Inertial confinement fusion, frequently referred to as ICF, inertial fusion, or laser fusion, is a means of producing energy by imploding small hollow microspheres containing thermonuclear fusion fuel. Polymer microspheres, which are used as fuel containers, can be produced by solution-based micro-encapsulation technique better known as density-matched emulsion technique. The specifications of these microspheres are very rigorous, and various aspects of the emulsion hydrodynamics associated with their production are important in controlling the final product. This paper describes about the optimization of various parameters associated with density-matched emulsion method in order to improve the surface smoothness, wall thickness uniformity and sphericity of hollow polymer microspheres. These polymer microshells have been successfully fabricated in our lab, with 3-30 µm wall thickness and 50-1600 µm diameters. The sphericity and wall thickness uniformity are better than 99%. Elimination of vacuoles and high yield rate has been achieved by adopting the step-wise heating of W 1 /O/W 2 emulsion for solvent removal.

No abstract

An electro-magnetic interference noise shielding enclosure for Pockels cells for high speed synchronized switching has been set-up and tested. The shielding effectiveness of the aluminum enclosures housing the Pockels cells and the electronic circuitry has been measured using a high impedance probe and is found to be ∼ 50 dB. This ensures a noise-free and synchronized electro-optic switching in an Nd:glass re-generative amplifier of chirped pulse amplification based table top terawatt laser system.

A simple and very efficient gas jet levitation technique for levitating inertial confinement fusion (ICF) targets has been developed. A low velocity gas jet through diverging nozzle generates precisely controlled low Reynolds number flow pattern, capable of levitating polymer microballoons up to 2500 m diameter. Different shaped diverging nozzle are investigated, satisfactory levitation is achieved with simple conical shapes. With this setup microballoon can be levitated for hours with excellent stability, continuous rotation and at the desired height (reproducible with in less than 100 m). The height of stabilization depends upon cone angle of diverging nozzle and velocity of levitating gas. This technique is very robust and highly insensitive to external disturbances like nonuniform temperature fields and vibrations.This setup is very economical to fabricate, easy to operate and can be used efficiently in various spray coating application involving plastic and metallic layers on microballoons.

Growth rates of the Rayleigh-Taylor instability, in direct drive inertial confinement fusion targets, can be reduced using a radiation-preheated polymer ablator. Polystyrene microshells doped with ultrafine metal particles (200-300 Å) are fabricated using the multiple emulsion technique, which can serve as the outer layer for radiation-preheated target. Preliminary results show that microshells of approximately 200-1500 µm can be produced with various wall thicknesses. Further optimization of the process is in progress to produce very thin (wall thickness ∼1 µm) microshells with ultrasmooth surface finish (∼15 nm).