Recoil Nuclei Research Articles

Characterization of new silicon carbide neutron detectors with thermal and fast neutrons

The aim of this work is to present a characterization of a new silicon carbide (SiC) neutron detector fabricated at the Institute of Microelectronics of Barcelona (IMB-CNM-CSIC). The device is based on a 50μm thick p-n diode built in a 4H-SiC wafer. Performance studies were carried out under different neutron energy spectra, including thermal and quasi-monoenergetic fast neutrons at the CNA HiSPANoS facility. We implemented a method for the fabrication of enriched LiF conversion layers to use for the detection of thermal neutrons. The detector was proven to be capable of being used for thermal neutron detection with conversion layers of 10B and LiF. A detection efficiency of 6 ± 1% was achieved with a 25μm thick LiF conversion layer. It was also confirmed that the device can be employed for the detection of recoil nuclei and protons produced by fast neutrons. The spectra obtained experimentally were compared with PHITS simulations. This work represents the first step towards the design and fabrication of new SiC neutron detectors in the IMB-CNM-CSIC clean room with potential applications in various scientific and technological fields.

Response of a high-pressure 4He scintillation detector to nuclear recoils up to 9 MeV

Helium-4-based scintillation detector technology is emerging as a strong alternative to pulse-shape discrimination-capable organic scintillators for fast neutron detection and spectroscopy, particularly in extreme gamma-ray environments. The 4He detector is intrinsically insensitive to gamma radiation, as it has a relatively low cross-section for gamma-ray interactions, and the stopping power of electrons in the 4He medium is low compared to that of 4He recoil nuclei. Consequently, gamma rays can be discriminated by simple energy deposition thresholding instead of the more complex pulse shape analysis. The energy resolution of 4He scintillation detectors has not yet been well-characterized over a broad range of energy depositions, which limits the ability to deconvolve the source spectra. In this work, an experiment was performed to characterize the response of an Arktis S670 4He detector to nuclear recoils up to 9 MeV. The 4He detector was positioned in the center of a semicircular array of organic scintillation detectors operated in coincidence. Deuterium–deuterium and deuterium–tritium neutron generators provided monoenergetic neutrons, yielding geometrically constrained nuclear recoils ranging from 0.0925 to 8.87 MeV. The detector response provides evidence for scintillation linearity beyond the previously reported energy range. The measured response was used to develop an energy resolution function applicable to this energy range for use in high-fidelity detector simulations needed by future applications.

Synergistic effect of electrical bias and proton irradiation on the electrical performance of β-Ga2O3 p–n diode

The synergistic impact of reverse bias stress and 3 MeV proton irradiation on the β-Ga2O3 p–n diode has been studied from the perspective of the defect in this work. The forward current density (JF) is significantly decreased with the increase in proton irradiation fluence. According to the deep-level transient spectroscopy results, the increase in the acceptor-like trap with an energy level of EC-0.75 eV within the β-Ga2O3 drift layer, which is most likely to be Ga vacancy-related defects, can be the key origin of the device degradation. The increase in these acceptor-like traps results in the carrier concentration reduction, which in turn leads to a decrease in JF. Furthermore, compared with the case of proton irradiation with no bias, the introduction of −100 V electrical stress induced a nearly double decrease in JF. Based on the capacitance–voltage (C–V) measurement, with the support of the electric field, the carrier removal rate increased from 335 to 600 cm−1. Similar to the above-mentioned phenomenon, the trap concentration also increased significantly. We propose a hypothesis elucidating the synergistic effect of electrical stress and proton irradiation through the behavior of recoil nuclei under the electric field.

Impact of gold ion irradiation on the initial alteration rate of the International Simple Glass

This study addresses the impact of 7 MeV Au irradiation on the initial alteration rate of International Simple Glass (ISG), considered as a reference for nuclear glasses. This irradiation scenario simulates the effect of nuclear collisions of the recoil nuclei of α decays. In order to study the very first moments of glass alteration, non-irradiated and Au-ion irradiated ISG glass monoliths were altered in pure water at 90 °C, pH 9 and with a ratio of glass surface area to solution volume of 0.01 cm−1. Glass alteration was monitored by measuring the releases of the glass elements in solution by UV–visible spectrophotometry and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Under these alteration conditions, the releases of the elements in solution are congruent. The initial alteration rate was found to be (2.0 ± 0.8) times higher for the irradiated glass monoliths than for non-irradiated samples.

57Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes

This paper presents the results of 57Fe Mössbauer spectroscopy and X-ray diffraction analysis of highly metamict perrierite (REE,Ca,Th)4(Fe2+,Mg)2(Ti,Fe3+)3Si4O22 after annealing in argon from 673 to 1273 K for one hour. Radioactive elements in metamict minerals damage crystal structure on geologic time scales primarily due to recoil nuclei from α-decay of 238U, 232Th, 235U, and their daughter products. Metamict minerals are widely used in geochronology and can serve as natural analogs for the study of radiation effects in high-level nuclear waste. Analyses were performed on fragments of a perrierite sample collected from granitoids near Amherst, Virginia (USA). Electron microprobe and gamma-ray spectrometry recorded Fe concentrations of 4.7 wt.% and Th and U concentrations of 0.64 and 0.06 wt.%, respectively. The calculated total absorbed α-dose was 7.8 × 1015 α-decay mg−1. The Mössbauer spectrum of the untreated sample can be fitted to two Fe2+ and two Fe3+ doublets in octahedral coordination with a relative ΣFe2+/ΣFe of 0.63. For samples annealed at 1173 K and 1273 K, spectra show a decrease in the total contribution of Fe2+ to 0.58 due to dehydroxylation associated with the simultaneous oxidation of post-metamict Fe2+ to Fe3+. In the examined perrierite, Fe2+ occurs in structural positions B and C(1). The broad, predominant Fe3+ doublet observed in the spectrum of the unannealed sample splits into two components at 973 K interpreted to represented positions C(1) and C(2) in the perrierite structure. The Mössbauer spectra show a prominent decrease in the width of the high-energy absorption peak representing Fe2+ components with increasing temperature. The variation in the width of this peak versus the annealing temperature seems to be an indicator of thermally induced recrystallization. Based on the exponential dependence of the derivative function of the parameter with the inverse temperature and using an Arrhenius plot, an activation energy (EA) of 0.73 eV was determined for thermally-induced recrystallization. Corresponding XRD data show progressive recrystallization with increasing annealing temperature. The XRD pattern of the fragment annealed at 1273 K indicates that highly metamict perrierite recrystallized to the pre-metamict state that can be indexed to the C2/m space group.

Characterization of homogeneous nucleation of superheated liquid droplets by nonlinear analysis

The homogeneous bubble nucleation in superheated liquid droplets can be initiated by energetic particles or radiation. The nonlinearity in the heat transfer introduces chaos in the temperature time series of a boiling system. In the present study, the acoustical pulses from the homogeneous nucleation of superheated liquid droplets by neutrons and gamma-rays have been collected. Nonlinear time series analysis methods like 3D attractor reconstruction and Fast Fourier transformation (FFT) have been performed on the collected pulses. The analysis predicts the possibility of the existence of chaos, and the positive value of the largest Lyapunov exponent confirms it. The nonlinearity in the energy deposition by both the recoil nuclei and electrons from the neutrons and gamma-rays respectively, introduce chaos. A qualitative difference has been observed in the 3D attractor and Rescaled Range (R/S) plots between the neutron and gamma-ray-induced pulses, and the present differences are useful for the identification of these pulses.

In situ TEM study of heavy-ion irradiation-induced amorphisation and electron beam-induced recrystallisation in powellite (CaMoO4)

Molybdenum-rich radioactive waste streams in the UK will be vitrified into glass composite high-level waste (HLW) products containing powellite (CaMoO4) crystals. These materials will be exposed to self-irradiation in a geological disposal facility for thousands of years. Our heavy-ion and electron irradiation results, together with a comprehensive review of previous studies, reveal new details on the radiation tolerance of powellite. In this study, powellite crystals were exposed to 500 keV Ar2+ and 600 keV Xe2+ ion irradiations between -160 and -80 °C and were analysed in situ via transmission electron microscopy (TEM). At low temperatures (between -160 and -105 °C), the critical amorphisation dose (Dc) is higher for the Xe irradiation, most likely due to the significant defect recovery in the cascade core. Above -105 °C, the Dc is higher for the Ar irradiation. The dynamic annealing of radiation-induced defects becomes more efficient as the temperature increases; our results suggest that point defects formed during Ar irradiation are more susceptible to dynamic annealing compared with defects in the cascades generated during Xe irradiation. We also present the first evidence of 300 keV electron beam-induced recrystallisation in amorphous powellite by studying its response from room temperature to cryogenic temperatures inside the TEM using a wide range of electron fluxes (0.6–5.2 × 1016 e/cm2/s). In contrast to previous research, our new data suggest that powellite is susceptible to amorphisation by alpha recoil nuclei, and that beta irradiation may cause defect recombination.

Three Particle Muon-Electron Bound Systems in Quantum Electrodynamics

The muonic 2P-2S Lamb shift in muon-electron atoms and ions of helium, lithium, beryllium, and boron with the electron in the ground state was calculated by the perturbation theory using the fine structure constant and the electron-muon mass ratio. The corrections of first- and second-orders of perturbation theory on the Coulomb interaction and nucleus recoil were taken into account. The obtained analytical results were validated numerically using calculations within the variational method.

PHOTONUCLEAR PRODUCTION OF 99Mo/ 99mТс-GENERATOR WITH USING EFFECT SZILARD-CHALMERS AND ELECTROLYSIS METHOD

The possibility of photonuclear production of 99Mo medical radioisotope using recoil nuclei of molybdenite nanoparticles from reaction 100Mo(γ,n)99Mo was investigated. The enrichment of radioactive isotopes is carried out by the effect of Szilard-Chalmers. Molybdenite nanoparticles were irradiated by bremsstrahlung with Emax = 39 MeV. The recoil nuclei of 99Mo are separated by electrolysis. The yield of 99Mo from the extractable phase amounted to ~3%. This technology will allow producing 0.8 GBq/g of 99mTc with high specific activity per day. Key words: linear electron accelerator, photonuclear production, electrolysis, specific activity, recoil nuclei, molybdenite nanoparticles.

Impact of complex irradiation scenarios on the structure and the properties of the International Simple Glass

This study addresses the consequences of three irradiation scenarios on the structure and macroscopic properties of the ISG glass. The coupling effect between 2.5 MeV electron irradiation (simulating the effects of beta particles and gamma rays) and 7 MeV Au irradiation (simulating the nuclear collisions of the recoil nuclei of alpha decays) was studied by comparing two monobeam irradiations with a sequential double beam irradiation. Various experimental techniques were used to characterize the glass structure and properties, combining Raman, NMR, IR-ATR spectroscopies, hydrostatic weighing, He pycnometry, X-Ray Reflectivity, AFM, surface tension and Vickers microhardness measurements.Electron irradiation up to 3.25 GGy induces only small changes of ISG glass structure and macroscopic properties than Au irradiation. Moreover, the magnitude of the changes induced by the sequential irradiation scenario, i.e. electron followed by Au ions, are the same as the one induced by the monobeam irradiation by Au ions, except for the surface tension. Because the bulk damage state are similar, this work demonstrates that there is no coupling between the damage generated by the electron irradiation and the subsequent nuclear collision generated by Au ions. Finally, the hardness and density changes of ISG glass are very similar to those of SON68 glass when submitted to similar irradiation conditions by electron or nuclear collisions. Therefore ISG glass is found to be a good glass surrogate with respect to radiation ageing of the SON68 glass.

Study of a Coherent Elastic Neutrino-Nucleus Scattering experiment at a reactor with a PbWO4-based bolometer

The first observation of the Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) by the COHERNET experiment using accelerator neutrinos rendered opportunities for abundant scientific and technological applications. To study the CEνNS process precisely, a project using cryogenic bolometer technology with lead tungstate (PbWO4) as a detector candidate and a nuclear reactor as a neutrino source is proposed. By taking a typical reactor, the China Taishan Nuclear Power Plant, as a reference, a flux of 6.7×1016 m−2 s−1 with energy below 10 MeV can be realized at an experimental site located approximately ∼30 meters away from one of the 4.6 GWth thermal power Taishan reactor cores. The specific heat of PbWO4, which is an important detector research and design parameter, was measured for the first time at O(500) mK, and the results were found to be consistent with the prediction of Debye model. The phonon-only response of a PbWO4 crystal to the energy deposits at very low temperatures may offer high sensitivity to the small nucleus recoil CEνNS signal. A configuration using a one-gram PbWO4 cube as a detector unit working at a temperature of O(10) mK, together with novel phonon sensor technology sensitive to nucleus recoil energy as low as O(10) eV, is hypothesized as the ideal experiment benchmark. Consequently, a signal rate of around 200 reactor neutrino coherent scattering events can be expected per day with a one-kilogram PbWO4 detector volume, against ∼20 background counts in the optimized signal region.

Direct detection of spin-dependent sub-GeV dark matter via Migdal effect

Motivated by the current strong constraints on the spin-independent dark matter (DM)-nucleus scattering, we investigate the spin-dependent (SD) interactions of the light Majorana DM with the nucleus mediated by an axial-vector boson. Due to the small nucleus recoil energy, the ionization signals have now been used to probe the light dark matter particles in direct detection experiments. With the existing ionization data, we derive the exclusion limits on the SD DM-nucleus scattering through Migdal effect in the MeV-GeV DM mass range. It is found that the lower limit of the DM mass can reach about several MeVs. Due to the momentum transfer correction induced by the light mediator, the bounds on the SD DM-nucleus scattering cross sections can be weakened in comparison with the heavy mediator.

JS5-2 Current status of boron neutron capture therapy

Boron neutron capture therapy (BNCT) selectively kills tumor cells using the energy of alpha rays (He nuclei) and Li recoil nuclei emitted by the transmutation reaction between boron 10B and thermal neutrons. Currently, 10B-boronophenylalanine, generally named borofalan(10B), in which a boron group is attached to phenylalanine, is used as a boron agent, and is taken up into tumor cells based on increased amino acid metabolism. Depending on the tumor selectivity of this boron agent, it will produce a large dose difference from the adjacent normal cells.

Calculation of recoil nucleus spectrum in the presence of multi-particle emission in nuclear reaction with Monte Carlo method as an extension of CCONE code

ABSTRACT Application of Monte Carlo method was proposed by the author for the calculations of recoil nucleus spectra on high-energy nuclear reactions, in which velocity distributions were integrated over 3-dimensional space with taking into account multi-particle emissions. It was implemented in a nuclear reaction model code CCONE. The results of double differential cross sections of recoil nuclei from a proton induced reaction on 12C were compared with the experimental data and the results of a Monte Carlo simulation code PHITS. It was found that the present results showed reasonably good agreements with the experimental data for almost all measured recoil nuclei. The results were also compared with the data of evaluated nuclear data libraries of ENDF/B-VIII.0 and TENDL-2017. While the average energies of the recoil nuclei were similar, significant differences were observed in the energy distributions.

Searching for low-mass dark matter via the Migdal effect in COSINE-100

We report on the search for weakly interacting massive particle (WIMP) dark matter candidates in the galactic halo that interact with sodium and iodine nuclei in the COSINE-100 experiment and produce energetic electrons that accompany recoil nuclei via the the Migdal effect. The WIMP mass sensitivity of previous COSINE-100 searches that relied on the detection of ionization signals produced by target nuclei recoiling from elastic WIMP-nucleus scattering was restricted to WIMP masses above $\sim$5 GeV/$c^2$ by the detectors' 1 keVee energy-electron-equivalent threshold. The search reported here looks for recoil signals enhanced by the Migdal electrons that are ejected during the scattering process. This is particularly effective for the detection of low-mass WIMP scattering from the crystals' sodium nuclei in which a relatively larger fraction of the WIMP's energy is transferred to the nucleus recoil energy and the excitation of its orbital electrons. In this analysis, the low-mass WIMP search window of the COSINE-100 experiment is extended to WIMP mass down to 200 MeV/$c^2$. The low-mass WIMP sensitivity will be further improved by lowering the analysis threshold based on a multivariable analysis technique. We consider the influence of these improvements and recent developments in detector performance to re-evaluate sensitivities for the future COSINE-200 experiment. With a 0.2 keVee analysis threshold and high light-yield NaI(Tl) detectors (22 photoelectrons/keVee), the COSINE-200 experiment can explore low-mass WIMPs down to 20 MeV/$c^2$ and probe previously unexplored regions of parameter space.

Muonium Lamb shift: theory update and experimental prospects

We review the theory of the Lamb shift for muonium, provide an updated numerical value and present the prospects of the Mu-MASS collaboration at PSI to improve upon their recent measurement. Due to its smaller nuclear mass, the contributions of the higher-order recoil corrections (160 kHz level) and nucleus self-energy (40 kHz level) are enhanced for muonium compared to hydrogen where those are below the level of the latest measurement performed by Hessels et al. and thus could not be tested yet. The ongoing upgrades to the Mu-MASS setup will open up the possibility to probe these contributions and improve the sensitivity of this measurement to searches for new physics in the muonic sector.

Degradation of silicon detectors under long-term irradiation by 252Cf fission products

The response function of the recoil nuclei in detectors designed for detection of neutrinos or dark matter particles can be determined only through usage of a neutron source with a known energy spectrum. A possible solution for a compact neutron calibration source is a combination of a 252Cf neutron source and a semiconductor detector that detects fission fragments, and thus records the neutron emission moment. This work is devoted to the degradation study of the operating parameters for silicon semiconductor detectors irradiated by fission fragments of the nuclide of 252 Cf. Two types of Si detectors were under investigations - silicon-lithium Si(Li) p-i-n detectors and silicon surface barrier detectors. As a result of the measurements, the maximum permissible radiation doses for the correct operation of both types of detectors and the relation of the received radiation dose to the spectroscopic characteristics of the detectors were determined.

Alpha dose rate and decay dose impacts on the long-term alteration of HLW nuclear glasses

In the prospect of deep geological disposal, the long-term behavior of high-level nuclear glasses has to be investigated regarding alpha radiation induced by long-life minor actinides. The present study focuses on the effects of alpha radiation on the long-term chemical reactivity of R7T7-type glasses, by separately considering the alpha dose rate and the alpha decay dose. Old SON68 glasses doped with 238/239PuO2 or 244CmO2 were studied to simulate high alpha dose rates corresponding to an early water ingress and a high level of alpha decay doses corresponding to long-term disposal conditions. A part of the 238/239Pu-doped glass block was annealed to fully recover the irradiation-induced damage accumulated since the glass was fabricated and to dissociate the effect of the alpha dose rate from that of the alpha decay dose. The glasses were then leached under static conditions at 90 °C for several years. The results showed that the residual alteration rate is not affected by the alpha dose rate over a wide range of dose rate values expected under disposal conditions: this glass remained relatively insensitive to the alpha radiolysis phenomena at the glass–water interface. However, over the duration of the experiments, the residual alteration rate of the damaged 238/239Pu-doped glass was enhanced compared to that of the annealed glass. This result is in agreement with those obtained on the 244Cm-doped glass and with reported values in the literature on simplified externally irradiated glasses, indicating that the ballistic effects of the recoil nuclei are responsible for this increase in the residual alteration rate.

Directional Observation of Cold Dark Matter Particles (WIMP) in Light Target Experiments

For the last 10 years, the search for dark matter (DM) was carried out taking into account the fact that the DM particles are WIMPs (Weakly Interacted Massive Particles) which were introduced in supersymmetric extensions of the Standard Model. Many experiments such as XENON1T, DarkSide, CRESST, etc. set the constraints on the WIMP-nucleon elastic interaction cross sections for different assumed WIMP masses. Methods for detecting WIMPs could play a special role, allowing one to determine the directions of the tracks of recoil nuclei and, therefore, to determine the preferred direction of the WIMP flux. In this work, we analyze the capabilities of such direct detection experiments through analyzing the lengths and directions of the tracks of recoil nuclei. Taking into account the existing experimental constraints, we conclude that the optimal target would be a lower density target containing nuclei of the CNO group, for example, liquid propane.

The adequacy of energy deposition over thermodynamic behaviour in explaining the acoustic energy in bubble nucleation of superheated droplets

Sufficient amount of energy deposition through the energetic particles initiate bubble nucleation in the superheated liquid by producing the critical sized vapor bubble and subsequent growth of the bubble occurs by emitting the acoustic energy. The sensitive region of bubble nucleation changes by controlling the reduced superheat of the superheated liquid. The electrons sensitivity arises at higher reduced superheat as compared to the recoil nuclei. In the present work, we have observed the discrimination between the acoustic energy released due to both the recoil nuclei and electrons induced nucleation in superheated liquids like R-134a (containing the low Z nuclei) and in R-12 (of high Z nuclei). The experimental results show opposite trend in the two liquids. The experimental results are explained by the thermodynamic calculation and by the calculation of energy deposition of the recoil nuclei and electrons in the liquid.