argon and decays into 42K.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
