论文部分内容阅读
液态金属离子源是由场致发射理论和电气流体力学理论相结合而发展起来的一种高亮度离子源。在发射体针尖端顶部曲率半径为微米数量级的发射体上,浸润上液态金属,在电场作用下,尖顶处的液态金属膜发生畸变,若电场足够强,液态金属就会发射出离子,而源池中的液态金属便会沿着发射体的针杆流到尖顶以维持连续发射。Taylor指出在发射体尖端上的液态金属同时受到两种力的作用:一是静电力作用;二是表面张力作用,这两种力的作用方向相反,当两者达到平衡时,在针尖端点处形成一个顶角为98.6°的圆锥体,这就是离子发射区,称为Taylor锥。它的形成是液态金属离子源稳定发射的关键,由于液态金属离子源(LMIS)发射体针尖非常细小,用一般的测量方法是无法准确测量针尖温度的,通常人们只能估计针尖最佳温度值为500℃左右。作者采用模拟方法测量针尖温度。方法如下:对照实测的发射体,去除引出电极,Einzol电极和接收靶,制作一个尽量相似的模拟发射体,其针尖比实用针尖粗一些,便于点焊热电偶,整个装置置于一真空室内,给加热钨丝通不同电流,热平衡后,上下两端热电偶有对应输出电压,这样,我们只要知道实用发射体发射时针尾的热电偶输出值,便可得到针尖温度。
Liquid metal ion source is a combination of field emission theory and the theory of electro-hydrodynamics developed a high-brightness ion source. Liquid metal is infiltrated onto a projectile whose radius of curvature on the top of the needle tip is on the order of microns. The liquid metal is distorted by the electric field and the liquid metal will emit ions if the electric field is strong enough. Liquid metal in the pool will flow along the emitter’s needle bar to the apex to maintain continuous emission. Taylor pointed out that the liquid metal on the tip of the projectile is subject to two forces at the same time: one is the electrostatic force; the other is the surface tension, the two forces acting in the opposite direction, when the two reached equilibrium, at the tip of the needle The formation of a cone angle of 98.6 ° cone, which is the ion launch area, known as the Taylor cone. Its formation is the key to the stable emission of liquid metal ion source. Due to the very small needle tip of the liquid metal ion source (LMIS), it is impossible to accurately measure the tip temperature with the common measurement method. Usually, one can only estimate the optimum tip temperature About 500 ℃. The authors used a simulation method to measure the tip temperature. The method is as follows: Controlled the measured emitter, remove the lead electrode, Einzol electrode and the receiving target to make a simulated simulator as similar as possible, the tip of the probe is thicker than the practical tip, which is convenient for spot welding the thermocouple, the whole device is placed in a vacuum chamber, Different current to the heating tungsten wire, thermal equilibrium, the upper and lower ends of the thermocouple has a corresponding output voltage, so that we only know when the practical emitter launcher thermocouple output value, you can get the tip temperature.