Ion Energy Deposition Research Articles

Numerical simulation study on the mechanism of plasma dissociation of carbon dioxide in atmospheric pressure packed-bed reactors

The streamer propagation and electric field distribution in a two-dimensional fluid model of a packed bed reactor (PBR) filled with carbon dioxide are comprehensively studied by utilizing the PASSKEy simulation platform in this work. The spatiotemporal evolution of electron density, electric fields and key plasma species in the discharge process are studied in depth. The PBR with layered dielectric spheres is simulated by using the model, indicating that the inner sides of the first layer and the second layer of dielectric spheres are not the main regions for reactions such as CO<sub>2</sub> dissociation; instead, the main regions are along the streamer propagation path and the outer side of the first layer of dielectric sphere. In this work, the propagation of streamers in an electric field is investigated, highlighting the influence of anode voltage rise and dielectric polarization on local electric field enhancement. This enhancement leads the electron density and temperature to increase, which facilitats streamer propagation and the formation of filamentary microdischarges and surface ionization waves. This work provides a detailed analysis of the local electric field evolution at specific points within the PBR, and a further investigation of the spatiotemporal dynamics of spatial and surface charges, revealing that negative charges concentrate in the streamer and on the dielectric surface, with density being significantly higher than that of positive charges. The positive charge distribution is closely related to the streamer path, and with time going by, the charge distribution becomes dominated in the discharge space. This work also explores the surface charge deposition on the dielectric spheres, and discusses the evolution trend of the distribution. Additionally, this work discusses the temporal and spatial evolution of key plasma species, including ions and radicals, and their contributions to the overall discharge characteristics. The production mechanisms of carbon monoxide particles, carbon dioxide ions, and oxygen ions are analyzed, with a focus on their spatial distribution and correlation with electron density. Finally, the energy deposition within the PBR is examined by integrating the spatial energy deposition of electrons and major positive ions. The results indicate a total energy deposition value of approximately 1.428 mJ/m, with carbon dioxide ions accounting for 8.8% of this value.

Three-in-One Nanozyme for Radiosensitization of Bladder Cancer.

Bladder cancer is a common malignancy of the urinary system and the development of noninvasive therapeutic methods is imperative to avoid radical cystectomy, which results in a poor quality of life for patients. In this study, ultrasmall copper-palladium nanozymes decorated with cysteamine (CPC) nanoparticles (NPs) were synthesized to enhance the efficacy of radiotherapy (RT) in treating bladder cancer. CPC NPs react with intracellular overexpressed H2O2 in the tumor microenvironment to produce large quantities of reactive oxygen species (ROS) and induce tumor cell apoptosis. Furthermore, the CPC nanozymes can generate ample oxygen within tumors by utilizing H2O2, addressing hypoxia conditions, and mitigating radioresistance. Additionally, CPC facilitates the oxidation of glutathione (GSH) into oxidized glutathione disulfide (GSSG), blocking the self-repair mechanisms of tumor cells post-treatment. Simultaneously, CPC enhances the ionization energy deposition effect on tumor cells. The results demonstrate an increased level of ROS and an elevation in oxygen content at the tumor site. Importantly, tumor growth was restrained without apparent systemic toxicity during the combined treatment. In summary, this study highlights the potential of CPC nanozyme-mediated radiotherapy as a promising avenue for the effective treatment of bladder cancer and demonstrates its potential for future clinical applications in the synergistic therapy of bladder cancer.

Towards precise LET measurements based on energy deposition of therapeutic ions in Timepix3 detectors

Objective. There is an increasing interest in calculating and measuring linear energy transfer (LET) spectra in particle therapy in order to assess their impact in biological terms. As such, the accuracy of the particle fluence energy spectra becomes paramount. This study focuses on quantifying energy depositions of distinct proton, helium, carbon, and oxygen ion beams using a silicon pixel detector developed at CERN to determine LET spectra in silicon. Approach. While detection systems have been investigated in this pursuit, the scarcity of detectors capable of providing per-ion data with high spatial and temporal resolution remains an issue. This gap is where silicon pixel detector technology steps in, enabling online tracking of single-ion energy deposition. The used detector consisted of a 300 µm thick silicon sensor operated in partial depletion. Main results. During post-processing, artifacts in the acquired signals were identified and methods for their corrections were developed. Subsequently, a correlation between measured and Monte Carlo-based simulated energy deposition distributions was performed, relying on a two-step recalibration approach based on linear and saturating exponential models. Despite the observed saturation effects, deviations were confined below 7% across the entire investigated range of track-averaged LET values in silicon from 0.77 keV µm−1 to 93.16 keV µm−1. Significance. Simulated and measured mean energy depositions were found to be aligned within 7%, after applying artifact corrections. This extends the range of accessible LET spectra in silicon to clinically relevant values and validates the accuracy and reliability of the measurements. These findings pave the way towards LET-based dosimetry through an approach to translate these measurements to LET spectra in water. This will be addressed in a future study, extending functionality of treatment planning systems into clinical routine, with the potential of providing ion-beam therapy of utmost precision to cancer patients.

Monolithic HV-CMOS sensors for a beam monitoring system of therapeutic ion beams

Nowadays, cancer treatment with ion beam is well established and studied. This method allows to deposit the maximum dose to the tumor and minimize the damage to healthy tissue, due to the Bragg peak of the ion energy deposition near the end of the particle range. During the treatment, it is possible to provide volumetric dose delivery by changing the particle energy (penetration depth) and adjusting the beam position via a magnetic system. For the beam monitoring system, the precise measurement of the beam direction, shape and fluence in real time becomes crucial to provide effective and safe dose delivery to the tumor. Additionally, the system should work for beam intensities up to 1010 s-1 for protons, be tolerant to 1 MeV neutron equivalent fluences up to 1015 cm-2 per year and be to tolerant to magnetic fields (for MR-guided ion beam).The studies presented in this article are focused on the application of the HitPix sensor family with counting electronics and frame-based readout for such a beam monitoring system. The HitPix sensors are monolithic pixelated silicon sensors based on HV-CMOS technology and have been developed at the ASIC and Detector Lab (ADL, KIT). Recent measurements with ion beams and a multi-sensor readout as well as future developments are discussed.

Assessing trajectory-dependent electronic energy loss of keV ions by a binary collision approximation code

The inelastic energy deposition of energetic ions is a decisive quantity for numerous industrial-scale applications, such as sputtering and ion implantation, yet the underlying physics being governed by dynamic many-particle processes is commonly only qualitatively understood. Recently, transmission experiments on single-crystalline targets (Phys. Rev. Lett. 124, 096601 & Phys. Rev. A 102, 062803) revealed a complex energy scaling of the inelastic energy loss of low-energy ions heavier than protons along different trajectories. We use a Monte Carlo like binary collision approximation code equipped with an impact-parameter-dependent modeling of the inelastic energy losses to assess the role of local contributions to electronic excitations in these cases. We compare angular intensity distributions of calculated trajectories with experimental results for 50-keV 4He and 100-keV 29Si ions transmitted in a time-of-flight setup through single-crystalline silicon (001) foils with nominal thicknesses of 200 and 50 nm, respectively. In these calculations, we employ different models of electronic energy loss, i.e., local and nonlocal forms for light and heavy projectiles. We find that the vast number of projectiles are eventually channeled along their trajectories, regardless of the alignment of the crystal with respect to the incident beam. It is, however, only when local electronic energy loss is considered that the simulated two-dimensional maps and energy distributions show excellent agreement with the experimental results, where channeling leads to significantly reduced stopping, especially for heavier projectiles. We demonstrate the relevance of these effects for ion implantations by assessing the nonlinear and nonmonotonic scaling of the ion range with the thickness of a random surface layer. Published by the American Physical Society 2024

Numerical Simulation Study on the Mechanism of Plasma Dissociation of Carbon Dioxide in Atmospheric Pressure Packed-Bed Reactors

This article presents a comprehensive study on the streamer propagation and electric field distribution within a two-dimensional fluid model of a packed bed reactor (PBR) filled with carbon dioxide, utilizing the PASSKEy simulation platform. The research delves into the spatiotemporal evolution of electron density, electric fields and key plasma species in the discharge process. The model simulates a PBR with layered dielectric spheres, indicates that the inner sides of the first and second layers of dielectric spheres are not the primary regions for reactions such as CO<sub>2</sub> dissociation; instead, the main regions are along the streamer propagation path and the outer side of the first layer of dielectric spheres. The study by examining the propagation of streamers in the presence of an electric field, highlighting the influence of anode voltage rise and dielectric polarization on local electric field enhancement. This enhancement leads to increased electron density and temperature, facilitating streamer propagation and the formation of filamentary microdischarges and surface ionization waves. The article provides a detailed analysis of the local electric field evolution at specific points within the PBR. The research further investigates the spatiotemporal dynamics of spatial and surface charges, revealing that negative charges concentrate within the streamer and on the dielectric surface, with densities significantly higher than positive charges. The positive charges' distribution is closely related to the streamer's path, and over time, they come to dominate the charge distribution in the discharge space. The study also explores the surface charge deposition on the dielectric spheres, discusses the evolution trends of the distribution. Additionally, the article discusses the temporal and spatial evolution of key plasma species, including ions and radicals, and their contribution to the overall discharge characteristics. The production mechanisms of carbon monoxide particles, carbon dioxide ions, and oxygen ions are analyzed, with a focus on their spatial distribution and correlation with electron density. The study concludes with an examination of the energy deposition within the PBR, integrating the spatial energy deposition of electrons and major positive ions. The results indicate a total energy deposition value of approximately 1.428 mJ/m, with carbon dioxide ions accounting for 8.8% of this value.

Heavy Ion Energy Deposition and SEE Intercomparison Within the RADNEXT Irradiation Facility Network

RADNEXT is an EU-funded network of irradiation facilities and radiation effects experts aimed at increasing the quantity and quality of user access to accelerator infrastructure, and improving the diversity and harmonization across facilities. Along with the beam provision to worldwide radiation effects users, RADNEXT has an ambitious research program oriented at improving radiation effects testing, of which an example of a heavy ion facility inter-comparison at very different energy regimes is included in this work. In particular, energy deposition distributions in a silicon solid-state detector and the Single Event Upset (SEU) and Multiple Cell Upset (MCU) behaviour are compared amongst heavy ion beams of similar LET, but very different energies (i.e., from the more classical ~10 MeV/u regime up to several hundreds of MeV/u).

BGO quenching effect on spectral measurements of cosmic-ray nuclei in DAMPE experiment

The Dark Matter Particle Explorer (DAMPE) is a satellite-borne detector designed to measure high energy cosmic-rays and γ-rays. As a key sub-detector of DAMPE, the Bismuth Germanium Oxide (BGO) imaging calorimeter is utilized to measure the particle energy with a high resolution. The nonlinear fluorescence response of BGO for large ionization energy deposition, known as the quenching effect, results in an under-estimate of the energy measurement for cosmic-ray nuclei. In this paper, various models are employed to characterize the BGO quenching factors obtained from the experimental data of DAMPE. Applying the proper quenching model in the detector simulation process, we investigate the tuned energy responses for various nuclei and compare the results based on two different simulation softwares, i.e. GEANT4 and FLUKA. The BGO quenching effect results in a decrease of the measured energy by approximately 2.5% (5.7%) for carbon (iron) at ∼10 GeV/n and <1% above 1 TeV/n, respectively. Accordingly, the correction of the BGO quenching effect leads to an increase of the low-energy flux measurement of cosmic-ray nuclei.

Fabrication of triangular pits in barium fluoride single crystals by localized electronic excitations

Ion beam technology is considered as one of the most effective and unique techniques for materials engineering. Here, we show that the selective chemical etching is used successfully for the fabrication of pyramidal etch pits by revealing the ion-induced damage in the surface and below surface regions of barium fluoride single crystals. The size of ion-induced pits is increasing by etching the ion impacted zones for longer time. Moreover, the types of the induced defects are probed using optical absorption spectroscopy. The presented findings are discussed in terms of the peculiarities of ion energy deposition as well as the comparison with the induced structures using different type of ions, namely slow highly charged ions. Furthermore, they might be of importance in today’s nano and microelectronics applications, where the fabrication of size-controlled surface structures is of high necessity.

Terrestrial neutron induced failure rate measurement of SiC MOSFETs using China spallation neutron source

The atmospheric neutron induced single event burnout (SEB) is observed for SiC MOSFETs by conducting irradiation at China Spallation Neutron Source (CSNS) with maximum energy close to 1.6 GeV. The failure is manifested as a sudden loss of voltage blocking ability during irradiation and a melting region is observed for the device with SEB. The SEB failure rates of SiC MOSFETs are calculated based on the experimental results. It shows that the failure rates increase exponentially with operating voltages. The measured failure rates are consistent with the results obtained at the other spallation neutron sources, which proves that the neutron beam line at CSNS is suitable for SEB testing. The information of the secondary ions produced by neutron is obtained through Monte Carlo simulations and the contributors to SEB are analyzed. A simulation method is also applied to calculate SEB failure rate by considering ionization energy deposition of secondary ions in the sensitive region of SiC devices. The simulated failure rates are also consistent with the experimental results.

3D Potential Simulation for H2+ ion Under a Strong Laser Field

Potential is the most important quantity needed to be concerned in the study of interaction between projectile ion and target. On the one hand, it decides the total interaction course such as ion energy deposition and molecular Coulomb explosion and so on. On the other hand, under a strong laser field, the potential can be influenced by the laser. In this paper, the 3D potential is studied under a strong laser field for a hydrogen molecular ion in Al target. The simulation results show that the 3D potential is weakened by the laser intensity. Such results can provide references for correlated experiments and theoretical study.

Charge Evolution for N2 + Ion Passing Through Ag Target

Charge state is a key factor for the ion stopping and energy deposition. It is helpful to understand the physics mechanics for interaction between ion and target by studying the charge state. In this paper, nitrogen molecular ion charge evolution in Ag target is studied. It is shown that the charge state of the trailing ion is oscillating, while the leading ion doesn’t show the similar behavior due to the wake effects aroused by the electronic exciting of the target electron.

Trajectory dependence of electronic energy-loss straggling at keV ion energies

Accurate knowledge of ion energy deposition in materials is imperative for a wealth of scientific and technological applications. Here, the authors measure the energy-loss straggling, i.e., the energy distribution variance of transmitted ions, for $k\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}V$ ions of H, He, B, and Si in Si membranes. Straggling exhibits a significant trajectory dependence for all ions. Studying the velocity dependence of electronic energy-loss straggling and calculating transport cross sections, the authors obtain strong evidence for contributions of electron-promotion events to ion energy loss at low velocities.

Compositional and Structural Modifications by Ion Beam in Graphene Oxide for Radiation Detection Studies

In the present study, graphene oxide foils 10 μm thick have been irradiated in vacuum using same charge state (one charge state) ions, such as protons, helium and oxygen ions, at the same energies (3 MeV) and fluences (from 5 × 1011 ion/cm2 to 5 × 1014 ion/cm2). The structural changes generated by the ion energy deposition and investigated by X-ray diffraction have suggested the generation of new phases, as reduced GO, GO quantum dots and graphitic nanofibers, carbon nanotubes, amorphous carbon and stacked-cup carbon nanofibers. Further analyses, based on Rutherford Backscattering Spectrometry and Elastic Recoil Detection Analysis, have indicated a reduction of GO connected to the atomic number of implanted ions. The morphological changes in the ion irradiated GO foils have been monitored by Transmission Electron, Atomic Force and Scanning Electron microscopies. The present study aims to better structurally, compositionally and morphologically characterize the GO foils irradiated by different ions at the same conditions and at very low ion fluencies to validate the use of GO for radiation detection and propose it as a promising dosimeter. It has been observed that GO quantum dots are produced on the GO foil when it is irradiated by proton, helium and oxygen ions and their number increases with the atomic number of beam gaseous ion.

Lattice damage in InGaN induced by swift heavy ion irradiation

The microstructural responses of In0.32Ga0.68N and In0.9Ga0.1N films to 2.25 GeV Xe ion irradiation have been investigated using x-ray diffraction, Raman scattering, ion channeling and transmission electron microscopy. It was found that the In-rich In0.9Ga0.1N is more susceptible to irradiation than the Ga-rich In0.32Ga0.68N. Xe ion irradiation with a fluence of 7 × 1011 ions⋅cm−2 leads to little damage in In0.32Ga0.68N but an obvious lattice expansion in In0.9Ga0.1N. The level of lattice disorder in In0.9Ga0.1N increases after irradiation, due to the huge electronic energy deposition of the incident Xe ions. However, no Xe ion tracks were observed to be formed, which is attributed to the very high velocity of 2.25 GeV Xe ions. Point defects and/or small defect clusters are probably the dominant defect type in Xe-irradiated In0.9Ga0.1N.

Angular dependence of proton-induced single event transient in silicon-germanium heterojunction bipolar transistors

We investigate the angular dependence of proton-induced single event transient (SET) in silicon-germanium heterojunction bipolar transistors. Experimental results show that the overall SET cross section is almost independent of proton incident angle. However, the proportion of SET events with long duration and high integral charge collection grows significantly with the increasing angle. Monte Carlo simulations demonstrate that the integral cross section of proton incident events with high ionizing energy deposition in the sensitive volume tends to be higher at larger incident angles, which is associated with the angular distribution of proton-induced secondary particles and the geometry of sensitive volume.

Synergistic effects in MOS capacitors with an Au/HfO2–SiO2/Si structure irradiated with neutron and gamma ray

The properties of oxide trapped charges and interface state density in the metal oxide semiconductor (MOS) capacitors with an Au/HfO2–SiO2/Si structure were investigated under irradiation of 14 MeV neutron and 60Co gamma-ray. In the mixed neutron and gamma irradiation environment, the formation of the oxide trapped charges in the HfO2–SiO2 layer is determined by the total deposited ionization energy, i.e. the sum of ionization energy deposition of the neutrons and the accompanying gamma rays, while the influence of the displacement damage caused by 14 MeV neutrons can be ignored. The interface state density depends not only on the ionizing energy loss (IEL) but also the non-IEL (NIEL), and NIEL plays a major role below the critical neutron fluence of 4.5 × 1012 n cm−2. The synergistic effect of the interface state is observed increases with energy deposition in the oxide at lower fluences, while decreasing above the critical fluence. These results confirm the existence of the synergistic effect of neutron and gamma irradiation in damaging HfO2 MOS devices.

Realistic energy deposition and temperature heating in molecular clouds due to cosmic rays: a computation simulation with the GEANT4 code employing light particles and medium-mass and heavy ions

ABSTRACT In the interstellar medium, Galactic and extragalactic cosmic rays (CRs) penetrate deeper in the molecular clouds (MCs) and promote inside several physical and physicochemical changes due to the energy deposition, including gas and grain heating, and triggering also molecular destruction and formation. In this work, in an attempt to simulate, in a more realistic way, the energy delivered by CRs in a typical MC (mass ∼5400 M☉ and size ∼106 au; mainly composed of H atoms), we combine the energy deposition of light particles and heavy ions, with the new calculations considering the medium-mass ions (3 ≤ Z ≤ 11). To execute the calculation, the Monte Carlo toolkit GEANT4 was applied to get the energy deposition rate per mass from many kinds of secondary particles, used in nuclear and hadron physics. The energy deposition by its induced cascade shower within the MC was characterized, as well as the relative energy deposition for all members of the medium-mass group. The results show that the incoming protons are the dominant source in the energy deposition and heating of the cloud, followed by alphas and electrons, with the medium-mass-ion and heavy-ion groups each contributing roughly 8 per cent. The current model also shows a temperature enhancement of up to 10 per cent in the external layers of the cloud (reaching 22.5 K) with respect to the previous calculations where only light particles were considered. However, neither heavy nor medium-mass ions contribute to the temperature enhancement in the deep core of the cloud.

Structural phase modifications induced by energetic ion beams in graphene oxide

Different ion beams, with energy from 2 MeV up to 16 MeV at different atomic number, have been employed to irradiate graphene oxide (GO) foils in vacuum. Due to effects of electron and nuclear ion stopping powers, the ion energy deposition reduces the irradiated GO foils and structurally modifies them. The ion bombarded GO foils X-ray diffraction (XRD) investigations have permitted to shed light on the different structural phases induced by the ion energy deposition. The changes in the GO foils pristine structure shift the diffraction main peak towards larger angles and produce new diffraction peaks indicating the presence of new phases, such as reduced GO (rGO), carbon nanotubes (CNT), amorphous carbon (a-C), onion like carbon (OLC) and probably new carbon allotropes. The obtained results indicate that the inner structure of the GO foils becomes more and more compact and dense with the absorbed dose, suggesting that the removal of the functional oxygen groups leads to a near graphite structure with a significant increase of the material mass density. The different structural phase modifications induced by the different ion beams as a function of the stopping power, fluence and dose will be presented and discussed in detail.

Measurement of Ion Energy Distribution and Deposition of Ti Thin Films Using ABPPS Technology on Glass Substrate

Ion energy distributions (IEDs) play an important role in material processes and thin film deposition. We developed a newly designed multistep pulsed power supply (modulator) for the asymmetric bipolar pulsed power sputtering (ABPPS) technology and studied the effect of reverse bias voltage in improving the properties of thin films through Ti deposition. Using an ion energy analyzer, we confirmed IEDs and relative ion intensity under a reverse bias voltage of the modulator at the substrate position. A dense plasma was generated near the sputter target at reverse bias voltages above 300 V. Experiments were conducted by varying the bias voltage applied to the sputter target and the duty cycle of the modulator. Our results demonstrate that the in-house-built ABPPS system can be used to clean the sample surfaces without requiring additional energy sources or substrate bias and that thin films prepared using this system have a smoother surface than those prepared by conventional sputtering.