93 / 2023-04-13 15:20:30

Branched flows in high-energy-density physics

branched flow,intense laser,relativistic electron beam,High Energy Density Physics

极端光下的基础物理学 > 基础物理-II

Branched flow refers to a phenomenon of the formation of treebranch-like filaments as waves or particle flows propagate through an uneven medium. Branched flow is attributed to weak and successive scatterings by smooth obstacles deflecting traveling waves or particles. Pulsed cosmic rays, rogue waves in the ocean, and electron strands in semiconductors are all relevant to branched flows. So far, investigations on the branched flow phenomenon mainly focus on linear regimes where the flow does not alter the medium properties.



In this report, we consider the propagation of intense lasers and relativistic electron beams through uneven plasmas, thereby bringing the branched flow phenomenon into the field of high-energy-density physics with high nonlinearity. We find that as an intense laser propagates through the medium, cascading local photoionization by the incident laser, together with the response of freed electrons in the strong laser fields, triggers space–time-dependent optical unevenness. The resulting branching pattern depends dramatically on the laser intensity. That is, the branching here is distinct from the existing linear ones. Likewise, when a relativistic electron beam propagates through foam targets, it can cascade into thin branches with local density hundred times the initial value and deposits its energy two orders of magnitude more efficiently than that in homogeneous plasma of similar average density. Such beam branching is attributed to successive weak scatterings of the beam electrons by the unevenly distributed self-generated fields in the foam pores.



Our work for the first time brings the branched flow phenomenon to high-energy-density physics and should open an interesting new direction in research on matter and radiation at extremes.





References:

[1] K. Jiang, T. W. Huang, C. N. Wu, M. Y. Yu, H. Zhang, S. Z. Wu, H. B. Zhuo, A. Pukhov, C. T. Zhou, and S. C. Ruan. Branched flow of intense laser light in plasma with uneven density distribution. Matter Radiat. at Extremes 8, 024402 (2023).

[2] K. Jiang, T. W. Huang, R. Li, M. Y. Yu, H. B. Zhuo, S. Z. Wu, C. T. Zhou, and S. C. Ruan. Branching of high-current relativistic electron beam in porous materials. Phys. Rev. Lett. (Accepted, 2023).