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

对未来液壁激光聚变反应堆中气溶胶的形成和金属蒸气对最终光学元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100Pa时，气溶胶的形成并不是很关键。在未来的激光聚变接收器KOYO-F中，最后的光学元件将位于30米长的光束导管的末端，以防止中子造成的损坏。该反应堆的半径为3米。在快点火模式下，压缩激光的束管直径为15 cm，加热激光的束管直径为60 cm。微聚变爆炸后，高能离子可以被磁场屏蔽。由于微聚变的阿尔法加热，大量中性金属蒸气(在Koyo-F的情况下为10公斤)从第一液相壁蒸发。中性金属蒸气的大部分可以用…屏蔽。More有一套三个同步的旋转快门，每4赫兹打开3毫秒进行激光照射。当快门打开时，蒸汽流向束流导管的速度为100m/S。在液壁激光聚变反应堆中，这种流动对最终光学元件的污染是一个重要的问题。为了实验模拟水蒸气进入光束管的影响，我们制作了一个实际尺寸的1/5模型。模型束管连接到温度为1100℃的电炉上，以产生足够的蒸汽压力，同时反应器温度为600℃，束管另一端的温度保持在室温。在室温端放置一块见证玻璃板，作为最终光学元件的替代。由于这一现象取决于分子的平均自由程与束管直径的比值，因此束管中的压力比实际反应堆中的压力高5倍。结果表明：1)在以铅和锂铅为蒸汽源的两种情况下，束管中铅的分布是相似的。2)当束流管内压力为10~100pa时，在证明板上没有观察到铅沉积。在该压力范围内没有观察到直径约为0.1μm的气溶胶的形成。3)当气压接近1kPa时，观察到气溶胶的形成。我们认为，在未来的液壁激光聚变反应堆中，缓冲气体压力为10~100Pa时，可以防止最终光学元件的污染。较少

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