COMPOSITE CONCENTRIC-GAP MAGNETIC LENS AND DEFLECTOR WITH CONICAL POLE PIECES

摘要

A composite magnetic lens and deflector for particle beam optical systems has a concentric gap and concentric conical lower pole pieces arranged to allow more accurate magnetic deflection. The flux generated by a solenoidal lens coil is shared by magnetically soft inner and higher saturation flux outer pole pieces to minimize saturation effects, while the flux generated by internal deflection coils is confined to magnetically soft inner pole pieces that minimize flux leakage and associated eddy current settling efffects. Shielding rings further contain leakage flux. The inner magnetic circuit is mounted and adhesively bonded to radial flexures to minimize thermal expansion drifts.