Elemental research on laser fusion reactor KOYO-F

We conceptually designed the laser fusion power plant KOYO-F based on fast ignition scheme and the result was reported at IAEA-FEC 2006. KOYO-F has a liquid LiPb flow as the first protective wall. After the activity we concentrated elemental researches on the issues to increase the reliability of the concept. The researches include two experiments on formation of aerosols and micro-particles, protection of laser beam ports using a magnetic field, stability of liquid LiPb flow. We used discharge method to contribute understanding formation of aerosols with aid of computer simulation. Energy deposition by alpha particles is volumetric heating that can be experimentally simulated more likely by electric discharge method than conventional laser heating. We observed lot of 30-nanometer-diameter aerosols on a witness plate, which agrees with numerical simulation. The other experiment is focused on the hydrodynamic phenomena of ablation process using backside illumination of a metal membrane on transparent substrate. Hydrodynamic instability was observed, which results formation of much larger droplets than aerosols. Beam ports that stick out of the LiPb flow need special scheme to protect from alpha particles. We found a 0.8 T magnetic field synchronized with laser irradiation was effective as the protective shield. A 3-mm-thick stable flow was formed on a mockup for cascade scheme of KOYO-F. The mockup was designed so that the Weber number of the film flow on the first wall was the same as the actual liquid LiPb flow from the flow stability point of view. The minimum flow rate to obtain the continuous film flow was confirmed experimentally and numerically. (author)