在线低能气体离子源

材料中氦和氢积累可引起材料性能的恶化甚至失效。为研究材料内氦和氢的存在形式、氦与氢及缺陷的相互作用、气泡的形成和演变过程以及各种因素的影响,建立一套离子束能量最高20keV的潘宁型气体离子源引出和聚焦系统,与200kV透射电镜联机,在离子注入现场原位观察氦和氢不同注入浓度下材料内部的微观结构及变化过程。对离子源进行氦离子的起弧、引出和聚焦测试。离子源在15–60mA放电电流范围内稳定地工作。在5×10–3Pa和1.5×10–2Pa工作气压下,放电电压约380V和320V。低气压下引出离子束流比高气压下大,且引出束流随放电电流和吸极电压的增加而增加。等径三圆筒透镜有显著聚焦作用,在距透镜出口150cm处,离子束流密度提高一个量级以上。能量10keV左右的氦离子获得束流密度约200nA·cm–2的离子束,可满足多种材料进行在线离子注入和原位电镜观测的需要。

An online low energy gaseous ion source

The accumulation of helium and/or hydrogen in nuclear materials may cause performance deterioration of the materials.In order to provide a unique tool to investigate the He-and/or H-caused problems,such as interaction of helium with hydrogen and defects,formation of gas bubbles and its evolution,and the related effects,we designed a low energy(≤20 keV)cold cathode Penning ion source,which will be interfaced to a 200 kV transmission electron microscope (TEM),for monitoring continuously the evolution of micro-structure during the He~+ or H~+ ion implantation.Studies on discharge voltage-current characteristics of the ion source,and extraction and focusing ofthe ion beam were performed.The ion source works stably with 15-60 mA of the discharge current.Under the gas pressure of 5×10~(-3) Pa and 1.5×10~(-2) Pa,the discharge voltage are about 380 V and 320 V, respectively.The extracted ion current under lower gas pressure is greater than that under higher gas pressure,and it increases with the discharge current and extraction voltage.The ion lens consisting of three equal-diameter metal cylinder focus the ion beam effectively,so that the beam density at the 150 cm away from the lens exit increases by a over one order of magnitude.implantation and in situ TEM observation for many kinds of nuclear materials.