Computation of Ion Collection by a Rocket-Mounted Mass Spectrometer in the Limit of Vanishing Debye Number.

摘要

Self-consistent calculations are made of the ion current density at the central point (orifice) of an electrically charged mass-spectrometer plate mounted on a rocket,in the limit of zero Debye number (Debye length divided by plate radius). In this limit,the plasma sheath containing the bulk of the potential drop is of zero thickness,but there is generally also a 'presheath'of finite extent. The presheath is determined by quasineutrality,and its structure is (a) independent of plate draw-in potential and Debye number,and (b) dependent on the ion Mach number. The presheath electric field enhances the current collected,by an enhancement factor which depends inversely on Mach number,but which is independent of plate potential and Debye number. A method is suggested for extending the zero-Debye-number solutions in the regime of small but finite Debye numbers. (Modified author abstract)