An Unusual Electron Shower

Abstract

Figure 1 depicts an event observed in a 600 µ glass-backed Ilford G5 emulsion. The shower occurred at point 0 as indicated by a sudden increase in grain density of the incident track. For the first 150 µ from 0 the grain density of all secondary tracks (which are not separated) is 46 ±4 grains per 50 (µ, approximately 3·5 times the plateau value (13·0 grains/50 µ). 200 µ from 0 five tracks are resolved and the sum of their grain densities is 64 ± 2 grains/50 µ, approximately five times plateau. These values suggest that one track originated some 150?200 µ from 0, although the possibility that it originated at 0 is not entirely excluded.