Foam-buffered laser-matter interactions

Recent experiments indicate that low-density foam buffer layers can significantly mitigate the perturbing effects of beam non-uniformities in direct drive laser-matter interactions. Results of a computational study with a 2D ALE code are reported here. Typical targets consisted of 50 μm of 50 mg/cm3 C10H8O4 foam attached to a 10 μm foil and covered with 250 A of gold. These targets were exposed to ∼1.2 ns, flat topped, green light pulses at ∼1.4x1014 W/cm2 intensity, bearing 30 μm lateral perturbations. Without the buffer layers the foils were severely disrupted after 1 ns of laser illumination. Buffering could provide stability for more than 2 ns of full shell acceleration. Our study shows that the high thermal conductivity of the foam results in flattened shocks in the foam plasma, communicating a smoothed laser drive to the accelerated shells. Preheat from the gold hastens conversion of solid foam to a heated plasma