Model of Plasma Contactor Performance

A hollow cathode-based plasma contactor will bee own on the international spacestation to control the station’ s potential to within 40 V of the local ionosphere. Extensive testing of the plasma contactor has been conducted in vacuum facilitiesat theNASA LewisResearch Center. Signie cant performance differenceswereobserved between testsofthesameplasmacontactorindifferentfacilities.Whymeasuredplasmacontactorperformancediffersinthe laboratory in different tank environmentsand how the plasma contactor performance measured in the laboratory relatestoexpected performanceinspaceisaddressed. Presented aremodelsof plasmacontactorplasma generation and interaction in a laboratory environment, including anode area limiting. These models were integrated using the Space Station Environment Work Bench to predict plasma contactor operation, and the results are compared with the laboratory measurements. Nomenclature F = gas e ow rate, standard cubic centimeter per minute ID = total orie ce electron current, A Iemission = orie ce current emitted, A Ikeeper = keeper electrode current, A Iloss = ion loss rate, A Imax = maximum possible electron current, A Iprod = total ion production rate, A