Flow induced beam deflection measurements in ablation plasmas

APS abstract 2025, Colin Bruulsema, bruulsema1@llnl.gov



Flow induced beam deflection measurements in ablation plasmas

C. Bruulsema¹, N. Lemos¹, Avi Milder², Charles Ruyer³, Will Farmer¹, Stefan Huller⁴ , Wojciech Rozmus⁵ , Will Riedel<sup>1

1</sup> Lawrence Livermore National Laboratory

7000 East Ave, Livermore, CA 94550

² University of Rochester Laboratory For Laser Energetics

250 E River Rd, Rochester, NY 14623

3Centre d'études scientifiques et techniques d'Aquitaine

15 Av. des Sablières, 33114 Le Barp, France

⁴Ecole Polytechnique

Boulevard Gaspard Monge, 91120 Palaiseau

⁵University of Alberta

116 St&85 Av, Edmonton AB T6G2R3

We measured ponderomotive laser deflection in a well characterized ablation plasma. Laser driven acoustic waves in flowing plasma are enhanced when the transverse flow reaches the sound speed, driving density perturbations that cause beam deflection in the downstream direction[1,2].

Our experiments create low-density plasmas with a flow velocity similar to its sound speed, making ponderomotive beam deflection angles much larger than the small refraction angles expected in these conditions. Laser deflection is measured for a high and a low ion acoustic damping case, which have different Mach number dependence.

The plasma conditions along the beam path are measured with Tomson Scattering and are used to calculate expected deflection and refraction angles, which are compared with observed deflections.

[1] H. A. Rose, Laser beam deflection by flow and nonlinear self-focusing, Physics of Plasmas 3, 1709 (1996).

[2] J. D. Ludwig, S. H ̈uller, H. A. Rose, C. Bruulsema,W. Farmer, P. Michel, A. L. Milder, G. F. Swadling,and W. Rozmus, Shock formation in flowing plasmas by temporally and spatially smoothed laser beams, Phys. Plasmas 31, 032103 (2024).



This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344