Incident Particle Energy Research Articles

The effect of CD4 injection on WD molecule sputtering at the divertor target in EAST

Tungsten (W) is one of the preferred plasma-facing materials for future fusion reactors because of the advantages of high melting point, low physical sputtering rate and low fuel retention. The lifetime and service performance of W materials are limited by erosion processes. In recent years, tungsten deuteride molecular (WD) sputtering has been discovered in tokamak. Studying WD sputtering helps to better understand the erosion of tungsten materials in tokamak. EAST adopts the method of injecting impurity gas in the divertor to alleviate the particle flux and heat flux bombarding the tungsten divertor, and CD4 is one of the impurities used. CD4 injection experiments on EAST show that after CD4 is injected from the upper outer (UO) divertor target, despite that the electron temperature (Te) around the strike point on the UO divertor target drops to about 8 eV, strong WD sputtering occurs in the far scrape-off layer (SOL) region. The divertor probe data shows that after CD4 injection, the particle flux from the upstream plasma onto the divertor split into two bands, creating a new particle flux strike point in the far SOL region. The energy of incident particles at the original strike point is significantly reduced, while the energy of incident particles at the far SOL region is enhanced. The edge electron density profile at mid-plane indicates that CD4 injection causes an increase of density in the SOL, which could improve the coupling of Lower-Hybrid Wave (LHW) with the edge plasma as evidenced by the decreasing reflected power of LHW. The increase in absorbed power of LHW could change the particle and energy transport in the edge plasma, thus plays an important role in the enhanced WD sputtering in the far SOL region after CD4 injection.

Transient behaviour analysis in silicon carbide alpha particle detector using TCAD and SRIM simulation

Time response characteristics of α particle detector are crucial for monitoring radiation fields varied with time and its characterization of pulse radiation field. Here, SRIM-informed TCAD simulation is utilized to visually investigate the transient behaviors of carriers and alpha particles in 4H-SiC Schottky barrier detectors for the time response characteristics. We identified external bias voltage and incident particle energy as key factors to influence transient current pulse broadening. Low-energy alpha particles result in low initial kinetic energy of the ionization-generated carriers, leading to transient current broadening and reduced time resolution characteristics. Conversely, high-energy alpha particles ionize carrier with high drift velocity, preventing the broadening effect. Our simulation provides a planform and valuable guidance for optimizing alpha particle detector, selecting appropriate bias voltages, and enhancing time resolution capabilities.

Simulation Analysis of Factors Affecting the Quantum Tunneling Effect in 1D Double Potential Barriers Structures

The working principle of a large number of modern scientific equipment has been applied to the quantum tunneling effect. Although the explanations for the relevant principles of this effect are clarified, the calculation process is very complex and difficult to understand. Previous studies combine specific applications without theoretical model references. This study adopts the method of using the time-independent Schrodinger equation to solve the wave function, which is more convenient to obtain the expression of transmission probability. Then, one discusses the relationship between transmission probability and potential barrier width, potential barrier spacing, and incident particle energy. The experimental results show that the transmission probability decreases exponentially from 1 to 0 as the potential barrier width gradually increases. As the potential barrier width increases, the transmission probability exhibits a clear periodic oscillation relationship, the oscillation period remains unchanged, and this paper derives the relationship between the oscillation period and the potential barrier width. As the incident energy of particles gradually increases, the transmission probability exhibits periodic changes, and the minimum value of transmission probability increases with the periodic changes. Based on the analysis, the smaller the potential barrier width, the greater the incident energy, and the more likely quantum tunneling occurs.

Radiative emissions from charge exchange processes in collisions of 0.7–10.0 keV He[formula omitted] with N[formula omitted] and O2 molecules

We present an experimental study of the dissociative excitation in the collision of helium ions with nitrogen and oxygen molecules for collision energy of 0.7–10.0 keV. Absolute emission cross sections are measured and reported for the most pronounced nitrogen and oxygen atomic and ionic lines in vacuum ultraviolet (80–130nm) and visible (380–670nm) spectral regions. Remarkable similarities of the processes realized in He++N2 and He++O2 collision systems are observed. We present polarization measurements for He++N2 collision system.The emission of excited dissociative products was detected using an improved high-resolution optical spectroscopy method. This method incorporates the retarding potential method and a high resolution electrostatic energy analyzer to precisely measure the energy of incident particles and the energy of dispersion. The improvement in the optical sensitivity allows us to measure the cross section on the order of 10−19 cm2 or lower.

Інклюзивна реакція фрагментації дейтронів при зіткненні їх з дейтронами мішені

Within the framework of eikonal approximation and the double folding model, a formalism for calculating the inclusive spectra of particles emitted from the deuteron breakup reaction is proposed. The spectra of protons from the reaction 2H(d,p) at an incident particle energy of 59.9 MeV are described. The calculated values of cross-sections are in good agreement with the corresponding experimental data.

Study of energy loss, range, and stopping time for proton in germanium and copper materials

Abstract In this study, the energy loss, range, and stopping time were calculated using the Bethe theory for protons in germanium and copper materials over an energy range of 0.01–1,000 MeV. The mathematical equations were programmed and implemented using MATLAB2013 to obtain the results for the relative mass stopping power and range, illustrated in tables and graphs. The computed results from the Bethe and Ziegler equations were compared with the experimental results from Pstar. The results showed a difference between the experimental and theoretical results at the beginning of the range used in the Bethe equation because it is a quantized equation that is not suitable for low energies. Hence, a correction term was proposed for the Bethe equation to correct the results at low energies, which produced negative values. On the other hand, the Ziegler equation showed good agreement along the range used as it is a semi-empirical equation. The range and stopping time of the incident particle increased with increasing incident particle energy in the mentioned materials.

The effect of multiple collisions on the electronic stopping losses

The paper considers the question of the dependence of electronic stopping dE/dx on the measurement technique. Usually, when using the transmission geometry, the value of electron stopping is defined as the ratio of the energy loss of the particle after passing through the film to the thickness of the film d. It is shown that this procedure provides overestimated results at low collision energies. Using the computer simulation, the dependence of the ratio of the particle mean trajectory length L in the film to its thickness d on the particle energy E has been obtained. Experimental values of inelastic loss dE/dx for transmission geometry were corrected for the L/d ratio and compared with the results of the “backscattering geometry” experiments. A good agreement of the corrected “transmission” data with the “backscattering” data has been demonstrated for the H-Cu, H-Ag and H-Au systems. The incident particle energies E0 ranged from 0.5 to 20 keV.

Generic temporal quantization criterion in dynamic resonant tunneling for current suppression

It is well known that resonant tunneling can significantly increase the tunneling current when the incident particle's energy (Ω) is equal to the resonant energy (ΩR). However, recent studies have shown that complex current structures can emerge when the resonant energy varies in time. While these temporal variations typically increase the current, there is a specific condition under which the current is significantly suppressed. This condition, which has previously only been presented for specific cases, is characterized by the equation12∫t1t1|Ω−ΩR(t′)|dt′=π(n−14) for =1,2,... , where t1,2 are the solutions of ΩR(t1,2)=Ω.In this paper, we present for the first time a full derivation of this expression using the Quasi-Bound Super State method and demonstrate it for various perturbation scenarios with the following temporal profiles: Gaussian, hyperbolic secant, harmonic, and smooth rectangular.The derivation of this quantization rule has practical implications beyond the intellectual realm. The specific spectral structure of these systems has implications for nanotechnology (e.g., frequency-controlled transistors) and the understanding of biological and biochemical processes (e.g., odor detection).

Estimation of different calculation models for evaluating heavy ion-induced damage in plasma facing materials

In a fusion reactor, plasma-facing materials are bombarded by various energetic particles (such as neutrons) from fusion reactions, leading to inevitable irradiation damages. These damages can significantly affect the material servicing life time and threaten the safety of fusion reactors. Accurate and consistent evaluation of irradiation damage is quite important to investigate the evolution mechanism of irradiation defect. In this study, the irradiation damage of tungsten caused by high-energy particles were evaluated using the SRIM code and molecular dynamics simulations. The accuracy of three atomic displacements calculation models, i.e., VAC model, NRT model, and arc-dpa model, under two computational modes of SRIM (the K-P mode and F-C mode) were discussed. It was found that with the increase of the incident particle atomic number, the peak depth of displacement moved to the shallow layer and increased in peak height, while the trend was opposite with the increase of the incident particle energy. As to the different calculation modes, the F-C and K-P modes produced a ratio of vacancies of about 1.8 times in the VAC model. What's more, the VAC model and NRT model predicted results consistent with molecular dynamics simulation results at lower energy ranges (approximately <100 eV), but deviated from them as the energy increased. In contrast, the arc-dpa model exhibited good consistency with the molecular dynamics simulations and had higher accuracy. Therefore, it is recommended to use the arc-dpa model under the K-P mode for the calculation of atomic displacement. This model can accurately and quickly calculate the irradiation damage level caused by high-energy particle irradiation in fusion reactors.

Investigation of charged-particle induced reactions on 27Al up to 100 MeV leading to the formation of 22Na and 24Na

Abstract Studies using theoretical models are of great importance for understanding of reaction process and its nature. In this study, nuclear level density model calculations of the cross sections of 27Al are investigated by using TALYS 1.96 computer code. The cross section calculations of 27Al(α,x)22Na, 27Al(α,x)24Na, 27Al(3He,x)22Na, 27Al(3He,x)24Na, 27Al(p,x)22Na and 27Al(p,x)24Na reactions were carried out for incident particle energy up to 100 MeV. In these calculations, four nuclear level density models, namely constant temperature model (CTM), back-shifted Fermi gas model (BSFGM), generalized superfluid model (GSM) and recently proposed semi-classical Fermi gas model (CSCFGM) are used. This model is developed using the simplest model BSFGM. The most obvious difference between CSCFGM and other models is the inclusion of the collective effects in the base of the formulation. The predicted results are discussed and compared with each other and the available experimental data taken from EXFOR library. In order to better evaluate the model results, chi-squared values are calculated and compared with each other for all analyzed reactions. According to the chi-squared results, CSCFGM gives closer predictions to the experimental data compared with the other models in 4 of the 6 analyzed reactions. Therefore, in this study, it is presented that this model can be reliably used in the reaction cross section calculations.

Cluster time measurement with CEPC calorimeter

We have developed an algorithm dedicated to timing reconstruction in highly granular calorimeters (HGC). The performance of this algorithm is evaluated on an electromagnetic calorimeter (ECAL) with geometries comparable to the electromagnetic compartment (CE-E) of the CMS endcap calorimeter upgrade at HL-LHC and conceptual Particle Flow oriented ECAL’s for future Higgs factories. The time response of individual channel is parameterized according to the CMS experimental result (Akchurin et al. in Nucl Instrum Methods Phys Res Sect A Accel Spectrom Detect Assoc Equip 859:31, 2017). The particle Time-of-Flight (ToF) can be measured with a resolution of 5–20 ps for electromagnetic (EM) showers and 80–160 ps for hadronic showers above 1 GeV. The presented algorithm provides comparable reconstruction with the E_{textrm{hit}}^2 weighting strategy and can significantly improve the time resolution compared to a simple averaging of the fast component of the time spectrum. The effects of three detector configurations are also quantified in this study. ToF resolution depends linearly on the timing resolution of a single silicon sensor and improves statistically with increasing incident particle energy. The timing layers at depth of 6–9 radiation lengths provide higher timing performance for EM showers. A clustering algorithm that vetoes isolated hits improves ToF resolution.

Comparison of morphological characteristics for alpha tracks in CR-39 using different radon monitors

CR-39 is a solid nuclear track detector that is commonly used for long-term passive radon monitoring. For a specific incident particle, etching condition and type of CR-39, the morphology of the nuclear tracks in CR-39 varies with the energy and angle of incident particles. This study systematically compares the performance of six different passive radon monitors from the perspective of nuclear track morphology using both theoretical calculations and experiments. Based on different shapes of exposure chambers for these monitors, different strategies for dealing with incident α particles can be observed, especially for those emitted from deposited progeny on the inner wall. These characteristics contribute to the strengths and weaknesses of each monitor in terms of efficiency, uncertainty, robustness in measurement, and consistency of track morphology. The results of this study revealed that the optimisation of the radon monitor should be multidirectional and situation-oriented. It was expected to be helpful to improve radon measurement using these monitors.

Effects of different He+ irradiating ion energies on the evolution behavior of helium bubbles in dispersion-strengthened NiMo–Y2O3NP alloys

The nickel-based NiMo–Y2O3NP alloy has been identified as a potential structural material to be used for advanced reactors. In this study, the microstructural evolution behavior of oxide-dispersion-strengthened NiMo–Y2O3 alloys irradiated with He+ ions possessing different incident particle energies (0.5, 1.0, and 2.0 MeV) was investigated by transmission electron microscopy, simulation calculations, and nanoindentation tests. The experimental results showed that helium bubbles were generated in all three irradiated samples of the NiMo–Y2O3NP alloy, where more than half of the bubbles were smaller than 4 nm in diameter. As the energy of the incident He+ irradiating ion increased, the number density of helium bubbles decreased, but their average size increased within the tolerance of the error, inducing an increase in the volume fraction of helium bubbles in the damage peak region. This could be attributed to the decrease in helium concentration and increase in the ratio of vacancies to helium atoms (Vac./He) in helium bubbles in the damage peak region. In addition, the average nanohardness of the irradiated samples S1, S2, and S3 was higher than that of the unirradiated sample S0. In this study, we evaluated the effects of He+ irradiating ion energy on the evolution behavior of helium bubbles in the alloy, providing a reference for further research on the evolution behavior of helium-induced damage defects of structural materials.

Kollektif Etkilerin Nötron Yakalama Reaksiyon Tesir Kesiti Üzerindeki Rolü

The neutron capture reaction is one of the important reactions that provides the determination of the structural properties of the nucleus and detailed information about the capture reaction mechanisms. In this study, cross section values of 89Y(n,g)90Y reaction, which is a neutron capture reaction, were calculated with TALYS computer code up to 10 MeV incident particle energy using different level density models. In the calculations, back-shifted Fermi gas model (BSFGM), constant temperature model (CTM), generalized superfluid model (GSM), and collective semi-classical Fermi gas model (CSCFGM) were preferred. The obtained results were compared with the data taken from the experimental database. In addition, the quality factors of the models were presented in the table. As a result of the calculations, it has been presented that the CSCFGM, which takes the collective effects into account basically, is more successful model to reproduce the experimental data and that the collective effects play a dominant role on the neutron capture reaction cross sections. Therefore, it has been demonstrated that CSCFGM is a model, which can be used for neutron capture reaction analyses in the future.

Інклюзивні реакції зриву та фрагментації легких кластерних ядер при проміжних енергіях

In the framework of eiconal approximation and the double folding model, a formalism for calculating inclusive spectra of particles from stripping and fragmentation reactions involving light cluster nuclei is proposed. The cross-section of the 12C(3He, d)13N reaction at an incident particle energy of 81.4 MeV and the proton spectra from the deuteron fragmentation reaction with 56 MeV energies by 12C and 27Al nuclei are described. The calculated values satisfactorily fit the corresponding experimental data.

On the Self-Shielding in the Unresolved Resonance Range

Abstract Resonance behavior is a feature of nuclear reaction cross sections. Resonance density increases with increasing incident particle energy and they begin to overlap, until they can no longer be resolved experimentally, but they still contribute to self-shielding and must be accounted for. This is usually done by representing them with statistical average parameters according to methods and approximations described in standard text-books. Self-shielding factors are commonly used in deterministic transport codes, while statistical Monte Carlo codes use probability tables or multiband parameters. An exercise was conducted at the International Atomic Energy Agency (IAEA) to validate codes and methods for generating data that account for self-shielding in deterministic and Monte Carlo codes. A simple numerical model problem was defined, considering a sphere of 1 m radius with a 20 MeV isotropic neutron source at the center. The chosen material for testing was 139La from the ENDF/B-VIII.0 library, which clearly showed anomalous behavior.

Measurement of three-dimensional track profiles on CR-39s based on the photometric stereo method.

To obtain more information about incident particles, a new method for measuring three-dimensional track profiles formed on CR-39s based on the photometric stereo method was developed. A new optical microscope system with 16 lasers and a complementary metal-oxide-semiconductor camera was built to automatically capture the reflecting track images illuminated by the laser beams from different angles, and the track profiles were three-dimensionally reconstructed using a self-developed software. To verify the reconstruction results of the track profiles, both the openings and depth were measured with an atomic force microscope. The results showed that the relative deviations between the two methods of the openings were about 5.5% and the deviations of the depth were about 8.0%. At present, the reconstruction speed of a three-dimensional track profile is a factor of 400 greater than that of the atomic force microscope. The new method shows great potential for rapid reconstruction of numerous track morphologies. It is expected to be helpful for further studies on the energy and angle discrimination of incident particles in the field of nuclear measurements.

Low Energy Ar&lt;sup&gt;+&lt;/sup&gt; Ions Scattering from SiO&lt;sub&gt;2 &lt;/sub&gt;(001)&amp;lt;Ῑ10&amp;gt; Surface under Grazing Incidence

This article presents the results of computer modeling of small-angle scattering of Ar+ ions from the surface of the SiO2 thin film under bombardment by low-energy. The study of the trajectory of the scattered ions showed that the trajectories with two focuses are observed not only near the center of the semichannel but also nearby the surface of the atomic chain. An increase in the value of the initial energy of incident particles leads to a narrowing of the trajectory of the scattered ions, which leads to the appearance of low-intensity peaks in the energy spectrum of the scattered ions.

Comparison of JET inner wall erosion in the first three ITER-like wall campaigns

• Rate and distribution of W erosion were the same in first 2 JET-ILW campaigns and JET-C campaigns. • Rate of W erosion increased by a factor of 1.6 in the third JET-ILW campaign. • Erosion of Be decreased by a factor of about 2 from JET-ILW 1 to JET-ILW 2 campaign. • Erosion of Be remained unchanged from the second to the third JET-ILW campaign. • Changes in Be migration and mean particle energy to the inner wall might be the reason for observed changes. The net erosion of material from recessed areas of the JET main chamber inner wall during the first three ITER-like wall (JET-ILW) campaigns was studied using long-term samples with Be and W marker layers. The samples were analyzed using elastic backscattering spectrometry (EBS) before and after each campaign. It was found that the erosion for both Be and W was roughly homogeneously distributed in both toroidal and poloidal directions, possibly with a small maximum near the middle of the inner wall and a minimum near the bottom of the wall, as well as several toroidal distribution features. The net erosion rate of Be decreased by a factor of two between the first and the second JET-ILW campaigns, and remained unchanged during the third JET-ILW campaign. Three possible explanations are presented: a campaign to test the power handling capability of the limiter in ILW1, a change in incident particle energy distribution, and a change in limiter to divertor discharge time ratio. The net erosion rate of W remained almost unchanged through the first two JET-ILW campaigns. In the third JET-ILW campaign the net erosion rate of W from the inner wall was about 1.6 times higher than previously observed, indicating a change in the energy spectrum of particles eroding the inner wall, and the occasional addition of Kr and Xe to the fuelling.

A Geant4-DNA Evaluation of Radiation-Induced DNA Damage on a Human Fibroblast.

Simple SummaryDNA damage caused by ionizing radiation in a human fibroblast cell evaluated by the Geant4-DNA Monte Carlo toolkit is presented. A validation study using a computational geometric human DNA model was then carried out, and the calculated DNA damage as a function of particle type and energy is presented. The results of this work showed a significant improvement on past work and were consistent with recent radiobiological experimental data, such as damage yields. This work and the developed methodology could impact a broad number of research fields in which the understanding of radiation effects is crucial, such as cancer radiotherapy, space science, and medical physics.Accurately modeling the radiobiological mechanisms responsible for the induction of DNA damage remains a major scientific challenge, particularly for understanding the effects of low doses of ionizing radiation on living beings, such as the induction of carcinogenesis. A computational approach based on the Monte Carlo technique to simulate track structures in a biological medium is currently the most reliable method for calculating the early effects induced by ionizing radiation on DNA, the primary cellular target of such effects. The Geant4-DNA Monte Carlo toolkit can simulate not only the physical, but also the physico-chemical and chemical stages of water radiolysis. These stages can be combined with simplified geometric models of biological targets, such as DNA, to assess direct and indirect early DNA damage. In this study, DNA damage induced in a human fibroblast cell was evaluated using Geant4-DNA as a function of incident particle type (gammas, protons, and alphas) and energy. The resulting double-strand break yields as a function of linear energy transfer closely reproduced recent experimental data. Other quantities, such as fragment length distribution, scavengeable damage fraction, and time evolution of damage within an analytical repair model also supported the plausibility of predicting DNA damage using Geant4-DNA.The complete simulation chain application “molecularDNA”, an example for users of Geant4-DNA, will soon be distributed through Geant4.