Experimental test of electron dynamics in the radiation-dominated regime
In plain words
At high enough intensity an electron radiates away most of its energy within one laser cycle, which is predicted to trap electrons where the field is strongest instead of pushing them out. This prediction has not been tested.
Precise statement
When the classical radiation-reaction parameter $R_c = \alpha a0 \chi >\sim 1$, an electron radiates an energy comparable to its own per laser period; simulations predict radiation-reaction trapping and anomalous radiative trapping of electrons at field antinodes of counterpropagating pulses, attractor trajectories, and strong gamma-ray conversion efficiency. Determine experimentally whether these trapping effects occur, by measuring electron and gamma-ray angular distributions and conversion efficiency versus intensity in a standing-wave or colliding-pulse geometry, and compare with LL and quantum-stochastic predictions.
What would settle it
Colliding-pulse experiments at multi-petawatt facilities showing the predicted intensity-dependent change in electron and gamma-ray angular distributions.