Speaker
Description
The very large power in electron beams needed to generate positrons requires that solid tantalum or tungsten targets have some means of heat removal, e.g., by cooling high speed rotating discs of such materials. The mechanical complexity of such rotating discs in the ultra-high vacuum of an accelerator beamline suggests that other target possibilities be considered. In particular, the free surface liquid metal jet target possesses some advantages. It is conceptually simple compared to a solid metal target, it can operate directly in an ultra-high vacuum environment due to the very low vapor pressure of the LMs used, and it can handle very high heat loads and act directly as target coolant. A free surface liquid metal target prototype has been constructed and tested at Xelera Research. The prototype uses a GaInSn eutectic and has been successfully operated in a 3.0$\times 10^{-8}$ Torr vacuum and a 0.25T magnetic field for extended periods of time. Jet velocities in the 2--10m/s range show less than 1% variation in thickness with time. Neutron and gamma radiation fields were investigated using MCNP6.2. In addition, CFD simulations of the nozzle, including heat transfer, were done using Fluent-ANSYS v2024R1, a volume-of-fluid multi-phase transport model. One phase is GaInSn and the other is air at a pressure of 7.5$ \times 10^{-9}$ Torr. A final version of the device will be installed and tested at the LERF facility at JLab in a 10MeV, 1mA electron beam.
