The Dortmund Low Background Facility - Low-Background Gamma Ray Spectrometry with an Artificial Overburden

TL;DR

The Dortmund Low Background Facility employs an artificial overburden combined with advanced shielding and veto systems to enable low-background gamma ray spectrometry at accessible locations, achieving competitive sensitivity.

Contribution

It introduces a novel low-background gamma spectrometry setup using artificial overburden and advanced shielding at an accessible campus location.

Findings

Background count rate of 2.528±0.004 counts/kg/min between 40keV and 2700keV.

Detects primordial radionuclides at activity levels of a few 10 mBq/kg within a week.

Effective shielding reduces cosmic ray interference at surface level.

Abstract

High-purity germanium (HPGe) detectors used for low-background gamma ray spectrometry are usually operated under either a fairly low overburden of the order of one meter of water equivalent (mw.e.) or a high overburden of the order of 100mw.e. or more, e.g. in specialized underground laboratories. The Dortmund Low Background Facility (DLB) combines the advantages of both approaches. The artificial overburden of 10mw.e. already shields the hadronic component of cosmic rays. The inner shielding, featuring a state-of-the-art neutron shielding and an active muon veto, enables low-background gamma ray spectrometry at an easy-accessible location at the campus of the Technische Universit\"at Dortmund. The integral background count rate between 40keV and 2700keV is 2.528+-0.004counts/kg/minute. This enables activity measurements of primordial radionuclides in the range of some 10mBq/kg within a week of measurement time.