Anomalous Disintegration of Nuclei by Cosmic Rays

Abstract

AS is well known¹, one effective method for the observation of the disintegration of atomic nuclei by cosmic rays is the method of the 'thick-layer' photographic plates suggested and developed in the Radium Institute of the Academy of Sciences of the U.S.S.R.². The tracks of these disintegrations in such plates are mostly in the form of forks with irregular angular distribution ('stars'). They correspond chiefly to protons, more seldom to α-particles and still more seldom to particles with a stronger 'ionization power'. The 'yield' of nuclear disintegrations at sea-level is approximately 8 × 10^-3 disintegrations in an hour per 1 cm.² of the area of the plate. This yield rapidly increases with height, reaching a value fifty times greater at a height of 7,000 metres3. At sea-level the greatest percentage of disintegrations corresponds to the triple forks. Forks with five tracks are met comparatively seldom, and only with the increase of height is the slow increase of the number of ejected particles in one disintegration observed. In addition to the disintegrations in the form of stars, there are observed also disintegrations in the form of 'showers', that is, in the form of forks with a pronounced unilateral direction of tracks (inside the narrow solid angle). Tracks in the showers may belong to protons as well as to mesotrons. We suggested in previous papers⁴ the possibility of the registration of slow mesotrons in the 'thick-layer' plates, and also the possibility of estimating their mass from the average distance between two neighbouring developed grains. In one of our papers⁵ there was shown a shower consisting of about a hundred heavy particles, which was obtained on a plate exposed at a height of about 9,000 metres.