Strong signatures of radiation reaction below the radiation-dominated regime.

The influence of radiation reaction (RR) on multiphoton Thomson scattering by an electron colliding head-on with a strong laser beam is investigated in a new regime, in which the momentum transferred on average to the electron by the laser pulse approximately compensates the one initially prepared. This equilibrium is shown to be far more sensitive to the influence of RR than previously studied scenarios. As a consequence, RR can be experimentally investigated with currently available laser systems and the underlying widely discussed theoretical equations become testable for the first time.