Energy Loss Of Protons Research Articles

Collision dynamics of proton to water dimer at 250 eV

Applying a real-space, real-time implementation of time-dependent density functional theory coupled to molecular dynamics (TDDFT-MD) non-adiabatically, we study the ionization and fragmentation of water dimer in collision with a proton at 250 eV. Four different incident orientations with various impact parameters are employed to account for orientation effects. The reaction channels, electronic density evolution, scattering pattern and energy loss of proton are obtained. We find that proton is scattered away for all impact parameters and the head-on collision effects the energy loss of proton dominantly as well as the scattering angle. The locations of peaks of the scattering angles are similar to those corresponding to the energy loss. The single-electron capture, the double-electron capture as well as the total electron capture cross-sections are obtained. We find that the single-electron capture cross-section contributes most to the total electron capture cross-section and the calculated total electron capture cross-section is in reasonable agreement with experimental and other theoretical results with respect to water gas and liquid water.

Collision of ultra-relativistic proton with strong magnetic field: Production of ultra-high energy photons and neutrinos

Proton-proton interaction and photo-hadronic interaction in cosmic accelerators are the two main channels for the production of cosmic ultra-high energy photons and neutrinos (TeV-PeV). In this Letter, we use FWW approach to obtain the production of cosmic ultra-high energy photons and neutrinos from the collision between UHE proton with magnetic field which could be considered as the virtual photon in the rest frame of UHE proton. We name this as pB process. The threshold for the occurrence of the pB process is that the combination of the Lorentz factor of proton and the strength of the magnetic field is about γpB≃5×1018 Gauss. Beyond this threshold, the rate of energy loss of proton due to the pB process is about three orders higher than that due to the synchrotron radiation of proton in the same magnetic field. The pB process might potentially happen in the atmosphere of white dwarfs, neutron stars or even that of stellar massive black holes.

Energy loss of protons from MedAustron in silicon strip sensors

MedAustron is a hadron synchrotron primarily designed and built for tumor treatment. Besides its clinical purpose, it is equipped with a dedicated beam line for non-clinical research. This beam line can be used for beam tests utilizing protons with an energy up to 252.7MeV at the moment, but 800MeV protons and carbon ions will become available through 2019. We conducted first beam tests at MedAustron in order to understand the usability of this beam line for testing silicon detectors. This includes the design and commissioning of a trigger setup based on scintillators and PMTs, which is meant to stay permanently there. This allowed us to measure energy deposition utilizing silicon strip sensors read out by the ALiBaVa system. Nominal beam energies were varied between 62.4 and 252.7MeV and verified by determining the specific energy loss of protons in silicon. As these energies are rather low compared to typical HEP beam tests, the proton beam through the setup was simulated to determine the necessary energy correction due to losses through matter and air in front of the Si sensor. These approaches yielded good agreement with reference data from NIST, so MedAustron is considered as a reliable facility for future beam tests.

Физика планирования протонной лучевой терапии

The most important stage of radiation therapy of oncological diseases is the planning of radiation treatment. In this work, this complex process in relation to proton therapy is proposed to be divided into medical and physical planning. In conventional therapy with photons and electrons, the latter is usually called dosimetric planning, however, when applied to proton radiation therapy, this stage involves a significantly wider range of tasks related to the modification and scanning of the proton beam, spreading and compensation of ranges, taking into account when planning for uncertainties and finiteness of proton ranges, a decrease in the contribution to the dose of secondary neutrons, the creation of error-tolerant optimization algorithms for dosimetric plans, and, finally, a precision calculation of dose distributions. The paper discusses the main stages and problems of physical planning of proton radiation therapy. Particular attention is paid to the formation of an extended high-dose region (extended Bragg peak) using the beam scattering method and scanning method, and to the algorithms for calculating the dose distributions created by protons in the scattering and beam scanning systems. The most detailed consideration is given to different versions of the proton pencil beam method, which allows to increase the dose calculation accuracy and take into account the transverse scattering and fluctuations in proton energy losses, especially at the end of the path (halo effect), analytical and numerical methods. Scanning are divided into three main technologies: homogeneous scanning, single field uniform dose (SFUD), multi-field uniform dose (MFUD), often called intensity modulated proton therapy (IMPT). Actual accounting problems are considered when planning the irradiation of the movement of organs, and uncertainties in determining path lengths and optimization of irradiation plans. In particular features, problems and modern approaches to the optimization of dosimetry plans of proton radiation therapy are discussed. It is noted that one of the most promising practical solutions for the uncertainty management in determining the path lengths of protons in optimization is to include possible errors in the objective function of the optimization algorithm. This technique ensures that an optimized irradiation plan will more reliably protect normal tissues and critical organs adjacent to the irradiation target from overexposure.

Sputtering yields of tantalum by hydrogen ions in the energy range of 3–11 keV

ABSTRACTThe total sputtering yield of 6 nm thick polycrystalline tantalum films resulting from H2+ ion bombardment, at normal incidence, has been determined. For this purpose, we study the evolution of the energy loss of protons transmitted through very thin films of tantalum following bombardment with controlled doses of H2+. The energy of the incident ions ranges from 3 to 11 keV. Our method allows us to determine how to find the limit of the thin film surface contamination which is important for stopping power measurements of pure samples. It also allows to prepare films of predetermined variable thickness.

The Atmospheric Radiation Interaction Simulator (AtRIS): Description and Validation

AbstractWe present the Atmospheric Radiation Interaction Simulator (AtRIS), a newly developed GEANT4‐based code tailored specifically to enable parametric studies of radiation propagation through various (exo)planetary atmospheres. Its main purpose is to model the altitude‐dependent atmospheric secondary particle environment and to calculate the ion pair production rates, which are a mandatory input for atmospheric chemistry models in order to, for example, directly characterize the habitability of the modeled planet. Similar codes have been developed previously (e.g., PLANETOCOSMICS; Desorgher, et al., ); however, until now, none possesses the necessary flexibility in the specification of the atmosphere and the regolith that is necessary to model planets outside our solar system. Here we provide a detailed description of AtRIS and its validation against earthbound measurements. For validation, we show comparisons against Earth measurements. Thereby, the focus is on the atmospheric altitude‐dependent ionization, the surface muon, and the neutron fluxes, as well as the primary proton fluxes. Furthermore, a comparison of the computed energy losses of monoenergetic protons based on AtRIS and PLANETOCOSMICS is shown. Our aim is to demonstrate the validity of AtRIS and its importance for future studies on, for example, potential (Earth‐like) exoplanets.

Density-dependent Energy Loss of Protons in Pb and Be Targets and Percent Mass-Stopping Power from Bethe-Bloch Formula and Bichsel-Sternheimer Data Within 1–12 MeV Energy Range: A Comparative Study Based on Bland-Altman Analysis

BackgroundThis comparative study calculated Bethe-Bloch results with Bichsel-Sternheimer values, employing the Bland-Altman analysis within 95% limit of agreement for the first time. The Bethe-Bloch formula was employed for the physical realization of the density-dependent energy loss of protons in lead (208Pb) and beryllium (9Be) targets in the energy range 1–12 MeV. MethodsThe mass-stopping power of protons for the given elements was calculated and the corresponding normalized difference and standard deviation was also calculated. The obtained theoretical results were compared with the Bichsel-Sternheimer values for the same targets within the same energy range of the projectile protons in terms of stopping-power percent difference. ResultsAs a general trend, as the energy of proton increases the percent normalized difference decreases. For elements having a high atomic number like lead, the percent difference is large. This may mean that calculated values of percent difference for heavy elements like lead are not in agreement with experimental results. ConclusionThe calculated mass-stopping power in view of the normalized percent difference is consistent with the Bichsel-Sternheimer results for the same projectile of higher energy in Pb and Be targets. However, results deviate from the Bichsel-Sternheimer results for high atomic number materials for the same projectile of lower energy. The difference may be attributed to the adjusted parameters in the Bethe-Bloch formula.

Proton scattering from tungsten fuzz

Abstract Tungsten fuzz is a nanostructure formed on tungsten surface under helium plasma impact. In this work, we investigate this structure using the scattering of keV-energy protons. Energy spectra of scattered protons have double-peak shape that corresponds to the scattering from fuzz and underlying pure tungsten. The energy losses of protons in fuzz are estimated as the difference between primary beam energy and the energy corresponding to the local minimum between two peaks. Computer simulations with SRIM code also demonstrate double-peak shape of energy spectra of protons scattered from fuzzy target. Fuzz and pure tungsten stopping powers for protons are compared and fuzz density relative to pure tungsten is estimated and discussed. Evolution of H+ energy spectra during fuzz irradiation by Ar+ beam is measured and discussed.

Energy loss of protons in hydrogen plasma

AbstractThis paper reports the measurement of the energy loss of protons at the energy of 100 keV penetrating a partially ionized hydrogen plasma. The plasma of ne≈ 1015–16cm−3; Te≈ 1–2 eV and lifetime of about 8 µs is created by the hydrogen gas discharge. The experimental results show an increase of a factor of 2.8 in the energy loss, which are in good agreement with the Bethe, Standard Stopping Model, Li–Petrasso and Vlasov models’ predictions within the error limit. The Bethe–Bloch Coulomb logarithm term is found to increase by a factor of 4.0 for free electrons as compared with the situation where bound electrons prevail. The potential application of protons energy loss for diagnosing the electron density in plasma is proposed too.

Proton energy loss in multilayer graphene and carbon nanotubes

ABSTRACTResults of a study of electronic energy loss of low keV protons interacting with multilayer graphene targets are presented. Proton energy loss shows an unexpectedly high value as compared with measurements in amorphous carbon and carbon nanotubes. Furthermore, we observe a classical linear behavior of the energy loss with the ion velocity but with an apparent velocity threshold around 0.1 a.u., which is not observed in other carbon allotropes. This suggests low dimensionality effects which can be due to the extraordinary graphene properties.

Collision dynamics of H+ + N2 at low energies based on time-dependent density-functional theory

Using time-dependent density-functional theory at the level of local density approximation augmented by a self-interaction correction and coupled non-adiabatically to molecular dynamics, we study, from a theoretical perspective, scattering dynamics of the proton in collisions with the N2 molecule at 30 eV. Nine different collision configurations are employed to analyze the proton energy loss spectra, electron depletion, scattering angles and self-interaction effects. Our results agree qualitatively with the experimental data and previous theoretical calculations. The discrepancies are ascribed to the limitation of the theoretical models in use. We find that self-interaction effects can significantly influence the electron capture and the excited diatomic vibrational motion, which is in consistent with other calculations. In addition, it is found that the molecular structure can be readily retrieved from the proton energy loss spectra due to a significant momentum transfer in head-on collisions.

Experimental investigation on diagnosing effective atomic density in gas-type target by using proton energy loss

The investigations of interaction processes between ion beams and gas and between ion beams and plasma play important roles in atomic physics, astrophysics, high energy density physics, and inertial confinement fusion.The atomic density of target is one of the key experimental parameters which may determine the interaction mechanism and experimental results.How to precisely diagnose the atomic density of target in different matter states, like gas phase and plasma phase, is challenging work on the experiments in laboratory.Conventionally the vacuum gauges are used to measure the pressure inside the gas target, but the accuracy is limited for a complex target system and they can hardly work in a strong radiation surrounding, especially in plasma where the high temperature can physically damage the gauges.Therefore we propose a new method to measure the atomic densities for both gas target and plasma target based on the heavy ion beam accelerator facility at the Institute of Modern Physics, Chinese Academy of Sciences.In our experiment the protons are extracted from an electron cyclotron resonance ion source (ECRIS) and accelerated to 100 keV then transmitted to the target.A two-stage differential pumping system is constructed to keep 10-7 mbar order of magnitude in beam line when the gas is filled into the target area where the pressure could increase to higher than 1 mbar.A 45 dipole magnet is used to bend the protons which have passed through the gas.The energy is determined by the different positions of protons at the position-sensitive detector which is placed at the end of magnet.Consequently the energy losses of protons at different pressures are obtained.There have been proposed many theories for calculating the energy loss of protons in gas, and we chose the very popular code named SRIM to simulate the experimental case. Finally the effective linear atomic density of target along the ion beam trajectory in the target area is obtained.For comparison, the conventional vacuum gauges (one is the hot cathode gauge-IonIVac ITR 90 and the other is capacitance diaphragm gauge-Varian CDG-500) are simultaneously used in the experiment.The results show that the recalibrated effective pressure obtained by the energy loss is close to the pressure measured by Varian CDG-500 but much lower than the pressure from IonIVac ITR 90.Only after the detection efficiency correction, could the corrected results of IonIVac ITR 90 be coincident with the effective pressure obtained according to energy loss.Moreover we find that the effective atomic density determined by the protons energy loss shows that these advantages over the conventional gauges are not only the high accuracy and reliability but also the in-situ measurement, high temporal resolution and the ability to work in the complex radiation and hot plasma environment.These properties may play a great role in the experimental researches and relevant topics.

Non-ionization energy loss of proton in different regions in SiC

Silicon carbide (SiC), as a representative of the third-generation semiconductor materials, is widely used in some fields which may suffer strong radiation such as in the cases of military affairs, aerospace and reactor. SiC possesses the superior radiation-resistance characteristic. However, SiC under the proton irradiation generate a lot of defects, resulting in degradation of device performance and even complete loss of its function. Therefore, the study on the irradiation damage to SiC under proton irradiation possesses important significance. A large number of studies have shown that for most of electronic devices and different types of incident particles, the degradation of device performance caused by displacement damage is linearly dependent on non-ionizing energy loss (NIEL), so the displacement damage can be evaluated by NIEL. In this work, the Monte Carlo software Geant4 is used to simulate the relationship between NIEL and proton energy, and the variation of NIEL with the depth of the material and the contribution of different types of primary recoil atoms to the total NIEL are also studied. The NIEL simulation results show that the NIEL in SiC material is less than that in Si and Ga semiconductor material under the same proton irradiation, proving that the stability and the radiation-resistance of SiC are stronger. The simulation results of NIEL at different depths show that the most serious damage regions of the material under different energy protons are diverse. Under the irradiation of low energy proton, the most serious region of the displacement damage occurs at the end of the proton range. With the increase of proton energy, the worst damage region of material will gradually move from the end of the proton range to the surface of SiC material. According to the contribution of different types of primary recoil atoms to the total NIEL, when the energy of the incident proton is low, the displacement damage of the proton in the SiC is mainly caused by 28Si and 12C, and the damage caused by 28Si is obviously higher than that by 12C. As the energy of proton increases, the 28Si and 12C are still the main causes of Bragg peak of the NIEL at the end of the proton range, but the number of ions generated by nuclear reactions increases accordingly, and the displacement damage caused by these ions increases in the shallow area of SiC, leading the surface of the material to be the worst damaged region. The combination of the two factors caused the most serious damage region moves from the end of the proton range to the surface of the material with the increase of proton energy. The results of this study are useful for the application of SiC devices to irradiation environment.

Energy-Dependent Degradation Characteristics of AlGaN/GaN MISHEMTs with 1, 1.5, and 2 MeV Proton Irradiation

We investigated the degradation characteristics of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) and Schottky HEMTs induced by proton irradiation at energy levels of 1, 1.5, and 2 MeV, with a total fluence of 5 × 1014 cm−2. Irradiated devices exhibited degradation characteristics of positive threshold voltage (Vth) shift and drain current (ID) reduction, which increased as the proton energies decreased. Hall pattern measurement revealed that the Hall mobility (μ), sheet carrier concentration (nsh), and sheet resistance (Rsh) of the electron channel were also degraded after proton irradiation (showing the same energy dependence). This effect can be attributed to the energy-dependent energy loss of protons penetrating the semiconductor material. Protons with lower irradiation energy can degrade the device characteristics more severely because of the larger amount of nonionizing energy loss (NIEL) in the active region, in which a two-dimensional electron gas (2-DEG) is formed as compared to higher irradiation energies where the energy loss is primarily in the bulk substrate. The capacitance-voltage (C-V) measurements indicated significant degradation of the insulator interface for 1-MeV irradiation.

DEVELOPMENT OF A HIGH-EFFICIENCY PROTON RECOIL TELESCOPE FOR D-T NEUTRON FLUENCE MEASUREMENT.

A high-efficiency proton recoil telescope was developed to determine neutron fluences in neutron fields using the 3H(d,n)4He reaction. A 2-mm thick plastic scintillation detector was employed as a radiator to increase the detection efficiency and compensate for the energy loss of the recoil proton within. Two silicon detectors were employed as the ΔE and E detectors. The distance between the radiator and the E detector was varied between 50 and 150 mm. The telescope had detection efficiencies of 3.5 × 10-3 and 7.1 × 10-4 cm2 for distances of 50 and 100 mm, respectively, which were high enough to determine the neutron fluence in 14.8-MeV neutron fields, with a few thousand cm-2 s-1 fluence rate, within a few hours.

Role of Elastic Scattering of Protons, Muons, and Electrons in Inducing Single-Event Upsets

The contribution of elastic scattering to single-event upset (SEU) by low-energy protons is usually considered negligible. This paper develops the formulas needed for calculating the cross section (CS) to create Si recoils of the elastic scattering of protons, muons, and electrons in silicon devices. The results are used to calculate SEU CS. This is compared with existing experimental results and with Monte Carlo calculations. For protons, the elastic scattering-induced SEU has a dominant role in sensitive devices at energies between about 2 and 10 MeV. The sum of this process with the inelastic scattering and direct ionization is in good agreement with experiments. For muons, the elastic SEU is significant at energies larger than 100 MeV. In the atmosphere, such muons have high flux. However, their elastic CS is small and the effect of the Si recoils is less important than that due to neutrons and protons in the atmosphere. For electrons, the elastic scattering starts to be significant at tens of MeV energies, as found experimentally. The expressions of elastic scattering were used for calculating the nuclear stopping power and the nonionizing energy loss (NIEL) of protons, muons, and electrons. The results are in agreement with published data.

Theoretical study on collision dynamics of H+ + H2O at low energies

ABSTRACTScattering dynamics of a water molecule in collision with proton is studied based on a time-dependent density functional theory and coupled with the molecular dynamics method, in which the electrons are described by quantum mechanics and the nuclei are described by classical mechanics. Four different incident directions at 46 eV are chosen in order to investigate the orientations effect, and the energy-dependent effect in low energy region is explored under impact energies 27, 36 and 46 eV. Reaction channels, scattering angles and energy loss of protons are calculated. The differences between those characteristics are unobvious in large impact parameters, which are irrespective of the incident orientations due to weak projectile-target interaction. In small impact parameters, the results strongly depend on the collision energy and orientation.

The optimal balance between quality and efficiency in proton radiography imaging technique at various proton beam energies: A Monte Carlo study

Proton radiography is a novel imaging modality that allows direct measurement of the proton energy loss in various tissues. Currently, due to the conversion of so-called Hounsfield units from X-ray Computed Tomography (CT) into relative proton stopping powers (RPSP), the uncertainties of RPSP are 3–5% or higher, which need to be minimized down to 1% to make the proton treatment plans more accurate.In this work, we simulated a proton radiography system, with position-sensitive detectors (PSDs) and a residual energy detector (RED). The simulations were built using Geant4, a Monte Carlo simulation toolkit. A phantom, consisting of several materials was placed between the PSDs of various Water Equivalent Thicknesses (WET), corresponding to an ideal detector, a gaseous detector, silicon and plastic scintillator detectors. The energy loss radiograph and the scattering angle distributions of the protons were studied for proton beam energies of 150MeV, 190MeV and 230MeV. To improve the image quality deteriorated by the multiple Coulomb scattering (MCS), protons with small angles were selected. Two ways of calculating a scattering angle were considered using the proton’s direction and position.A scattering angle cut of 8.7mrad was applied giving an optimal balance between quality and efficiency of the radiographic image. For the three proton beam energies, the number of protons used in image reconstruction with the direction method was half the number of protons kept using the position method.

Low- and intermediate-energy stopping power of protons and antiprotons in solid targets

In this work we propose a non-perturbative approximation to the electronic stopping power based on the central screened potential of a projectile moving in a free electron gas, by Nagy and Apagyi. We used this model to evaluate the energy loss of protons and antiprotons in ten solid targets: Cr, C, Ni, Be, Ti, Si, Al, Ge, Pb, Li and Rb. They were chosen as canonicals because they have reliable values of the Seitz radio, rS=1.48-5.31 a.u., which cover most of the possible metallic solids. Present low velocity results agree well with the experimental data for both proton and antiproton impact. Our formalism describes the binary collision of the projectile and one electron of the free electron gas. It does not include the collective or plasmon excitations, which are important in the intermediate to high velocity regime. The distinguishing feature of this contribution is that by using the present model for low to intermediate energies (below the appearance of plasmon excitations), the Lindhard dielectric formalism (including plasmons) for intermediate to high energies, and the shellwise local plasma approximation to account for the inner shell contribution, then a good full-theoretical description of the available experimental data is obtained in an extensive energy range, covering the low, intermediate and high energy region.

Ab initio research of energy loss for energetic protons in solid-density Be

Ab initio research of energy loss for energetic protons in solid-density Be is made based on the average atom model. Our results are found in good agreement with the recent experiment for both warm and cool matter. Our results are compared with the local density approximation model and the reason for their difference is also explored. The energy loss at smaller projectile energies is predicted by our model and local density approximation, which helps probe the higher reliability of the proving model and judge the existence of the non-Fermi-Dirac velocity distribution for free electrons exists in dense plasmas in future.