Mobile miniature X-ray source

• US 6,661,876 B2
• Filed: 07/29/2002
• Issued: 12/09/2003
• Est. Priority Date: 07/30/2001
• Status: Expired due to Fees

• Current Assignee: Moxtek (Polatechno Co.,Ltd.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Voronov, Sergei, Moody, Paul, Reyes, Arturo, Lund, Mark W., Pew, Hans K., Turner, Clark, Lines, Michael
• Primary Examiner(s): Dunn, Drew A.
• Application Number:
  US10/208,646
• Publication Number:
  US 20030021377A1
• Time in Patent Office: 498 Days
• Field of Search: 378/119, 378/122, 378/123, 378/138, 378/143, 378/101, 378/102, 378/64, 378/65, 313/553
• US Class Current: 378/138
• CPC Class Codes: G01N 2223/076 X-ray fluorescence
• CPC Class Codes: G01N 23/223 by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence
• CPC Class Codes: G01N 33/18 Water
• CPC Class Codes: H01J 2235/163 shaped for a particular application
• CPC Class Codes: H01J 35/04 Electrodes ; Mutual position thereof; Constructional adaptations therefor
• CPC Class Codes: H01J 35/116 Transmissive anodes acting as a window H01J35/186
• CPC Class Codes: H01J 35/186 used as targets or X-ray converters
• CPC Class Codes: H01J 35/32 Tubes wherein the X-rays are produced at or near the end of the tube or a part thereof which tube or part has a small cross-section to facilitate introduction into a small hole or cavity

Abstract

A mobile, miniature x-ray source includes a low-power consumption cathode element for mobility, and an anode optic creating a field free region to prolong the life of the cathode element. An electric field is applied to an anode and a cathode that are disposed on opposite sides of an evacuated tube. The anode includes a target material to produce x-rays in response to impact of electrons. The cathode includes a cathode element to produce electrons that are accelerated towards the anode in response to the electric field between the anode and the cathode. The tube can have a length less than approximately 3 inches, and a diameter or width less than approximately 1 inch. The cathode element can include a low-power consumption cathode element with a low power consumption less than approximately 1 watt. The power source can include a battery power source. A field-free region can be positioned at the anode to resist positive ion acceleration back towards the cathode element. An anode tube can be disposed at the anode between the anode and the cathode, and electrically coupled to the anode so that the anode and the anode tube have the same electrical potential, to form the field-free region.

Claims

1. A mobile, miniature x-ray source device, comprising:

a) an evacuated tube having a length less than approximately 3 inches, and a diameter or width less than approximately 1 inch;

b) an anode, disposed in the tube, including a material configured to produce x-rays in response to impact of electrons; and

c) a cathode, disposed in the tube opposing the anode, including a low-power consumption cathode element configured to produce electrons accelerated towards the anode in response to an electric field between the anode and the cathode, the cathode element having a low power consumption less than approximately 1 watt; and

d) a battery power source, electrically coupled to the anode, the cathode, and the cathode element, to provide power for the cathode element, and to provide the electric field between the anode and the cathode.

2. A device in accordance with claim 1, wherein the battery power source includes a battery operated, high voltage power supply and provides an electric field between the anode and the cathode of at least approximately 15 kilo-volts.

3. A device in accordance with claim 1, further comprising a window, disposed in the evacuated tube at the anode, including a target material configured to produce x-rays in response to impact of electrons.

4. A device in accordance with claim 1, further comprising:

a field-free region, positioned at the anode, configured to resist positive ion acceleration back towards the cathode element.

5. A device in accordance with claim 4, wherein the electrons impact the anode and heat the anode, releasing residual gas molecules, and wherein the electrons ionize the residual gas molecules to positive ions, which ions would normally be accelerated back to the cathode and sputter-erode the cathode element.

6. A device in accordance with claim 4, further comprising:

a) an anode tube, disposed at the anode between the anode and the cathode, and electrically coupled to the anode so that the anode and the grounded anode tube have the same electrical potential, the anode tube creating the field-free region.

7. A device in accordance with claim 1, wherein the anode tube and the anode include the same material.

8. A device in accordance with claim 1, further comprising:

a) a cathode optic, disposed proximate the cathode element, including a plate with an aperture therein configured to allow electrons to pass through the aperture towards the anode; and

b) an anode optic, disposed proximate the anode, including an anode tube with a hollow aligned to allow electrons to pass through the hollow towards the anode, the anode tube creating the field-free region within the hollow configured to resist positive ion acceleration back towards the cathode element.

9. A device in accordance with claim 1, wherein the cathode element includes a low-mass filament having a mass less than approximately 100 micrograms.

10. A device in accordance with claim 1, further comprising a window, disposed in an end of the evacuated tube, configured to release x-rays, the window being aligned with a longitudinal axis of the evacuated tube configured to release x-rays substantially along the longitudinal axis.

11. A device in accordance with claim 1, further comprising a window, disposed in a side of the evacuated tube, configured to release x-rays transverse to the longitudinal axis.

12. A device in accordance with claim 1, wherein the cathode element includes an electron emitting source selected from the group consisting of:

a thermionic emitter, a tungsten filament, a tungsten filament coated with mixed oxides of alkaline earths, a field emitter, a ferroelectric cathode, a metal tip array, a gated-modulated emitter in an array, a gate-modulated emitter in a field emitting surface, a carbon nanotube, a carbon nanotube with a modulating gate, and heated lanthanum hexaboride.

13. An x-ray source device, comprising:

a) an evacuated tube;

b) an anode, disposed in the tube, including a material configured to produce x-rays in response to impact of electrons; and

c) a cathode, disposed in the tube opposing the anode, including a cathode element configured to produce electrons accelerated towards the anode in response to an electric field between the anode and the cathode; and

d) a field-free region, positioned at the anode, configured to resist positive ion acceleration back towards the cathode element.

14. A device in accordance with claim 13, wherein the electrons impact the anode and heat the anode, releasing residual gas molecules, and wherein the electrons ionize the residual gas molecules to positive ions, which ions would normally be accelerated back to the cathode and sputter-erode the cathode element.

15. A device in accordance with claim 13, further comprising:

a) an anode tube, disposed at the anode between the anode and the cathode, and electrically coupled to the anode so that the anode and the anode tube have the same electrical potential, the anode tube creating the field-free region.

16. A device in accordance with claim 15, wherein the anode tube and the anode include the same material.

17. A device in accordance with claim 13, wherein the evacuated tube has a length less than approximately 3 inches, and a diameter or width less than approximately 1 inch;

wherein the cathode element has a low power consumption less than approximately 1 watt; and

further comprising;

a battery power source, electrically coupled to the anode, the cathode, and the cathode element, to provide power for the cathode element, and to provide the electric field between the anode and the cathode.

18. A device in accordance with claim 13, further comprising:

a) a cathode optic, disposed proximate the cathode element, including a plate with an aperture therein configured to allow electrons to pass through the aperture towards the anode; and

b) an anode optic, disposed proximate the anode, including an anode tube with a hollow aligned to allow electrons to pass through the hollow towards the anode, the anode tube creating the field-free region within the hollow.

19. A device in accordance with claim 13, wherein the cathode element includes a low-mass filament having a mass less than approximately 100 micrograms.

20. A device in accordance with claim 13, wherein the cathode element includes an electron emitting source selected from the group consisting of:

a thermionic emitter, a tungsten filament, a tungsten filament coated with mixed oxides of alkaline earths, a field emitter, a ferroelectric cathode, a metal tip array, a gated-modulated emitter in an array, a gate-modulated emitter in a field emitting surface, a carbon nanotube, a carbon nanotube with a modulating gate, and heated lanthanum hexaboride.

21. An x-ray source device, comprising:

a) an evacuated tube having first and second ends;

b) an anode, disposed at the first end of the tube;

c) a window, disposed at the first end of the tube, including a material configured to produce x-rays in response to impact of electrons;

d) a cathode, disposed at the second end of the tube opposing the anode;

e) an electron emitter, disposed at the second end of the tube, configured to produce electrons accelerated towards the anode in response to an electric field between the anode and the cathode;

f) a cathode optic, disposed proximate the electron emitter, including a plate with an aperture therein configured to allow electrons to pass through the aperture towards the anode; and

g) an anode optic, disposed proximate the anode, including an anode tube with a hollow aligned to allow electrons to pass through the hollow towards the anode, the anode tube creating a field-free region within the hollow configured to resist positive ion acceleration back towards the cathode element.

22. A device in accordance with claim 21, wherein the anode tube of the anode optic is directly attached to the target material.

23. A device in accordance with claim 21, wherein the anode tube and the anode are formed of the same material.

24. A device in accordance with claim 21, further comprising:

a) a shield surrounding at least a portion of the evacuated tube; and

b) an insulating material disposed between the evacuated tube and the shield.

25. A device in accordance with claim 21, further comprising:

a) an x-ray filter, disposed at the output window adjacent the target material; and

b) an x-ray collimator, disposed at the output window, including an aperture to configured to allow x-rays therethrough in a desired direction.

26. A device in accordance with claim 21, wherein the electrons impact the anode and heat the anode, releasing residual gas molecules, and wherein the electrons ionize the residual gas molecules to positive ions, which positive ions would normally be accelerated back to the electron emitter.

27. A device in accordance with claim 21, wherein the cathode element includes a low-mass filament having a mass less than approximately 100 micrograms.

28. A device in accordance with claim 21, wherein the electron emitter is selected from the group consisting of:

a thermionic emitter, a tungsten filament, a tungsten filament coated with mixed oxides of alkaline earths, a field emitter, a ferroelectric cathode, a metal tip array, a gated-modulated emitter in an array, a gate-modulated emitter in a field emitting surface, a carbon nanotube, a carbon nanotube with a modulating gate, and heated lanthanum hexaboride.