Abstract
Signatures of stochastic effects in the radiation of a relativistic electron beam interacting with a counterpropagating superstrong short focused laser pulse are investigated in a quantum regime when the electron’s radiation dominates its dynamics. We consider the electron-laser interaction at near-reflection conditions when pronounced high-energy gamma-ray bursts arise in the backward-emission direction with respect to the initial motion of the electrons. The quantum stochastic nature of the gamma-photon emission is exhibited in the angular distributions of the radiation and explained in an intuitive picture. Although, the visibility of the stochasticity signatures depends on the laser and electron beam parameters, the signatures are of a qualitative nature and robust. The stochasticity, a fundamental quantum property of photon emission, should thus be measurable rather straightforwardly with laser technology available in near future.
Highlights
The generation petawatt laser systems[1, 2] will open a door to novel regimes of laser-matter interaction[3, 4], and to new perspectives for the investigation of fundamental problems[5,6,7,8,9]
We investigate signatures of the stochastic nature of photon emission in the nonlinear Compton scattering in the quantum radiation dominated regime (RDR) during the interaction of a superstrong short focused laser pulse with a counterpropagating relativistic electron beam
We focus on the strongest radiation domain along the polarization plane in the region of −15° ≤ φ ≤ +15°, analysing the radiation ednoemrgayind. εT Rh/e[dsθto scinh(aθs)t]ic =n ∫a−t+u115r5 e doφf pdhεoRt/odnΩeamnidsstihoen pishcolteoanrlynudmiscbeerrndib∼NlRe/i[ndθR sAinD(θ: )a] s=in ∫g−l+e115b5 r doφaddhNigR/hd-Ωintienntshitiys gamma-photon peak is formed in the near-reflection direction when stochasticity effects (SE) is included, while in the case without SE multiple radiation peaks emerge corresponding to the emission from different laser cycles
Summary
The considered quantum RDR requires the invariant parameters χ ≡ γ(ω0/m)ξ(1 − β cosθ) ≈ 10−6γξ < 1 and. It provides a natural way to treat the electron dynamics in the external field classically but to take into account in the radiation-reaction quantum-recoil corrections (but not stochasticity). A typical angular distribution of radiation which carries the signature of the stochastic nature of photon emission, is illustrated in Fig. 1; φ = 0° and ±180° correspond to the positive and negative directions of the laser polarization, respectively. In a tightly focused laser beam, other components of the electric field, Ey and Ez, are not negligible and play a significant role in the electron dynamics and the photon emission. ΕT Rh/e[dsθto scinh(aθs)t]ic =n ∫a−t+u115r5 e doφf pdhεoRt/odnΩeamnidsstihoen pishcolteoanrlynudmiscbeerrndib∼NlRe/i[ndθR sAinD(θ: )a] s=in ∫g−l+e115b5 r doφaddhNigR/hd-Ωintienntshitiys gamma-photon peak is formed in the near-reflection direction when SE is included, while in the case without SE multiple radiation peaks emerge corresponding to the emission from different laser cycles. The main detectable difference of RADs with and without SE is the peak number of the radiation: the previous has only one radiation peak, and the latter has several peaks corresponding to the laser-cycle structure
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