HPGe Research Articles

Comparison between carrier transport property and crystal quality of TlBr semiconductors

Thallium bromide (TlBr) semiconductor detectors are being developed as promising candidates for high-detection-efficiency, high-energy-resolution, and room-temperature gamma-ray spectrometers. This study presents methods for evaluating TlBr crystal quality and carrier transport characteristics using neutron Bragg-dip imaging and the time-of-flight method for pulsed-laser-induced carriers, respectively. Neutron Bragg-dip imaging effectively determines the crystal orientation distribution, revealing crystal imperfections and grain boundaries. Time-of-flight measurements provide a spatial distribution of carrier mobility. In this study, two samples obtained from both the upstream and downstream region in the crystal ingot were evaluated. Although both samples show similar crystal quality, the upstream sample showed high carrier mobility across all areas, whereas the downstream sample exhibits low mobility in some areas. These findings suggest that, at least within the range of carrier mobility currently obtained, the effect of crystal integrity on carrier mobility is less significant than that of impurities. In conclusion, combining neutron Bragg-dip imaging with carrier mobility measurements offers a comprehensive approach to evaluating and improving TlBr detectors.

Estimation of the Effective Radiation Dose in Nuclear Medicine Workers from Dhaka by Measuring Radioactivity in Urine Sample Resulting from Internal Exposure

This study estimates the effective doses and activity concentration from 151 urine samples which are collected from 15 (Fifteen) occupational workers at National Institute of Nuclear Medicine and Allied Science (NINMAS) in Dhaka, Bangladesh. The radioactivity concentration in urine sample is due to intake of I-131, Tc-99m and F-18. The samples have been analyzed using High Purity Germanium (HPGe) detector. The radioactivity of I-131 and Tc-99m was found 0.91 ± 0.26 BqL-1 to 504.49 ± 6.03 BqL-1 and 0.15 ± 0.21 BqL-1 to 191.19 ± 6.98 BqL-1 respectively. Radioactivity of F-18 was found from 0.031 ± 0.022 BqL-1 to 0.282 ± 0.065 BqL-1. The effective doses of occupational workers have been also calculated using the radioactivity concentration and the dose coefficient according to ICRP publication 78. Jagannath University Journal of Science, Volume 11, Number 1, June 2024, pp. 64−80

Short-Wave Infrared Upconverting Nanoparticles.

Optical technologies enable real-time, noninvasive analysis of complex systems but are limited to discrete regions of the optical spectrum. While wavelengths in the short-wave infrared (SWIR) window (typically, 1700-3000 nm) should enable deep subsurface penetration and reduced photodamage, there are few luminescent probes that can be excited in this region. Here, we report the discovery of lanthanide-based upconverting nanoparticles (UCNPs) that efficiently convert 1740 or 1950 nm excitation to wavelengths compatible with conventional silicon detectors. Screening of Ln3+ ion combinations by differential rate equation modeling identifies Ho3+/Tm3+ or Tm3+ dopants with strong visible or NIR-I emission following SWIR excitation. Experimental upconverted photoluminescence excitation (U-PLE) spectra find that 10% Tm3+-doped NaYF4 core/shell UCNPs have the strongest 800 nm emission from SWIR wavelengths, while UCNPs with an added 2% or 10% Ho3+ show the strongest red emission when excited at 1740 or 1950 nm. Mechanistic modeling shows that addition of a low percentage of Ho3+ to Tm3+-doped UCNPs shifts their emission from 800 to 652 nm by acting as a hub of efficient SWIR energy acceptance and redistribution up to visible emission manifolds. Parallel experimental and computational analysis shows rate equation models are able to predict compositions for specific wavelengths of both excitation and emission. These SWIR-responsive probes open a new IR bioimaging window, and are responsive at wavelengths important for vision technologies.

Pixelation method for the FARCOS array

A pixelation method addresses the challenge of accurately assigning coordinates to each particle that impinges on the detector area. The pixelation method used for the analysis of the data acquired with Double-Sided Silicon Strip Detectors of the Femtoscope ARray for COrrelations and Spectroscopy FARCOS is described here. The application of the pixelation method requires several tasks to be performed. First, the coincidence in the detection time of the particles of front and back signals allows the elimination of spurious events. The second fundamental operation is the recovery of inter-strip events obtained comparing the energies of detected front and back side signals in all possible configurations. Two-alpha coincidences are analysed and the 8Beg.s. resonance is observed to compare the energy resolution of recovered inter-strip events with that of single-strip events. Using this pixelation method, a 41 ± 8% improvement in the efficiency of detecting three-alpha particles was achieved.

ASSESSMENT OF THE LEVELS OF NATURAL RADIOACTIVITY AND THE POSSIBILITY OF RADIATION RISKS IN SOIL SAMPLES TAKEN FROM DIFFERENT LOCATIONS IN SOUTHERN ALMAZAR-ALKARAK, JORDAN

A wide study of environmental radioactivity levels in soil samples from Southern Almazar-Alkarak in Jordan was performed to develop a radiological map of the area. 15 soil samples were collected from different locations across the region and subjected to analysis using a high-purity germanium detector (HPGe). The study showed that the average levels of natural radionuclides 226Ra, 232Th, 238U and 40K were 34.5±0.98, 25.6±1.3, 32.2±3.7 and 278.5±15.7 Bq.kg−1, respectively. Also, to evaluate the radiological danger, the radium equivalent activity (Raeq) is calculated, absorbed gamma dose rate (D), annual effective dose equivalent (AEDE) and external hazard index (Hex), internal hazard index (Hin). The average values for these parameters were determined to be 92.5 Bq.kg−1, 43.0 nGy h−1, 52.7 µSv y−1 and 0.25Bq.kg−1, 0.34Bq.kg−1 respectively. The values of the gathered samples stay below the allowable limits. Consequently, the examined region does not present any radiation risk to the general population. Moreover, it has been discovered that there is no concentration of 137Cs radionuclide activity in the studied area.

Efficiency of sub-THz – DC energy conversion of a silicon detector

The efficiency of sub-THz to DC energy conversion of a silicon-based plasmonic detector was studied. The dependence of the signal at the detector output on the incident radiation power was measured. In the power linear region, the coefficient η was shown to grow with increasing power and to saturate in the sub-linear regime. The maximum achieved values of η were 0.4% for the radiation frequency of 97 GHz. The measurements were carried out both at room temperature and when the detector was cooled to liquid nitrogen temperature.

Determination of natural radioactivity levels in soil samples from irrigated vegetable farming land in and around Addis Ababa, Ethiopia.

Soil samples were collected from vegetable agricultural areas in and around Addis Ababa, and their levels of radioactivity were measured. Gamma spectrometry with high-purity germanium detector was used to quantify radioactivity level. The average concentration of 226Ra, 232Th, and 40K were 32.8±2.1, 62.4±4.4, and 544.3±23.3Bqkg-1 respectively. The mean values of 232Th and 40K are higher, whereas the value of 226Ra is comparable with world average values. Radiological hazard indices, including radium equivalent activity (Raeq), absorbed dose rate (Dr), outdoor annual effective dose equivalent (Deff), external hazard index (Hex), internal hazard index (Hin), and gamma radiation representative level index (Iγ), were calculated based on the activity concentration of 226Ra, 232Th and 40K. The mean values were 163.9Bqkg-1, 78.7 nGy h-1, 0.10mSv y-1, 0.44, 0.53, and 0.60 respectively. All indices are lower than global recommended limit values. These results revealed that radiation hazard due to radionuclides in the soil of the study area is insignificant.

Optimization of the Electron Spectrometer Telescope geometry for the PRESET satellite through Monte Carlo simulation

The Electron Spectrometer Telescope (EST) aboard the PRESET satellite mission aims to measure the pitch angle distribution of 0.3–4 MeV electrons in the outer Van Allen belts. The PRESET satellite is planned to launch into a sun-synchronous low Earth orbit in Q2, 2026. We present comprehensive Monte Carlo simulations to optimize the design and response of the EST instrument. The EST consists of a stack of silicon strip detectors and a collimator to take pitch-angle dependent electron spectral measurements with a target angular resolution of 6° while rejecting the proton, heavy ion and gamma detection events. Various collimator designs and detector stacking configurations are investigated using the Geant4 code to deduce an optimal design and configuration. For validation of the Geant4 simulations, a benchmark test spectrometer was set up using a stack of four silicon detectors and a good agreement between the measured and simulated responses was found for a beta spectrum from a 90Sr/90Y source. The collimator design was optimized by adjusting total length, aperture size, number of view-ports and collimator materials. The optimum aperture size and the number of view-ports were determined by varying them and selecting the best cases that meet the angular resolution and the geometric factor requirements. Moreover, to address the under-utilization of the front position-sensitive detector encountered in a typical pin-hole collimator, two offset collimators with tilted axes were employed. Extensive simulations were carried out by varying the number of silicon detectors and the thickness of each detector to optimize the configuration of the silicon detector stack. An optimum thickness of the front detector was found to be 140 µm, which can minimize the perturbation counts caused by the proton detection events. For the other detectors, a stack of four 1.5 mm thick detectors was chosen to achieve a good sensitivity to low energy electrons at a tolerable complexity of the system. The angular response simulated for the optimum design of the EST showed a resolution of 5.5°, which is slightly better than the target resolution of 6°. The response matrices of the final design simulated for isotropic electron and proton fields showed a high geometric factor, which is expected to produce an average electron counting rate of 230 cps within the trapped region with a negligible contamination of the electron spectrum by protons except for a mild contamination by the 1.0–1.1 MeV protons.

The 2024 LaBr[formula omitted](Ce) detector setup for the FAMU experiment

The FAMU experiment, led by INFN at the Rutherford Appleton Laboratory (UK), is designed to measure the Zemach radius of the proton in muonic hydrogen (μp) with uncertainty better than 1%. A set of LaBr3(Ce) scintillating crystals, complemented by a High-Purity Germanium (HPGe) detector, are used to detect the delayed muonic oxygen (μO) X-ray emission, which signals the muonic hydrogen spin flip excited with a tunable MIR laser. The detector setup is in continuous development. After two periods of measurement in 2023, the detector configuration is currently being upgraded for the 2024–2025 runs with new detectors read out by SiPMs to enhance signal-to-noise ratio and improve time performance. In particular, all ½” scintillators are being substituted with 1” ones, increasing the solid angle coverage and optimising energy resolution and timing performances.

The European strategy and detector R&D program

The latest update of the European Strategy for Particle Physics stimulated the preparation of the European Detector Roadmap document in 2021 by the European Committee for Future Accelerators ECFA. This roadmap, defined during a bottom-up process by the community, outlines nine technology domains for HEP instrumentation and pinpoints urgent R&D topics, known as Detector R&D Themes (DRDTs). Task forces were set for each domain, leading to Detector R&D Collaborations (DRDs), now hosted at CERN. After an intensive period over the last months, seven DRD collaborations have been established which are now starting to set up their collaboration structures and begin to work. One is still in the preparation phase.In this publication, I will give an overview of the set-up process and the current status of all DRD collaborations covering detector developments in the field of gaseous detectors, noble liquid detectors for rare event searches, semiconductor detectors, photodetectors and concepts for particle ID, quantum sensors, calorimetry, electronics for HEP instrumentation and mechanical and integration aspects.

Estimation of radiological health risks due to 226Ra, 232Th, and 40K in foods consumed in Iraqi Kurdistan Region

ABSTRACT This study investigates the activity concentration of natural radionuclides in a diverse range of food samples in the Koya district markets food baskets, including both domestic and imported products. The samples cover annual crops (e.g. coffee, tea, kidney beans), tree nuts (e.g. almonds, pistachios), and other items (e.g. beef, fish, milk) by using a high-purity germanium (HPGe) detector. This research addresses a notable gap by providing baseline data on radionuclide concentrations and assessing potential health risks. Average activity concentrations for ²²⁶Ra, ²³²Th, and ⁴⁰K were 0.943, 0.367, and 191.8 Bq kg−1, respectively. Radium equivalent activity values ranged from 2.88–58.48 Bq kg−1, all below the safety limit. The average excess lifetime cancer risk (ELCR) was 0.154 mSv a−1, indicating safety for most samples, though coffee and tea showed higher levels. This study provides new data crucial for future research and regulatory monitoring, underscoring the need for further investigation into geological impacts on radionuclide levels.

Experimental evaluation of the impact of ZnO on the radiation shielding ability of B2O3–PbO–ZnO–CaO glass systems

In this study, we used the melt quenching process to develop inexpensive, new radiation shielding glasses. The prepared glasses have a general formula 40B2O3–20PbO-(y)ZnO-(40-y)CaO, (y = 20, 25, 30 and 35 mol%). These glasses' gamma-radiation shielding properties were experimentally measured using Am-241, Co-60, and Cs-137 sources and a High-Purity Germanium (HPGe) detector, revealing that incorporation of ZnO had a positive impact of the density of these glasses. Moreover, the incorporation of ZnO enhanced the prepared glasses' attenuation performance. With greater energy the half value layer increased, and by a factor of 45 with a 0.059–1.333 MeV energy increase. For the four studied glasses the radiation protection efficiency (RPE) values are 100 % efficient at low energies (0.059 MeV), with a drastic decrease in the values across all four samples as the energy increases from 0.06 to 0.662 MeV.

Low Energy Neutron-induced Charged-particle (Z) (LENZ) instrument development with a focus on pulse shape discrimination for low-energy charged particles

To study neutron-induced charged-particle reactions with high precision, the Low Energy Neutron-induced Charged-particle (Z) instrument (LENZ) was developed at the Los Alamos Neutron Science Center. For the interest of measuring (n,p) and (n, α) reactions simultaneously, Pulse Shape Discrimination methods were investigated to identify different charged particles in the energy range of 3 - 20 MeV and improve signal-to-background ratios using Double-sided Silicon Strip Detectors and waveform digitizers. The risetime and pulse shape properties of detected charged particles were characterized for various silicon detector’s thickness with different orientations. During the post-processing of waveforms, we implemented different digital filters for effective particle identifications and improved energy- and timing- resolutions. We validated the optimized digital filters and pulse shape analyses, via measurements with 228Th and 229Th calibration sources, proton-induced reactions on a 7LiF target, and neutron-induced reactions on CH2, Ta2O5, 58Ni, and 6LiF/59Ni targets at the time-of-flight facility, LANSCE. The summary of effective thresholds and Figure of Merits on separating different charged particles is reported.

Design of a triggerless readout electronics system for CDEX-50

Direct detection of light-mass dark matter is a frontier topic in international physics research. The reduction of system threshold is important in order to improve the sensitivity of light-mass dark matter detection. The scientific goal of the China Dark Matter Experiment (CDEX) at Jinping Underground Laboratory in China is to detect WIMPs utilizing a high-purity germanium array detector. CDEX-10 achieved the most sensitive results in the 4 to 5 GeV/c 2 range. CDEX-50 aims to achieve an energy threshold of 100 eV, which significantly increases data bandwidth and complicates the implementation of noise reduction algorithms, thereby posing challenges to the readout electronics system. In this paper, a triggerless readout electronics system based on FPGA-GPU is designed for CDEX-50, which can achieve full energy range detection from 100 eV to 10 MeV. A verification prototype of a triggerless electronics system utilizing a Broad Energy Germanium (BEGe) detector has been developed to test the performance of high-bandwidth transmission and data processing. The results demonstrate that the bit error rate for the high-speed transmission link of the triggerless readout electronics system is below 1015. Furthermore, the FPGA-GPU transmission bandwidth, utilizing P2P DMA, achieves 100.2 Gbps, and the mean filter implemented on the GPU is capable of processing a 64 Gbps data stream in real-time. These results provide foundation for the design of the triggerless readout electronics system for CDEX-50.

An extreme thermal cycling reliability test of ATLAS ITk Strips barrel modules

At the end of Run 3 of the Large Hadron Collider (LHC), the accelerator complex will be upgraded to the High-Luminosity LHC (HL-LHC) in order to increase the total amount of data provided to its experiments. To cope with the increased rates of data, radiation, and pileup, the ATLAS detector will undergo a substantial upgrade, including a replacement of the Inner Detector with a future Inner Tracker, called the ITk. The ITk will be composed of pixel and strip sub-detectors, where the strips portion will be composed of 17,888 silicon strip detector modules. During the HL-LHC running period, the ITk will be cooled and warmed a number of times from about -35°C to room temperature as part of the operational cycle, including warm-ups during yearly shutdowns. To ensure ITk Strips modules are functional after these expected temperature changes, and to ensure modules are mechanically robust, each module must undergo ten thermal cycles and pass a set of electrical and mechanical criteria before it is placed on a local support structure. This paper describes the thermal cycling Quality Control (QC) procedure, and results from the barrel pre-production phase (about 5% of the production volume). Additionally, in order to assess the headroom of the nominal QC procedure of 10 cycles and to ensure modules don't begin failing soon after, four representative ITk Strips barrel modules were thermally cycled 100 times — this study is also described.

Natural radionuclide and <sup>137</sup>Cs activity concentration in soils of the Brazilian State of Sergipe and their correlation with environmental characteristics

Radionuclides occur naturally in the environment, exposing living organisms to ionizing radiation. In addition, human activities have introduced artificial radionuclides such as 137Cs, among others, into the environment. To better understand the occurrence and behaviour of radionuclides in soil, several countries have developed radiological studies and constructed maps. An effort has been made in Brazil to assess the radioactivity in the soils of the country. In this study, the activity concentrations of natural radionuclides 40K, 226Ra and 228Ra, and artificial 137Cs were determined in samples at a depth of 20 cm collected from the soils of the Brazilian State of Sergipe, in a regular grid of 25 km x 25 km. Samples were analysed by gamma-ray spectrometry with the use of hyperpure germanium detectors. The results were correlated with the type of soil, geology, and climate characteristics of the State. The median activity concentrations of 40K, 226Ra, and 228Ra were 210.4 Bq.kg-1, 12.33 Bq.kg-1, and 18.69 Bq.kg-1, respectively. The results are lower than those reported for soils from other Brazilian States in the same region. The activity concentration of 137Cs was lower than the minimum detectable activity. The activity concentration of 40K in young soils of the semi-arid region was higher than that found in most weathered soils of the rainy regions due to the very low pluviometry of the semi-arid area. Higher activity levels of 226Ra were found in Planosol and for 228Ra it was found in the weathered soils (Acrisol) of the coastal zone. Maps of the distribution of the studied radionuclides were designed. The median value of the outdoor absorbed dose rate in air (Dnat) calculated for the soils of the State of Sergipe is lower when compared with other Brazilian States and the UNSCEAR’s worldwide median value.

Myocardial Perfusion Scintigraphy in Diagnosic of Coronary Heart Disease

<i>Introduction: </i>Atherosclerosis plays a key role in the etiopathogenesis of cardiovascular diseases. Atherosclerosis is a generalized chronic inflammatory disease of the vascular wall, which results in anatomical and histological changes that, together with functional changes, lead to endothelial dysfunction, narrowing of the arterial lumen, and insufficient blood supply to the tissues. The shift in the incidence of cardiovascular diseases to younger age groups is alarming. The presence of microvascular changes in the myocardium is significant. The high incidence of cardiovascular diseases, especially ischemic heart disease, requires early diagnosis and modern treatment. <i>Aim: </i>The aim of the paper is to analyse and point out early diagnosis of coronary heart disease using nuclear medicine methods. <i>Set of examined patients and methodology: </i>Using nuclear medicine methods, we try to detect these changes in time and thus prevent the occurrence of acute coronary events. In nuclear cardiology, instead of a large-area scintillation detector, a new type of cardio-gamma camera "Discovery CZT 530c" based on the principle of semiconductor detectors began to be used. The abbreviation CZT stands for semiconductor composition (Cadmium-Zinc-Tellur). The set of respondents consisted of 4270 people examined in the years 2014-2016 by myocardial perfusion scintigraphy. There were 950 diabetic patients in the analysed group of the 4270 examined. <i>Results:</i> In the analysed group of 4270 respondents, 61% had negative findings and 39% had positive findings in terms of the presence of ischemic heart disease. In the group of diabetic patients, there was a negative finding in 28% of respondents and a positive finding in 72% of the respondents in the sense of positive ischemic heart disease. Using myocardial perfusion scintigraphy in the diagnosis of functional changes, we confirmed a great benefit in detecting early changes in coronary heart disease, including in the diagnosis of microvascular angina. <i>Conclusion:</i> Nuclear medicine methods are of great benefit for the diagnosis of small vessel disease, diabetic cardiomyopathy and cardiac autonomic neuropathy in patients with diabetes mellitus. The new type of cardio gamma camera "Discovery CZT 530c" allows more accurate assessment of myocardial perfusion abnormalities and at the same time the reduction of the radiopharmaceutical dose reduces the patient's radiation load by 50%.

Feasibility study of YSO/SiPM based detectors for virtual monochromatic image synthesis.

The development of photon-counting CT systems has focused on semiconductor detectors like cadmium zinc telluride (CZT) and cadmium telluride (CdTe). However, these detectors face high costs and charge-sharing issues, distorting the energy spectrum. Indirect detection using Yttrium Orthosilicate (YSO) scintillators with silicon photomultiplier (SiPM) offers a cost-effective alternative with high detection efficiency, low dark count rate, and high sensor gain. This work aims to demonstrate the feasibility of the YSO/SiPM detector (DexScanner L103) based on the Multi-Voltage Threshold (MVT) sampling method as a photon-counting CT detector by evaluating the synthesis error of virtual monochromatic images. In this study, we developed a proof-of-concept benchtop photon-counting CT system, and employed a direct method for empirical virtual monochromatic image synthesis (EVMIS) by polynomial fitting under the principle of least square deviation without X-ray spectral information. The accuracy of the empirical energy calibration techniques was evaluated by comparing the reconstructed and actual attenuation coefficients of calibration and test materials using mean relative error (MRE) and mean square error (MSE). In dual-material imaging experiments, the overall average synthesis error for three monoenergetic images of distinct materials is 2.53% ±2.43%. Similarly, in K-edge imaging experiments encompassing four materials, the overall average synthesis error for three monoenergetic images is 4.04% ±2.63%. In rat biological soft-tissue imaging experiments, we further predicted the densities of various rat tissues as follows: bone density is 1.41±0.07 g/cm3, adipose tissue density is 0.91±0.06 g/cm3, heart tissue density is 1.09±0.04 g/cm3, and lung tissue density is 0.32±0.07 g/cm3. Those results showed that the reconstructed virtual monochromatic images had good conformance for each material. This study indicates the SiPM-based photon-counting detector could be used for monochromatic image synthesis and is a promising method for developing spectral computed tomography systems.

Measurement of fast neutron induced (n,γ) reaction cross-section of 68Zn, 96Zr, 121Sb and 123Sb in the energy range of 1 to 2 MeV

The (n,γ) reaction cross-section for the elements 68Zn, 96Zr, 121Sb and 123Sb, present in the reactor structural/shielding materials, was measured by neutron activation technique in the neutron energy region of 1–2 MeV as very limited data is available in this energy range. Further, the neutron spectrum peaks in this energy region for the fast breeder reactors and proposed accelerator driven sub-critical systems. The natural strontium (natSr) element was used as a neutron flux monitor by considering effective combined reaction cross-section for 86Sr(n,γ)87Srm and 87Sr(n,n′)87Srm reactions. The pellets of mixture of sample and monitor were irradiated by a quasi-mono energetic fast neutron beam, generated by 7Li(p,n)7Be reaction at FOTIA, Bhabha Atomic Research Centre, Mumbai, India. The activity of activation products was measured by off-line gamma-ray spectrometry using High Purity Germanium Detector (HPGe). The present data with improved uncertainty and covariance analysis enhance the cross-section data base for better constraining the evaluated data and theoretical models. The theoretical (n,γ) reaction cross-sections were calculated using TALYS 1.96, which could reasonably explain the present data with the Fermi gas level density prescription.

Lightweight thermal management strategies for the silicon detectors of CBM at FAIR

Lightweight thermal management is central to the design of the all-silicon Inner Tracker of the Compressed Baryonic Matter Experiment (CBM) at the Facility for Antiproton and Ion Research (FAIR). This experiment aims to study strongly interacting matter at neutron star core densities through fixed-target Au-Au collisions (sNN=2.9−4.9GeV; up to 107 beam–target interactions per second; polar angular acceptance of 2.5°≤Θ≤25°). Studies with thermal demonstrators for both the pixel-based Micro Vertex Detector and the strip-based Silicon Tracking System have validated their thermal management strategies, preparing them for series production now and global commissioning in 2028.