Triode Pumps

Triode

 Pumps use reverse electrical polarity and a radically different cathode design to achieve two important advantages over the diode pumps: (1) an electrically isolated cathode allows the starting glow discharge to be confined at significantly higher pressures, resulting in shorter starting times; (2) the sputter cathode design allows noble and non-noble gases sputtering. Triodes have the highest speeds for noble gases and freedom from argon instability in the event of an air leak. Disadvantage: because of the sputter cathode design, the triode pumps require more frequent service.