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 lengtht, as tx, wherex is about 0·8 fort = 1 mm. to 3 mm. and about 0·5 fort = 3 mm. to 8 mm.
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.