High-energy Detectors Research Articles

Hybrid spectral CT system with clinical rapid kVp-switching x-ray tube and dual-layer detector for improved iodine quantification.

Spectral computed tomography (CT) is a powerful diagnostic tool offering quantitative material decomposition results that enhance clinical imaging by providing physiologic and functional insights. Iodine, a widely used contrast agent, improves visualization in various clinical contexts. However, accurately detecting low-concentration iodine presents challenges in spectral CT systems, particularly crucial for conditions like pancreatic cancer assessment. In this study, we present preliminary results from our hybrid spectral CT instrumentation which includes clinical-grade hardware (rapid kVp-switching x-ray tube, dual-layer detector). This combination expands spectral datasets from two to four channels, wherein we hypothesize improved quantification accuracy for low-dose and low-iodine concentration cases. We modulate the system duty cycle to evaluate its impact on quantification noise and bias. We evaluate iodine quantification performance by comparing two hybrid weighting strategies alongside rapid kVp-switching. This evaluation is performed with a polyamide phantom containing seven iodine inserts ranging from 0.5 to 20 mg/mL. In comparison to alternative methodologies, the maximum separation configuration, incorporating data from both the 80 kVp, low photon energy detector layer and the 140 kVp, high photon energy detector layer produces spectral images containing low quantitative noise and bias. This study presents initial evaluations on a hybrid spectral CT system, leveraging clinical hardware to demonstrate the potential for enhanced precision and sensitivity in spectral imaging. This research holds promise for advancing spectral CT imaging performance across diverse clinical scenarios.

Searching for long faint astronomical high energy transients: a data driven approach

HERMES Pathfinder is an in-orbit demonstration consisting of a constellation of six 3U nano-satellites hosting simple but innovative detectors for the monitoring of cosmic high-energy transients. The main objective of HERMES Pathfinder is to prove that accurate position of high-energy cosmic transients can be obtained using miniaturized hardware. The transient position is obtained by studying the delay time of arrival of the signal to different detectors hosted by nano-satellites on low-Earth orbits. In this context, we need to develop novel tools to fully exploit the future scientific data output of HERMES Pathfinder. In this paper, we introduce a new framework to assess the background count rate of a spaceborne, high energy detector; a key step towards the identification of faint astrophysical transients. We employ a neural network to estimate the background lightcurves on different timescales. Subsequently, we employ a fast change-point and anomaly detection technique called Poisson-FOCuS to identify observation segments where statistically significant excesses in the observed count rate relative to the background estimate exist. We test the new software on archival data from the NASA Fermi Gamma-ray Burst Monitor (GBM), which has a collecting area and background level of the same order of magnitude to those of HERMES Pathfinder. The neural network performances are discussed and analyzed over period of both high and low solar activity. We were able to confirm events in the Fermi-GBM catalog, both solar flares and gamma-ray bursts, and found events, not present in Fermi-GBM database, that could be attributed to solar flares, terrestrial gamma-ray flashes, gamma-ray bursts and galactic X-ray flashes. Seven of these are selected and further analyzed, providing an estimate of localisation and a tentative classification.

DEVELOPMENT OF A SOFTWARE AND TECHNICAL COMPLEX FOR A TWO-CHANNEL DETECTING SYSTEM FOR CONTINUOUS REGISTRATION OF X-RAY AND GAMMA RADIATION

A compact spectrometric tract and software for work as part of a two-channel detecting system for continuous registration of X-ray and gamma radiation in a wide range of energies have been developed. The complex is designed to work with silicon planar uncooled detectors. The software allows you to process information from each spectrometric channel and provide information in the form of a integrated spectrum. The design of the detecting module, which combines low-energy and high-energy detectors in one housing has been developed.

Insight-HXMT Detections of Hard X-Ray Tails in Scorpius X-1

Using the observations of the high-energy detector of the Hard X-ray Modulation Telescope (Insight-HXMT) for Scorpius X-1 from 2017 to 2020, we search for hard X-ray tails in the X-ray spectra in ∼30–200 keV. The hard X-ray tails are found throughout the Z-track on the hardness–intensity diagram, and the detected hard X-ray tails become hard and weak from the horizontal branch (HB), through the normal branch (NB), to the flaring branch (FB). Comparing the hard X-ray spectra of Insight-HXMT between Cyg X-1 and Sco X-1, it is concluded that the hard X-ray spectrum of Cyg X-1 shows a high-energy cutoff, implying a hot corona in it, but the high-energy cutoff is not seen in the hard X-ray spectrum of Sco X-1. From fitting the broadband spectrum of Sco X-1 in ∼2–200 keV, it is proposed that the hard X-ray tails in the HB and NB can be explained by the overall Comptonization COMPTB model, suggesting that the hard X-ray tails could have resulted from the Comptonization of the photons from the neutron star (NS) surface by the thermal electrons in the region between the NS and the disk and the energetic electrons in the freefall toward the NS in the converging flow onto the NS. However, this model cannot be responsible for the hard X-ray tails in the FB. Further study on the FB hard X-ray tails is needed.

GRB minimum variability timescale with Insight-HXMT andSwift

Context.There has been significant technological and scientific progress in our ability to detect, monitor, and model the physics ofγ-ray bursts (GRBs) over the 50 years since their first discovery. However, the dissipation process thought to be responsible for their defining prompt emission is still unknown. Recent efforts have focused on investigating how the ultrarelativistic jet of the GRB propagates through the progenitor’s stellar envelope for different initial composition shapes, jet structures, magnetisation, and, consequently, possible energy dissipation processes. Study of the temporal variability – in particular the shortest duration of an independent emission episode within a GRB – may provide a unique way to distinguish the imprint of the inner engine activity from geometry and propagation related effects. The advent of new high-energy detectors with exquisite time resolution now makes this possible.Aims.We aim to characterise the minimum variability timescale (MVT) defined as the shortest duration of individual pulses that shape a light curve for a sample of GRBs in the keV–MeV energy range and test correlations with other key observables such as the peak luminosity, the Lorentz factor, and the jet opening angle. We compare these correlations with predictions from recent numerical simulations for a relativistic structured – possibly wobbling – jet and assess the value of temporal variability studies as probes of prompt-emission dissipation physics.Methods.We used the peak detection algorithmMEPSAto identify the shortest pulse within a GRB time history and preliminarily calibratedMEPSAto estimate the full width at half maximum duration. We then applied this framework to two sets of GRBs:SwiftGRBs (from 2005 to July 2022) and Insight Hard Modulation X-ray Telescope (Insight-HXMT) GRBs (from June 2017 to July 2021, including the exceptional 221009A). We then selected 401 GRBs with measured redshift to test for correlations.Results.We confirm that, on average, short GRBs have significantly shorter MVTs than long GRBs. The MVT distribution of short GRBs with extended emission such as 060614 and 211211A is compatible only with that of short GRBs. This is important because it provides a new clue concerning the progenitor’s nature. The MVT for long GRBs with measured redshift anti-correlates with peak luminosity; our analysis includes careful evaluation of selection effects. We confirm the anti-correlation with the Lorentz factor and find a correlation with the jet opening angle as estimated from the afterglow light curve, along with an inverse correlation with the number of pulses.Conclusions.The MVT can identify the emerging putative new class of long GRBs that are suggested to be produced by compact binary mergers. For otherwise typical long GRBs, the different correlations between MVT and peak luminosity, Lorentz factor, jet opening angle, and number of pulses can be explained within the context of structured, possibly wobbling, weakly magnetised relativistic jets.

Burst Phase Distribution of SGR J1935+2154 Based on Insight-HXMT

On 2020 April 27, the soft gamma-ray repeater SGR J1935+2154 entered its intense outburst episode again. Insight-HXMT carried out about one month observation of the source. A total number of 75 bursts were detected during this activity episode by Insight-HXMT, and persistent emission data were also accumulated. We report on the spin period search result and the phase distribution of burst start times and burst photon arrival times of the Insight-HXMT high energy detectors and Fermi/Gamma-ray Burst Monitor (GBM). We find that the distribution of burst start times is uniform within its spin phase for both Insight-HXMT and Fermi/GBM observations, whereas the phase distribution of burst photons is related to the type of a burst’s energy spectrum. The bursts with the same spectrum have different distribution characteristics in the initial and decay episodes for the activity of magnetar SGR J1935+2154.

Updates for automatic analysis and post-processing of JET neutral particle analysers for TT and DT campaigns

The data processing from both JET Neutral Particle Analysers (NPAs), high energy and low energy detector systems, has been updated for needs of operating in different scenarios with several isotopes in tritium and deuterium plasmas in the 2021 campaigns. The new automatic processing allows quick routine analysis of NPA data during JET experiments and enables efficient further analysis of large data sets with the help of coupling to the JETPEAK database. The analysis of the NPA data can be now performed as a standard way reliably in intershot and avoid misunderstanding and misusing the data. The NPA data analysis workflow has been systematically applied and demonstrated during scenario development experiments in 2020. This contribution introduces the capability and efficiency of the coupled analysis chain in fast particle diagnostics data checks and post-processing by using JET DTE2 reference pulse sub-database.

Insight-HXMT measurements of the diffuse X-ray background

ABSTRACT We present an X-ray spectrum of the diffuse X-ray background (DXRB) between 1.5 and 120 keV, as measured with the Low-Energy Detector (LE) and the High-Energy Detector (HE) aboard the Insight-HXMT satellite, based on ’blank-sky’ observations. LE covers a nominal energy range of 1–15 keV and HE 20–250 keV, but calibration issues and data quality narrowed the energy range for this work. The LE background was directly measured with ‘blind’ detector modules, while the HE background was derived from Earth-occultation data. With the LE data alone, the measured DXRB spectrum can be well-described by a power law; fitting the LE and HE data jointly, however, a spectral cut-off must be introduced in the model to account for the measurements above 30 keV. Modelling the combined spectrum with a cut-off power law, the best-fitting photon index is 1.40, normalization 9.57 $\rm ph~cm^{-2}\,s^{-1}\,keV^{-1}\,sr^{-1}$ (at 1 keV), and cut-off energy 55 keV after correcting for the effects of the Earth albedo and atmospheric emission (which are significant in the HE band). Based on the best-fitting cut-off power law, we derived the spectral energy distribution (SED) of the DXRB. The shape of the SED is in general agreement with the published measurements, but the overall normalization is lower by varying amounts, except for the HEAO-1 result, with which our result is in good agreement.

Galactic and extragalactic sources of very high energy gamma rays

Very high energy $$\gamma $$ -rays are one of the most important messengers of the relativistic non-thermal Universe. The major motivation of very high energy $$\gamma $$ -ray astronomy is to find sources of high energy cosmic rays. Several astrophysical sources are known to accelerate cosmic rays to very high energies under extreme conditions. Very high energy $$\gamma $$ -rays are produced at these astrophysical sites or in their vicinity through interactions of cosmic rays in the surrounding medium close to the sources. Gamma rays, being neutral, travel in a straight line and thus give us valuable information about the cosmic ray sources and their surroundings. Additionally, very high energy $$\gamma $$ -ray astronomy can probe many fundamental physics questions. Ground-based $$\gamma $$ -ray astronomy began its journey in 1989 when Whipple telescope detected TeV $$\gamma $$ -rays from the Crab, a pulsar wind nebula in our galaxy. In the last 2 decades, technological improvements have facilitated the development of the latest generation of very high energy detectors and telescopes which have delivered exciting new results. Until now, over two hundred very high energy $$\gamma $$ -ray sources, both galactic and extra-galactic, have been detected. These observations have provided a deeper insight into a large number of important questions in high energy astrophysics and astroparticle physics. This review article is an attempt to enumerate the most important results in the exciting and rapidly developing field of very high energy $$\gamma $$ -ray astronomy.

Robust Analog Multi-Sensory Array System for Lossy Capacitive Sensors Over Long Distances

A robust capacitive multi-sensory readout system is presented in this paper. The system consists of a few thousand lossy capacitive-based sensors which can be modeled as a parallel connection of sensor capacitor and undesirable leakage resistance. The real system in our application will consist of a high number of capacitive sensors used for the monitoring of relative humidity in a High Energy detector at CERN. However, our findings apply to any set of capacitive devices aimed to any other sensing application. Furthermore, the proposed system is intended for harsh environments (e.g. with high radiation levels and magnetic field presence) where the readout system is separated from the sensor and placed far away, connecting to them via cables. In such cases, the presence of cables brings another issue to the readout system – parasitic capacitance. Using long cables, we introduce high values of parasitic capacitance that make the sensor capacitance practically invisible to the readout unit. This paper presents an effective, robust, analog method, based on a quadrature-phase shifter and an auto-balancing bridge, used to overcome the sensor leakage resistance and parasitic capacitance caused by the cables. The experiments for various values of capacitance and leakage resistance at different frequencies and the influence of different cable lengths and types are analyzed and discussed.

Absolute time calibration of LAXPC aboard AstroSat

The AstroSat mission carries several high-energy detectors meant for fast timing studies of cosmic sources. In order to carry out high precision multi-wavelength timing studies, it is essential to calibrate the absolute time stamps of these instruments to the best possible accuracy. We present here the absolute time calibration of the AstroSat LAXPC instrument, utilising the broad-band electromagnetic emission from the Crab Pulsar to cross calibrate against Fermi-LAT and ground based radio observatories Giant Metrewave Radio Telescope (GMRT) and the Ooty Radio Telescope (ORT). Using the techniques of pulsar timing, we determine the fixed timing offsets of LAXPC with respect to these different instruments and also compare the offsets with those of another AstroSat instrument, CZTI.

Design of a High-Energy and High-Resolution detector for X-ray computed tomography

The Nuclear Measurement Laboratory (LMN) at CEA Cadarache in France is developing a high-energy tomograph reaching energies up to 21 MeV with high dose rates. It allows performing tomographies on massive objects (5 tons, 140 cm diameter) with a multimillimetric spatial resolution. For the control of absence of cracks, bubbles or defects in the concrete coating of some CEA waste drums, the laboratory needs a “high-resolution” version of this tomograph. The purpose of this study is to design an imaging detector able to provide a high spatial resolution on large objects with high dose resistance and scanning times of a few hours. To achieve this design, several steps are necessary and will be presented: – A first step consists in characterizing the current detection elements of the tomograph, such as the camera and its lens with experimental measurements. This enables to compare performance of these elements with that available on the market and to consider a replacement. – Then, the scintillator is selected according to experimental measurements on few scintillator types and a state of the art. – Next, the detector configuration is optimized to achieve the higher spatial resolution. Throughout these steps, we present the design of a highresolution detector with a spatial resolution around 300 µm for a 10%contrast.

Preparation and Properties of CdZnTe Thick Film on Doped ZnO Film Substrates

Cadmium zinc telluride (CdZnTe) is considered to be an ideal material for manufacturing high-energy radiation detectors with large scale and long-term stability. To solve the problem of film fragmentation during the process of preparing CdZnTe thick films using the close-spaced sublimation method, Ga-doped ZnO (GZO) was chosen as the substrate for CdZnTe film growth, since it has a similar thermal expansion coefficient, lower lattice mismatch, and better adhesion compared with CdZnTe. For comparison, borosilicate glass and fluorine-doped tin oxide substrates were also used to deposit CdZnTe under the same preparation conditions. The structure and physical properties of the CdZnTe film were investigated in detail by using atomic force microscopy, scanning electron microscopy, energy-dispersive spectrometry, x-ray diffraction analysis, and current–voltage (I–V) measurements. The results indicated that CdZnTe film grown on GZO film substrate has large grain size, high growth rate, high quality, and good adhesion.

Control of crystal morphology in energetic drop-on-demand inkjet method

Nano-energetic materials have attracted the worldwide attention since they play an important role in fabricating insensitive high-energy explosives, micro-energetic devices, and explosive detectors. Here, we report a simple, but an effective strategy to control droplet coalescence during inkjet printing, as a major variable, to tailor the nanoscale morphology of energetic materials produced upon evaporation of all-liquid inks. We expect to achieve energetic materials with nanoscale particles by integrating the deposition and the nanocrystallisation of energetic droplets in one step. A proprietary uniform energetic micro-droplet printing equipment is utilised to reveal the influence of temperature, frequency on the particle size of energetic materials. Uniform line, with the particle size between nanometre and microns, is successfully obtained, showing the feasibility of the proposed method for preparing the microscale charge of nano-energetic materials. We also discussed the effect of droplet coalescence on the crystal morphology.

Simulation of cosmic rays in the Earth’s atmosphere and interpretation of observed counts in an X-ray detector at balloon altitude near tropical region

The study of secondary particles produced by the cosmic-ray interaction in the Earth’s atmosphere is very crucial as these particles mainly constitute the background counts produced in the high-energy detectors at balloon and satellite altitudes. In the present work, we calculate the abundance of cosmic-ray generated secondary particles at various heights of the atmosphere by means of a Monte Carlo simulation and use this result to understand the background counts in our X-ray observations using balloon-borne instruments operating near the tropical latitude (geomagnetic latitude: ~14.50°N). For this purpose, we consider a 3D description of the atmospheric and geomagnetic field configurations surrounding the Earth, as well as the electromagnetic and nuclear interaction processes using Geant4 simulation toolkit. Subsequently, we use a realistic mass model description of the detector under consideration, to simulate the counts produced in the detector due to secondary cosmic-ray particles.

Overcoming the challenges of high-energy X-ray ptychography.

X-ray ptychography is a coherent diffraction imaging technique with a high resolving power and excellent quantitative capabilities. Although very popular in synchrotron facilities nowadays, its implementation with X-ray energies above 15 keV is very rare due to the challenges imposed by the high energies. Here, the implementation of high-energy X-ray ptychography at 17 and 33.6 keV is demonstrated and solutions to overcome the important challenges are provided. Among the particular aspects addressed are the use of an efficient high-energy detector, a long synchrotron beamline for the high degree of spatial coherence, a beam with 1% monochromaticity providing high flux, and efficient multilayer coated Kirkpatrick-Baez X-ray optics to shape the beam. The constraints imposed by the large energy bandwidth are carefully analyzed, as well as the requirements to sample correctly the high-energy diffraction patterns with small speckle size. In this context, optimized scanning trajectories allow the total acquisition time to be reduced by up to 35%. The paper explores these innovative solutions at the ID16A nano-imaging beamline by ptychographic imaging of a 200 nm-thick gold lithography sample.

Epitaxial growth and characterization of Cd1−xMnxTe films on Si(1 1 1) substrates

Semiconductors structures with high quality and low cost have been developed and applied in industry on a large scale. The knowledge of basic properties of semiconductor materials growth is important for many technological applications. Cd1-xMnxTe films have been used successfully in optoelectronic, solar cells and high energy detectors applications. However, despite the high potential for application of these films, fundamental growth studies on Si(1 1 1) substrate are not extensively explored. In this study, two Cd1−xMnxTe (CMT) films (with different Mn concentrations) were successfully prepared on Si(1 1 1) substrate employing molecular beam epitaxy. The morphology and surface roughness of the films were investigated using atomic force microscopy (AFM). X-ray diffraction was used to investigate the structural quality and to determine the Mn concentration of the samples. It shows that the films have only (1 1 1) orientation despite a lattice mismatch of almost 19%. Room temperature micro-photoluminescence (µ-PL) spectra shows a high intensity band edge emission and very low intensity defect related emission. Raman spectroscopy of the samples was carried out in order to obtain the vibrational modes. First, second and third order CdTe-like and MnTe-like longitudinal-optical (LO) phonon modes were observed. These results demonstrate the potential of these structures for room temperature applications.

Particle identification with DIRCs at PANDA

The DIRC technology (Detection of Internally Reflected Cherenkov light) offers an excellent possibility to minimize the form factor of Cherenkov detectors in hermetic high energy detectors. The PANDA experiment at FAIR in Germany will combine a barrel-shaped DIRC with a disc-shaped DIRC to cover an angular range of 5 to 140 degrees. Particle identification for pions and kaons with a separation power of 3 standard deviations or more will be provided for momenta between 0.5 GeV/c and 3.5 GeV in the barrel region and up to 4 GeV/c in the forward region. Even though the concept is simple, the design and construction of a DIRC is challenging. High precision optics and mechanics are required to maintain the angular information of the Cherenkov photons during multiple internal reflections and to focus the individual photons onto position sensitive photon detectors. These sensors must combine high efficiencies for single photons with low dark count rates and good timing resolution at high rates. The choice of radiation hard fused silica for the optical material and of MCP-PMT photon sensors is essential for DIRC detectors to survive in an environment of radiation and strong magnetic field. The two DIRC detectors differ in the focusing optics, in the treatment of chromatic dispersion and in the electronic readout systems. The technical design of the two DIRC detectors and their validation by testing prototypes in a mixed particle beam at CERN are presented.

Studies of photon interaction and shielding parameters of lead alumino-borophosphate glass system

The photon interaction parameters viz. Mass attenuation coefficient (μm), effective atomic number (Zeff), effective electron density (Ne), Half Value Layer (HVL) and Mean Free Path (MFP) of xPbO−(40−0.5x)B2O3−(40−0.5x)P2O5−9.0Na2O−1.0Al2O3−9.6ZnO−0.2Sm2O3−0.2Gd2O3(x=10,15,20,25,30,35) of glass system are measured at energies 59.54 keV, 356 keV, 662 keV, 1173 keV and 1333 keV. Scintillation detector [NaI(Tl), 3'×3' has been used for these measurements. The experimental values of μm have been compared with the values obtained with the help of WinXcom and the comparison shows a good agreement of the values with each other within experimental uncertainties of 3.5%. The parameters μm, Zeff and Ne are energy dependent and vary from the higher value at lower energy to the lower value at higher energy. The values of HVL and MFP fall from 67% to 42% with the increase of Pb concentration whereas these values rise with the increase in incident photon energies from 59.54 keV to 1333 keV. This suggests that the presence of PbO improves the radiation shielding properties of lead alumino-borophosphate glasses. This study is usefulness to explore the feasibility of borophosphate glasses for developing high energy radiation sensors and detectors.

The high-energy particle package onboard CSES

The China Seismo-Electromagnetic Satellite (CSES) aims to monitor space electromagnetic fields, ionospheric plasma, high-energy charged particles and other features of the global space environment. The high-energy particle package (HEPP), which can effectively detect the energy spectrum, flux and pitch angle distribution of space electrons and protons, and soft X-ray emission from solar flares, is one of the main payloads of CSES. In this study, we designed, developed and calibrated the high-energy particle package and launched it into orbit with CSES. HEPP consists of the high-energy detector (HEPP-H), the low-energy detector (HEPP-L), and the solar X-ray monitor (HEPP-X). The three sub-detectors mainly use silicon detector and crystal calorimeter detection technology. Before launching, we calibrated the three sub-detectors in detail by using radiation source and accelerator beam. All the three sub-detectors have good energy linearity. After launching into orbit, the space energetic particles and X-ray distribution detected by HEPP are consistent with expectations. The performance indices of the detector reach the advanced level of the same kind of detector in the world. HEPP has a wide energy detection range, good energy resolution and high angular resolution ability for electrons and protons. It will play an important role in the study of space particle response and space physics of seismic activity.