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

固体氢芯块注入燃料到聚变等离子体的不可避免性已被广泛认识，然而，芯块注入技术尚未充分建立以满足与反应堆相关的操作能力。该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弹丸注入器。主要目标是：（1）1小时长运行的能力和无限运行持续时间的可行性，（2）超过10赫兹的重复率和超过95%的弹丸发射可靠性，以及（3）超过1.5米/秒的弹丸速度。在原型喷油器中，这3个条件应同时满足。开发中的基本要素是通过螺杆挤出机进行固化和挤出成型，并通过GM制冷机进行冷却，从而实现无液氦操作。从室温到室温，在4小时内达到了足以使氢凝固的低温（10 K）。 关于我们 温度然后以15 mg/s的速率连续凝固1小时。挤出成型为一个棒已经可以在35毫米/秒的速度。在此操作期间，温度升高已被抑制到小于1 K。从杆形成粒料并发射粒料的机构已与螺杆挤出机组合。在10 Hz下连续发射1,000 s，这意味着已经尝试了10，000个弹丸，并且已经证实了完整弹丸发射的可靠性超过99%。至于弹丸速度，最大值已被限制在600米/秒。研究了推进剂气体快速阀的性能与气体压差和气体流量的关系，为推进剂气体快速阀的改进提供了前景。为了达到弹丸速度的初始规格，还需要进一步的研究。总之，在初步目标，以证明高性能耐用的弹丸注入器相关的高温稳态等离子体操作的两个主要目标已经成功地实现，并增加弹丸速度的问题已经分解为基本的主题。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