Mobile X-ray unit

• US 6,205,200 B1
• Filed: 10/28/1996
• Issued: 03/20/2001
• Est. Priority Date: 10/28/1996
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Seely, John F., Holland, Glenn E., Boyer, Craig N.
• Primary Examiner(s): Porta, David P.
• Application Number:
  US08/738,927
• Time in Patent Office: 1,604 Days
• Field of Search: 378/101, 378/102, 378/103, 378/106, 378/114
• US Class Current: 378/101
• CPC Class Codes: H05G 1/06 X-ray tube and at least part of the power supply apparatus being mounted within the same housing
• 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

Abstract

A portable X-ray unit, of a relatively light-weight, occoping a volume of less then one-half a cubic foot containing an x-ray head assembly, a unique Marx generator, a plurality of spark-gap switches and control electronics is disclosed. The Marx generator allows for the development of a relatively high voltage in excess of 100 kV, yet allows for the discharge thereof within the nanosecond range. The Marx generator is enclosed by an acrylic insulator that cooperates with an aluminum enclosure, which functions as a return current path for the capacitors in the Marx generator and also as a shield against the escape of electromagnetic radiation from the pulsed x-ray unit. The Marx generator and spark-gap switches are confined within the pressurized chamber that may contain nitrogen gas to reduce the separation of the gap in the spark-gap switches.

Claims

1. A mobile X-ray unit comprising:

an X-ray tube having an anode and a cathode and an anode-cathode gap therebetween;

a power supply for providing a predetermined voltage;

control electronics having first input and first output stages, said first input stage being responsive to at least one input pulse for generating a first trigger pulse at said first output stage; and

a Marx generator having second input and second output stages, said second output stage being coupled across said anode and said cathode of said x-ray tube, said Marx generator comprising;

a plurality of spark gap switches, including first and last spark gap switches, and a UV photoionization source, each of said spark-gap switches and said UV source having anode and cathode electrodes spaced apart from each other by a predetermined distance and providing a high resistance path therebetween, said UV photoionization source generating a second trigger pulse which acts to sequentially close said plurality of spark-gap switches, said second input stage being coupled between said anode and said cathode electrodes of said first spark-gap switch;

a plurality of capacitors coupled to said power supply and arranged in parallel so that each capacitor is charged to said predetermined voltage from said power supply, said plurality of capacitors being arranged in cascade with said spark-gap switches so as to be discharged in series in response to said second trigger pulse and produce an output pulse at the output stage of the Marx generator having an amplitude that is proportional to the accumulative voltage to which said plurality of capacitors are charged.

2. The mobile X-ray unit of claim 1 wherein:

each of said plurality of capacitors is a ceramic disc formed of a barium titanate disc having a value of about 0.01 microfarads.

3. The mobile X-ray unit of claim 2 wherein:

said plurality of capacitors is responsive to said trigger pulse for serially discharging to produce a sum voltage equal to the accumulative voltage to which said plurality of capacitors are charged and applies this sum voltage to said anode of said X-ray tube.

4. The mobile X-ray unit of claim 3 wherein:

said X-ray tube is responsive to the sum voltage produced by the Marx generator for producing an X-ray pulse having a duration of about 50 nanoseconds.

5. The mobile X-ray unit of claim 1 wherein:

said plurality of capacitors are held on a polycarbonate rod having a spine configuration.

6. The mobile X-ray unit of claim 1 further including:

a plurality of clamping diodes respectively coupled in parallel with said plurality of capacitors for minimizing negative ringover in said plurality of capacitors upon discharge.

7. The mobile X-ray unit of claim 1 further including:

a conducting cylinder fitted over said Marx generator for providing a return path confining any unwanted electronic radiation.

8. The mobile X-ray unit of claim 7 wherein:

said insulating cylinder comprises an aluminum member fitted over an acrylic material.

9. The mobile X-ray unit of claim 1 further including a pressurized insulating cylinder, said insulating cylinder containing:

said Marx generator for preventing high voltage breakdown between said Marx generator and ground; and

a conducting cylinder closely fitted over the insulating cylinder for for providing a conducting return path for discharge of said capacitors within said Marx generator.

10. The mobile X-ray unit of claim 9 wherein:

said conducting cylinder is comprised of a light weight conductive metal.

11. The mobile X-ray unit of claim 10 wherein:

said conductive metal can be selected from the group consisting of aluminum, magnesium, titanium and combinations thereof.

12. The mobile X-ray unit of claim 9 wherein said insulating cylinder is selected from the group consisting of polycarbonate, acrylic, glass reinforced epoxy resins, and combinations thereof.

13. The mobile X-ray unit of claim 6 wherein:

said mobile X-ray unit is battery powered, completely portable, and occupies a volume less than one-half of a cubic foot.

14. The mobile X-ray unit of claim 3 wherein:

said plurality of capacitors, said plurality of spark gap switches, said plurality of clamping diodes, and the UV photoionization source are contained within said insulating cylinder.

15. The mobile X-ray unit of claim 8 wherein:

said plurality of spark gap switches are disposed in sequence along an optical path which facilitates the photoionozation of said plurality of spark gap switches.

16. The mobile X-ray unit of claim 1 wherein:

said UV photoionization source includes an anode wire surrounded by a ceramic insulator disposed within said cathode, said anode wire being responsive to said second voltage pulse from the control electronics for establishing a high current discharge across the surface of said ceramic insulator and producing thereby an intense hard ultraviolet pulse.