Magnetic head for X-ray source

• US 20070025516A1
• Filed: 03/30/2006
• Published: 02/01/2007
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Moxtek (Polatechno Co.,Ltd.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Jensen, Charles, Reyes, Arturo, Liddiard, Steven, Ogden, Shaun, Bard, Erik
• Granted Patent: US 7,428,298 B2
• Time in Patent Office: Days
• US Class Current: 378/138
• CPC Class Codes: H01J 2235/165 Shielding arrangements
• CPC Class Codes: H01J 35/116 Transmissive anodes acting as a window H01J35/186
• CPC Class Codes: H01J 35/147 Spot size control
• CPC Class Codes: H01J 35/153 Spot position control
• CPC Class Codes: H01J 35/16 Vessels; Containers; Shields associated therewith
• CPC Class Codes: H05G 1/04 Mounting the X-ray tube within a closed housing

Abstract

An X-ray source includes a magnetic appliance to provide electron beam focusing. The magnetic appliance can provide variably focused and non-focused configurations. The magnetic appliance can include one or more electromagnets and/or permanent magnets. An electric potential difference is applied to an anode and a cathode that are disposed on opposite sides of an evacuated tube. 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 anode includes a target material to produce x-rays in response to impact of electrons.

Claims

1. An X-ray source device with a magnetic appliance coupled to its anode for electron beam focusing, comprising:

a) an evacuated tube;

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

c) a cathode, coupled to 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) an annular magnetic appliance, circumscribing the anode, to focus an electron-beam.

2. A device in accordance with claim 1, wherein:

the evacuated tube has a length less than approximately 3 inches, and a diameter or width less than approximately 1 inch;

the cathode includes a low-power consumption cathode element having 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.

3. A device in accordance with claim 2, wherein the battery power source includes a battery operated, high voltage power supply and provides an electric field between the anode and the cathode between approximately 4 to 80 kilo-volts.

4. A device in accordance with claim 1, wherein the annular magnetic appliance provides focusing of an electron beam within the X-ray source device, the resulting focused electron beam having a cross-sectional diameter reduced at least 1/10^th in size relative to an unfocused electron beam produced without the annular magnetic appliance.

5. A device in accordance with claim 1, wherein the annular magnetic appliance provides focusing of an electron beam within the X-ray source device, the resulting focused electron beam having a cross-sectional diameter reduced between approximately ½

to 1/50^th in size relative to an unfocused electron beam produced without the annular magnetic appliance.

6. A device in accordance with claim 1, wherein the annular magnetic appliance further comprises:

an annular magnet, circumscribing the anode and having magnetic poles oriented parallel with a longitudinal axis of the annular magnet and the evacuated tube;

an annular pole piece, disposed proximate and axially forward of the annular magnet and having a longitudinal axis coaxial with the longitudinal axis of the evacuated tube; and

an annular shunt, disposed proximate and axially rearward of the annular magnet and having a longitudinal axis coaxial with the longitudinal axis of the evacuated tube.

7. A device in accordance with claim 6, wherein the anode, the annular magnet, the shunt, and the pole piece form a magnetic electron beam focusing lens.

8. A device in accordance with claim 1, wherein the anode further comprises:

a tube extension, attached to the evacuated tube, formed of a ferromagnetic material;

a window mount, attached to the tube extension, having a target; and

a drift tube, extending through and defined by the tube extension and the window mount, terminating at the target.

9. A device in accordance with claim 8, wherein the window mount has a magnetic permeability of approximately 1, and the annular magnet appliance includes an annular magnet with a magnetic energy product (BHmax) of approximately 30-40 Megagauss Oersteds.

10. A device in accordance with claim 8, wherein the window mount has a magnetic permeability of approximately 1, and the annular magnet appliance includes an annular magnet with a magnetic energy product (BHmax) of approximately 10-50 Megagauss Oersteds.

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

an annular magnet, circumscribing the anode and having magnetic poles oriented parallel with a longitudinal axis of the annular magnet and the evacuated tube;

an annular shunt, disposed proximate and rearward of the annular magnet, and contacting the tube extension, the shunt being formed of a ferromagnetic material; and

an annular pole piece, disposed proximate and forward of the annular magnet, and contacting the window mount, the pole piece being formed of a ferromagnetic material.

12. A device in accordance with claim 11, wherein the shunt and the pole piece have a magnetic permeability of approximately 10.

13. A device in accordance with claim 11, wherein the shunt and the pole piece have a magnetic permeability of greater than 1.

14. A device in accordance with claim 11, wherein the pole piece includes an exit aperture for the transmission of X-rays.

15. A device in accordance with claim 14, wherein the pole piece aperture is conical, having a smaller rearward opening nearest a site of X-ray production at the anode and a larger forward opening further from the site of X-ray production.

16. A device in accordance with claim 11, wherein the pole piece includes a central protrusion extending rearward to the window mount or anode.

17. A device in accordance with claim 11, wherein the anode, the annular magnet, the shunt and the pole piece are electrically grounded.

18. A device in accordance with claim 11, wherein the shunt is split into two pieces and has a central aperture with a diameter less than a diameter of the evacuated tube.

19. A device in accordance with claim 11, wherein the evacuated tube, the anode, the annular magnet, the shunt and the pole piece are disposable in a shield enclosure.

20. A device in accordance with claim 11, wherein at least the annular magnet is removably disposed on the anode.

21. A device in accordance with claim 1, wherein at least a portion of the annular magnet appliance is moveable.

22. A device in accordance with claim 1, wherein the magnetic appliance includes an electromagnet.

23. 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.

24. An X-ray source device with a magnetic head for electron beam focusing, comprising:

a) an evacuated tube formed of a ceramic material;

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

i) a tube extension, brazed to the evacuated tube, formed of a ferromagnetic material;

ii) a window mount, attached to the tube extension, including a target with a material configured to produce X-rays in response to impact of electrons; and

iii) a drift tube, extending through and defined by the tube extension and the window mount;

c) a cathode, disposed at another end of 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;

d) an annular magnet, circumscribing the anode;

e) an annular exit pole piece, proximate to and forward of the annular magnet, extending to the window mount; and

f) an annular shunt, proximate to and rearward of the annular magnet, defining a second pole piece, extending to the tube extension.

26. A magnetic head device for focusing an electron beam of an X-ray, comprising:

an annular magnet, configured to circumscribe an anode;

an annular pole piece, proximate to and forward of the annular magnet;

an annular shunt, proximate to and rearward of the annular magnet, defining a second pole piece.

25. A device in accordance with claim 26, wherein:

the evacuated tube has a length less than approximately 3 inches, and a diameter or width less than approximately 1 inch;

the cathode includes a low-power consumption cathode element having 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.