Experimental Investigation of Lower-Hybrid Solitons Using a Large-Volume, High-Density Helicon-Plasma Source

1. ISAS/JAXA（日本宇宙航空研究开发机构下属的空间宇宙科学研究所）研制出了一种大体积螺旋等离子体装置（直径74厘米，长度486厘米，B_<max> = 2 kG）。该装置采用直径43厘米、4圈的大型平面螺旋天线，能够产生世界上体积最大的螺旋等离子体，n_e（大于或等于）10^<12> cm^<-3>，中等射频输入功率为~ 500 W（小于或等于）2 kW)。利用该装置，可以通过(1)改变天线附近的磁场结构和(2)改变天线的辐射场方向图来控制径向密度分布。东海大学开发了另一种螺旋等离子体装置（直径20厘米，长度100厘米，B_<max> = 0.6 kG），专门用于激发大振幅低杂合波。该装置采用了一种特殊设计的分段多环路天线，用于等离子体产生和波激发。在ISAS/JAXA，尝试使用轴向长栅格天线在沿轴方向的预制作的低密度通道内激发低混合（LH）腔模式。腔本征模的激发尚未得到证实。在东海，为了使用多环天线的外部部分作为激振器来激发LH孤子，已经开始了一系列的实验。在未来的实验中，将尝试观察与LH孤子相关的局域场对等离子体离子的跨场加速。

1. A large volume helicon-plasma device (74 cm in diameter, 486 cm in length, and B_<max> = 2 kG) has been developed at ISAS/JAXA (the Institute of Space and Astronautical Science, a division of the Japan Aerospace Exploration Agency). With the use of a large flat-spiral antenna (43 cm in diameter, 4 turns), the device is capable of producing a world-largest-volume helicon-plasma of n_e 【greater than or equal】 10^<12> cm^<-3> with moderate rf input power of 〜500 W for Ar (【less than or equal】2 kW for He).2. With this device, it is possible to control the radial density profile by (1) changing the magnetic-field configuration near the antenna and (2) changing the antenna radiation-field patterns.3. Another helicon-plasma device (20 cm in diameter, 100 cm in length, and B_<max> = 0.6 kG), which is specialized to excite large amplitude lower-hybrid waves, has been developed at Tokai University. The device utilizes a specially designed segmented multi-loop antenna for both plasma production and wave excitation.4. At ISAS/JAXA, it was attempted to excite lower-hybrid (LH) cavity modes inside a pre-produced low density channel along the axis by using an axially long grid-antenna. The excitation of cavity eigen-modes has not been confirmed yet.5. At Tokai, a series of experiments has been initiated in order to excite LH solitons using an outer part of the multi-loop antenna as an exciter.6. In the future experiment, it will be attempted to observe cross-field acceleration of plasma ions due to localized fields associated with LH solitons.