Production of polarized particle beams via ultraintense laser pulses

Reviews of Modern Plasma Physics (2022) 6:38 https://doi.org/10.1007/s41614-022-00099-9 REVIEW PAPER Production of polarized particle beams via ultraintense laser pulses Ting Sun1 · Qian Zhao1 · Kun Xue1 · Zhi‑Wei Lu1 · Liang‑Liang Ji2 · Feng Wan1 · Yu Wang1 · Yousef I. Salamin3 · Jian‑Xing Li1 Received: 3 May 2022 / Accepted: 23 October 2022 © Division of Plasma Physics, Association of Asia Pacific Physical Societies 2022 Abstract High-energy spin-polarized electron, positron, and 𝛾 -photon beams have many significant applications in the study of material properties, nuclear structure, particle physics, and high-energy astrophysics. Thus, efficient production of such polarized beams attracts a broad spectrum of research interests. This is driven mainly by the rapid advancements in ultrashort and ultraintense laser technology. Currently, available laser pulses can achieve peak intensities in the range of 1022–1023 Wcm−2, with pulse durations of tens of femtoseconds. The dynamics of particles in laser fields of the available intensities is dominated by quantum electrodynamics (QED) and the interaction mechanisms have reached regimes spanned by nonlinear multiphoton absorption (strong-field QED processes). In strong-field QED processes, the scattering cross-sections obviously depend on the spin and polarization of the particles, and the spin-dependent photon emission and the radiation-reaction effects can be utilized to produce the polarized particles. An ultraintense laser-driven polarized particle source possesses the advantages of high brilliance and compactness, which could open the way for the unexplored aspects in a range of researches. In this work, we briefly review the seminal conclusions from the study of the polarization effects in strong-field QED processes, as well as the progress made by recent proposals for production of the polarized particles by laser–beam or laser–plasma interactions. Keywords Strong-field QED · Nonlinear Compton scattering · Nonlinear Breit– Wheeler pairs · Quantum Monte-Carlo simulations · Particle-in-cell simulations * Qian Zhao * Jian‑Xing Li Extended author information available on the last page of the article Published online: 15 November 2022 13 Vol.:(0123456789) 38 Page 2 of 36 Reviews of Modern Plasma Physics (2022) 6:38 1 Introduction Spin-polarized particles are employed extensively to investigate the properties of materials, in atomic and molecular structure investigations (Gay 2009; Schultz and Lynn 1988; Danielson et al. 2015), in nuclear structure studies (Abe 1995; Uggerhøj 2005; Alexakhin et al. 2007), and in high-energy physics (MoortgatPick 2008). Being chiral, spin-polarized relativistic particles are ideally suited for selective enhancement or suppression of specific reaction channels which, in turn, makes them better at characterizing the quantum numbers and chiral couplings of the new particles (Barish and Brau 2013). For instance, polarized 𝛾 photons with tens-of-MeV energy can be used to excite polarization-dependent photofission of the nucleus in the giant dipole resonance (Speth and van der Woude 1981), while polarized 𝛾 photons with GeV energy play crucial roles in meson photoproduction (Akbar 2017) and the test of vacuum birefringence (Bragin et al. 2017). In astrophysics polarization of the 𝛾 photons provides detailed insight into the 𝛾 -photon emission mechanism and the properties of dark matter (Laurent et al. 2011; Bœhm et al. 2017). Furthermore, spin-polarized lepton beams are used in investigations of the spin dependence of the fundamental interactions and the violation of symmetries such as parity (Schlimme 2013). In addition, they play a central role in precise measurements pertaining to the spin-dependent processes that focus attention on physics beyond the standard model. Such measurements can compete with direct searches at the high-energy accelerators (Androic 2018). Conventional methods of producing high-energy polarized 𝛾 photons include linear Compton scattering (Howell et al. 2021) and bremsstrahlung (Olsen and Maximon 1959; Kuraev et al. 2010). The former employs unpolarized electron beams in which the emitted 𝛾 -photon polarization is determined by the driving laser polarization, because the radiation formation length is much longer than the laser wavelength (Baier et al. 1973; Ritus 1985; Sokolov and Ternov 1986; Khokonov and Bekulova 2010). Because of the relatively small scattering crosssection of the linear Compton scattering (around 10−3 barns∕MeV ), luminosity of the electron–photon collision is rather low (Omori et al. 2006). The collision luminosity can be increased using high-intensity lasers, but in this case the interaction moves into the nonlinear regime. Many theoretical and experimental investigations have recently been conducted into how to acquire brilliant high-energy 𝛾 -rays, even with spin or orbital angular momentum in the nonlinear regime. In incoherent bremsstrahlung, an electron beam is passed through a thin metal target and radiates in the presence of the Coulomb field near the nucleus (Giulietti 2008; Albert and Thomas 2016). Here, the circularly polarized (CP) 𝛾 -photons are generated by longitudinally spin-polarized (LSP) electrons (Uggerhøj 2005; Timm 1969) while the linearly polarized (LP) 𝛾 -photons cannot be generated because of the large scattering angle (Baier et al. 1998). LP 𝛾 -photons can be obtained by coherent bremsstrahlung when an electron beam is passed through a crystal, which gets periodically disturbed by the nucleus. The damage threshold of the crystal, however, places limits on the energy of the electron beam and the flux of the 𝛾 -rays. 13 Reviews of Modern Plasma Physics (2022) 6:38 Page 3 of 36 38 The usual sources of polarized leptons are obtained in a storage ring via the Sokolov–Ternov (ST) effect (Sokolov and Ternov 1986) and Bethe–Heitler pair production. The transversely spin-polarized (TSP) lepton beams directly obtained via the ST effect require long polarization times, since the corresponding static magnetic fields are relatively weak. Longitudinally spin-polarized (LSP) leptons can be produced in a Bethe–Heitler process via high-energy circularly polarized 𝛾 -photons interacting with a high-Z target (Abbott 2016). In such a process, the low luminosity of the 𝛾 -photon beam is compensated by meeting the high repetition rate requirement to yield a dense positron beam for applications (Variola 2014). Generally speaking, the transverse and longitudinal polarizations can be transformed into each other by a spin-rotator. This, however, has the drawbacks of demanding quasi-monoenergetic beams and being accompanied by a beam intensity reduction. To enable the spin-dependent sciences at the ever-demanding energy and brilliance, development of advanced polarized particle beam is considered essential. The rapid development of ultraintense ultrashort laser techniques have followed the advent of petawatt laser systems. Current (...truncated)