Identifying the quantum radiation reaction by using colliding ultraintense lasers in gases

X. B. Li, B. Qiao, H. X. Chang, H. He, W. P. Yao, X. F. Shen, J. Wang, Y. Xie, C. L. Zhong, C. T. Zhou, S. P. Zhu, and X. T. He

Phys. Rev. A 98, 052119 – Published 15 November 2018

Abstract

A scheme for identifying the quantum radiation reaction effect on relativistic electron motion in strong electromagnetic fields is proposed, where two ultraintense lasers are used to collide with each other in a tenuous gas. Different from the previous method by collision of an ultraintense laser with a high-energy electron beam, in which the radiation reaction effect is evidenced by the energy loss in the electron energy spectrum, here the transition between the classical and quantum radiation reaction regimes is distinguished from the angular distribution of the total electron radiations. With no need of additional relativistic electron beams, the scheme is more robust and easily achievable in experiments. Both theory and two-dimensional particle-in-cell simulations show that the classical radiation dominates in the transverse direction perpendicular to laser axis, forming a dipolelike pattern, while that in the quantum regime dominates at four diagonal directions, constituting a butterflylike structure.

Received 26 May 2018

DOI:https://doi.org/10.1103/PhysRevA.98.052119

Physics Subject Headings (PhySH)

Gamma-ray generation in plasmas Quantum electrodynamics Radiation & particle generation in plasmas

General Physics

Authors & Affiliations

X. B. Li^1,2, B. Qiao^1,2,3,*, H. X. Chang^1,2, H. He⁴, W. P. Yao^1,2, X. F. Shen^1,2, J. Wang^1,2, Y. Xie^1,2, C. L. Zhong^1,2, C. T. Zhou^1,3, S. P. Zhu^5,6, and X. T. He^1,2,5

¹Center for Applied Physics and Technology, HEDPS, and SKLNPT, School of Physics, Peking University, Beijing 100871, China
²Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240, China
³Center for Advanced Material Diagnostic Technology, Shenzhen Technology University, Shenzhen 518118, China
⁴Shanghai Institute of Laser Plasma, Shanghai 201800, China
⁵Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
⁶Graduate School of China Academy of Engineering Physics, P. O. Box 2101, Beijing 100088, China

^*bqiao@pku.edu.cn

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Issue

Vol. 98, Iss. 5 — November 2018

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Images

Figure 1
Schematic of the simulation setup. Two laser pulses irradiate a gas target from opposite sides. Electric field of the laser pulses is represented by blue and red colors. Sampled electron trajectories are shown in blue lines for the classical model and orange lines for the quantum model. Squiggly arrows denote the dominant radiation directions. Classical electrons are trapped in the electric field nodes, while QED electrons migrate between different nodes.
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Figure 2
(a) Angular distribution of radiated energy ${log}_{10} d E / d θ$ . Blue line: Classical. Orange line: QED. (b) Integrated frequency spectra of the total radiated photons. Blue line: Classical. Orange line: QED. (c) Angular distribution of radiation power $d P / d θ$ of electrons versus time for the LL case. (d) Same as (c), but for QED case. The result is consistent with the angular distribution of radiated energy.
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Figure 3
(a) The parameter $χ_{e}$ of electrons at $t = 20 T_{0}$ for the classical model. (b) Same as (a), but for the QED model. Due to the straggling effect, the parameter $χ_{e}$ of the quantum model is higher than that of the classical model. (c) Electron density normalized by $n_{c}$ in the $(x, y)$ plane at $t = 20 T_{0}$ for the classical model. Electrons are trapped in the electric field nodes. (d) Same as (c), but for the QED model. (d) Corresponding longitudinal electron density, i.e., $y = 0$ for both models and the longitudinal profile of the normalized electric fields $E_{y}$ (dashed red line). For the classical model, most electrons concentrate around $x = \pm λ / 4$ ; while for the QED model, a large fraction of electrons also distribute at other nodes.
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Figure 4
Six sampled electron trajectories in real space $(x, y)$ , phase subspace $(x, p_{x}, p_{y})$ . (a) and (c) Classical model. (b) and (d) QED model. Dotted lines denote the location of nodes of electric fields $(x = \pm λ / 4, \pm 3 λ / 4, \pm 5 λ / 4)$ . Color denotes the temporal variation in laser period $T_{0}$ . Limit cycles and attractors appear at $x = \pm λ / 4$ for the classical model. No such structures are shown for the quantum model.
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Figure 5
(a) Poincaré plots for 1000 trajectories starting from $t = 20 T_{0}$ to $t = 30 T_{0}$ for the classical model. (b) Same as (a), but for the quantum model. For the classical model, attractors are shown at $x = \pm 4 / λ$ , while for the QED model, no such structures appear.
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Figure 6
The dominant radiation angle $θ$ (see Fig. 1) with respect to different $a_{0}$ for the classical model (blue line) and the QED model (orange line), respectively.
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