新型高密度直线等离子体发生源研究与实验

Research on high performance Plasma Facing Material (PFM) is the latest in fusion research field. It is a challenge and urgent topic to research the structure and property variation of PFM based on laboratory irradiation simulation with linear plasma generator. As we known, plenty of electron can be emitted by LaB6. Through researches on vacuum heating, heat transmission, electron emitting property, we want to research a kind of plasma generator which plasma density is as high as devices in Japan and USA. As researches in Japan and US as well as Europe shows us, there are two kinds of plasma generators: direct heating type and indirect one. In vacuum environment, plenty of electron can be emitted by LaB6 in 1600 ℃. After excitation by bias voltage, plasma can be generated through the channel restricted by magnetic field, which beam current density could reach 1 E22 m^(-2) s^(-1). We want to have more researches on emission property of LaB6 and plasma excitation condition. By employing of inspection of plasma current density, electron temperature, plasma density, as well as magnetic field with different shape and density, laboratory plasma simulating ITER plasma boundary conditions could be generated properly, as Japan and US have done. And also, more PFM researches could be carried out on it.

高性能面对等离子体材料（PFM）研究是当前聚变研究的前沿热点之一。应用"直线等离子体发生装置"等设备进行实验室模拟辐照条件下PFM的结构和性能的变化是当前一项极具挑战性和紧迫性的研究课题。本基金项目利用极易发射电子的阴极材料LaB6大量发射电子的优点，通过研究高密度直线等离子体发生源的真空加热、传热和电子发射特性，研制出等离子体束流密度可与美日欧洲类似装置达到相同量级等离子体的发生源。高密度等离子体发生源分为阴极直热型和阴极间热型两种。原理是在真空状态下将LaB6加热到1600℃以上，从而使其大量发射电子，用偏压激励产生等离子体，再通过磁场约束形成高密度等离子体束，其束流密度可达到1 E22 m^(-2) s^(-1)以上。本课题将对阴极材料LaB6的发射电子特性以及低温等离子体在此装置内的产生激励条件进行研究，研制出可以正确模拟ITER等离子体边界条件的直线等离子体。

高性能面对等离子体材料（PFM）研究是当前聚变研究的前沿热点之一。由于托卡马克实验条件有限，应用“直线等离子体发生装置（LPD）”等实验室设备进行模拟托卡马克甚至ITER辐照条件下PFM 的结构和性能的变化是当前学术界最前沿的课题。获得可模拟ITER等离子体边界条件的实验室等离子体成为当前一项极具挑战性和紧迫性的研究课题。本课题以高密度直线等离子体热阴极源为对象，进行研究和实验。将大面积圆盘形六硼化镧（LaB6）材料作为初始电子发射基体，采用间热式加热的方法在真空状态下加热到1600℃以上，加直流电压激励等离子体放电。等离子体经过磁场线圈的束径作用后辐照材料样品表面，样品表面加直流负偏压。通过暴露于等离子体中的三探针系统和与样品直接接触的电流表检测等离子体密度与束流密度。实验中等离子体放电稳定运行，实测放电电压随时间呈V形曲线而电流值则呈正相关。测得等离子体电子温度8.66~10.1 eV，束流密度6.3×1022 m^(-2) s^(-1),等离子体密度1.17×1018/m3。热阴极源运行稳定可靠，电子发射持续稳定，六硼化镧（LaB6）材料的碎裂不影响电子的持续发射和等离子体放电。