Orbital angular momentum radiation and polarization of relativistic electrons in magnetic fields
Ziqiang Huang, Qi Meng, Xuan Liu, Wei Ma, Zhen Yang + 4 more
TLDR
Relativistic electrons in magnetic fields can have their orbital angular momentum polarized by synchrotron radiation, much faster than spin polarization.
Key contributions
- Demonstrates that synchrotron radiation can polarize the orbital angular momentum (OAM) of vortex electrons.
- Shows OAM transition rates are asymmetric, favoring OAM decrease, analogous to the Sokolov-Ternov effect.
- Finds OAM polarization can approach unity and is orders of magnitude faster than spin polarization.
- Provides analytical solutions for OAM relaxation time and stationary-state distribution.
Why it matters
This research establishes a novel mechanism for polarizing the orbital angular momentum of electron beams using synchrotron radiation. The significantly faster OAM polarization time compared to spin polarization opens new avenues for controlling vortex electron beams. This has major implications for high-energy accelerator applications.
Original Abstract
While spin polarization from synchrotron radiation is well established, the polarization of orbital angular momentum (OAM) in such radiative processes remains elusive. We study radiation and polarization of relativistic electrons in a uniform magnetic field, focusing on OAM polarization radiation for vortex electrons which carry intrinsic OAM. The results illustrate that transition rates are asymmetric in the low-photon-energy regime, favoring OAM decrease, analogous to the spin-flip asymmetry in the Sokolov-Ternov effect. Under these conditions, synchrotron radiation can polarize the OAM. The characteristic relaxation time and stationary-state OAM distribution are obtained analytically. The polarization of spin about \(\mathcal{P}_{\text{spin}}\) reaches \(92.38\%\), while that of \(\mathcal{P}_{\text{OAM}}\) can even approach almost unity for a large OAM; however, their polarization behaviors are different. For typical storage ring parameters, the OAM polarization time is orders of magnitude shorter than the spin polarization time. Thus, synchrotron radiation offers a mechanism for controlling vortex electron beams which carry OAM for high-energy accelerator applications.
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