Abstract
Describes a new kind of apparatus for making positron annihilation, angular correlation measurements. The use of a spark chamber as a two-dimensional gamma -ray detector enables two components of the momentum of photon pairs to be determined instead of the normal one. The development and construction of the special narrow gap spark chambers needed for this work are described and a discussion of the spark mechanism of narrow gap chambers is given. The use of television cameras to read out the spark chamber information is then considered and the logic of the complete recording system is briefly described. This apparatus was used to study a copper single crystal and the effect of the 'necks' of the copper Fermi surface was visible in the data. Various possible ways to improve the performance of the apparatus are then discussed.

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