Radiation Reaction Enhancement in Flying Focus Pulses

TL;DR

This paper proposes using flying focus pulses (FFPs) to enhance measurable radiation reaction effects in laser-electron interactions, enabling experiments at lower laser powers and improving stability and diagnostic accuracy.

Contribution

It introduces a novel FFP technique that extends interaction length and reduces power requirements for observing radiation reaction effects in electrodynamics.

Findings

FFPs enable longer interaction with laser peaks compared to Gaussian pulses.

Radiation reaction effects are observable at significantly lower laser powers with FFPs.

Numerical and analytical results confirm the feasibility of experimental detection of RR using FFPs.

Abstract

Radiation reaction (RR) is the oldest still-unsolved problem in electrodynamics. In addition to conceptual difficulties in its theoretical formulation, the requirement of exceedingly large charge accelerations has thus far prevented its unambiguous experimental identification. Here, we show how measurable RR effects in a laser-electron interaction can be achieved through the use of flying focus pulses (FFPs). By allowing the focus to counterpropagate with respect to the pulse phase velocity, a FFP overcomes the intrinsic limitation of a conventional laser Gaussian pulse (GP) that limits its focus to a Rayleigh range. For an electron initially also counterpropagating with respect to the pulse phase velocity, an extended interaction length with the laser peak intensity is achieved in a FFP. As a result, the same RR deceleration factors are obtained, but at FFP laser powers orders of magnitude lower than for ultrashort GPs with the same energy. This renders the proposed setup much more stable than those using GPs and allows for more accurate \emph{in situ} diagnostics. Using the Landau-Lifshitz equation of motion, we show numerically and analytically that the capability of emerging laser systems to deliver focused FFPs will allow for a clear experimental identification of RR.