Search

As a result of the p-type point contact germanium detectors' ability to produce kg-scale radiation sensors with sub- k e V ee (electron equivalent energy) sensitivity, they have been preferred for light dark matter WIMP searches and the study of low energy neutrino physics. These detectors display anomalous behavior to events placed at the surface layer. The spectral shape and ratio methods are utilized to separate the bulk–surface events. The spectral shape technique relies on spectral shape assumptions and the use of external calibration sources to discriminate bulk–surface events. Whereas in ratio method to distinguish between bulk–surface events by employing ratios between several in situ event sample types as calibration sources. Here in this article we will present the comparison study of the two improved methods to separate the bulk–surface events. The bulk–surface separation results for both techniques are found to be comparable, but the main advantage of the ratio technique is its ability to calibrate systems using on-site data; this property makes it easier to collect long-term data and conduct large-scale multidetector research by reducing or eliminating the need for external γ -ray sources for calibration. [ABSTRACT FROM AUTHOR]

A software package for INAA (Instrumental Neutron Activation Analysis), developed at the Nuclear Metrology Laboratory of the IPEN-CNEN/SP, called k0-IPEN, is described. The package consists of a main program linked to nine subprograms designed to perform automatically most of the tasks necessary in order to obtain the mass fractions of the irradiated samples. External efficiency curves calculated by the Monte Carlo code MCNP6 can be read to extend the calibration curve to source to detector distances where only a few experimental points are available. Covariance analysis was used in all steps of the calculation. The validation of the code was tested in an intercomparison sponsored by the IAEA. [ABSTRACT FROM AUTHOR]

In order to establish the variation between results in mass fractions due to software implementation, as measured by the k0-method for INAA, the IAEA has organized a software intercomparison. A complete set of test spectra and associated information was assembled. Efficiency curves, neutron spectrum parameters, correction factors and mass fractions were calculated with the participating programs (k0-IPEN, k0-INRIM, k0-DALAT, k0-IAEA and KayWin) using identical peak areas. In this paper, we report on the observed discrepancies, causes, remedies and future software developments. The test data, as well as intermediate results and observed mass fractions of the certified reference material BCR-320R "channel sediment" are available through the IAEA on request. The variations in concentrations attributed to differences between the programs were initially found to be 5.6 and 7.9%, for certified and uncertified concentrations, respectively. After the certified concentrations had been made available to the participants and they had been allowed to improve their programs, the variations found were 2.7 and 3.4%, respectively. The main identified remaining causes of variation are differences in the procedures used for detector efficiency characterisation and neutron spectrum parameter determination. [ABSTRACT FROM AUTHOR]

We explore the possibility to use advanced germanium (Ge) detectors as a low-energy solar neutrino observatory by means of neutrino-nucleus elastic scattering. A Ge detector utilizing internal charge amplification for the charge carriers created by the ionization of impurities is a novel technology with experimental sensitivity for detecting low-energy solar neutrinos. Ge internal charge amplification (GeICA) detectors will amplify the charge carriers induced by neutrino interacting with Ge atoms through the emission of phonons. It is those phonons that will create charge carriers through the ionization of impurities to achieve an extremely low energy threshold of ∼0.01 eV. We demonstrate the phonon absorption, excitation, and ionization probability of impurities in a Ge detector with impurity levels of 3 × 1010 cm−3, 9 × 1010 cm−3, and 2 × 1011 cm−3. We present the sensitivity of such a Ge experiment for detecting solar neutrinos in the low-energy region. We show that, if GeICA technology becomes available, then a new opportunity arises to observe pp and 7Be solar neutrinos. Such a novel detector with only 1 kg of high-purity Ge will give ∼10 events per year for pp neutrinos and ∼5 events per year for 7Be neutrinos with a detection energy threshold of 0.01 eV. [ABSTRACT FROM AUTHOR]

High Purity germanium point-contact detectors have low energy thresholds and excellent energy resolution over a wide energy range, and are thus widely used in nuclear and particle physics. In rare event searches, such as neutrinoless double beta decay, the point-contact geometry is of particular importance since it allows for pulse-shape discrimination, and therefore for a significant background reduction. In this paper we investigate the pulse-shape discrimination performance of ultra-high purity germanium point contact detectors. It is demonstrated that a minimal net impurity concentration is required to meet the pulse-shape performance requirements.

In this paper we perform a critical analysis of the Orch OR consciousness theory at the crossroad with the newest experimental results coming from the search for spontaneous radiation predicted by the simplest version of gravity-related dynamical collapse models. We conclude that Orch OR theory, when based on the simplest version of gravity-related dynamical collapse, is highly implausible in all the cases analyzed. We discuss the implications of our findings, the limitations, and future plans toward the development of more realistic gravity-related collapse models. • In our article entitled "At the crossroad of the search for spontaneous radiation and the Orch OR consciousness theory", we present for the first time a critical analysis of the Orch OR consciousness theory, at the crossroad with the newest experimental results coming from the search for spontaneous radiation predicted by (the simplest version of) gravity-related dynamical collapse models. • Our article is strongly connected to that published in 2014 by Stuart Hameroff and by Roger Penrose, entitled "Consciousness in the universe: A review of the 'Orch OR 'theory", Volume 11, Issue 1, March 2014, Pages 39-78. • Based on a novel intertwined theoretical and experimental approach, we examined one of the pillars of the Orch OR model, namely the gravity-related collapse model. In this context, we examined the Orch OR calculations using the gravity-related (called Diosi-Penrose, DP, for reasons we explain in the article) theory along with recent experimental constraints on the DP cutoff parameter (R0). We showed that, in this context, the Orch OR based on the DP theory is definitively ruled out for the case of atomic nuclei level of separation, without needing to consider the impact of environmental decoherence; we also showed that the case of partial separation requires the brain to maintain coherent superpositions of tubulin of such mass, duration, and size that vastly exceed any of the coherent superposition states that have been achieved with state-of-the-art optomechanics and macromolecular interference experiments. We conclude that none of the scenarios we discuss (with possible exception to the case of partial separation of tubulins) are plausible. • The implications of our findings, towards future developments of more realistic gravity-related collapse models, including dissipation and/or non-Markovianity, that may leave the door open for Orch Or theory, are also discussed. • Based on the strong connection with previous published papers on this topic, and on the importance of these studies for the Physics of Life, we kindly ask you to consider the publication of our original article in Physics of Life Reviews. [ABSTRACT FROM AUTHOR]

There is concern that work scenarios on the tantalite mining sites in Oke-Ogun, Oyo State, Nigeria may cause occupational radiation exposure of workers due to enhanced concentrations of naturally occurring radionuclides in some process materials. A prior radiological assessment of the mining activities was carried out to determine if and which exposure scenarios may require radiation protection measures. Samples of the materials involved, comprising tantalite (tantalum ores), soil and waste rock were collected and analyzed for activity concentrations of 40K, 226Ra, 238U and 232Th using a hyper pure germanium detector gamma-ray spectrometer. Radon concentrations in the mines were also measured using a continuous radon monitor - Radon-Scout Plus (Sarad, GmbH). Activity concentrations of 40K are below 10 Bqg-1 in all the samples but all the tantalite samples contain more than 1 Bqg-1 of 226Ra and 238U. Hence tantalite is regarded as naturally occurring radioactive material (NORM) and the mining activity as a practice. The requirements for planned exposure situations apply to all the mining sites but, on the basis of graded approach, the optimum radiation protection measures vary from one mine to another, ranging from exemption to authorization. Exposures to radon in the underground mines pose the greatest radiological risks and portend the greatest need for regulatory control in the mining operations. The results further underscore the need to integrate radiation protection with the other health and safety measures in the mining sector. [ABSTRACT FROM AUTHOR]

The MAJORANA Collaboration is searching for the neutrinoless double-beta decay of the nucleus 76Ge. The MAJORANA DEMONSTRATOR is an array of germanium detectors deployed with the aim of implementing background reduction techniques suitable for a 1-ton 76Ge-based search. The ultra low-background conditions require regular calibrations to verify proper function of the detectors. Radioactive line sources can be deployed around the cryostats containing the detectors for regular energy calibrations. When measuring in low-background mode, these line sources have to be stored outside the shielding so they do not contribute to the background. The deployment and the retraction of the source are designed to be controlled by the data acquisition system and do not require any direct human interaction. In this paper, we detail the design requirements and implementation of the calibration apparatus, which provides the event rates needed to define the pulse-shape cuts and energy calibration used in the final analysis as well as data that can be compared to simulations.

An investigation into the irradiation of zirconium alloys with protons was carried out with respect to the capability for simulation of neutron damage as well as the associated activity which would accompany any suggested irradiation programme.Irradiations at 1, 3, 9 and 20 MeV were used to verify an activity modelling program which was found to be accurate in predicting the most active isotopes of Niobium from Zr(p,n)Nb direct reactions with zirconium but was less successful in replicating the relative gamma intensities of spectra recorded by a germanium detector of samples following irradiation. [ABSTRACT FROM AUTHOR]

The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, modular, HPGe detector array with a mass of 44-kg (29 kg 76Ge and 15 kg natGe) to search for neutrinoless double beta decay in 76Ge. The next generation of tonne-scale Ge-based neutrinoless double beta decay searches will probe the neutrino mass scale in the inverted-hierarchy region. The MAJORANA DEMONSTRATOR is envisioned to demonstrate a path forward to achieve a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value of 2039 keV. The MAJORANA DEMONSTRATOR follows a modular implementation to be easily scalable to the next generation experiment. First, the prototype module was assembled; it has been continuously taking data from July 2014 to June 2015. Second, Module 1 with more than half of the total enriched detectors and some natural detectors has been assembled and it is being commissioned. Finally, the assembly of Module 2, which will complete MAJORANA DEMONSTRATOR, is already in progress.

The Majorana Collaboration is building the Majorana Demonstrator, a 60 kg array of high purity germanium detectors housed in an ultra-low background shield at the Sanford Underground Laboratory in Lead, SD. The Majorana Demonstrator will search for neutrinoless double-beta decay of 76Ge while demonstrating the feasibility of a tonne-scale experiment. It may also carry out a dark matter search in the 110 GeV/c2 mass range. We have found that customized Broad Energy Germanium (BEGe) detectors produced by Canberra have several desirable features for a neutrinoless double-beta decay experiment, including low electronic noise, excellent pulse shape analysis capabilities, and simple fabrication. We have deployed a customized BEGe, the Majorana Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and shield at the Kimballton Underground Research Facility in Virginia. This paper will focus on the detector characteristics and measurements that can be performed with such a radiation detector in a low-background environment. © 2010 Elsevier B.V.

In the global landscape of neutrinoless double beta (0νββ) decay search, the use of semiconductor germanium detectors provides many advantages. The excellent energy resolution, the negligible intrinsic radioactive contamination, the possibility of enriching the crystals up to 88% in the 76Ge isotope as well as the high detection efficiency, are all key ingredients for highly sensitive 0νββ decay search. The Majorana and Gerda experiments successfully implemented the use of germanium (Ge) semiconductor detectors, reaching an energy resolution of 2.53 ± 0.08 keV at the Qββ and an unprecedented low background level of 5.2×10−4 cts/(keV·kg·yr), respectively. In this paper, we will review the path of 0νββ decay search with Ge detectors from the original idea of E. Fiorini et al. in 1967, to the final recent results of the Gerda experiment setting a limit on the half-life of 76Ge 0νββ decay at T1/2>1.8×1026 yr (90% C.L.). We will then present the LEGEND project designed to reach a sensitivity to the half-life up to 1028 yr and beyond, opening the way to the exploration of the normal ordering region.

Purpose: The concrete vault, cyclotron body, and peripheral equipment in a cyclotron room become radioactivated by neutrons generated by operating an unshielded cyclotron. Radionuclides and the amounts of radioactivated materials must be identified before discarding a cyclotron system. The present study aimed to reduce the amounts of concrete from cyclotron vaults, as well as cyclotron components and peripheral equipment, that will be disposed of as radioactivated waste by clarifying the nature and quantity of radioactivated materials remaining in facilities after cyclotron operations have ceased. Methods: Cylindrical concrete cores were bored into all four walls, ceiling, and floor of a room where a Cypris 370 cyclotron had been operated for 22.8 yr and then cooled for 40 months. The accelerated particles comprised protons and deuterons with constant energy of 18 and 10 MeV, respectively. The types and amounts of radionuclides in these cores, in 38 components of the cyclotron including the yoke, and in 13 pieces of equipment in the room, were determined by γ‐ray spectrometry. Concentrations of radioactivity were also calculated using an updated version of Particle and Heavy Ion Transport System and DCHAIN‐SP. Amounts of materials with both measured and calculated total radioactivity concentration (ΣD) of <0.1 Bq/g were identified as being nonradioactivated. Results: The major radionuclides in the concrete were 60Co and 152Eu. The radioactivated concrete was distributed to a depth of <38 cm. Most cyclotron components and equipment were radioactivated by neutrons. The major radionuclides in cyclotron components and equipment were 54Mn, 60Co, and 65Zn. A 33% volume of the yoke was regarded as nonradioactivated. Conclusions: The estimated amount of radioactivated waste in the concrete was about 70,000 kg (12.5% of the total concrete). Most components of the cyclotron except for the 33% volume of the yoke (20% of the cyclotron body), as well as most peripheral equipment in the room, were radioactivated. Part‐by‐part assessments of radioactive materials using measurements and calculations could distinguish nonradioactive from radioactive materials before they are discarded. [ABSTRACT FROM AUTHOR]

Abstract High Purity germanium point-contact detectors have low energy thresholds and excellent energy resolution over a wide energy range, and are thus widely used in nuclear and particle physics. In rare event searches, such as neutrinoless double beta decay, the point-contact geometry is of particular importance since it allows for pulse-shape discrimination, and therefore for a significant background reduction. In this paper we investigate the pulse-shape discrimination performance of ultra-high purity germanium point contact detectors. It is demonstrated that a minimal net impurity concentration is required to meet the pulse-shape performance requirements. [ABSTRACT FROM AUTHOR]

In this work, we have focused on results of measurements of the hydrogen line 2223 keV and compared them with the results of Geant4 simulations. The paraffin containing hydrogen was irradiated by neutrons produced by the weak AmBe source. Produced gammas were measured with the germanium detector. The experimental setup was placed inside a carbon chamber which provided the shielding from the external neutrons. The measurements were performed for different amounts of paraffin. The processes playing a role in the description of our measurements are transport and moderation of neutrons, production of gamma rays in neutron-hydrogen interactions, transport and detection of gamma rays. It has been shown that the correctly carried out Monte Carlo simulations reproduced the measured values of the intensity of the observed gamma line 2223 keV from the neutron capture on hydrogen. The absorption of gamma rays is also described correctly. This has been shown in comparing the measurements of gamma line 322 keV from 2 0 6 Pb with the simulations. [ABSTRACT FROM AUTHOR]

Highlights • 235U enrichment estimation investigated by ISOCS™ and MGAU software. • Uranium enrichment and mass can be calculated from the activity calculated by ISOCS™. • Measuring time added an error of statistical nature and affects the estimated precision. • MGAU software can be used directly, but it needs a relatively long time of measurement. • Uncertainty in estimated enrichment for the ISOCS™ method was less than MGAU-based method. Abstract Carry out independent measurements is requisite during nuclear safeguards inspection activities, at nuclear facilities and location outside facility (LOFs), to consider operators' declaration. 235U enrichment value estimation is a significant activity in nuclear material accounting and accountancy. The shortage of standard radioactive sources suitable to γ-ray detectors calibration for field measurements lets to use analysis methods for detectors calibration. Our work gives an overview of uranium enrichment estimation using two different analysis methods. A set of Standard Nuclear Material (SNM) samples, with cylindrical shapes and different enrichment percentage, was used to perform the experimental measurements. Count rate due to the most prominent γ-ray signatures for 235U and 238U isotopes was measured using germanium detector. The isotopic masses calculated based on the activity value estimated for 235U and 238U isotopes by ISOCS™ software efficiency calibration. Also, MGAU software was used to estimate the isotopic fractions of uranium. 235U enrichment value for each sample was calculated using the two analysis methods. The results obtained using different enrichment analysis methods were compared with each other and with the certified value for each sample. [ABSTRACT FROM AUTHOR]

Gamma logging for uranium exploration are currently based on total counting with Geiger Müller gas detectors or NaI (TI) scintillators. However, the total count rate interpretation in terms of uranium concentration may be impaired in case of roll fronts, when the radioactive equilibrium of the natural 238U radioactive chain is modified by differential leaching of uranium and its daughter radioisotopes of thorium, radium, radon, etc. Indeed, in case of secular equilibrium, more than 95 % of gamma rays emitted by uranium ores come from 214Pb and 214Bi isotopes, which are in the back-end of 238U chain. Consequently, these last might produce an intense gamma signal even when uranium is not present, or with a much smaller activity, in the ore. Therefore, gamma spectroscopy measurements of core samples are performed in surface with high-resolution hyper-pure germanium HPGe detectors to directly characterize uranium activity from the 1001 keV gamma ray of 234mPa, which is in the beginning of 238U chain. However, due to the low intensity of this gamma ray, i.e. 0.84 %, acquisitions of several hours are needed. In view to characterize uranium concentration within a few minutes, we propose here a method using both the 92 keV gamma ray of 234Th and the 98.4 keV uranium X-ray. This last is due to uranium self-induced fluorescence caused by gamma radiations of 214Pb and 214Bi, which create a significant Compton scattering continuum acting as a fluorescence source and resulting in the emission of uranium fluorescence X-rays. The comparison of the uranium activity obtained with the 92 keV and 98.4 keV lines allows detecting a uranium heterogeneity in the ore. Indeed, in case of uranium nugget, the 92 keV line leads to underestimated uranium concentration due to gamma self-absorption, but on the contrary the 98.4 keV line leads to an overestimation because of increased fluorescence. In order to test this new approach, several tens of uranium ore samples have been measured with a handheld HPGe FALCON 5000 detector.

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration evaluation by means of gamma-ray measurements. This paper reports gamma-ray spectra, recorded with two high-purity germanium detectors, on standard cement blocks with increasing uranium content, and the corresponding MCNP simulations. The detailed MCNP model of detectors and experimental setup has been validated by calculation versus experiment comparisons. An optimization of detector MCNP models is presented in this paper, as well as a comparison of different nuclear data libraries to explain missing or exceeding peaks in the simulation. Energy shifts observed between the fluorescence X-rays produced by MCNP and atomic data are also investigated, as well as gamma backscattering and beta radiation effects. The validated numerical models will be used in further studies to develop new gamma-ray spectroscopy approaches aiming at reducing acquisition times, especially for ore samples with low uranium content. [ABSTRACT FROM AUTHOR]

Empirical calibrations of full-energy peak and total efficiency curves for well-type and coaxial p-type germanium detectors were carried out using several combinations of practical nuclides. As a result, reliable efficiency functions of both types of detectors were successfully obtained using a home-made program coded with Visual Basic for Applications (VBA) and the “Solver” add-in in Excel™. We also examined the applicability of our advanced program to volumetric sources using squared-to-linear curve technique. [ABSTRACT FROM AUTHOR]

The Majorana Collaboration is searching for the neutrinoless double-beta decay of the nucleus 76 Ge. The Majorana Demonstrator is an array of germanium detectors deployed with the aim of implementing background reduction techniques suitable for a 1-ton 76 Ge-based search. The ultra low-background conditions require regular calibrations to verify proper function of the detectors. Radioactive line sources can be deployed around the cryostats containing the detectors for regular energy calibrations. When measuring in low-background mode, these line sources have to be stored outside the shielding so they do not contribute to the background. The deployment and the retraction of the source are designed to be controlled by the data acquisition system and do not require any direct human interaction. In this paper, we detail the design requirements and implementation of the calibration apparatus, which provides the event rates needed to define the pulse-shape cuts and energy calibration used in the final analysis as well as data that can be compared to simulations. [ABSTRACT FROM AUTHOR]

When calibrating absolute peak efficiency and total efficiency functions for high efficient germanium detectors, single gamma-emitting nuclides are used in general to avoid coincidence summing effects. As another approach, Blaauw developed calibration technique using multiple gamma-emitting nuclides with least-square technique ( Blaauw, 1993; Blaauw and Gelsema, 2003 ). In the present study, we tried to calibrate efficiency functions of a well-type germanium detector based on Blaauw's approach using a home-made iteration calculation algorithm with the “Solver” add-in in Excel™. [ABSTRACT FROM AUTHOR]