Vacuum encapsulated, high temperature diamond amplified cathode capsule and method for making same

A method for fabricating a diamond amplified cathode capsule for generating an electron beam of secondary electrons, the method comprising:

• providing a cathode element having a primary emission surface adapted to emit primary electrons;
• providing an annular insulating spacer;
• providing a diamond window element comprising a diamond material and having a secondary emission surface adapted to emit secondary electrons in response to primary electrons impinging on the diamond window element;
• stacking a first high-temperature solder blank between the diamond element and the annular insulating spacer;
• heating the first high-temperature solder blank under vacuum to form a weld between the diamond element and the annular insulating spacer thereby forming a welded diamond element and annular insulating spacer sub-unit;
• stacking a second high temperature solder blank between the cathode element and the welded diamond element and annular insulating spacer sub-unit;
• sealing off the diamond element from the second high temperature solder blank;
• and
• heating the second high temperature solder blank under vacuum to form a weld between the cathode element and the welded diamond element and annular insulating spacer sub-unit, thereby forming a vacuum encapsulated, diamond amplified cathode capsule with a hermitically sealed chamber defined therein,
• wherein the diamond element is protected from out gassing from the second high temperature solder blank during said second heating due to said sealing off of the diamond element.