Background reduction in germanium spectrometers: Material selection, geometry, and shielding (original) (raw)

Study of the background components for a Ge(HP) detector in environmental radioactivity measurements

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994

A quantitative study of the environmental background components of a gamma-ray spectrum recorded with an unshielded p-type germanium detector has been performed. The contribution of each component to the background spectrum was analyzed separately using Monte Carlo simulation techniques.

Natural Background in Ge(Li) Spectrometers

Instrumentation Science & Technology, 1997

The natural background activity of a Ge(Li) spectrometer was measured and background reduction was evaluated. Twenty lines were observed in the energy spectrum, extendmg from 20 to 1000 keV. Background reduction, achieved by shielding geometry improvements for low energy photon spectrometer, is presented. Continuum counting rate for 13 % relative-efficiency Ge(Li) detector decreased from 4.9 c/min keV at 120 keV to less than 0.1 c/min keV at 900 keV in a 50 mm lead shield.

Optimized background reduction in low-level gamma-ray spectrometry at a surface laboratory

Applied Radiation and Isotopes, 2006

The background of a coaxial Ge detector placed at a surface laboratory has been reduced by means of a background reduction setup consisting of a passive shield of low-activity lead, a simple radon suppression system and an active shield with a plastic scintillation plate. In particular, we have devoted our efforts to in-depth optimization of each parameter associated with different anticoincidence setups and to their subsequent intercomparison. The overall performance of the active shield was improved by using the optimum time parameters for each setup. The final objective is to decrease the cosmic-ray background and, by this way, to reduce the detection limits of gamma-ray spectrometers at conventional laboratories, and consequently make them competitive for different measurements like 210 Pb dating. r

Low-level gamma-ray spectrometry using Ge-detectors

Metrologia, 2007

The technological advances that have taken place during the past 45 years in the fabrication of high purity germanium crystals have had a significant impact on low-level gamma-ray spectrometry. Today, Ge-detectors with high purity Ge-crystals of 2 kg are readily available and detectors with crystals up to 5 kg can be produced. Use of large area crystals results in high detection efficiencies, which can serve to reduce detection limits or to make faster measurements of low activity samples possible. The second major development that has contributed to lowering detection limits has been research on identifying and reducing the background components in gamma-ray spectrometry systems. This paper deals with the major technical factors affecting the performance of low-background HPGe-detectors and provides an overview of the major areas of application.

Performance of an intrinsic germanium three-crystal ultralow background gamma-ray spectrometer

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1988

A-y-ray spectrometer with three large HpGe crystals totalling 560 cm3 in one cryostat was fabricated with a view to achieving ultralow background count rates in the energy region below 4 MeV. At 2 MeV, the continuum background is 1.7 x 10-3 counts per keV per 1000 h per cm3, making this one of the lowest background, large systems at the present time. Only passive shielding is used. Residual activities intrinsic to the detector and shielding materials have been identified with respect to their origin from fission and cosmogenic sources.

Spectroscopic performance evaluation and modeling of a low background HPGe detector using GEANT4

arXiv (Cornell University), 2023

Low background gamma spectrometry employing HPGe detectors is a sensitive technique for measuring low-level radioactivity in environmental applications, material screening, and for rare decay searches. This work presents spectroscopic performance evaluation and modelling of a low background measurement setup developed at IIT Ropar in Punjab, India, to measure trace natural radioactive elements, with a particular interest in studying low-level radioactivity in soil and/or rock samples to generate specific inputs for low background experiments. The performance test and characterization of a low background cryocooled HPGe detector with relative efficiency of ∼33% have been carried out. An effective detector model has been developed using GEANT4 Monte Carlo simulation to determine the response of the detector over an energy range of 80.9-1408 keV and compared with the experimental performance of the detector. The response of the detector obtained using Monte Carlo simulations agrees reasonably well within 93% level of confidence, indicating only 7% deviation in the comparison. The present setup offers improved detection limits of primordial radionuclides (U/Th and K) to measure radioactive contamination in environmental matrices, which has been used elsewhere [1].

Characterization of 30 ^{76}$$Ge enriched Broad Energy Ge detectors for GERDA Phase II

The European Physical Journal C, 2019

The GERmanium Detector Array (Gerda) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double-beta decay of$$^{76}$$76Ge into$$^{76}$$76Se+2e$$^-$$-.Gerdahas been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new76Ge enriched detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in theHadesunderground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input forGerdaPhase II data collection and analyses, but also allowed to study detector phenomen...

Isotopically modified Ge detectors for GERDA: from production to operation

Journal of Instrumentation, 2013

The GERDA experiment searches for the neutrinoless double beta (0νβ β) decay of 76 Ge using high-purity germanium detectors made of material enriched in 76 Ge. For Phase II of the experiment a sensitivity for the half life T 0ν 1/2 ∼ 2 • 10 26 yr is envisioned. Modified Broad Energy Germanium detectors (BEGe) with thick n + electrodes provide the capability to efficiently identify and reject background events, while keeping a large acceptance for the 0νβ β-decay signal through novel pulse-shape discrimination (PSD) techniques. The viability of producing thickwindow BEGe-type detectors for the GERDA experiment is demonstrated by testing all the production steps from the procurement of isotopically modified germanium up to working BEGe detectors. Comprehensive testing of the spectroscopic as well as PSD performance of the GERDA Phase II prototype BEGe detectors proved that the properties of these detectors are identical to those produced previously from natural germanium material following the standard production line of the manufacturer. Furthermore, the production of BEGe detectors from a limited amount of isotopically modified germanium served to optimize the production, in order to maximize the overall detector mass yield. The results of this test campaign provided direct input for the subsequent production of the enriched germanium detectors.

A comprehensive calibration method of Ge detectors for low-level gamma-spectrometry measurements

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2002

This paper aims to show a general and simple method for gamma-ray efficiency calibration in the 186-1500 keV energy range with special attention to applications on environmental studies. This method accounts for differences in densities, composition and counting geometries between real and calibration samples. Self-absorption corrections can be easily determined from a single spectral measurement knowing only the apparent densities of the samples. We have evaluated the influence of background parameters in the response of the spectrometric system and moreover, we have calculated the minimum detectable activity due to background contribution. This calibration has been validated through three different and independent tests. r

LArGe R&D for active background suppression in Gerda

Journal of Physics: Conference Series, 2012

LArGe is a Gerda low-background test facility to study novel background suppression methods in a low-background environment, for future application in the Gerda experiment. Similar to Gerda, LArGe operates bare germanium detectors submersed into liquid argon (1 m 3 , 1.4 tons), which in addition is instrumented with photomultipliers to detect argon scintillation light. The light is used in anti-coincidence with the germanium detectors to effectively suppress background events that deposit energy in the liquid argon. The background suppression efficiency was studied in combination with a pulse shape discrimination (PSD) technique using a BEGe detector for various sources, which represent characteristic backgrounds to Gerda. Suppression factors of a few times 10 3 have been achieved. First background data of LArGe with a coaxial HPGe detector (without PSD) yield a background index of the order 10 −2 cts/(keV•kg•y), which is at the level of the Gerda phase I design goal. As a consequence of these results, the development of an active liquid argon veto in Gerda is pursued.