Speaker
Description
Laser wakefield acceleration (LWFA) [1,2] is a promising approach for producing compact sources of high-energy electron beams and ultrashort X-ray pulses [3], offering a potential alternative to large-scale synchrotron facilities [4,5] for applications in imaging, materials science, and ultrafast science. One promising strategy for increasing the X-ray yield is the accelerator–radiator scheme[6], in which electrons are first accelerated in a low-density plasma stage and subsequently enter higher-density radiator, where enhanced transverse oscillations lead to stronger X-ray emission.
In this work, we investigate the optimization of such accelerator–radiator configurations using particle-in-cell simulations [7]. Due to the highly nonlinear nature of laser–plasma interactions and the large parameter space, we employ Bayesian optimization [8] to efficiently explore the dependence of X-ray generation on the radiator position and plasma density. The optimization targets the laser-to-X-ray conversion efficiency and identifies operating regimes where electron rephasing in the radiator significantly enhances betatron emission, achieving more than an order-of-magnitude increase in X-ray yield compared to the accelerator-only configuration.
These results demonstrate the potential of accelerator–radiator schemes for developing brighter compact X-ray sources while highlighting the role of efficient simulation-driven optimization in studying complex laser–plasma systems. The work contributes to the development of advanced betatron sources for experiments at ELI Beamlines [9] and illustrates the value of high-performance computing in accelerating their design and optimization.
References:
[1] T. Tajima and J. M. Dawson, Laser electron accelerator, Physical review letters 43, 267 (1979).
[2] A. Picksley et al., Matched guiding and controlled injection in dark-current-free, 10-GeV-class, channel-guided laser-plasma accelerators, Physical Review Letters 133 (2024) 255001.
[3] A. Pukhov, et al., Laser wake field acceleration: the highly non-linear broken-wave regime, Applied Physics B 74, 355 (2002).
[4] S. Corde, et al., Femtosecond x rays from laser-plasma accelerators, Reviews of Modern Physics 85, 1 (2013).
[5] F. Albert, et al., Laser wakefield accelerator based light sources: potential applications and requirements, Plasma Physics and Controlled Fusion 56, 084015 (2014).
[6] J. Ferri, et al., High-brilliance betatron g-ray source powered by laser-accelerated electrons, , Physical review letters 120, 254802 (2018)
[7] J. Derouillat, A. Beck, F. Pérez, T. Vinci, M. Chiaramello, A. Grassi, M. Flé, G. Bouchard, I. Plotnikov, N. Aunai, et al., Smilei: A collaborative, open-source, multi-purpose particle-in-cell code for plasma simulation, Computer Physics Communications 222, 351–373 (2018).
[8] A. Döpp, C. Eberle, S. Howard, F. Irshad, J. Lin and M. Streeter, Data-driven science and machine learning methods in laser–plasma physics, High Power Laser Science and Engineering 11, e55 (2023)
[9] U. Chaulagain, et al., Eli gammatron beamline: a dawn of ultrafast hard x-ray science, in Photonics, Vol. 9 (MDPI, 2022) p. 853.