Direct-drive fuel-assembly experiments with gas-filled, cone-in-shell, fast-ignitor targets on the OMEGA Laser

The fuel assembly of gas-filled, cone-in-shell, fast-ignitor targets is being studied experimentally at the OMEGA Laser Facility. The spherical plastic (CH) shells with a ∼24 μm wall thickness had a 70° or 35° opening-angle gold cone inserted. The targets, filled with ∼10 atm of D 3 He or D 2 , were imploded by direct illumination with up to 21 kJ of 351 nm laser light. Some experiments used a backlighter to study the fuel assembly and mixing of cone material into the dense core. No significant mixing of the cone and core material was observed. Using both fusion products and backlit images, an areal density of ∼60 to 70 mg cm -2 was inferred for the dense core assembly. The filling of the inside of the cone, where the ultrafast laser propagates in integrated fast-ignitor experiments, was studied using a streaked optical pyrometer. No plasma was seen inside the cone before the assembled core reached peak compression. These results are promising for successful integrated fast-ignitor experiments on the OMEGA EP Facility, scheduled to be completed in 2007.