Energy Distribution Of Charged Particles Research Articles

Study and design of a lens-type retarding field energy analyzer without a grid electrode

A retarding field energy analyzer (RFEA) for measuring the energy distribution of charged particles offers the advantages of a simple structure and suitability for simultaneous observations of beam patterns in two dimensions. In this study, lens-based RFEAs without a grid electrode were theoretically investigated with regard to the geometry and lens condition to achieve high performance. The simulation results show that the proposed RFEA can achieve a resolution of 2.6 meV at an energy level of 500 eV. In addition, performance, which is the ratio of the resolution to the beam energy, reached 5.2×10−6. These results indicate that the RFEA designed in this study is capable of high-performance outcomes. The findings here demonstrate that the most important factors when attempting to realize a high-resolution RFEA design are to reduce the sagging effect of the electron beam through the focusing lens and ensure that V″(z) in the retarding electrode is close to zero. The design of the lens-based RFEAs is described in detail.

Time-of-flight analyzer system to detect reflected particles from a solid surface following low-energy particle injection

We have developed a time-of-flight analyzer to measure energy distributions of reflected particles from solid surfaces bombarded by low-energy (1-2 keV) ions. The analyzer yields energy distributions of neutrals which can be compared with the energy distributions of charged particles measured by a magnetic deflection-type momentum analyzer. We have tested the system to measure the angular dependence of energy and intensity for neutrals reflected from a polycrystalline W target. The energies of the reflected neutrals are much smaller than the incident ion energies, suggesting multiple scattering in the target. No angular dependence is observed under the condition that the sum of the incident and reflected angles is constant. The intensity of the reflected neutrals takes the maximum around the mirror angle. We compare these characteristics of neutral particle reflections with those of reflected ions.

Nanodosimetric measurements and calculations in a neutron therapy beam

A comparison of calculated and measured values of the dose mean lineal energy (y(D)) for the former neutron therapy beam at Louvain-la-Neuve is reported. The measurements were made with wall-less tissue-equivalent proportional counters using the variance-covariance method and simulating spheres with diameters between 10 nm and 15 microm. The calculated y(D)-values were obtained from simulated energy distributions of neutrons and charged particles inside an A-150 phantom and from published y(D)-values for mono-energetic ions. The energy distributions of charged particles up to oxygen were determined with the SHIELD-HIT code using an MCNPX simulated neutron spectrum as an input. The mono-energetic ion y(D)-values in the range 3-100 nm were taken from track-structure simulations in water vapour done with PITS/KURBUC. The large influence on the dose mean lineal energy from the light ion (A > 4) absorbed dose fraction, may explain an observed difference between experiment and calculation. The latter being larger than earlier reported result. Below 50 nm, the experimental values increase while the calculated decrease.

Calculation of energy distributions of charged particles produced by neutrons from 0.14 to 65 MeV in tissue substitutes

Energy distributions of secondary charged particles were calculated in tissue substitutes irradiated by neutrons from 0.14 to 65 MeV, using the Particle and Heavy Ion Transport code System. The calculations were compared with experimental data measured by tissue equivalent proportional counters (TEPC). It is found that the calculated distributions of the lineal energy, y, generally agree well with the measured ones for neutrons from several 100 keV to 15 MeV. In the case of 40 and 65 MeV neutron irradiations, wall effects of TEPC should be considered and the fluence of alphas is underestimated by the calculations. Integrated dose contributions of the secondary charged particles are generally in good agreement with those of the measured ones.

Cosmic rays from collapsing magnetized stars

We examine the acceleration of cosmic rays in the magnetospheres of collapsing stars with initial dipole magnetic fields and various initial energy distributions of charged particles in their magnetospheres (the exponential, relativistic Maxwellian, and Boltzmann distributions were considered). When a magnetized star contracts at the gravitational collapse stage, its magnetic field grows considerably. Such a variable magnetic field generates an eddy electric field. Our calculations suggest that this electric field can accelerate charged particles to relativistic energies. In this way collapsing stars can be sources of high-energy cosmic rays in our Galaxy as well as in other galaxies.

Energy distributions of charged particles from three-body decay

We compute the energy distributions of charged particles and neutrons emerging from the three-body decay of the 2 + -resonances of 6Be and 6Li with isospin 1. These states are isobaric analogue states to the 2 + -resonance in 6He. We use hyperspherical adiabatic expansion combined with the complex scaling method. We first investigate the adiabatic potentials and the related eigenfunctions where each has its characteristic contribution to different energy distributions. The microscopic origin of the related decay mechanisms is exhibited. The Coulomb interaction in general broadens the distributions due to long-range couplings. The method is rather efficient in the present cases. Numerically stable distributions are found at intermediate hyperradii where the basis size is sufficient to describe the asymptotic behavior. Different decay mechanisms contribute with sequential α-emission as dominating but also with substantial fractions of direct decay. Computations are consistent with available experiments.

Radiation Bursts from a Presupernova Collapsar

SummaryThe radiation from the magnetic presupernova star is calculated. This radiation will generate when the magnetosphere of presupernova star compresses during collapse and its magnetic field increases considerably. The variable magnetic field will accelerate the charged particle, which generate radiation when moving in the magnetic field. The particles dynamics and their non-thermal emission in the magnetospheres of presupernova collapsing star with initial dipole magnetic fields and a certain initial energy distribution of charged particles in a magnetosphere are considered. The radiation flux depend on the distance to the star, its magnetic field, and the particle spectrum in the magnetosphere. This flux can be observed by means of modern instruments in broad band (from radio waves to gamma rays). The radiation flux grows with decreasing stellar radius and frequency and can be observed in the form of radiation bursts with duration equal to the stellar collapse time.

Particle dynamics in magnetosphere with variable dipole magnetic fields

The particle acceleration and their non-thermal emission in the magnetospheres of celestial body with the variable dipole magnetic fields and a certain initial energy distribution of charged particles in a magnetosphere (power-series, relativistic Maxwell, and Boltzmann distributions) are considered. The cyclic electric field produced in these magnetospheres will accelerate of charged particles till relativistic energy. These particles will generate radiation when moving in the magnetic field. Thus the celestial body with variable dipole magnetic fields can be powerful sources of non-thermal radiation. The effect can be observed by means of modern instruments. The radiation flux grows with decreasing body radius and can be observed in the form of the pulse radiation. The flux depends on the distance to the source, its magnetic field, and the particle spectrum in the magnetosphere.

Electro-Static Energy Analyzer with Elliptical Electrode.

The design of electrostatic energy analyzer for charged particles is described in this paper. A program for potential calculation including space charge is used here. The results show that the energy distribution of charged particles can be obtained with good resolution (about 1%) by the combination of elliptical electrodes. This analyzer has a wide angular aperture, thus the high throughput is expected. Also, it can resolve the particleenergy; therefore it can be applied to the short pulse beam measurement like ion scattering spectroscopy (ISS). In conclusion, this analyzer described here will be one of hopeful energy distribution measurements of charged particles like Cylindrical Mirror Analysis (CMA).

Particle Acceleration and Radiation in Magnetospheres of Collapsing Stars

Particle dynamics and nonthermal emission therefrom in the magnetospheres of collapsing stars with initial dipole magnetic fields and a certain initial energy distribution of charged particles (power-law, relativistic Maxwell, and Boltzmann distributions) are considered. The radiation fluxes are calculated for various collapsing stars with initial dipole magnetic fields and an initial power-law particle energy distribution in the magnetosphere. The effects can be observed by means of modern instruments.

Electromagnetic radiation from collapsing stars -- I. The power-series distribution of particles in magnetospheres

This is the first paper in a series in which the dynamics and non-thermal emission of particles in the magnetospheres of collapsing stars, with initial dipole magnetic fields and a particular initial energy distribution of charged particles in the magnetosphere (power-series, relativistic Maxwell and Boltzmann distributions), are considered. When the star magnetosphere compresses during collapse, its magnetic field increases considerably. The cyclic electric field thus produced involves acceleration of charged particles, which generate radiation when moving in the magnetic field. The analysis of particle dynamics and particle emission in the stellar magnetosphere under collapse shows that collapsing stars can be powerful sources of non-thermal radiation, produced by the interaction of charged particles with the magnetic field. The effect can be observed by means of modern instruments. The radiation flux grows with decreasing stellar radius and frequency and can be observed in the form of a radiation pulse with duration equal to the stellar collapse time. This flux depends on the distance to the star, its magnetic field and the particle spectrum in the magnetosphere. In this paper the radiation fluxes are calculated for various collapsing stars with initial dipole magnetic fields and an initial power-series particle energy distribution in the magnetosphere.

Analytical solutions for the energy distribution of charged particles in a weak electric field

The paper deals with the stationary distribution of charged particles moving in a material medium, having scattering and absorption properties, in which a uniform electric field is present. The purpose of the work is finding analytical solutions in simplified but physically significant situations and comparing different approximations based on a spherical-harmonics expansion of the velocity distribution.

Self-consistent modelling of plasma-solid interaction

In the paper the transport of electrons and ions in plasma is studied by computer simulation. The main goal of the modelling was to establish an exact form of energy distributions of charged particles near the metal substrates immersed into plasma and to analyse changes in their distributions during the transport through both the presheath and the sheath for various voltage biases and substrate geometries. Further results concern the probe characteristics both in inert gas and chemically active plasma and the distribution of potential and space charge in the vicinity of metal electrodes. As a simulation technique the combination of molecular dynamics and Monte Carlo methods was used. The movement of charged particles in self-consistent electric field was studied under the assumption of internal symmetry of the problem, which enabled to reduce the number of necessary coordinates to four (either 1d3v or 2d2v).

Angular anisotropy of charged particles evaporated from deformed nuclei

A semiclassical technique is developed for calculating the angular and energy distributions of charged particles evaporated from deformed nuclei. It includes an analytical expression for particle momentum at infinity via its momentum at the emission point, which reasonably reproduces exact calculations, and a triangular weighting function for averaging over the cascade temperature. Essential reduction in computational effort is achieved due to a compact expression for emission widths and a phenomenological treatment of penetration through an aspherical barrier. The application of this technique to alpha -emission from strongly excited Yb isotopes with aligned spin has produced values of the deformation parameter which are in good agreement with liquid drop model calculations.

Threshold and Energy Distribution for ECR Discharge Plasma Source

An ECR discharge plasma source obtained through the use of ferrite magnets was studied especially focusing on the threshold electric field at the breakdown and the energy distribution of charged particles in the plasma produced. The microwave frequency was a little smaller than the electron cyclotron frequency by about 0.5∼1%, which was explained clearly by the electron trapping condition. The energy distribution of electrons has the second harmonic and strongly depends on the localizing of the microwave field.

Collision of fast charged particles in solids

This book contains the following chapters: The transport equation of charged particles in matter; Elastic scattering of fast charged particles; Solution of transport equations for inelastic collisions; Angular and energy distributions of charged particles; Backscattering of charged particles from a continuous medium; Orientation effects in the coherent scattering of charged particles in single crystals; Channeling of charged particles in single crystals; Orientational phenomena in radiation of charged particles in single crystals; and Changes in the properties of matter in the particle track.

A Space-Borne Plasma Analyser for Three-Dimensional Measurements of the Velocity Distribution

A new type of plasma analyser, capable of covering the three-dimensional energy distribution of charged particles from a spinning spacecraft, has been built for the AMPTE and GIOTTO spacecraft. The novel features are the use of 260° of deflection in a spherical plate electrostatic analyser to obtain energy discrimination simultaneously with dispersion in angle and the use of a microchannel plate with position-sensitive readout to obtain the angular distribution. The sensor achieves a field of view greater than 140°; a well-defined and nearly-ideal shape for the acceptance volume in velocity space and a relatively large geometric factor.

Focusing deflection by flexible curved solenoid coil

AbstractThe so‐called “drift” of a charged particle annexed to the movement along the magnetic flux lines in a curved coil could be compensated by bending the coil in a letter “S” form (S‐type coil) or by superposing vertically the electrostatic fields to the magnetic fields.For an S‐type coil, when an electron beam accelerated at 2.5 kV was injected into the center of the coil, the focused beam was extracted through the center of the exit plane of the coil. Here, the height of the coil, the horizontal distance between the incident and the exit planes, and the strength of the magnetic fields were 225 mm, 60 mm, and 6.1 × 10−3 T, respectively. In this case, since the exit plane could be moved freely parallel to the incident plane, the focused beam was extracted according to the movement of the exit plane of the coil.Further, when the electric fields produced by a cylindrical static deflector were superimposed vertically to the magnetic fields in the coil with bending angle 90°, a focused beam without any drift was also obtained from the center of the exit plane.Therefore, this focusing deflection system will be available to transport the charged beam or to analyze the energy distribution of charged particles.

Angular and energy distributions of charged particles in electron-photon cascades in air

Monte-Carlo simulations of the development of 100 GeV photon-initiated cascades in the atmosphere have been used to predict the energy spectra and angular distributions of charged particles in electron-photon showers as a function of shower age. The lateral spread of the particles and their spread in time were also studied, in rather less detail, and a track length integral which measures the angular deflections produced by a magnetic field is given. Approximate formulae are given to describe these distributions. Particles of energy below about 15 MeV are not included in the distributions, as the main intended application is to the study of Cerenkov radiation from cosmic-ray showers, although particles were actually followed down to 0.05 MeV.

The interaction of atomic particles with solid surfaces at intermediate energies II. Scattering processes

Measurements were made of the energy distributions of charged particles emitted from targets of platinum, nickel and molybdenum bombarded by atomic and molecular positive ions of hydrogen, deuterium , helium , carbon, nitrogen, oxygen, neon, argon and carbondioxide, with energy 2 to 40 keV. It is shown that the scattering of incident particles is predominantly elastic and approximately independent of the charge state of the incident particle. Hydrogen, deuterium, carbon and oxygen are scattered with both positive and negative charges, but CO2gives only negatively charged scattered particles. Scattering with positive charge increases over an energy range 2 to 15 keV per incident particle, while scattering with negative charge increases to a maximum at incident energies 3 to 7 keV per particle and then decreases up to the highest energies used, 40 keV. Scattering with positive and negative charges is of the same magnitude at the incident energy corresponding with the maximum for negative scattering of hydrogen ions. The energy distribution of negatively charged scattered ions is generally broader than that for positively charged scattered ions at the same incident energy, for the lighter ions. Scattering as neutral atoms is estimated roughly and is shown to increase rapidly as the bombarding energy is reduced below about 10 keV.