Radiation Reaction near the Classical Limit in Aligned Crystals

Abstract

An accelerated charged particle emits electromagnetic radiation. If the driving force is sufficiently strong, the radiated energy becomes comparable to the kinetic energy of the particle and the back-action of the emitted radiation (radiation reaction) significantly alters the dynamics of the particle. The Landau-Lifshitz (LL) equation has been proposed as the classical equation to describe the dynamics of a charged particle in a strong electromagnetic field when the effects of radiation reaction are taken into account. Hitherto, the experimental problem in validating the LL equation has been to achieve sufficiently strong fields for radiation reaction to be important without quantum effects being prominent. Notwithstanding, here we provide a quantitative experimental test of the LL equation by measuring the emission spectrum for a wide range of settings for 50 GeV positrons crossing aligned silicon single crystals near the $(110)$ planar channeling regime as well as 40 GeV and 80 GeV electrons traversing aligned diamond single crystals near the $⟨100⟩$ axial channeling regime. The experimental spectra are in remarkable agreement with predictions based on the LL equation of motion with small quantum corrections for recoil and, in case of electrons, spin and reduced radiation emission, as well as with a more elaborate quantum mechanical model. Our experiment clearly shows the inadequacy of the Lorentz force as the sole agent of force on the particles in the classical limit, due to its absence of radiative energy loss in describing the dynamics of high-energy charged particles in strong electromagnetic fields like those in aligned single crystals.

22 pages, 13 figures, accepted for submission in PRD

References in corpus (6)

• Quantum radiation reaction in laser-electron beam collisions
• Aspects of electromagnetic radiation reaction in strong fields
• Signatures of quantum effects on radiation reaction in laser -- electron-beam collisions
• Longitudinal and transverse cooling of relativistic electron beams in intense laser pulses
• Robust signatures of quantum radiation reaction in focused ultrashort laser pulses
• Experimental investigations of synchrotron radiation at the onset of the quantum regime

Cited by in corpus (9)

• Single Particle Detection System for Strong-Field QED Experiments
• All-atom relativistic molecular dynamics simulations of channeling and radiation processes in oriented crystals
• Reduction of order, resummation and radiation reaction
• Exact solutions in radiation reaction and the radiation-free direction
• High-resolution modeling of nonlinear Compton scattering in focused laser pulses
• Analytical solutions for quantum radiation reaction in high-intensity lasers
• Atomistic modelling of the channeling process with radiation reaction force included
• On the status of channeling radiation and laser based radiation sources
• Short-term evolution of electron wave packet in a constant crossed field with radiative corrections