Numerical simulation of full-aperture-pair ion optics in a miniature ion thruster

M. Nakano, K. Nakamura, Y. Nakagawa, D. Tomita, Y. Takao, H. Koizumi
2018 Physics of Plasmas  
The 211-aperture-pair two-grid ion optics of a miniature ion thruster is numerically simulated. Since the plasma in the miniature ion thruster is too inhomogeneous to introduce mirror or translational boundary conditions between apertures, all the apertures of the grid system are considered. The simulation is self-consistent, the ion current profile in the discharge chamber plasma is given by the particle-in-cell with Monte Carlo collision algorithm calculations, and all the ion beams extracted
more » ... from the full-aperture-pair array were tracked including charge-exchange ions. A scheme for the construction of the full-aperture-pair simulation domain is proposed based on the array of a six-fold hexagonal single-aperture-pair simulation domain, which can be extended to other numbers of aperture pairs. Numerical results on accel impingement current and ion-beam profile are compared to experimental data and shown to be in reasonable agreement. Furthermore, the full-aperture-pair ion-optics model is compared with the single-aperture-pair ion-optics models used in the majority of previous ion-optics simulations, which showed that the full-aperture-pair ion-optics model yielded the most accurate predictions. These results suggest that the ion thruster grid system using an inhomogeneous plasma source can be designed more accurately and effectively using full-aperture-pair ion-optics simulations. Published by AIP Publishing. NOMENCLATURE A down downstream boundary area A up upstream boundary area d a , d s accel and screen grid diameters e elementary charge j ion current density at the upstream surface J a accel impingement current: J a ¼ J ai þ J aCE þ J aEL J a (N xy , N z ) accel impingement current for (N xy , N z ) mesh divisions J aCE accel impingement current due to chargeexchange ions J aEL accel impingement current due to elasticcollision ions J ai accel impingement current due to direct impingement J b beamlet current, defined as the current passing through the ion-acceleration grid system J scl space charge limited current: J scl ¼ 4e 9 ffiffiffiffiffi ffi 2e m Xe
doi:10.1063/1.5008802 fatcat:xacbrsiztfgl5is6qju34pdk3y