Revision as of 13:51, 19 December 2016

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

1. Lee KH, Yang G, Koymen AR, et al (1994) Positron annihilation induced Auger electron spectroscopy studies of submonolayer Au on Cu(100): Direct evidence for positron localization at sites containing Au atoms. Phys Rev Lett 72:1866–1869. doi: 10.1103/PhysRevLett.72.1866

2. Martin P, Strong AW, Jean P, et al (2012) Galactic annihilation emission from nucleosynthesis positrons. Astron Astrophys Vol 543, idA3, 15 pp. doi: 10.1051/0004-6361/201118721

3. Gabrielse G, Bowden NS, Oxley P, et al (2002) Background-Free Observation of Cold Antihydrogen with Field-Ionization Analysis of Its States. Phys Rev Lett 89:213401. doi: 10.1103/PhysRevLett.89.213401

4. Amoretti M, Amsler C, Bonomi G, et al (2002) Production and detection of cold antihydrogen atoms. Nature 419:456–459. doi: 10.1038/nature01096

5. Kalaydzhyan T (2016) Gravitational mass of positron from LEP synchrotron losses. Sci Rep 6:30461. doi: 10.1038/srep30461 6. Perez P, Sacquin Y, G B-LA and C, et al (2012) The GBAR experiment: gravitational behaviour of antihydrogen at rest. Class Quantum Gravity 29:184008. doi: 10.1088/0264-9381/29/18/184008

7. Green J, Lee J (1964) Positronium chemistry. Academic Press

8. Jensen K, Walker A (1990) Positron thermalization and non-thermal trapping in metals. J. Phys. Condens. Matter

9. Danielson JR, Hurst NC, Surko CM (2013) Progress towards a practical multicell positron trap. In: AIP Conf. Proc. American Institute of PhysicsAIP, pp 101–112

10. Chemerisov S, Jonah CD, Jean P KJLVAMRJPSGKTBJ and VG, et al (2011) Development of high intensity source of thermal positrons APosS (Argonne Positron Source). J Phys Conf Ser 262:012012. doi: 10.1088/1742-6596/262/1/012012

11. Abbott D, Adderley P, Adeyemi A, et al (2016) Production of highly-polarized positrons using polarized electrons at MeV energies. doi: 10.1103/PhysRevLett.116.214801

Difference between revisions of "LBE Paper"