Ion beam plume and efflux measurements of an 8-cm mercury ion thruster

Measurements o f the i o n beam plume and e f f l u x cons t i tuents o f an 8-cm mercury i o n th rus ter have been c a r r i e d out i n the TRW 5 x 10 f o o t t e s t i n g chamber. Charged components ( ion beam plume) were measured w i t h an array of movable p o s i t i o n Faraday cups and re ta rd ing p o t e n t i a l analyzers y i e l d i n g both cur ren t densi ty and p a r t i c l e energy determinat ions. Neutral components ( i o n beam e f f lux ) were determined w i t h a movable p o s i t i o n i o n i z a t i o n gauge. Measurements of the i o n beam plume were performed for a t h r u s t e r both w i t h and w i thout a sput te r sh ie ld . e f f l u x e s has been c a r r i e d o u t and has been appl ied t o an example c a l c u l a t i o n of e f f l u x c o m p a t i b i l i t y w i t h a comnunications spacecraft. I . In t roduc t ion The use o f ion th rus ters fo r s t a t i o n keeping and a t t i t u d e cont ro l o f spacecraft w i l l requi re , i n general, t h a t on ly a l i m i t e d s o l i d angle o f d i rect ions from the spacecraft may be occupied w i t h the plume from the t h r u s t e r and t h a t the remaining s o l i d angle o f d i rec t ions w i l l be occupied w i t h other com onents (e.g., so la r ar ray panels, antennae and booms7 o f t h a t spacecraft. I n o r d e r t o successf u l l v in teara te the i o n t h r u s t e r i n t o the m a w Analysis o f data i n terms of normalized c r a f t f o r ihese described appl icat ions, i t 'is-necessary t h a t there be a d e t a i l e d evaluat ion of the d i rec t ions and the magnitudes o f the various charged and neut ra l p a r t i c l e s released by the thruster . This paper presents such an evaluat ion of the plume and e f f lux o f an 8-cm e lec t ron bombardment mercury ion th rus ter . t i e s , the various charged p a r t i c l e species i n the plume are described and the normalized e f f l u x parame te rs f o r those species are defined. t i o n i s a lso given o f the i o n t h r u s t e r spu t te r sh ie lds which are used t o provide s p e c i f i c a l l y low e f f l u x regions f o r the l o c a t i o n o f sens i t i ve spacec r a f t surfaces. given fo r a t h r u s t e r both w i t h and w i thout such a s p u t t e r sh ie ld . example c a l c u l a t i o n o f e f f l u x c o m p a t i b i l i t y o f an i o n thruster , a c t i n g as a north-south s t a t i o n keeper, on a three-axis s t a b i l i z e d communications spacecraft. Before prov id ing the measured ion beam proper-