Highly spin-polarized multi-GeV electron beams generated by single-species plasma photocathodes

Abstract: High-gradient and high-efficiency acceleration in plasma-based accelerators has been demonstrated, showing its potential as the building block for a future collider operating at the energy frontier of particle physics. However, generating and accelerating the required spin-polarized beams in such a collider using plasma-based accelerators have been a long-standing challenge. Here we show that the passage of a highly relativistic, high-current electron beam through a single-species (ytterbium) vapor excites a nonlinear plasma wake by primarily ionizing the two outer 6⁢𝑠 electrons. Further photoionization of the resultant \(Yb^{2+}\) ions by a circularly polarized laser injects the \(4⁢𝑓^{14}\) electrons into this wake, generating a highly spin-polarized beam. Combining time-dependent Schrödinger equation simulations with particle-in-cell simulations, we show that a subfemtosecond, high-current (4 kA) electron beam with up to 56% net spin polarization can be generated and accelerated to 15 GeV in just 41 cm. This relatively simple scheme solves the perplexing problem of producing spin-polarized relativistic electrons in plasma-based accelerators.

Recommended citation: Zan Nie, Fei Li, Felipe Morales, Serguei Patchkovskii, Olga Smirnova, Weiming An, Chaojie Zhang, Yipeng Wu, Noa Nambu, Daniel Matteo, Kenneth A. Marsh, Frank Tsung, Warren B. Mori, Chan Joshi, "Highly spin-polarized multi-GeV electron beams generated by single-species plasma photocathodes," Phys. Rev. Research 4, 033015 (2022).
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