CPC H01J 1/34 (2013.01) [H01J 37/073 (2013.01)] | 20 Claims |
1. A photocathode kit comprising:
a photocathode including a substrate on which a photocathode film is formed on a first surface;
a lens which converges excitation light; and
a holder that holds the substrate and the lens,
wherein the holder has
a hollow structure,
a retaining member that retains the photocathode film and the lens to be spaced apart by a predetermined distance, and
a gas vent which is a through hole communicating between inside and outside of the holder to prevent expansion of gas inside the holder in vacuum,
wherein the lens is held in the hollow structure.
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