Field emission device and reforming treatment method

A field emission device, comprising:

• a vacuum vessel with a cylindrical insulator, the insulator having both ends sealed to define a vacuum chamber on an inner wall side of the insulator;
• an emitter located on one end side of the vacuum chamber and having an electron generating portion facing the other end side of the vacuum chamber;
• a target located on the other end side of the vacuum chamber and opposed to the electron generating portion of the emitter;
• a supporting body that has a shape extending from a side of the emitter opposite the electron generating portion and supports the emitter;
• a guard electrode disposed on an outer circumferential side of the electron generating portion of the emitter, the guard electrode having a cylindrical shape extending in an end-to-end direction of the vacuum chamber and being supported at one end side thereof on the vacuum vessel;
• and
• a bellows supported at one end side thereof on the supporting part and supported at the other end side thereof on the vacuum vessel so as to constitute a part of the vacuum vessel.

A field emission device, comprising:

• a vacuum vessel with a cylindrical insulator, the insulator having both ends sealed to define a vacuum chamber on an inner wall side of the insulator;
• an emitter located on one end side of the vacuum chamber and having an electron generating portion facing the other end side of the vacuum chamber;
• a target located on the other end side of the vacuum chamber and opposed to the electron generating portion of the emitter;
• a guard electrode disposed on an outer circumferential side of the electron generating portion of the emitter, the guard electrode having a cylindrical shape extending in an end-to-end direction of the vacuum chamber and being supported at one end side thereof on the vacuum vessel;
• and
• a supporting part,
• wherein the supporting part includes:
• a supporting body that has a shape extending from a side of the emitter opposite the electron generating portion and supports the emitter;
• a magnetic body disposed on an extending direction side of the supporting body;
• a circumferential wall that has a shape extending outwardly from a portion of the vacuum vessel opposed to the extending direction side of the supporting body and surrounds the supporting body and the magnetic body;
• and
• a magnet disposed on an outer wall surface of the circumferential wall;
• and
• wherein the relationship of t1≦t≦t2 is satisfied where t1 is a distance from a movement range of the magnetic body to the outer wall surface of the circumferential wall at a position opposed to the movement range of the magnetic body in a direction between the magnet and the movement range of the magnetic body;
• t2 is a maximum distance at which a magnetic attractive force can be generated between the magnet and the magnetic body by the action of a magnetic force of the magnet on the magnetic body;
• and t is a minimum distance between the magnet and the magnetic body.