以巨脉冲红宝石激光为光源的Mach-Zehnder干涉仪应用于θ收缩等离子体的研究

本文应用巨脉冲红宝石激光为光源的Mach-Zehnder干涉仪,研究了23kJ(千焦耳)“θ收缩”(θ-pinch)等离子体的电子密度、形状和不稳定性。从轴向干涉图的照片获得45至120mTorr(毫乇)氘气压范围的二维电子密度分布和电子密度的峰值在6×10¹⁶—2.3×10¹⁷cm^-3范围。等离子体最大收缩出现在主压缩磁场的第一个半周期的1/3附近,在等离子体的最大收缩附近的特征约束时间(粒子数衰减1/e的时间)为1.8—4.3μs,具有负偏磁场的干涉图显示在等离子体中捕获了偏磁场。从这些干涉图的照片上还看到等离子体在主压缩磁场和等离子体捕获场之间作径向磁流体振荡。干涉图照片还表明,在45至80mTorr氘气压范围内,等离子体在主压缩磁场的第一个半周期内基本上都是稳定的。

THE STUDY OF θ-PINCH PLASMA USING A MACH-ZEHNDER INTERFEROMETER ILLUMINATED BY A GIANT PULSED RUBY LASER

The plasma electron density, shape and instability of the 23 kJ θ-pinch have been studied through the use of a Mach-Zehnder interferometer with a giant pulsed ruby laser illumination. The axial interferograms in the range of 45-120 m Torr deuterium pressures gave two-dimensional electron density distributions for the dicharge and established peak plasma electron densities in the range of 6-10¹⁶-2.3·10¹⁷ cm^-3 for the plasma at peak pinch. The time of the peak pinch was about 1/3 of the first half-cycle of the main compressive magnetic field. The plasma characteristic time of containment (time required for the number of particles to be reduced to 1/e) close to peak pinch was 1.8-4.3μs. The interferograms with reverse bias magnetic field showed that the bias magnetic field was trapped in the plasma, and revealed that radial hydromagnetic oscillation of the plasma occurred between the trapped magnetic field and the main compressive magnetic field. The interferograms also showed that the plasma is essentially stable during the first half-cycle of the main compressive magnetic field in the range 45-80 m Torr deuterium pressures.