profile is varied during a scan cycle to attain a minimum value at the radially outermost point s on target 60 reached by impingement spot 14 during its displacement along scan path 200 and a maximum where impingement spot 14 is at its radially innermost point along that scan path 200 the alternate embodiment of actuator 40 shown in fig4 represents one exemplary means by which such sinusoidal profile may be effected note that scan path 200 may extend substantially across the diametric extent of target traversing rotation axis x 0045 fig3 c graphically illustrates examples of substantially sinusoidal displacement profiles that may be employed in an exemplary embodiment of the present invention as there shown the instantaneous linear position of impingement spot 14 in proportional units relative to the target 39 s rotation axis x is plotted against the corresponding instantaneous angle values within one complete cycle of the given scanning action curve 210 simply represents for referential purposes the cosine curve defined by the angle values within the scan cycle shown similarly curve 212 effectively represents the ideal case u2014 that is where optimal target wear is realized given an infinitesimally small impingement spot 14 scanned through a path traversing the target 39 s rotation axis x curves 214 and 216 profile exemplary scanning actions that may be effected in accordance with the present invention with l.