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A multichannel analyzer (MCA) for gamma ray spectroscopy is presented. The system comprises a silicon photomultiplier, an analog front-end readout IC, a piecewise-linear ADC, and a digital back-end. The AFE and the PWL-ADC were fabricated in a 180 nm CMOS process. A highly programmable architecture allows pulse-height analysis with reconfigurable resolution across the full dynamic range which enables variable energy bin-width in specific regions of interest with a smaller digital word length. This allows the implementation of a DBE with fewer resources, and optimal energy binning within a spectrum. The FPGA-based DBE performs histogramming for spectrum analysis. Measured peaks from 32 keV to 1.33 MeV and reconfigurable energy bin-widths of 3 keV to 58 keV show the versatility of the proposed MCA.

We present a study of the performances of a proximal gamma-ray ground station based on a 7 months continuous acquisition, including 42 rain episodes and 16 irrigations. In particular, we demonstrate the reliability of the station in discriminating irrigations and rains through their peculiar gamma signals fingerprint. This proof of concept experiment shows that proximal gamma-ray spectroscopy can potentially fill the spatial gap between punctual and satellite soil water content measurements, as well as provide an unbiased approach for producing comprehensive irrigations maps.

We present a 144-independent-channel SiPM-based detection module for gamma spectroscopy with a 3” Ce3+ -Sr2+ codoped Lanthanum Bromide (LaBr3) scintillator crystal (73 ph/keV conversion efficiency, 25 ns decay time), featuring 84dB dynamic range front-end electronics with automatic gain switching, state-of-the-art energy resolution (2.6% at 662 keV), 80kHz maximum acquisition rate and imaging capabilities. The relatively large number of independent channels is aimed at achieving a large energy range (up to 20MeV) as well as maintaining the best achievable energy resolution without sacrificing the spatial resolution in photon-interaction position reconstruction in order to correct for the relativistic Doppler effect that occurs in accelerator-based nuclear experiments due to the relativistic speed at which the radioactive nuclei move. Experimental measurements are reported to demonstrate the performance of the system in terms of energy resolution, spatial resolution, and dynamic range, confirming the possibility of using Silicon Photomultipliers (SiPMs) - already known for their high robustness, magnetic fields insensitivity, and fast response - as a suitable replacement of Photomultiplier Tubes (PMTs) in nuclear and particle physics experiments.

Artificial neural networks (ANN) based on learning the features of the entire measured gamma energy spectrum has been used for radioisotope identification and proved promising especially for gamma-ray spectroscopy with low energy resolution. The implementation of ANN method, however, requires tedious experimental measurement process in generation of training data for various radioisotopes. In this work, we propose an ANN-based radioisotope identification method with simulated training data. Gamma energy spectra of 27 different radioisotopes were generated with Monte Carlo simulation. A detector energy response model was proposed to match the energy spectra generated from simulation and measured from experiment, thus “pseudo” measured energy spectra of various radioisotopes transformed from simulation can be used for ANN training, which eliminates the tedious experimental measurement process for training data generation. To reduce the complexity of the training process, the principal component analysis (PCA) method was used for dimension reduction of the input energy spectra in ANN and the channel number of the energy spectra was reduced from 2000 to 50. The trained ANN was further used to identify experimentally measured gamma energy spectra of various radioisotopes including 60Co., 137CS., 18F, 131I, 226Ra and 232Th at 103, 104 and 105 count levels. In single isotope identification test, with increased count level, higher correct identification rate is achieved and at 105 count level, all the isotopes are correctly identified for all the samples. In mixed isotope identification test, at 105 count level, all the radioisotope combinations can be identified with a correct identification rate larger than 98%, which demonstrates the feasibility and accuracy of the ANN method. To conclude, the proposed ANN method with simulated training data features good radioisotope identification capability with greatly simplified training data generation process and is feasible for gamma spectroscopy with relatively poor energy resolution.

A compact module based on arrays of solid-state SiPM detectors (up to 144), integrated front-end and a crystal with large scintillation efficiency (3” LaBr 3 :Ce) for detection of gamma rays is presented. In addition to state-of-the-art energy resolution (2.6% at 662 keV) and sub-centimeter spatial resolution in reconstruction of the photon interaction point, this portable unit enables the angular localization of gamma sources as a function of the reconstructed interaction point distribution. The latter task is performed by means of k-NN and decision tree classifiers. The implementation of the reconstruction algorithm in the micro-controller of the acquisition node allows for relaxation of constraints in data transmission and, in case of cooperative networks, distribution of computational complexity. The system architecture and design choices are here presented in detail, followed by preliminary experimental results obtained with a 16 channel front-end ASIC.

Radiological measurements and traceability of materials are becoming more and more important in the industrial sector of stones and building materials for both producers and users. This is due to the recent European regulatory restrictions on the maximum level of radiological emissions for materials intended for use in public and private building structures. The proposed system, called CORSAIR (Cloud Oriented Radiation Sensor for Advanced Investigation of Rocks) is a cyber-physical system empowered by cloud-based technologies that consists of sensing nodes, data collection gateways and a centralized cloud application. These components are interconnected in a star-of-stars topology, exploiting respectively LoRaWan, Internet network, and provide specialized user interface. The system includes also handheld devices with dedicated user interface to control the sensing nodes on the field via WiFi Direct connection. The system introduces a fast, repeatable, real-time and nondestructive method to measure radiological emissions and other parameters of each single building material item, uniquely identified by an applied RFID tags. Moreover, it makes those data available to all stakeholders, enabling to trace the materials along the full market chain, from extraction to the final customer, with modern technologies.

We present a 144 Silicon Photomultipliers (SiPMs) detection module for gamma spectroscopy with 3" co-doped LaBr 3 scintillator capable of 2.6% energy resolution at the 137Cs emission photopeak (662 keV), photon-interaction position reconstruction and 84 dB dynamic range front-end electronics. This prototype, together with the detector mechanical robustness and magnetic field insensitivity, show that SiPMs are perfect candidate for a large variety of nuclear physics experiments.

Cs2LiYCl6:Ce3+ (CLYC) is a promising Li-based inorganic scintillator for its dual-mode detector capability to perform neutron detection and gamma spectroscopy. Pulse Shape Discrimination (PSD) between neutron and gamma-ray signals can achieve superior results owing to the fundamentally unique scintillation mechanisms within CLYC crystal. In this work, an 1×1 inch CLYC scintillator enriched with 95% 6Li was used for simultaneous neutron and gamma-ray detection. Difference on pulse rise time between neutron and gamma-ray was found and its effects on traditional charge integration method were analyzed. A pulse shape discrimination (PSD) method based on Fisher linear discriminant was used to discriminate neutron and gamma-ray signals with different parts of waveform. The results show that positive effect on neutron and gamma-ray PSD appears when the integral window is well set based on the pulse rise time. Fisher classification achieves better figure-of-merit (FOM) of 4.6±0.1 compared to charge integration method. This method also shows reliable screening ability only using the short recording waveforms whose distinctions are mainly from the rising part. When the length of waveforms is 80 ns, the FOM is 2.3±0.1. This benefits the applications of CLYC in high count rate situations with short recording waveforms.

LaBr 3 crystals are a key element for high-end gamma-ray detectors based on indirect conversion. Recent developments in high-density SiPM technology opened the possibility to solid-state readout of this crystals providing similar performance of PMTs. After having assessed the obtainable resolution and the imaging capabilities of smaller prototypes of this technology (1-2’’ scintillators), a compact readout system for gamma-spectroscopy with 3"×3" LaBr3 coupled to 144 SiPMs readout by a high-dynamic range (87dB) ASIC is under development, allowing imaging reconstruction together with high-resolution gamma-ray spectroscopy. The first experimental results will be here presented.

SIPHRA is a low-power (30 mW) application specific integrated circuit (ASIC) recently developed by IDEAS, Norway for readout of photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs). The ASIC has 16 input channels and one summing channel. Each channel can be used for timing and pulse height spectroscopy with a programmable shaping time of 200 ns, 400 ns, 800 ns, or 1600 ns. The current mode input stage (CMIS) is designed for large negative charge (-16 nC, -8 nC, -4 nC, and 0.4 nC), depending on the programmable attenuation. The ASIC contains a 12-bit ADC for pulse-height digitization. SIPHRA’s performance has been tested using a 4 $\times$4 array of 6 mm Jseries SiPMs from SensL and a number of scintillator crystals (BGO, LYSO, $LaBr_{3}:Ce and CeBr_{3}$). The $LaBr_{3}$:Ce detector has shown energy resolution (FWHM) of 3.4% at 662 keV and 2.5% at 1274 keV. In further measurements with a light emitting diode, the SiPMs have demonstrated the same energy resolution as obtained using discrete readout electronics.

We are working on scale up of several new plastic scintillator compositions. One composition uses Iridium complex fluors to obtain up to 3x higher light yields and high α/β ratios, for improved particle (alpha, neutron, fission product) detection and imaging. Other compositions include high loading of Bismuth for gamma spectroscopy and with Lithium for neutron detection. Plastics containing 21 wt% elemental Bismuth and an Ir fluor provide strong photopeaks and R(662 keV) ~9%. When activated with standard organic fluors, 10 in3 plastic scintillators containing 8 wt% Bismuth provide a strong photopeak with R(662 keV)~19%. A 5 in3 plastic formulation including 1 wt% Lithium-6 provides a neutron capture peak at 350 keVee, with 11% resolution for the capture peak.

New transparent ceramic scintillators offer advantages for applications in gamma spectroscopy and X-ray imaging. For gamma spectroscopy, excellent light yield, material uniformity, light yield proportionality, mechanical and environmental ruggedness can be achieved in polycrystalline ceramic oxide garnets. We have fabricated 5 in3 Ce-doped Gd garnet transparent ceramics. GYGAG(Ce) garnet transparent ceramics offer $^{\mathbf {\rho \, =\, 5.8g/cm^{3},\,}}$, $z_{eff}=48$, principal decay of 2 O 3 structure structure. The 12” x 12” GLO imaging plates outperform scintillator glass for MeV radiography, due to higher light yield (55,000 Ph/MeV) and better stopping, while providing spatial resolution of >8 lp/mm for MeV X-rays.

As interest of environmental radiation has increased, accurate analysis of the environmental radioactive sample has been demanded. The gamma ray spectroscopy is generally used to analyze the environmental radiation for solid radioactive samples such as soil compacted in a standard container. To improve the accuracy of the analysis, it is necessary to compact as much sample of the powder state as possible. Compacted amount of the sample and its density could be different depending on the force from measuring person in the case of conventional method using a compacting rod. In this study, we propose a method to improve the compacting rate with high power ultrasound for solid radioactive sample of powder state.

The Pulse pile-up in gamma ray spectroscopy is a severe problem because it degrades both energy resolution and detection efficiency, especially at high count rates. This paper presents two algorithms for signal recovery of peak pile up. These algorithms depend on experimental acquisition of gamma radiation signals with analog to digital converter at sampling rate 16MS/s. The first algorithm depends on a peak detection method that determines the peaks' parameters, which are recorded into a two rows matrix representing the amplitude and position of the peaks. The second algorithm depends on a peak sensitivity method, which determines the location of the maximum peaks using a local extreme method. The variance between each two adjacent points are calculated to find indices of nonzero elements that are larger than zero to determine the maximum amplitude of each peak. The resultant peaks correspond to peak location. These two methods are evaluated by comparing not only their parameters but also their fitting error. Moreover, the influence of these algorithms on the obtained spectrums are analyzed and evaluated. The results show that the second algorithm outperforms the performance of the first one due to the efficient recovery of overlapping peaks.

The advent of new plastic scintillator formulations opens avenues of application in terms of neutron-gamma discrimination. As a consequence, the likelihood that these detectors will be subject to regions of significant neutron flux is high. In order to study the tolerance to radiation damage a number of samples of both EJ-299 and EJ-200 plastic scintillator were irradiated with fast neutrons using a neutron flux of up to 2.2×1012 (+/−5.6%) n/cm2/s. All samples were cut to a size of 30 mm × 30 mm × 15 mm and polished prior to irradiation. The radiation response of the samples was measured by performing standard gamma spectroscopy on lab sources. The optical emission spectra were analysed by irradiating each sample with an 80 kV X-ray beam from a Hamamatsu X-ray tube. Optical spectroscopy of the scintillation light was recorded using an Ocean Optics QE6500 spectrometer, and the opacity of the irradiated samples was measured with a Cary 5000 spectrophotometer. The effect on the peak emission wavelength, optical intensity, and spectral shape of the scintillation was determined as a function of neutron fluence.

Thallium-bromide (TlBr) is a viable alternative to CZT for room-temperature gamma ray spectroscopy because of its high atomic number, high density, and wide band-gap. Sub-1% FWHM energy resolution at 662 keV has been achieved on 5 mm thick pixelated devices, however, these results are mostly limited to stable operation at −20°C. During room-temperature operation, the devices degrade and fail, a phenomenon known as polarization. Polarization is likely caused by bulk-to-contact interactions facilitated by ionic conduction. In 2008, Hitomi et al. found that room-temperature lifetime could be extended by applying Tl electrodes. In this work we verify stable room-temperature performance of a 4.1 mm thick pixelated TlBr detector with Tl electrodes. Energy resolution, mobility-lifetime product, and resistivity are characterized and presented. Resolutions of 1.6% and 1.2% FWHM are achieved for all depths and cathode-side events only, respectively. A very high electron mobility-lifetime product is calculated: 3.1±0.2 ·10-2 cm2/V.

Many applications require the generation of gamma spectra at event rates in excess of 106 s−1 as well as very good energy resolution, e.g., safeguards, emergency response, and nondestructive assay. Good energy resolution is especially important when lower activity isotopes are sought among a large background (or foreground) that would otherwise dominate the spectrum, such as the minor actinides present in spent fuel after a long cool down time. To this end, we anticipate that high-energy-resolution detectors, such as high-purity germanium, can be adapted to high rates at a small cost to energy resolution, rather than starting with a detector with high-rate capability and medium energy resolution, e.g., LaBr 3 . Here, we present recent design improvements of the ultra high-rate germanium (UHRGe) detection system to allow for a 24-channel spectrum generation output. Further, we present a sensitivity study to determine how uncertainties in parameters of the detection system response affect the resulting spectra. A preamplifier simulator is developed that can emulate the output of the system at various event rates, including very high rates in excess of 106 s−1. Here, we show how various levels of uncertainty in the DC offset of the preamplifier output can affect the full width at half max (FWHM) of the resulting spectrum.

A specific Differential Die-away Analysis (DDA) system in an advanced non-destructive analysis (NDA) system using a compact pulsed neutron generator has been studied and designed for non-nuclear proliferation in the Japan Atomic Energy Agency (JAEA). The NDA system is composed mainly of combination of four active neutron analysis techniques, DDA, PGA (Prompt Gamma-ray Analysis), NRTA (Neutron Resonance Transmission Analysis) and DGS (Delayed Gamma Spectroscopy). The design study on the DDA section in the system has been performed with Monte Carlo simulation code (MCNP) to evaluate the performance of the DDA system. The simulation result shows that the 239Pu mass (contained in MOX fuel) of as low as 0.01 g is detectable. The dependence of the performance on the type of the inner wall material in the DDA section and the thickness of the cylindrical moderator placed to circumscribe the measurement sample are presented.

Gamma Ray Spectroscope (GRS) is a system to detect, measure, analyze and display the Gamma Ray Spectrum. It consists of 4k Multi Channel Analyzer (MCA), 1.5” × 1.5” Thallium activated Sodium Iodide(NaI(Ti)) scintillation detector and a PC based MCA software. MCA has all the required facilities to handle the scintillation detector and to convert the signals from detector into meaningful data. MCA software is used to display the Gamma spectrum and important parameters. GRS is also used for identification of gamma radiating source. This paper deals with the algorithm that has been employed to identify the gamma sources. The Gamma source identification algorithm is a peak scanning based algorithm and scanned data is then matched with library data. The complexities of signal processing and data handling are reduced to great extent without much compromise in the accuracy of identification. Algorithm was developed with appropriate weightage to speed and accuracy.

Lutetium Oxyorthosilicate (LSO) is an attractive scintillator for positron emission tomography (PET) imaging, due to its relatively high light output, short decay time, and high stopping power. LSO has a 2.6% natural abundance of Lu-176, a long-lived (3.78×1010 years) radioisotope that generates an intrinsic background. This low background rate has been capitalized on to perform PET quality checks and measure transmission data. In this work, LSO was exposed to the neutrons produced by the O-18(p, n)F-18 reaction in a Siemens Eclipse Cyclotron to selectively alter the intrinsic background rate. The cyclotron was run for a total of 1827 microamp-hours over two weeks, with mean proton energy of 11 MeV. Ten LSO pixels (4×4×20 mm3) were placed in locations selected for a desired neutron energy range. The range of neutron energies produced permitted the Lu-175(n,γ)Lu-176 and Lu-176(n,γ)Lu-177 reactions. Three of the pixels were placed behind polyethylene to further moderate the neutrons. The pixel's scintillation properties were measured to determine if they had been damaged by the irradiation. Gamma ray spectroscopy was performed for several weeks following the irradiation to evaluate the transmutations engendered. Despite an increase in trapping centers, scintillation properties were not changed, and the expected Lu-177 activation occurred.

Cs 2 LiLaBr 6 (Ce) (CLLB) crystal scintillator shows great potential as a radiation detection material with excellent energy resolution for gammas, sensitivity to neutrons, and the ability to separate the two using pulse shape discrimination (PSD). Experiments have been performed testing this material using silicon photomultipliers for creation of compact, easily-portable detectors for dual gamma ray spectroscopy and neutron detection. Pulse shape discrimination in CLLB is achieved by analyzing the scintillation pulse decay on the time scales of >1 μs. This feature enables the silicon photomultipliers with low afterpulsing to achieve suitable discrimination. Experiments have been conducted attempting to find a suitable cost/efficiency compromise that maximizes performance by varying crystal cerium concentration along with silicon photomultiplier type and placement position. A disk of CLLB (diameter = 52 mm, thickness = 6 mm, 6Li enriched) coupled to a 6×6 mm2 silicon photomultiplier can achieve 4.4% gamma ray energy resolution at 1275 keV, and 74% thermal neutron detection efficiency with a high pulse shape discrimination figure-of-merit of 1.9.

CdZnTe imaging gamma-ray spectrometers using digital pulse processing techniques have shown great promise in recent years. The energy resolution of 15 mm thick CdZnTe spectrometers has improved to around 0.4 % FWHM at 662 keV for single pixel events and near 0.6 % FWHM at 662 keV using all events, regardless of the number of pixels triggered. Additionally, the position resolution through subpixel position sensing has improved to less than 300 μm FWHM for 662 keV gamma-rays. This technical progress has encouraged the use of CdZnTe in challenging environments with high gamma ray fluxes such as nuclear power plants. CdZnTe is also being studied for use in medical imaging applications as well as nuclear safeguards and treaty verification where high count rate environments may be encountered. Signal pulse waveforms generated from charge motion in CdZnTe were studied at high count rates to learn how the material responds in high gamma-ray fluxes. The relationship between average preamplifier decay slope and dose rate is shown to be monotonic. This relationship could be used in a real system to estimate the dose rate on the detector surface. Minimal energy resolution degradation was observed up to 50 mR/hr. Beyond 50 mR/hr, the energy resolution degrades more substantially for multiple pixel events due to chance coincidence Compton scattering events. Changes in the electric field due to positive space charge accumulation were observed which likely contributes to the energy resolution degradation. Preamplifier instability is the other major contributor to energy resolution degradation.

High Purity Germanium (HPGe) radiation detectors are widely used for the gamma ray spectroscopy due to their best energy resolution. However, the detector response including Absolute Full Energy Peak (AFEP) efficiency, photo-fraction, Compton-to-photo ratio, etc., depends on the different physical parameters. The main advantage of Monte Carlo simulations lies in the fact that we can separately study the effect of different physical parameters. In this study, we present simulation results of the HPGe detector using Electron Gamma Showers 5 (EGS5) code and compare the simulation results with the already published data. A difference of about 5% was observed when compared with MCNP simulation and experimental results. Finally, optimum value of the Lead shield thickness was determined to be 5 cm for collimator diameter of 12 mm for different energies of interest.

Basic concepts and preliminary results of creating high rate digital spectrometry system using efficient ADCs and latest FPGA are presented as well as a comparison with commercially available devices.

Most of nuclear reactor developments are using evaluated data base for numerical simulations. However, the considered databases present still large uncertainties and disagreements. To improve their level of precision, new measurements are needed, in particular for (n, xnγ) reactions, which are of great importance as they modify the neutron spectrum, the neutron population, and produce radioactive species. In 2003, the IPHC group started an experimental program to measure (n, xnγ) reaction cross sections using prompt gamma spectroscopy and neutron energy determination by time of flight. Measurements of (n, xnY) cross section have been performed for 235, 238u, 232Th, nat, 182, 183, 184, 186W natZr The experimental setup, consisting of HPGe detectors and a fission chamber, is installed at the neutron beam at GELINA (Institute for Reference Materials and Measurements (IRMM), Geel, Belgium). It has recently been upgraded with the addition of a highly segmented 36 pixels planar HPGe detector. The setup is equipped with a high rate digital acquisition system. The analysis of the segmented detector data requires a specific procedure to account for cross signals between pixels. An overall attention is paid to the precision of the measurement. The setup characteristic and the analysis procedure will be presented along with the acquisition and analysis challenges. Examples of results and their impact on models will be discussed. Finally, the perspectives on complimentary experiments will be presented.

Canberra Industries has developed a specialized software package, Advanced In-Situ Object Counting System (A-ISOCS), which is based on absolute gamma-spectrometric measurements. It is intended for the verification of the quantity of nuclear materials under conditions where measurements are challenged by incomplete information on the properties of assayed objects which are inspected by the International Atomic Energy (IAEA)'s inspectors. A-ISOCS introduces a technique, which is called the automated optimization that allows the users to determine unknown sample parameters as well as the mass and isotopic composition of nuclear materials. The optimization process is carried out by using benchmarks referring the information included within the gamma-ray spectrum of the measured item. For each benchmark, Figure-of-Merit (FOM) is calculated and used to find the most consistent quantitative result (the best solution) corresponded to the minimized FOM. We have evaluated the capabilities and performance of A-ISOCS based on the measurements of uranium standard reference material samples, which have well-known geometry parameters and physical properties. In addition the applicability of the software to field measurements was assessed with an extensive set of gamma-ray spectra from holdup materials collected at uranium bulk handling facilities. This paper summarizes the results of our evaluation activity.

In the context of criticality accident alarm system tests, several experiments were carried out in 2013 on the PROSPERO reactor to study the response to neutron and gamma of different devices and dosimeters, particularly on the SNAC2 dosimeter. This article presents the results of this criticality dosimeter in different configurations, and compares the experimental measurements with the results of calculation performed with the TRIPOLI-4 Monte-Carlo Neutral Particles transport code. PROSPERO is a metallic critical assembly managed by the Criticality, Neutron Science and Measurement Department located at the French CEA Research Center of Valduc. The core, surrounded by a reflector of depleted uranium, is composed of 2 horizontal cylindrical blocks made of a highly enriched uranium alloy which can be placed in contact, and of 4 depleted uranium control rods which allow the reactor to be driven. This reactor, placed in a cell 10 m × 8 m × 6 m high, with 1.4-meter-thick concrete walls, is used as a fast neutron spectrum source and is operated at stable power level in delayed critical state, which can vary from 3 mW to 3 kW. PROSPERO is extensively used for electronic hardening or to study the effect of the neutrons on various materials. The SNAC2 criticality dosimeter is a zone dosimeter allowing the off line measurement of criticality accident neutron doses. This dosimeter consists of the pile up of seven activation foils embedded into a 23 mm diameter × 21 mm height cadmium container. The activation measurement of each foil, using a gamma spectroscopy technique, gives information about the neutron reaction rates. The SNAC2 software allows the spectrum unfolding from these values, taking into account the hypothesis of a particular spectrum shape, in three components: a Maxwell spectrum component for the thermal range, a 1/E component for the epithermal range, and a Watt spectrum component for the high energy range. Moreover, from the neutron spectrum, the SNAC software can calculate the neutron fluence integrated by the dosimeter and the neutron dose. During the 3 weeks measurement campaign many radioprotection devices were used. To modify the spectrum seen by these devices, several shields of various thicknesses made of concrete or polyethylene, with or without cadmium covers, were placed in the PROSPERO cell. These devices allow the study of criticality accident spectra in several environments: from metal to pseudo liquid. The fluxes measured by the SNAC2 devices were compared with TRIPOLI-4 calculations.

Surface deposition of activated corrosion product on oxide layers of light-water reactor primary system components is the primary source for ex-core radiation fields and personnel radiation exposure. Understanding the deposition mechanism and what factors influence the deposition and release behaviors are crucial for developing effective radiation field reduction measures. One of the available tools to assess the surface deposition is inplant gamma spectrometry, which has been performed for several decades using either sodium iodide (NaI) or high-purity germanium (HPGe) detectors. Lately, the much more mobile cadmium-zinc-telluride (CZT) detectors are increasingly employed by stations because of their ease in use and handling. However, all of these gamma detectors face the same challenges; namely large-geometry samples of inconsistent sample compositions and sometimes gaps in the information necessary to establish proper efficiency calibrations. This paper reviews current measurements and efficiency calibration approaches taken in the industry. The validity of the measurement results and the feasibility of the data's use in understanding source term behavior is examined. Suggestions are made for the development of a more robust deposit characterization and radiation field monitoring program.

The first step of the present study was to simulate the γ-radioactivity produced by photoneutrons in the treatment head of a decommissioned medical LINAC. These results, obtained with MCNPX and CINDER'90, are then compared with γ-ray spectrometric measurements of parts of the treatment head. Our ultimate objective is to simulate the associated production by photonuclear reactions of pure β-emitters, which are more difficult to access experimentally than the γ-ray emitters.

This work deals with the development of a new gamma detector based on Silicon Drift Detectors (SDDs) to read out large (2″ up to 3″) LaBr3:Ce scintillators for gamma-ray spectroscopy for astronomy applications, an activity supported by ESA. SDDs, characterized by high quantum efficiency and low electronic noise, are good candidates in such applications with a wide energy range of gamma rays to be detected from 150 keV to 15 MeV. The gamma-ray detection system here presented is composed of a 2″×2″ LaBr3:Ce scintillator coupled with four SDD modules arranged in a 2×2 format (a total of 36 SDDs). An energy resolution of 3.5% FWHM at 662 keV has been achieved with this detection system being read out by custom developed electronics. In this work we will report on the SDD technology used, their X-ray characterization, readout electronics, experimental setups and gamma-ray spectroscopy results.

This work aims to create a library of predicted detector responses used for real-time background estimation during airborne gamma-ray spectroscopy. The simulated spectra are a function of naturally occurring radioactive potassium, uranium, and thorium (KUT) and radioactive daughter products which are present in terrestrial-based materials. Self-attenuation within these materials varies, such that the gamma spectra emitted from the surfaces can differ, despite all having KUT origins. This study also compares various simulated detector responses among materials to determine if some could be accurately scaled from another across reasonable helicopter altitudes and orientations relative to the ground. Results show that materials with comparable sample thicknesses can be scaled consistently across altitude. This work allows for efficient background estimation via aggregation of simulated detector responses in real time.

Digitizing scintillation pulses with the Multi-voltage threshold (MVT) method shows great potentials for building all-digital positron emission tomography (PET). In this paper, we introduce the MVT method into gamma-ray spectroscopy. An accurate scintillation pulse model used in pulse fitting is especially important to get precise energy when implementing the MVT in gamma-ray spectroscopy, since a wide-range energy needs to be measured with limited MVT samples. However, accurately model the scintillation pulse is a not trivial work, as the physical model of scintillation pulse is not only determined by scintillator and photo-electric device but also the parasitic capacitance and inductance of the read out circuits. The unideal scintillation pulse model adopted in the MVT degrades the spectral accuracy and the energy resolution. To address this problem, an energy calibration method is proposed in this paper. By measuring the energy of scintillation pulses with different pulse amplitudes with high sample rate ADC and the MVT respectively, a look-up table is generated by dividing the energy obtained in the ADC to that in the MVT. The look-up table is used as calibration coefficient to correct the energy in the all-digital data acquisition system (DAQ) based on the MVT. Our preliminary results show that with the proposed energy calibration method, the peak-to-valley ratio in the Cs-137 energy spectrum is increased by about 1.5 times and the energy resolution is improved from 6.1% to 3.8% at 662 keV with LaBr3/PMT detector, which is equivalent to that of a 5 GSPS ADC.

In this study, the impact of impurities on the scintillation performance of SrI2(Eu) was characterized along with their segregation behavior. Single crystals of SrI2 codoped with 4% Eu and 0.2% X = {Cs, Mg, Fe, Sn} were grown by the vertical Bridgman-Stockbarger method from the melt. Pulse-height gamma ray spectroscopy measurements demonstrated that samples codoped with Cs, Mg, and Fe were slightly degraded in light yield and energy resolution. No significant impact on the decay time and emission peak centroid, 1.5 µs and 428 nm, respectively, were observed. However, the Sn-codoped sample possessed only 55% of the light yield and only half the resolution of SrI2(Eu). In addition to its Eu2+ 5d-4f emission at 428 nm, a broader emission above 550 nm was observed in this sample, accompanied by a shorter decay time of 1.1 µs. Moreover, Sn did not segregate as well as Cs, Mg, and Fe, and thus cannot be removed as easily during growth or zone refining purification. Finally, the results of this study will aid in developing a better understanding of how codoping influences light output.

To have a better energy resolution in a gamma ray spectroscopy, an appropriate shaping of the nuclear pulses is necessary. The shaping improves two parameters namely the counting rate and signal to noise ratio (SNR). Trapezoidal, Gaussian and Cusp - these three shaping algorithms have been simulated to assess the suitability in terms of these two parameters. The energy resolution in the spectrum depends on these parameters. The shaping algorithms are implemented using field programmable gate array (FPGA) at 100MHz clock with 100MSPS ADC. In multi channel analyzer (MCA) DAQ setup, FPGA based shaper hardware is used to study the shaping algorithm with the help of the spectrum of 60 Co and 137 Cs as radiation sources. This paper has reported the results of the real time implementations of this work.

Nevada Nanotech Systems, Inc. (NevadaNano) has developed an automated, multi-sensor Chemical, Biological, Radiological, Nuclear and Explosive (CBRN&E) detection system to perform a multiple-measurement, orthogonal analysis of trace chemical samples and identify radioactive isotopes. One application is threat detection in shipping containers, where samples can be collected over long periods of time (hours to days) in order to detect low levels of threat molecules and radiation. This system, called the C-Scout™, uses a Molecular Property Spectrometer™ (MPS™) - a low-cost, low-power, micro-electromechanical-systems (MEMS) chip capable of measuring numerous thermodynamic and electrostatic molecular properties of sampled vapors and particles - coupled with a compact, highresolution, solid-state gamma spectrometer for identifying radioactive materials, including isotopes used in dirty bombs and nuclear weapons. C-Scout™ transmits results using a radio frequency communication system. Here we provide an overview of the system design and operation and present threat detection results from laboratory and field tests.

In this paper results of gamma spectroscopy with the GAGG: 1%Ce scintillators with different Al-to-Ga ratio are showed. The study covered measurements of emission spectra, light output, energy resolution and non-proportionality for each crystal. It was observed that the light output of the recent set of scintillators was significantly improved in comparison to the previous set and varies from 40000 to 55000 ph/MeV. The best energy resolution of 3.7% at 662 keV was obtained using a Hamamatsu S8664-1010 avalanche photodiode. This result can be compared to scintillators possessing very good energy resolution, like LaCl 3 and CeBr 3 .