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石油勘探测井中小型中子管由于其外径小、内部结构复杂和高中子产额,要求离子源引出的束流在靶上的轰击面积尽可能大。对几种不同的中子管离子源引出结构进行了软件仿真和验证试验。要使中子管在不同靶压下影响减小并稳定工作,需要考虑屏蔽靶压电场对离子源放电的影响;对引出孔结构和离子束流在加速空间的运行轨迹进行计算和仿真,改变离子源引出孔结构能相应调整离子束流在靶上的轰击面积;离子源引出孔由1个大孔改为多个小孔,靶压电场对多孔离子源内部放电基本没有影响,与大孔源相比,离子引出比例低,但稳定性要好,在相同离子流(100μA)情况下,多个小孔管引出的靶流只有1个大孔管的50%左右;而在相同靶流(20μA)和相同靶压下,多个小孔管离子源的中子产额比1个大孔管的离子源的中子产额要高20%左右。计算仿真的结果和试验吻合好,经试验验证其中子管工作稳定,中子产额提高,达到了设计目的。
Due to its small outer diameter, complicated internal structure and high-neutron yield, small and medium-sized neutron tubes for petroleum exploration and logging require that the bombardment area of the beam induced by the ion source be as large as possible on the target. Several different neutron tube ion source extraction structures were simulated and verified by software. In order to reduce the influence of neutron tube under different target pressures and stabilize the work, the influence of the shielding target voltage field on the discharge of the ion source needs to be considered; the trajectory of the extraction hole structure and ion beam in the acceleration space is calculated and simulated, Changing the structure of the ion source extraction hole can adjust the ion bombardment area of the ion beam accordingly. The ion source extraction hole is changed from one large hole to multiple small holes, and the target piezoelectric field basically has no influence on the internal discharge of the porous ion source. Compared with the macropore source, the ion extraction ratio is low, but the stability is better. In the case of the same ion current (100μA), the target flow from multiple orifice tubes is only about 50% of one macroporous tube. The neutron yield of multiple orifice source was about 20% higher than that of one orifice source at flow rate (20μA) and the same target pressure. The results of calculation and simulation are in good agreement with the experimental results. The experimental results show that the tube works steadily and the neutron yield increases, reaching the design goal.