X-ray tube high voltage sensing resistor

• US 8,948,345 B2
• Filed: 01/17/2013
• Issued: 02/03/2015
• Est. Priority Date: 09/24/2010
• Status: Expired due to Fees

• Current Assignee: Moxtek Inc (Nippon Kayaku Company Limited)
• Original Assignee: Moxtek Inc (Nippon Kayaku Company Limited)
• Inventors: Wang, Dongbing
• Primary Examiner(s): Ho, Allen C.
• Application Number:
  US13/744,193
• Publication Number:
  US 20130136237A1
• Time in Patent Office: 747 Days
• Field of Search: 378/91, 378/117, 378/118, 378/121
• US Class Current: 378/121
• CPC Class Codes: H05G 1/08 Electrical details
• CPC Class Codes: H05G 1/12 with dc or rectified single-phase ac or double-phase
• CPC Class Codes: H05G 1/265 Measurements of current, voltage or power

Abstract

A high voltage sensing resistor disposed on a cylinder that at least partially surrounds an evacuated enclosure of an x-ray tube.

Claims

1. An x-ray source comprising:

a. an electrically insulative cylinder;

b. an x-ray tube comprising;

i. an evacuated chamber;

ii. an anode disposed at one end of the evacuated chamber;

iii. a cathode disposed at an opposite end of the evacuated chamber from the anode;

c. the electrically insulative cylinder circumscribing a portion of the evacuated chamber;

d. a first resistor and a second resistor electrically connected in series;

e. the first resistor;

i. comprising a line of electrically insulative dielectric ink painted on a surface of the electrically insulative cylinder;

ii. having a resistance of at least 10 mega ohms;

iii. including a first end attached to either the anode or the cathode; and

iv. including a second end electrically connected to a first end of the second resistor;

f. a resistance of the first resistor is at least 100 times higher than a resistance of the second resistor; and

g. a voltage measurement device connected across the second resistor and configured to measure a voltage across the second resistor.

2. The x-ray source of claim 1, wherein the first resistor wraps around a circumference of the electrically insulative cylinder at least five times.

3. The x-ray source of claim 1, wherein:

a. the electrically insulative cylinder comprises a single electrically insulative cylinder; and

b. the single electrically insulative cylinder forms at least a portion of the evacuated chamber along with the anode and the cathode.

4. The x-ray source of claim 1, wherein the first resistor extends in a first direction, then reverses in a second direction substantially opposite of the first direction, then reverses and extends again in the first direction, and repeats this reversal of direction at least three more times.

5. An x-ray source comprising:

a. an electrically insulative cylinder;

b. an x-ray tube comprising;

i. an evacuated chamber;

ii. an anode disposed at one end of the evacuated chamber;

iii. a cathode disposed at an opposing end of the evacuated chamber from the anode;

c. the electrically insulative cylinder at least partially surrounding the evacuated chamber; and

d. a first resistor;

i. comprising a line of electrically insulative material, having a length and a diameter and wherein the length is at least 10 times longer than the diameter;

ii. disposed directly on a surface of the electrically insulative cylinder;

iii. electrically connected to either the anode or the cathode at one end; and

iv. configured to be electrically connected to an external circuit at an opposing end.

6. The x-ray source of claim 5, wherein:

a. the electrically insulative cylinder comprises a first electrically insulative cylinder and a second electrically insulative cylinder;

b. the first electrically insulative cylinder forms at least a portion of the evacuated chamber along with the anode and the cathode;

c. the second electrically insulative cylinder at least partially surrounds the first electrically insulative cylinder; and

d. the line of electrically insulative material is disposed on a surface of the second electrically insulative cylinder.

7. The x-ray source of claim 6, wherein:

a. a gap between the first electrically insulative cylinder and the second electrically insulative cylinder is between 0.5 millimeters and 5 millimeters; and

b. electrically insulative potting material substantially fills the gap.

8. The x-ray source of claim 6, wherein the first resistor is a dielectric ink painted on the surface of the second electrically insulative cylinder.

9. The x-ray source of claim 8, wherein the line of electrically insulative material is disposed on an inside surface of the second electrically insulative cylinder.

10. The x-ray source of claim 8, wherein the line of electrically insulative material is disposed on an outside surface of the second electrically insulative cylinder.

11. The x-ray source of claim 5, wherein a resistance across the first resistor from one end to the other end is at least 10 mega ohms.

12. The x-ray source of claim 5, further comprising:

a. a second resistor connected in series with the first resistor;

b. the second resistor having a resistance of at least 1 kiloohm less than a resistance of the first resistor; and

c. a voltage measurement device connected across the second resistor and configured to measure a voltage across the second resistor.

13. The x-ray source of claim 12, wherein the second resistor is a line of electrically insulative material disposed on the electrically insulative cylinder.

14. The x-ray source of claim 12, wherein the resistance of the first resistor is at least 1000 times higher than the resistance of the second resistor.

15. The x-ray source of claim 5, wherein the first resistor wraps around a circumference of the electrically insulative cylinder at least five times.

16. The x-ray source of claim 5, wherein the first resistor extends in a first direction, then reverses in a second direction substantially opposite of the first direction, then reverses and extends again in the first direction, and repeats this reversal of direction at least three more times.

17. The x-ray source of claim 5, wherein:

a. the electrically insulative cylinder comprises a single electrically insulative cylinder;

b. the single electrically insulative cylinder forms at least a portion of the evacuated chamber along with the anode and the cathode; and

c. the first resistor is disposed on an outer surface of the single electrically insulative cylinder.

18. The x-ray source of claim 17, wherein the first resistor is a dielectric ink painted on the outer surface of the single electrically insulative cylinder.

19. The x-ray source of claim 5, wherein the first resistor comprises beryllium oxide.

20. A method for sensing a voltage across an x-ray tube, the method comprising:

a. painting electrically insulative material on a surface of an electrically insulative cylinder, the electrically insulative material comprising a first resistor, the electrically insulative cylinder surrounding at least a portion of an evacuated chamber of the x-ray tube;

b. connecting the first resistor to a second resistor at one end and to either a cathode or an anode of the x-ray tube at an opposing end;

c. connecting an opposing end of the second resistor to ground;

d. measuring a voltage across the second resistor; and

e. calculating a voltage across the x-ray tube by