Por Jorge Vieira (Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Portugal).

Coherent light sources, such as free electron lasers, provide bright beams for biology, chemistry, physics and advanced technological applications. As their brightness increases, these sources are also becoming progressively larger, with the longest being several km long (e.g. Linac Coherent Light Source - LCLS at SLAC). Plasma accelerators, are much more compact, and can play a key role in bringing these sources to smaller laboratories. Achieving this goal depends directly on the onset of superradiance in plasma-based accelerators. Here, we propose a novel light source concept that may bring temporal coherence and superradiance to plasma accelerator based light sources. The mechanism is suitable for experimental demonstrations in current plasma accelerator laboratories.

Instead of focusing on single particle motions, we investigate the radiation produced by an ensemble of light emitting particles exhibiting collective, matter-wave effects. Such collective motions, which can be as simple as a plasma wave, are pervasive in plasmas and plasma based accelerators. We find that the trajectory of the centroid of such collective perturbation (which we denote as a quasi-particle) determines key radiation aspects, such as temporal coherence, just as if it were a single particle undergoing a similar trajectory. We apply this concept to obtain superradiant emission in plasma accelerator based-light sources, in order to generate broadband and narrow bandwidth superradiant and temporally coherent radiation in the XUV/soft-xray region [1,2]. We use theory and particle-in-cell simulations complemented by the Radiation Diagnostic for Osiris (RaDiO) [3].

• [1] J. Vieira et al, Nature Physics 17,99 (2021)
• [2] B. Malaca et al, Nature Photonics 18, 39–45 (2024)
• [3] M. Pardal et al, Comp. Phys. Communs. 285, 108634 (2023)