Particle Identification Methods Research Articles

Track etch rate characteristics of makrofol polycarbonate plastic detector exposed to xenon ions

Abstract Track etch rate characteristics of makrofol polycarbonate plastic detector exposed to 54 Xe 129 heavy ions of 7.5 MeV/n energy at GSI, Darmstadt have been investigated. It is observed that the bulk etching rate, V b , as well as track etching rate, V t , by keeping the concentration of the etchant (6.25N NaOH) constant, increase with the increase of etching temperature. Complete etching times have been found to be 32, 15, 9 minutes at etching temperatures of 50°C, 60°C and 65°C, respectively. The activation energies for bulk etching and track etching are determined to be 0.9 eV and 1.38 eV, respectively. The etching efficiency (η) has been found to be independent of the etching temperature. The threshold value of energy loss rate of makrofol polycarbonate has been determined from a semi-empirical relation between V t , V b and REL, and has been found to be 4.29 MeV mg -1 cm -2 . The suitability of single sheet charged particle identification method has been examined. Using this method, makrofol detector has been found to quite suitable for identifying low energy Xe ions.

A new possibility for high-resolution spectroscopy of nuclear particles entering CR-39 at selected dip angles

In nuclear reaction studies a differentiation of the reaction products according to their type and energy is generally required. At right angle of incidence a particle identification method based on the relation netween the track diameter and particle energy can be well applied to plastic track detectors of low registration sensitivity. We have tried to extend this “track-diameter method” to the high-sensitivity CR-39 sheets by selecting special incident angles for particle detection. The utility of such a measuring procedure, called “track-size method”, is presented for alpha and proton spectroscopy. A theory is developed to calculate at arbitrary angles the main parameters affecting the energy resolving power of the “track-size method”, namely the critical layer thickness (which has to be removed from the detector surface for track-induction) and the depth and minor axis of etch-pits.

Particle identification through the measurement of the Bragg curve centroid

A new method of particle identification of heavy ions through the measurement of the Bragg curve centroid and particle energy has been developed using a gas ionization chamber with a resistive anode layer. Z-resolutions comparable to the conventional ΔE-E counter telescope could be rather easily attained.

Track record in meteorites

Over geological time, meteoritical crystals have accumulated a record of tracks produced by heavily charged energetic particles from both internal and external sources, such as fissile nuclei and cosmic rays with Z >20. The paper highlights some of the areas where the track analysis method has made significant, and sometimes unique, contributions to our knowledge, not only of the history of meteorites but also of conditions prevailing in our Solar System from soon after the end of nucleosynthesis ( ca . 4.6 Ga ago) until the present day. The topics covered include the following, (i) Fission-track retention ages and cooling rates of meteoritic parent bodies. Ages range downwards from ca . 4.55 Ga, depending on the type of crystal and the time at which different crystals had cooled down sufficiently to retain tracks; typical early cooling rates are (a few times) 1 to 10 K Ma -1 . (ii) Charge and energy spectra of ancient cosmic rays in comparison with contemporary values. Methods of particle identification are described; no significant differences from Solar System abundances or contemporary cosmic rays are found for the v.h. (very heavy; Z « 20-28) and v.v.h. (very very heavy; Z > 30) nuclei, (iii) Determination of pre-atmospheric sizes of meteorites by fitting measured track-density values as a function of depth below a fusion crust to theoretical curves for track-production rate as a function of true pre-ablation depth. (iv) Search for superheavy elements (s.h.e.) in meteorites. By examining the silicate minerals at boundaries with metal in iron and stony-iron meteorites, where large amounts of excess tracks from the fission decay of siderophile superheavy elements should have been recorded in the silicate interface but are not found, upper limits ranging from ca. 1 fg g -1 to ca . 1 pg g -1 at fission-track retention time ( ca . 4.2 Ga ago) can be placed on the superheavy element content.

Detection of far-ultraviolet photons with the multistep avalanche chamber. Application to Cherenkov light imaging and to some problems in high-energy physics

We have designed and operated a multistep avalanche chamber capable of detecting single photons in the vacuum ultraviolet wavelenght (130–160 nm). The device has been used to image photons generated from charged particles by Cherenkov effect in solid an gaseous radiators, and providing a ring pattern with a radius related to the particle's velocity; experimental values are given for the angle and velocity resolution obtained. Possible applications of the method for particle identification are discussed.

An observation on the spatial distribution of vacuum UV photons generated by Cherenkov radiation

We report the observation of photoelectrons from vacuum UV photons in a multiwire proportional chamber (MWPC). This gave a one-dimensional projection of the ring image obtained for Cherenkov radiation from 1.2GeV/ c electrons. The measurement of such ring images would give a powerful method of particle identification in high energy experiments.

Differential Energy Spectra of Low-Energy (<8.5 MeV per Nucleon) Heavy Cosmic Rays during Solar Quiet Times

Explorer 47 satellite observations of carbon, oxygen, and heavier nuclei differential energy spectra below 8.5 MeV/nucleon are presented for solar quiet time periods. A dE/dx vs E method for particle identification and energy determination was used. The instrumentation telescope included an isobutane proportional counter, a surface barrier Si detector, and a cylindrical plastic scintillator anticoincidence shield. The observations were performed outside the bow-shock and in the ecliptic plane. Results show an anisotropy of about 25% at 22 degrees west of the sun with a C/O ratio of 0.5 supporting a solar origin. The low energy portions of the C and O spectra have steep negative slopes, and the corresponding power law is given. Peculiarities in the O spectrum are discussed.

A new method for particle identification on light nuclear charged particles by means of a solid-state track detector

A new method is presented for particle identification and energy measurement on light nuclear charged particles by means of a solid-state track detector. The principle and the concrete method of particle identification are given with theoretical calculations. This method is applicable in the energy region from about 0.5 MeV per nucleon up to about critical energy for the particles with the atomic number z ⪅ 20.

Detection of low-intensity alpha decay branches with semiconductor detectors

The detection limit for low-intensity α-transitions with semiconductor detectors may be lowered to 10 −4% of the total transition rate, using particle identification methods.

The NRL-Isochronous Cyclotron Multi-User On-Line Data Acquisition System

The operating features of the SOPHYA (Supervisor of Physics Analysis) system as implemented for an EMR Advance Series 6050 computer at the Naval Research Laboratory's Isochronous Cyclotron are explained. Several independent experiments may be run concurrently with additional capability for a batch processing shadow time job. Each experimenter has acceses to the full library of general routines. The special purpose routines may be coded in Fortran or Assembly Language and included in the library. Standard package includes MATRIX SLICE routines, CRT display routines for single parameter and two parameter contour map or isometric display. Light pen control allows such operations as background subtraction, rotation of axes, etc. A digital method of particle identification is discussed in which an algorithm for evaluation of an identification constant is computed in realtime.

A diode function generator for identification of charged particles

A simple, low cost diode function generator for identifying charged particles with different mass and/or charge, is described. The circuit is capable of handling input pulses as narrow as 0.5 μsec. The accuracy of a function approximation of 0.5% with good stability and reliability can be obtained. The possibilities of the application of this circuit for different methods of particle identification are discussed.

Pulse-shape discrimination method for particle identification

A new electronic method for pulse shape discrimination is described, and this method was applied for identification of various charged particles. By using a single crystal scintillation spectrometer with CsI(Tl) crystal the variation of the fluorescent decay time with the alpha and proton energy is presented.

Survey of (p, d) Reactions at 22 Mev

Energy spectra of deuterons from (p,d) reactions on medium and heavy weight elements were surveyed. The experimental method of particle identification is described. The spectra show gross structure indicative of strong selection rules. The gross structure can be correlated with nuclear shell structure, and the levels which are most strongly excited are those which have the same shell configurations as the target with one neutron missing. Angular distributions confirm the shell assignments. This leads to a picture of the reaction mechanism for (p,d) reactions in which the incoming proton interacts principally with a single neutron rather than with the nucleus as a whole. (auth)

PARTICLE IDENTIFICATION IN PHOTOGRAPHIC EMULSIONS BY THE DELTA-RAY METHOD

A comparison is made in this study between the δ-ray densities expected theoretically and those observed experimentally on charged particle tracks in Ilford G5 emulsions. The energies of δ-rays are determined here by means of grain-counting measurements and energy-loss considerations. Using this method of energy determination and the theoretical formula for δ-ray density, good agreement has been found with the experimental distributions on proton, μ-meson, deuteron, and α-particle tracks. The agreement is satisfactory both in absolute value and in the shape of the δ-ray density distribution. These results are considered to show that the δ-ray technique is suitable as an absolute method of charged particle identification in photographic emulsions.