Estimation on contamination of final optics with metal vapor in laser fusion reactor with liquid wall

对带液体壁的激光聚变反应堆中气溶胶的形成和金属蒸气对末级光学器件的污染进行了实验和数值模拟。结果表明，当反应器内的背压小于100 Pa时，气溶胶的形成不是很关键。在未来的激光聚变反应堆KOYO-F中，最终光学器件将位于30米长的束管的末端，以防止中子造成的损坏。反应堆的半径为3米。在快速点火模式的情况下，用于压缩激光器和加热激光器的光束导管的直径分别为15 cm和60 cm。微聚变爆炸后，高能离子可以被磁场屏蔽。大量中性金属蒸气（在KOYO-F的情况下为10 kg）由于来自微熔合的α加热而从第一液体壁蒸发。中性金属蒸气的大部分可以用 关于我们 h一组三个同步旋转快门，每4 Hz打开3 ms用于激光照射。在快门打开时，蒸气朝向束管的流速为100 m/s。为了实验模拟蒸汽进入束流管道对激光聚变反应堆光学系统的影响，我们制作了一个实际尺寸的1/5模型。模型束流导管与温度为1100 ℃的电炉相连，以在反应堆温度为600 ℃时产生足够的蒸汽压。束流导管另一端的温度保持在室温。在室温端放置一个见证玻璃板作为最终光学元件的替代。由于这一现象取决于分子平均自由程与束流管直径的比值，因此束流管中的压力保持在实际反应堆中压力的5倍以上，结果表明：1）以Pb和LiPb为蒸汽源时，束流管中Pb的分布相似; 2）束流通道内压力为10 ~ 100 Pa时，在验证板上没有观察到Pb的沉积。在此压力范围内，未观察到直径约为0.1 μm的气溶胶形成。3)当压力接近1 kPa时，观察到气溶胶的形成。结果表明，缓冲气体压力在10 ~ 100 Pa时，可以防止液体壁激光聚变反应堆末级光学元件的污染。少

Formation of aerosol and contamination of final optics with metal vapor in a future laser fusion reactor with a liquid wall were experimentally and numerically simulated. The result indicated that formation of aerosol was not so critical if the back pressure in the reactor is less than 100 Pa. Contamination of the final optics at the end of a beam duct can be prevented with low-pressure buffer gas,In a future laser fusion rector KOYO-F, the final optics will be located at the end of a 30 m long beam duct to prevent damage due to neutrons. The radius of the reactor is 3m. In a case of fast ignition mode, the diameters of the beam duct for compression lasers and heating laser are 15 cm and 60 cm, respectively. After micro fusion explosion, energetic ions can be shielded with a magnetic filed. Lot of neutral metal vapor (10 kg in a case of KOYO-F) evaporates from the first liquid wall due to alpha heating from the micro fusion. The major part of the neutral metal vapor can be shielded wit … More h a set of three synchronized rotary shutters that opens 3 ms for laser irradiation every 4 Hz. The flow velocity of vapor toward the beam duct is 100 m/s at the time when the shutter opens. Contamination of the final optics due to this flow is important issue in the laser fusion reactor with a liquid wall.To experimentally simulate the influence of vapor coming into the beam duct, we made a 1/5 model of actual size. The model beam duct is connected to an electric furnace whose temperature is 1100 C to produce sufficient vapor pressure while the temperature of reactor is 600 C. The temperature at the other end of the beam duct was kept at room temperature. A witness glass plate was located at the room temperature end as the substitution of final optics. Since the phenomena depends on the ratio of the mean free path of molecules to the diameter of the beam duct, the pressure in the beam duct was kept 5 times higher than that in the actual reactor.As the result, 1)distributions of Pb in the beam duct were similar in both cases where Pb and LiPb were used as the vapor source. 2)No deposition of Pb was observed on the witness plate when the pressure in the beam duct was 10 to 100 Pa. No formation of aerosol, whose diameter is around 0.1 μm, was observed at this pressure range. 3)When the pressure was close to 1 kPa, formation of aerosol was observed. We conclude that contamination of the final optics in the future laser fusion reactor with liquid wall can be prevented if the pressure of buffer gas is 10 to 100 Pa. Less