Optimal Parameters of High Energy Ion Microprobe Systems Comprised of Oxford Lenses

Focusing of ion beams of MeV energy until now has been mostly accomplished by magnetic quadrupole lenses in different configurations: doublet, triplet, quadruplet and quintuplet. Many focusing systems are two-parametric focusing systems, i.e., systems having two field parameters (two excitations). The simplest two parametric focusing system, other than the doublet, is a two parametric triplet which can consist of two different configurations: (1) an Oxford configuration in which the focusing (F) and defocusing (D) capabilities of the lenses in one plane alternate F-D-F whereas the lens strengths are ordered as A-A-B, and (2) a triplet in which the focusing and defocusing capabilities of the lenses in one plane also alternate F-D-F but the lens strengths are ordered as A-B-A. Experimental results of a comparison of system parameters for these two focusing configurations, including demagnifications, magnet current, and slit settings will be shown. Both configurations utilized the Oxford Microbeams, Ltd. 10 cm long magnetic quadrupole lenses.