Performance Of Radiation Detectors Research Articles

Effect of NO annealing on radiation detection performance of Ni/SiO2/4H-SiC MOS capacitors

In this study, Ni/SiO2/4H-SiC metal-oxide-semiconductor (MOS) devices were fabricated, achieving high-energy resolution for alpha particle radiation detection. The SiO2/4H-SiC interface was treated with two different methods: i) annealing in N2 environment, ii) annealing in NO environment. Devices manufactured using the former method show lower dark currents than the latter. This difference is due to a decrease in trap density at the SiO2/4H-SiC interface caused by NO annealing, resulting in a higher barrier height for the device. The NO-30 exhibited a much higher energy resolution of 0.46%@5486 keV compared to 0.95%@5486 keV observed in N2-30, despite both devices exhibiting good energy linearity in response to alpha particles. The SiO2/4H-SiC interface trap density revealed a significant decrease after NO treatment, indicating NO treatment can effectively improve the electrical performance of 4H-SiC MOS devices. CCE analysis showed the NO-30 had a lower surface recombination field (13000 V/cm) compared to N2-30 (35000 V/cm), which improves the charge collection efficiency and energy resolution. This study provides a practical approach for enhancing the energy resolution of 4H-SiC MOS detectors.

Evaluation and applicability of radiation detectors for quantitative assessment of radiation exposure in a 16-MeV electron UHDR linac

Background and purposeThe investigation of the FLASH effect requires experimental accelerators capable of delivering ultra-high dose rate (UHDR) beams. Rapid widespread use of this technology could be achieved by modifying clinical electron linacs, originally designed to deliver megavoltage photon radiation up to a few Gy per minute to the isocenter, to deliver electron beams at 40 Gy/s and beyond. Only limited experience has been reported on the radiation safety of UHDR electron beams. This work aims to evaluate the performance and applicability of radiation detectors to quantitatively assess the radiation exposure in this context. MethodsA Varian TrueBeam linac has been modified to deliver 16-MeV electron UHDR with dose rates up to 3⋅105 Gy/s (instantaneous) and 256 Gy/s (average) at the isocenter and used to investigate the detectors performances. A short-term survey was performed at the first UHDR beam-on with passive and active detectors. Then, a long-term survey was conducted with passive detectors during the first three months of operation of the UHDR linac. Moreover, linearity of detector response, activation of the linac components and secondary radiation inside the bunker were evaluated. ResultsSelected active survey metres were shown to have a linear response for the detection of the ambient radiation outside the bunker when performing pulsed UHDR irradiations. The most critical locations outside the bunker were identified at the bunker door and at the control room. The results showed that the operation of the linac with a workload limit of 1000 Gy/week at the isocenter would allow respecting a limit of 0.02 mSv/week to the personnel. The activation of the linac head with 16-MeV electron beam was more than ten times greater with conventional beams compared to UHDR. The secondary radiation inside the bunker was also reduced by −27% when employing UHDR beams. ConclusionsThis work provides a comprehensive evaluation of the suitability of active and passive detectors to perform a radiation safety assessment for a 16-MeV electron UHDR linac. The conditions under which commonly available survey metres for photons (FLUKE 451P) and neutrons (Ludlum Model 3007) can safely be employed in controlled areas outside the bunker were investigated. Moreover, we showed that if a radiation vault is safe for 16-MeV electron beams at conventional dose rates, this applies also to UHDR when fixing the linac weekly workload to a given amount of dose at the isocenter.

Unsupervised Learning for Improved Gamma-Ray Spectrometry in Pixelated Cadmium Zinc Telluride (CZT) Detectors

Machine learning has been found to be ubiquitously useful across many industries, presenting an opportunity to improve radiation detection performance using data-driven algorithms. Improved detector resolution can aid in the detection, identification, and quantification of radionuclides. In this work, a novel, data-driven, unsupervised learning approach is developed to improve detector spectral characteristics by learning, and subsequently rejecting, poorly performing regions of the pixelated detector. Feature engineering is used to fit individual characteristic photo peaks to a Doniach lineshape with a linear background model. Then, principal component analysis is used to learn a lower-dimension latent space representation of each photo peak where the pixels are clustered, and subsequently ranked, based on the cluster mean distance to an optimal point. Pixels within the worst cluster(s) are rejected to improve the full-width at half-maximum (FWHM) by 10% to 15% (relative to the bulk detector) at 50% net efficiency when applied to training data obtained from measurements of a 100 μCi 154Eu source using a H3D M400i pixelated cadmium zinc telluride detector. These results compare well with, but do not outperform, a greedy algorithm that accumulates pixels in order of FWHM from lowest to highest used as a benchmark. In the future, this approach can be extended to include the detector energy and angular response. Finally, the model is applied to newly seen natural and enriched uranium spectra relevant for nuclear safeguards applications.

Feasibility assessment of polycrystalline CsPbI3 relative dosimeters in photon and electron beam radiotherapy

Volumetric modulated arc therapy represents the latest technology in radiotherapy. It involves continuous modification of the multi-leaf collimator spatial distribution, dose rate, and gantry rotational speed, necessitating a dosimeter with high spatial resolution and exceptional sensitivity per unit volume. In particular, cesium-based inorganic perovskites have been studied for various applications, spanning from photoconductor solar cells to radiation detectors. These perovskites are renowned for their outstanding attributes, including thermal stability, inorganic stability, and light absorption capacity. Despite such advantageous characteristics, CsPbI3 materials have only been investigated in radiodiagnostics, with limited exploration in radiotherapy. To address this gap, this study verified the viability of CsPbI3 materials, note for their outstanding radiation detection efficiency, as dosimeters capable of measuring the radiation detection performance for radiotherapy devices. The reproducibility, linearity, and percent depth dose (PDD) were evaluated under the application of photon and electron beams in linear accelerators. The reproducibility assessment revealed impressive results, with the relative standard deviation registering at 0.53%, 0.32%, and 0.38% under electron beam energies of 6, 9, and 12 MeV and 0.45%, and 0.89% under photon beam energies of 6 and 15 MV. Moreover, the linearity test revealed an R 2 value of 0.9999, indicating high linearity, at 6, 9, and 12 MeV and at 6 and 15 MV. The PDD graphs drawn for the CsPbI3 dosimeter fabricated in this study showed that the D max points were consistent. The novel CsPbI3 dosimeter demonstrated a level of detection performance that satisfied all criteria; reproducibility, linearity, and PDD. The results collectively indicated that the CsPbI3 dosimeter can be used for dosimeters in radiotherapy devices.

An evaluation method for nuclear radiation detection performance of glass scintillator

An evaluation method for nuclear radiation detection performance of glass scintillator

Study on the growth and radiation detection performance of high-efficiency perovskite single crystal

The growth and radiation detection performance of high efficiency perovskite single crystal is studied. First, high-quality perovskite single crystals were successfully prepared by optimizing the growth conditions. Secondly, the structure, optical and electrical properties are characterized in detail, and the single crystal is found to be excellent. Moreover, the application of perovskite single crystal in radiation detection was also studied, and the results showed its high sensitivity, low detection limit and rapid response. This paper provides theoretical basis and experimental support for the application of perovskite single crystal in the field of practical radiation detection.

Preliminary Characterization of an Active CMOS Pad Detector for Tracking and Dosimetry in HDR Brachytherapy.

We assessed the accuracy of a prototype radiation detector with a built in CMOS amplifier for use in dosimetry for high dose rate brachytherapy. The detectors were fabricated on two substrates of epitaxial high resistivity silicon. The radiation detection performance of prototypes has been tested by ion beam induced charge (IBIC) microscopy using a 5.5 MeV alpha particle microbeam. We also carried out the HDR Ir-192 radiation source tracking at different depths and angular dose dependence in a water equivalent phantom. The detectors show sensitivities spanning from (5.8 ± 0.021) × 10-8 to (3.6 ± 0.14) × 10-8 nC Gy-1 mCi-1 mm-2. The depth variation of the dose is within 5% with that calculated by TG-43. Higher discrepancies are recorded for 2 mm and 7 mm depths due to the scattering of secondary particles and the perturbation of the radiation field induced in the ceramic/golden package. Dwell positions and dwell time are reconstructed within ±1 mm and 20 ms, respectively. The prototype detectors provide an unprecedented sensitivity thanks to its monolithic amplification stage. Future investigation of this technology will include the optimisation of the packaging technique.

Kinetic modulation-eliminated precursor liquid inclusions in solution-grown CsPbBr3 bulk crystals for gamma-ray detection

Liquid inclusion defects in CsPbBr3 crystals are attributed to natural convection generated around the crystal surface. Forced convection is introduced to eliminate liquid inclusions, and the crystal achieves high radiation detection performance.

Dual-Core Ce: YAG-Derived Silicate Scintillation Fiber for Real-Time X-Ray Detection

A dual-core Ce:YAG-derived scintillation fiber (DCSF) was proposed conceptually, simulated numerically, and prepared experimentally by the modified molten core method (MCM) for the first time, of which, the core material is amorphous yttrium aluminosilicate glasses and the cladding material SiO2. Theoretically, it is found that such kind of DCSF exhibits very low inter-core crosstalk with the help of finite element simulation analysis, which may result from the high index difference of ∼0.097 between core and cladding. The average decay lifetime of the prepared DCSF are 31.4 ns and 36 ns at 350 nm and 500 nm, which are shorter than those of its Ce:YAG bulk crystal counterpart. Radiation monitoring was demonstrated by an all-fiber detection system. The radiation response of the DCSF bundle was also investigated, whose radio-luminescence response intensity is ∼1.66 and ∼1.12 times higher than that of the single-core fiber bundles with similar core-diameter and with similar core-area, respectively. In conclusion, with radiation detection performance improvement enabled by space division multiplexing capability, the DCSF not only provides a solution for the dilemma between low transmission loss and high optical yield, but also makes a substantial step towards the development of practical and reliable radiation detectors.

Spectrometric performance of SiC radiation detectors at high temperature

In this work, we have investigated the performance of a 4H–SiC radiation sensor in the temperature range from 25 °C to 450 °C to explore its compatibility as detector of fast ion losses in plasma diagnostic of future nuclear fusion reactors. To simulate the escape of fusion-born alpha particles in D-T (deuterium-tritium) fusion plasmas, spectroscopic measurements were carried out in a vacuum chamber by irradiating the detector with a 3.5 MeV alpha beam from a Tandem accelerator. The detector was found to have an energy resolution ≤2% over the entire temperature range analyzed. Relevantly, the excellent spectrometric capabilities of the device have allowed us to calculate from experimental data, with unprecedented accuracy, the average energy required to create a single electron-hole pair in 4H–SiC as a function of temperature.

Passivation effect on Cd0.95Mn0.05Te0.98Se0.02 radiation detection performance

CdTe-based detectors have the problem of Te-rich surface layers caused by Br etching, which is one of fabrication steps. Te-rich layer acts as a trapping center and serves as an additional source of charge carriers, thereby degrading transport property of charge carriers and enriching leakage current on surface of detector. To solve this problem, we introduced sodium hypochlorite (NaOCl) as a passivant, and investigated its effect on Cd0.95Mn0.05Te0.98Se0.02 (CMTS), by analyzing chemical state of surface and its performance. After passivation with NaOCl, the results of X-ray photoelectron spectroscopy (XPS) shows the formation of tellurium oxide and elimination of water on CMTS surface, and CMTS presented enhanced performance with Am-241 radioisotope. Consequently, it is demonstrated that the passivation with NaOCl reduces leakage current, compensates defect, and elevates transport of charge carriers, thereby decreasing charge loss of carriers and improving performance of CMTS detector.

Fast-, Light-Cured Scintillating Plastic for 3D-Printing Applications

Additive manufacturing techniques enable a wide range of possibilities for novel radiation detectors spanning simple to highly complex geometries, multi-material composites, and metamaterials that are either impossible or cost prohibitive to produce using conventional methods. The present work identifies a set of promising formulations of photocurable scintillator resins capable of neutron-gamma pulse shape discrimination (PSD) to support the additive manufacturing of fast neutron detectors. The development of these resins utilizes a step-by-step, trial-and-error approach to identify different monomer and cross-linker combinations that meet the requirements for 3D printing followed by a 2-level factorial parameter study to optimize the radiation detection performance, including light yield, PSD, optical clarity, and hardness. The formulations resulted in hard, clear, PSD-capable plastic scintillators that were cured solid within 10 s using 405 nm light. The best-performing scintillator produced a light yield 83% of EJ-276 and a PSD figure of merit equaling 1.28 at 450–550 keVee.

Quartz tuning fork-based high sensitive photodetector by co-coupling photoelectric and the thermoelastic effect of perovskite.

This paper reports a new strategy for enhancing the photoresponse of a quartz tuning fork (QTF). A deposited light absorbing layer on the surface of QTF could improve the performance only to a certain extent. Herein, a novel strategy is proposed to construct a Schottky junction on the QTF. The Schottky junction presented here consists of a silver-perovskite, which has extremely high light absorption coefficient and dramatically high power conversion efficiency. The co-coupling of the perovskite's photoelectric effect and its related QTF thermoelastic effect leads to a dramatic improvement in the radiation detection performance. Experimental results indicate that the CH3NH3PbI3-QTF obtains two orders of magnitude enhancement in sensitivity and SNR, and the 1σ detection limit was calculated to be 1.9 µW. It was the first time that the QTF resonance detection and perovskite Schottky junction was combined for optical detection. The presented design could be used in photoacoustic spectroscopy and thermoelastic spectroscopy for trace gas sensing.

Towards Extended Gate Field Effect Transistor-Based Radiation Sensors: Impact of Thicknesses and Radiation Doses on Al-Doped Zinc Oxide Sensitivity

Radiation measurements are critical in radioanalytical, nuclear chemistry, and biomedical physics. Continuous advancement in developing economical, sensitive, and compact devices designed to detect and measure radiation has increased its capability in many applications. In this work, we presented and investigated the performance of a cost-effective X-ray radiation detector based on the extended gate field effect transistors (EGFET). We examined the sensitivity of Al-doped Zinc oxide (AZO) of varying thicknesses, fabricated by chemical bath deposition (CBD), following X-ray irradiation with low and high doses. EGFETs were used to connect samples for their detection capabilities. As a function of the absorbed dose, the response was analyzed based on the threshold voltage shift, and the sensitivity of each device was also evaluated. We demonstrated that thin films are less sensitive to radiation than their disk-type EG devices. However, performance aspects of the devices, such as radiation exposure sensitivity and active dosage region, were found to be significantly reliant on the composition and thickness of the materials used. These structures may be a cost-effective alternative for real-time, room-temperature radiation detectors.

Enhancement of radiation detection performance with reduction of EH6/7 deep levels in n-type 4H–SiC through thermal oxidation

We report the effect of EH6/7 electron trap centers alone on the performance of high-resolution radiation detectors fabricated on n-type 4H–SiC epitaxial layers. A Schottky barrier detector (SBD) and a metal-oxide-semiconductor (MOS) capacitor detector fabricated using two sister samples derived from the same 50 μm 4H–SiC parent wafer exhibited widely different energy resolutions of 0.4% and 0.9% for 5486 keV alpha particles. An equivalent noise charge model analysis ruled out the effect of the detector capacitance and the leakage current on the resolution of the detectors. Deep level transient spectroscopic studies revealed the presence of two trapping centers in each detector within the temperature scan range 240–800 K. The Z1/2 center, a potential electron trap, was detected in both the detectors in equal concentration, which suggested that the observed difference in the energy resolution is due to the presence of the other defect, the EH6/7 center, in the SBD. The capture cross section of the EH6/7 center was calculated to be three orders of magnitude higher than the second defect [a carbon antisite vacancy (CAV) center] observed in the MOS detector with an activation energy of 1.10 eV, which accounted for the enhanced electronic trapping in the SBD leading to its poor energy resolution. It has been proposed that the EH6/7 centers in the SBD have likely been reconfigured to CAV pairs during the thermal growth of the silicon dioxide layer in the MOS detector. The proposed formation mechanism of CAV, a stable qubit state for quantum information processing, addresses the outstanding questions related to the role of defect dynamics in their formation.

Scintillation performance of the Ce3+ -activated lithium phosphate glass

Ce3+ -doped phosphate glasses with intense luminescence were reported extensively for radiation detection in recent decades. With the same intension, we fabricated glasses of composition 45P2O5:35Li2O:(10-x)GdI3:5Al2O3:5Ca2CO3:xCeBr3 (x = 1, 2, 3, 5) in molar ratio using conventional technique followed by thermal annealing. The luminescence studies confirmed the energy transfer process from Gd3+ to Ce3+ -ions. The scintillation measurements of the optimized sample were performed under the excitation of α -particles and γ-rays. A photopeak was detected under γ-ray excitation at 662 keV energy from 137Cs source. The estimated absolute light yield was 1600 ± 200 Photons/MeV. The shortest component of the decay time under α -particles and γ -ray excitations was found 32.5 ± 0.3 ns and 39.9 ± 0.4 ns, respectively. In the future, the glass configuration can be engineered to improve radiation detection performance.

Optical Writing and Electro-Optic Imaging of Reversible Space Charges in Semi-Insulating CdTe Diodes.

Deep levels control the space charge in electrically compensated semi-insulating materials. They limit the performance of radiation detectors but their interaction with free carriers can be favorably exploited in these devices to manipulate the spatial distribution of the electric field by optical beams. By using semi-insulating CdTe diodes as a case study, our results show that optical doping functionalities are achieved. As such, a highly stable, flux-dependent, reversible and spatially localized space charge is induced by a line-shaped optical beam focused on the cathode contact area. Real-time non-invasive imaging of the electric field is obtained through the Pockels effect. A simple and convenient method to retrieve the two-dimensional electric field components is presented. Numerical simulations involving just one deep level responsible for the electrical compensation confirm the experimental findings and help to identify the underlying mechanism and critical parameters enabling the optical writing functionalities.

Effect of oxide layer growth conditions on radiation detection performance of Ni/SiO2/epi-4H-SiC MOS capacitors

High resolution radiation detection has been demonstrated using Ni/SiO2/n-4H-SiC metal-oxidesemiconductor vertical capacitors fabricated using highly crystalline 4H-SiC epilayers. The oxide layers have been grown thermally using two different approaches: i) in-air, and ii) oxygen-ambience oxidation. The devices fabricated using the former method exhibited dark currents one order of magnitude higher than that in the latter. The observed difference has been attributed to the back-contact series resistance and capacitance. Regardless of the difference in the device parameters, detectors prepared using both of the methods exhibited very high energy resolutions of ≤0.5% for 5486 keV alpha particles emitted by an 241Am radioisotope. Capacitance mode deep level transient spectroscopic (DLTS) studies revealed similar type of electrically active defects along with Z1/2 and EH5 deep level defects in both the types of devices. The DLTS scans also revealed positive polarity peaks in these devices which indicate emission from minority carrier trap centers. The activation energy corresponding to the peak was found to be ∼1.2 eV which has been assigned to HK3 defects responsible for hole trapping in 4H-SiC. The possibility of appearance of the positive peak due to non-negligible impedance of the back-contact has been ruled out based on the observation that the centroid of the observed peak did not change with detectors having different device parameters.

A portable magnet for radiation biology and dosimetry studies in magnetic fields.

In the current and rapidly evolving era of real-time MRI-guided radiotherapy, our radiation biology and dosimetry knowledge is being tested in a novel way. This paper presents the successful design and implementation of a portable device used to generate strong localized magnetic fields. These are ideally suited for small-scale experiments that mimic the magnetic field environment inside an MRI-linac system, or more broadly MRI-guided particle therapy aswell. A portable permanent magnet-based device employing an adjustable steel yoke and magnetic field focusing cones has been designed, constructed, and tested. The apparatus utilizes two banks of Nd Fe B permanent magnets totaling around 50 kg in mass to generate a strong magnetic field throughout a small volume between two pole tips. The yoke design allows adjustment of the pole tip gap and exchanging of the focusing cones. Further to this, beam portal holes are present in the yoke and focusing cones, allowing for radiation beams of up to 5 5 cm to pass through the region of high magnetic field between the focusing cone tips. Finite element magnetic modeling was performed to design and characterize the performance of the device. Automated physical measurements of the magnetic field components at various locations were measured to confirm the performance. The adjustable pole gap and interchangeable cones allows rapid changing of the experimental set-up to allow different styles of measurements to beperformed. A mostly uniform magnetic field of 1.2 T can be achieved over a volume of at least 3 3 3 cm . This can be reduced in strength to 0.3 T but increased in volume to 10 10 10 cm via removal of the cone tips and/or adjustment of the steel yoke. Although small, these volumes are sufficient to house radiation detectors, cell culture dishes, and various phantom arrangements targeted at examining small radiation field dosimetry inside magnetic field strengths that can be changed with ease. Most important is the ability to align the magnetic field both perpendicular to, or inline with, the radiation beam. To date, the system has been successfully used to conduct published research in the areas of radiation detector performance, lung phantom dosimetry, and how small clinical electron beams behave in these strong magneticfields. A portable, relatively inexpensive, and simple to operate device has successfully been constructed and used for performing radiation oncology studies around the theme of MRI-guided radiotherapy. This can be in either inline and perpendicular magnetic fields of up to 1.2 T with x-ray and particlebeams.

Performance of 4h-Sic Radiation Detector after High Flux Proton and Fe13+ Heavy Ion Beam Irradiation

Performance of 4h-Sic Radiation Detector after High Flux Proton and Fe13+ Heavy Ion Beam Irradiation