Helium Ions Research Articles

Particle induced x-ray emission (pixe) assisted technique in the evaluation of potential ecological risks of heavy metals in surface sediments of Oba-Ile River, Ifelodun Local Government Area, Osun-State, Nigeria

The seasonal evaluation of trace elements in the surface sediments collected from Oba-Ile River, using Particle Induced X-Ray Emission (PIXE) Spectroscopy had been carried out. This was done so as to provide information about the pollution status of the river during the rainy and dry seasons. The samples were subjected to trace metal profiling using a 2.5 Mev proton available at the Ion Beam Analysis (IBA)/accelerator laboratory, Centre for Energy Research and Development (CERD), Obafemi Awolowo University, Ile-Ife. The facility is centered on a NEC 5SDH 1.7 MV Pelletron accelerator, equipped to provide proton and helium ions. A multi-elemental estuarine sediments referenced material (SRM 1646a purchased from NIST) was used for the determination of H-value which was subsequently used for analyzing the samples and assured the accuracy of the experimental procedure. The order of abundance of the 16 elements identified was Si > Fe >Al >K > Ca >Ti > Na > Mg > Zr > Mn > Sr > V > Cr > Zn > Pb > Cu. The contamination factor indicated that the metals presented a low contamination factor (LCf) to moderate contamination factor (MCf) except for Fe and Zr which presented a considerable contamination (CCf) and a very high contamination factor (VHCf) respectively. Other contamination indices indicated that Fe had either a moderate enrichment (ME) factor or a significant enrichment (SE) factor, thereby suggesting that Oba-Ile River sediment was particularly enriched in Fe

The alpha particle charge radius, the radion and the proton radius puzzle

AbstractRecent measurements of the Lamb shift of muonic helium-4 ions were used to infer the alpha particle charge radius. The value found is compatible with the radius extracted from the analysis of the electron-helium scattering. Thus, the new spectroscopic data put additional empirical bounds on some free parameters of certain physics theories beyond the Standard Model. In this paper, we analyze the new data in the context of large extra-dimensional theories. Specifically, we calculate the influence of the radion, the scalar degree of freedom of the higher-dimensional gravity, on the energy difference between the 2S and 2P levels of this exotic atom. The radion field is related to fluctuations of the volume of the supplementary space. It should be treated as a phenomenologically independent quantity in relation to the tensorial degrees of freedom of the metric within the braneworld scenario. Based on the spectroscopic data of muonic helium, we find constraints for the effective energy scale of the radion as a function of the alpha particle radius. Then, we discuss the implications of these new constraints on the proton radius puzzle. We also establish a new empirical bound for the radion by examining its influence on the isotopic shift in the 2P-2S transition of muonic hydrogen and muonic deuteron. In connection with this discussion, we study the impact of the radion on the tension observed in measurements of the difference between the squared radii of the helion and alpha particle as extracted from muonic and electronic helium isotopes.

Manifestations in nature of self-controlled quasi-stationary nuclear fusion into magnetized low-temperature hydrogen plasma

This paper examines the characteristics of nuclear reactions occurring in low-temperature magnetized deuterium plasma. It is demonstrated that considering the ionization-recombination dynamics of deuterium atoms in this plasma allows for the potential realization of efficient nuclear fusion at low thermal energies kT≈10−20 eV. The study shows that these processes are linked to the formation of coherent correlated states of deuterons, accompanied by the generation of giant energy fluctuations δE≥10−50 keV during each recurring ionization event of deuterium atoms. These findings align with known anomalies in the solar atmosphere, such as the sharp temperature increase above the Sun’s surface and the observed excess concentration of helium-3 ions in the solar wind. Furthermore, this process may explain well-documented experimental results, such as neutron generation during electric discharges in gas.

Minimal lateral damage fabrication of high-temperature superconducting nanowires via focused helium ion beam irradiation

Abstract Low-temperature superconducting nanowire single-photon detectors have become a key infrared photon counting technology in communication and astronomy applications. However, the constrained physical space of devices demands high-performance superconducting detectors capable of operation at higher temperatures. To date, high-temperature superconductor nanowires still face seriously uneven lateral damage in the ion etching process during fabrication. In this work, we report a promising fabrication method for high-temperature superconducting YBa2Cu3O7−x (YBCO) nanowires, using a focused helium ion beam to minimize the lateral damage of the cut. Based on simulations, we designed tangent circles and adjacent isosceles triangles to replace lines in cutting nanowires to reduce the superimposed damage by He+ ions. The lateral damage of a single helium ion cut has been reduced with a decrease in superimposed damage width from 58.8 nm to 29.7 nm. This work provides a platform for boosting YBCO nanowires to achieve single photon detection.

Circular dichroism in multiphoton ionization of resonantly excited helium ions near channel closing

The circular dichroism (CD) of photoelectrons generated by near-infrared (NIR) laser pulses using multiphoton ionization of excited He+ ions in the 3p(m= +1) state is investigated. The ions were prepared by circularly polarized extreme ultraviolet (XUV) pulses. For circularly polarized NIR pulses co- and counter-rotating relative to the polarization of the XUV pulse, a complex variation of the CD is observed as a result of intensity- and polarization-dependent Freeman resonances, with and without additional dichroic AC-Stark shifts. The experimental results are compared with numerical solutions of the time-dependent Schrödinger equation to identify and interpret the pronounced variation of the experimentally observed CD.

Detection of bifurcation in phase-space perturbative structures across transient wave–particle interaction in laboratory plasmas

A key ingredient for realizing a magnetically confined tritium-deuterium plasma fusion reactor is plasma heating by fusion-born high-energy helium ions, as a chained cycle of "nuclear burning." Efficient collisionless plasma heating by high-energy particles is anticipated when their energy is directly transferred to the plasma through waves. Those processes often involve nonlinear structure formations in phase-space, spanned by real-space and velocity-space coordinates, that significantly influence heating efficiency. To date, experimental knowledge of phase-space structure formation physics is severely limited, due to lack of experimental diagnostic schemes. Here, state-of-the-art hardware and software approaches for phase-space perturbative structure detection are introduced. A bifurcation in the phase-space structure formation is found, which affects the plasma heating efficiency. A confinement magnetic field structure is shown to be a potential knob for nuclear-burning control through phase-space manipulation.

Oxygen consumption measurements at ultra-high dose rate over a wide LET range.

The role of radiolytic oxygen consumption for the in-vitro "Ultra-High Dose Rate" (UHDR) sparing and in-vivo FLASH effect is subject to active debate, but data on key dependencies such as the radiation quality are lacking. The influence of "dose-averaged Linear Energy Transfer" (LETd) and dose rate on radiolytic oxygen consumption was investigated by monitoring the oxygen concentration during irradiation with electrons, protons, helium, carbon, and oxygen ions at UHDR and "Standard Dose Rates" (SDR). Sealed "Bovine Serum Albumin" (BSA) 5% samples were exposed to 15Gy of electrons and protons, and for the first time helium, carbon, and oxygen ions with LETd values of 1, 5.4, 14.4, 65, and 100.3keV/µm, respectively, delivered at mean dose rates of either 0.3-0.4Gy/s for SDR or approximately 100Gy/s for UHDR. The Oxylite (Oxford Optronics) system allowed measurements of the oxygen concentration before and after irradiation to calculate the oxygen consumption rate. The oxygen consumption rate was found to decrease with increasing LETd from 0.351mmHg/Gy for low LET electrons to 0.1796mmHg/Gy for high LET oxygen ions at SDR and for UHDR from 0.317 to 0.1556mmHg/Gy, respectively. A higher consumption rate for SDR irradiation compared to the corresponding UHDR irradiation persisted for all particle types. The measured consumption rates demonstrate a distinct LETd dependence. The obtained dataset, encompassing a wide range of LETd values, could serve as a benchmark for Monte Carlo simulations, which may aid in enhancing our comprehension of oxygen-related mechanisms after irradiations. Ultimately, they could help assess the viability of different hypotheses regarding UHDR sparing mechanisms and the FLASH effect. The found LETd dependence underscores the potential of heavy ion therapy, wherein elevated consumption rates in adjacent normal tissue offer protective benefits, while leaving tumor regions with generally higher "Linear Energy Transfer" (LET) vulnerable.

Radiation Resistivity of Ti-5331 Alloy with Different Microstructures

Titanium alloys have promising potential for applications in marine nuclear power systems owing to their exceptional mechanical and corrosion properties. Nevertheless, their radiation resistivity is a determining factor for their extensive use as structural materials in nuclear energy systems. In this study, the radiation resistivity of Ti-5Al-3V-3Zr-Cr (Ti-5331) alloys with three different microstructures was examined using a combination of characterization techniques including positron annihilation Doppler broadening spectroscopy (DBS), Elastic Recoil Detection Analysis (ERDA), Transmission Electron Microscope (TEM), Small-Angle X-ray scattering (SAXS) and nanoindentation. The results reveal that the equiaxed structure, bimodal structure, and Widmanstatten structure of Ti-5331 alloy obtained through different annealing processes exhibit differences in the number of interfaces and the content of the β phase. The α/β interfaces can significantly enhance the radiation resistance of titanium alloys by inhibiting the diffusion of helium atoms after helium ion irradiation. Notably, the alloy with a bimodal structure exhibited the best overall radiation resistivity, showing small defect size, low hardening effect, and low swelling rate of 0.003%. Moreover, the size of helium bubbles of the bimodal structure is half of that in the equiaxed structure and Widmanstatten structure. Thus, the bimodal structure of the Ti-5331 alloy possesses superior radiation resistivity.

Breakthrough 4π helium ion energy spatial distribution in plasma focus space applying novel mega-size panorama cylindrical ion image detector

Breakthrough 4π helium ion energy spatial distribution in plasma focus space applying novel mega-size panorama cylindrical ion image detector

Overall Concept Design of 2.45 GHz ECR Ion Source with Tunable Magnetic Field

The design of the ECR ion source was made for an operating frequency of 2.45 GHz. The ion source is considered to be used for producing protons and double charged helium ions. The source construction as well as the separate components design are presented in the study. The operating modes include both ECR and microwave operating regimes. The extraction system with the beamforming was developed. The beam adjustment is implemented by the longitudinal shifting of the electrodes against the plasma electrode position. The performance of the 2.45 GHz waveguide line to provide the stable power injection into the plasma chamber is considered. The numerical simulation of the waveguide line components was made and optimised.

On Velocity Stopbands in Electrostatic Solitary Wave Propagation in Magnetospheric Plasma in the Presence of an Ion Beam—Application in the Solar Wind

Satellite observations in the Earth’s magnetosphere suggest a coexistence of different types of ion populations, such as protons and heavier helium ions (alpha particles) transported by the solar wind. We have undertaken an investigation, from first principles, of the conditions for the occurrence of electrostatic solitary waves in such a multi-ion plasma environment. Nonlinear analysis has been employed to explore the effect of an ion beam on the occurrence of stopbands in a multicomponent plasma consisting of Boltzmann electrons and two ion species, modeled as cold and warm (adiabatic) ions. A “stopband” is an interval of pulse speed (mach (Mach number) values in which solitary waves cannot propagate. Such stopbands are known to exist in relation to fast ion-acoustic solitary waves (exclusively). Our parametric analysis reveals that the stopband widens over the range of cold ion charge density (values) upon increasing speed of a hot ion beam moving along the direction of wave propagation. However, the stopband becomes narrower in the case of a counterpropagating beam. Similarly, the streaming of a cold ion beam fluid along (or antiparallel) to the wave direction leads to the narrowing (or widening, respectively) of the stopband. The fast soliton existence (velocity) domain is characterized by two critical points (a crossover and a turning point), which are affected by the beam. Our study could be relevant to understanding energy dissipation processes in the fast solar wind associated with relative drifts between the major (protons) and minor (alpha particles) ions which results in the heating of both species.

Nanofabrication of high transition temperature superconductive electronics with focused helium ion irradiation

Superconductive electronics from Josephson junctions are governed by quantum mechanical tunneling through sub-10 nm scale insulating tunnel barriers. The electrical properties are exponentially sensitive to this dimension, which necessitates fabrication with nanoscale precision and uniformity. For circuits in high-transition temperature YBa2Cu3O7−δ (YBCO) thin films, direct writing of the material with a focused helium ion beam has shown promise in the creation of uniform nanoscale insulators for YBCO Josephson junctions and other circuit regions. In this paper, we report on the procedures and variables associated with this process and discuss the potential for scaling up the number of junctions for quantum sensing and complex energy efficient digital circuits.

Isolation and characterization of bacteriophages specific to Streptococcus equi subspecies zooepidemicus and evaluation of efficacy ex vivo.

Streptococcus (S.) equi subspecies (subsp.) zooepidemicus is an important facultative pathogen in horses and can cause severe infections in other species including humans. Facing the post-antibiotic era, novel antimicrobials are needed for fighting bacterial infections. Bacteriophages (phages) are the natural predators of bacteria and discussed as a promising antimicrobial treatment option. The objective of this study was to isolate and characterize S. equi subsp. zooepidemicus-specific phages for the first time and to evaluate their efficacy in vitro and ex vivo. In total, 13 phages with lytic activity were isolated and host ranges were determined. Two phages with broad host ranges and high efficiency of plating (vB_SeqZP_LmqsRe26-2 (lytic activity: 30/37 bacterial isolates) and vB_SeqZP_LmqsRe26-3 (lytic activity: 29/37 bacterial isolates)) and one phage with relatively low efficiency of plating (vB_SeqZP_LmqsRe26-1) were selected for further characterization, including electron microscopy and whole genome sequencing. In in vitro planktonic killing assays at two tested multiplicities of infection (MOI 1 and MOI 10), significant bacterial growth reduction was observed when the phages vB_SeqZP_LmqsRe26-2 and vB_SeqZP_LmqsRe26-3 were added. These phages were subsequently co-incubated with clinical S. equi subsp. zooepidemicus isolates in an equine endometrial explant model but did not achieve bacterial growth reduction at MOI 1 and MOI 10. However, helium ion microscopy revealed presence of particles adherent to the bacteria on the explant after incubation (25 h), suggesting possible phage-bacteria interactions. In conclusion, phages against S. equi subsp. zooepidemicus were successfully isolated and characterized. Promising results were observed in in vitro but no significant reduction was detected in ex vivo experiments, requiring additional investigations. However, after further adaptations (e.g., optimization of MOIs and phage administration or use of phage-antibiotic combination), phages could be a potential antimicrobial tool for future therapeutic use in S. equi subsp. zooepidemicus infections, although the available results do not currently support the therapeutic usage.

ELECTROPHYSICAL CHARACTERISTICS OF TiO2 SAMPLES IRRADIATED WITH 0.12 MeV HELIUM IONS

The main parameters of samples irradiation on the linear helium ions accelerator are presented as well as of TiO2 irradiated characteristics. It is experimentally shown that with irradiation dose increasing, helium ion energy of 0.12 MeV, the volume electrical resistance and surface electrical resistances on the front and back sides of samples decrease, the loss angle tangents and relative dielectric permittivities increase. The primary processes, namely: the sputtering, ionization, phonons and vacancies formation, segregation, damage have been calculated. The analysis of experimental and calculated data has shown that a model based on processes of the excitation and propagation of elastic waves in a concept of the long-range effect most physically correctly describes the changes in electrophysical characteristics of the irradiated samples.

Photoluminescence Spectra of Helium Ion-Implanted Diamond.

Ion implantation in diamond crystals is widely used both for producing conducting microstructures in the bulk of the material and for creating isolated photon emitters in quantum optics, photonics, cryptography, and biosensorics. The photoluminescence (PL) spectra of helium ion-implanted diamonds are dominated by two sharp emission lines, HR1 and HR2 (from Helium-Related), at ~536 and 560 nm. Here, we report on PL studies of helium-related optical centers in diamonds. Experiments have been carried out on a (110) plate of natural single-crystal type IIa diamonds. The uniform distribution of radiation defects in a 700 nm-thick layer was obtained by ten cycles of multiple-energy (from 24 to 350 kV) helium ion implantation with a total dose of 5 × 1016 cm-2. The diamonds were annealed in steps in a vacuum oven at temperatures from 200 to 1040 °C. It is demonstrated that helium ion implantation in diamonds followed by annealing gives rise to more than a dozen various centers that are observed in the PL spectra in the range of 530-630 nm. The transformations of the PL spectra due to annealing are investigated in detail. The spectral shapes of phonon sidebands are determined for the HR1, HR2, and HR3 bands with ZPLs at ~536, 560, and 577 nm, respectively, and it is shown that these bands are attributed to interstitial-related centers in diamonds. The reported results are important for understanding the structure and properties of helium-related defects in diamonds.

Single-photon and multi-photon Fano lines for helium and neon using tRecX-haCC

Abstract Single-photon and multi-photon ionization of helium and neon atoms by ultrashort extreme ultraviolet radiation is studied. The wavelength of radiation is chosen to excite a set of doubly excited states. We analyse the lineshapes arising from the presence of doubly excited states and numerically demonstrate the sensitivity of the Fano q parameter to the order of multi-photon process. The computations were performed using the tRecX-haCC package developed by the authors. The tRecX-haCC package solves the time-dependent Schrödinger equation in the presence of a laser pulse and computes the photoelectron spectra including the narrow resonance peaks using the time-dependent surface flux method (tSurff) and iSurf techniques.

Excitation cross-sections for atomic hydrogen by hydrogen-like ions of helium and carbon

Excitation cross-sections for atomic hydrogen by hydrogen-like ions of helium and carbon

Effect of irradiation temperature on the mobility of structural and vacancy defects in the damaged layer of Li2ZrO3 ceramics

The paper presents the assessment results of the irradiation temperature effect on the change in the type of structural defects caused by irradiation with helium ions in the near-surface layer of Li2ZrO3 ceramics, as well as determining the nature of structural damage using the electron paramagnetic resonance method in the case of irradiation fluence variation. During characterization of the structural changes caused by helium ion irradiation, the main attention was paid to detailing the type of structural defects and radiolysis products arising during irradiation, alongside alterations in their concentration using the electron paramagnetic resonance method. During the experiments, it was determined that the observed effects of thermally stimulated mobility of vacancy defects in the damaged layer caused by irradiation with helium ions indicate a positive effect of thermal heating of samples during irradiation at low fluences. This effect consists in a decline in the number of oxygen vacancies in the damaged layer at low irradiation fluences (1015–1016 cm−2), the concentration of which was determined using the EPR method, and the observed structural changes at low irradiation fluences in the case of an elevation in irradiation temperatures are associated with deformation distortion of the crystalline structure of ceramics caused by transformation energy processes, and thermal expansion effects.

Influence of temperature gradients on helium diffusion and clustering in tungsten: A molecular dynamics study

Tungsten and its alloys, used as plasma-facing materials in fusion reactors, endure high-flux, low-energy helium ion irradiation and temperature gradients induced by thermal load and shocks. This study utilizes molecular dynamics (MD) simulations to explore the diffusion and clustering behavior of helium (He) in tungsten (W) under temperature gradients. The migration behavior of isolated helium atoms, small helium clusters, and helium self-interstitial atom (He-SIA) clusters within tungsten is analyzed. It is revealed that both helium and He-SIA clusters tend to migrate towards higher temperature regions, exhibiting negative thermophoresis. The nucleation of helium clusters, the formation of Frenkel pairs, and the interactions between self-interstitial clusters and helium clusters are also investigated. The results indicate that helium concentration significantly impacts He nucleation behavior. Directional diffusion may lead to areas of high concentration over time, potentially promoting the formation of He clusters and bubbles. These insights enhance the understanding of tungsten's performance and durability as a plasma-facing component in fusion reactors.

Surface plasmons on silver gratings transform pyrolytic carbon into luminescent graphitized carbon dots.

Plasmonic catalysis holds the promise of opening new reaction pathways that are inaccessible thermally or via direct UV-vis electronic transitions. Here, energetic carriers produced via the decay of surface plasmons excited by visible light at 532nm (2.33eV, green) on a Ag-grating-bearing pyrolytic carbon residue drive its transformation into light-emitting graphitized carbon dots. The pyrolytic carbon residue is detectable via high-magnification surface-enhanced Raman scattering but cannot be directly observed using optical, electron, atomic force, or helium ion microscopy. When a Ag-grating-bearing pyrolyzed residue is introduced into a high-purity O2-depleted gas environment (Ar, N2, and CO2) and excited with 532nm light, bright yellow luminescence emerges and is readily observed. Light emission is not observed without the pyrolytic carbon, without the excitation of plasmons, or in air or an Ar/O2 gas mixture. This process, driven by visible light and a nanostructured Ag surface bearing pyrolytic carbon, will be of interest to researchers involved in plasmonic catalysis, catalytic processes involving carbon, and luminescent plasmonic surfaces.