Heavy Primary Cosmic Rays Research Articles

Scientific Objectives of Explorer VII

This paper presents a description and the results of experiments conducted and carried aboard the Explorer VII satellite. Experiments covered are: radiation balance, heavy primary cosmic ray, Lyman-alpha X ray, the cosmic ray, exposed solar cell, micrometeorite, the earth radiation balance, and temperature measurement. A brief description of the power source and telemetering frequencies used on the satellite for the transmission of scientific information is also given.

A fast hyperfragment produced by a heavy primary cosmic ray

A stack of 6" x 12" G-5 600 microns Ilford emulsions, which was flown over Texas for 8 hours above 104,000 ft, was scanned for entering heavy primaries. These were followed until they either interacted or left the stack. One event was found which was interpreted as a decay in flight of a LAMBDA H/sup 4/. A description of this event is given. (W.D.M.)

Heavy Primary Cosmic Rays at Geomagnetic Latitude of 41°N

Heavy Primary Cosmic Rays at Geomagnetic Latitude of 41°N

Charge Spectrum, Mean Free Paths, and Flux of Heavy Primary Cosmic Rays at the Top of the Atmosphere

This investigation is restricted to primary cosmic rays of nuclear charges equal to or greater than ten at the geomagnetic latitude of 41 degrees north. Data were obtained from thick emulsions exposed at high altitudes over Texas. The flux, extrapolated to the top of the atmosphere, was found to be 2.65\ifmmode\pm\else\textpm\fi{}0.3 particles/${\mathrm{m}}^{2}$ sec sterad. The distribution histogram for the charge spectrum is included. The attenuation mean free paths for three groups were 28.5\ifmmode\pm\else\textpm\fi{}2.8, 26.7\ifmmode\pm\else\textpm\fi{}2.9, 23.6\ifmmode\pm\else\textpm\fi{}3.7 g/${\mathrm{cm}}^{2}$ for $Z=10\ensuremath{-}11, 12\ensuremath{-}14, 15\ensuremath{-}26$, respectively.

Interaction of Heavy Primary Cosmic Rays in Lead

The energy spectrum of heavy primary cosmic-ray nuclei was measured and found to be in agreement with the assumption that no primaries with energy below the geomagnetic cutoff enter the earth. The mean free path of the primary nuclei in lead was measured. If the transparency of nuclear matter is taken into account, the present results for lead and the measurements by others for lighter elements are in good agreement. If the expression ${R}_{A}={R}_{0}\ifmmode\times\else\texttimes\fi{}{A}^{\frac{1}{3}}$ is used for the radius of the nucleus, the data indicate for ${R}_{0}$ the value 1.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ cm. It is also shown that the ratio of the abundances of the charge groups $Z=12 \mathrm{to} 17$ and $Z=18 \mathrm{to} 28$ is \ensuremath{\sim}2.1.

Low-Momentum End of the Spectra of Heavy Primary Cosmic Rays

Measurements of the intensity of heavy primary cosmic-ray nuclei have been made above the atmosphere by means of the new Iowa balloon-launched rocket ("rockoon") technique at geomagnetic latitudes $\ensuremath{\lambda}=56\ifmmode^\circ\else\textdegree\fi{}, 76\ifmmode^\circ\else\textdegree\fi{}, \mathrm{and} 86\ifmmode^\circ\else\textdegree\fi{}$. The measuring instrument was a thin-walled, pulse-ionization chamber of 15-cm diameter. The observed data, in conjunction with geomagnetic theory, demonstrate a complete or nearly complete absence of primary heavy nuclei of $Z\ensuremath{\ge}6$ having a magnetic rigidity less than 1.5\ifmmode\times\else\texttimes\fi{}${10}^{9}$ volts ($\frac{p}{\mathrm{mc}}<0.8$), the result being the most significant for the C, N, O group. It is noted that this spectral cutoff occurs at closely the same magnetic rigidity, and distinctly not at the same velocity, as the previously reported cutoff in the spectra of primary protons and $\ensuremath{\alpha}$ particles.

Intensities of Heavy Cosmic-Ray Primaries by Pulse Ionization Chamber Measurements

The results of two rocket flights of electron collection, pulse ionization chambers above the atmosphere are summarized and discussed. It is shown that the data provide limiting information on the absolute intensities of the heavy nuclei in the primary cosmic radiation. Additional confidence in the photographic emulsion estimates of these intensities by other workers is provided by the consistency of their results with the entirely independent ionization chamber measurements.