Experimental evidence of quantum radiation reaction in aligned crystals

Abstract

Quantum radiation reaction is the influence of multiple photon emissions from a charged particle on the particle's dynamics, characterized by a significant energy-momentum loss per emission. Here we report experimental radiation emission spectra from ultrarelativistic positrons in silicon in a regime where quantum radiation reaction effects dominate the positron's dynamics. Our analysis shows that while the widely used quantum approach is overall the best model, it does not completely describe all the data in this regime. Thus, these experimental findings may prompt seeking more generally valid methods to describe quantum radiation reaction. This experiment is a fundamental test of quantum electrodynamics in a regime where the dynamics of charged particles is strongly influenced not only by the external electromagnetic fields but also by the radiation field generated by the charges themselves and where each photon emission may significantly reduce the energy of the charge.

Spin-dependent radiative deflection in the quantum radiation-reaction regime

“…The bunch get polarized along y because the electrons with positive s y tend to be scattered upwards while those with negative s y downwards. Experimental measurement of this anti-symmetric phenomenon provides a new degree of freedom to study the quantum RR effect in addition to spin-free phenomena [7,10,[31][32][33]. Effects of the electron beam energy spread and angular divergence are illustrated in figure 4(c).…”

Efficiency of radiation friction losses in laser-driven ‘hole boring’ of dense targets

“…However, in our particular conditions, due to (a) RF induced suppression in the growth of g¢ (15) and (b) reduction of x¢ with increasing of v HB a further increase in the laser intensity results in a very slow growth of χ starting from a 0 ;a cr . In the strong field limit,  ¥ a 0 the HB velocity approaches the speed of light, and the parameter (1)).…”

“…Finally, we account for the attenuation of the laser field in the plasma and the dependence of the laser intensity on time and its radial distribution in the focal spot. The laser field amplitude a 0 is not constant within the evanescence length ℓ s , but dropping down, leading to a considerable decrease of the 'efficient' value of a 0 entering equations (15) and (16). Figure 3 based on the HB model of [30] sketches the electron and the ion density distributions along the propagation direction at the initial stage of the interaction when the electrons are pushed forward by light pressure, while the ions still remain immobile and homogeneously distributed inside the plasma layer.…”

Realising single-shot measurements of quantum radiation reaction in high-intensity lasers

“…Another alternative is to use an aligned crystal lattice to provide the strong fields, although in this case the a 0 is fixed by the nuclear field strength. This alternative approach has recently produced interesting results although again definitive model comparison is a challenge [62].…”