Fig. 3
From: Fabrication of ion-trap electrodes by self-terminated electrochemical etching
The self-terminated electrochemical etching setup. The tungsten rod is immersed into NaOH solution as anode and can be moved vertically by a computer-controlled translation stages. Two stainless steel (SS) tubes are placed in the beaker, where the larger one produces an etching electric field with circular symmetry, and the small one protects the down-piece when the rod separates into two pieces. The plastic tube surrounding to the down-piece is used to suppress the etching reaction