Experimental results of microprobe focusing by quadruplet with four independent lens power supplies

Earlier we have proposed the idea in optics of one-stage quadrupole probe-forming systems that consisted in using independent power supplies for all lenses [1]. The new arrangement, in comparison to Oxford triplets and Russian quadruplets, theoretically allows operating in regimes with considerably higher density of ion current. The probe-forming system of the Sumy microprobe has been arranged as a quadruplet with four independent lens power supplies. Current density growth was experimentally verified and sub-micron probe size was obtained, despite the large working distance of 23.5 cm, the moderate beam brightness of 7 A/(m2 rad2 eV) and the energy spread of 10−3. This upgrade did not require changes in the beam-line design.