Nie Zan, Li Fei, Morales Felipe, Patchkovskii Serguei, Smirnova Olga, An Weiming, Nambu Noa, Matteo Daniel, Marsh Kenneth A, Tsung Frank, Mori Warren B, Joshi Chan
Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, California 90095, USA.
Max Born Institute, Max-Born-Strasse 2A, D-12489 Berlin, Germany.
Phys Rev Lett. 2021 Feb 5;126(5):054801. doi: 10.1103/PhysRevLett.126.054801.
In situ generation of a high-energy, high-current, spin-polarized electron beam is an outstanding scientific challenge to the development of plasma-based accelerators for high-energy colliders. In this Letter, we show how such a spin-polarized relativistic beam can be produced by ionization injection of electrons of certain atoms with a circularly polarized laser field into a beam-driven plasma wakefield accelerator, providing a much desired one-step solution to this challenge. Using time-dependent Schrödinger equation (TDSE) simulations, we show the propensity rule of spin-dependent ionization of xenon atoms can be reversed in the strong-field multiphoton regime compared with the non-adiabatic tunneling regime, leading to high total spin polarization. Furthermore, three-dimensional particle-in-cell simulations are incorporated with TDSE simulations, providing start-to-end simulations of spin-dependent strong-field ionization of xenon atoms and subsequent trapping, acceleration, and preservation of electron spin polarization in lithium plasma. We show the generation of a high-current (0.8 kA), ultralow-normalized-emittance (∼37 nm), and high-energy (2.7 GeV) electron beam within just 11 cm distance, with up to ∼31% net spin polarization. Higher current, energy, and net spin-polarization beams are possible by optimizing this concept, thus solving a long-standing problem facing the development of plasma accelerators.
原位产生高能、高电流、自旋极化电子束是高能对撞机基于等离子体加速器发展面临的一项重大科学挑战。在本信函中，我们展示了如何通过用圆偏振激光场将特定原子的电子进行电离注入到束流驱动的等离子体尾场加速器中产生这样的自旋极化相对论性束流，为这一挑战提供了备受期待的一步式解决方案。通过含时薛定谔方程（TDSE）模拟，我们表明与非绝热隧穿 regime 相比，在强场多光子 regime 中氙原子自旋相关电离的倾向规则可以被反转，从而导致高的总自旋极化。此外，三维粒子模拟与 TDSE 模拟相结合，提供了氙原子自旋相关强场电离以及随后在锂等离子体中电子自旋极化的俘获、加速和保持的端到端模拟。我们展示了在仅 11 厘米的距离内产生高电流（0.8 kA）、超低归一化发射度（约 37 nm）和高能（2.7 GeV）的电子束，净自旋极化高达约 31%。通过优化这一概念，有可能产生更高电流、能量和净自旋极化的束流，从而解决了等离子体加速器发展面临的一个长期问题。
