Madeev S, Selivanov M, Shagayda A, Lovtsov A
Keldysh Research Centre, Onezhskaya, 8, 125438 Moscow, Russian Federation.
Rev Sci Instrum. 2019 Apr;90(4):043302. doi: 10.1063/1.5090590.
Large-diameter ion-optical systems are widely used in gridded ion thrusters for missions in near-earth space and for deep-space research. Ion sputtering of the accelerator grid is the main factor that limits the thruster's life. The use of carbon-based materials with a lower sputtering rate compared to metal grids allows the thruster to increase its life more than four times. The most resistant to mechanical loads are grids made of carbon-carbon composite materials. Traditionally, ion optics grids use circular-shaped apertures with the centers located in the nodes of the hexagonal pattern. However, with this arrangement of holes, all carbon fibers in the carbon-carbon composite are cut, and this weakens the mechanical strength of the grid. Previously, the Keldysh Research Centre carried out computational studies of a new form of apertures, in which it is possible to preserve uncut fibers and thereby increase the mechanical strength of grids made of carbon-carbon composites. This paper presents the results of a comparative experimental study of the operational characteristics of ion optics with the traditional round shape of apertures and with the new shape of apertures, which are squares with rounded corners. Measurements of the accelerator grid currents depending on the accelerating voltage have shown that both traditional and new ion-optical systems have close perveance limits in which there is no direct ion impingement on the accelerator grid.
大口径离子光学系统广泛应用于近地空间任务和深空研究的栅控离子推进器中。加速器栅极的离子溅射是限制推进器寿命的主要因素。与金属栅极相比，使用溅射率较低的碳基材料可使推进器的寿命延长四倍以上。最耐机械载荷的是由碳 - 碳复合材料制成的栅极。传统上，离子光学栅极使用圆形孔径，其中心位于六边形图案的节点处。然而，采用这种孔的排列方式，碳 - 碳复合材料中的所有碳纤维都会被切断，这会削弱栅极的机械强度。此前，克尔德什研究中心对一种新的孔径形式进行了计算研究，采用这种形式可以保留未切断的纤维，从而提高由碳 - 碳复合材料制成的栅极的机械强度。本文展示了对具有传统圆形孔径和新孔径形状（圆角正方形）的离子光学器件的运行特性进行比较实验研究的结果。根据加速电压对加速器栅极电流的测量表明，传统和新型离子光学系统都有相近的导流系数极限，在这个极限范围内不会有直接的离子撞击加速器栅极。
