Magnetic Confinement of Cryogenic Plasma Produced by Pulsed Discharges in Superfluid Liquid Helium

超流液氦中脉冲放电产生低温等离子体的磁约束

• 批准号: 12680475
• 负责人: MINAMI Kazuo
• 金额: $ 1.98万
• 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: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12680475/
• 关键词: Liquid Helium; Superconducting Coil; Pulsed Discharge; Stark Broadening; Magnetic Confinement; Mirror Field; Cusp Field; Needle Electrodes; 超伝導マグネット; 超流動; 極低温; プラズマ; 磁場閉じ込め; ミラー磁界; カスプ磁界; 磁気圧

The effect of magnetic confinement has been investigated on the density decay of afterglow plasma produced by pulsed discharges between needle electrodes embedded in a split type superconducting coils with maximum magnetic field 2 T immersed in superfluid liquid helium (LHe). A pair of needle tungsten electrodes in mirror- or cusp-types magnetic field in LHe are fired by high voltage pulses of 20 kV, current 50 A, and time width 1.0μs. The Stark broadening of spectral line 587.6 nm from neutral helium atoms in plasma is observed to measure local plasma density. At time t=0.5μs after the discharge, the plasma density n=10^<18>cm^<-3>, and electron temperature Te=32,000 K. For a period until t=3.0μs after the dischagges, the estimated beta value defined by the ratio of plasma and magnetic pressures changes from 0.28 to 0.014. Effects of applied magnetic field are assumed to be evident. Somewhat surprisingly, no changes in density decays with and without magnetic field can be detected until t=3.0μs for both mirror- and cusp-type cases. We observe total light intensity until t=18 ms for detecting the difference. No differences with and without the magnetic field are detected. Reducing the pressure and temperature of LHe results in no difference.

研究了磁约束对超流液氦(LHe)中最大磁场为2T的分离型超导线圈中针状电极间脉冲放电产生的余辉等离子体密度衰减的影响。用20kV、电流50A、脉宽1.0μ的S高压脉冲激发出镜面或尖点型磁场中的一对针状钨电极，观察到等离子体中中性氦原子对587.6 nm谱线的斯塔克展宽，以测量局域等离子体密度。在放电后时间t=0.5时，等离子体密度n=10μ；18；cm；-3，电子温度Te=32,000K，直到放电后t=3.0μS，由等离子体和磁压之比定义的估计贝塔值从0.28变化到0.014。假设外加磁场的影响是明显的。有些令人惊讶的是，对于镜型和尖型情况，直到t=3.0μS，才能检测到有磁场和无磁场时密度衰变的变化。我们观察总的光强度，直到t=18ms，以检测差异。没有检测到有无磁场的差异。降低LHe的压力和温度，结果是没有差别的。

项目成果

K. Minami, Y. Yamanishi, C. Kojima, M. Shindo and O. Ishihara: "Very Slowly Decaying Afterglow Plasma in Cryogenic Helium Gas"IEEE Transactions Plasma Sciene. vol.31,no.3(in printing). (2003)

K. Minami、Y. Yamanishi、C. Kojima、M. Shindo 和 O. Ishihara：“低温氦气中缓慢衰变的余辉等离子体”IEEE Transactions Plasma Sciene。

E.Minami, Y.Yamanishi, C.Kojima, M.Shindo, O.Ishihara: "Very Slowly Decaying Afterglow Plasma in Cryogenic Helium Gas"IEEE Transactions Plasma Science. 31(印刷中). (2003)

E. Minami、Y. Yamanishi、C. Kojima、M. Shindo、O. Ishihara：“低温氦气中缓慢衰变的余辉等离子体”IEEE Transactions Plasma Science 31（出版中）。