Slow-positron apparatus for surface studies

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Abstract
We describe an apparatus for producing an intense low energy positron beam of well defined energy by moderating the decay positrons from a radioactive source using a clean single crystal convertor with high conversion efficiency (ε≃10−3). These positrons are used as a probe to study well characterized surfaces in an ultra‐high vacuum system. The magnetically focussed beam can deliver a current on the order of 2×105 positrons/s to a target when a 300 mCi 58Co source is used. Characteristics of the apparatus are given and possible directions for future improvements are mentioned.