Angular Distributions Of Charged Particles Research Articles

Approach for simultaneous measurement of two-dimensional angular distribution of charged particles: Spherical aberration correction using an ellipsoidal mesh

An approach for simultaneous measurement of two-dimensional angular distribution of charged particles is proposed. This concerns spherical aberration correction in electrostatic lenses with potential use of a mesh. In an earlier work, an effective use of a spherical mesh has succeeded to obtain a large acceptance angle limited to around 60 degrees (+/- 30 degrees). The present work is aimed at dramatically increasing acceptance angles limited in conventional lenses. For this purpose, spherical aberration behavior of mesh lenses is studied in detail using an analytical approximation and ray tracing, with particular attention paid to the effect of the mesh shape. It is shown here that the lens ability to correct spherical aberration over wide aperture angles can be effectively enhanced by the ellipsoidal deformation of a spherical mesh. We demonstrate that an effective use of an ellipsoidal mesh provides remarkable performance characteristics for electrostatic lenses, which opens new possibilities in surface and materials analysis techniques. Simple examples of ellipsoidal mesh lenses are presented that allow very wide acceptance angles of up to 120 degrees.

Erraticity analysis of multiparticle production in nucleus-nucleus interactions at relativistic energies

Nonstatistical fluctuation in the angular distribution of charged particles produced in high-energy nucleus-nucleus interactions is investigated by using the technique of erraticity moments. Nuclear photographic emulsion data on secondary shower track emissions collected from $^{16}\mathrm{O}$-Ag/Br and $^{32}\mathrm{S}$-Ag/Br interactions, each at an incident momentum of 200 A GeV/c, are analyzed. A generalized scaling law between the erraticity moments and the phase-space partition number is established for both sets of data. Experimental values of erraticity parameters are compared with those obtained from event samples generated by the Lund Monte Carlo model FRITIOF and by simple random numbers. In each case simulated results substantially underestimate the extent of experimentally observed nonstatistical fluctuation.

Charged particle multiplicity in Pb-Pb collisions from the NA50 experiment

Angular distributions of charged particles produced in Pb-Pb collisions at the CERN SPS have been measured by the NA50 experiment. Measurements have been performed with a silicon microstrip detector at two different beam energies (40 and 158 GeV/nucleon) and over a wide impact parameter (centrality) range. The centrality of the collision has been evaluated both by neutral transverse energy released in the interaction and by spectator nucleons energy (zero degree energy).The charged particle density at midrapidity shows a linear dependence on the number of participating nucleons at both beam energies. The particle density per participant pair and its √S dependence are also studied.

HPGe detectors for low-temperature nuclear orientation

Using the Low-Temperature Nuclear Orientation (LTNO) technique one can study various interesting properties of atomic nuclei and nuclear decay which can be deduced from the measurements of the angular distributions of charged particles emitted during the decay. However, the use of particle detectors working in conditions of LTNO devices (which are generally not available commercially) is a necessary precondition for the realization of these experiments.Planar HPGe detectors for detection of charged particles at “liquid helium” temperatures were developed and produced at NPI Řež. Relatively simple technology using vacuum evaporation and diffusion was employed. The performance of detectors at low temperatures was tested and their characteristics measured in a testing cryostat before using them in real experiments.The HPGe detectors were extensively used in a whole range of LTNO experiments with various physical objectives — in offline (IKS Leuven) as well as online (CERN-ISOLDE, Louvain-la-Neuve — LISOL) experiments. In frame of the project “Meson-Exchange Enhancement of First-Forbidden Beta Transitions in the Lead Region”, the measurements of angular distribution of emitted β-particles allowed to determine experimentally the “meson-exchange currents” contribution to the β-decay. In the project “Isospin Mixing in N∼Z nuclei”, the isospin-forbidden β-transitions of the nuclei in region (A=50–100) were studied in order to obtain information on the isospin structure of the nuclear states. A new project looking for the possible presence of the tensor currents contribution to the β-decay is being prepared for the CERN-ISOLDE facility.

Iron-cored coil system for the measurement of angular distributions of charged particles

A novel coil system is described that enables the magnetic angle-changing technique to be used at higher energies. The system consists of coils of wire that are combined with specially shaped iron cores in such a way as to preserve localization of the magnetic field. The system extends the operational energy range of previous systems consisting of solenoids alone by a factor of 25. Measurements of the electron impact excitation of the n=2 states of helium are presented as an example of the use of the device.

Nucleus-nucleus collision as superposition of nucleon-nucleus collisions

Angular distributions of charged particles produced in 16O and 32S collisions with nuclear track emulsion were studied at momenta 4.5 and 200 A GeV/c. Comparison with the angular distributions of charged particles produced in proton-nucleus collisions at the same momentum allows to draw the conclusion, that the angular distributions in nucleus-nucleus collisions can be seen as superposition of the angular distributions in nucleon-nucleus collisions taken at the same impact parameter b NA , that is mean impact parameter between the participating projectile nucleons and the center of the target nucleus

An analysing system for concurrent energy and angular distribution measurements of charged particles' emission

A theoretical treatment of an electron-optical scheme is suggested. The system can be used for simultaneous registration of energy and angular distributions of charged particles (electrons or ions) emitted from a small source. The scheme is based on an axially calculated symmetrical electrostatic field. The source has the form of a short interval of the axis of symmetry. The system consists of a novel type of electrostatic energy analyser and an usual planar position-sensitive detector joined to it.

A measurement of charged particles accompanying high-energy muons exiting matter

Using a high-energy muon beam at Fermilab, we have made measurements of frequency, multiplicity, spatial and angular distributions of charged particles accompanying muons after they have traversed an iron absorber. Effects of several other materials (Al, Pb, G-10, Lucite) placed at various locations downstream of the absorber were also studied. Measurements were made at muon beam energies 94, 360, 480 and 560 GeV. Experimental data are compared to GEANT 3.21 Monte-Carlo simulations. GEANT parameter settings for matching the experimental data are investigated.

SLOW TARGET-ASSOCIATED PARTICLE PRODUCTION IN 6Li-Em COLLISIONS AT 4.5 A GeV/c

The multiplicity and angular distributions of charged particles with velocities smaller than 0.7c produces in 6 Li-Em collisions at 4.5 A GeV/c. The multiplicity distribution is independent of the energy of the projectile or its mass. The Ng multiplicity distributions are fitted with a parameter free model whose input information is the Ng multiplicity distribution produced in proton induced reactions.

Measurement of the angular distributions of particles in air showers.

Using a scintillator air shower array to determine the direction, size, and core position of extensive air showers and a large-volume drift chamber to track individual shower particles, we have measured the angular distributions of charged particles in extensive air showers at sea level. The distributions are sharply peaked around the shower axis, with characteristic widths of a few degrees. Particles at large distances from the shower axis tend to point towards the axis as their origin. Monte Carlo models of air showers reproduce the measured distributions rather well.

New effects in the angular distribution of charged particles in crystals

Abstract The possibility of increasing angular density of charged and neutral particle beams using different scattering rates of particles with different angles of incidence is discussed. The experimental evidence of this increase is presented. The possibility to intensify the effect by its successive use in different crystals is discussed.

Large solid angle detector for charged particles from photodisintegration of light nuclei

A large solid angle detector has been built for measurements of the angular distributions of charged particles in photodisintegration reactions. The detector consists of a three-layered, cylindrical, multiwire proportional chamber surrounded by eight ΔE- E plastic scintillator pairs. The detector is described, along with its performance in two photodisintegration experiments and its calibration in a measurement of proton scattering from hydrogen.

Erratum: New display-type analyzer for the energy and the angular distribution of charged particles [Rev. Sci. Instrum. 5 9, 545 (1988)

First Page

New display-type analyzer for the energy and the angular distribution of charged particles

A new principle for analyzing the kinetic energy as well as the angular distribution of charged particles has been discovered. A new display type analyzer was constructed according to theory. It consists of an inner hemispherical grid and an outer hemispherical electrode which has a radius two times larger than that of the inner grid. Charged particles with the same kinetic energy radiate from one point to all directions inside the inner grid, are repelled by the electric field between the two spheres, and converge at the point which is symmetric to the center of the hemispheres. When an aperture is put at the point, the angular distribution of the charged particles can be observed using a two-dimensional detector which is positioned out of the aperture. The characteristics of the analyzer are (1) the acceptance cone is ultimately wide, for instance, 2π sr for the charged particles emitted from a flat surface, (2) the pattern obtained is not distorted, and (3) the two electrodes are very simple and easy to construct.

Multiplicity and angular distributions of charged particles in interactions of 56Fe in emulsion at 2.5A GeV/c

Data are presented on multiplicity and angular distributions of charged secondary particles from inelastic interactions of 56Fe in emulsion at 2.5A GeV/c. Comparisons with data, at nearby the same incident momentum per nucleon from p-A, 14N-A, 16O-A and 40Ar-A collisions are performed in order to trace the dependence on projectile and target mass. Furthermore, the 56Fe data are compared with the results from a cascade-evaporation model. This comparison shows some significant deviations between the model and the data which are not observed for light ion induced collisions.

Charged-particle multiplicity and angular distributions in proton-emulsion interactions at 800 GeV.

The interaction of 800-GeV protons in nuclear emulsion has been investigated. The multiplicities and angular distributions of charged particles emitted by both the projectile and the target nucleus have been measured for 1718 inelastic events and are compared with the data obtained in proton-emulsion collisions at 67, 200, and 400 GeV. The target excitation is found to be independent of energy while the production of secondary particles continues to increase with incident proton energy.

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.

Angle resolved detection of charged particles with a novel type toroidal electrostatic analyser

Abstract A novel type of toroidal electrostatic energy analyser is described with position sensitive detection of the particles passing the exit slit of the analyser, different positions corresponding to different scattering angles. The angular distribution of charged particles' in a 20° angular range can be measured simultaneously with energy resolution ΔE/E = 4 × 10-3, angular resolution 0.2° and under ultra-high vacuum conditions.

The bidirectional particle event of October 12, 1977, possibly associated with a magnetic loop

A fortuitous set of interplanetary and solar events which occured on October 12, 1977, allowed the observations by several interplanetary spacecraft, IMP 7 and 8, of features in charged particle angular distributions which suggest the presence of a closed magnetic loop. This loop must have extended beyond the orbit of earth and have been connected to particle sources and/or mirrors at both ends. This magnetic topology is similar to a suggestion made by Gold (1960). The salient feature of the anisotropies which calls attention to the possible presence of a loop is the occurrence of a trapping‐type electron distribution peaked at 90° to the magnetic field, while the ions are strongly field aligned and bidirectional.

Application of a multiwire proportional chamber for the measurement of differential (n, charged particle) cross sections

A new method for the measurement of energy and angular distributions of charged particles from neutron induced nuclear reactions is described. A small cylindrical multiwire proportional chamber in connection with a central CsI(T1) scintillator allows simultaneously the measurement of the energy of charged particles at all reaction angles, the particle identification via the d E/d X- E detector system and via pulse shape discrimination, and the measurement of the background, thus reducing accelerator and measuring time. Data acquisition is made on-line via CAMAC to a PDP-11 computer. The design of the system and its performance under realistic measuring conditions are described in detail.