Ion beamlet steering by aperture displacement for a tetrode accelerating structure

Steering of a single beamlet of ions in a tetrode accelerating structure as a function of both aperture displacement and the ratio of acceleration to extraction voltage (Gamma) has been measured, and the results are compared to the steering predicted by a modified linear theory. Although the data contain the predicted features of (1) null steering for a particular value of Gamma and (2) a directional change in steering through this point, the steering was also observed to be nonlinear in nature. A conjecture as to the cause of this nonlinearity is given, and the implications of these findings to beamlet steering in a multibeamlet source are discussed.