Dense Polarized Positrons from Beam-Solid Interaction.

Area of Science:

• Nuclear and particle physics
• Plasma physics
• Quantum electrodynamics

Background:

• High spin polarization of relativistic positron sources is crucial for nuclear and particle physics.
• Producing dense polarized positrons remains a significant challenge in current research.

Purpose of the Study:

• To present a novel, simple, and effective method for generating dense, highly spin-polarized positron beams.
• To explore the underlying physics of positron production via electron-solid target interactions.

Main Methods:

• Impacting a relativistic, high-density electron beam directly onto a solid target surface.
• Utilizing three-dimensional particle-in-cell simulations to model the plasma dynamics and positron generation.

Main Results:

• Generation of asymmetric quasistatic magnetic fields (megatesla scale) along the target surface.
• Efficient production of copious polarized positrons through radiative spin flips and multiphoton processes.
• Demonstration of a dense, highly polarized multi-GeV positron beam with >40% average spin polarization and nC-scale charge per shot.

Conclusions:

• The proposed method offers an effective route for producing dense, highly polarized positron beams.
• This technique opens new avenues for laserless strong-field quantum electrodynamics studies.
• It provides a novel pathway for developing advanced high-energy polarized positron sources.