Positron sources: from conventional to advanced accelerator concepts-based colliders

Abstract

A: Positron sources are the key elements for the future and current lepton collider projects such as ILC, CLIC, SuperKEKB, FCC-ee, Muon Collider/LEMMA, etc., introducing challenging critical requirements for high intensity and low emittance beams in order to achieve high luminosity. In fact, due to their large production emittance and constraints given by the target thermal load, the main collider parameters such as the peak and average current, the emittances, the damping time, the repetition frequency and consequently the luminosity are determined by the positron beam characteristics. In this paper, the conventional positron sources and their main properties are explored for giving an indication to the challenges that apply during the design of the advanced accelerator concepts. The photon-driven positron sources as the novel approach proposed, primarily for the future linear colliders, are described highlighting their variety and problematic.

Positron Sources for Future High Energy Physics Colliders

“…Table 1: Performances of ever existed positron sources (readapted from [22]. Some parameters were not found in literature and, therefore, marked as "-".…”

“…The concept is shown in Figure 7. In this proposal, the positrons can be generated either by emission from a 𝛽-decay emitter, such as 22 Na, which produces roughly 10 9 positrons per second, or by impacting a 5 MeV electron beam on a high-Z target. The positrons pass through a solid-neon moderator which reduces their energy so that they can be trapped [119].…”

“Snowmass’21” Accelerator Frontier

“…They are particularly formidable for sources of beams with special characteristics, such as polarized electrons and ions or ultra-small emittances, and for tertiary and secondary particles, such as muons and positrons. High intensity positron sources, that are critical for future e + e − linear colliders, may be simplified using advanced accelerator concepts and photon-driven schemes that can potentially outperform conventional e + production techniques [71].…”