A new approach to gas field ion sources

A new approach to gas field ion sources is described. It is based on a structure made by inserting a field emission tip inside a small diameter tube. The tube supplies gas to the tip from a high-pressure chamber into a high-vacuum chamber where ionization takes place. Comparison of projection electron and ion micrographs shows that ionization results from a field ionization process taking place at the very end of the tip. Emission currents in the 10 nA range, for a few kV emission voltages, are obtained with various gases including neon, air and hydrogen. Lifetime experiments with H2 show stable emission for days.