The effect of the electron's spin magnetic moment on quantum radiation in strong electromagnetic fields

Ultra-intense laser pulses can create sufficiently strong fields to probe quantum electrodynamics effects in a novel regime. By colliding a 60 GeV electron bunch with a laser pulse focussed to the maximum achievable intensity of $10^{23}$ Wcm$^{-2}$, we can reach fields much stronger than the critical Schwinger field in the electron rest frame. When the ratio of these fields $\chi_e\gg1$ we find that the hard ($>25$ \thinspace GeV) radiation from the electron has a substantial contribution from spin-light. 33% more photons are produced above this energy due to spin-light, the radiation resulting from the acceleration of the electron's intrinsic magnetic moment. This increase in high-energy photons results in 14% more positrons produced with energy above $25$ GeV. Furthermore, the enhanced photon production due to spin-light results in a 46% increase in the electron recoil radiation reaction. These observable signatures provide a potential route to observing spin-light in the strongly quantum regime ($\chi_e\gg1$) for the first time.