Speaker
Description
The positron beams play a unique role in antimatter research and particle physics, providing crucial insights into various fundamental questions. In materials science, they are routinely used for studying defects and microstructures in materials. So far the research at Bhabha Atomic Research Centre using positrons is focused on material science aspects.
The conventional monoenergetic slow positron beams use radioisotopes like Na-22. Moderated positron beams using Na-22 are simplest in their design but offer low intensity beams of the order of 104 to 105 e+/sec. The enhanced intensity of positrons is a prerequisite to achieve high aerial density of positronium required for studies towards realization of Bose-Einstein condensate of positronium, anti-matter laser etc., as well as state of the art experiments in material science.
For achieving high intensity of positrons, the reactor based positron beams are one way forward. Though we have focused earlier on Na-22 based beams, a reactor based positron beam is proposed to be installed at Dhruva Research Reactor, BARC. In this beam, the thermal neutrons from the reactor core will be utilized to produce prompt gamma-rays via 113Cd(n,γ)114Cd reaction which would further undergo pair production as well as moderation in suitably designed tungsten assembly. These positrons are magnetically transported outside. To design the reactor based positron beam, the capture gamma production, transport and subsequent pair production process were simulated using FLUKA code [1]. Various parameters such as cadmium thickness, design of tungsten foil-based moderator assembly were optimized. Transport of the slow positrons was simulated using SIMION [2,3]. Design of outer radiation shielding assembly was carried out using FLUKA. Our simulations suggest an intensity of ~7x108 e+/s positrons in a ~20 mm diameter which is comparable to the various other similar facilities operating worldwide [3-6].
The talk would focus on our experience with Na-22 beams in brief and discuss in detail the proposed high intensity reactor based positron beam, the current status and future prospects.
References
[1]. C. Ahdida et al., Frontiers in Physics 705 (2022); Giuseppe Battistoni et al., Annals of Nuclear Energy 82 (2015)
[2]. D. A. Dahl, SIMION 3D 7.0, INEEL-95/4043, Revision 5, 2000
[3]. J. Moxom et al. Nucl. Instrum. Methods Phys. Res.A 579.1 (2007).
[4]. A. van Veen et al. Proc. of IAEA Symposium on Research Reactor Utilization, Safety and Management. IAEA, 2000.
[5]. C. Hugenschmidt et al., Applied Physics A 74 (2002).
[6]. K. Sato et al, Nucl. Instrum. Methods Phys. Res.B, 342 (2015)
