290 / 2023-04-25 15:48:18

The use of AM foams in laser-plasma interaction experiments

Additive manufactured (AM) foams present significant interest in the context of high-power laser-matter interaction. Printed foam targets provide a highly controlled environment and permit a high degree of versatility in terms of density, spatial structure and materials. This presentation describes an approach to the design and fabrication of low-density AM foams and their use in a laser-plasma interaction experiment.

Foams with an octet truss cellular structure have been designed using a finite element approach and printed on a 7 μm thick copper substrate using two-photon laser lithography, see Fig. 1. A foam in the form of a cylinder of a diameter 0.95 mm and depth 0.6 mm has a stiffness of 2−4 MPa sufficient for it use in experiment in a free-standing geometry [1].

AM and chemically produced foams are irradiated at the PALS laser facility using the third harmonic of iodine laser at wavelength of 438 nm with pulse duration of 300 ps and energy of 200 J focused on a spot of diameter of 120 μm. The electron density of a fully ionized foam is about one third of the critical density. We measured the velocity of ionization front propagating inside the foam, electron and ion temperatures and characteristics of hot electrons generated in plasma and compared them with chemically produced foams of the same average density.

Experimental results are simulated with a hydrodynamic code FLASH equipped with a sub-grid model describing laser interaction with foam and its homogenization [2]. Excitation of parametric instabilities and generation of hot electrons is simulated with a particle-in-cell code SMILEI. The results of simulations and a comparison with experiments will be presented.

This work has been partially carried out within the framework of the EUROfusion Consortium and has received funding from EUROfusion project CfP-FSD-AWP21-ENR-01-CEA-02.

[1] T. Wiste et al., J. Appl. Phys. 133, 043101 (2023)

[2] L. Hudec et al., Phys. Plasmas 30, 042704 (2023).