X-ray tube for improving electron focusing

1. An X-ray tube for improving electron focusing, the X-ray tube comprising:

a thermionic emitter configured to emit thermoelectrons by application of a negative high voltage;

a focusing tube configured to focus the thermo electrons emitted from the thermionic emitter;

an X-ray irradiation window configured to irradiate X-rays outside by the thermoelectrons bombarded on a target distributed on the X-ray irradiation window, to generate the X-rays after the thermoelectrons pass through the focusing tube;

a tube part including both the thermionic emitter and the focusing tube; and

a housing surrounding the tube part,

wherein the thermionic emitter includes a filament, and a plurality of stem pins applying the negative high voltage to the filament,

the focusing tube includes a first focusing tube surrounding the filament and firstly focusing thermoelectrons emitted from the filament, and a second focusing tube secondly focusing thermoelectrons emitted from the first focusing tube by being disposed to face the first focusing tube, and

wherein the focusing tube and the housing are configured to have a same potential such that movement directions of the thermoelectrons are directed from the first focusing tube to the second focusing tube towards the X-ray irradiation window, and the housing has a predetermined length such that the first focusing tube is placed inside the housing and the second focusing tube is placed outside the housing.

2. The X-ray tube of claim 1 , further comprising:

a substrate provided with first, second, and third terminals, and disposed at an end of the housing; and

a connection part electrically connected to any one of the terminals of the substrate,

wherein the first and second terminals are electrically connected to the plurality of stem pins, respectively, and the third terminal is electrically connected to the connection part, and

first and second stem pins of the plurality of stem pins and the connection part have a same potential.

3. The X-ray tube of claim 2 , wherein the first stem pin and the connection part are supplied with the negative high voltage to cause the thermoelectrons to be bombarded on the target, and

the second stem pin is supplied with the negative high voltage to allow the filament to emit the thermoelectrons.

4. The X-ray tube of claim 3 , wherein the connection part, the first focusing tube, and the housing are electrically connected to each other, so that the same potential is generated with the negative high voltage.

5. The X-ray tube of claim 3 , further comprising:

a getter disposed below the filament to maintain a vacuum inside the tube part, with the plurality of stem pins penetrating therethrough; and

a stem part disposed below the getter, with the plurality of stem pins penetrating therethrough.

6. The X-ray tube of claim 5 , wherein the tube part and the stem part are made of a ceramic material.

7. The X-ray tube of claim 5 , wherein the connection part is coupled to support the stem part.

8. The X-ray tube of claim 2 , wherein the housing, the first focusing tube, and the connection part are made of a conductive material.

9. The X-ray tube of claim 8 , wherein the housing is made of a brass material, and

both the first focusing tube and the connection part are made of a Kovar material.

10. The X-ray tube of claim 1 , wherein the first focusing tube and the second focusing tube extend longitudinally so as to face each other while being spaced apart from each other at a predetermined interval in the tube part, and

each of the first focusing tube and the second focusing tube is provided with an opening at an end tip thereof to emit or receive thermoelectrons.