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采用单孔引出系统的Moak型高频直流源,要引出十几毫安的离子流,必须选取孔道直径较粗长度较短的吸极,提高高频振荡器的输出功率和引出电压,但是,在上述情况下,会导致源的气耗量迅速的增加;使源的散热问题变得突出并降低源的功效;往往也会增加吸极的热负荷,降低源的工作寿命,为克服上述困难,有人曾采用过多孔引出系统。 由于源的气耗量正比于(2X_2)~3/L,输出流强正比于(2X_2)~2/L~2,这里,2X_2和L分别是吸极孔道的直径和长度,所以和单孔引出相比,采用多孔引出具有以下优点:在不增加源的气耗量(即多孔源的气耗量和单孔源等效)的情况下,可获得较大的离子流,相应地降低对振荡器输出功率和引出电压的要求;可以改善离子流密度沿束截面的分布(即由高斯分布改善为准矩形分布),当束流用作轰击核靶时,有利于改善靶子热负荷的均匀性;可以降低束流的体电荷效应,从而改善束流的发射度。
The Moak-type high-frequency DC source with a single-hole extraction system needs to extract a few milliamps of ion current, and the shorter diameter of the channel must be selected to improve the output power and the output voltage of the high-frequency oscillator. However, Under these circumstances, the gas consumption of the source will rapidly increase; the source cooling problem will become prominent and the source efficiency will be reduced; the heat load of the sink will also be increased and the working life of the source will be reduced. In order to overcome the above difficulties Someone once used a porous lead-out system. Since the source gas consumption is proportional to (2X_2) ~ 3 / L, the output flow is strongly proportional to (2X_2) ~ 2 / L ~ 2, where 2X_2 and L are the diameters and lengths of the suction channels respectively. Compared with the introduction of porous leads has the following advantages: Without increasing the amount of gas consumption of the source (ie, porous gas source gas consumption and single-hole equivalent), the larger ion current can be obtained, Oscillator output power and draw-out voltage; the distribution of ion flux density along the beam cross-section can be improved (that is, from Gaussian distribution to quasi-rectangular distribution); when the beam is used as a bombardment nuclear target, it is beneficial to improve the uniformity of target thermal load ; Can reduce the body charge effect of the beam, thereby improving the beam emission.