An overview of the design of ELIPS—A new slow positron beam line

In this work, the progress made by the positron group from ELI-NP in the design of a new slow positron beam line is summarized. The rays of a brilliant gamma beam will be used to produce a slow positron beam of high intensity. The main results of the simulations, done for the geometry optimization of the Converter/Moderator Assembly (CMA) for $\gamma$-to-slow e${}^{+}$ conversion, are reported. By using the $\gamma$-beam with energy of up to 3.5 MeV and intensity of $2.4\times 10^{10}$ $\gamma$ $s^{-1}$, the slow e${}^{+}$ beam can be obtained with a maximum intensity of $\sim 2\times 10^6$ s⁻¹ with tungsten or platinum CMA. Solid neon moderation is applicable, and a successful implementation will result in a slow e${}^{+}$ beam of intensity $>10^7$ s${}^{-1}$. The CMA can be operated with a central hole ($⌀=2.5$ mm) in the foils in parasitic mode, $i.e.$, simultaneously with other $\gamma$-beam experiments, at the cost of reduced intensity by 18%. Furthermore, details on the slow positron transport and the spectroscopic systems, which are under construction, are provided.