Laser-driven high-quality positron sources as possible injectors for plasma-based accelerators

Abstract

The intrinsic constraints in the amplitude of the accelerating fields sustainable by radio-frequency accelerators demand for the pursuit of alternative and more compact acceleration schemes. Among these, plasma-based accelerators are arguably the most promising, thanks to the high-accelerating fields they can sustain, greatly exceeding the GeV/m. While plasma-based acceleration of electrons is now sufficiently mature for systematic studies in this direction, positron acceleration is still at its infancy, with limited projects currently undergoing to provide a viable test facility for further experiments. In this article, we study the feasibility of using a recently demonstrated laser-driven configuration as a relatively compact and inexpensive source of high-quality ultra-relativistic positrons for laser-driven and particle-driven plasma wakefield acceleration studies. Monte-Carlo simulations show that near-term high-intensity laser facilities can produce positron beams with high-current, femtosecond-scale duration, and sufficiently low normalised emittance at energies in the GeV range to be injected in further acceleration stages.

Laser-Wakefield Electron Beams as Drivers of High-Quality Positron Beams and Inverse-Compton-Scattered Photon Beams

“…Quasi-neutral beams have been observed for converters of thickness >∼ 5L rad . [96], and Alejo et al [102]]. The numbers presented here are intended as indicative figures only.…”

Shaping trailing beams for beam loading via beam-induced-ionization injection at FACET

“…Recent breakthroughs in PBAs have demonstrated its potential wide range of applicability. PBAs are being explored for positron acceleration [9][10][11]. Two PBA stages driven by laser pulses in capillary discharge plasmas were used to first produce and then accelerate electron beams, at the BELLA Center [12].…”

Copious positron production by femto-second laser via absorption enhancement in a microstructured surface target

“…There are three main processes capable of creating positrons based on laser-plasma interactions: trident process, Bethe-Heitler (BH) process and Breit-Wheeler (BW) process. With the state-of-the-art laser facilities, the production of high-density and high-energy positron beams has been successfully demonstrated in experiments via the BH or Trident process [7][8][9][10][11][12][13][14][15][16] . Mainly, there are two effective methods to produce positrons.…”

“…One is a "1-step" method, which uses pico-second (ps), kilo-Joule class lasers to directly irradiate a high-Z planar target, which can produce positrons with yield up to 10 12 8-10 . The other is a "2-step" method, which uses femto-second (fs) lasers to indirectly produce positrons [11][12][13][14][15][16] : (i) quasi-monoenergetic electrons production via laser wakefield acceleration (LWFA); (ii) the electrons shoot into a high-Z target, and produce positrons. In ultrahigh intense laser regime ( > I Wcm 10 / 22 2 ), there are schemes proposed to produce high yield positrons by triggering Breit-Wheeler (BW) process, such as a 10 PW laser striking a solid 17 , two laser pulses colliding in near-critical plasmas 18 , electron self-injection and trapping inside a laser pulse 19 , and a multi-PW laser scattering GeV electron beams 20 , etc.…”

“…A positron source based on a fs laser system is of great interest in many fields. In the "2-step" method based on LWFA, the positron beam has remarkable advantages of high energy (several hundreds of MeV), narrow divergence (a few mrad) and short duration (fs scale) [11][12][13][14][15] . Furthermore, the LWFA electron energy can be enhanced by the use of copropagating two-color laser pulses, leading to a considerable boost in the positron energy in a bremsstrahlung-based positron generation configuration 16 .…”