Ne Ions Research Articles

Assessing the impact of valence sd neutrons and protons on fusion

Experimental above-barrier fusion cross-sections for $^{17}$F + $^{12}$C are compared to the fusion excitation functions for $^{16,18}$O, $^{19}$F, and $^{20}$Ne ions on a carbon target. In comparing the different systems both the differing static size of the incident ions and changes in fusion barrier are accounted for by examining the reduced fusion cross-section. Remaining trends of the fusion cross-section above the barrier which reflect the sensitive interplay of the sd protons and neutrons are observed. The experimental data are also compared to both a widely-used analytical model of near-barrier fusion, as well as a time-dependent Hartree-Fock model. Both models fail to describe the trends observed.

20Ne ion range and fragmentation cross-sections in various targets for space shielding and hadrontherapy applications: A Monte Carlo simulation study

The computational study of projectile range and partial fragmentation cross-section (PFXS) has been executed for 20Ne ion using Geant4 Monte Carlo simulation toolkit. The interaction of heavy semi-symmetric system for energy range 290 MeV/n−670 MeV/n has been researched on various targets: carbon (C), aluminium (Al), copper (Cu), tin (Sn), lead (Pb), and tantalum (Ta). The range simulated via Geant4 and SRIM software shows an agreement of ~ 99%. The PFXS simulation has been conducted using three models of Geant4: the Binary Cascade (BIC), Liege Intranuclear cascade (INCL++), and Quantum Molecular Dynamics (QMD). The PFXS is computed for heavy (Z = 5–9) and light (Z = 2–4) fragments. These models have been validated by analysing simulation data with experimental and semi-empirical nuclear fragmentation model data. The QMD model provides the best data for PFXS following an odd–even effect for all targets. The BIC and the INCL++ behave in similar manner for high Z target.

Study on the dissolution of β-precipitates in the Zr–1Nb alloy under the influence of Ne ion irradiation

Abstract The stability of β-precipitates in the Zr–1Nb alloy has been studied under Ne ion irradiation of energy 250 keV by insitu transmission electron microscope as a function of irradiation dose. The irradiation was carried out up to ∼136 dpa at 573 K. Microstructural investigations have shown that up to ∼38 dpa, precipitates showed an increase in size, and for irradiation doses >38 dpa, the size of the precipitates was noticed to reduce. Post-irradiation energy-dispersive spectrometry of the specimens revealed the Nb concentration throughout the matrix to be ∼0.8–1.5%. Three-dimensional atom probe tomography was also carried out for irradiated specimens to look for the presence of any nanoclusters. However, Nb clustering was not observed in the specimens. It is proposed that the dissolution of the precipitates may be facilitated by an increase in the solubility limit of Nb in Zr caused by irradiation. The solubility limit may increase by the introduction of defects generated by irradiation and by the destabilization of the β-phase. This may result in back-diffusion of Nb atoms to the matrix by radiation-enhanced diffusion to lower the strain produced by the defects, resulting in the dissolution of the precipitates.

Flowing Atmospheric Pressure Afterglow for Ambient Ionization: Reaction Pathways Revealed by Modeling.

We describe the plasma chemistry in a helium flowing atmospheric pressure afterglow (FAPA) used for analytical spectrometry, by means of a quasi-one-dimensional (1D) plasma chemical kinetics model. We study the effect of typical impurities present in the feed gas, as well as the afterglow in ambient humid air. The model provides the species density profiles in the discharge and afterglow regions and the chemical pathways. We demonstrate that H, N, and O atoms are formed in the discharge region, while the dominant reactive neutral species in the afterglow are O3 and NO. He* and He2* are responsible for Penning ionization of O2, N2, H2O, H2, and N, and especially O and H atoms. Besides, He2+ also contributes to ionization of N2, O2, H2O, and O through charge transfer reactions. From the pool of ions created in the discharge, NO+ and (H2O)3H+ are the dominant ions in the afterglow. Moreover, negatively charged clusters, such as NO3H2O- and NO2H2O-, are formed and their pathway is discussed as well. Our model predictions are in line with earlier observations in the literature about the important reagent ions and provide a comprehensive overview of the underlying pathways. The model explains in detail why helium provides a high analytical sensitivity because of high reagent ion formation by both Penning ionization and charge transfer. Such insights are very valuable for improving the analytical performance of this (and other) ambient desorption/ionization source(s).

Interferometric extraction of photoionization-path amplitudes and phases from time-dependent multiconfiguration self-consistent-field simulations

Bichromatic extreme-ultraviolet pulses from a seeded free-electron laser enable us to measure photoelectron angular distribution (PAD) as a function of the relative phase between the different wavelength components. The time-dependent multiconfiguration self-consistent-field (TD-MCSCF) methods are powerful multielectron computation methods to accurately simulate such photoionization dynamics from the first principles. Here, we propose a method to evaluate the amplitude and phase of each ionization path, which completely determines the photoionization processes, using TD-MCSCF simulation results. The idea is to exploit the capability of TD-MCSCF to calculate the partial wave amplitudes specified by the azimuthal and magnetic angular momenta (l, m) and the m-resolved PAD. The phases of the ionization paths as well as the amplitudes of the paths resulting in the same (l, m) are obtained through global fitting of the expression of the asymmetry parameters to the calculated m-resolved PAD, which depends on the relative phase of the bichromatic field. We apply the present method to ionization of Ne by combined fundamental and second-harmonic extreme ultraviolet pulses, demonstrating that the extracted amplitudes and phases excellently reproduce the asymmetry parameters.

Characterization of a novel large area microdosimeter system for low dose rate radiation environments

A feasibility study is presented on a newly developed microdosimetry system named Octobox, for its application in low dose rate, mixed radiation environments. A full characterization of the device was performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan, out-of-field of various heavy ion radiation fields — 290 MeV/u 12C, 230 MeV/u and 490 MeV/u 28Si and 400 MeV/u 20Ne ions, as well as a low dose rate 222Rn environment at the Australian Nuclear Sciences and Technology Organization (ANSTO). The device was shown to collect adequate statistics in a short period of time when compared to the MicroPlus probe with a single microdosimeter, while accurately measuring microdosimetric quantities and the corresponding average quality factor (Q¯) and dose equivalent (H) of the mixed radiation field. Good agreement of the microdosimetric spectra was also shown with Geant4 simulations for all presented ion fields. Based on the findings in this study, the Octobox is capable of being applied in mixed, low dose rate, radiation environments such as those encountered in space and aviation, as well as in underground mines for radiation protection purposes.

Structural Changes in HPRT Gene of V79 Cells After Irradiation With Heavy Ions—Immediate and Delayed Effects

The radiobiological effects of accelerated ions with high charge and high energy (HZE) on mammalian cells and their propagation in time are still not sufficiently explained and attract great deal of attention. This work aims to compare the immediate and delayed effects with emphasis on the latter. As shown by our group, the dependence of mutant fraction on expression time after irradiation may have interesting, non-monotonic, character depending on LET (linear energy transfer) of the used heavy ions. We speculate that this phenomenon may occur due to the induced genomic instability. Another area of our research is the study of the DNA structural changes in these mutants induced at different expression times. Chinese hamster V79 cells were irradiated with accelerated ions 11B, 18O, 20Ne, and gamma radiation. The LET was ranging from 0.23 keV/μm of 60Co gamma rays up to 136 keV/μm of 20Ne ions. DNA of unique HPRT mutants was isolated, concentration measured, HPRT exons amplified, and analyzed at several different time points, up to about 40 days, after exposure. Over 1200 HPRT mutants were analyzed for deletions of exons and sorted into three main categories: partial deletion, PD—with deletion of one to eight exons; total deletions, TD—with all nine exons deleted; and no deletions—no change in the HPRT structure observed. In general, the number of samples with partial deletion was increasing with LET of the used radiation, suggesting that higher energy deposition to the cell nucleus is more likely to cause larger structural changes. In the case of total deletions, increase in their number with LET was observed up to LET ∼115 keV/μm followed by a sharp decrease. The samples were also analyzed for the distribution of deletions, in particular exons at various expression times, the so-called mutational patterns. Hypothesis of the mechanisms behind observed phenomena is given, and possible implications for further research are discussed.

Спектроскопия барьерного разряда низкого давления. Послесвечение с ионами Ne-=SUP=-2+-=/SUP=-, Ne-=SUP=-+-=/SUP=- и Ne-=SUP=-2+-=/SUP=-

We present the results of modeling the radiation of a decaying plasma, formed by the processes of electron-ion recombination with the participation of three neon ions: the molecular ion Ne2+ and atomic ions Ne+ and Ne2+. Such a combination of ions, simultaneously participating in the formation of the plasma spectrum, was first discovered in the afterglow of a pulsed barrier discharge of a cylindrical geometry at neon pressures less than 1 Torr and an electron density[e] ≤ 4 × 1010 cm-3. The main attention is paid to the comparative analysis of the mechanisms of impact-radiation recombination of Ne+ and Ne2+ ions based on the numerical solution of the system of differential equations for the densities of ions and long-lived excited atoms in the afterglow, taking into account the main elementary processes in decaying plasma with pulsed "heating" of electrons. The regularities of electron temperature relaxation from discharge values of several electron volts to 300 K in the late afterglow are considered in particular details. Comparison of the model solutions with the spectral intensities measured by the multichannel photon counting method shows that, given their good agreement in the case of singly charged ions, an adequate description of the evolution of ionic lines requires expanding the available information on the recombination of Ne2+ ions.

Sputtering of Tungsten by Beryllium and Neon Ions

Sputtering yields and their angular dependences for tungsten bombarded with beryllium (Be) and neon (Ne) ions were calculated using the molecular dynamics method, showing good agreement with experiment for Ne–W collisions. Data for the Be–W interaction are necessary for calculating the impurity supply during bombardment of the diverter material (W) into plasma of the ITER tokamak. A model is proposed that explains universal behavior of the sputtering yields of tungsten in the near-threshold region during bombardment by light ions.

Double differential distributions of e-emission in ionization of N2 by 3, 4 and 5 keV electron impact

We report the measurement of the absolute double differential cross sections (DDCS) of secondary electrons emitted due to the ionization of N2 molecule in collisions with fast electrons having energies between 3 and 5 keV. The emitted electrons with energies from 1–500 eV have been measured for different forward and backward emission angles. The measured DDCS have been compared with the state-of-the-art first Born approximation with correct boundary condition (CB1) model calculations as well as with the classical trajectory Monte Carlo (CTMC) method. From the measured DDCS, the single differential cross sections (SDCS) as a function of the emission energies have been computed and eventually the total ionization cross sections (TCS) have been derived. The TCS values are also compared with a semi-empirical calculation, namely, the CSP-ic (complex scattering potential-ionization contribution) model.

Multi-gigayear White Dwarf Cooling Delays from Clustering-enhanced Gravitational Sedimentation

Abstract Cooling white dwarfs (WDs) can yield accurate ages when theoretical cooling models fully account for the physics of the dense plasma of WD interiors. We use MESA to investigate cooling models for a set of massive and ultramassive WDs (0.9–1.3 ) for which previous models have failed to match kinematic age indicators based on Gaia DR2. We find that the WDs in this population can be explained as C/O cores experiencing unexpectedly rapid 22Ne sedimentation in the strongly liquid interior just prior to crystallization. We propose that this rapid sedimentation is due to the formation of solid clusters of 22Ne in the liquid C/O background plasma. We show that these heavier solid clusters sink faster than individual 22Ne ions and enhance the sedimentation heating rate enough to dramatically slow WD cooling. MESA models including our prescription for cluster formation and sedimentation experience cooling delays of ≈4 Gyr on the WD Q branch, alleviating tension between cooling ages and kinematic ages. This same model then predicts cooling delays coinciding with crystallization of 6 Gyr or more in lower-mass WDs (0.6–0.8 ). Such delays are compatible with, and perhaps required by, observations of WD populations in the local 100 pc WD sample and the open cluster NGC 6791. These results motivate new investigations of the physics of strongly coupled C/O/Ne plasma mixtures in the strongly liquid state near crystallization and tests through comparisons with observed WD cooling.

Simulation studies of divertor power exhaust with neon seeding for CFETR with GW-level fusion power

A conventional single null divertor geometry has been proposed for Chinese fusion engineering testing reactor (CFETR) with fusion power up to gigawatt level. Modeling using the SOLPS5.0 code package shows promising results for divertor power exhaust by seeding with neon (Ne) and deuterium (D2). Partial detachment for both inner and outer divertor targets can be achieved with a peak heat load lower than 3 MW/m2. The effective ion charge number, Zeff, at the core boundary is below three, which can be further reduced by increasing the upstream D2 puffing rate. A higher D2 puffing rate helps to increase electron density (ne) in scrape-off layer (SOL) and the impurity screening ability. Based on the SOLPS modeling results, the lifetime of tungsten (W) divertor targets has been estimated by using the DIVIMP code, which indicates that W sputtering is mainly contributed by Ne ions at a far SOL region due to high electron and ion temperature (Te and Ti) there. Upstream D2 puffing can reduce the W erosion rate and W impurity concentration inside the separatrix due to decreasing Te and Ti at the far SOL region. The modeling results show a viable operation regime for the CFETR divertor.

Effects of irradiation temperature on Ne ion irradiated binary nickel-based alloys

ABSTRACT The evolution processes of the defects in Ni, Ni-Cr and Ni-Mo alloys under 400 keV Ne ion irradiation at different temperatures were investigated. At room temperature, the defect sizes are between 2 and 4 nm and defect densities are in the range of 1.24 × 1015–1.39 × 1015 m−2. With increasing irradiation temperature, the defect sizes become larger, and the defect densities decrease. Moreover, under irradiation at high temperature, Ni-Mo and Ni-Cr alloys show the higher defect densities and smaller defect sizes than Ni. These are ascribed to the pinning effects of solid solution elements on the ion irradiation-induced defects in the nickel-based alloys.

Investigation of NanoSQUIDs Fabricated with a Range of Focused Ion Beam Sources

SQUIDs (Superconducting Quantum Interference Devices) are macroscopic quantum devices capable of detecting and measuring a wide variety of physical parameters with unprecedented sensitivity. SQUIDs based on nanobridge weak links have shown increasing promise for quantum information and quantum sensing applications such as single spin detection. Focussed ion beam etched nanobridges have properties which can enhance nanoSQUID device performance but are often limited in terms of their non-hysteretic operating temperature range. Here we describe measurements of FIB-milled nanobridges, as single weak links or in nanoSQUIDs, made using either Ga, Xe or Ne ion beam sources. Their properties as a function of temperature, bias current, magnetic field and microwave power are measured and modelled according to a range of superconductivity models, as a means for improved understanding of the associated nanobridge parameters. We further propose techniques to extend the non-hysteretic operating temperature range of the devices.

Ağır İyon Terapide İnsan Organları ve Dokularının Yüklü Parçacık Etkileşimleri; Etkin Atom Numarası ve Elektron Yoğunluğu

In this work, various organs of human and tissues were studied in terms of the effective atomic numbers (Zeff) and electron densities (Ne) in the continuous kinetic energy region for different types of heavy ions. Variations of Zeff and Ne with kinetic energy were investigated and significant variations were noted. In addition, water and tissue equivalences of the given materials with respect to their Zeff and Ne were evaluated based on the results obtained. The best water equivalents were found to be Urinary Bladder_Urine for H, He and C ions and Skeleton Cartilage for Ne ion since differences in Zeff relative to water for H (≤%3), He (≤%1), C (≤%1) and Ne (≤%6) ions were significantly low. Moreover, variations in water equivalences of the materials have been discussed in detail in the continuous energy region. The reported data should be useful when heavy ions are intended to be used in these materials for radiotherapy and dosimetry applications as they represent the interaction of ions with these materials in the continuous kinetic energy region.

Mutagenic Effect of Three Ion Beams on Rice and Identification of Heritable Mutations by Whole Genome Sequencing.

High-energy ion beams are known to be an effective and unique type of physical mutagen in plants. However, no study on the mutagenic effect of argon (Ar) ion beam radiation on rice has been reported. Genome-wide studies on induced mutations are important to comprehend their characteristics for establishing knowledge-based protocols for mutation induction and breeding, which are still very limited in rice. The present study aimed to investigate the mutagenic effect of three ion beams, i.e., Ar, carbon (C) and neon (Ne) on rice and identify and characterize heritable induced mutations by the whole genome sequencing of six M4 plants. Dose-dependent damage effects were observed on M1 plants, which were developed from ion beam irradiated dry seeds of two indica (LH15, T23) and two japonica (DS551, DS48) rice lines. High frequencies of chlorophyll-deficient seedlings and male-sterile plants were observed in all M2 populations (up to ~30% on M1 plant basis); plants from the seeds of different panicles of a common M1 plant appeared to have different mutations; the whole genome-sequencing demonstrated that there were 236–453 mutations in each of the six M4 plants, including single base substitutions (SBSs) and small insertion/deletions (InDels), with the number of SBSs ~ 4–8 times greater than that of InDels; SBS and InDel mutations were distributed across different genomic regions of all 12 chromosomes, however, only a small number of mutations (0–6) were present in exonic regions that might have an impact on gene function. In summary, the present study demonstrates that Ar, C and Ne ion beam radiation are all effective for mutation induction in rice and has revealed at the genome level the characteristics of the mutations induced by the three ion beams. The findings are of importance to the efficient use of ion beam radiation for the generation and utilization of mutants in rice.

An investigation on structures and strains of gas-ion-implanted and post-implantation-annealed SiC

Silicon carbide (SiC) single crystals were implanted by 5.3-MeV Kr ion, 2.3-MeV Ne ion, and 100-keV He ion with the fluence of 2.0 × 1014, 3.75 × 1015, 3.0 × 1016 ions/cm2, respectively. After ion implantation, SiC specimens were annealed at different temperatures in a high vacuum. The HRXRD measurements were used to characterize the structure damage, strain generation and their recovery processes. HRXRD results reveal that the full width at half maximum (FWHM) of the main diffraction peak broadens and new diffraction peaks appear at lower angles besides the main diffraction peak due to lattice expansions and strain occurrences caused by the implantation. Meanwhile, with increasing annealing temperature, the lattice recovery and strain relaxation occur gradually and several stages of the strain release are presented. Moreover, based on the Arrhenius model, the thermal relaxation activated energy of strains at different temperature ranges was estimated. The mechanisms on strain releases were discussed in detail.

An irradiation device for biological targets using focused microbeams of cyclotron-accelerated heavy ion

For use in medical and life science research, a device and sample preparation methods were developed to irradiate cultured cells and individual animals with a focused microbeam of cyclotron-accelerated heavy-ions. The new irradiation device positions both sample and microscope with micrometer precision. The beam size is smaller than 3 µm when the distance between the beam exit from vacuum to the irradiation device is less than 500 µm for 13.0 MeV/u 20Ne ions. This beam size is sufficiently small to irradiate intracellular targets in cultured cells. A beam size smaller than 10 µm was obtained for 12C ions of 26.7 MeV/u at a distance of 2 mm from the beam exit, which enabled irradiation of specific cells in a small model animal. Methods to prepare cultured cells and the nematode Caenorhabditis elegans for irradiation using the new device are reported, and the results of the first irradiation experiments presented.

Annealing behavior of hardening and ductility loss of a 16Cr–4Al ODS ferritic steel irradiated with high energy Ne ions

Annealing behavior of the hardening and ductility loss of an oxide-dispersion-strengthened (ODS) ferritic steel (16Cr–4Al) irradiated with high-energy heavy ions is studied. 20Ne ions with 123.4 MeV supplied by a cyclotron was used to produce a quasi-uniform atomic region of atomic displacement damage and Ne concentration from surface to a depth of 33 μm in the specimens. Two atomic displacement levels (0.16dpa, 0.70dpa) were approached at about 220 K. The irradiated specimens were subsequently thermally annealed at room temperature, 473 K and 673 K, respectively. Hardness and ductility of the specimens were investigated with nano-indentation technique and small-punch test. The data of the nano hardness were fitted by Nix-Gao model to obtain the bulk equivalent hardness values. The irradiated specimens show observable hardening, which recedes monotonously with the increase of annealing temperature. The Arrhenius plots show a good linearity in the entire temperature range investigated, with an apparent activation energy of 0.13 ± 0.01 eV for both the two damage levels. Assuming that the hardening is caused by the self-interstitial-atom (SIA) clusters initially produced by the cascade damage, an activation energy of 0.70 ± 0.05 eV is deduced for the migration and coalescence process of the SIA-clusters. The small punch test (SPT) of the high-dose specimens shows that a minor ductility loss occurred under conditions as-irradiated or subsequently thermally annealed at 473 K, while a remarkable increase of the ductility loss was observed after the thermal annealing at 673 K, which coincides with the formation of nano-scale gas bubbles in high density in the specimen. It is indicated that the formation of bubbles has minor on the irradiation hardening. A comparison of three ODS ferritic steels Ne-ion-irradiated to 0.7 dpa/260 appm(Ne) shows that the ductility loss decreases with the increase of the sink strength of the oxide dispersoids/ferritic substrate interfaces.

Experimental investigation of dissociative ionization of NeAr dimer by electron impact

SynopsisA two body fragmentation experiment of NeAr dimer by 480 eV electron impact was performed. By recon-structing the momenta of Ne+ ion, Ar+ ion and one electron, the 2D coincidence map between Kinetic energy release and electron energy is obtained, from which two islands are observed. It is found that, Interatomic Coulombic Decays induced by Ne+Ar ion and Ar+ Ne ion can both take place in our experiment, as well as Radiative Charge Transfer. This is different from X ray in which only one decay process is dominant in one incident energy.