基于麦克风的气体超声分子束飞行速度的实验研究  

Experimental study on velocity of supersonic molecular beam based on microphone

作　　者：周茂蕾 刘东[1] 曲国峰 陈桎远 李敏[1] 王艺舟 徐子虚 韩纪锋[1] Zhou Mao-Lei;Liu Dong;Qu Guo-Feng;Chen Zhi-Yuan;Li Min;Wang Yi-Zhou;Xu Zi-Xu;Han Ji-Feng(Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, China)

机构地区：[1]辐射物理及技术教育部重点实验室四川大学原子核科学技术研究所

出　　处：《物理学报》2019年第16期246-253,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11575121);中国国家热核聚变专项(批准号:2014GB125004)资助的课题~~

摘　　要：超声分子束的膨胀和输运过程是一个较为复杂的分子动力学问题,相关的参数较难准确计算.本文基于麦克风测量方法研究了多种气体(H2, D2, N2, Ar, He, CH4)超声分子束在自由膨胀过程中的平均速度及其沿出射方向在远域空间(喷射距离/喷嘴直径>310)的演变情况,获得了较大范围内分子束平均速度分布随气体种类、温度、气压和膨胀距离的变化规律.结果表明, H2, D2, He分子束的速度分别只占各自理论极限速度的54%, 60%和68%,且在远域空间速度下降较快.而CH4, N2和Ar分子束的速度与其各自的极限速度十分接近,占比分别为85%, 92%和99%,且在远域空间速度下降较缓.The expansion and transportation of supersonic molecular beams is a complex process of molecular dynamics, and the related parameters are difficult to calculate accurately. Currently there is no rigorous theory to accurately predict the beam expansion process under specific valve conditions, and current researches are less concerned with the spatial evolution of supersonic molecular beam characteristics over long distance. In addition, time-of-flight mass spectrometry is not well suitable for supersonic molecular beam injection in the field of magnetic confinement fusion. Therefore, based on microphone measurements, the average velocities of several supersonic molecular beams(H2, D2, N2, Ar, He, CH4) in the process of free expansion and their evolutions in the far-field space(flight distance/nozzle diameter > 310) are studied in this work. The variations of velocity distribution with gas type, temperature, pressure and expansion distance are obtained. The results show that the velocities of H2, D2 and He beams account for only 54%, 60% and 68% of their ideal limit velocities, respectively, and their velocities decrease rapidly in the far-field space. The velocities of CH4, N2 and Ar beams are very close to their limit velocities, accounting for 85%, 92% and 99% respectively, and their velocities decrease slowly in the far-field space. And the results show that the velocities of the H2 and D2 beams increase with the source pressure, while the velocities of the other four molecular beams decrease slightly with the source pressure. And it is found that the velocity of supersonic beam without skimmer is negatively correlated with the square root of the molecular mass. For the effect of temperature on velocity, the results show that the velocities of H2 and D2 beams increase with the source temperature but are smaller than their limit velocities at given temperature, and the difference is larger for higher temperature. The results of this experiment provide basic data for controlling the parameters of the supersonic m

关 键 词：麦克风 超声分子束 自由膨胀 速度分布 

分 类 号：O561[理学—原子与分子物理]