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4.2 K以下的加压液氦（HE）中以及在4.2 K，1 atm附近的低压液氦（HE）中进行了高压脉冲放电，在380 nm至720 nm的波长区域中进行了光谱研究。结果表明，由于较厚的瞬态等离子体在低温环境中的存在引起的鲜明作用，众所周知的中性He原子线被极大地扩展。脉冲放电后的血浆密度高达5x10E18/cc。最高电子温度为35,000 K观察线与各种光谱线周围的连续强度比。在相同的实验条件下，在室温下，温度比气态排放案件低几倍。被超流体包围的等离子体在排放后很长一段时间是低温等离子体。根据获得的血浆参数，库仑耦合系数约为0.1，比在室温下的常规气态放电值大5倍。在目前的重新仪上，这是第一次澄清的。在中性HE原子线外，在430 nm和395 nm附近观察到了两组强烈的光谱线。前者被确定为分子的旋转旋转 - 振动转变，而后者尚未在以前的文献中报道，并且目前尚不清楚排放的起源。提出了一种在低温环境中的分层等离子体模型来解释实验结果。这强调，本研究中的低温等离子体涉及将来需要研究的各种未知现象。