A transition radiation detector for electron identification in a high energy experiment

We have built a transition radiation detector consisting of four sets of multilayered polyethylene radiators each followed by a xenon-filled proportional chamber. This detector has been used in a hadron-proton scattering experiment at CERN SPS to discriminate electrons from hadrons in the final state. Using the technique of recording chamber signals of amplitude exceeding a fixed threshold we normally achieved 0.5% pion contamination at 80% electron efficiency.     

The design of a portable cosmic ray three-band neutron detector

The design of a portable three-band cosmic-ray neutron detector is reported in this article. This instrument has been designed to characterise cosmic ray neutron fields in the upper atmosphere and in cosmic reference field facilities. The design utilises a spherical moderator with a layer of spallation material covering a central (3)He proportional counter. The instrument incorporates twelve lithium-coated diodes, six on the outside of the polyethylene layer and six placed within the structure. The dimensions, materials and arrangement of these in the instrument have been optimised with MCNPX to provide a compromise between the requirements of portability and spectral response.     

Contribution of cosmic ray heavy ions to the radiation hazard in manned space flights

Primary cosmic radiation arriving near the Earth may be classified into two general categories: the gamma component and the hadronic component. The hadronic component contains mainly protons, a small amount of alpha particles and a smaller amount of heavier charged nuclei (ions). Although the fluxes of these heavier ions are very small in comparison to those of protons, they are able to originate a huge linear energy transfer (LET). This work studies the contribution of heavy ions from cosmic rays to the radiation hazard to which the crew of a manned long duration space flight might be exposed. The geometry of the energy deposition by a heavy ion is studied, and it is found that energies of the order of up to 10(23) J kg-1 are deposited.     

Propagation of Cherenkov radiation of cosmic ray particles through water

The spatial distribution of Cherenkov radiation emitted by a relativistic muon passing through the water is calculated by the Monte Carlo method. The absorption and scattering of photons in the medium are taken into account. Analytical expressions are obtained for asymptotically large distances from the particle trajectory to the detector.     

A neural network for positron identification by transition radiation detector

A neural network algorithm has been applied in order to distinguish positrons from protons by a transition radiation detector (TRD). New variables are introduced, that simultaneously take into account spatial and energy TRD information. This method is found to be better than the one based on classical analysis: the results improve the detector performance in particle identification for efficiency higher than 90%. The high accuracy achieved with this method is used to identify positrons versus protons with 3 × 10⁻³ contamination, as required by TRAMP-SI cosmic ray space experiment on the NASA Balloon-Borne Magnet Facility.     

Front end electronics and cosmic ray tests of muon drift tubes for the SDC detector

A system of front end wire chamber electronics for a large scale array of muon drift tubes is described. Simulations of the tube performance with readout electronics are discussed and compared with cosmic ray measurements.     

HETC radiation transport code development for cosmic ray shielding applications in space

In order to facilitate three-dimensional analyses of space radiation shielding scenarios for future space missions, the Monte Carlo radiation transport code HETC is being extended to include transport of energetic heavy ions, such as are found in the galactic cosmic ray spectrum in space. Recently, an event generator capable of providing nuclear interaction data for use in HETC was developed and incorporated into the code. The event generator predicts the interaction product yields and production angles and energies using nuclear models and Monte Carlo techniques. Testing and validation of the extended transport code has begun. In this work, the current status of code modifications, which enable energetic heavy ions and their nuclear reaction products to be transported through thick shielding, are described. Also, initial results of code testing against available laboratory beam data for energetic heavy ions interacting in thick targets are presented.     

Monte Carlo simulation of a transition radiation detector

This paper employs Monte Carlo simulations of the performance of a transition radiation detector (TRD). The program has been written for the TRD in the ZEUS spectrometer, which separates electrons from hadrons in the momentum range between 1 and 30 GeV/c. Both, total charge method and cluster counting method were simulated taking into account various experimental parameters. In particular, it was found that the cluster counting method relies on a quantitative understanding of the background originating from the production of δ-electrons by charged particles. The results of the Monte Carlo calculations are in agreement with experimental data obtained with prototypes within a systematic uncertainty of 20%. We applied our Monte Carlo program to studies in order to find an optimum layout for the TRD within available space in the ZEUS spectrometer. In this context, the performance of TRD layouts with different geometries and materials has been evaluated comprehensively. The geometry found by optimization promises an improvement on hadron suppression by a factor of about two for both methods compared with present results from test measurements. Applying algorithms for a detailed analysis of the energy and space distributions of the clusters in the TRD, hadrons in the momentum range from 1 to 30 GeV/c can be suppressed to a level of less than 2%. This method of cluster analysing improves the suppression of hadrons by a factor of about two compared to the total charge method.     

JACEE emulsion chambers for studying the energy spectra of high energy cosmic ray protons and helium

Emulsion chambers are being used in a series of stratospheric balloon flights to study nuclear interactions, charge composition, and energy spectra of cosmic ray nuclei over the energy range 10¹²–10¹⁵ eV. Charge identification involves grain, gap, and/or delta-ray counting in emulsion plates having different sensitivities on two sides of an acrylic base. Electromagnetic cascade energies are measured with resolutions of about 25% by the three-dimensional track counting method. This report describes the apparatus, the measurement techniques, and the analysis methods used to determine the primary proton and helium spectra.     

High energy gamma ray observatories for the study of cosmic ray electrons above 1014 eV

We have studied in detail the possibility of detecting cosmic ray electrons of energy ?10¹⁴ eV using high energy γ-ray detectors. Such instruments would detect synchrotron γ-rays radiated by the electrons, while traversing the Earth's magnetic field. These radiated γ-rays are expected to be incident along a straight line in the detector for an unambiguous identification of an electron event. Our analysis shows that small γ-ray detectors such as those in SAS-2 and COS-B satellites cannot be used for this purpose. The high energy γ-ray detector to be flown on the GRO satellite may be able to detect electrons, if the energy spectrum of electrons at high energies is modified by the influence of a nearby source. Such exciting possibilities can be observed with large area γ-ray instruments, which are aslo capable of detecting γ-rays through Compton scattered electrons. We have, in this investigation, suggested ways of utilizing future large area γ-ray observatories to open up a new avenue for the study of ultra high energy cosmic ray electrons.     

Linear energy transfer spectra of cosmic radiation aboard the Cosmos-1129 satellite

The most important characteristic of the hazard due to cosmic radiation is the spectrum of linear energy transfer (LET), which enables one to estimate the dose equivalent. This has prompted us to study LET spectra of cosmic radiation aboard Cosmos-1129 using nuclear emulsions as a threshold detector.     

A massive bolometer on the international space station to measure energy deposition by the space radiation environment

We describe a novel space-based low-temperature radiation detector, the “Particle Heating Detector” (PhD), which was recently selected to be part of the first mission of the Low-Temperature Microgravity Physics Facility, scheduled to fly on the International Space Station in 2008. This massive bolometer will measure total heating induced in an aluminum absorber by the space radiation environment. The use of paramagnetic alloy thermometers with SQUID readout, giving resolution, combined with a large-area absorber, will enable the detector to perform high-resolution, real-time measurement of the low energy deposition levels caused by galactic cosmic rays in low-Earth orbit.     

Holographic recording of cosmic ray tracks in BEBC

We report on a successful test of holography in the Big European Bubble Chamber (BEBC) at CERN, which was filled with a heavy neon—hydrogen mixture. During the test of a modified in-line scheme we photographed bubble tracks longer than 1 m, which were produced by cosmic rays. The smallest bubbles, which were recorded with excellent contrast, had a diameter of ? 120 μm. This presents an improved resolution of a factor of five compared to photos taken with conventional cameras.     

Simulation of the cosmic ray Moon shadow in the geomagnetic field

An accurate Monte Carlo simulation of the deficit of primary cosmic rays in the direction of the Moon has been developed to interpret the observations reported in the TeV energy region until now. Primary particles are propagated through the geomagnetic field in the Earth–Moon system. The algorithm is described and the contributions of the detector resolution and of the geomagnetic field are disentangled.     

A new method to detect gamma ray extensive air showers which directly measures angles and identifies muons

We describe an extensive air shower array (GRAND™) ⁷ which is currently under construction. It is dedicated to recording ultrahigh energy (UHE) gamma rays from stellar point sources by measuring the angle of charged secondaries with proportional wire chamber tracking detectors. This new method is designed to give 0.25° angular resolution for the primary gamma direction with 100 detected secondary electrons. These same tracking detectors make possible a new, inexpensive detector for muons thereby enabling the rejection of muon-rich hadronic shower background.     

A combined interpretation of cosmic ray light nuclei and antiproton measurements

Recently several experiments improved significantly our knowledge of cosmic ray (CR) spectra at high energy. In particular CREAM measured B/C, C/O and N/O ratios up to and PAMELA observed the antiproton-to-proton ratio up to with high accuracy. These results permit to put more stringent constraints on the free parameters involved in the diffusion-loss equation that describes the propagation of CRs in the Galaxy. To this purpose, we perform a new statistical analysis comparing updated experimental data with the predictions of an improved version of our numerical code DRAGON. We obtain well defined ranges of values for the diffusion coefficient normalization and index of the power-law dependence on rigidity as well as for the Alfvén velocity.     

FLUKA simulation of TEPC response to cosmic radiation

The aircrew exposure to cosmic radiation can be assessed by calculation with codes validated by measurements. However, the relationship between doses in the free atmosphere, as calculated by the codes and from results of measurements performed within the aircraft, is still unclear. The response of a tissue-equivalent proportional counter (TEPC) has already been simulated successfully by the Monte Carlo transport code FLUKA. Absorbed dose rate and ambient dose equivalent rate distributions as functions of lineal energy have been simulated for several reference sources and mixed radiation fields. The agreement between simulation and measurements has been well demonstrated. In order to evaluate the influence of aircraft structures on aircrew exposure assessment, the response of TEPC in the free atmosphere and on-board is now simulated. The calculated results are discussed and compared with other calculations and measurements.     

A selective pyroelectric detector of millimeter-wave radiation with an ultrathin resonant meta-absorber

The results of experimental investigations of spectral and amplitude-frequency characteristics for a discrete wavelength-selective pyroelectric detector operating in the millimetric band are presented. The high spectral selectivity is attained due to integrating the detector with a resonant meta-absorber designed for a close-to-unity absorptivity at 140 GHz. It is demonstrated that the use of this meta-absorber provides an opportunity to construct small-sized and inexpensive multispectral polarization-sensitive systems for radiation detection in the range of millimeter and submillimeter waves.