Electrons in plasmas produced by next-generation ultraintense lasers ($I>5\times {10}^{22}\mathrm{W}/{\mathrm{cm}}^2$) can be spin polarized to a high degree (10%–70%) by the laser pulses on a femtosecond time scale. This is due to electrons undergoing spin-flip transitions as they radiate $\gamma$-ray photons, preferentially spin polarizing in one direction. Spin polarization can modify the radiation reaction force on the electrons, which differs by up to 30% for opposite spin polarizations. Consequently, the polarization of the radiated $\gamma$-ray photons is also modified: the relative power radiated in the $\sigma$ and $\pi$ components increases and decreases by up to 30%, respectively, potentially reducing the rate of pair production in the plasma by up to 30%.

• Received 30 January 2017

DOI:https://doi.org/10.1103/PhysRevA.96.043407

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Published by the American Physical Society