Design and Modeling of a Liquid Xenon Positron Target

Positron sources have been identified as a key technological need for future collider and accelerator applications [1,2]. We explore liquid xenon (LXe) as a target material for the production of positron beams [3]. LXe has several properties that make it attractive as a positron target. First, due to its density and high atomic number, LXe has a relatively short radiation length for a nonmetal. Second, LXe has a large heat of vaporization; it can absorb significant energy before vaporizing. Third, using LXe as a positron target removes the concern of long term degradation observed with solid positron targets because the LXe is continuously refreshed. Finally, LXe is non-toxic and requires much less safety infrastructure than liquid metal targets. High power targets made of liquid lead and mercury have been deployed previously in high energy physics applications, but the toxicity of these materials limits their use.

We present Geant4 simulations of electron beam-driven positron targets for parameters relevant to the ILC [4] and Ce+BAF source [5] using the G4Beamline code. We study the deposition and transport of heat in the LXe target with Computational Fluid Dynamics simulations using ANSYS Fluent software, leveraging experience gained in the design of the Qweak LH2 target [6]. Safe and reliable liquid target technology will be a welcome addition to the field of positron targetry and may even provide a path to ultra-high power applications such as Muon Colliders in the future.