Photocathode high-frequency electron-gun cavity apparatus

A photocathode high-frequency electron-gun cavity apparatus structured with a BNL high-frequency acceleration cavity, comprising:

• a high-frequency acceleration cavity including a plurality of cavity cells and at least one iris extending between the plurality of cavity cells to connect the plurality of cavity cells, each of the plurality of cavity cells having a curved surface shape formed with any of a trigonometric-function curved line, an arc, an oval, and a parabola on an inner face thereof such that the inner face of the each of the plurality of cavity cells has a smooth and curved surface shape approaching to a standing wave waveform suitable for an acceleration high-frequency high-electric field;
• a photocathode which is arranged at an end part of the high-frequency acceleration cavity;
• a laser entering port which is arranged at a position facing the photocathode behind an electron beam extraction port of the high-frequency acceleration cavity arranged at another end part and from which laser light is entered into the high-frequency acceleration cavity to be supplied to the photocathode;
• a high-frequency power input coupler port which is arranged at a side surface part of the high-frequency acceleration cavity and from which high-frequency power is input into the high-frequency acceleration cavity;
• a vacuum exhaust port which is arranged at the side surface part of the high-frequency acceleration cavity and from which the high-frequency acceleration cavity is vacuum-exhausted;
• and
• a high-frequency resonant tuner which is arranged at a side of the high-frequency acceleration cavity and which adjusts a high-frequency resonance frequency at the plurality of cavity cells,
• wherein the inner face of the each of the plurality of cavity cells is formed only with the curved surface shape without having a sharp angle part,
• each curved surface shape at a vicinity of a top section of the each of the plurality of cavity cells and the at least one iris are formed with arcs, respectively, and each curvature radius R thereof is in a range between 5 and 20 mm inclusive,
• surface roughness of the inner face of the each of the plurality of cavity cells is 0.05 μm or less, and
• wherein the photocathode is a photocathode plug having a conductive RF contactor at a section in contact with the high-frequency acceleration cavity and having a Cs2Te cathode face, and
• the high-frequency resonant tuner is a non-insertion high-frequency resonant tuner which is arranged at the side of the high-frequency acceleration cavity to mechanically adjust the resonance frequency at the plurality of cavity cells from outside of the high-frequency acceleration cavity without inserting a frequency adjusting rod into the plurality of cavity cells.