The effect of magnetic quadrupole lens hysteresis on the focusing of an ion beam with variable energy in a nuclear scanning microprobe

The influence of the hysteresis of magnetic quadrupole lenses on the transverse size of a beam focused on the target in a probe-forming system with a separated Russian quadruplet configuration has been experimentally studied. The measurements were performed in a nuclear scanning microprobe using a proton beam with the ion energy varied within 0.8–1.6 MeV. The beam size was determined by processing the secondary electron emission profiles measured during scanning of a calibrated micrometric square mesh. A new approach is proposed that allows a beam with variable energy in the nuclear microprobe to be focused so as to keep the probe size within preset limits.