Filament for X-ray tube and X-ray tube having the same

An X-ray tube comprising a coiled filament which includes:

• a central region including plural turns having a same coil pitch;
• and
• end regions which are arranged on either side of the central regions and include plural turns each of which has a coil pitch smaller than the coil pitch of the central region,
• wherein the coil pitches of the plural turns of the end regions are reduced one by one by a same variation from a turn close to the central region toward an outermost turn, and
• Δp/p is within a range of 0.015 to 0.1 and k/n is within a range of 0.3 to 0.8, where p is the coil pitch of the central region, Δp is the coil pitch variation of the end regions, n is a total number of turns of the filament, and k is a sum of numbers of turns of the end regions.

An X-ray tube comprising:

• an electron gun which includes a Wehnelt electrode formed with an elongate opening and a coiled filament disposed inside the opening to emit an electron beam;
• and
• a target which is irradiated with the electron beam to generate an X-ray beam,
• wherein the opening has two longer sides positioned asymmetrically about a center-of-width line of the filament, and
• the filament includes:
• a central region including plural turns having a same coil pitch;
• and
• end regions which are arranged on either side of the central regions and include plural turns each of which has a coil pitch smaller than the coil pitch of the central region,
• the coil pitches of the plural turns of the end regions being reduced one by one by a same variation from a turn close to the central region toward an outermost turn.