Function Of Particle Energy Research Articles

Timing performance of the CMS High Granularity Calorimeter prototype

This paper describes the experience with the calibration, reconstruction and evaluation of the timing capabilities of the CMS HGCAL prototype in the beam tests in 2018. The calibration procedure includes multiple steps and corrections ranging from tens of nanoseconds to a few hundred picoseconds. The timing performance is studied using signals from positron beam particles with energies between 20 GeV and 300 GeV. The performance is studied as a function of particle energy against an external timing reference as well as standalone by comparing the two different halves of the prototype. The timing resolution is found to be 60 ps for single-channel measurements and better than 20 ps for full showers at the highest energies, setting excellent perspectives for the HGCAL calorimeter performance at the HL-LHC.

Sputtering from rough tungsten surfaces: Data-driven molecular dynamics simulations

The sputtering of tungsten surfaces caused by hot plasma particles is an important process in fusion reactors where divertors are typically made of tungsten sheets. In this study, we present a molecular dynamics simulation strategy to investigate the sputtering yields of tungsten surfaces with geometrical defects. This should serve as a model for non-monocrystalline surfaces in general and could also be a rough model for nanoscale “fuzzy” layers, which are known to be formed by surface bombardment with energetic particles. Using a non-cumulative approach, we simulate the irradiation of tungsten surfaces with cone-shaped, cylindrical, and spherical defects by argon atoms. We analyze the sputtering yields as functions of particle energy and defect sizes. As a result, we find that surfaces with distinctly shaped defects always exhibit reduced sputtering yields, compared to smooth ones. We also investigate the angular distributions of sputtered particles and find them mostly to be in accordance with prior experimental and computational results.

Attenuation range of particle radiations (alpha and beta) in human skin by Monte Carlo simulation

Particle radiations such as alpha and beta particles are more hazardous to humans than photons because of their higher linear energy transfer (LET). It is important to analyze the profile of particle radiations when interact with human skin. It is generally said that α particles can be stopped by a piece of paper while β rays can be stopped by an aluminum plate. A Monte Carlo simulation (PHITS code) is used for determining the attenuation and range of commonly available alpha (Po-210, Po-214, Am-241) and beta sources (Y-90) in human skin. These particle radiations were set at the surface of several materials such as skin, paper, water, aluminium and air to see their distribution within the materials. The PHITS code outputs were verified by comparing it with other literature for its range in air. Results showed that alpha particles barely pass through the outer layer of dead human skin and definitely can be stopped by a piece of paper. From the particle trajectory output, fluence of α particles from Po-210, Po-214, and Am-241 are completely stopped at 0.005 cm, 0.009 cm, and 0.012 cm in a paper, respectively, with no secondary particles are generated. On the other hand, beta particles would easily penetrate human skin and its range in human skin is ~0.8 cm for Y-90, while it would stop at ~0.3 cm in aluminium. In conclusion, based on these simulations, it was found that this study had justified the common sense on the shielding for the particle by using paper for alpha and aluminium for beta particle as a function of particle energy. Calculation with PHITS can be used for range calculation of various radiation types, including neutron and proton particles.

Particle resonances in toroidal fusion devices

Resonances of high energy particles in magnetic confinement devices due to electromagnetic instabilities can strongly modify the distribution, leading to a reduction in fusion power and even discharge termination and particle loss to the device walls through avalanche. The existence of a mode particle resonance depends on properties of the equilibrium, particle trajectories, and perturbation mode harmonic content. Resonance location is a function of particle energy and equilibrium field line helicity. Different methods for finding resonance location and energy dependence are developed. The properties of resonances are discussed using examples from magnetic fusion devices. We show that if mode resonances exist at low particle energy, they very likely also exist at high energy, thus modifying high energy beam particles and fusion products. It is possible for a resonance to appear due to mode induced orbit helicity modification when it is forbidden at low mode amplitude.

Proton and Hydrogen Transport through Hydrogen Environments: Ionization and Stripping

Abstract Data are presented over a wide range of impact energies describing the ionization or stripping probability, projectile energy loss, and ejected electron and recoiling target energies and angles for proton and hydrogen passage through hydrogen astrophysical environments. These kinematic and reaction data are tabulated at three levels of detail for use in heavy-particle (H+, H) and secondary-electron transport simulations: (1) the integral scattering cross section and average values of the distributions of energy and angle of the particles, (2) the singly differential cross sections as a function of particle energy and angle, and (3) a subset of the many possible doubly differential cross sections as functions of the particle energy and angle chosen to be most relevant to transport simulations.

Novel aspects of cosmic ray diffusion in synthetic magnetic turbulence

The diffusive motion of charged particles in synthetic magnetic turbulence with different properties is investigated by using numerical simulations with unprecedented dynamical range, which allow us to ensure that both the inertial range and the long wavelength part of the turbulent spectrum are properly described. This is of particular importance in evaluating previous suggestions that parallel and perpendicular diffusion coefficients differ in their energy dependence, an assertion at odds with the many claims of universality of the $D_{\perp}$ and $D_{\parallel}$ as functions of particle energy. Cases with and without an ordered magnetic field are discussed. Results of the numerical simulations are compared with available theoretical models, for slab, slab/2D and isotropic turbulence. We find widespread evidence that universality is broken, and that the ratio $D_{\perp}/D_{\parallel}$ is not independent of energy. The implications of this finding for the physics of cosmic ray transport are discussed in depth.

First-principles Demonstration of Diffusive-advective Particle Acceleration in Kinetic Simulations of Relativistic Plasma Turbulence

Abstract Nonthermal relativistic plasmas are ubiquitous in astrophysical systems like pulsar wind nebulae and active galactic nuclei, as inferred from their emission spectra. The underlying nonthermal particle acceleration (NTPA) processes have traditionally been modeled with a Fokker–Planck (FP) diffusion-advection equation in momentum space. In this Letter, we directly test the FP framework in ab initio kinetic simulations of driven magnetized turbulence in relativistic pair plasma. By statistically analyzing the motion of tracked particles, we demonstrate the diffusive nature of NTPA and measure the FP energy diffusion (D) and advection (A) coefficients as functions of particle energy . We find that scales as in the high-energy nonthermal tail, in line with second-order Fermi acceleration theory, but has a much weaker scaling at lower energies. We also find that A is not negligible and reduces NTPA by tending to pull particles toward the peak of the particle energy distribution. This study provides strong support for the FP picture of turbulent NTPA, thereby enhancing our understanding of space and astrophysical plasmas.

Calculation of the atom displacement concentration in YVO4 and PbMoO4 crystals as a function of electrons or neutrons energy

This work is devoted to the calculation of concentration of radiation displacement defects (RDDs, i.e. atoms, cations or anions displaced from positions in lattice and their associated vacancies) in YVO4 and PbMoO4 crystals as a function of particle energy (electrons and neutrons). Energy dependencies of RDD concentrations are discussed in comparison with results of other complex oxide crystals. The obtained results show that the case of electron irradiation the radiation hardness of YVO4 and PbMoO4 is higher than for other oxide crystals.

The magnitude and effects of extreme solar particle events

The solar energetic particle (SEP) radiation environment is an important consideration for spacecraft design, spacecraft mission planning and human spaceflight. Herein is presented an investigation into the likely severity of effects of a very large Solar Particle Event (SPE) on technology and humans in space. Fluences for SPEs derived using statistical models are compared to historical SPEs to verify their appropriateness for use in the analysis which follows. By combining environment tools with tools to model effects behind varying layers of spacecraft shielding it is possible to predict what impact a large SPE would be likely to have on a spacecraft in Near-Earth interplanetary space or geostationary Earth orbit. Also presented is a comparison of results generated using the traditional method of inputting the environment spectra, determined using a statistical model, into effects tools and a new method developed as part of the ESA SEPEM Project allowing for the creation of an effect time series on which statistics, previously applied to the flux data, can be run directly. The SPE environment spectra is determined and presented as energy integrated proton fluence (cm−2 ) as a function of particle energy (in MeV). This is input into the SHIELDOSE-2, MULASSIS, NIEL, GRAS and SEU effects tools to provide the output results. In the case of the new method for analysis, the flux time series is fed directly into the MULASSIS and GEMAT tools integrated into the SEPEM system. The output effect quantities include total ionising dose (in rads), non-ionising energy loss (MeV g−1 ), single event upsets (upsets/bit) and the dose in humans compared to established limits for stochastic (or cancer-causing) effects and tissue reactions (such as acute radiation sickness) in humans given in grey-equivalent and sieverts respectively.

SU-E-T-306: Electronic Equilibrium in RBE of DSB Induction in Monte Carlo Simulations of Low Energy Photon and Electron Track Structures

Purpose: The study of DNA double‐strand breaks (DSB) induction by ionizing radiation can provide understanding of linear quadratic formalism failures for complex cases such as stereotactic body radiation therapy. Using Monte Carlo simulations in cell nuclear volumes and adequate DNA modelling, estimation of DSB's is possible for various radiation fields. This study aims to evaluate the impact of electronic equilibrium (EE) and lack‐thereof on dosimetric quantities such as dose, number of ionizations and excitations and subsequently on simulated DSB's and on the relative biological effectiveness (RBE). Methods: Using Geant4 with the newly added Geant4‐DNA low energy processes, we simulated track structures of mono‐energetic photons and electrons (0.280 to 20 keV), including Auger electrons and fluorescence photons deexcitation products, and scored energy deposition interactions inside liquid water micro‐volumes of various shapes and sizes. Electronic equilibrium conditions were varied by changing the relative size of the particle source and volume of interest. Results: The total number of energy depositions interactions inside the volume varied around 0.62+/−0.04 interactions/eV and was almost constant for all analyzed EE conditions. However, the spatial distribution is affected by EE conditions and lack of interactions around the edges of the volume of 30% were scored. When coupled to a fixed position geometrical DNA model, simulated strand breaks are underestimated by up to 10% influencing the RBE of DSBs induction as a function of particle energy. Conclusion: In order to speed up miro‐dosimetric calculations, source sizes violating electronic equilibrium are often used. Simulated DSB's in a fixed geometrical model for different incident particle energies in electronic deequilibrium conditions, can thus be skewed by up to 10%. To circumvent this effect, sources satisfying electronic equilibrium in the volume for all energies or probabilistic delocalized DNA models need to be used. Fond de Recherche en Sante du Quebec Canadian Institutes of Health Research

Calibration studies and the application of nuclear track detectors to the detection of charged particles

Abstract This paper describes calibration studies of solid state nuclear track detectors (SSNTDs) of he CR-39/PM-355 type. A dozen or so PM-355 detector samples were cut out from detector sheets delivered at different times and were irradiated with mono-energetic protons, deurerons and helium ions of energy ranging up to a few MeV. After that, the samples were etched and track opening diameters were determined as a function of particle energy and detector etching time. These studies were motivated by the application of the detectors in fusion experiments to measure energetic ions which escape high-temperature plasmas. The calibration diagrams obtained enable us to compare the relative sensitivities of detectors from different batches and to use these detectors in an optimal way.

ULTRA-HIGH-ENERGY COSMIC RAYS FROM CENTAURUS A: JET INTERACTION WITH GASEOUS SHELLS

Ultra high energy cosmic rays (UHECRs), with energies above ~6 x 10^19 eV, seem to show a weak correlation with the distribution of matter relatively near to us in the universe. It has earlier been proposed that UHECRs could be accelerated in either the nucleus or the outer lobes of the nearby radio galaxy Cen A. We show that UHECR production at a spatially intermediate location about 15 kpc northeast from the nucleus, where the jet emerging from the nucleus is observed to strike a large star-forming shell of gas, is a plausible alternative. A relativistic jet is capable of accelerating lower-energy heavy seed cosmic rays (CRs) to UHECRs on timescales comparable to the time it takes the jet to pierce the large gaseous cloud. In this model many CRs arising from a starburst, with a composition enhanced in heavy elements near the knee region around PeV, are boosted to ultra-high energies by the relativistic shock of a newly oriented jet. This model matches the overall spectrum shown by the Auger data and also makes a prediction for the chemical composition as a function of particle energy. We thus predict an observable anisotropy in the composition at high energy in the sense that lighter nuclei should preferentially be seen toward the general direction of Cen A. Taking into consideration the magnetic field models for the Galactic disk and a Galactic magnetic wind, this scenario may resolve the discrepancy between HiRes and Auger results concerning the chemical composition of UHECRs.

Response of the radiation belt electron flux to the solar wind velocity: Parameterization by radial distance and energy

The solar wind velocity is the primary driver of the electron flux variability in Earth's radiation belts. The response of the logarithmic flux (“log-flux”) to this driver has been determined at the geosynchronous orbit and at a fixed energy [Baker, D.N., McPherron, R.L., Cayton, T.E., Klebesadel, R.W., 1990. Linear prediction filter analysis of relativistic electron properties at 6.6 RE. Journal of Geophysical Research 95(A9), 15,133–15,140) and as a function of L shell and fixed energy [Vassiliadis, D., Klimas, A.J., Kanekal, S.G., Baker, D.N., Weigel, R.S., 2002. Long-term average, solar-cycle, and seasonal response of magnetospheric energetic electrons to the solar wind speed. Journal of Geophysical Research 107, doi:10.1029/2001JA000506). In this paper we generalize the response model as a function of particle energy (0.8–6.4 MeV) using POLAR HIST measurements. All three response peaks identified earlier figure prominently in the high-altitude POLAR measurements. The positive response around the geosynchronous orbit is peak P 1 ( τ=2±1 d; L=5.8±0.5; E=0.8–6.4 MeV), associated with high-speed, low-density streams and the ULF wave activity they produce. Deeper in the magnetosphere, the response is dominated by a positive peak P 0 (0±1 d; 2.9±0.5 R E; 0.8–1.1 MeV), of a shorter duration and producing lower-energy electrons. The P 0 response occurs during the passage of geoeffective structures containing high IMF and high-density parts, such as ICMEs and other mass ejecta. Finally, the negative peak V 1 (0±0.5 d; 5.7±0.5 R E; 0.8–6.4 MeV) is associated with the “ D st effect” or the quasiadiabatic transport produced by ring-current intensifications. As energies increase, the P 1 and V 1 peaks appear at lower L, while the D st effect becomes more pronounced in the region L<3. The P 0 effectively disappears for E>1.6 MeV because of low statistics, although it is evident in individual events. The continuity of the response across radial and energy scales supports the earlier hypothesis that each of the three modes corresponds to a qualitatively different type of large-scale electron acceleration and transport.

Errors in ram velocity and temperature measurements inferred from satellite-borne retarding potential analyzers

Retarding potential analyzers (RPAs) [Heelis and Hanson, Measurement Techniques in Space Plasmas, in Geophys. Monogr. Ser., Vol. 102 (AGU, Washington, D.C., 1998), p. 61] have been used extensively in space science over the past five decades to provide in situ estimates of ion velocities and temperatures. It has been shown previously that the use of biased grids in such instruments creates a nonuniform potential in the grid plane, which leads to errors in inferred parameters. A simulation of ion interactions with biased grids has been developed using a commercial finite-element analysis software package. Using a statistical approach, perturbations to the idealized RPA equation are discussed with the intent of developing quantitative corrections for the inferred parameters. The transparency of the grid stacks is found to be a function of particle energy and angle of attack. A preliminary case study is presented and compared to previous work.

Concentration of radiation displacement defects in BSO and BGO crystals irradiated by electrons or neutrons

Abstract This work is devoted to the calculation of the concentration of radiation displacement defects (RDD) in bismuth germanate and bismuth silicate crystals as a function of particle energy (electrons and neutrons). Energy dependencies of RDD concentrations are discussed in comparison with results for other complex oxide crystals. The obtained results show that for the case of electron irradiation the radiation hardness of BSO and BGO should be similar to other oxide crystals, but for neutrons is drastically smaller. Additionally, for the neutron irradiation, the efficiency of the production of defects in the oxide sublattice is drastically smaller than for other oxide crystals.

Concentration of Radiation Displacement Defects in Complex Oxide Crystals upon Energy of Particle

The present work is devoted to the calculation of the radiation displacement defects (RDD) concentration in complex oxide crystals (Y3Al5O12, Gd3Ga5O12, YAlO3, LiNbO3) as a function of particle energy (electrons and neutrons). Energy dependencies of RDD concentration are discussed. The results of calculations show that the concentrations of RDD reduced to one impinging particle increased initially with the particles energy and they saturates for the electron and neutron energy above 25 MeV. The comparison of the concentrations of RDD calculated for different sub-lattices as well as for the cases of electrons and neutrons is made. The obtained results are compared with the experimental data.

Temporal signatures of radiation belt electron precipitation induced by lightning‐generated MR whistler waves: 1. Methodology

We present a novel technique designed to calculate the detailed differential number flux signature (as a function of energy and time) of precipitating radiation‐belt electrons, driven by a magnetospherically reflecting (MR) whistler wave, initiated by a single cloud‐to‐ground lightning discharge. Our model consists of several stages. First, we calculate the MR whistler wave characteristics at 1° latitude intervals along a given field‐line. This is accomplished using an extensive ray tracing and interpolation algorithm involving ∼120 million rays, and accounting for the effects of Landau damping, spatial, and temporal dispersion. We then use these wave characteristics to compute the pitch angle changes of resonant electrons by assuming that the interactions are linear, and independent between adjacent latitude and wave frequency bins. The pitch angle changes are transformed to precipitating flux using a novel convolution method and displayed as a function of particle energy and time at the feet of a given field line. We have calculated and compared the differential number flux signatures at the northern and southern feet of the L = 2.3 and L = 3 field lines, and found that precipitation onset and duration times increase with latitude (consistent with previous work). The precipitation consists of suprathermal Landau resonance electrons (E ≲ 10 keV) which are intense but contribute little to the total energy flux, a flux gap (10 keV ≲ E ≲ 80 keV) corresponding to a change in coupling mechanism from Landau resonance to gyroresonance, and a series of precipitation swaths (E ≳ 80 keV) corresponding to gyroresonance interactions. The swaths result in periodic maxima in the precipitated energy flux, which correspond to the equatorial traversals of the underlying MR whistler wave energy. Global precipitation signatures were computed for a number of lightning discharge latitudes and are presented in a companion paper (Bortnik et al., 2006).

Gene Expression Changes in Normal Human Skin Fibroblasts Induced by HZE-Particle Radiation

Studies have shown that radiation exposure affects global gene expression in mammalian cells. However, little is known about the effects of HZE particles on gene expression. To study these effects, human skin fibroblasts were irradiated with HZE particles of different energies and LETs. The data obtained from these experiments indicate that changes in gene expression are dependent on the energy of the radiation source. Particles with the highest energy, i.e. iron, induced the biggest expression changes in terms of numbers of genes and magnitudes of changes. Many genes were found to undergo significant expression changes after HZE-particle irradiation, including CDKN1A/p21, MDM2, TNFRSF6/fas, PCNA and RAD52. Unlike X rays, HZE particles expose cells to two types of radiation: primary ions and delta rays. We hypothesized that the biological effects of delta rays, which are secondary electron emissions, should resemble the effects of X rays. To explore this idea, gene expression changes between cells that had been irradiated with HZE particles and X rays were compared. The results support our hypothesis since the number of genes that commonly changed after exposure to both radiations increased as a function of particle energy.

Modelling the energy dependence of helium ion TL fluence response using the extended track interaction model

Helium ion thermoluminescence (TL) fluence response is calculated as a function of particle energy from 1 to 10 MeV in the framework of the extended track interaction model (ETIM). The results of Monte Carlo calculations of absorbed dose as a function of the radial distance from the He ion track axis are employed for 1, 2, 2.6, 3.5, 4.95, 6.76 and 10 MeV He ions in condensed phase LiF. The radial dose is then transformed to radial occupation probabilities for the TL trapping and luminescent defect centres using optical absorption (OA) dose filling constants based on experimental gamma/electron OA dose response measurements. The radial defect occupation probabilities are used to estimate the track structure parameters (TSPs) r100 (full occupation defining the track core), r50 (50% occupation) and rh (track extension). These, of course, may be different for the trapping centres, luminescent centres and competitive centres due to their different charge carrier trapping cross-sections leading to different dose-filling constants. He ion TL fluence response (linearity, supralinearity and saturation) is then modelled in the framework of the ETIM with the TSPs and dose filling constants as input parameters. It is illustrated that the maximum supralinearity f(n)max increases smoothly with increasing particle energy due to the gradually increasing track radial extension and the increase in the number of electrons escaping the parent track, Ne, relative to the number recombining within the parent track, Nw.

Thin-target excitation functions: a powerful tool for optimising yield, specific activity and radionuclidic purity of accelerator-produced radionuclides

In accelerator production of radionuclides, thin-target yield yEOIB(E) vs. projectile energy, at the end of an instantaneous bombardment (EOIB), is the slope at the “origin” of the growth curve of the activity of a radionuclide per unit beam current vs. irradiation time, for a target in which the energy loss is negligible in respect to projectile energy. Conversely, thick-target yield Y(E,ΔE) is a function of particle energy E (MeV) onto the target and energy loss ΔE (MeV) into target itself, obtained experimentally or by integration of thin-target excitation function y(E). Some local maxima on Y(E,ΔE) curves are present in many cases. As a relevant conclusion, use of target thickness larger than the “effective” value is unsuitable, due to larger specific power deposited by the beam in target material, instead of cooling system. Moreover, increasing amount of target material leads to a lower value of specific activity, due to larger amounts and volumes of chemicals and equipment. Y(E,ΔE) curves and their maxima permit calculating optimal irradiation conditions to produce radionuclides with maximum yield, specific activity and radionuclidic purity. In order to join the advantages of accurate knowledge of thin-target excitation functions, very selective radiochemical separations were optimised, without intentional addition of an isotopic carrier.