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气固双等离子体离子源的实验中,在一定吸极电压下,观察到从离子源引出的离子束在吸入口处是收敛的(见图1)。束的截面在吸极口内有极小值,常称为束腰。离子束过吸极口后进入等电位区漂移前进。按图1所示,沿轴向移动法拉第筒,测得引出束流强度I_o~+与位移L的关系曲线如图2所示。从图2中可以看出,I_o~+随L的增加衰减很快;显然,如果束的散角很小,I_o~+随L的增加衰减会慢些。这个规律与近似估算公式:
In the experiment of gas-solid dual plasma ion source, it is observed that the ion beam extracted from the ion source is convergent at the suction inlet under a certain electrode voltage (see FIG. 1). The cross section of the beam has a minimum inside the nozzle port, often called the beam waist. Ion beam over the suction port into the isoelectric area drift forward. Shown in Figure 1, along the axial movement of the Faraday cup, measured the intensity of the extracted beam I_o ~ + displacement L of the relationship shown in Figure 2. It can be seen from Fig. 2 that I_o ~ + decays rapidly with the increase of L; obviously, if the angle of divergence of the beam is small, the attenuation of I_o ~ + with L will be slower. This law and approximate estimation formula: