Low Background Gamma Spectroscopy Research Articles

Virtual reality (VR) simulation of a nuclear physics laboratory exercise

This paper outlines some of the benefits of using virtual reality (VR) in physics education at the university level. Based on the existing experimental infrastructure of the low-background gamma spectroscopy laboratory, a VR experiment has been designed which includes all the stages of the physical measurement process. Following the VR experiment, the students receive pre-prepared experimental data (gamma spectra) from which they extract a specific result (in this case, the mass of the deuteron) and accordingly validate some of the knowledge they acquire in the classroom. The most significant benefit of introducing VR into the education process is the opportunity for students to become familiar with experimental settings and procedures, in environments without similar infrastructure, as well as being provided with appropriate experimental material. An example from nuclear physics was taken because there is great scope in this field for the possible use of VR techniques in teaching. Only a few universities have adequate equipment to cover this field extensively, especially for advanced courses or master studies. This technique could be also applied in the teaching environment for a number of other experimental courses.

An improved half-life limit of the double beta decay of 94Zr into the excited state of 94Mo

A search for the double beta decay transition of 94Zr into the first excited state of 94Mo has been performed at the Felsenkeller underground laboratory in Dresden, Germany. A 341.1 g zirconium sample with natural isotopic composition has been measured for 43.9 d in an ultra low background gamma spectroscopy setup. No signal has been observed and a new best lower half-life limit is set as 5.2 × 1019 yr (90% CI). This limit is valid for the 0νββ and 2νββ decay into excited states of 94Mo but cannot distinguish between the two modes. Existing limits are improved by 50%.

Low-background gamma spectroscopy at the Boulby Underground Laboratory

The Boulby Underground Germanium Suite (BUGS) comprises three low-background, high-purity germanium detectors operating in the Boulby Underground Laboratory, located 1.1 km underground in the north-east of England, UK. BUGS utilises three types of detector to facilitate a high-sensitivity, high-throughput radio-assay programme to support the development of rare-event search experiments. A Broad Energy Germanium (BEGe) detector delivers sensitivity to low-energy gamma-rays such as those emitted by 210Pb and 234Th. A Small Anode Germanium (SAGe) well-type detector is employed for efficient screening of small samples. Finally, a standard p-type coaxial detector provides fast screening of standard samples. This paper presents the steps used to characterise the performance of these detectors for a variety of sample geometries, including the corrections applied to account for cascade summing effects. For low-density materials, BUGS is able to radio-assay to specific activities down to 3.6mBqkg−1 for 234Th and 6.6mBqkg−1 for 210Pb both of which have uncovered some significant equilibrium breaks in the 238U chain. In denser materials, where gamma-ray self-absorption increases, sensitivity is demonstrated to specific activities of 0.9mBqkg−1 for 226Ra, 1.1mBqkg−1 for 228Ra, 0.3mBqkg−1 for 224Ra, and 8.6mBqkg−1 for 40K with all upper limits at a 90% confidence level. These meet the requirements of most screening campaigns presently under way for rare-event search experiments, such as the LUX-ZEPLIN (LZ) dark matter experiment. We also highlight the ability of the BEGe detector to probe the X-ray fluorescence region which can be important to identify the presence of radioisotopes associated with neutron production; this is of particular relevance in experiments sensitive to nuclear recoils.

Low Background Counting at LBNL

The Low Background Facility (LBF) at Lawrence Berkeley National Laboratory in Berkeley, California provides low background gamma spectroscopy services to a wide array of experiments and projects. The analysis of samples takes place within two unique facilities; locally within a carefully-constructed, low background cave and remotely at an underground location that historically has operated underground in Oroville, CA, but has recently been relocated to the Sanford Underground Research Facility (SURF) in Lead, SD. These facilities provide a variety of gamma spectroscopy services to low background experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K) or common cosmogenic/anthropogenic products, as well as active screening via Neutron Activation Analysis for specific applications. The LBF also provides hosting services for general R&D testing in low background environments on the surface or underground for background testing of detector systems or similar prototyping. A general overview of the facilities, services, and sensitivities is presented. Recent activities and upgrades will also be presented, such as the completion of a 3π anticoincidence shield at the surface station and environmental monitoring of Fukushima fallout. The LBF is open to any users for counting services or collaboration on a wide variety of experiments and projects.

Low-background Gamma Spectroscopy at Sanford Underground Laboratory

Low-background Gamma Spectroscopy at Sanford Underground Laboratory

Installation of a muon veto for low background gamma spectroscopy at the LBNL low-background facility

An active veto system consisting of plastic scintillation panels was installed outside the Pb shielding of a 115% n-type HPGe detector in an effort to reduce background continuum generated by cosmic ray muons on the surface. The Low Background Facility at the Lawrence Berkeley National Laboratory performs low level assay (generally of primordial U, Th, K) of candidate construction materials for experiments that require a high level of radiopurity. The counting is performed in two facilities: one local surface site and a remote underground site of approximately 600m.w.e. For the recently installed veto system at the surface location, the top scintillator panel has been in use for nearly 1year and the full 3π anticoincidence shield was commissioned into normal counting operations in January 2013. The integrated background from 20 to 3600keV is reduced overall by a factor of 8, where most of the energy spectrum above 100keV achieves an overall reduction that varies from 8 to 10. A dramatic improvement of peak-to-background across the entire continuum is observed, greatly enhancing low-level peaks that would otherwise be obscured.

The new set-up in the Belgrade low-level and cosmic-ray laboratory

The Belgrade underground laboratory consists of two interconnected spaces, a ground level laboratory and a shallow underground one, at 25 meters of water equivalent. The laboratory hosts a low-background gamma spectroscopy system and cosmic-ray muon detectors. With the recently adopted digital data acquisition system it is possible to simultaneously study independent operations of the two detector systems, as well as processes induced by cosmic-ray muons in germanium spectrometers. Characteristics and potentials of the present experimental setup, together with some preliminary results for the flux of fast neutrons and stopped muons, are reported here.

Neutrons in the low-background Ge-detector vicinity estimated from different activation reactions

Neutrons produced by cosmic-ray muons in a detector shield and other surrounding materials can be captured or scattered by different nuclei in subsequent reactions. The gamma photons emitted after nuclear capture or scattering from produced Ge isotopes are used to estimate the neutron flux. If a bulk sample measured in some low background gamma spectroscopy system contains hydrogen, a high energy photon (of energy 2223keV) emitted in the process of deuterium production can be used to estimate the flux of thermal neutrons. Results obtained from the interaction of neutrons with H as well as with some Ge isotopes are computed and compared in this paper. The passive lead shield in a detector system is a source of a significant fraction of the gamma radiation induced by capture and inelastic scattering of neutrons. We also used gamma lines emitted by several Pb isotopes to estimate the neutron flux near a detector.

7Be analyses in seawater by low background gamma-spectroscopy

Oceanographers use the cosmogenic radionuclide 7Be (T 1/2 53 days) as a tracer for atmospheric input and a conservative tracer of mixing in the open ocean. This paper elucidates a method for improving the analysis of 7Be from seawater. The scavenging efficiency of Fe(OH)3 for each sample is measured by ICP-MS using stable 9Be as a yield monitor. Samples are gamma-counted in a large diameter (28 mm) well detector. The high purity germanium well detector is coupled with an active anti-coincidence cosmic guard to reduce the spectra background. The improved overall accuracy of the method and lower detection limit of the detector results in a lower volume of seawater needed for analyses. Results will be shown from a study of 7Be in the Sargasso Sea.

The chronology of the Neolithic sequence at Dikili Tash, Macedonia, Greece: TL dating of domestic ovens*

The chronological sequence of a major reference site for Neolithic periods in southeastern Europe and the Aegean, Dikili Tash (Macedonia, Greece), has been reassessed by TL. Baked adobe material samples extracted from domestic ovens, directly associated with specific occupational levels, have been studied. The fine‐grain technique has been used for equivalent dose determination. K, U and Th contents and the equilibrium state of U‐series have been measured by low‐background gamma spectroscopy. Since the archaeological levels were already partly excavated, the environmental dose‐rate was evaluated by a reconstruction technique combining laboratory analysis and on‐site measurements.The TL results (weighted average of multiple age determination, oven 400, middle of the Dikili Tash I (DT‐I) phase, 5500 ± 320 bc; oven 600, end of DT‐I, 4920 ± 310 bc; house 3, DT‐II, 4260 ± 280 bc; house 4, DT‐II, 4510 ± 410 bc) are in general agreement with the timeframe deduced from previous radiocarbon dates. This convergence strengthens the settlement's chronology, established now by independent dating methods.