GERDA: a Germanium Detector Array to Search for Neutrinoless Double Beta Decay

The GERDA, a new experiment to search for the double beta decay of 76 Ge, is being installed at Laboratori Nazionali del Gran Sasso. The potentialities of this experiment as well as the status of the project are reviewed.JRC.D.4-Isotope measurement

DONA Detector: Further Improvements and Evaluation for Field Applications

The DONA neutron spectrometer concept is based on the measurement of neutron induced activity in a series of small metal disks that have been exposed to a neutron field. The induced activity is measured and the neutron spectrum is calculated using and unfolding technique, based on environmental neutron spectra. The novelty of the approach lies in the concept as such, including usage of carefully selected metal disks arranged in a holder, high performance gamma-ray spectrometry and spectrum unfolding using a library of environmental neutron spectra. This report covers the IRMM exploratory research prolongation project for 2006 and now environmental neutron fields with considerably lower neutron fluence rates are used. The result shows that after further refinement of the detector device and the data evaluation program the detector can very well be used for environmental neutron fluence measurements. Tests were done at PTB, Germany, using their calibrated neutron source and at the MOX fuel fabrication plant Belgonuclearire in Mol, Belgium.JRC.D.4-Isotope measurement

The Effect of Uncertainties in Nuclear Decay Data on Coincidence Summing Calculations for Gamma-Ray Spectrometry

All nuclear decay data have uncertainties. It is not obvious how these uncertainties affect the detection efficiencies in gamma-ray spectrometry performed with HPGe detectors and in close geometry with cascading gamma-rays. This paper presents examples based on Monte Carlo simulations. It shows that for certain cases the uncertainty in the detection efficiency can be significantly greater than the uncertainty of the nuclear decay. This should thus be taken into account when performing a complete uncertainty budget for close geometry measurements.JRC.D.4-Isotope measurement

The 76Ge Double-Beta Decay Experiment GERDA at LNGS

In the second generation 76Ge double-beta decay experiment GERDA bare detectors made out of enriched 76Ge will be operated in an cryogenic fluid shield. The goal of the approved GERDA project is to reduce the background around Q = 2039 keV below 10-3 counts/(kg keVy) and reach a sensitivity for neutrinoless __ decay of T1/2 > 2 × 1026 years after an exposure of 100 kg years.JRC.D.4-Isotope measurement

Measurements of MeV Particles from JET Fusion Plasmas based on the Activation Technique

Measurements of sample activation by nuclear reaction from MeV particles in the JET tokamak are reported. The samples are used as flux monitors for fusion plasma particles in the MeV energy range. Activation products generated by MeV neutrons, protons and deuterons were found and two nuclear reactions possibly due to alpha particles were registered, though at a level close to the detection limit.JRC.D.4-Isotope measurement

Underground Gamma-Ray Spectrometry

Gamma-ray spectromety using high purity Ge detectors has made significant advances in recent years because large crystals have become readily available and the importance of very radiopure materials in the construction of dectectors has been understood. The combination of these improvements has made it possible to decrease detection limits in special low background counting systems. Gamma-ray Spectrometry systems located underground are particularly improved by the new developments. This paper deals with the current state-of-the art of underground gamma-ray spectrometry as well as providing examples of new applications of underground gamma-ray spectrometry that were made possible due to the advances in detectors and technique.JRC.D.4-Isotope measurement

The Effect of Uncertainties in Nuclear Decay Data on Coincidence Summing Calculations for Gamma-Ray Spectrometry

All nuclear decay data have uncertainties. It is not obvious how these uncertainties affect the detection efficiencies in gamma-ray spectrometry performed with HPGe detectors and in close geometry with cascading gamma-rays. This paper presents examples based on Monte Carlo simulations. It shows that for certain cases the uncertainty in the detection efficiency can be significantly greater than the uncertainty of the nuclear decay. This should thus be taken into account when performing a complete uncertainty budget for close geometry measurements.JRC.G.8-Nuclear safeguard

The Sandwich Spectrometer for Ultra Low-level Gamma-ray Spectrometry

A new type of ultra low-background gamma-ray spectrometer has been installed in the underground laboratory HADES in Belgium located at a depth of 500 m water equivalent. The spectrometer is composed of two coaxial HPGe-detectors of about 1.9 kg each. The lower detector has the typical U-shaped arm while the top detector's arm is inverted to make the two detectors' windows face each other. The solid angle is effectively doubled for small samples and close to 3.2p. The muon fluence rate in HADES is 0.09 s-1m-2, which is about 5000 times lower than at the surface (40 m above sea level). The detailed muon spectrum is measured with an active muon shield comprising two plastic scintillators stacked on top of the lead shield. The plastic scintillators are 2.5 cm thick and with an area of 0.8×0.8 m2. The scintillators are connected in coincidence to exclude environmental gamma- and X-rays. All data is stored in list mode, which is suitable for offline analysis of time-interval distributions, coincidences and subsequent background reduction. A completely new type of lead shield is used around the HPGe-detectors. The outer part of the shield is made of 145 mm low-background lead (20 Bq/kg) while the inner 40 mm is made of ultra low-background lead (2.5 Bq/kg), which in turn is lined on the inside with 35 mm of electrolytic copper. The complete detector shield can be opened in two halves by using a motor. This shield design ensures easy and fast access to change samples, clean the detectors and remove/replace HPGe-detectors. This paper describes the technical details of the sandwich detector system, its performance, the most suitable applications and the achieved background reduction. By using data from the active muon shield the background is reduced and it will also be possible identify certain decay chains by studying coincidences and/or time intervals between pulses of different detectors and identify individual events.JRC.D.4-Isotope measurement

On the Use of Mercury as a Means of Locating Background Sources in Ultra Low Background HPGe-Detector Systems

In low-level gamma-ray spectrometry, it is common to measure large samples in order to obtain low detection limits for the massic activity (in mBq/kg). These samples have significant shielding effects. In order to study whether the background sources in three ultra low background HPGe detectors were located in the detector or in the shield, Marinelli beakers filled with hyperpure mercury were measured. Although the measurements were hampered by the presence of cosmogenically produced 194Hg, information regarding the major background location of 40K, 60Co, 137Cs, 210Pb, 226Ra, 228Ra and 228Th could be obtained.JRC.D.4-Isotope measurement

Neutron Field Measurements for Alara Purposes around a Van de Graaff Accelerator Building.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel