The copper coil has outer and inner diameters of 2.4mm and
0.6mm respectively. It is wound with 25µm diameter copper
wire achieving 600 turns and a resistance of ~100Ω. The coil is
bonded directly to a purpose made base machined from
Tecatron GF40, a hard easily machineable plastic that can
provide a rigid clamp for the beam. The inertial mass is
maximised within the given volume by using wire eroded high
density tungsten blocks.
Four Neodymium Iron Boron (NdFeB) magnets are bonded to
the two tungsten masses again increasing the inertial mass
within the volume. NdFeB rare earth permanent magnets have
the highest flux density of any commercially available magnets.
In addition, zinc coated mild steel (Zintec) keepers are bonded
to the magnets to act as flux guides completing the magnetic
flux circuit. The beam in this study was etched from a sheet of
50µm thick beryllium copper. Stainless steel and silicon beams
have also been employed with this design, the results of which
have been previously reported elsewhere [4,5].