Fabrication of a microengineered quadrupole electrostaticlens

A self-aligning method of mounting four parallel cylindrical electrode rods in the geometry of a miniature quadrupole electrostatic lens is described. Pairs of electrode rods are mounted in V-grooves, which are fabricated by anisotropic etching of Si wafers. Two etched dies, separated by further insulating cylindrical spacer rods, comprise a complete lens assembly. For prototype lenses with 500 µm electrode diameter, electrode spacings were maintained to within 3% of their design value, suggesting that this method of construction will allow sufficient precision for such lenses to act as mass analysers in miniaturised quadrupole mass spectrometers.