Devices and methods for producing multiple x-ray beams from multiple locations

1. An x-ray generating device for scanning an object under inspection, the x-ray generating device comprising:

(a) at least one addressable field emission cathode, the cathode comprising a substrate and a nanostructure-containing material comprising a plurality of individually controllable nanostructure-containing elements configured to emit electrons;

(b) at least one anode target comprising a plurality of focal spots corresponding to the plurality of nanostructure-containing elements, wherein the device is configured for simultaneously generating multiple x-ray beams from the focal spots at different radiation angles for simultaneous convergence at an image plane for imaging of an object; and

(c) wherein the at least one addressable field-emission cathode and the at least one anode target are contained within a vacuum chamber.

2. The device of claim 1 , wherein the nanostructure-containing material comprises single-walled carbon nanotubes, multi wall nanotubes, or mixtures thereof.

3. The device of claim 1 , comprising a nanostructure-containing material coating layer that at least partially covers the cathode.

4. The device of claim 3 , further comprising an adhesion-promoting interlayer between the substrate and the nanostructure-containing material coating layer.

5. The device of claim 1 , further comprising a gate electrode arranged to control the field-emission cathode, wherein the gate electrode is rotatable.

6. The device of claim 1 , wherein the device is portable.

7. The device of claim 1 , further comprising a moveable stage.

8. The device of claim 1 , wherein the at least one addressable field-emission cathode emits electrons without the assistance of the heater.

9. A multi-beam x-ray generating device comprising:

(a) a stationary field-emission cathode comprising a plurality of stationary and individually controllable electron-emitting pixels disposed in a predetermined pattern on the cathode;

(b) an anode opposing the cathode comprising a plurality of focal spots disposed in a predetermined pattern that corresponds to the predetermined pattern of the pixels, wherein the device is configured for simultaneously generating multiple x-ray beams from the focal spots at different radiation angles for simultaneous convergence at an image plane for imaging of an object; and

(c) a vacuum chamber enveloping the anode and cathode.

10. The device of claim 9 , wherein the cathode comprises a nanostructure-containing material.

11. The device of claim 10 , wherein the nanostructure-containing material comprises single walled carbon nanotubes.

12. The device of claim 9 , wherein the cathode has a planar geometry.

13. The device of claim 12 , wherein the anode has a planar geometry.

14. The device of claim 9 , further comprising at least one gate electrode arranged to control the field-emission cathode wherein the at least one gate electrode comprises a plurality of individually addressable gate electrode control units, each unit arranged to control a corresponding electron-emitting pixel.

15. The device of claim 9 , wherein the focal spots comprise materials that produce x-rays with different energy distributions when bombarded with electrons emitted from the pixels.

16. The device of claim 9 , comprising one focal spot for every pixel.

17. The device of claim 9 , further comprising a computer programmed to control the plurality of pixels.

18. The device of claim 17 , wherein the computer is programmed to turn on the pixels in sequence, at a predetermined frequency, for a predetermined duty cycle, and/or for a predetermined dwell time.

19. The device of claim 9 , wherein the pixels and corresponding focal spots are arranged along the circumference of a circle.

20. The device of claim 9 , wherein the plurality of pixels are arranged in a circular shape.

21. The device of claim 9 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is rotatable.

22. The device of claim 9 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is stationary.

23. The device of claim 9 , wherein the pixels and corresponding focal spots are arranged along the circumferences of a plurality of concentric circles.

24. The device of claim 9 , wherein the pixels are arranged in at least one cluster, the at least one cluster comprising a plurality of immediately adjacent pixels.

25. The device of claim 24 , wherein each pixel comprises a multi-layer electrical gate or coil constructed to focus a beam of electrons emitted from each pixel.

26. The device of claim 24 , further comprising a collimator constructed to focus the x-ray beams generated by the focal spots.

27. The device of claim 24 , further comprising an x-ray detector.

28. The device of claim 27 , wherein the detector comprises a plurality of discrete detector elements.

29. An x-ray generating device comprising:

(a) a stationary field-emission cathode, the cathode comprising a planar surface with an electron-emissive material disposed on at least a portion thereof;

(b) a gate electrode disposed in parallel spaced relationship relative to the planar surface of the cathode, the gate electrode comprising a plurality of openings having different sizes;

(c) an anode opposing the cathode and spaced therefrom, the anode comprising a plurality of focal spots aligned with the electron-emissive material; and

(d) a vacuum chamber enveloping the anode and cathode;

(e) wherein the gate electrode is operable such that the openings are manipulated to bring at least one beam of electrons emitted from the cathode into and out of registry with at least one of the focal spots,

(f) wherein the openings comprise a plurality of mesh grids, and

(g) wherein each of the mesh grids are electrically and independently controlled.

30. The device of claim 29 , wherein the gate electrode is rotatable.

31. The device of claim 29 , wherein the mesh grids are formed from tungsten, molybdenum, nickel, or alloys thereof.

32. The device of claim 30 , further comprising a computer programmed to control the speed at which the gate electrode is rotated, a voltage applied to the gate electrode, a sequence of focal spots brought into registry with electrons emitted from the cathode, and/or the amount of time that the emitted electrons are allowed to remain in registry with a particular focal spot.

33. The device of claim 29 , wherein the cathode comprises a nanostructure-containing material.

34. The device of claim 29 , wherein the nanostructure-containing material comprises single walled carbon nanotubes.

35. A method of scanning an object with x-rays directed at the object from different locations, the method comprising:

(a) providing a stationary field-emission cathode comprising a plurality of stationary and individually controllable electron-emitting pixels and disposing the pixels in a predetermined pattern on the cathode;

(b) locating an anode in opposing relationship to the cathode and providing the anode with a plurality of focal spots disposed in a predetermined pattern that corresponds to the predetermined pattern of the pixels, wherein multiple x-ray beams are generated simultaneously from the focal spots at different radiation angles for simultaneous convergence at an image plane for imaging of an object, wherein the plurality of focal spots are arranged in a circular shape;

(c) enveloping the anode and cathode with a vacuum chamber; and

(d) activating at least one of the pixels thereby generating a beam of emitted electrons that is incident upon a corresponding focal spot of the anode, thereby generating an x-ray, and directing the x-ray toward the object to be scanned.

36. The method of claim 35 , wherein the step (d) comprises activating a first pixel thereby generating a first x-ray incident upon the object to be scanned from a first location, then sequentially activating at least a second pixel thereby generating a second x-ray incident upon the object to be scanned from a second location.

37. The method of claim 35 , wherein the step (d) comprises simultaneously activating a plurality of pixels thereby generating a plurality of x-rays incident upon the object to be scanned from multiple locations.

38. The method of claim 35 , further comprising the step of: (e) locating an x-ray detector such that x-rays passing through the object being scanned are incident up the detector.

39. The method of claim 38 , wherein the detector comprises a plurality of discrete detectors.

40. The method of claim 38 , wherein the detector comprises an array of detector pixels.

41. The method of claim 38 , further comprising the step of: (f) collecting input from the detector and constructing an image from the input.

42. The method of claim 41 , further comprising the step of: (g) displaying the constructed image.

43. The method of claim 35 , wherein the cathode comprises a nanostructure-containing material.

44. The method of claim 43 , wherein the nanostructure-containing material comprises single walled carbon nanotubes.

45. The method of claim 35 , wherein steps (a) and (b) comprise arranging the pixels and corresponding focal spots along the circumference of a circle.

46. The method of claim 35 , wherein steps (a) and (b) comprise arranging the pixels along the circumferences of a plurality of concentric circles.

47. The method of claim 35 , wherein the step (a) comprises arranging the pixels in at least one cluster, the at least one cluster comprising a plurality of immediately adjacent pixels.

48. The device of claim 9 wherein the pixels comprise a material selected from the group consisting of: nanotubes, nonowires, and nonorods.

49. The device of claims 1 or 9 wherein the cathode has an emitted current density of between about 4 A/cm 2 and about 10 A/cm 2 .

50. The device of claim 9 wherein an applied electrical field of between 2 and about 7 V/μm between the cathode and the anode produces a stable current density of about 100 mA/cm 2 .

51. A method of scanning an object with x-rays directed at the object from different locations, the method comprising:

(a) providing a stationary field-emission cathode comprising a plurality of stationary and individually controllable electron-emitting pixels and disposing the pixels in a predetermined pattern on the cathode;

(b) locating an anode in opposing relationship to the cathode and providing the anode with a plurality of focal spots disposed in a predetermined pattern that corresponds to a circular shape;

(c) enveloping the anode and cathode with a vacuum chamber; and

(d) activating at least one of the pixels thereby generating a beam of emitted electrons that is incident upon a corresponding focal spot of the anode, thereby generating an x-ray, and directing the x-ray toward the object to be scanned, wherein multiple x-ray beams are generated simultaneously from the focal spots at different radiation angles for simultaneous convergence at an image plane for imaging of an object.

52. The device of claim 1 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is rotatable.

53. The device of claim 9 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is stationary.

54. The device of claim 9 further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is stationary.

55. The device of claim 19 wherein the plurality of pixels are arranged in a circular shape.

56. The device of claim 19 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is rotatable.

57. The device of claim 19 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is stationary.

58. The device of claim 29 wherein the plurality of pixels are arranged in a circular shape.

59. The device of claim 29 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is rotatable.

60. The device of claim 29 , further comprising at least one gate electrode arranged to control the field-emission cathode, wherein the gate electrode is stationary.