Description
We will report on the ICF hohlraum experimental campaign that was conducted in 2025 on the LMJ laser facility. During this campaign, approximately 270 kJ of UV energy was delivered to the target using 80 beams. These beams were arranged in 20 quads with a fivefold azimuthal symmetry. The main objective of this campaign was to increase the capsule convergence ratio Rc compared to that achieved in the previous years [1,2], while still maintaining a symmetric implosion. Increase ablator thickness (from 70 to 100 μm) was applied in order to enhance Rc. The symmetry was tuned for the cylindrical and elliptical (rugby) gas filled hohlraum using the laser beam pointings and the outer to inner energy balance. The laser energy coupling and implosion performances were measured with a total of up to 13 plasma diagnostics that measured (i), time-resolved backscattering in the Brillouin and Raman ranges, (ii) the radiative temperature, (iii) the laser beam energy deposition at the hohlraum wall, (iv) the hot spot x-ray emission.
Another objective was to perform the first measurement of the in-flight shape of imploding ICF capsules at the LMJ facility using 2D X-ray radiography. The in-flight radiographies enable the analysis of several phases of the implosion. A number of specific adjustments for the shot dedicated to radiography were necessary. For example, two quads that could impact the radiography observation hole were turned off. These specificities cannot be described by classical 2D axisymmetric hydrodynamic simulations. Therefore, we will present 3D integrated simulations on these particular shots that complement our previous understanding of the experimental results [3.4]. Indeed, radiative losses through the radiography and observation holes, cross-beam energy transfer, or the 3D shape of the imploding capsule can only be interpreted with 3D simulations.
References:
[1] S.Liberatore et al. Phys. Plasmas 30, 122707 (2023)
[2] S. Lafitte et al. Bulletin of the APS, 67th Annual Meeting of the APS DPP (2025)
[3] S. Liberatore et al. Bulletin of the APS, 67th Annual Meeting of the APS DPP (2025)
[4] V.Tassin et al. Bulletin of the APS, 67th Annual Meeting of the APS DPP (2025)