Electron gun using virtual source method

An electron gun using a virtual source method, the electron gun comprising:

• an emitter configured to emit an electron beam to the outside;
• a suppressor electrode disposed at a position behind a tip of the emitter based on a direction of emission of the electron beam and surrounding the emitter;
• and
• an extraction electrode disposed on one side of the suppressor electrode,
• wherein the emitter has a virtual source formed inside an interior region of the emitter,
• wherein the suppressor electrode is configured to suppress electron emission from regions other than the tip and to induce formation of the virtual source inside the emitter,
• wherein sizes of holes of the suppressor electrode and the extraction electrode are less than or equal to 5 mm in diameter,
• wherein a distance between the suppressor electrode and the extraction electrode is greater than or equal to 0.5 mm and less than or equal to 2 mm, and
• wherein the suppressor electrode comprises a first surface and a second surface inclined relative to the first surface to define a tapered tip of the suppressor electrode, the tapered tip of the suppressor electrode having a first thickness defined by a distance between the first surface and the second surface in the direction of emission and gradually decreasing toward a distal end of the suppressor electrode;
• and
• wherein the extraction electrode comprises a third surface opposing the first surface and a fourth surface inclined relative to the third surface to define a tapered tip of the extraction electrode, the tapered tip of the extraction electrode having a second thickness defined by a distance between the third surface and the fourth surface in the direction of emission and gradually decreasing toward a distal end of the extraction electrode.