7 / 2023-03-06 21:18:36

Ultra-bright laser-driven sources of MeV particles and radiation using long-scale foams irradiated with sub-ps pulses

Laser-driven sources, DLA electrons, foams

Experiments on the interaction of relativistic laser pulse with pre-ionized foam targets were carried out at the PHELIX-facility at GSI, Darmstadt. Experiments and simulations showed a greatly improved conversion of laser energy into energy of MeV-particles and radiation. In the interaction of ~ 10¹⁹ W/cm² sub-ps laser pulses with pre-ionized polymer foams, high-current beams of direct laser-accelerated (DLA) electrons with an effective temperature 10× higher than the ponderomotive limit and with up to 100 nC charge of directed fraction of electrons with energies above 7.5 MeV were measured [1, 2]. These results are in good agreement with 3D PIC-simulations [1, 2].

Using foams combined with µm-thin foils or mm-thick high-Z convertors, we have successfully demonstrated the generation of ultra-bright bremsstrahlung with photon energies of up to 50-60 MeV and a record-breaking conversion efficiency up to 2 % for photons > 7.5 MeV (giant dipole resonance)[2, 3]; record efficiency of neutron production in gamma-driven nuclear reactions [3]; super-intense betatron radiation [4, 5], and strongly enhanced proton acceleration. The application of DLA electrons to study the Flash effect was also successfully demonstrated.

The DLA process proves to be very robust and can be used to generate ultra-bright laser-driven sources of particles and photons with energies of tens of MeV already at moderate relativistic laser intensity, which is typical for large kJ-class PW laser facilities, used in ICF research.

[1] Rosmej, O.N. et al., “Interaction of relativistically intense laser pulses with long-scale near critical plasmas for optimization of laser based sources of MeV electrons and gamma-rays”, New J. Phys. 21 (2019) 043044

[2] O N Rosmej et al, “High-current laser-driven beams of relativistic electrons for high energy density research”, Plasma Phys. Control. Fusion 62 (2020) 115024

[3] M. M. Günther et al, Forward-looking insights in laser-generated ultra-intense gamma-ray and neutron sources for nuclear applications and science, Nat Commun 13, 170 (2022) 

[4] X. F. Shen et al, Bright betatron x-rays generation from picosecond laser interactions with long-scale near critical density plasmas, Appl. Phys. Lett. 118, 134102 (2021)

[5] O. N. Rosmej et al, Bright betatron radiation from directlaser-accelerated electrons at moderate relativistic laser intensity, Mat. Radiat. Extremes 6, 048401 (2021)