Field emission device and field emission method

A field emission device comprising:

• a vacuum container including an insulator shaped tubular and a vacuum chamber formed inside the insulator, wherein the insulator includes first and second ends both sealed;
• a bellows member expandable in a both-end direction that is a direction of the first and second ends;
• a movable body disposed in a first end side in the both-end direction in the vacuum chamber, and supported by the bellows member so as to be movable in the both-end direction;
• a guard electrode disposed around the movable body;
• and
• a target disposed in a second end side in the both-end direction in the vacuum chamber so as to face a second face of the movable body that is a face directed toward the second end side in the both-end direction,
• wherein:
• the movable body includes an emitter formed in a tip of the second face of the movable body;
• the emitter is formed by applying film formation processing to a surface of the tip, and includes an electron generator;
• the movable body includes an outer periphery including an outer peripheral stepped part that has a diameter decreasing from the first end side toward the second end side in the both-end direction so as to form a step;
• the guard electrode includes an inner periphery including an inner peripheral stepped part that has a diameter decreasing from the first end side toward the second end side in the both-end direction so as to form a step;
• and
• the outer peripheral stepped part and the inner peripheral stepped part overlap with each other when viewed in the both-end direction, and are structured to come into surface-to-surface contact with each other in response to satisfaction of a condition that the electron generator of the emitter and the guard electrode are close to or in contact with each other.