As in the diode, a plasma discharge is created within the anode cells upon the application of high voltage to the cathode grid. The ions impinge upon the sputter cathode and dislodge titanium atoms as in the diode. At this point there is a significant difference. Because the cathode grids are open, considerable titanium reaches the pump walls where it cannot be further disturbed by ion bombardment. This has at least two favorable results.
Undisturbed deposits mean less regurgitation of previously pumped gases.
And deposits at the pump wall mean that titanium compounds are kept cooler in the starting mode. A further benefit of the open cathode grid structure is a high production rate for energetic neutral atoms. These energetic neutrals are produced by glancing collisions at the cathode and are readily buried at the pump wall. This burial without reemission accounts for the triode s high speed for noble gases. Last updated April 15, 1998.