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Measurements of Cryogenic Plasma in Pressurized Superfluid Liquid Helium Using Pulsed Discharge Method

脉冲放电法测量加压超流液氦中的低温等离子体

基本信息

批准号：
08680499
负责人：
MINAMI Kazuo
金额：
$ 1.54万
依托单位：
NIIGATA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08680499/
关键词：
Liquid Helium Pulsed Discharge Line Spectrum Stark Broadening Superfluid Multichannel Detector Strongly Coupled Plasma Electron Bubble マルチ・チャンネル検出器シュタル広がり

项目摘要

High voltage pulsed discharges in pressurized liquid helium (He) below 4.2 K,as well as cryogenic helium gas near 4.2 K,1 atm, are spectroscopically studied in a wavelength region from 380 nm to 720 nm. The results demonstrate that well-known neutral He atomic lines are extremely broadened due to Stark effects caused by the presence of thick transient plasmas in cryogenic environment. The plasma density just after the pulsed discharges attains to be as high as 5X10E18/cc. The maximum electron temperature is measured to be 35,000 K observing line to continuum intensity ratios around various spectral lines. The temperature is several times lower than the gaseous discharge cases at room temperature under identical experimental condition. The plasmas surrounded by superfluid He are concluded to be cryogenic plasmas long after the discharges. According to the plasma parameters obtained, the Coulomb coupling coefficients are around 0.1 that is 5 times larger than the values in conventional gaseous discharges in room temperature. This fact is clarified for the first time in the present reseaech.In addition to the neutral He atomic lines, two series of strong spectral lines without broadening are observed near 430 nm and 395 nm. The former is identified to be from rotaional-vibratinal transitions of diatomic He molecules, whereas the latter was not reported in previous literatures and the origins of the emissions are not understood at this moment. A stratified plasma model in cryogenic environment is proposed to explain the experimental results.It is emphasized that the cryogenic plasma in the present study involves various unknown phenomena to be studied in future.

在380~720 nm波长范围内，对4.2K以下加压液氦(He)高压脉冲放电和4.2K、1大气压附近低温氦气高压脉冲放电进行了光谱研究。结果表明，在低温环境中，由于厚的瞬变等离子体的存在而引起的斯塔克效应，使大家熟知的中性氦原子谱线极大地展宽。脉冲放电后的等离子体密度高达5×10E18/cc。测得最高电子温度为35000K观察线与各谱线周围的连续谱强度比。在相同的实验条件下，温度比常温下气体放电的温度低好几倍。被超流体包围的等离子体在放电后很长一段时间内被认为是低温等离子体。根据得到的等离子体参数，库仑耦合系数约为0.1，是常规气体放电室温下库仑耦合系数的5倍。本研究首次阐明了这一事实。除了中性He原子谱线外，在430 nm和395 nm附近还观察到了两组没有展宽的强谱线。前者被认为来自双原子氦分子的旋转-振动跃迁，而后者在以前的文献中没有报道，而且目前还不清楚发射的来源。提出了一个低温环境下的分层等离子体模型来解释实验结果，并强调了本研究中的低温等离子体涉及到未来有待研究的各种未知现象。