An Electrode With Molybdenum-Cathode and Titanium-Anode to Minimize Field Emission Dark Currents

A series of dark current measurements are performed for Molybdenum (Mo) and Titanium (Ti) electrodes, and the results are analyzed to separate the primary field emission current from the total observed dark current. The analysis shows that Mo exhibits very low primary field emission current as a cathode, and Ti also exhibits a lower enhancement effect of dark current due to electron and ion bombardments of cathode and anode. An electrode configuration with Mo cathode and Ti anode is thus examined, and it is confirmed that a field gradient of as high as 130 MV/m for 1 nA total dark current is possible for an electrode gap of 0.5 mm and an effective cathode area of 7 mm.