A Critical Review of Orificed Hollow Cathode Modeling: 0-D Models
A critical review of zero-dimensional orificed hollow cathode modeling is presented, with a focus on the validity of model assumptions, the reproducibility of model results, and the observed scaling behaviors. Complete models were capable of recreating the original results of their authors, but were generally unable to produce agreement with other experimental data. Resolution of the potential structure of the emitter sheath beyond the inclusion of the pre-sheath is attempted in only one model. In all other models it is assumed that the plasma and sheath potentials are equal, inflating the contribution of emitter ion bombardment and power deposition in the insert plasma by sheath electrons while essentially neglecting electron back-bombardment. Model results are generally sensitive to the internal neutral pressure, but neutral flow predictions do not agree with experimental data. Inconsistent property data and the inappropriate evaluation of flux terms between control volumes are pervasive, and introduce significant errors. Most models require substantial input in the form of experimental data or free parameters and cannot be used for predictive calculations.