Diagnosis of plasma in high current laser ion source
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摘要: 强流激光离子源是最有希望为重离子聚变直线感应加速器提供离子的离子源之一。离子源内等离子体决定了离子源性能和引出品质，为了了解强流激光离子源内等离子体参数，采用发射光谱和ICCD成像的方法对该离子源中的等离子体进行了诊断。该离子源由一台四倍频的266 nm Nd:YAG激光器和Cu靶组成，激光束经过透镜聚焦后照射在Cu靶上产生等离子体，激光打靶能量密度约为108 W/cm2，持续时间15 ns。ICCD相机拍摄了激光照射后等离子体的膨胀过程，初始时刻等离子体垂直表面喷射，膨胀速度约为1 cm/s。光谱仪测量了离子发射光谱，谱线主要由Cu原子的Cu Ⅰ谱线和Cu+离子的Cu Ⅱ谱线组成。采用Boltzmann图法得到膨胀等离子体电子激发温度约为1 eV，采用Stark展宽法得到电子密度约为1016 cm-3。Abstract: Plasma characteristics are key parameters of ion source. The characteristics of plasma in high current laser ion source are diagnosed by optic emission spectroscopy and an ICCD camera. The plasma is produced by a quadruplicated frequency Nd: YAG laser irradiating Cu target. The laser energy density is about 108 W/cm2, and the duration time is 15 ns. The plasma expansion progress is captured by the ICCD camera, which shows the expansion velocity is about 1 cm/s. Meantime the plasma emission spectra are measured by a spectrograph, which are mostly Cu Ⅰ spectra from Cu atoms and some weakly Cu Ⅱ spectra from Cu+ ions. Electron temperatures are got by Boltzmann plot and they are about 1 eV. Electron densities are got by Stark broadening and they are about 1016 cm-3.
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