X-ray source

• US 5,682,412 A
• Filed: 09/20/1996
• Issued: 10/28/1997
• Est. Priority Date: 04/05/1993
• Status: Expired due to Term

• Current Assignee: Airdrie Partners I LP
• Original Assignee: Cardiac Mariners, Inc. (NovaRay Medical, Inc.)
• Inventors: Fellingham, George H., Skillicorn, Brian, Loeffler, Peter E.
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US08/717,611
• Time in Patent Office: 403 Days
• Field of Search: 378/137, 378/113, 378/98.6
• US Class Current: 378/98.6
• CPC Class Codes: A61B 6/06 Diaphragms
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies
• CPC Class Codes: A61B 6/4028 resulting in acquisition of views from substantially different positions, e.g. EBCT
• CPC Class Codes: A61B 6/4488 Means for cooling A61B6/045 takes precedence
• CPC Class Codes: G01T 1/202 the detector being a crystal
• CPC Class Codes: G01T 1/2971 using solid state detectors
• CPC Class Codes: H01J 35/147 Spot size control
• CPC Class Codes: H01J 35/153 Spot position control
• CPC Class Codes: H01J 35/30 by deflection of the cathode ray
• CPC Class Codes: H05G 1/10 Power supply arrangements for feeding the X-ray tube supply circuits with converters in general H02M; supply circuits for emitters and amplifiers H04B1/16 - H04B1/1623
• CPC Class Codes: H05G 1/64 Circuit arrangements for X-ray apparatus incorporating image intensifiers

Abstract

The x-ray source of the present invention comprises a charged particle beam generator and a vacuum enclosure assembly. The charged particle beam generator includes only a single electrical connection for providing high voltage to the electron gun. The power for the active circuits in the high voltage terminal of the charged particle beam generator is provided by a unique isolation transformer that has minimal losses and generates controlled magnetic flux. The generated charged particle beam is controlled through a series of dynamic and static focus coils and moved across the inner face of the target by a stepping coil assembly comprising x and y deflection coils as well as an x step and preferably a y step coil. Further, to minimize power usage, a control grid pinches off the charged particle beam during the stepping of the beam.

Claims

1. An x-ray source comprising a charged particle beam generator and a vacuum envelope assembly;

said charged particle beam generator comprising an outer casing, a high-voltage terminal and an electron gun;

said high-voltage terminal comprising electronic components to power said electron gun;

said vacuum envelope assembly comprising an outer casing, charged particle beam focussing means for focussing an electron beam generated by said charged particle beam generator, a target, and charged particle beam deflection means for deflecting said electron beam in a step pattern at said target;

said target operated at ground potential;

said charged particle beam deflection means comprising a beam controller, a fast deflection yoke and a slow deflection yoke, said beam controller having current outputs comprising an x-deflection current and an x-step current;

said x-deflection current having a triangular waveform with a non-zero substantially constant slope during the period of time it takes said electron beam to travel across the face of said target;

said x-step current comprising a waveform having a plurality of substantially sawtoothed shapes during the period of time it takes said electron beam to travel across the face of said target;

said slow deflection yoke comprising x-deflection coils and y-deflection coils, said x-deflection coils operably coupled to said beam controller and having an input electrically coupled to said x-deflection current;

said fast deflection yoke comprising x-step deflection coils operably coupled to said beam controller, said x-step deflection coils having lower inductance than said x-deflection coils and said y-deflection coils, said x-step deflection coils having an input electrically coupled to said x-step current.

2. The x-ray source of claim 1 wherein

said current output further comprises a y-step current, said y-step current comprising a periodic substantially sawtooth waveform with a period less than the time it takes said electron beam to travel across the face of said target;

said fast deflection yoke further comprises y-step deflection coils operably coupled to said beam controller, said y-step deflection coils having lower inductance than said x-deflection coils and said y-deflection coils, said y-step deflection coils having an input coupled to said y-step current.

3. The x-ray source of claim 1 wherein said charged particle beam focussing means comprises a static focus coil and a dynamic focus coil, said dynamic focus coil having lower inductance than said static focus coil;

a current in said dynamic focus coil synchronized with currents in said charged particle beam deflection means.

4. The x-ray source of claim 1 wherein said fast deflection yoke further comprises a rotational alignment assembly.

5. The x-ray source of claim 1 wherein said slow deflection yoke further comprises a rotational alignment assembly.

6. The x-ray source of claim 1 wherein said charged particle beam focussing means comprises an axial alignment assembly.

7. The x-ray source of claim 1 wherein said charged particle beam focussing means comprises a radial alignment assembly.

8. The x-ray source of claim 1 wherein a coolant flows in direct contact with said target.

9. The x-ray source of claim 1 wherein said outer casing comprises a first and a second wall, with a coolant flowing between said first and said second walls.

10. The x-ray source of claim 1 wherein said target comprises a target layer and a support layer;

said target layer comprising a layer of tantalum and a layer of niobium, said support layer comprising beryllium, said niobium forming an intermediate layer between said tantalum and said support layer.

11. The x-ray source of claim 1 wherein said target comprises a target layer and a support layer;

said target layer comprising a layer of tungsten-rhenium alloy.

12. The x-ray source of claim 1 wherein said target comprises a target layer and a support layer;

said target layer comprising a layer of tungsten-rhenium alloy and an intermediate niobium layer.

13. The x-ray source of claim 1 further comprising fiber optic links to control said electronic components.

14. An x-ray source comprising a charged particle beam generator and a vacuum envelope assembly;

said charged particle beam generator comprising an outer casing, a high-voltage terminal and an electron gun;

said high-voltage terminal comprising electronic components to power said electron gun;

said vacuum envelope assembly comprising an outer casing, a target, charged particle beam focussing means for focussing an electron beam generated by said charged particle beam generator, charged particle beam deflection means for deflecting said electron beam in a step pattern at said target, and a collimator, said target operated at ground potential;

said collimator comprising a plurality of rows and columns of x-ray transmissive apertures;

said charged particle beam deflection means comprising a beam controller, a fast deflection yoke and a slow deflection yoke, said beam controller having as its output control signals comprising an x-deflection signal and an x-step signal, said x-deflection signal comprising a waveform having a non-zero substantially constant slope when said electron beam is positioned along said target adjacent to a single row of said plurality of rows of apertures on said collimator, said x-step signal having a waveform with a plurality of periodic sawtooth shapes when said electron beam is positioned along said target adjacent to a single row of said plurality of rows of apertures on said collimator;

said slow deflection yoke comprising x-deflection coils and y-deflection coils, said x-deflection coils coupled to said x-deflection signal;

said fast deflection yoke comprising x-step deflection coils, said x-step deflection coils coupled to said x-step signal and having lower inductance than said x-deflection coils and said y-deflection coils.

15. The x-ray source of claim 14 wherein said fast deflection yoke further comprises a y-step deflection coils, said output of said beam controller further comprises a y-step current coupled to said y-step deflection coils, said y-step current comprising a periodic substantially sawtoothed waveform having a period substantially the same as the time it takes to deflect said electron beam from a position substantially behind a first row of x-ray transmissive apertures on said target to another position behind a second row of x-ray transmissive apertures on said target.

16. The x-ray source of claim 14 wherein said output of said beam controller further comprise a y-deflection signal coupled to said y-deflection coils, said y-deflection signal comprising a waveform having a slope of substantially zero when said electron beam is deflected across said target in substantial alignment with a single row of said plurality of rows of x-ray transmissive apertures of said collimator and said y-deflection signal comprising a waveform having a substantially constant non-zero slope when said electron beam is deflected from a position substantially behind one of said x-ray transmissive apertures of a first row of x-ray transmissive apertures at one end of said target to one of said x-ray transmissive apertures of a second row of x-ray transmissive apertures at another end of said target.

17. The x-ray source of claim 14 wherein a coolant flows in direct contact with said target.

18. The x-ray source of claim 14 wherein said charged particle beam deflection means comprises a rotational alignment assembly.

19. The x-ray source of claim 14 wherein said charged particle beam deflection means comprises a rotational alignment assembly.

20. The x-ray source of claim 14 wherein

said output of said beam controller further comprises a y-step signal having a substantially sawtoothed waveform;

said fast deflection yoke further comprises y-step deflection coils, said y-step deflection coils coupled to said y-step signal.