US 4,152,596 AGranted

Apparatus for reducing pulse pileup in an elemental analyzer measuring gamma rays arising from neutron capture in bulk substances

AssigneeMDH Industries, Inc.

InventorJ. Howard Marshall, III

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Abstract

The active reduction of the number of analyzed events with pulse amplitudes which pileup has distorted improves measurement accuracy and response time in an apparatus for neutron-capture-based on-line elemental analysis of bulk substances. Within the apparatus, the analyzed bulk substance is exposed to neutrons, and neutron capture generates prompt gamma rays therefrom. A detector interacts with some of these gamma rays to produce electrical signals used to measure their energy spectrum by pulse-height analysis. Circuits associated with this pulse-height analysis also detect the pileup of the signals of two or more independent gamma rays using one or more of several techniques. These techniques include multiple outputs from a special amplifier-discriminator system, which has been optimized for low pulse-pair resolving time and may have adaptive thresholds, and the requirement that the relative amplitudes of the outputs of slow and fast amplifiers be consistent with a single event producing both outputs. Pulse-width measurements are also included in the pileup detection.

Claims23

Dependent claims

In an apparatus for the on-line analysis of the composition of a bulk substance, wherein said analysis includes the production and capture of neutrons and the detection and measurement of the energy spectrum of the resulting capture gamma rays, an improvement for reducing the deleterious effects of pulse pileup, the improvement comprising, in combination:

(a) a gamma-ray detector operably associated with the bulk substance which is exposed to neutrons to generate capture gamma rays, the detector producing electrical signals indicative of the energies of the gamma rays to provide for the measurement of their energy spectrum;
(b) slow-amplifier means connected to the output of the gamma-ray detector, the slow-amplifier means producing a pulse of sufficient width that satisfactory resolution can be obtained in the energy-spectrum measurement;
(c) fast-amplifier means also connected to the output of the gamma-ray detector, the fast-amplifier means producing a pulse with a width chosen to optimize the detection of pulse pileup;
and
(d) amplitude-correlation means connected to the outputs of the slow-amplifier means and of the fast-amplifier means, the amplitude-correlation means detecting an event where the amplitude of the pulse produced by the slow-amplifier means is inconsistent with the amplitude of the pulse produced by the fast-amplifier means,
whereby events with pulse amplitudes which pileup has distorted can be eliminated from the measurement of the energy spectrum of the capture gamma rays.

3 more elements

(a) a gamma-ray detector operably associated with the bulk substance which is exposed to neutrons to generate capture gamma rays, the detector producing electrical signals indicative of the energies of the gamma rays to provide for the measurement of their energy spectrum;
(b) fast-amplitude means connected to the output of the gamma-ray detector, the fast-amplifier means producing a pulse with a width chosen to optimize the detection of pulse pileup;
and
(c) means for pulse-width measurement connected to the output of the fast-amplifier means, the width-measuring means producing an electrical signal which is indicative of the width of the pulse at the output of the fast-amplifier means,
whereby events for which pulse pileup causes the pulse from the fast-amplifier means to be lengthened excessively can be rejected in order to reduce in the measurement of the energy spectrum of the capture gamma rays the number of events with amplitudes which pileup has distorted.

2 more elements

(a) a gamma-ray detector operably associated with the bulk substance which is exposed to neutrons to generate capture gamma rays, the detector producing electrical signals indicative of the energies of the gamma rays to provide for the measurement of their energy spectrum;
(b) fast-amplifier means connected to the output of the gamma-ray detector, the fast-amplifier means producing a pulse with a width chosen to optimize the detection of pulse pileup;
and
(c) means for indicating the presence of a plurality of pulses exceeding an amplitude threshold during a known time interval following the first pulse exceeding said threshold, wherein the threshold depends upon the measured pulse amplitude, the means for indicating the presence of a plurality of pulses being connected to the output of the fast-amplifier means,
whereby events including more than one pulse during the interval necessary to perform the energy measurement can be detected in order to reduce in the measurement of the energy spectrum of the capture gamma rays the number of events with amplitudes which pileup has distorted.

2 more elements

Dependencies are inferred from the claim text.