Articles written in Proceedings – Section A
Volume 38 Issue 5 November 1953 pp 418-439
A new method is developed for determining the mass of particles coming to rest in nuclear emulsions. Multiple coulomb scattering is measured with cells whose lengths vary along the trajectory in such a manner as to compensate for the momentum loss of the particle and keep the mean deviation between adjacent cells constant over the entire track. It is shown that this procedure is more convenient and inherently more accurate than that based on scattering measurements with constant cellsize. The method has been applied to
Volume 41 Issue 4 April 1955 pp 154-184
Small local dislocations in processed emulsions give rise to spurious scattering whose effect on tracks is indistinguishable from the multiple scattering produced by coulomb interaction. Because of this effect the atomic number of fast primary cosmic ray nuclei will be underestimated in more than 50% of the cases in experiments where multiple scattering of tracks and ionization measurements are employed for charge determination. The spurious scattering was investigated by measuring the track contours of 100 very long tracks due to energetic primary particles; the effect was present in comparable strength in all plates and all types of emulsions which have been investigated. It is too small to affect measurements on medium energy particle tracks (protons with energy below 600 MeV and heavy nuclei with energy below 300 MeV/ nucleon). It dominates, however, other sources or error and noise for tracks of energetic particles although it does not preclude occasional observations of very low scattering values. New methods for measuring various forms of noise have also been developed in the course of this work and the noise level for scattering measurements has been reduced below previously accepted values.
Spurious scattering is presumably largely responsible for the discrepancies which appear when one compares the primary charge and energy spectra derived from experiments involving scattering measurements with the corresponding spectra derived from numerous other experiments which employ different techniques.
If the experiments based on scattering measurements are omitted, the remaining evidence strongly favours a spectrum in which the energy per nucleon is nearly independent of atomic number for all primaries. It also favours a charge distribution which has a pronounced minimum for charges 3≤ Z≤ 5 and, therefore, yields a fairly low upper limit for the amount of interstellar matter traversed by primary cosmic ray nuclei.
Volume 46 Issue 2 August 1957 pp 167-181
Scattering measurements on individual tracks and relative scattering measurements on pairs of tracks have been made in two stacks exposed to 6·2 and 5·7 BeV protons respectively from the Berkeley Bevatron. Spurious scattering was determined in these two stacks for cell lengths ranging from 1 mm. to 8 mm. In one stack the magnitude of spurious scattering was very low while in the other it was fairly high. Our results indicate that:
Spurious scattering varies with cell length
The spurious scattering is lowest near the glass surface of the emulsion and increases towards the air surface.
The small-scale dislocations which give rise to spurious scattering extend in the plane of the emulsion at least over distances of 200 µ, but vary rapidly in size and direction with depth. Therefore, reliable relative scattering measurements require that the separation between the tracks in the depth of emulsion should be as small as possible (≤50 µ) whereas the separation in the plane of the emulsion may be as large as 200 µ.
The scattering constant for cell lengths of 1 mm. to 8 mm. has been determined. Our values are about 10% higher than the theoretical values, on the assumption that the proton energy in the Bevatron was known accurately at the time the plates were exposed.
Volume 65 Issue 2 February 1967 pp 104-118
The flux of He3 nuclei and the ratio He3/(He3+He4) in the low energy primary cosmic radiation have been determined using a stack of nuclear emulsions exposed at 3·1 g. cm.−2 of atmospheric depth from Fort Churchill, Canada, in June 1963. The grain-density
Volume 70 Issue 5 November 1969 pp 201-220
A detailed study of the composition and energy spectra of heavy nuclei of charge Z⩾3 in the primary cosmic rays has been made during the period of low solar activity, using two stacks of nuclear emulsions exposed in balloon flights from Fort Churchill, Canada, in June 1963. Each of the stacks was composed of 120 nuclear emulsions of three different sensitivities and was exposed at about 3·5 g. cm.−2 of residual air for about 11.1 hr. Reliable resolution of charges of nuclei from lithium to oxygen was obtained; for heavier nuclei, charge groups were determined. From the analysis of 793 tracks of nuclei with Z⩾3, results on the following aspects were obtained:
The differential energy spectra of L (Z=3–5), M (Z=6–9) and H (Z=10–28) nuclei were measured in the energy intervel 150–600 MeV/nucleon; integral fluxes were obtained for energy >600 MeV/nucleon;
The energy dependence of the L/M ratio at the top of the atmosphere was determined; the ratios were obtained as 0·45 ± 0·06 and 0·29 ± 0·03 in the energy intervals of 200–575, and >575 MeV/nucleon respectively;
Relative abundances of individual nuclei of Li, Be, B, C, N and O at the top of the atmosphere were determined as 36, 29, 55, 100, 60 and 106 respectively in the energy interval 150–600 MeV/nucleon; corresponding values were also obtained for energy >600 MeV/nucleon.
The differential fluxes of multiply charged nuclei measured by us and by other investigators were used to determine the solar modulation between solar maximum to solar minimum. It was found that solar modulation of the fluxes of M and He nuclei were consistent with R
The implications of these results are discussed.