High throughput pulse height analyzer

Patent metadata

Field	Value
Publication number	US-9703004-B2
Application number	US-201615157023-A
Country	US
Kind code	B2
Filing date	May 17, 2016
Priority date	May 17, 2011
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

A method and system for acquiring spectral information from an energy sensitive nuclear detector is disclosed. The method includes detecting nuclear radiation at a detection device and generating an electronic input pulse indicative of energy deposited in the detection device. The method further includes integrating the electronic input pulse at an integrating device to produce an integrated output signal and digitally sampling the integrated output signal of the integrating device at intervals to produce a stream of digital samples. The method further includes resetting the integrator synchronously with a sampling clock when a limit condition is reached.

First claim

What is claimed is:

1. A method for acquiring spectral information from an energy sensitive nuclear detector comprising:
detecting nuclear radiation at a detection device and generating an electronic input pulse indicative of energy deposited in the detection device;
integrating the electronic input pulse at an integrating device to produce an integrated output signal;
digitally sampling the integrated output signal of the integrating device at intervals to produce a stream of digital samples; and
resetting the integrator synchronously with a sampling clock when a limit condition is reached,
wherein pulse acquisition and integration continue without interruption during the resetting of the integrator.

2. The method of claim 1 , further comprising determining and calibrating the integrated output signal during a quiescent period of the integrating device.

3. The method of claim 2 , wherein the quiescent period comprises an off-period of a pulsed neutron generator.

4. The method of claim 1 , wherein the integrating device produces the integrated output signal as a difference between a first sample after an end of integration of the electronic input pulse and a sample preceding a start of the electronic input pulse compensated by a quiescent integral for a same length of time.

5. The method of claim 2 , further comprising disabling the electronic input pulse to create a quiescent period for the calibration.

6. The method of claim 1 , further comprising digitally differentiating the stream of digital samples and obtaining a digital representation of the electronic input pulse.

7. The method of claim 6 , further comprising estimating a baseline from the digitally differentiated stream of digital samples.

8. The method of claim 6 , further comprising shaping the digitally differentiated stream of digital samples, thereby reducing the pulse length and improving pile up detection.

9. The method of claim 8 , further comprising basing pile up detection on the shape of the digitally differentiated stream of digital samples.

10. The method of claim 8 , further comprising determining a pulse arrival time based on a threshold crossing of the digitally differentiated stream of digital samples.

11. The method of claim 8 , further comprising processing the detected pile up to remove the effect of the pile up on the pulse, resulting in a restored initial pulse.

12. The method of claim 1 , further comprising analysis of the shape of the digital representation to distinguish pulses coming from the interaction of different kinds of nuclear radiation with the nuclear detector.

13. A downhole tool for acquiring spectral information, comprising:
a generator configured to emit nuclear radiation into an earth formation surrounding a borehole;
a nuclear detector, and;
data processing circuitry configured to detect nuclear radiation and generate an electronic signal indicative of the energy deposited in a detection device;
data processing circuitry configured to integrate the electronic signal indicative of the energy deposited in a detection device to produce an output signal;
data processing circuitry configured to digitally sample the output signal at an interval to produce a digitized pulse stream;
data processing circuitry configured to obtain the integral of the electronic signal from the digitized pulse stream and reset the data processing circuitry for integrating synchronously with a sampling clock when a limit condition is reached, wherein pulse acquisition and integration continue without interruption during the resetting of the integrator.

14. The tool of claim 13 , further comprising a downhole memory in which acquired pulse heights are stored in a histogram.

15. The tool of claim 13 , further comprising a link to a memory storage device at an uphole location, wherein said link transfers acquired pulse heights for storage in the memory storage device.

16. The tool of claim 13 , said tool further comprising a conveyance means selected from the group consisting of wireline, slickline, coiled tubing, drillstring, and wired drill pipe.

17. The tool of claim 13 , wherein the nuclear detector comprises a material selected from the group consisting of NaI, LaBr, LaCl, GSO, LSO, YAP, LuAG, LuAP, and LPS.

18. The tool of claim 13 , wherein the generator comprises a pulsed neutron generator such as a d-T, t-T or d-D generator.

19. The tool of claim 13 , where the generator comprises a DC x-ray generator comprising one of a pulsed device, a linear accelerator, and a circular accelerator.

20. The tool of claim 19 , where the DC x-ray generator is configured for pulsed operation including off periods for predetermined time intervals, resulting in a quiescent signal period.

Assignees

• Schlumberger Technology Corp

Inventors

• Jorion Bruno

Classifications

• G01V5/12

  using gamma or X-ray sources {(gamma sources using isotopes G21G4/00; X-ray tubes H01J35/00)} · CPC title

• G01T3/001

  Spectrometry · CPC title

• G01V5/10 Primary

  using neutron sources {(neutron generating tubes H05H5/00; neutron sources using isotopes G21G4/00)} · CPC title

• G01V13/00

  Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00 · CPC title

• G01V5/102 Primary

  the neutron source being of the pulsed type · CPC title