MeV Energy Range Research Articles

Radiation Shielding Properties of B2O3-ZnO-BaO-TiO2-Bi2O3 Glass System: A Study on Eu-152 Radiation

Abstract The focus of this investigation is the evaluation of the B₂O₃-ZnO-BaO-TiO₂-Bi₂O₃ glasses' radiation shielding properties within the 0.122–0.867 MeV energy range. A 0.75 cm thickness glass's radiation protection efficiency (RPE) was evaluated, revealing that the higher Bi₂O₃ content glass exhibits superior RPE compared to the other samples. The RPE of the glasses at 0.245 MeV are equal to 73 and 83% for the 18 and 30 Bi2O3 mol % glasses, respectively. The transmission factor (TF) results demonstrated that increased glass thickness leads to a reduction in TF values, leading to higher attenuation. The TF values at 0.296 MeV are 40, 22, and 14% for 0.75, 1.25 and 1.6 cm thickness, respectively. It was revealed that the higher Bi2O3 content glass has the lowest TF values. The TF values at 0.245 MeV are 27, 23, 19 and 17% for the 18, 22, 26, and 30 Bi2O3 mol % samples, respectively. At 0.245 MeV, the effective atomic number values are 40.32, 42.45, 48.58, and 48.81 for the 16, 22, 26, and 30 Bi2O3 mol % samples, respectively,

Multispacecraft Observations of Protons and Helium Nuclei in Some Solar Energetic Particle Events toward the Maximum of Cycle 25

The intricate behavior of particle acceleration and transport mechanisms complicates the overall efforts in formulating a comprehensive understanding of solar energetic particle (SEP) events; these efforts include observations of low-energy particles (from tens of keV to hundreds of MeV) by space-borne instruments and measurements by the ground-based neutron monitors of the secondary particles generated in the Earth atmosphere by SEPs in the GeV range. Numerous space-borne missions provided good data on the nature/characteristics of these solar particles in past solar cycles, but more recently—concurrently with the rise toward the maximum of solar cycle 25—the High-Energy Particle Detector (HEPD-01) proved to be well suited for the study of solar physics and space weather. Its nominal 30–300 MeV energy range for protons can enlarge the detection capabilities of solar particles at low Earth orbit, closer to the injection limit of many SEP events. In this work, we characterize three SEP events within the first six months of 2022 through spectral and velocity dispersion analysis, assessing the response of HEPD-01 to >M1 events.

The Northern Cross Fast Radio Burst project

Context. Fast radio bursts (FRBs) are energetic, millisecond-duration radio pulses observed at extragalactic distances and whose origins are still a subject of heated debate. A fraction of the FRB population have shown repeating bursts, however it’s still unclear whether these represent a distinct class of sources. Aims. We investigated the bursting behaviour of FRB 20220912A, one of the most active repeating FRBs known thus far. In particular, we focused on its burst energy distribution, linked to the source energetics, and its emission spectrum, with the latter directly related to the underlying emission mechanism. Methods. We monitored FRB 20220912A at 408 MHz with the Northern Cross radio telescope and at 1.4 GHz using the 32-m Medicina Grueff radio telescope. Additionally, we conducted 1.2 GHz observations taken with the upgraded Giant Meter Wave Radio Telescope (uGMRT) searching for a persistent radio source coincident with FRB 20220912A, and included high energy observations in the 0.3–10 keV, 0.4–100 MeV and 0.03–30 GeV energy range. Results. We report 16 new bursts from FRB 20220912A at 408 MHz during the period between October 16th 2022 and December 31st 2023. Their cumulative spectral energy distribution follows a power law with slope αE = −1.3 ± 0.2 and we measured a repetition rate of 0.19 ± 0.03 hr−1 for bursts having a fluence of ℱ ≥ 17 Jy ms. Furthermore, we report no detections at 1.4 GHz for ℱ ≥ 20 Jy ms. These non-detections imply an upper limit of β < −2.3, with β being the 408 MHz – 1.4 GHz spectral index of FRB 20220912A. This is inconsistent with positive β values found for the only two known cases in which an FRB has been detected in separate spectral bands. We find that FRB 20220912A shows a decline of four orders of magnitude in its bursting activity at 1.4 GHz over a timescale of one year, while remaining active at 408 MHz. The cumulative spectral energy distribution (SED) shows a flattening for spectral energy Eν ≥ 1031 erg Hz−1, a feature seen thus far in only two hyperactive repeaters. In particular, we highlight a strong similarity between FRB 20220912A and FRB 20201124A, with respect to both the energy and repetition rate ranges. We also find a radio continuum source with 240 ± 36 μJy flux density at 1.2 GHz, centered on the FRB 20220912A coordinates. Finally, we place an upper limit on the γ to radio burst efficiency η to be η < 1.5 × 109 at 99.7% confidence level, in the 0.4–30 MeV energy range. Conclusions. The strong similarity between the cumulative energy distributions of FRB 20220912A and FRB 20201124A indicate that bursts from these sources are generated via similar emission mechanisms. Our upper limit on β suggests that the spectrum of FRB 20220912A is intrinsically narrow-band. The radio continuum source detected at 1.2 GHz is likely due to a star formation environment surrounding the FRB, given the absence of a source compact on millisecond scales brighter than 48 μJy beam−1. Finally, the upper limit on the ratio between the γ and radio burst fluence disfavours a giant flare origin for the radio bursts unlike observed for the Galactic magnetar SGR 1806-20.

Candidate-nuclei for observation of a bound dineutron. Part II: The (n,2n + n) and (γ,2n) nuclear reactions

This is a second part of a survey for stable isotopes in the mass range 90 < A < 210, to find candidates showing the bound dineutron nuclear reaction output channel after irradiation with neutrons or photons. To this end, the neutron capture reaction cross sections were calculated in the (0 - 30) MeV energy range with the TALYS-2.0 code for nuclei in the outgoing channel, which are expected to host bound dineutrons. This study was performed to find appropriate candidates to observe bound dineutron decay meeting the criteria based on the (n, γ) resonance cross section analysis. This study opens up a new direction in dineutron research with the (n, n2+n) and (γ, n2) nuclear reactions.

Reviving MeV-GeV indirect detection with inelastic dark matter

Thermal relic dark matter below ∼10 GeV is excluded by cosmic microwave background data if its annihilation to visible particles is unsuppressed near the epoch of recombination. Usual model-building measures to avoid this bound involve kinematically suppressing the annihilation rate in the low-velocity limit, thereby yielding dim prospects for indirect detection signatures at late times. In this work, we investigate a class of cosmologically viable sub-GeV thermal relics with late-time annihilation rates that are detectable with existing and proposed telescopes across a wide range of parameter space. We study a representative model of inelastic dark matter featuring a stable state χ1 and a slightly heavier excited state χ2 whose abundance is thermally depleted before recombination. Since the kinetic energy of dark matter in the Milky Way is much larger than it is during recombination, χ1χ1→χ2χ2 upscattering can efficiently regenerate a cosmologically long-lived Galactic population of χ2, whose subsequent coannihilations with χ1 give rise to observable gamma-rays in the ∼1 MeV−100 MeV energy range. We find that proposed MeV gamma-ray telescopes, such as e-ASTROGAM, AMEGO, and MAST, would be sensitive to much of the thermal relic parameter space in this class of models and thereby enable both discovery and model discrimination in the event of a signal at accelerator or direct detection experiments. Published by the American Physical Society 2024

Fabrication of Quasi-Sinusoidal Surface Relief Optical Transmission Gratings in Pyrex and IOG Glasses by Implantation with Oxygen and Nitrogen Ion Microbeams of the 5-6 MeV Energy Range.

A method for the fabrication of high diffraction efficiency optical transmission gratings with quasi-sinusoidal profile in glasses by microbeams of medium-mass ions of 5-6 MeV energy was devised and demonstrated. Gratings with a 30 μm grating constant have been manufactured and characterized by interference microscopy and microprofilometry. The obtained surface profiles of the gratings were found to be quasi-sinusoidal with up to 265 nm amplitude. Measured highest first-order diffraction efficiencies were around 26% in both Pyrex and IOG glasses. Such gratings could serve as coupling elements in integrated optics and photonic integrated circuits.

Preparation and radiation shielding features of high density, transparent borosilicate glasses with different Bi2O3 contents

This work assessed highly effective bismuth borosilicate glasses' nuclear radiation shielding capabilities in terms of different concentrations of Bi2O3. Melt-quenching was the method used to create the glasses. The Phy-X/PSD program was used to compute the μm values. The bismuth borosilicate glasses' nuclear radiation shielding properties were determined in the 0.015–15 MeV energy range. Increasing Bi₂O₃ concentration resulted in an increase in mass attenuation coefficient, linear attenuation coefficient, and effective atomic number. Conversely, the half value layer and mean free path values decreased. The B48Bi17 sample, with its largest Zeff, is a great gamma attenuator. The results of a new study may help to clarify the nature of the Bi2O3 additive used in borosilicate glasses, which are a potential form of shield for use in industrial and medical radiation facilities.

Efficacy of barium and calcium additives in lithium silicate glasses for nuclear shielding applications

This study presents a detailed investigation into the nuclear radiation shielding capabilities of lithium silicate (Li2O-SiO2) glass systems, specifically examining the impact of doping with barium oxide (BaO) and calcium oxide (CaO). Utilizing advanced simulation tools, including PAGEX and SRIM for charged particle interactions, and Phy-X/PSD for gamma-ray attenuation analysis, the radiation shielding effectiveness of BaO-based and CaO-based lithium silicate glasses were systematically compared. The gamma attenuation parameters (LAC, MAC, TVL, HVL, EBF, EABF, MFP, Zeff, Neff, FNRCS, and Zeq) of investigated glass samples were computed via the Phy-X/PSD program (15 keV-15 MeV energy). The HVL values vary between 0.007–14.203 cm, and the TVL values vary between 0.054–47.182 cm for all samples in the selected energy range. The highest and lowest values of FNRCS were observed for samples BaO20 and CaO5, with the values 0.093 and 0.1 cm−1, respectively. KERMAs were calculated using PAGEX software between the 1.5 keV and 20 MeV energy range, with the highest KERMA obtained for the BaO20 sample at 0.05 MeV and the lowest KERMA obtained for the CaO5 sample at the lowest density. The mass stopping power quantities were computed between 1 keV-10 GeV energy with PAGEX. The projected range values were calculated with SRIM codes. The lowest projected range values for both alpha particles and protons were obtained for the BaO20 sample with maximum density (3.391 g cm−3). The sample with BaO20 code showed better shielding potential for alpha and proton particles with lower values of projected range and mass stopping power. Findings reveal that the Li2O-BaO-SiO2 glass composition exhibits superior gamma-ray attenuation properties compared to its CaO-doped counterpart, with the BaO20 sample demonstrating particularly enhanced performance.

High-energy heavy ions as a tool for production of nanoporous graphene

Single-layered supported graphene sheets were irradiated by iodine, copper, silicon, and oxygen ions in the MeV energy range. The selected ion beams cover a wide range of nuclear and electronic stopping powers. Raman spectroscopy used for the analysis of irradiated graphene samples reveals similar, nanometer-sized, pores due to the ion impacts, but with varying probability of their formation. We observed an inverse relationship between ion velocity and the size of the nanopores. Also, we observed damage accumulation is influenced by electronic stopping in all cases when electronic stopping is greater than nuclear stopping by two orders of magnitude. The systematic investigation presented in this work enables custom-made production of nanoporous graphene using high-energy heavy ion beams.

The role of ZnO in the radiation shielding performance of newly developed B2O3–PbO–ZnO–CaO glass systems

Glasses with varying compositions were prepared using the melt-quenching process within the 40B2O3–20PbO-xZnO-(40-x)CaO system, where x = 20, 25, 30 and 35 mol%. ZnO's influence on the prepared glasses' radiation shielding properties was studied in the 0.015–15 MeV energy range. The results demonstrated that ZnO has a significant shielding effect at low energies, where there is an increased in the linear attenuation coefficient from 279.96 to 319.17 cm−1 at 0.015 MeV due to the 20-to-35 mol% increase in ZnO. The values of the mean free path (MFP) for the prepared glasses are very small when the energy is less than 0.1 MeV, in the order of 0.013–0.015 cm at 0.03 MeV, 0.051–0.055 cm at 0.05 MeV and 3.051–3.248 cm at 1 MeV, which revealed an enhanced attenuation efficiency with increasing ZnO content. According to the MFP results, the Zn35Ca5 sample (which contains 35 mol% ZnO) offers the best shielding performance. The half value layer (HVL) was also evaluated, and we found that the HVL is in order of 1.5 cm at 0.6 MeV, and in order of 3 cm at 2 MeV, while at 15 MeV, the HVL is 4.30 cm for Zn20Ca20 and 3.74 cm for Zn35Ca5.

Alpha particle energy-range studies by a layer removal method in polycarbonate detectors for determining unknown ion energies

The aim of this study is to apply a “layer removal method” for alpha energy-range determination in polycarbonate detectors (PC) compared with SRIM software. This method is a precise chemical pre-etching process by which a layer of a certain thickness is removed from an exposed or unexposed PC detector surface before applying electrochemical etching (ECE). A group of 500 μm thick PC detectors was exposed to alpha particles of known fluence (∼1.0 × 104 alphas.cm−2) and ∼0.3–∼5.0 MeV energy range, followed by a pre-etching process at 12 different time intervals in 70% ethylenediamine solution. After the ECE process, alpha track density and diameter were determined. Track density versus removed layer thickness for each alpha energy follows a Bragg type peak after which approaching zero at a known removed layer thickness corresponding to the alpha range. The results also show a linear increase of the mean track diameter as the removed layer thickness increases for each energy. On the other hand, this study confirms a shift in the energy range registration by increasing the thickness of the removed layer. Using this precise method, an unknown energy can be determined by step-by-step thickness removal process until the track density approaches zero. In conclusion, the upper energy of ions emitted in a PFD can be determined. This method is a precise and simple method for ion energy-range determination studies for passive ion spectrometry.

Study of the 11B(p,α)αα Reaction in the 0.3–2.15 MeV Energy Range of the Proton Beam

Study of the 11B(p,α)αα Reaction in the 0.3–2.15 MeV Energy Range of the Proton Beam

Comprehensive study on structural, optical, mechanical and radiation blocking nature of Eu3+-doped bismuth tellurite glasses

A novel glass system B2O3–SiO2–Bi2O3–TeO2–BaO–ZnO doped with Eu2O3 (x = 0–4 mol%) is fabricated through melt-quench technique and coded as BiTeEu-x. Density and refractive index measurements done on the glasses resulted in the increase up to 5.4377 gcm−3 and 1.99, respectively, for 4 mol% addition of Eu2O3. Vickers micro-indentation measurements done on synthesized glasses gave increasing microhardness values with Eu3+ doping due to higher bond strength of Eu–O bond compared to Te–O bond. The Phy-X/PSD simulation software utilized for obtaining radiation shielding parameters produced highest range of mass attenuation coefficient (63.878–0.036 cm2/g) and lowest range of half-value layer (0.002–3.551 cm) for the same glass proving its superiority in radiation attenuating capacity. This article addresses the theoretical analysis of photon buildup occurring inside the fabricated glasses in 0.015–15 MeV energy range with respect to different penetration depths. Neutron shielding ability of BiTeEu-4 glass was found to be impressive with fast neutron removal cross section (FNR) value of 0.10362 cm−1.

Effect of oxidation on radiation shielding capacity of ZrNbTaMoW Refractory High Entropy Alloys (RHEA) for nuclear reactor applications: Experimental and theoretical assessment

This study presents the production and comprehensive assessment of a Refractory High Entropy Alloy (RHEA) with a ZrNbTaMoW composition for possible usage nuclear reactor applications. The alloy was synthesized using the mechanical alloying (MA) method, and its radiation properties were examined. Elemental powders of Zr, Nb, Ta, Mo, and W were utilized in equimolar quantities during the 120-hour MA process, conducted under a high-purity Ar atmosphere to prevent oxidation. The obtained HEA was then subjected to a mechano-thermal process to transform it into Refractory High-Entropy Oxide (RHEO) for comparing their radiation-shielding performance under oxide conditions. The characterization of the produced alloys through X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS). The photon shielding parameters of the alloys were experimentally obtained for various energies emitted from a 133Ba radioactive source, employing a Canberra UltraLEGe semiconductor detector. Furthermore, theoretical calculations were performed to validate the experimental data and to evaluate the alloys' photon shielding capabilities comprehensively. For this purpose, Phy-X/PSD software was employed to determine mass attenuation coefficients, half-value layer, effective atomic number, and effective electron density. Fast neutron absorption capabilities were determined through the calculation of average absorption cross-sections in the 2–12 MeV energy range. The results showed that the oxidation process significantly diminished the photon absorption capacity of RHEA.

CNN-based track reconstruction study for gamma-ray pair telescope

MeV Gamma-ray Telescope (MGT) is a conceptual mission aimed at improving the detection sensitivity of gamma-ray astronomy in the MeV energy range. It consists of three sub-detectors: Gamma-ray Conversion silicon tracker, CALOrimeter and Anti-Coincident Detector. In this paper, a track reconstruction algorithm based on Convolutional Neural Networks (CNN) is developed for MGT. In order to train and test the model, Geant4 simulation is used and generates a large number of gamma-ray events at nine energy points in the energy band from 0.5 GeV to 10 GeV. Finally, the reconstruction results of angular resolution, position resolution and acceptance are shown. The testing results indicate that the angular resolution of MGT significantly improves in the 0.5∼10 GeV range compared with Fermi-LAT.

Assessment of radiation shielding capability of a high-density TeO2–Tl2O–Ag2O glass system: A simulation and theoretical studies

We investigated the shielding properties of four selected glass samples among the 66 samples. These glass samples had the following compositions and densities: S1 (55TeO2+45Ag2O, density 6.28 g/cm3), S2 (55TeO2+5Tl2O+40Ag2O, density 6.37 g/cm3), S3 (50TeO2+15Tl2O+35Ag2O, density 6.49 g/cm3), and S4 (40TeO2+55Tl2O+35Ag2O, density 7.20 g/cm3). These glasses exhibit high density. We compute the mass attenuation and linear attenuation coefficients for these samples using MCNPX simulations and Phy-X software between 0.001 MeV and 15 MeV energy range. The derived mass attenuation coefficient (MAC) enables the calculation of key radiation shielding metrics. The tenth value layer, the half value layer (HVL), the mean free path (MFP), and the effective atomic number (Zeff) were also determined. Values of LAC values for S1, S2, S3 and S4 glasses span 244.91 to 0.24932 cm⁻1, 319.52 to 0.2625 cm⁻1, 447.24 to 0.28491 cm⁻1 and 379.480 to 0.273 cm−1, respectively. Correspondingly, HVL values range from 0.0028 to 2.78005 cm, 0.0021–2.6403 cm, and 0.00154–2.4327 cm and 0.002135–2.917403 cm for S1, S2, S3 and S4 glasses, respectively. Our findings reveal that results from both MCNPX and Phy-X exhibit consistency, supported by computed relative differences. Notably, the glass sample with a relatively higher TlO2 concentration demonstrates superior shielding properties across the entire energy spectrum. Importantly, these glass samples can significantly lower the strength of the x-rays and γ-rays.

Radiophotoluminescence response of LiF:Mg,Ti pellets irradiated with clinical proton beams in the 70–200 MeV energy range

Lithium fluoride doped with Mg and Ti (LiF:Mg,Ti) has been used for several decades as thermoluminescent dosimeter material, but recently also its radiophotoluminescence has been investigated for applications in dosimetry. In this work, LiF:Mg,Ti pellets (TLD-100) were irradiated in a water phantom at CNAO (Pavia, Italy) with therapeutic proton beams at five energies from 70 to 200 MeV in the dose range from 2 to 20 Gy. After irradiation, their visible radiophotoluminescence spectra were measured in controlled conditions and the spectrally-integrated red emission response of radiation-induced color centers has been investigated. The radiophotoluminescence signal, excited by a 445 nm continuous wave laser, was integrated within a 50 nm-wide band around the emission peak of the F2 color centers, located around 670 nm in LiF. The spectrally-integrated signal of the samples irradiated at the energy of 147.7 MeV exhibited a linear dependence with dose. Moreover, this radiophotoluminescence response appears independent from Linear Energy Transfer in the range from 0.8 to 1.6 keV/μm in all the samples irradiated at the dose of 5 Gy. Such independence was found up to 10.3 keV/μm in samples irradiated within two spread out Bragg peaks made of 36 energy components in the entire investigated proton energy range. The radiophotoluminescence response of the TLD-100 pellets was compared to that of nominally-pure LiF crystals irradiated in the same conditions, which show a similar behavior. The results are encouraging for the exploitation of TLD-100 pellets as passive solid-state radiophotoluminescent dosimeters for proton therapy.

Probing deformed nuclei: Experimental insights into excited states of 152,153,154Gd isotopes through fusion-evaporation reactions

The rare-earth region has been the focus of various studies aiming at the understanding of nuclear structure and providing information on the details of the reaction mechanism. The Gd isotopes belong to this group of nuclei and despite the available spectroscopic information, several open questions about their structure still exist, such as the inter-band transitions related to shape evolution or branching-ratios in deformed states. In addition, production cross sections of different reactions to Gd isotopes are largely unknown.In this work, we report on an experimental attempt to populate the excited states in the isotopes 152,153,154Gd by employing the heavy-ion fusion reaction 18O+138Ba → 156-xGd + xn in the 58-64 MeV energy range (center-of-mass). The experiment was conducted at the 9 MV FV Pelletron Tandem at the Horia Hulubei National Institute for Physics and Nuclear Engineering, employing the ROSPHERE array. Several branching-ratios for energy levels in 152,153Gd have been measured, offering new and updated values. Furthermore, relative cross sections regarding the fusion-evaporation reactions 138Ba(18O, 4n)152Gd, 138Ba(18O, 3n)153Gd, and 138Ba(18O, 2n)154Gd have been measured and compared with theoretical calculations with PACE4.

Passive single-sphere multi-detector spectrometry system for profiling of neutron fields in the thermal to 20 MeV energy range

This study explores the development and application of a custom-designed single-sphere multi-detector spectrometer (SSMDSS) for characterizing neutron fields. Stray neutrons in reactor and accelerator facilities present complex, energy-diverse fields. Accurately assessing these fields is crucial for personnel safety. The SSMDSS system is designed to address this challenge, offering a compact and passive dosimetry solution for constrained workspaces. We studied the performance of SSMDSS in two environments: radio-nuclide based neutron sources and stray neutron fields at a research reactor hall. Our investigation demonstrates that SSMDSS provide reliable neutron energy distributions. The performance of the SSMDSS was compared with commercially available ROSPEC system. SSMDSS exhibits superior resolution due to its design, leading to a more accurate measurement of low-energy fluence when compared with ROSPEC. This distinction is reflected in various measured parameters, including average energy and fluence-to-dose conversion coefficients. Inside the reactor hall, SSMDSS measured a fluence-to-dose conversion coefficient of 121 pSv.cm2 compared to ROSPEC's 83 pSv.cm2. Additionally, SSMDSS measured a higher average energy (0.25 MeV) compared to ROSPEC (0.14 MeV). While ROSPEC remains a valuable tool for real-time data collection in dynamic fields with high gamma backgrounds, SSMDSS presents itself as a viable alternative for neutron spectrometry in neutron work fields due to its compact design and passive dosimetry capabilities. This makes it particularly suitable for deployment in constrained workspaces with potential stray neutron exposure.

Investigate various shielding parameters for (C18H20O8)x (ZrSiO4)100-x and (C18H20O8)x (BiClO)100-x in medical radiological applications

This study investigates some of shielding parameters of (C18H20O8)x (ZrSiO4)100-x and (C18H20O8)x (BiClO)100-x, x=(95,80,65,50)% wt coded as (S1,S2) for medical radiation application. We employed a theoretical model to calculate a mixture’s mass attenuation coefficients (MAC) during our investigation. The XCOM computer program was utilized for this purpose within the energy range of (0.356,0.364,0.44,0.662,0.739,0.834,0.846,1.17,1.238,1.274,1.33,1.368 and 2.754) MeV. The MAC values were used to compute several parameters, such as the linear attenuation coefficient LAC, half-value layer HVL, and effective atomic number Z eff . The study’s findings revealed a consistent decrease in the value of LAC as the energy increased for all the mixtures. The maximum value of LAC is 0.366 cm−1 in energy 0.356 MeV at x=50 for S2. The results show that adding BiClO to a matrix material can greatly improve its attenuation properties and be used to protect against medical radiation. The results show that the values of Z eff decreased with increasing energies, then stabilized and changed slightly at increasing energy. The lowest HVL values and the best for shielding were in group S2. The investigation also examined the association between the Z eff and the LAC at the value of x=50. The results show the correlation was positive and strong.