Compact X-ray source

• US 8,995,621 B2
• Filed: 07/15/2011
• Issued: 03/31/2015
• Est. Priority Date: 09/24/2010
• Status: Active Grant

• Current Assignee: Moxtek (Polatechno Co.,Ltd.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Wang, Dongbing, Reynolds, Dave
• Primary Examiner(s): Ho, Allen C.
• Application Number:
  US13/812,102
• Publication Number:
  US 20140294156A1
• Time in Patent Office: 1,355 Days
• Field of Search: 378/101, 378/102, 378/104, 378/105, 378/106, 378/107, 307/43, 363 59- 61
• US Class Current: 378/107
• CPC Class Codes: H01F 27/28 Coils; Windings; Conductive connections
• CPC Class Codes: H01F 27/40 Structural association with built-in electric component, e.g. fuse
• CPC Class Codes: H01J 35/22 specially designed for passing a very high current for a very short time, e.g. for flash operation
• CPC Class Codes: H05G 1/12 with dc or rectified single-phase ac or double-phase
• CPC Class Codes: H05G 1/20 with high-frequency ac; with pulse trains pulse generators in general H03K3/00, H03K4/00
• CPC Class Codes: H05G 1/265 Measurements of current, voltage or power
• CPC Class Codes: H05G 1/32 Supply voltage of the X-ray apparatus or tube

Abstract

A compact x-ray source can include a circuit (10) providing reliable voltage isolation between low and high voltage sides (21, 23) of the circuit while allowing AC power transfer between the low and high voltage sides of the circuit to an x-ray tube electron emitter (43). Capacitors (11, 12) can provide the isolation between the low and high voltage sides of the circuit. The x-ray source (110) can utilize capacitors of a high voltage generator (67) to provide the voltage isolation. A compact x-ray source (110) can comprise a single transformer core (101) to transfer alternating current from two alternating current sources (104a, 104b) to an electron emitter (43) and a high voltage generator (107). A compact x-ray source (120) can comprise a high voltage sensing resistor (R1) disposed on a cylinder (41) of an x-ray tube (40).

Claims

1. A power source comprising:

a. a first alternating current source connected in series with a first capacitor;

b. the first alternating current source configured to be operated at a first frequency and a first amplitude;

c. a second alternating current source configured to be operated at a second frequency and a second amplitude;

d. the first alternating current source and the first capacitor connected in parallel with the second alternating current source;

e. the first frequency having a value that is at least 3 times greater than the second frequency;

f. the second amplitude having a value that is at least 3 times greater than the first amplitude;

g. a high voltage generator having two connection points at a low voltage end and two connection points at a high voltage end;

h. the first alternating current source and the first capacitor and the second alternating current source connected in parallel with the two connection points at the low voltage end of the high voltage generator; and

i. a load connected between the two connection points at the high voltage end of the high voltage generator.

2. The power source of claim 1, wherein the load comprises an x-ray tube filament and a second capacitor connected in series.

3. The power source of claim 1, wherein the first frequency has a value of greater than 100 megahertz and the second frequency has a value of between 10 kilohertz to 10 megahertz.

4. The power source of claim 1, wherein the first amplitude has a value of less than 10 volts and the second amplitude has a value of greater than 100 volts.

5. The power source of claim 1, wherein:

a. the high voltage generator is a Cockcroft-Walton multiplier with diodes that have a forward voltage of greater than 10 volts; and

b. the first amplitude has a value of less than 10 volts.

6. The power source of claim 1, wherein the high voltage generator develops a voltage differential between the low voltage end and the high voltage end of greater than 10 kilovolts.

7. The power source of claim 1, further comprising:

a. an x-ray tube comprising;

i. an insulative cylinder;

ii. an anode disposed at one end of the insulative cylinder and electrically connected to ground;

iii. a cathode at an opposing end of the insulative cylinder from the anode, the cathode comprising a filament;

b. the filament is the load;

c. the first alternating current source drives alternating current and power at the filament;

d. the second alternating current source supplies alternating current to the high voltage generator, allowing the high voltage generator to develop a voltage differential from the low voltage end to the high voltage end of greater than 10 kilovolts, thus creating a high voltage at the cathode and a voltage differential between the cathode and the anode; and

e. the voltage differential between the cathode and the anode and the alternating current at the filament cause electrons to be emitted from the filament and propelled towards the anode.

8. The power source of claim 1, wherein the second alternating current source comprises:

a. an alternating current source connected in series with input windings on a step-up transformer;

b. output windings on the step-up transformer connected in parallel with the first alternating current source and the first capacitor.

9. An x-ray source comprising:

a. a power source comprising;

i. a first alternating current source connected in series with a first capacitor;

ii. the first alternating current source configured to be operated at a first frequency and a first amplitude;

iii. a second alternating current source configured to be operated at a second frequency and a second amplitude;

iv. the first alternating current source and the first capacitor connected in parallel with the second alternating current source;

v. the first frequency having a value that is at least 3 times greater than the second frequency;

vi. the second amplitude having a value that is at least 3 times greater than the first amplitude;

vii. a high voltage generator having two connection points at a low voltage end and two connection points at a high voltage end;

viii. the first alternating current source and the first capacitor and the second alternating current source connected at the two connection points at the low voltage end of the high voltage generator and in parallel with the high voltage generator; and

ix. a load connected between the two connection points of the high voltage end of the high voltage generator and in parallel with the high voltage generator;

b. an x-ray tube comprising;

i. an insulative cylinder;

ii. an anode disposed at one end of the insulative cylinder and electrically connected to ground; and

iii. a cathode at an opposing end of the insulative cylinder from the anode, the cathode comprising a filament;

c. the load comprises the filament and a second capacitor connected in series;

d. the first alternating current source drives alternating current and power at the filament;

e. the second alternating current source supplies alternating current to the high voltage generator, allowing the high voltage generator to develop a voltage differential from the low voltage end to the high voltage end, thus creating a voltage differential between the cathode and the anode; and

f. the voltage differential between the cathode and the anode and the alternating current at the filament cause electrons to be emitted from the filament and propelled towards the anode.

10. The x-ray source of claim 9, wherein:

a. the first frequency has a value of greater than 100 megahertz and the second frequency has a value of between 10 kilohertz to 10 megahertz;

b. the first amplitude has a value of less than 10 volts and the second amplitude has a value of greater than 100 volts;

c. the high voltage generator is a Cockcroft-Walton multiplier with diodes that have a forward voltage of greater than 10 volts.

11. A multiple channel transformer comprising:

a. a transformer core;

b. a first input circuit wrapped at least one time around the transformer core and configured to carry an alternating current signal at a first frequency;

c. a first output circuit comprising a first output winding;

d. the first output winding wrapped at least one time around the transformer core;

e. the first output circuit having a resonant frequency which is about the same as the first frequency;

f. a second input circuit wrapped at least one time around the transformer core and configured to carry an alternating current signal at a second frequency;

g. a second output circuit comprising a second output winding;

h. the second output winding wrapped at least one time around the transformer core; and

i. the second output circuit having a resonant frequency which is about the same as the second frequency.

12. The multiple channel transformer of claim 11, further comprising:

a. a first output circuit capacitor, having a first output capacitance, in parallel with the first output winding, the first output winding having a first output inductance, and the first frequency equals the inverse of the product of two times π

times the square root of the first output inductance times the first output capacitance; and

b. a second output circuit capacitor, having a second output capacitance, in parallel with the second output winding, the second output winding having a second output inductance, and the second frequency equals the inverse of the product of two times π

times the square root of the second output inductance times the second output capacitance.

13. The multiple channel transformer of claim 11, wherein the first frequency is at least ten times greater than the second frequency.

14. The multiple channel transformer of claim 11, wherein the second frequency is at least ten times greater than the first frequency.

15. The multiple channel transformer of claim 11, wherein the first frequency is between 10 times greater to 1000 times greater than the second frequency.

16. The multiple channel transformer of claim 11, wherein:

a. the first input circuit induces a current in the first output circuit at the first frequency with negligible inducement of current in the first output circuit from the second input circuit; and

b. the second input circuit induces a current in the second output circuit at the second frequency with negligible inducement of current in the second output circuit from the first input circuit.

17. The multiple channel transformer of claim 11, wherein:

a. the first output circuit further comprises a first output circuit capacitor, having a first output capacitance, in parallel with the first output winding;

b. the first output winding having a first output inductance;

c. the second output circuit further comprises a second output circuit capacitor, having a second output capacitance, in parallel with the second output winding;

d. the second output winding having a second output inductance; and

e. an inverse square root of the product of the first output capacitance and the first output inductance does not equal an inverse square root of the product of the second output capacitance and the second output inductance.

18. The multiple channel transformer of claim 11, wherein the inverse square root of the product of the first output capacitance and the first output inductance is greater than ten times the inverse square root of the product of the second output capacitance and the second output inductance.

19. The multiple channel transformer of claim 11, wherein:

a. the resonant frequency of the first output circuit is between 1 megahertz to 500 megahertz; and

b. the resonant frequency of the second output circuit is between 10 kilohertz to 1 megahertz.

20. The multiple channel transformer of claim 11, further comprising:

a. an x-ray tube comprising;

i. an insulative cylinder;

ii. an anode disposed at one end of the insulative cylinder and electrically connected to ground;

iii. a cathode disposed at an opposing end of the insulative cylinder from the anode, the cathode comprising a filament;

b. a high voltage generator for generating a high voltage having an absolute value of at least 10 kilovolts electrically connected to the cathode, the high voltage generator providing a voltage differential of at least 10 kilovolts between the anode and the cathode;

c. the first output circuit electrically connected to and providing an alternating current to the filament;

d. the second output circuit electrically connected to and providing an alternating current to the high voltage generator.