A new approach to positron angular correlation studies

A new kind of apparatus is described for carrying out positron angular correlation measurements. The apparatus employs a spark chamber as a two dimensional gamma -ray detector and is able to determine two components of the momentum of photon pairs produced by annihilating electron positron pairs. The results of an experiment on a copper single crystal are described and it is shown that the experimental data show the effect of the necks of the copper Fermi surface. Various possibilities for improvements to the apparatus are discussed. Finally a mathematical method is proposed which it is believed would permit the complete momentum for photon pairs to be derived from a single experiment at a mirror plane orientation. If this method were operated successfully then it would allow a Fermi surface to be derived which was correct for electrons in the region of the positron. This has been shown to be very similar to the true Fermi surface.