Fabrication and characterization of field emission points for ion production in Penning trap applications

A series of cold cathode field emission points to be used for electron impact ionization of background gas in Penning trap mass spectrometry applications have been fabricated by electrochemically etching tungsten rod in a NaOH solution. A new variation of the drop-off etching method that can produce tips with tip radii down to 10 nm is described. We present the results of studies in which the parameters used in the etching process were varied, and the geometry and operation of the resulting tips was investigated by imaging them with a scanning electron microscope and by operating them in field emission mode. Finally, the use of these tips in a Penning trap mass spectrometry application is described.