Search

Energy spectra of protons and helium nuclei in primary cosmic rays were measured above 1 TeV in a series of balloon flights carrying emulsion chambers. Differential spectra may be represented by power laws of indices -2.81 + or - 0.13 and -2.83 + or - 0.20 for protons and He, respectively. No index change was observed for either species over the energy ranges 5-500 TeV for protons and 2-50 TeV/nucleon for He. Intensities were consistent with extrapolations of previously published data below 1 TeV/nucleon.

The instrumentation and results of long duration balloon flights carried out jointly by U.S. and Japan researchers to examine high energy cosmic rays are reported. Basic detector geometries are 2.5 sq m sr with operation at altitudes with 3-4 g/sq cm pressure, with observations thus far of over 100 hr. Energies from 2-100 TeV are recorded for nucleus-nucleus and hadron-nucleus interactions, and searches are made for new particle or interactions. The detector is an emulsion chamber which comprises doubly-coated nuclear emulsions on 800 micron thick methacryl substrates, X-ray films, etchable detectors, low density spacers, and lead sheets. Segmentation of the instrument into a primary charge module, a target section, a spacer section, and a lead-emulsion calorimeter allows accurate charge measurement for primary nuclei, reliable energy resolution, and a large geometrical factor for collecting high energy events. A primary Ca nucleus of 300 TeV has been observed.

The inelastic-interaction mean free paths (lambda) of 5-, 10-, and 15-GeV/c pions have been measured by determining the distribution of first-interaction locations in a modular tungsten-scintillator ionization spectrometer. In addition to commonly used interaction signatures of a few (2-5) particles in two or three consecutive modules, a chi-squared distribution is employed to calculate the probability that the first interaction occurred at a specific depth in the spectrometer. This latter technique seems to be more reliable than use of the simpler criteria. No significant dependence of lambda on energy has been observed. In tungsten, lambda for pions is 206 (plus or minus 6) g/sq cm.

Electromagnetic cascades in a lead-emulsion chamber have been studied to determine the effect of air gaps on the upstream sides of the emulsions. Such air gaps cause a change in the form of the radial distribution of electron tracks, making cascades appear older and giving incorrect energy estimates. The number of tracks remaining within a radius r was found to vary as exp(-g/G), where g is the gap thickness. The characteristic gap thickness in mm is G = 3.04 + 1.30 ln (Err per GeV per sq mm) where E is the energy of the initiating gamma ray. Use of this relation provides a significant correction to cascade-energy estimates and allows one to calculate the effect of different gap thicknesses on the energy threshold for visual detection of cascades.

A search has been carried out for a long-lived particle having an interaction length lambda sub m equals 300 to 2000 gm/sq cm in air. Such a particle, called the mandela, has been proposed to explain an anomalous energy spectrum of particles observed near sea level with a shallow spectrometer. Data taken at mountain altitude with a deep spectrometer has been examined for compatibility with the existence of the mandela. Although data tend to favor the mandela hypothesis the results are not conclusive and appear to be explainable by conventional means.

The response of a tungsten-scintillator ionization spectrometer to accelerated particle beams has been investigated. Results obtained from exposure of the approx. 1000 g/sq cm apparatus to 5, 10, and 15 GeV/c electrons and pions as well as to 2.1 GeV/nucleon C-12 and O-16 ions are presented. These results include cascade-development curves, fractions of the primary energy measured by the spectrometer, and resolutions of the apparatus for measuring the primary energies. For 15 GeV/c electrons, an average of about 82% of the incident energy is measured by the apparatus with resolution (normal standard deviation) of about 6%. For 15 GeV/c pions, an average of about 65% of the incident energy is measured with resolution of about 18%. The energy resolution improves with increasing energy and with increasing depth of the spectrometer.

Measurement of the total fragmentation cross sections of C-12 and O-16 ions incident in CsI target and tungsten scintillator modules. The analysis described is based on a one-module criterion for determining the location of an interaction. The results are independent of the windows used, provided that corrections are made for interactions simulated by energy loss fluctuations in the individual modules and for Delta Z ? 1 interactions missed because of the use of wide windows. The cross sections obtained are in general agreement with the values obtained in other experiments for various target nuclei.

Light produced by nuclear-electromagnetic cascades in a plastic scintillator can be photographed, and the resulting images on film used to measure both the energy content of the cascades and also the positions at which the cascades passed through the scintillator. The energy content of a cascade can be measured to 20% and its position determined to plus or minus 0.8 cm in each scintillator. Techniques for photographing the cascades and analyzing the film are described. Sample data are presented and discussed.

Cosmic ray nuclear interactions in 10-300 GeV energy range, using balloon-borne emulsion target, spark chambers and ionization spectrometer

A method is proposed for obtaining the energies of high-energy hadrons incident upon a glass-scintillator ionization spectrometer. The description of the apparatus and of its calibration with cosmic ray muons is followed by a demonstration of the processing of the data obtained.

Design of experiments and systems for HEAO to determine composition and spectra of high energy cosmic rays

The longitudinal development of nuclear-electromagnetic cascades with energies greater than 200 GeV was measured in a low-Z (glass) absorber. This was done in the course of operating an ionization spectrometer at mountain altitude in an experiment to study the properties of gamma rays emitted from individual interactions at energies around 10,000 GeV. The ionization produced by a cascade is sampled by 20 sheets of plastic scintillator spaced uniformly in depth every 2.2 radiation lengths. Adjacent pairs of scintillators are viewed by photomultipliers which measure the mean ionization produced by an individual cascade in 10 layers each 1.1 interaction length (4.4 radiation lengths) thick. The longitudinal development of the cascades was measured for about 250 cascades having energies ranging from 200 GeV to 2500 GeV. The observations are compared with the predictions of calculations made for this specific spectrometer using a three-dimensional Monte Carlo model of the nuclear-electromagnetic cascade.

Image intensifier apparatus photographing nuclear electromagnetic cascades in ionization spectrometer

Properties of ionization spectrometer exposed to 10, 20.5, and 28 GeV/c synchrotron accelerated protons

Ionization spectrometer for hadron energy measurement, analyzing instrument accuracy by Monte Carlo model for nuclear-EM cascade in iron absorber

Gamma ray emission from individual interactions of hadrons in carbon at 10 TeV, using ionization spectrometer-emulsion chamber combination

Image intensifier photography of simulated cosmic ray shower development within ionization calorimeter containing large sheets of plastic scintillator