Photomultiplier and detection systems

• US 8,993,970 B2
• Filed: 11/18/2013
• Issued: 03/31/2015
• Est. Priority Date: 06/11/2008
• Status: Active Grant

• Current Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Original Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Inventors: Morton, Edward James
• Primary Examiner(s): Kim, Kiho
• Application Number:
  US14/082,658
• Publication Number:
  US 20140348293A1
• Time in Patent Office: 498 Days
• Field of Search: 25036301-3631
• US Class Current: 250/363.02
• CPC Class Codes: G01T 1/16 Measuring radiation intensity G01T1/29 takes precedence ; self-powered detectors G01T3/006; using an ionisation chamber filled with a liquid or solid, e.g. frozen liquid, dielectric G01T3/008
• CPC Class Codes: G01T 1/167 Measuring radioactive content of objects, e.g. contamination whole body counters G01T1/163
• CPC Class Codes: G01T 1/208 Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section
• CPC Class Codes: G01T 3/06 with scintillation detectors
• CPC Class Codes: G01V 5/222 measuring scattered radiation
• CPC Class Codes: G01V 5/281 detecting special nuclear material [SNM], e.g. Uranium-235, Uranium-233 or Plutonium-239
• CPC Class Codes: H01J 40/04 Electrodes
• CPC Class Codes: H01J 43/08 Cathode arrangements construction of photo cathodes H01J40/06, H01J40/16, H01J47/00, H01J49/08
• CPC Class Codes: H01J 43/18 Electrode arrangements using essentially more than one dynode
• CPC Class Codes: H01J 43/30 Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for

Abstract

The invention provides a switchable photomultiplier switchable between a detecting state and a non-detecting state including a cathode upon which incident radiation is arranged to impinge. The photomultiplier also includes a series of dynodes arranged to amplify a current created at the cathode upon detection of photoradiation. The invention also provides a detection system arranged to detect radiation-emitting material in an object. The system includes a detector switchable between a detecting state in which the detector is arranged to detect radiation and a non-detecting state in which the detector is arranged to not detect radiation. The system further includes a controller arranged to control switching of the detector between the states such that the detector is switched to the non-detecting state while an external radiation source is irradiating the object.

Claims

1. An inspection system for scanning an object for threat materials comprising:

a plurality of passive detectors configured to detect passive radiation emitted from material in the scanned object;

an active detection system comprising a radiation source to irradiate the scanned object and a plurality of active detectors configured to detect radiation emitted by said radiation source after it passes through and/or is scattered by the scanned object; and

a control system configured to perform the functions of controlling a switching of passive detectors between a detecting state and a non-detecting state such that the passive detectors are switched to a non-detecting state when the active radiation source is irradiating the object;

receiving separate sets of detection data from the plurality of passive and active detectors; and

correlating said separate sets of detection data to estimate a presence of threat materials in the scanned object.

2. The inspection system for scanning an object according to claim 1, wherein said passive detectors comprise an array of detectors.

3. The inspection system for scanning an object according to claim 1, wherein said plurality of passive detectors are configured in a predetermined spatial position with respect to said plurality of active detectors.

4. The inspection system for scanning an object according to claim 3, wherein the predetermined spatial positioning of said plurality of passive and active detectors is correlated with the separate sets of detection data for estimating the presence of threat materials in the scanned object.

5. The inspection system for scanning an object according to claim 4, wherein a speed of a moving scanned object is monitored and correlated with the separate sets of detection data to estimate the presence of threat materials in said object.

6. The inspection system for scanning an object according to claim 1, wherein said control system further controls a displaying of information received from said plurality of active and passive detectors simultaneously on a display monitor for viewing by a system operator.

7. The inspection system for scanning an object according to claim 1, wherein the control system switches only a subset of passive detectors in a non-detecting state depending on the spatial positioning of said subset of passive detectors with respect to spatial positioning of said plurality of active detectors.

8. The inspection system for scanning an object according to claim 1, wherein the control system switches only a subset of passive detectors in a non-detecting state depending on the direction of the radiation emitted by said radiation source.

9. The inspection system for scanning an object according to claim 1, wherein each of said plurality of passive detectors comprise a switchable photomultiplier which is adapted to be switchable between a detecting state and a non-detecting state.

10. The inspection system for scanning an object according to claim 9, wherein said switchable photomultiplier comprises a cathode arranged to receive an incident radiation;

a plurality of electrodes; and

a first electrode of the plurality of electrodes, wherein said first electrode is operatively closest to the cathode relative to other of said plurality of electrodes, wherein said first electrode is at a first potential and wherein an electrical potential of the cathode is switchable between a second potential, below the first potential, when the photomultiplier is in a detecting state and a third potential, above the second potential, when the photomultiplier in a non-detecting state.

11. The inspection system for scanning an object according to claim 1, wherein each of said plurality of passive detectors comprises a photomultiplier tube.

12. The inspection system for scanning an object according to claim 11, wherein each of said photomultiplier tubes is coupled to a shaper circuit, a discriminator and a digital data buffer.

13. The inspection system for scanning an object according to claim 1, wherein said passive detectors comprise a gamma detector.

14. The inspection system for scanning an object according to claim 1, wherein said radiation source comprise an X-ray source.

15. An inspection system for scanning an object for threat materials comprising:

a plurality of passive detectors configured to detect the passive radiation emitted from any radiation emitting material in a scanned object;

an active detection system comprising a radiation source to irradiate the scanned object and a plurality of active detectors configured to detect radiation emitted by said radiation source after it passes through and/or is scattered by the scanned object;

a control system configured to control the switching of passive detectors between a detecting state and a non-detecting state such that the passive detectors are switched to a non-detecting state when the radiation source is irradiating the object.

16. The inspection system for scanning an object according to claim 15, wherein the inspection system correlates data received from said plurality of active detectors with data received from said plurality of passive detectors to estimate a presence of threat materials in the scanned object.

17. The inspection system for scanning and object according to claim 15, wherein a relative spatial positioning of said plurality of active detectors and said plurality of passive detectors is correlated with data received from said detectors to estimate the presence of threat materials in the scanned object.

18. The inspection system for scanning an object according to claim 16, wherein each of said plurality of passive detectors comprise a switchable photomultiplier which is adapted to be switchable between a detecting state and a non-detecting state.