Inelastic Reactions Research Articles

Anew GPU-based Monte Carlo code for helium ion therapy.

This work presents an effort to extend the capabilities of the previously introduced GPU-based Monte Carlo code ARCHER for helium ion therapy. ARCHER performs helium ion transport simulations in voxelized geometry, covering kinetic energy levels up to 220 MeV/u. The physical processes are modeled using aclassII condensed-history algorithm, considering ionization, energy straggling, multiple scattering, and elastic and inelastic nuclear interactions. Anew nuclear-event-repeat algorithm is proposed to generate inelastic nuclear reaction products. Secondary protons, deuterons, tritons, and 3He particles are tracked, while other particles either deposit their energy locally or are ignored. The code is developed under the compute unified device architecture (CUDA) platform to improve computational efficiency. Validations are conducted by benchmarking our code against TOPAS in different phantoms. Dose distribution comparisons demonstrate strong agreement between our code and TOPAS. The mean point-by-point local relative errors in the region where the dose exceeds 10% of the maximum dose range from 0.25% to 1.31% for all phantoms. In the strict 1%/1 mm criterion, gamma passing rates for ahead-neck case, chest case, and prostate case are 99.8%, 96.9%, and 99.6%, respectively. Except for the lung phantom, ARCHER takes less than 10 s to simulate 10million primary helium ions using asingle NVIDIA GeForce RTX 3080 card (NVIDIA Corporation, Santa Clara, USA), while TOPAS requires several minutes on acomputational platform with two Intel Xeon Gold 6348 CPUs (Intel Corporation, Santa Clara, USA) with 56 cores. This work presents the development and benchmarking of the first GPU-based dose engine for helium ion therapy. The code has been proven to achieve high levels of accuracy and efficiency.

A damage rock model considering shear failure by modified logistic growth theory

Localized rock failures, like cracks or shear bands, demand specific attention in modeling for solids and structures. This is due to the uncertainty of conventional continuum-based mechanical models when localized inelastic deformation has emerged. In such scenarios, as macroscopic inelastic reactions are primarily influenced by deformation and microstructural alterations within the localized area, internal variables that signify these microstructural changes should be established within this zone. Thus, localized deformation characteristics of rocks are studied here by the preset angle shear experiment. A method based on shear displacement and shear stress differences is proposed to identify the compaction, yielding, and residual points for enhancing the model's effectiveness and minimizing subjective influences. Next, a mechanical model for the localized shear band is depicted as an elasto-plastic model outlining the stress-displacement relation across both sides of the shear band. Incorporating damage theory and an elasto-plastic model, a proposed damage model is introduced to replicate shear stress-displacement responses and localized damage evolution in intact rocks experiencing shear failure. Subsequently, a novel nonlinear mathematical model based on modified logistic growth theory is proposed for depicting the shear band's damage evolution pattern. Thereafter, an innovative damage model is proposed to effectively encompass diverse rock material behaviors, including elasticity, plasticity, and softening behaviors. Ultimately, the effects of the preset angles, temperature, normal stresses and the residual shear strength are carefully discussed. This discovery enhances rock research in the proposed damage model, particularly regarding shear failure mode.

Jet transport coefficients by elastic and radiative scatterings in the strongly interacting quark-gluon plasma

We extend the investigation of jet transport coefficients within the effective dynamical quasiparticle model (DQPM)—constructed to describe nonperturbative QCD phenomena of the strongly interacting quark-gluon plasma (sQGP) in line with the lattice QCD equation of state—by accounting for inelastic 2→3 reactions with gluon radiation in addition to the elastic scattering of partons. The elastic and inelastic reactions are calculated explicitly within leading-order Feynman diagrams with effective propagators and vertices from the DQPM by accounting for all channels and their interferences. We present the results for the jet transport coefficients such as the transverse momentum transfer squared q̂ per unit length as well as the energy loss dE/dx per unit length in the sQGP and investigate their dependence on the temperature T and momentum of the jet parton depending on the choice of the strong coupling constant αs in thermal, jet parton, and radiative vertices. For the latter, we consider different scenarios used in the literature and find a very strong dependence of q̂ and dE/dx on the choice of αs. Moreover, we explore the relation of q̂/T3 to the ratio of specific shear viscosity to entropy density η/s and show that the ratio T3/q̂ to η/s has a strong T dependence—especially when approaching Tc—on the choice of αs in scattering vertices. Published by the American Physical Society 2024

NeuSIM4: A comprehensive GEANT4 based neutron simulation code

A new neutron SIMulation program based on the versatile GEANT4 toolkit, neuSIM4, has been developed to describe interactions of neutrons in the NE213 liquid scintillator from 0.1 to 3000 MeV. neuSIM4 is designed to accommodate complicated modern detector geometry setups with multiple scintillator detectors, each of which can be outfitted with more than one photo-multiplier. To address a broad spectrum of neutron energies, two new neutron interaction physics models, KSCIN and NxQMD, have been implemented in GEANT4. For neutrons with energy below 110 MeV, we incorporate a total of eleven neutron induced reaction channels on hydrogen and carbon nuclei, including nine carbon inelastic reaction channels, into KSCIN. Beyond 110 MeV, we implement a neutron induced reaction model, NxQMD, in GEANT4. We use its results as reference to evaluate other neutron-interaction physics models in GEANT4. We find that results from an existing cascade physics model (INCL) in GEANT4 agree very well with the results from NxQMD, and results from both codes agree with new and existing light response data. To connect KSCIN to NxQMD or INCL, we introduce a transition region where the contribution of neuSIM4 linearly decreases with corresponding increased contributions from NxQMD or INCL. To demonstrate the application of the new code, we simulate the light response and performance of a 2 × 2 m2 neutron detector wall array consisting of 25 2m-long scintillation bars. We are able to compare the predicted light response functions to the shape of the experimental response functions and calculate the efficiency of the neutron detector array for neutron energies up to 200 MeV. These simulation results will be pivotal for understanding the performance of modern neutron arrays with intricate geometries, especially in the measurements of neutron energy spectra in heavy-ion reactions.

Coherent γ*-nucleus scattering and coherent nuclear states

In the context of a McLerran-Venugopalan (MV) model for a large nucleus, coherent scattering of a virtual photon on that nucleus is evaluated in the A− = 0 gauge, the gauge appropriate for the target nucleus. The evaluation of the scattering in A− = 0 gauge is very intricate compared to the usual A+ = 0 gauge evaluation natural for the scattering process, but has the advantage of directly giving the scattering in terms of a partonic description of the nucleus. In the limit where a tagged forward jet puts the dipole-nucleus scattering in the saturation regime the coherent reactions are equal to the inelastic reactions. In terms of the nuclear wave function the coherent reactions come from color singlet and zero total transverse momentum quark-antiquark pairs in the wave function and in the saturation regime the nuclear wave function is a coherent state for these pairs. In the saturation region half of all quarks (or antiquarks) come from zero momentum and color charge pairs.

Prospects to study hyperon-nucleon interactions at BESIII* *Supported by the National Natural Science Foundation of China (NSFC) (11935018, 11875054, 12165022), the Chinese Academy of Sciences (CAS) Key Research Program of Frontier Sciences (QYZDJ-SSW-SLH003), and the Fundamental Research Project of Yunnan Province, China (202301AT070162)

The prospects to study hyperon-nucleus/nucleon interactions at BESIII and similar colliders are analyzed in this paper. Utilizing the large quantity of hyperons produced by the decay of 10 billion and 2.7 billion collected at BESIII, the cross sections of several specific elastic and inelastic hyperon-nucleus reactions can be measured via scattering between hyperons and nucleus in the dense objects of the BESIII detector. Subsequently, the cross sections of the corresponding hyperon-nucleon interactions can be extracted from further phenomenological calculations. The interactions between antihyperons and nucleus/nucleon, including scattering and annihilation, can also be studied using the method proposed in this study. The results will definitely benefit the realization of precise probes for hyperon-nuclei/nucleus interactions and establish constraints to study the potential of strong interaction, the origin of color confinement, a unified model for baryon-baryon interactions, and the internal structure of neutron stars. In addition, the desirable prospects of corresponding studies in the future Super Tau-Charm Factory (STCF) are discussed and estimated in this study.

Towards a Timepix3 Radiation Monitor for the Accelerator Mixed Radiation Field: Characterisation with Protons and Alphas from 0.6 MeV to 5.6 MeV

A Timepix3 detector with a 300 μm silicon sensor has been studied as a novel radiation monitor for the mixed radiation field at the Large Hadron Collider at CERN. This work describes a test campaign carried out at Centro Nacional de Aceleradores with quasi-mono energetic protons (alphas) from 0.6 (1) to 5 (5.6) MeV, where orthogonal irradiations are used to obtain an energy calibration, and a low-energy angular scan to estimate the front dead layer thickness of the sensor. The detector is operated in hole collection mode and at a partial bias of 250 μm at 50 V, which increases the charge sharing among pixels to mitigate the signal saturation at high energy depositions. The data, supported by FLUKA Monte Carlo simulations of energy losses in the sensor, show that the Timepix3 monitor operates in a linear regime up to energy depositions of around 600 keV per pixel and 2 MeV per cluster. As a result, the detector has been found to be suitable for measuring charged particle fluxes in the LHC mixed radiation field within the linear calibration regime, with the partial exception of inelastic nuclear reaction hits (mostly from neutrons).

Extending the panel of inelastic scattering reactions availaible for dosimetry: Definition of the experimental campaign at the JSI TRIGA reactor

The epithermal to fast neutron domain lacks reactions to enhance the knowledge of spectrum in this energy range (1 keV to 1 MeV). Previous studies on this topic focused on 94Zr(n, γ) capture and 117Sn(n, n′) inelastic reactions. In the framework of a research collaboration between the French Atomic and Alternative Energies Commission (CEA) and the Jožef Stefan Institute (JSI), a new project consists in finding new inelastic reactions suitable for dosimetry. This paper describes the selection process of new reactions to be tested in an experimental campaign at JSI.

Superheavy nuclei and other exotics – opportunities at SPIRAL2 and S3

The structure of very heavy and superheavy nuclei (SHN) as well as the location of the next proton and neutron shell closures beyond 208Pb is still one of the most intriguing topics in modern nuclear physics [1]. Worldwide competitive, high beam intensities provided by the accelerator facility SPIRAL2 at GANIL which started operation recently, will cover in future all ions up to uranium thanks to the new injector project NEWGAIN. Combined with the separator-spectrometer installation S3 [3], it will provide the instrumental prerequisites for an ambitious science program. Apart from SHN/SHE research, the envisaged physics case at S3 covers, among other, the structure of N=Z nuclei, low energy physics (fundamental properties of the atomic nucleus etc.), interdisciplinary research, atomic physics and reaction studies (fission, deep inelastic reactions etc.). The state of the art of the field is discussed in this paper with an emphasis on the role of the odd particle(s) in odd-even, even-odd and odd-odd nuclei and the consequences for nuclear structure features like K-isomers, trends of single-particle energies as a function of deformation, and the competition of spontaneous fission (SF) and α decay. As an alternative approach to produce heavy and in particular more neutron-rich nuclear species multi-nucleon transfer reactions are briefly discussed as well.

Deuteron Optical Model Calculations for Elastic and Inelastic Reactions on 14N, 16O, 27Al Target Nuclei

Nuclear reaction cross sections have a key role in nuclear radioisotope production research. It is also an important part of applied fields such as energy production and experimental nuclear studies. It has been the subject of theoretical studies such as elucidating the nuclear structure and preparing and testing nuclear reaction models. It has become a very useful tool, especially for determining nuclear optical model parameters. In this study differential cross sections were calculated for elastic and inelastic scattering of 14-15 MeV energy range deuterons from 14N, 16O and 27Al. Calculation were carried out with TALYS 1.96/2.0 nuclear reaction code. Calculations include determining the deuteron optical model that match the experimental data. The values calculated with theoretical models were compared with experimental data obtained from the literature. While such studies are important for testing nuclear reaction models, they are also important for encouraging the preparation of nuclear reaction codes.

State-Specific Dissociation and Inelastic Rate Constants for Collisions of H2 with H and He

Recent reports have called for planetary probe missions to the outer planets of the solar system. To support these missions, kinetic data for processes involving molecular hydrogen are required in order to conduct the necessary computational and experimental studies. The data available in the literature are currently incomplete owing to the broad range of temperatures required for these computational studies. In this work, the rate constants for the state-specific dissociation and inelastic scattering collisions between molecular hydrogen and H and He were calculated using the quasi-classical trajectory method in a range of translational energy between 0.1 and 15 eV. Comparisons with the state-specific cross sections reported in the literature are made for both systems. The full set of ro-vibrational state-specific cross sections is then used to compute the corresponding dissociation and inelastic reaction rate constants between 1000 and 30,000 K. Thermal and state-specific data are made available.

Theoretical study of inelastic processes in collisions of Y and Y+ with hydrogen atom

ABSTRACT Utilizing a simplified quantum model approach, the low-energy inelastic collision processes between yttrium atoms (ions) and hydrogen atoms have been studied. Rate coefficients corresponding to the mutual neutralization, ion-pair formation, excitation, and de-excitation processes for the above collision systems have been provided in the temperature range of 1000–10 000 K. Three ionic states and 73 covalent states are considered in calculations for the collisions of yttrium atoms with hydrogen atoms, which include six molecular symmetries and 4074 partial inelastic reaction processes. For the collisions of yttrium ions with hydrogen atoms, one ionic state and 116 covalent states are included, which are related to three molecular symmetries and 13 572 partial inelastic collision processes. It is found that the rate coefficients for the mutual neutralization process have a maximum at T = 6000 K, which is an order of magnitude higher than those of other processes. Notably, the positions of optimal windows for the collisions of yttrium atoms and ions with hydrogen atoms are found near electronic binding energy −2 eV (Y) and −4.4 eV (Y+), respectively. The scattering channels located in or near these optimal windows have intermediate-to-large rate coefficients (greater than 10−12 cm3 s−1). The reported data should be useful in the study of non-local thermodynamic equilibrium modelling.

Effect of ion-induced secondary radiations on the formation of extended defects and radiolysis beyond the range of swift 12C, 50Ti, and 52Cr ions in LiF

The objective of this research is to study the role of ion-induced secondary radiations on structural damage in LiF crystals irradiated with ∼ 10 MeV/u energy 12C, 50Ti, and 52Cr ions using experimental methods of nanoindentation, Atomic Force Microscopy, optical absorption, depth-resolved photoluminescence and chemical etching. In LiF crystals irradiated at room temperature with 50Ti and 52Cr ions, the chemical etching method revealed formation of nano-sized colloids in a wide area (up to one mm) beyond the ion penetration depth. Annealing experiments on irradiated samples at temperatures above 620 K, show enhanced manifestations of radiolysis in ion-irradiated and beyond-range areas accompanied by the emission of radiolysis residues. The multicomponent secondary radiation following the ion-induced inelastic nuclear reactions is discussed as the plausible mechanism of the observed long-range damage.

Intense γ -Photon and High-Energy Electron Production by Neutron Irradiation: Effects of Nuclear Excitations on Reactor Materials

The effects of neutron irradiation on materials are often interpreted in terms of atomic recoils, initiated by neutron impacts and producing crystal lattice defects. In addition, there is a remarkable two-step process, strongly pronounced in the medium-weight and heavy elements. This process involves the generation of energetic {\gamma} photons in nonelastic collisions of neutrons with atomic nuclei, achieved via capture and inelastic reactions. Subsequently, high-energy electrons are excited through the scattering of {\gamma} photons by the atomic electrons. We derive and validate equations enabling a fast and robust evaluation of photon and electron fluxes produced by the neutrons in the bulk of materials. The two-step n-{\gamma}-e scattering creates a nonequilibrium dynamically fluctuating steady-state population of high-energy electrons, with the spectra of photon and electron energies extending well into the mega-electron-volt range. This stimulates vacancy diffusion through electron-triggered atomic recoils, primarily involving vacancy-impurity dissociation, even if thermal activation is ineffective. Tungsten converts the energy of fusion or fission neutrons into a flux of {\gamma} radiation at the conversion efficiency approaching 99%, with implications for structural materials, superconductors, and insulators, as well as phenomena like corrosion, and helium and hydrogen isotope retention.

Large collectivity in 29Ne at the boundary of the island of inversion

The heavy-ion inelastic scattering of the neutron-rich nucleus 29Ne to its excited states was studied using a 100.1 MeV/u 29Ne rare isotope beam on 181Ta and 9Be targets. The combined setup consisting of the GRETINA array, the TRIPLEX device and the S800 Spectrograph facilitates the simultaneous measurements of the two inelastic reactions, providing the first measurement of the transition strengths for this isotope. A sizable E2 strength B(E2↑) which amounts to 163(30) e2fm4 was determined in the excitation to the 931-keV state, demonstrating a large degree of collectivity. The present results of B(E2↑) are compared to various shell-model calculations, confirming the role of intruder configurations in 29Ne at the boundary of the island of inversion.

Coulomb divergence in (d,p) reactions based on Faddeev-Alt-Grassberger-Sandhas equation

The Faddeev-Alt-Grassberger-Sandhas equation is the most performance formalism to describe the (d,p) reactions since it can exactly and simultaneously treat the elastic, inelastic, transfer, and breakup reactions. In this brief report, we describe the progress and some main difficulties in treating the Coulomb interaction in the direct elastic scattering of the (d,p) reaction by using the Faddeev-Alt-Grassberger-Sandhas equation.

Transuranium isotopes at ISAC/TRIUMF

The production of transuranium isotopes has been demonstrated at the Isotope Separation and ACceleration (ISAC) facility. In particular a laser-ionized 239Pu beam, extracted from a uranium carbide target, was investigated. The experimental work was complemented by Geant4 simulations, modelling the impact of secondary particles on the creation of transuranium isotopes through inelastic nuclear reactions. Theoretical production cross sections were derived and compared to experimental results, leading to a discussion on boundary conditions for the release of neptunium and plutonium from ISAC uranium carbide targets.

Risk Management of a Fusion Facility: Radiation Protection and Safety Integrated Approach for the Sorgentina-RF Project

The Sorgentina-RF project will use fusion neutrons to produce 99Mo, a precursor of 99mTc, by irradiating natural molybdenum. 99Mo is produced by means of the inelastic reaction 100Mo(n, 2n)99Mo on 100Mo, which is an isotope of natural Mo. From a functional point of view, the project consists of two parts: an irradiation neutron source at 14 MeV and a radiochemistry facility dedicated to the extraction of 99Mo from the solid sample irradiated by the neutron source. Given the degree of complexity of such a facility, the risk management strategy is based on an integrated approach that combines the engineering method of safety with that of radiation protection. Therefore, design issues were studied and systems were planned according to both radiation protection and safety criteria already in the preliminary phase, allowing a general strengthening of the safety of the plant. This work discusses the preventive analysis and the related activities to identify the ways in which potential exposures to radiation may occur. In particular, the preliminary safety analysis is presented for the innovative rotating target, developed for the project, and, accordingly, some specific technical solutions are given to refine the initial design of the facility.

SuSAv2 model for inelastic neutrino-nucleus scattering

The susperscaling model SuSAv2, already available for charged-current neutrino-nucleus cross sections in the quasielastic region, is extended to the full inelastic regime. In the model the resonance production and deep inelastic reactions are described through the extension to the neutrino sector of the SuSAv2 inelastic model developed for ($e$, ${e}^{\ensuremath{'}}$) reactions, which combines phenomenological structure functions with a nuclear scaling function. This work also compares two different descriptions of the $\mathrm{\ensuremath{\Delta}}$ resonance region, one based on a global scaling function for the full inelastic spectrum and the other on a semiphenomenological $\mathrm{\ensuremath{\Delta}}$ scaling function extracted from ($e$, ${e}^{\ensuremath{'}}$) data for this specific region and updated with respect to previous work. The results of the model are tested against ($e$, ${e}^{\ensuremath{'}}$) data on $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, $^{40}\mathrm{Ca}$, and $^{40}\mathrm{Ar}$ and applied to the study of the charged current inclusive neutrino cross-section on $^{12}\mathrm{C}$ and $^{40}\mathrm{Ar}$ measured by the T2K, MicroBooNE, ArgoNEUT, and MINERvA experiments, thus covering several kinematical regions.

Nuclear reactions in artificial traps

Abstract Coupled-channel two-particle systems bound by a harmonic trap are discussed in the present paper. Under assumption of short-range interactions, the formula that relates the energy levels of such trapped systems to phase shifts and inelasticity of coupled-channel reactions can be obtained in a closed form. The present paper may set some groundworks toward extracting scattering amplitudes of inelastic nuclear reactions from ab initio calculations of discrete levels of many-nucleon systems in a harmonic trap.