Laser study into and explanation of the direct-indirect target concept

The idea of direct-indirect target is experimentally tested with planar targets from LPI made of low-density metal foam (nanosnow) or of nanoparticles (30%) in plastic aerogels. The laser experiments in BARC have shown that compared to plain targets the foams of/with nanoparticles demonstrate: 1) better x-ray emissivity ; 2) smoother energy distribution over the target surface; 3) material flow from low-density wall being slower and more uniform; 4) active transverse energy transport over the target plane. These properties could be useful for hohlraums and direct-indirect concept

Particle size effect on velocity of gold particle embedded laser driven plastic targets

A scheme to enhance the target foil velocity has been investigated for a direct drive inertial fusion target. Polymer PVA (polyvinyl alcohol or (C2H4O)n) target foils of thickness 15–20 μm were used in plain form and also embedded with gold in the nano-particle (Au-np) or micro-particle (Au-mp) form. Nano-particles were of 20–50 nm and micro-particles of 2–3 μm in size. 17% higher target velocity was measured for foils embedded with nano-particle gold (Au-np) as compared to targets embedded with micro-particles gold (Au-mp). The weight of gold in both cases was in the range 40–55% of the full target weight (atomic percentage of about 22%). Experiments were performed with the single beam of the Prague Asterix Laser System (PALS) at 0.43 μm wavelength (3ω of the fundamental wavelength), 120 Joule energy and 300 psec pulse duration. Laser intensity on the target was about 1015 W/cm2. A simple model has been proposed to explain the experimental results