Studies of Bursts at Sea Level

Abstract

Data obtained in some 2000 hours of photographic registration of cosmic-ray ionization bursts at sea level (some of which has been published previously) is reported in full. The measurements cover a very wide range of burst size (factor 2000) in two ion chambers of volumes 175 and 1.1 liters, with argon, nitrogen, and hydrogen gas fillings at pressures ranging from 1.5 to 87 atmos. When the ion chambers (thin-walled) are unshielded the bursts are very clearly separable into a component resulting from the extensive cascade showers from the atmosphere and a component resulting from heavily ionizing particles from cosmic-ray induced nuclear disintegrations. The number-size distributions to be expected in the ion chambers from single protons and alpha-particles produced by nuclear disintegrations are calculated on the assumption that these particles have the energy spectrum given by Bagge. The effect of columnar recombination at high pressures in nitrogen and argon is discussed and allowed for. The agreement obtained between the calculated curves and those observed shows that the interpretation of this component as chiefly caused by single heavily ionizing protons and alpha-particles is probably correct. Some very rare bursts of anomalously large size are found under moderate thicknesses of lead. The experimental results of others are reviewed, and detailed comparisons are made.