Collisions of heavy particles

Pictures of heavy particle into stationary targets in nuclear emulsions photographs.

Fragmentation by collision of a Calcium nucleus

In this event, shown in three overlapping photographs; a nucleus with Z ~20 (Calcium) make a glancing collision with a nucleus in the emulsion at point ‘a’ lower left and upper centre. Emerging from the encounter are about 20 fast singly charged particles, together with a ‘jet’ of 4 or 5 relativistic α particles and a heavier fragment. Before he particles in this jet have diverged sufficiently to allow the individual tracks to be identified, one of the particles makes the prominent nuclear disintegration of a silver or bromine nucleus, seen at ‘b’. Careful study under the microscope shows that the collision at ‘b’ was probably made by an α-particle, and not by the heaviest member of the jet. After the disintegration at ‘b’, the remaining fragments of the first collision at ‘a’ diverge sufficiently to allow their identification, and they are found to be an oxygen nucleus accompanied by four α-particles. There is a great reduction in the number of δ-rays associated with the unresolved jet of secondary particles, immediately after the collision at ‘a’, as compared with that of the primary particle, although the total charge of the secondaries is not less than that of the primary. This result provides a good illustration of the fact that the value of nδ depend on Z².