Preparation of thin nuclear targets

The chemical mechanical and physical techniques employed in the preparation of nuclear targets are reviewed and the method of vacuum evaporation discussed in detail. A typical system for high-vacuum evaporation is described and the three methods of heating the target material to evaporating temperatures (resistance heating, induction heating and heating by means of electron bombardment) considered. Various electron bombardment configurations are compared. The relative merits of various thickness measuring techniques are described. Stages in the fabrication and mounting of self-supporting foils are considered with emphasis given to the preparation of thin self-supporting carbon foils used as target backings and stripper foils. Various target backings, and the merits of the more generally used release agents are described. The preparations of more difficult elemental targets are discussed, and a comprehensive list of the common targets is presented. (U.K.)