Phenomena associated with the interaction of high energy ions and solid surfaces under conditions relevant to ion rocket operation have been investigated. The number of target atoms removed per incident ion, or sputtering ratio, has been determined for xenon and argon ions incident on copper, tungsten, molybdenum, sili¬con and titanium with energies from 1,500 to 39,000 electron volts and at incidence angles from 2° to normal incidence. The effect of target temperatures, both high and low, on the sputtering ratio has been investigated. The ratio of secondary particles produced to incident ions, along with their energy and angular distri¬bution, has been investigated as functions of ion energy and incidence angle. Areas investigated for the first time in this program include:n(1) Sputtering and secondary emission for very low angles of ion incidence, and effects of surface roughness.n(2) The energy and angular distributions of secondary particles as a function of bean incidence angle.n(3) Sputtering and secondary emission of surfaces at reduced temperatures.nAnalysis of theoretical concepts of sputtering and existing empirical data have led to recommendations of likely materials for ion rocket use. A bibliography of relevant papers has also been compiled.
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