# US 2014/0197307 A1 · High Throughput Pulse Height Analyzer

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- Number: US 2014/0197307 A1
- Document ID: US20140197307A1
- Status: Published application
- Kind: A1
- Application number: 14/116,314
- Filed: 2012-05-16
- Published: 2014-07-17
- Earliest claimed: 2011-05-17
- Assignees: Schlumberger Technology Corporation
- Inventors: Bruno Jorion
- Web page: https://patentgrep.com/patent/US20140197307A1

## CPC

- G01V 5/102: {the neutron source being of the pulsed type}
- G01T 1/17: Circuit arrangements not adapted to a particular type of detector {(pulse-selection circuits H03K, G01R)}
- G01T 1/171: {Compensation of dead-time counting losses}
- G01T 1/362: {with scintillation detectors}
- G01T 3/001: {Spectrometry}
- G01V 5/10: using neutron sources {(neutron generating tubes H05H5/00; neutron sources using isotopes G21G4/00)}
- G01V 5/12: using gamma or X-ray sources {(gamma sources using isotopes G21G4/00; X-ray tubes H01J35/00)}
- G01V 13/00: Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00
- G01V 2210/40: Transforming data representation
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)
- G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00)

## 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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

The method of claim 1, wherein pulse acquisition and integration continue without interruption during the resetting of the integrator.

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 3)

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

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 3)

The method of claim 3, further comprising disabling the electronic input pulse to create a quiescent period for the calibration.

### Claim 7 (depends on 1)

The method of claim 1, wherein the digital sampling interval is predetermined.

### Claim 8 (depends on 1)

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

### Claim 9 (depends on 8)

The method of claim 8, further comprising estimating a baseline from the digitally differentiated stream of digital samples.

### Claim 10 (depends on 8)

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

### Claim 11 (depends on 10)

The method of claim 10, further comprising basing pile up detection on the shape of the digitally differentiated stream of digital samples.

### Claim 12 (depends on 10)

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

### Claim 13 (depends on 12)

The method of claim 12, further comprising storing the pulse arrival time with respect to a predetermined start time in a time spectrum.

### Claim 14 (depends on 11)

The method of claim 11, further comprising flagging a pile up.

### Claim 15 (depends on 10)

The method of claim 10, further comprising integrating the digitally differentiated pulse and storing the resulting integral in a pulse height histogram.

### Claim 16 (depends on 15)

The method of claim 15, wherein a pulse flagged as a pile up is stored in a histogram distinct from the pulse height histogram.

### Claim 17 (depends on 11)

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

### Claim 18 (depends on 17)

The method of claim 17, where the restored initial pulse is stored in a pulse height histogram.

### Claim 19 (depends on 17)

The method of claim 17, where an arrival time of a second pulse in the detected pile up is stored in an arrival time histogram.

### Claim 20 (depends on 10)

The method of claim 10, where the shaping accounts for a presence of more than one detector time decay constant.

### Claim 21 (depends on 10)

The method of claim 10, wherein the shaping accounts for non-ideal behavior of the integrating device.

### Claim 22 (depends on 8)

The method of claim 8, 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.

### Claim 23 (depends on 22)

The method of claim 22, where the different kinds of nuclear radiation are gamma-rays and neutrons.

### Claim 24 (depends on 23)

The method of claim 23, where the detector is a scintillation detector exhibiting a pulse shape, which is different between neutrons and gamma-rays.

### Claim 25 (depends on 24)

The method of claim 24, where the detector is an Elpasolite detector

### Claim 26

An apparatus for acquiring spectral information from an energy sensitive nuclear detector, comprising:
electronic means for detecting nuclear radiation and generating an electronic signal indicative of the energy deposited in a detection device;
an integrator for integrating the electronic signal indicative of the energy deposited in a detection device;
electronic means to digitally sample the output signal of the integrator at an interval to produce a digitized pulse stream;
electronic means for obtaining the integral of the electronic signal from the digitized pulse stream and resetting the integrator synchronously with a sampling clock when a limit condition is reached.

### Claim 27 (depends on 26)

The apparatus of claim 26, wherein pulse acquisition and integration continue without interruption during the resetting of the integrator.

### Claim 28 (depends on 26)

The apparatus of claim 26, wherein the electronic signal is generated at a scintillation detector coupled to a photomultiplier.

### Claim 29 (depends on 26)

The apparatus of claim 26, wherein the scintillation detector comprises a detector material selected from the group consisting of NaI, LaBr, LaCl, GSO, LSO, YAP, LuAG, LuAP, and LPS.

### Claim 30 (depends on 26)

The apparatus of claim 26, wherein the nuclear radiation comprises gamma-rays caused by the interaction of neutrons with matter.

### Claim 31 (depends on 30)

The apparatus of claim 30, wherein the nuclear radiation comprises neutrons generated by a radioisotope source.

### Claim 32 (depends on 30)

The apparatus of claim 30, wherein the radioisotope source comprises a source material selected from the group consisting of 241AmBe and 252Cf.

### Claim 33 (depends on 26)

The apparatus of claim 26, wherein the nuclear radiation comprises neutrons generated by a pulsed neutron generator such as a d-T, t-T or d-D generator.

### Claim 34 (depends on 26)

The apparatus of claim 26, where the nuclear radiation is generated by an x-ray generator.

### Claim 35 (depends on 34)

The apparatus of claim 34 the x-ray generator comprising a DC x-ray generator.

### Claim 36 (depends on 34)

The apparatus of claim 34, where the x-ray generator is configured for pulsed operation including off periods for predetermined time intervals, resulting in a quiescent signal period.

### Claim 37 (depends on 26)

The apparatus of claim 26, the x-ray generator comprising one of a pulsed device, a linear accelerator, and a circular accelerator.

### Claim 38

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.

### Claim 39 (depends on 38)

The tool of claim 38, further comprising a downhole memory in which acquired pulse heights are stored in a histogram

### Claim 40 (depends on 38)

The tool of claim 38, 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.

### Claim 41 (depends on 38)

The tool of claim 38, said tool further comprising a conveyance means selected from the group consisting of wireline, slickline, coiled tubing, drillstring, and wired drill pipe.