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"Oversimplified" and "simplified" methods based on true coincidence summing effect used in uncomplicated determination of the photo-peak efficiency of the semiconductor High Purity Germanium (HPGe) detector system are suggested and verified. The methods and calibrated 60 Co radioactive source may be used to commission any HPGe detector to use during potential criticality event. The determined accuracy of the semiconductor HPGe detector system using this method is a few percent (for the detector system used in this study it was ≃8% for "oversimplified" and ≃5% for "simplified" methods accordingly) reasonable, expected, and good enough to use for estimation of neutron dose from irradiated human blood in a potential criticality event. Moreover, if one can experimentally deduce the photo-peak efficiency for 60 Co 1333 keV γ-ray line using the suggested methods, then with a few percent accuracy this efficiency could be also used for 1369 keV γ-ray line in the decay of 24 Na isotope., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The determination in a sample of the activity concentration of a specific radionuclide by gamma spectrometry needs to know the full energy peak efficiency (FEPE) for the energy of interest. The difficulties related to the experimental calibration make it advisable to have alternative methods for FEPE determination, such as the simulation of the transport of photons in the crystal by the Monte Carlo method, which requires an accurate knowledge of the characteristics and geometry of the detector. The characterization process is mainly carried out by Canberra Industries Inc. using proprietary techniques and methodologies developed by that company. It is a costly procedure (due to shipping and to the cost of the process itself) and for some research laboratories an alternative in situ procedure can be very useful. The main goal of this paper is to find an alternative to this costly characterization process, by establishing a method for optimizing the parameters of characterizing the detector, through a computational procedure which could be reproduced at a standard research lab. This method consists in the determination of the detector geometric parameters by using Monte Carlo simulation in parallel with an optimization process, based on evolutionary algorithms, starting from a set of reference FEPEs determined experimentally or computationally. The proposed method has proven to be effective and simple to implement. It provides a set of characterization parameters which it has been successfully validated for different source-detector geometries, and also for a wide range of environmental samples and certified materials., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Numerical calculations and experimental approaches are used to examine the slip characteristics of 1064 nm laser ablated single crystal germanium. The ablation and cooling processes are used to investigate the influence of laser power density on the creation of the slip process. A 1064 nm continuous laser and a nanosecond laser were used to ablate single-crystal germanium samples, and the damage to the surface was seen using an optical microscope. The results demonstrate that raising the laser power density to 107 W/cm2 efficiently suppresses slip production during laser processing. [ABSTRACT FROM AUTHOR]

This paper presents the effects of background reduction with anticoincidence logical condition between the sum of muon-sensitive large scintillator veto detectors and a germanium detector as well as the time evolution of rejected, muon-induced coincidence gamma spectra. A special attention is paid to neutron effects. The digital event-by-event registration used for data acquisition opens possibilities to study in an off-line mode the variety of effects related to the time structure of all signals registered by detectors. In our laboratory currently we use two such systems with in-house written software Veto for off-line data analysis. [ABSTRACT FROM AUTHOR]

Recently, phase change chalcogenides, such as monochalcogenides, are reported as switching materials for conduction‐bridge‐based memristors. However, the switching mechanism focused on the formation and rupture of an Ag filament during the SET and RESET, neglecting the contributions of the phase change phenomenon and the distribution and re‐distribution of germanium vacancies defects. The different thicknesses of germanium telluride (GeTe)‐based Ag/GeTe/Pt devices are investigated and the effectiveness of phase loops and defect loops future application in neuromorphic computing are explored. GeTe‐based devices with thicknesses of 70, 100, and 200 nm, are fabricated and their electrical characteristics are investigated. Highly reproducible phase change and defect‐based characteristics for a 100 nm‐thick GeTe device are obtained. However, 70 and 200 nm‐thick devices are unfavorable for the reliable memory characteristics. Upon further analysis of the Ag/GeTe/Pt device with 100 nm of GeTe, it is discovered that a state‐of‐the‐art dependency of phase loops and defect loops exists on the starting and stopping voltage sweeps applied on the top Ag electrode. These findings allow for a deeper understanding of the switching mechanism of monochalcogenide‐based conduction‐bridge memristors. [ABSTRACT FROM AUTHOR]

The future Ricochet experiment aims to search for new physics in the electroweak sector by measuring the Coherent Elastic Neutrino-Nucleus Scattering process from reactor antineutrinos with high precision down to the sub-100 eV nuclear recoil energy range. While the Ricochet collaboration is currently building the experimental setup at the reactor site, it is also finalizing the cryogenic detector arrays that will be integrated into the cryostat at the Institut Laue Langevin in early 2024. In this paper, we report on recent progress from the Ge cryogenic detector technology, called the CryoCube. More specifically, we present the first demonstration of a 30 eVee (electron equivalent) baseline ionization resolution (RMS) achieved with an early design of the detector assembly and its dedicated High Electron Mobility Transistor (HEMT) based front-end electronics with a total input capacitance of about 40 pF. This represents an order of magnitude improvement over the best ionization resolutions obtained on similar phonon-and-ionization germanium cryogenic detectors from the EDELWEISS and SuperCDMS dark matter experiments, and a factor of three improvement compared to the first fully-cryogenic HEMT-based preamplifier coupled to a CDMS-II germanium detector with a total input capacitance of 250 pF. Additionally, we discuss the implications of these results in the context of the future Ricochet experiment and its expected background mitigation performance. [ABSTRACT FROM AUTHOR]

In an ideal germanium detector, fully-absorbed monoenergetic γ –rays will appear in the measured spectrum as a narrow peak, broadened into a Gaussian of width determined only by the statistical properties of charge cloud generation and the electronic noise of the readout electronics. Multielectrode detectors complicate this picture. Broadening of the charge clouds as they drift through the detector will lead to charge sharing between neighboring electrodes and, inevitably, low-energy tails on the photopeak spectra. We simulate charge sharing in our germanium cross strip detectors in order to reproduce the low-energy tails due to charge sharing. Our goal is to utilize these simulated spectra to develop an analytical fit (shape function) for the spectral lines that provides a robust and high-quality fit to the spectral profile, reliably reproduces the interaction energy, noise width, and the number of counts in both the true photopeak and the low-energy tail, and minimizes the number of additional parameters. Accurate modeling of the detailed line profiles is crucial for both calibration of the detectors as well as scientific interpretation of measured spectra. [ABSTRACT FROM AUTHOR]

The article investigates the performance of germanium source doping-less tunnel FET (Ge DLTFET)-based digital integrated circuits. For this, the compact models have been developed for DLTFETs using Verilog-A approach. Furthermore, at circuit level, the performance of Ge DLTFET is compared with its conventional counterpart silicon source DLTFET (Si DLTEFT). Two digital benchmark circuits are considered for circuit simulation such as ring oscillator (RO) and conventional six-transistor static random-access memory (6 T SRAM). The simulation results depict that the operating frequency of Ge DLTFET RO is ~ 4.48 decade higher than Si DLTFET. Similarly, the performance of Ge DLTFET SRAM cell in terms of read and write delay is much better than its conventional counterpart Si DLTFET. Hence, Ge DLTFET can be considered as a promising device structure for high-speed digital circuit design and for its applications. [ABSTRACT FROM AUTHOR]

We present a design for silicon-compatible vertical Germanium pin photodiodes structured into all-dielectric metasurfaces. Proof-of-principle metasurfaces are fabricated on silicon-on-insulator wafers in a top-down process. Simulations and measurements of the spectroscopic properties, specifically the absorption, show high spectral selectivity, and absorption efficiencies as large as those in bulk Germanium layers with about four times the Ge layer thicknesses. Our metasurface structures can be tuned to the target wavelength through tailoring of the lateral geometry. Possible applications include spectroscopy and hyperspectral imaging, with several metasurfaces for different wavelength ranges integrated with readout circuitry into a low-cost electronic–photonic integrated circuit. [ABSTRACT FROM AUTHOR]

We collided silicon and germanium laser-induced plumes in helium background gas to clarify the behavior of the plumes after the collision. The expansion of the silicon and germanium species in the mixed plume after the collision was observed separately by spectroscopic measurements and the degree of mixing was evaluated by the experimental results. When the pressure of the background gas was 2000 Pa, the plumes moved backward after the collision with the counter-propagating shock wave, and no mixing of the plumes was observed. The effect of the counter-propagating shock wave was discussed by comparing with the results of numerical calculations based on the compressible Euler equations. At 300 Pa, the plumes concentrated at about 1 mm around the central region just after the collision and almost 100% mixing occurred in this region. The concentration and mixing of the plumes in the central region is a key to forming well-mixed plume. Stagnation and partial mixing of the plumes were observed at intermediate pressures. By decreasing the background helium gas pressure from 2000 to 300 Pa, the degree of mixing increased from 0 to about 100%. The results are compared with those in argon background gas to discuss effects of mean free path. The effects of counter-propagating shock wave, mean free path and the onset time of the collision on the backward movement and mixing of the plumes are discussed. [ABSTRACT FROM AUTHOR]

• Plasma evolution of laser-induced damage of Ge is monitored in air and vacuum. • The dependence between damage morphology and scattering light is analysed. • Plasma shield effect and thermal ablation are main damage mechanism in the air. • Plasma shock wave and thermo-mechanical stress dominate damage process in the vacuum. Laser-induced damage of germanium (Ge) sheets plays a key role to explore the laser irradiation effect with the development of high-power laser and precision machining technology. However, the impact of plasma evolution on the damage mechanism is still a lack of detailed analysis for Ge sheet. Here, we investigate the change of the morphology and size of the plasma plume and compare it with the damage morphology of Ge sheets versus the laser pulse number in air and vacuum conditions. The plasma plume area reveals a gradual increase and then a slow decrease trend in the air and the final damage morphology is a shallow concavity. Instead, it reveals a fast rise and fall trend in the vacuum and the final morphology is a complete breakdown pit. The damage process of Ge sheet is divided into the initial damage, developmental damage, breakdown damage and stable damage according to the morphological changes of scattering light. The plasma shielding effect and thermal ablation play a more important role in formation of the damage morphology in the air, and the plasma shock wave and thermo-mechanical stress dominate the damage morphology in the vacuum. The significant contrasts and the combined experimental and theoretical works provide an insight into the laser irradiation effect and material degradation behavior, hence broaden the potential application of Ge sheets in laser micro/nano-fabrication. [ABSTRACT FROM AUTHOR]

The use of High Purity Germanium detectors operated in ionization mode at cryogenic temperatures is investigated as an external background mitigation solution for bolometers used in rare-event search experiments. A simple experimental setup, running a 52-g Li 2 WO 4 bolometer sandwiched in-between two 2-cm thick High Purity Germanium cylindrical detectors in a dry cryostat, shows promising rejection to environmental gammas and atmospheric muons backgrounds. The acquired data are used together with a Monte Carlo simulation of the setup to extract the main contributions to the external backgrounds expected in an above ground experiment, such as e.g. current and future experimental efforts targeting the detection of coherent elastic neutrino-nucleus scattering at reactor facilities. Based on all these results, a 4 π coverage similar veto system achieving a O (10 keV) energy threshold is expected to achieve a ≳ 73% and a ≳ 92% rejection power for gamma-like and muon-like events, respectively. [ABSTRACT FROM AUTHOR]

The first-generation semiconductor materials represented by silicon (Si) and germanium (Ge) still hold a dominant position in many fields, including micro-electromechanical systems (MEMS) and integrated circuits (ICs). The processing of these materials continues to attract significant research attention for improvements in quality and efficiency. This study proposes a novel hybrid laser-enhanced particle-laden electrochemical machining (LEPL-ECM) process, whereby pulsed laser irradiation is utilized to selectively and locally enhance the electrical conductivity of Ge at specific locations. A neutral electrolyte jet, containing abrasive diamond particles, is applied to the location on the wafer surface opposite the laser irradiation, facilitating a localized and enhanced electrochemical dissolution. The effect of micro-particle erosion effectively removes the generated oxides and potential passivation layers, ensuring continuous and efficient electrochemical reactions. Consequently, high-quality micro-dimples with an entrance diameter of about 380–800 μm, a depth of around 138–300 μm, and a quasi-mirror surface with the roughness (Sa) of as low as 59.8 nm can be achieved within 90 s. Furthermore, the effects of the applied voltage, laser power and processing time on the resulting dimple characteristics and surface quality are discussed, along with a detailed morphology characterization. Dense micro-pits, radial streamlined micro-grooves and a special transitional region have been observed on dimple center, sidewall and near the edge, respectively, and the formation mechanism have been analyzed. Finally, a simulation of the electrolyte jet induced fluid pressure and velocity as well as the particle trajectory and distributions within and surrounding the dimple structure was conducted, which reveals that the synergistic mechanism associated with the hybrid material removal process involves both electrochemical corrosion and abrasive erosion. [Display omitted] • A novel LEPL-ECM method is proposed for high quality micro-dimpling of Ge. • A quasi-mirror dimple surface with the Sa of 59.8 nm can be achieved within 90 s. • Influences of several key processing parameters have been experimentally studied. • Synergistic effects exist between electrochemical corrosion and abrasive erosion. • Distributions of flow velocity, pressure and particle trajectory are calculated. [ABSTRACT FROM AUTHOR]

For precise modeling of a high purity germanium (HPGe) detector, detailed knowledge of its geometry is necessary. Unfortunately, some of the detector geometric parameters are often not available. This study suggests simple procedures for determining geometry without the need for radiography. The study considers the HPGe detector GC0518 manufactured by Mirion. The detector datasheet is available, but the uncertainties do not allow the detector to be modeled without additional corrections. The detector was modeled using MCNP5 code and the results were compared with calibration point sources and Marinelli beakers measurements. We also performed measurements to obtain information on the germanium dead layer, crystal holder shape, inner hole shape and radii of the crystal edges. Then the model was optimized according to the measurements. Finally, the full energy peak efficiencies were evaluated. The relative differences between the measured and calculated efficiencies are less than 4.5% for point sources and 5.4% for Marinelli beakers. [ABSTRACT FROM AUTHOR]

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The new DEspec Germanium Array Spectrometer (DEGAS), used at GSI/FAIR, includes bismuth germanate (BGO) scintillation detectors for active shielding to improve the sensitivity of its high-purity germanium (HPGe) detectors. The BGO detectors have a very high gamma-ray detection efficiency and can suppress background, such as Compton-scattered photons, by operating in an anti-coincidence veto mode with the germanium detectors. The BGO system was characterized and its performance was compared to simple gamma-ray propagation simulations. [ABSTRACT FROM AUTHOR]

Rare event search experiments using germanium detectors are performed in underground laboratories to minimize the background induced by cosmic rays. However, the cosmogenic activation of cupreous detector components on the ground generates long half-life radioisotopes and contributes to the background level. We measured cosmogenic activation with 142.50 kg of copper bricks after 504 days of exposure at an altitude of 2469.4 m outside the China Jinping Underground Laboratory (CJPL). The specific activities of the cosmogenic nuclides produced in the copper bricks were measured using a low-background germanium gamma-ray spectrometer at CJPL. The production rates at sea level, in units of nuclei/kg/day, were 18.6 ± 2.0 for 54 Mn, 9.9 ± 1.3 for 56 Co, 48.3 ± 5.5 for 57 Co, 51.8 ± 2.5 for 58 Co, and 39.7 ± 5.7 for 60 Co. The measurement will help to constrain cosmogenic background estimation for rare event searches using copper as a detector structure and shielding material. Based on the measured production rates, the impact of the cosmogenic background in cupreous components of germanium detectors on the next generation CDEX-100 experiment was assessed with the expected exposure history above ground. [ABSTRACT FROM AUTHOR]

Single-charge pumps are the main candidates for quantum-based standards of the unit ampere because they can generate accurate and quantized electric currents. In order to approach the metrological requirements in terms of both accuracy and speed of operation, in the past decade there has been a focus on semiconductor-based devices. The use of a variety of semiconductor materials enables the universality of charge pump devices to be tested, a highly desirable demonstration for metrology, with GaAs and Si pumps at the forefront of these tests. Here, we show that pumping can be achieved in a yet unexplored semiconductor, i.e. germanium. We realise a single-hole pump with a tunable-barrier quantum dot electrostatically defined at a Ge/SiGe heterostructure interface. We observe quantized current plateaux by driving the system with a single sinusoidal drive up to a frequency of 100 MHz. The operation of the prototype was affected by accidental formation of multiple dots, probably due to disorder potential, and random charge fluctuations. We suggest straightforward refinements of the fabrication process to improve pump characteristics in future experiments. [ABSTRACT FROM AUTHOR]

Investigation of a polished surface of germanium single crystals scanned with a focused beam of pulse-frequency modulated UV radiation of Nd:YAG laser showed evidence of laser-induced surface etching at subthreshold energy densities (E ∼ 0.5–1.15 J/cm2) in the absence of noticeable traces of crater formation. It is suggested that the ablation centers nucleate on dislocations escaping at the surface of germanium crystals. [ABSTRACT FROM AUTHOR]

The Compex detector is an electrically cooled, composite germanium detector that uses four coaxial, cubic-shaped, single-encapsulated germanium crystals. This novel detector allows for new heights in photon detection efficiency in decay spectroscopy setups using box-shaped vacuum chambers. Its spectroscopic performance and detection efficiency is evaluated by means of source measurements. Motivated by Compex's unique cubic germanium crystals, the Lund scanning system has been developed. The constructed system is used to characterise the response as a function of interaction position within a Compex crystal. Sensitivity across the front face, pulse shapes, and rise times have been analysed. Future development and applications of the Compex detector are discussed. [ABSTRACT FROM AUTHOR]

The true coincidence summing correction factor for a Broad Energy Germanium detector has been calculated at far and close geometry set-up using radioactive γ -ray sources. The correction factors were calculated using both experimental and analytical methods. Geant4 simulation was done to calculate the full-energy peak and total efficiencies of the detector. Standard, as well as fabricated mono-energetic γ -ray sources, were used for the γ -ray efficiency measurements. The simulated efficiencies of mono-energetic γ -ray sources were matched to the experimental γ -ray efficiencies by optimizing the detector parameters. The same parameters were used to obtain the full-energy peak and total efficiencies for γ -rays of current interest. Analytical and experimental correction factors were found to agree well with each other. The coincidence summing effect is found to be significant for source-to-detector distances less than 5 cm. • Close geometry measurement for γ -ray detection efficiency. • Coincidence summing correction for BEGe (Broad Energy Germanium) detector. • Geant4 simulation for γ -ray detection efficiency. [ABSTRACT FROM AUTHOR]

LEGEND-200 (Large Enriched Germanium Experiment for Neutrinoless ββ Decay) is a physics experiment at the Gran Sasso National Laboratories (LNGS) in Italy searching for neutrinoless double beta (0υββ) decay of 76Ge using enriched high purity germanium (HPGe) detectors with a total mass of about 200 kg. During the production of germanium crystals, especially during the crystal cutting, a fraction of the enriched germanium remains as metal residues. To reuse these residual materials again for crystal growing, they must be efficiently purified. A special plant was built to purify and convert Ge metal to GeO 2. Quadrupole ICP-MS (Q-ICP-MS) and High Resolution ICP-MS (HR-ICP-MS) were used to characterize the starting materials, reaction and final products. The results of the analyses are presented here. • ICP-MS analysis of germanium samples. • Purification of germanium crystals. • Use of high resolution ICP-MS. • Online check of purification system. [ABSTRACT FROM AUTHOR]

Abstract Future direct searches for low-mass dark matter particles with germanium detectors, such as SuperCDMS SNOLAB, are expected to be limited by backgrounds from radioactive isotopes activated by cosmogenic radiation inside the germanium. There are limited experimental data available to constrain production rates and a large spread of theoretical predictions. We examine the calculation of expected production rates, and analyze data from the second run of the CDMS low ionization threshold experiment (CDMSlite) to estimate the rates for several isotopes. We model the measured CDMSlite spectrum and fit for contributions from tritium and other isotopes. Using the knowledge of the detector history, these results are converted to cosmogenic production rates at sea level. The production rates in atoms/(kg · day) are 74 ± 9 for 3H, 1.5 ± 0.7 for 55Fe, 17 ± 5 for 65Zn, and 30 ± 18 for 68Ge. [ABSTRACT FROM AUTHOR]

A non-destructive gamma-spectrometric method of determining the characteristics of fissile materials in fuel pins with uranium-plutonium fuel is presented. The measurements were performed with the aid of a scanning apparatus with an ultrapure germanium detector. The uniformity of the mass and plutonium distributions was monitored according to the counting rate of the pulses in the 413.7 keV peak of 239Pu. The FRAM code was used to determine the isotopic composition of plutonium in a fuel pin. Multiple repeated measurements were performed and the repeatability and reproducibility of the determinations of the characteristics of the fissile materials in a fuel element were determined. [ABSTRACT FROM AUTHOR]

• ISOCS technique an important and significant tool for IAEA activities verification. • ISOCS technique able to measuring samples with different geometry. • ISOCS technique was used for the germanium detector efficiency calculation. • The detector efficiency has been used as a parameter to estimate 235U mass. • A good agreement was obtained between estimated and declared values. Measurement of nuclear materials by ISOCS technique an important and significant tool for IAEA activities verification. ISOCS technique able to measuring samples with different geometry. In this work, ISOCS technique was used to calculate the absolute efficiency of the Hyper Pure Germanium (HPGe) detector. The calculated absolute efficiency of the detector was used in combination with experimental work to determine U-235 mass in cylindrical NM samples. A good agreement was obtained when compared estimated and declared values of 235U mass content with difference in the ranged from −0.827% to 1.635%. [ABSTRACT FROM AUTHOR]

We present a retrospective on the foundation, evolution, contributions and future prospects of the TEXONO Collaboration and its research programs on neutrino physics and dark matter searches at the Kuo-Sheng Reactor Neutrino Laboratory in Taiwan and, as a founding partner of the CDEX program, at the China Jinping Underground Laboratory in China. aThis retrospective paper is an expansion and update of one that appeared in “The Universe” newsletter of the Asia Pacific Organization for Cosmology and Particle Astrophysics (APCosPA Org).1 [ABSTRACT FROM AUTHOR]

Detector efficiency is a measure of the detectors' ability to detect radiation. It is known that the efficiency values, which are important and affect the activity calculation in germanium detectors, decrease rapidly at low energies. This study focuses on the reasons for this handicap in the low energy region of the efficiency curve. The Monte Carlo simulation was carried out with four setups: germanium only, germanium with a dead layer, germanium with aluminum holders, and finally germanium with a dead layer and aluminum holders. The effect of each setup on the efficiency curve was observed. As a result, it was seen that the main cause of the handicap was the dead layer. For this reason, it was concluded that the current value of the dead layer, which is known to change over time, should be taken into account in detector calibrations or characterizations. • The efficiency of HPGe detectors was questioned by PHITS Monte Carlo code. • The dead layer causes a rapid decrease in efficiency in the low-energy region. • Detector characterization should include a time-varying dead layer. [ABSTRACT FROM AUTHOR]

Recent progress on the development of very low noise high purity germanium ionization spectrometers has produced an instrument of 1.2 kg mass and excellent noise performance. The detector was installed in a low-background cryostat intended for use in a direct detection search for low mass, WIMP dark matter. This transaction reports the thermal characterization of the cryostat, specifications of the newly prepared 1.2 kg p-type point contact germanium detector, and the spectroscopic performance of the integrated system. The integrated detector and low background cryostat achieved full-width-at-half-maximum noise performance of 98 eV for an electronic pulse generator peak and 1.9 keV for the 1332-keV 60Co gamma ray. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to develop a Monte Carlo simulation model for in vivo associated particle neutron elemental imaging (APNEI) and to study the feasibility of using APNEI to determine the iron distribution in a human liver with the defined model. Methods: The model presented in this study was defined in ???? by the basic geometry of the human body, the use of D+D source neutrons, iron as the element of interest, an iron-containing voxel in the liver as the target region, and 2 large germanium detectors anterior and posterior to the trunk of the body. The f 8 pulse height tally was employed in ???? to determine the signal acquired from iron inelastic scatter gamma rays at various iron concentrations in the target liver voxel. Correspondingly, the f 4 average flux tally in ???? was modified by a dose function such that the equivalent dose to the whole liver and the effective dose to the whole body could be estimated and used as the basis for a limiting number of neutron histories which could feasibly allow for the collection of a sufficient volume of data to construct a 2D image of iron distribution in the liver voxel. Results: Assuming an allowable equivalent dose to the liver of 5 mSv, 143 inelastic scatter iron gamma ray counts (at ~847 keV) would ideally be registered at the germanium detectors for a 1 cm³ cube-shaped liver voxel with an iron concentration of 1000 ppm. According to the simulation model, an image of iron distribution in the liver can be constructed with a 1 cm resolution at the level of 1000 ppm iron. Collecting such an image would yield an estimated whole body dose of 0.82 mSv. The mathematical introduction of image uncertainty resulting from source spot diameter and detector timing resolution more closely approximates the result of real world application. Conclusions: APNEI of certain elements in vivo appears feasible given several timing, sensitivity, and resolution caveats. However, further study is required to determine what the detection limit of iron would be and what image resolution would be in an experimental setup as the present model contains idealized assumptions which overestimate the signal attributable to iron inelastic scatter gamma rays. [ABSTRACT FROM AUTHOR]

A compact, low-mass light shield has been designed for the Psyche space mission high-purity germanium gamma-ray spectrometer. The spectrometer will be vented to space, which can allow solar photons to enter the cryostat and cause charge-induced noise. The light shield was designed to block more than 99.9% of solar photons while maintaining high molecular conductance to space vacuum. COMSOL simulations and experiments were performed to characterize light shield photon attenuation and molecular conductance. The light shield was integrated onto the gamma-ray spectrometer and photon suppression and vacuum performance were demonstrated. [ABSTRACT FROM AUTHOR]

The determination in a sample of the activity concentration of a specific radionuclide by gamma spectrometry needs to know the full energy peak efficiency (FEPE) for the energy of interest. The difficulties related to the experimental calibration make it advisable to have alternative methods for FEPE determination, such as the simulation of the transport of photons in the crystal by the Monte Carlo method, which requires an accurate knowledge of the characteristics and geometry of the detector. The characterization process is mainly carried out by Canberra Industries Inc. using proprietary techniques and methodologies developed by that company. It is a costly procedure (due to shipping and to the cost of the process itself) and for some research laboratories an alternative in situ procedure can be very useful. The main goal of this paper is to find an alternative to this costly characterization process, by establishing a method for optimizing the parameters of characterizing the detector, through a computational procedure which could be reproduced at a standard research lab. This method consists in the determination of the detector geometric parameters by using Monte Carlo simulation in parallel with an optimization process, based on evolutionary algorithms, starting from a set of reference FEPEs determined experimentally or computationally. The proposed method has proven to be effective and simple to implement. It provides a set of characterization parameters which it has been successfully validated for different source-detector geometries, and also for a wide range of environmental samples and certified materials. [ABSTRACT FROM AUTHOR]

The segmentation of the electrodes of germanium detectors facilitates gamma-ray imaging and tracking. Replacing the traditional n-type lithium drifted contact is a key to finer segmentation. Amorphous-germanium is a promising alternative contact technology, and large, highly segmented detectors have been fabricated. One factor in adopting any new detector technology is its robustness in hostile environments. Therefore, to explore the effects of neutron damage on position sensitive amorphous-contact germanium gamma-ray detectors and investigate methods for mitigation and repair of damage, two detectors were intentionally exposed to a non-uniform neutron fluence of greater than 4(1) ×10 9 n/cm 2 produced in the 7 Li(p, n) 7 Be reaction at the UMass Lowell Van-de-Graaff accelerator. Post-irradiation tests were made on the counters by varying the electric field, the charge deposition rate, the operating temperature, and utilizing various annealing cycles in order to ascertain the robustness of their performance after irradiation. [ABSTRACT FROM AUTHOR]

We have constructed a pixelated germanium detector using a technique which has been shown to provide good isolation between adjacent pixels. In this work we present initial tests of the application of a low-noise CMOS ASIC to read out this detector. The detector has 64 pixels, each 0.5~\mm\times 5~\mm, arranged as a series of strips. It is connected by wire-bonds to two 32-channel application-specific integrated circuits (ASICs) which provide a complete photon-counting chain for every channel. Since the size of the pixel array is no longer restricted by the difficulties of instrumenting large channel-count conventional electronics, this development will open up the possibility of even larger arrays, similar to those offered by silicon detectors. [ABSTRACT FROM PUBLISHER]

A novel, multi-point contact high-purity germanium detector has been developed for applications in high-rate gamma environments. The planar detector was fabricated with seven point contacts, a high-voltage steering grid and bias electrode using amorphous germanium technology. We have characterized this detector and report herein on the depletion profile, leakage current, energy resolution, and charge-sharing behavior. [ABSTRACT FROM PUBLISHER]

A charge-carrier trap correction technique was developed for orthogonal strip planar germanium gamma-ray detectors. The trap corrector significantly improves the gamma-ray energy resolution of detectors with charge-carrier trapping from crystal-growth defects and radiation damage. Two orthogonal-strip planar germanium detectors were radiation damaged with 2-MeV neutron fluences of ~8x109 n/cm². The radiation-damaged detectors were studied in the 60-80 K temperature range. [ABSTRACT FROM AUTHOR]

The objective of this work is to determine if coherent-elastic-neutrino-nucleus scatter (CE ν NS) in natural germanium detectors can be used to detect antineutrinos from an AP1000-type fission reactor. In this work, we first modeled the AP1000 core using Monte Carlo N-Particle Transport Code 6.2 (MCNP) to estimate the number of fissions from each fissile isotope in the core. Next, the reactor antineutrino spectrum was computed using the summation method for fuel burnup from 10 to 60 GWd/MTU. It was found that with the increasing fuel burnup, as the 239Pu inventory builds-up in the fuel and the 235U inventory depletes, the contributions from 239Pu to fission is enhanced. Thus, the antineutrino energy spectrum begins to skew more towards lower energies as seen by the quantification of third and fourth central moments. Increased fuel burnup also results in greater antineutrino production. The detection setup assumes a 100-kg CE ν NS based natural germanium detector, which is placed outside the reactor containment, 25 m away from the core. The detector has a 100-eV nuclear recoil (NR) threshold and experiences a background level of 100 differential rate units (DRU), per kg.keV.day, due to surrounding radiation interacting in the detector. We then computed the differential pulse height distribution responses for two 235U enrichment cases: 3.3-wt-% and 4.4-wt-% at burnup levels of 10, 20, 40, and 60 GWd/MTU. Overall, the detection rate decreases when the burnup increases. This study indicates that germanium pulse height distribution end-point energies decrease with increasing fuel burnup and become less separable. Thus, we note that the CE ν NS detector resolution would need to be higher for more burned fuel. A 16-eV NR is sufficient for distinguishing fresh fuel from that burned to 20 GWd/MTU. We also investigate the ability to detect a difference between burnups: 10 and 20 GWd/MTU, 10 and 40 GWd/MTU, 10 and 60 GWd/MTU, based on the integral detector counts after accounting for background and detection threshold. We determined that fuel burnup deviations can be detected with confidence much greater than 20%, as required by the IAEA, for low likelihood events. For 3.3-wt-% 235U enrichment, the confidence levels to distinguish burnup between 10 and 20 GWd/MTU, 10 and 40 GWd/MTU, 10 and 60 GWd/MTU are 80.60%, 100%, and 100%, respectively. For 4.4-wt% 235U enrichment, but the same three burnup comparisons, the confidence levels decreased marginally to 65.52%, 100%, and 100%, respectively. [ABSTRACT FROM AUTHOR]

The performance of a new gamma-gamma coincidence spectrometer system for environmental samples analysis at the Center for Nuclear Technologies of the Technical University of Denmark (DTU) is reported. Nutech Coincidence Low Energy Germanium Sandwich (NUCLeGeS) system consists of two HPGe detectors in a surface laboratory with a digital acquisition system used to collect the data in time-stamped list mode with 10 ns time resolution. The spectrometer is used in both anticoincidence and coincidence modes. [ABSTRACT FROM AUTHOR]

In Japan, we conducted proficiency testing of activity measurement by using high-purity germanium detectors for 134 Cs and 137 Cs in brown rice grains. Among 176 reported results, 86 % (for 134 Cs) and 93 % (for 137 Cs) of the results satisfied | E n | ≦ 1. However, 58 reports for 134 Cs and 51 reports for 137 Cs had some failures in their evaluations of uncertainties. The proficiency testing was effective to improve the ability of uncertainty evaluation. [ABSTRACT FROM AUTHOR]

Abstract: We present data characterizing the performance of the first segmented, N-type Ge detector, isotopically enriched to 85% 76Ge. This detector, based on the Ortec PT6×2 design and referred to as SEGA (Segmented, Enriched Germanium Assembly), was developed as a possible prototype for neutrinoless double beta-decay measurements by the Majorana collaboration. We present some of the general characteristics (including bias potential, efficiency, leakage current, and integral cross-talk) for this detector in its temporary cryostat. We also present an analysis of the resolution of the detector, and demonstrate that for all but two segments there is at least one channel that reaches the Majorana resolution goal below 4keV FWHM at 2039keV, and all channels are below 4.5keV FWHM. [Copyright &y& Elsevier]

The SIGMA project aims to develop a p-type segmented inverted coaxial point contact germanium detector for gamma-ray tracking and imaging. The performance of the first prototype of this type of detector is reported. The measurements performed verified the size and shape of the crystal and determined the location of the complex active volumes of the detector segments. The latter determines the charge collection times that are related to the position of interaction. Good agreement is found between the results and the specified crystal design. The energy resolution of the point contact has been measured to be 0.84 keV and 2.21 keV at 122 keV and 1332 keV, respectively. [ABSTRACT FROM AUTHOR]

This paper presents progress on the development of a cryostat intended to improve upon the low-energy threshold (below 0.5 keV) of p-type point contact germanium gamma-ray spectrometers. Ultra-low energy thresholds are important in the detection of low-energy nuclear recoils, an event class relevant to both dark matter direct detection and measurement of coherent neutrino-nucleus scattering. The cryostat design, including a thermal and electrical-field model, is given. A prototype cryostat has been assembled and data acquired to evaluate its vacuum and thermal performance. [ABSTRACT FROM PUBLISHER]

Cross-talk limits of monolithic highly-segmented semiconductor detectors for high-resolution X-gamma spectrometry are investigated. Cross-talk causes false signal components yielding amplitude losses and fold-dependent shifts of the spectral lines, which partially spoil the spectroscopic performance of the detector. Two complementary electrical models are developed, which describe quantitatively the inter-channel cross-talk of monolithic segmented detectors whose electrodes are read out by charge-sensitive preamplifiers. The first is here designated as Cross-Capacitance (CC) model, the second as Split-Charge (SC) model. The CC model builds around the parasitic capacitances Cij linking the preamplifier outputs and the neighbor channel inputs. The SC model builds around the finite-value of the decoupling capacitance C_C used to read out the high-voltage detector electrode. The key parameters of the models are individuated and ideas are shown to minimize their impact. Using a quasi-coaxial germanium segmented detector it is found that the SC cross-talk becomes negligible for decoupling capacitances larger than 1 nF, where instead the CC cross-talk tends to dominate. The residual cross-talk may be reduced by minimization of stray capacitances Cij, through a careful design of the layout of the Printed Circuit Board (PCB) where the input transistors are mounted. Cij can be made as low as \sim5 fF, but it is shown that even in such case the impact of the CC cross-talk on the detector performance is not negligible. Finally, an algorithm for cross-talk correction is presented and elaborated. [ABSTRACT FROM AUTHOR]

Abstract: Four general Monte Carlo codes (GEANT3, PENELOPE, MCNP and EGS4) and five dedicated packages for efficiency determination in gamma-ray spectrometry (ANGLE, DETEFF, GESPECOR, ETNA and EFFTRAN) were checked for equivalence by applying them to the calculation of efficiency transfer (ET) factors for a set of well-defined sample parameters, detector parameters and energies typically encountered in environmental radioactivity measurements. The differences between the results of the different codes never exceeded a few percent and were lower than 2% in the majority of cases. [Copyright &y& Elsevier]

Abstract: We investigate the temperature dependence of p–i–n photodetectors realized in germanium on silicon. The dark current increases by a factor 1.6–1.9 every 10°C and is typically dominated by generation in the space charge region, with diffusion contributing in the best samples. The near infrared (NIR) responsivity decreases with temperature in devices with a large defect-density, but is more stable in high-quality photodiodes. These findings provide a relevant insight on the design of Ge-on-Si NIR detectors to be operated above room temperature. [Copyright &y& Elsevier]

Abstract: We report on near-infrared waveguide photodetectors realized in germanium evaporated at low temperature on silicon-on-insulator optical chips. We discuss the fabrication and integration and show experimental results in terms of dark current, responsivity and signal to noise ratio. [Copyright &y& Elsevier]