Calculations of Gas Density in a Closely-Packed Multi-Channel Electrostatic Quadrupole (MESQ) Array

摘要

As a part of our program for developing new accelerators for high-energy negative ion neutral beamlines, we have studied the pumping properties of a MESQ array such as might be interposed between the ion-source/pre-accelerator and a MESQ accelerator. The studies were performed using a two-and-a-half dimensional Monte Carlo code under the assumption of molecular flow, with pumping to be provided by cryopanels on either side of the array. The basic unit treated by the code was a unit cell which could be translated laterally or longitudinally to reproduce the full array. We have studied the behavior of the system as a function of electrode geometry, array size, and cryopanel position. It was found necessary to insert lateral baffles periodically to prevent downstream migration of the gas in the region between the outer edge of the MESQ array and the cryopanels. (ERA citation 08:008867)