Extraction of correlated count rates using various gate generation techniques: Part I theory

In the measurement field of international nuclear safeguards, passive neutron coincidence counting is used to quantify the spontaneous fission rate of certain special nuclear materials. The shift register autocorrelation analysis method is the most commonly used approach. However, the Feynman-Y technique, which is more commonly applied in reactor noise analysis, provides an alternative means to extract the correlation information from a pulse train. In this work we consider how to select the optimum gate width for each of these two time-correlation analysis techniques. The optimum is considered to be that which gives the lowest fractional precision on the net doublets rate. Our theoretical approach is approximate but is instructional in terms of revealing the key functional dependence. We show that in both cases the same performance figure of merit applies so that common design criteria apply to the neutron detector head. Our prediction is that near optimal results, suitable for most practical applications, can be obtained from both techniques using a common gate width setting. The estimated precision is also comparable in the two cases. The theoretical expressions are tested experimentally using 252 Cf spontaneous fission sources measured in two thermal well counters representative of the type in common use by international inspectorates. Fast accidental sampling was the favored method of acquiring the Feynman-Y data. Our experimental study confirmed the basic functional dependences predicted although experimental results when available are preferred. With an appropriate gate setting Feynman-Y analysis provides an alternative to shift register analysis for safeguards applications which opening up new avenues of data collection and data reduction to explore.

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“…In terms of the RTI number distribution we can write the second order multiplet rate as follows [7,8]:…”

Section: Optimum Gate Width Selection -Feynman-y (Rti) Analysismentioning

confidence: 99%

The optimum choice of gate width for neutron coincidence counting

Croft¹,

Henzlová²,

Favalli³

et al. 2014

Nuclear Instruments and Methods in Physics Research Section A:

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“…Depending on the method used for the analysis, various combinations of gate generators, delay lines, shift register coincidence circuits and variable dead time circuits [6,7,9,10] are used to acquire the data in the experiment. Work related to gate width optimisation and gate generation technique was reported recently [11,12]. Thus the configuration of electronics modules for acquisition of data is specific to the theoretical method used for the data analysis.…”

Section: Introductionmentioning

confidence: 99%

Development and testing of neutron pulse time stamping data acquisition system for neutron noise experiment

Kumar

Ali

Degweker

et al. 2015

Nuclear Instruments and Methods in Physics Research Section A:

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“…The latter approach is typically employed to perform Feynman variance-to-mean analysis, however, the information contained in the random-gate multiplicity distribution generated using the long delay may also be used to extract correlated events as shown in [5]. A link between the Feynman variance-to-mean analysis and PNMC was recently established and discussed in detail in [5][6][7] and relies on the realization that multiplicity distribution constructed from series of random-gates can itself be utilized to extract the genuine correlated multiplicity rates. This approach was termed Randomly Triggered Interrogation (RTI).…”

Section: Introductionmentioning

confidence: 99%

“…Theoretical expressions for triggered-gate as well as randomgate GUF values are available [7,8] and generally rely on a single die-away time assumption, derived for an idealized detection system, where neutron population lifetime can be described by a single exponential. The corresponding expressions are written as follows:…”

Section: Introductionmentioning

confidence: 99%

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The impact of gate width setting and gate utilization factors on plutonium assay in passive correlated neutron counting

Henzlová

Menlove

Croft

et al. 2015

Nuclear Instruments and Methods in Physics Research Section A:

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a b s t r a c tIn the field of nuclear safeguards, passive neutron multiplicity counting (PNMC) is a method typically employed in non-destructive assay (NDA) of special nuclear material (SNM) for nonproliferation, verification and accountability purposes. PNMC is generally performed using a well-type thermal neutron counter and relies on the detection of correlated pairs or higher order multiplets of neutrons emitted by an assayed item. To assay SNM, a set of parameters for a given well-counter is required to link the measured multiplicity rates to the assayed item properties. Detection efficiency, die-away time, gate utilization factors (tightly connected to die-away time) as well as optimum gate width setting are among the key parameters. These parameters along with the underlying model assumptions directly affect the accuracy of the SNM assay. In this paper we examine the role of gate utilization factors and the single exponential die-away time assumption and their impact on the measurements for a range of plutonium materials. In addition, we examine the importance of item-optimized coincidence gate width setting as opposed to using a universal gate width value. Finally, the traditional PNMC based on multiplicity shift register electronics is extended to Feynman-type analysis and application of this approach to Pu mass assay is demonstrated.

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Extraction of correlated count rates using various gate generation techniques: Part I theory

Cited by 29 publications

References 4 publications

The optimum choice of gate width for neutron coincidence counting

The optimum choice of gate width for neutron coincidence counting

Development and testing of neutron pulse time stamping data acquisition system for neutron noise experiment

The impact of gate width setting and gate utilization factors on plutonium assay in passive correlated neutron counting

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