Development of durable solid-hydrogen pellet injector for fueling to fusion plasmas

固体氢球团注入聚变等离子体燃料的必然性已经得到广泛的认识，然而，球团注入技术还没有建立到足以满足与反应堆相关的操作能力。本项目旨在演示与高温稳态等离子体操作相关的高性能耐用颗粒注入器。主要目标是：(1)1小时长运行能力和无限运行时间的可行性；(2)重复率大于10hz，发射可靠性大于95%；(3)球团速度大于1.5 m/s。这3个条件应在原型注入器中同时满足。开发的基本要素是通过螺杆挤出机进行凝固和挤压成型，并通过通用冰箱进行冷却，使液氦自由运行。低温足以使氢凝固（10K）已在4小时内从室温达到…在此基础上，成功地进行了15mg/s连续凝固1小时的实验。在35mm/s的速度下挤压成型到一根棒材。在此操作过程中，温度升高被抑制到小于1K。从杆形成球团和发射球团的机构已与螺杆挤出机相结合。以10赫兹的频率连续注入1000秒，这意味着已经尝试了1万个颗粒，并确认了完整颗粒发射的可靠性超过99%。对于球团速度，最大值限制在600m/s。对推进剂气体快速阀的性能与气体差压和气体流速的关系进行了研究，提出了提高到1km/s的前景。进一步的研究，以达到初始规格的颗粒速度仍然存在。综上所述，成功实现了与高温稳态等离子体操作相关的高性能耐用球团注入器的初始目标中的两个主要目标，并将提高球团速度的问题分解为元素问题。少

Inevitability of solid hydrogen pellet injection for fueling to fusion plasmas has been widely recognized However, the technology of pellet injection has not been established sufficiently to fulfill the operational capability relevant to a reactor. This project aims at demonstration of a high-performance durable pellet injector relevant to high-temperature steady-state plasma operation. Major goals are (1) capability of 1-hour long operation and feasibility of unlimited operational duration, (2) repetition rate of more than 10 Hz and reliability of pellet launch of more than 95%, and (3) pellet velocity of more than 1.5 m/s. These 3 conditions should be fulfilled simultaneously in a proto-type injector. Essential elements in development are solidification and extrusion molding by means of a screw extruder, and cooling by a GM refrigerator which enables liquid helium free operation. Cryogenic temperature enough for solidification of hydrogen (10K) has been achieved in 4 hour from room t … More emperature. Then continuous solidification at the rate of 15mg/s for 1 hour has been successfully demonstrated. Extrusion molding to a rod has been available at the speed of 35mm/s. The temperature increase has been suppressed to less than 1K during this operation. The mechanism to form pellets from a rod and to launch the pellets has been combined with the screw extruder. The continuous pellet injection at 10 Hz for 1,000s, which means 10,000 pellets has been attempted and reliability of more than 99% for intact pellet launch has been confirmed. As for the pellet velocity, the maximum value has been limited to 600m/s. Performance of a fast valve for propellant gas has been surveyed with relation to differential gas pressure and flow rate of gas, which provides us prospect to improvement up to 1km/s. Further investigation to achieve the initial specification of the pellet velocity remains. In summary, two major goals in the initial objectives to demonstrate high-performance durable pellet injector relevant to high-temperature steady-state plasma operation have been achieved successfully and an issue to increase the pellet velocity has been decomposed to elemental subjects. Less