A high power positron converter based on recirculating free surface liquid metal jets in vacuum

An effective high-power positron converter for electron linear accelerators is not currently available from industry. A commercial source allows the nation's research institutes to have ready access to high- brightness positrons for a wealth of material science, nuclear, particle, and accelerator physics projects. Improving the efficiency of the converter target will allow these projects to proceed without in-house development and translates into lower operating costs and the ability to operate with higher beam currents. During Phase I, Xelera Research LLC designed, built, and tested a free surface liquid metal (GaInSn) jet converter/target prototype. Free surface liquid metal jets allow for significantly greater electron beam power densities than is possible with solid targets. During part of Phase II, a modified GaInSn converter/target will be constructed and tested at the Thomas Jefferson National Accelerator Facility (JLab). In addition, a PbBi converter, based on a similar design and capable of handling greater incident power, will be designed and constructed. This converter, unlike the GaInSn converter that operates at room temperature, requires that all its components be heated to 150°C. By considering electron energies in the 10 MeV and 120 MeV range and beam currents up to 1 mA, this project will lead to positron sources (including polarized positron sources, an important consideration for JLab in the future) that will be of benefit to researchers in the nuclear, solid-state, and low-energy particle physics communities. Higher power densities lead to greater positron production and, importantly, allow continuous wave (CW) operation. The team at Xelera Research LLC is uniquely experienced in the design and construction of novel optics, detectors, particle beam sources, injectors, beam transport systems, and beam dumps, and has pioneered work using modern optimization techniques for applications of interest to the Department of Energy.