MeV Energy Range Research Articles

Single event burnout failures caused in silicon carbide power devices by alpha particles emitted from radionuclides

Single event burnouts (SEB) threaten the safe operation of high voltage SiC power devices in a wide range of applications. The triggering of this failure mechanism has been widely documented for the case of heavy ions and neutron interactions. In this study, it is demonstrated experimentally that destructive SEB events can be triggered in SiC and Si power devices by single alpha particles in the 5 MeV energy range, such as those emitted by radioactive isotopes. Such SEB events have been observed for blocking voltages lower than the breakdown voltage of the investigated devices. The experimental setup making use of an Am241 planar source to quantitatively observe the current pulses resulting from irradiation is described in detail. The mechanism of SEB initiation by single alpha particles has been investigated by the means of TCAD simulation.The experimental and simulation results show that alpha particles can trigger SEB in both SiC and Si power devices, with SiC devices exhibiting a graver susceptibility. In particular, the simulations demonstrate that the thermal runaway is a consequence of current filamentation in the main blocking junction of the devices, due to generation of a streamer along the ionization track produced by the impinging particle. Furthermore, it is shown that the increased susceptibility of SiC devices to destructive SEB is due to the stronger local field, thinner depleted region and higher junction capacitance than in Si, resulting in higher available energy for the destructive event. The present findings may have practical implications. Given the simplicity and economy of the procedure, alpha sources can be used as a complementary technique to nucleon irradiation for the characterization of the susceptibility of power devices to SEB. Finally, the possible impact on the triggering of SEBs by alpha emitters present as contamination near the active areas of the device should be reconsidered.

Monte Carlo simulations of electron interactions with the DNA molecule: A complete set of physics models for Geant4-DNA simulation toolkit

In this study we are introducing an update of the Geant4-DNA physics constructor “option 6” including electron interactions with all constituents of the DNA molecule in addition to those already publicly available for liquid water. The new implementation is based on the interaction cross sections of electrons with the four DNA nucleobases, deoxyribose and phosphoric acid for elastic scattering, electronic excitation and ionisation in the 11 eV – 1 MeV energy range. An additional sampling method to estimate the transferred secondary electron energy produced by ionisation is also introduced and can be optionally activated instead of the classical interpolation method based on the differential cross section tables, thus eliminating the need to upload large data files. The implementation in Geant4-DNA was verified by calculating range and electronic stopping power in the various materials. Good agreement is observed with the data available in the literature, and calculations with the interpolation method and the sampling method showed less than 4% difference. No differences were observed in terms of computational cost.

Validation of a Proposed Equation for Determining the Half-Thickness Value of Gamma and X-Ray Radiation

Half-value layer (HVL) is energy dependent on the photon, much as the attenuation coefficient. Increasing the penetrating energy of a photon stream causes an increase in a substance's HVL. Before calculating the HVL value, the linear attenuation coefficient (μ) must be established. A review of the literature indicated that there is presently no Monte Carlo-based sufficient tool for direct calculation of the HVL value and direct computation suitable for material design and all changes based on sophisticated simulation methods. This study aims to calculate HVL data with GAMOS simulation in the 0.1-20 MeV energy range for some anatomical structures defined in ICRU-44 (bone cortical, brain, gray/white matter, breast tissue, eye lens, and testis). The HVL values of the anatomical structures used in the GAMOS code were compared with the results in the literature. As a result, HVL values obtained from GAMOS simulation for different materials and biological structures were compatible with the literature.

Scattering of electron and positron by HCN: a theoretical investigation

A theoretical investigation of differential, integrated elastic, inelastic, transport (momentum transfer & viscosity), grand total (elastic+inelastic) and total ionisation cross-sections along with the Sherman functions for the scattering of electron and positron by hydrogen cyanide (HCN) in the energy range 1 e V − 1 MeV are presented in this report. We perform calculations using the single scattering independent atom model (IAM) and IAM with screening correction (IAMS). The scattering observables are calculated using a complex optical model potential in the framework of the Dirac partial wave analysis (DPWA). The inclusion of screening correction to the IAM appreciably improves the cross-sections, especially at low-impact energies. Our calculated results are compared with the available experimental and theoretical works found in the literature. Our present computational data agree well with prior results.

Tailoring a symmetry for material properties of tellurite glasses through tungsten(vi) oxide addition: Mechanical properties and gamma-ray transmissions properties

AbstractWe report a correlation outcome for mechanical and gamma-ray transmission properties of tellurite glasses by increasing tungsten(vi) oxide concentration in glass structure. The mechanical properties as well as Poisson’s ratio (σ) of the studied glasses are estimated by applying Makishima–Mackenzie model. Gamma-ray attenuation properties using various fundamental parameters are determined in 0.015–15 MeV energy range. Poisson’s ratio (σ) decreased from 0.43017 to 0.42711, while all elastic moduli increased linearly with the molar increment of either [WO3] or [TeO2] in the molecular structure of the glass network. Moreover, gamma-ray attenuation properties are enhanced as a function of increasing WO3substitution amount from 30 to 50% mol in the glass structure. Half-value layer values at 15 MeV are found to be between 2.648 and 2.8614 cm. I4 samples with a composition of 20TeO2–50WO3–30GdF3and density of 6.0530 g/cm3was found to have superior material properties in terms of elastic and gamma-ray attenuation properties. It can be concluded that maximized WO3contribution into the tellurite glasses may be considered as a critical tool in terms of establishing a symmetry between mechanical and gamma-ray attenuation properties for high-density tellurite glasses for their potential utilization in nuclear waste management, radiation shielding, and radioactive source transportation purposes.

Investigation of the fusion mechanism in the Li6 -induced reaction on Nb93

We attempt to put forth the competing reaction mechanisms through residual cross section measurement in $^{6}\mathrm{Li}$ fusion with $^{93}\mathrm{Nb}$. The measured residual cross sections in the 24--43 MeV energy range are analyzed with the theoretical estimations from pace4, empire3.2.2, and alice23 statistical model codes. The replication of major $xn$-channel cross sections by empire with enhanced generalized superfluid model (EGSM) level density confirms that the population of $xn$-channel residues is through the complete fusion (CF) mechanism. The preequilibrium (PEQ) emission signatures were witnessed in the case of $^{97}\mathrm{Ru}$ residue populated via the $2n$ channel. Amplification of major experimental $p$- and $\ensuremath{\alpha}$-channel cross sections relative to the optimal theory was interpreted by considering the possibility of an incomplete fusion (ICF) process in addition to CF, owing to the low breakup threshold of the $^{6}\mathrm{Li}$ projectile. Thus, the ICF strength fraction $({F}_{\mathrm{ICF}})$ was estimated. The ${F}_{\mathrm{ICF}}$ turned out to be $\ensuremath{\approx}8--20%$ with an increasing trend and is found to be thoroughly higher than the deduced ${F}_{\mathrm{ICF}}$ for $^{7}\mathrm{Li}$ reaction on $^{93}\mathrm{Nb}$ target. In the case of weakly bound $^{6,7}\mathrm{Li}$-induced reactions, the first attempt is made to understand the influence of entrance channel parameters such as bombarding energy, $\ensuremath{\alpha}$-separation energy, Coulomb factor, mass asymmetry, neutron skin thickness, angular momentum, etc., on ${F}_{\mathrm{ICF}}$. The observed trend of the isomeric cross section ratios from the relative population of isomeric and ground states of $^{96,94}\mathrm{Tc}$ radionuclides is also discussed.

Bragg Curve Detection of Low-Energy Protons by Radiophotoluminescence Imaging in Lithium Fluoride Thin Films.

Lithium fluoride (LiF) crystals and thin films are utilized as radiation detectors for energy diagnostics of proton beams. This is achieved by analyzing the Bragg curves in LiF obtained by imaging the radiophotoluminescence of color centers created by protons. In LiF crystals, the Bragg peak depth increases superlinearly with the particle energy. A previous study has shown that, when 35 MeV protons impinge at grazing incidence onto LiF films deposited on Si(100) substrates, the Bragg peak in the films is located at the depth where it would be found in Si rather than in LiF due to multiple Coulomb scattering. In this paper, Monte Carlo simulations of proton irradiations in the 1-8 MeV energy range are performed and compared to experimental Bragg curves in optically transparent LiF films on Si(100) substrates. Our study focuses on this energy range because, as energy increases, the Bragg peak gradually shifts from the depth in LiF to that in Si. The impact of grazing incidence angle, LiF packing density, and film thickness on shaping the Bragg curve in the film is examined. At energies higher than 8 MeV, all these quantities must be considered, although the effect of packing density plays a minor role.

Detection limit for secondary ions of organic molecules under MeV ion bombardment

In the present work we have investigated the chemical sensitivity of a mass spectrometry imaging method MeV – SIMS. Primary ion beam within the MeV energy range domain was employed to bombard samples of two organic compounds; amino acid arginine, and peptide hormone angiotensin II (human), with average molecular weights of 174.2 u and 1046.2 u respectively. Secondary ion yield was measured as a function of number of molecules per area unit, and the detection limit was determined. For both molecular compounds and two different energies of primary 35Cl ion beam, the secondary ion yield exhibited a significant decrease below the area density of 1015 molecules/cm2, while the density of 1013 molecules/cm2 resulted in molecular peak / background ratio being lesser than 3, which is below the commonly used sensitivity threshold in other techniques. Other experiment related drawbacks to sensitivity were also discussed.

Virtual photon approach of cathodoluminescence and ion-beam induced luminescence of solids

A novel analysis of cathodoluminescence (CL) and ion-beam induced luminescence (IBIL) is presented on the basis of virtual photon spectra (VPS) produced by charged particles (electrons or ions) passing by luminescent species such as defects or impurities, in wide band-gap ionic-covalent solids. A discussion is provided for irradiations in a wide range of charged particle kinetic energy by using the Weizsäcker-Williams theory. The computed VPS are found to decay rapidly as a function of virtual photon (VP) energy regardless of particle energy, for close or distant collisions. The electron-energy dependence of experimental CL spectra of sapphire (α-Al2O3) is discussed in relation to the computed VPS for the primary and secondary electrons. The experimental IBIL spectra of α-Al2O3 are also analyzed in this framework for protons and helium ions in the MeV energy range. The variations of stopping power are consistent with the variation of the number of emitted VPs. The decay of IBIL yield versus ion stopping power is discussed on the basis of the variation of the computed VPS, and ionization and excitation induced by primary ions and secondary electrons. This decay is accounted for by a decrease of the yield of low-energy secondary electrons with the subsequent VP emission.

Bright X-ray pulsars as sources of MeV neutrinos in the sky

ABSTRACT High-mass accretion rate on to strongly magnetized neutron stars results in the appearance of accretion columns supported by the radiation pressure and confined by the strong magnetic field of a star. At mass accretion rates above $\sim 10^{19}\, {\rm g\, s^{-1}}$ , accretion columns are expected to be advective. Under such conditions, a noticeable part of the total energy release can be carried away by neutrinos of a MeV energy range. Relying on a simple model of the neutrino luminosity of accreting strongly magnetized neutron stars, we estimate the neutrino energy fluxes expected from six ULX pulsars known up to date and three brightest Be X-ray transits hosting magnetized neutron stars. Despite the large neutrino luminosity expected in ULX pulsars, the neutrino energy flux from the Be X-ray transients of our Galaxy, Small Magellanic Cloud (SMC), and Large Magellanic Cloud is dominant. However, the neutrino flux from the brightest X-ray transients is estimated to be below the isotropic background by two orders of magnitude at least, which makes impossible direct registration of neutrino emission from accreting strongly magnetized neutron stars nowadays.

The dual ion beam microprobe

A new experimental setup for dual ion microbeam irradiation and analysis of materials has been designed and commissioned at the Ruđer Bošković Institute (RBI). Ion beams in the MeV energy range are provided by two tandem accelerators, a 1.0 MV Tandetron and a 6.0 MV EN tandem Van de Graaff. The dual microprobe end station is primarily dedicated for the performance of experiments where one ion microbeam is used for the irradiation, while the other ion microbeam is used for the analysis or ‘probing’ the in-situ changes induced during the target irradiation. Likewise, both microbeams can be also used independently, for experiments involving either ion beam characterization or ion beam irradiation techniques. The ion beam from the small tandem accelerator is focused with a magnetic quadrupole triplet, which is more suitable for the high spatial resolution work with light ions. The ion beam from the larger accelerator is focused by an electrostatic quadruplet that enables easier focusing of heavy ions. Details of the experimental setup, its capabilities in terms of ion beam irradiation and analysis techniques, as well as the first applications, are presented.

The light charged particle detector array at the CSNS Back-n white neutron source

The Back-n white neutron source at the China Spallation Neutron Source (CSNS) provides neutrons in the continuous energy region from 0.5 eV to 200 MeV. A spectrometer named Light charged Particle Detector Array (LPDA) is designed for the study of (n, lcp) reactions at Back-n. The main detector of the LPDA spectrometer, a 16-unit ΔE-ΔE-E telescope array, is composed of two arrays of 8-unit ΔE-ΔE-E telescope. Each telescope unit consists of a Low-Pressure Multi-Wire Proportional Chamber (LPMWPC), a Si-PIN detector, and a CsI(Tl) scintillator detector. In 2021, a neutron-proton (n-p) scattering reaction cross-section measurement experiment was accomplished as the first experiment of the telescope array. Protons can be clearly identified in the ΔE-E spectrum (LPMWPC + Si-PIN) and the ΔE-E spectrum (Si-PIN + CsI(Tl)). Cross sections of the n-p scattering reaction in the neutron energy range of several MeV are extracted. The ΔE-E method also provides new measurement opportunities for many-body neutron induced light charged-particle emission reactions.

Mechanical properties, elastic moduli, and gamma ray attenuation competencies of some TeO2–WO3–GdF3 glasses: Tailoring WO3–GdF3 substitution toward optimum behavioral state range

Abstract We report the mechanical properties, elastic moduli, and gamma ray attenuation properties of some TeO2–WO3–GdF3 glasses. Using the chemical composition of the selected glasses, the dissociation energy per unit volume (G t ) and the packing density (V t ) were calculated. Using the G t and V t values, Young’s, Shear, Bulk, Longitudinal Modulus, and Poisson’s ratio of the glasses are calculated. Next several fundamental gamma ray attenuation properties such as linear and mass attenuation coefficients, half value layer, mean free path, effective atomic number, effective electron density, effective conductivity, exposure, and energy absorption buildup factors are calculated in 0.015–15 MeV energy range. As a consequence of WO3–GdF3 substitution, the glass densities are observed in different values. The overall gamma ray attenuation properties are found to be enhanced through WO3 addition. Moreover, the increasing WO3 incorporation into glass configuration decreases the overall elastic moduli of glasses. It can be concluded that increasing WO3 may be a useful tool for enhancing the gamma ray attenuation qualities and decreasing the elastic moduli of TeO2–WO3–GdF3 in situations where a material with versatile mechanical properties is required.

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.

Target Density Effects on Charge Transfer of Laser-Accelerated Carbon Ions in Dense Plasma.

We report on charge state measurements of laser-accelerated carbon ions in the energy range of several MeV penetrating a dense partially ionized plasma. The plasma was generated by irradiation of a foam target with laser-induced hohlraum radiation in the soft x-ray regime. We use the tricellulose acetate (C_{9}H_{16}O_{8}) foam of 2 mg/cm^{3} density and 1mm interaction length as target material. This kind of plasma is advantageous for high-precision measurements, due to good uniformity and long lifetime compared to the ion pulse length and the interaction duration. We diagnose the plasma parameters to be T_{e}=17 eV and n_{e}=4×10^{20} cm^{-3}. We observe the average charge states passing through the plasma to be higher than those predicted by the commonly used semiempirical formula. Through solving the rate equations, we attribute the enhancement to the target density effects, which will increase the ionization rates on one hand and reduce the electron capture rates on the other hand. The underlying physics is actually the balancing of the lifetime of excited states versus the collisional frequency. In previous measurement with partially ionized plasma from gas discharge and z pinch to laser direct irradiation, no target density effects were ever demonstrated. For the first time, we are able to experimentally prove that target density effects start to play a significant role in plasma near the critical density of Nd-glass laser radiation. The finding is important for heavy ion beam driven high-energy-density physics and fast ignitions. The method provides a new approach to precisely address the beam-plasma interaction issues with high-intensity short-pulse lasers in dense plasma regimes.

A Promising Glass Type in Electronic and Laser Applications: Elastic Moduli, Mechanical, and Photon Transmission Properties of WO3 Reinforced Ternary-Tellurite Glasses

We report the symmetry of mechanical and gamma-ray attenuation properties for some tellurite glasses through elastic moduli, mechanical, and transmission properties as a function of varied WO3 amount in glass configuration. Four glass samples, along with different molar compositions as well as WO3/GdF3 substitution ratios, are investigated. Transmission properties using several essential parameters, such as attenuation coefficients, half-value layers, effective atomic numbers, effective conductivity, and buildup factors, are calculated in the 0.015–15 MeV energy range. Moreover, elastic moduli and Poisson’s ratios (σ) of the studied glass are calculated using the Makishima–Mackenzie model. The M4 sample with the highest WO3 addition is found with superior photon attenuation properties among the glasses investigated. Poisson’s ratio (σ) is increased, while all elastic moduli are decreased. Young’s modulus is reported as 62.23 GPa and 36.45.37 GPa at the highest and lowest WO3 mol%, respectively. It can be concluded that WO3 is a functional and monotonic tool in ternary-tellurite glasses for multiple modifications and enhancement purposes on gamma-ray attenuation, elastic moduli, and mechanical properties. It can also be concluded that increasing the WO3 amount in tellurite glasses may be considered a tool in terms of providing symmetry for mechanical and gamma-ray attenuation properties.

Measurement of thick target neutron yield from 80.5 MeV/u 12C incidence on Be, C, W, and Pb targets

Thick target neutron yield produced from 80.5 MeV/u 12C ions stopping in the thick Be, C, W, and Pb targets were measured at 0°, 37°, 60° using liquid scintillation detector and the time of flight method. The experimental data were compared with those calculations using the Liege IntraNuclear-Cascade (INCL) implemented in Geant4 and the JAERI Quantum Molecular Dynamics 2.0 (JQMD-2.0) model followed by the Generalized Evaporation Model (GEM) implemented in PHITS, and default model implemented in FLUKA. The results of the three simulation codes with different physics models are similar for beryllium and carbon targets and in good agreement with the experimental data. For tungsten and lead targets, the calculation results from PHITS and FLUKA successfully reproduced the neutron spectra. While the results from GEANT4 overestimate the experimental data above 50 MeV at 0° and significantly underestimated experimental data in the 15–60 MeV energy range at 0°, 37° and 60°. In general, the simulation results of PHITS with the JQMD-2.0 physical model are in good agreement with the experimental data for all targets.

Measurement of 9Be(3He,p i )11B (i = 0, 1, ..., 9) nuclear reaction cross sections in the 1.0 MeV to 2.5 MeV energy range

In fusion materials research using ion beam analysis techniques, the reactions 9Be(3He,p i )11B (i = 0, 1, 2…) are relevant to probe Be-related plasma-wall interactions. The cross sections for this reaction have been examined previously; nevertheless, there is a ∼40% difference in the studied energy interval between the two most relevant earlier studies. Therefore, a new data set for the differential cross sections 9Be(3He,p i )11B for the proton groups i = 0, 1, …, 9 is given. The measurements were performed using a thin beryllium film in the laboratory energy range from 1.0 MeV to 2.5 MeV in steps of 50 keV for lab angles from 115° to 165° to the incoming beam direction in steps of 10°. Additional measurements for intermediate angles were performed over the same energy range in steps of 250 keV. The results are in good agreement with one of the previous studies and a benchmarking measurement was performed against the yield of a beryllium thick target at 2.5 MeV for 135°.

Secondary particle predictions in quasifree proton scattering reactions in the 100–250 MeV energy range

Results for observables related to the secondary particle production process in proton-nucleus spallation reactions at low beam incident energy (100--250 MeV) are shown. The energy and angular distributions of the residual nucleus are determined in the context of our multicollisional Monte Carlo intranuclear cascade model. The mechanism of proton-nucleus reactions is conventionally described as a sequence of two stages: the rapid intranuclear cascade phase and the slow particle evaporation step. In this work we focus on the rapid phase considering the nucleon effective mass as an effect of the many-body nuclear interactions and the intranuclear mean field. This procedure represents a more realistic scenario to obtain the particles' multiplicity generated in spallation reactions with light-mass target nuclei in a low-energy range. We focused our attention on target nuclei of macro elements, such as carbon, oxygen, phosphorus, sulfur, sodium, potassium, chlorine, and calcium, and trace elements such as iron, copper, zinc, bromine and selenium, which are the most frequent compounds of the organic material. The choice of these target nuclei is due to our expectancy that our results can work as a preliminary insight for further theoretical approaches, specially taking into account nuclear effects due to the interaction of the particles of the beam with the organic tissue.

Study of [formula omitted] reactions in the [formula omitted] targets

The development of novel medical radioisotopes for diagnostic and therapeutic purposes is critical for the advancement of personalized nuclear medicine. Radio metals contain promising theranostic pairs and can be used to label proteins and peptides. Scandium radionuclides have recently gained a lot of attention for their radiation characteristics (such as half-life, β particle and gamma emission energies) in order to improve the efficiency of medical care or therapeutic benefit for specific groups of patients.An accurate understanding of the production cross-sections is required to maximize the production yield and radionuclidic purity, as well as to improve the model predictions. In this paper, we report the measurement of the cross-section of (p,x) reactions for the production of 47Ca, 42K, 43K, and 44mSc, 46Sc, 47Sc, 48Sc using natCaO targets using proton beam of energy up to 60 MeV. The reported data for 47Sc is the first experimental data with a natCaO target in the 16–60 MeV energy range. All radioisotope cross sections produced by natCaO(p, x) reactions are compared to literature data and TALYS predictions.