LBE Paper
Liquid Lead Bismuth Target for Positron Production
Intro
Need for positrons
Intense positron sources are urgently needed for numerous applications, primarily for positron spectroscopy, which can have a huge impact on chemistry, physics, materials and biological science [1–4]. Additionally, high intensity positron beams are required to carry out gravitation experiments [5, 6] and to do chemistry with antimatter [7]. Finally, efficient positron traps also require an intense source of positrons [8, 9].
The easiest way to produce positron beams is to use e+-emitting sources, such as Na-22, which can have activity as high as 1 MBq. Another possibility is to generate positrons by pair production. In this case, an electron beam is stopped in a converter creating bremsstrahlung γ-rays. Provided that the energy of the primary electron beam is high enough, the generation probability of e-/e+ pairs is sufficiently high. Typically high Z material (such as tungsten) is preferred for positron production and moderation [10, 11]. For 10 MeV beam the optimum tungsten converter thickness is about 1.4 mm, and about 20% of the electron beam energy is converted into the x-rays.
Conventional W target (for a 10 MeV electron beam) – power limits?
Liquid metal targets as an alternative=
Beam Power capability of W -vs- LBE
Simple 1D calculations of heat transfer and temperature gradients
If we can back it up with ANSYS that would be great
Impact of windows on positron production
Walls might be needed for liquid LBE – windowless design is tricky
Effect of thin windows (different materials, different thickness) needs to be evaluated - by how much the production rate drops
Impact of LBE flow rate
Maximum LBE flow rate is defined by corrosion and depends on the material of the window (~ 2 m/s)
Limit on the flow rate means limit on the beam current and e+ production rate.
Conclusions
References
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