A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators

Xu Yunlin, Marek Flaska, Sara Pozzi, Vladimir Protopopescu, Thomas Downar

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Citations (Scopus)

Abstract

In this paper, we present a neutron spectrum unfolding technique based on a modification of the least-squares method. The main innovation is the use of a Krylov subspace iteration method to solve the least-squares normal equations. This method was employed because it performs better on ill-conditioned systems of linear equations as compared with standard direct-solution methods. Three different least-squares solution techniques are compared and evaluated in terms of (i) accuracy in the prediction of the energy spectrum, (ii) computational efficiency, and (iii) robustness to noise. The unfolding is performed on measured pulse-height distributions as well as pulse height distributions generated with the Monte Carlo code MCNP-PoliMi. Using this code, neutron energy depositions on the constituents of the scintillator are individually tracked, and the light output generated at each interaction is suitably accounted for. This procedure allows for a very accurate simulation of the liquid scintillator detector response. The precise knowledge of the neutron energy spectrum provides information not only about the presence or absence of fissile material, but also about the characteristics of the material. We show that the proposed technique performs well in the unfolding of neutron pulse-height distributions from Monte Carlo simulations, and fairly well for a measured distribution from a Cf-252 neutron source.

Original languageEnglish (US)
Title of host publicationJoint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007
StatePublished - Dec 3 2007
EventJoint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007 - Monterey, CA, United States
Duration: Apr 15 2007Apr 19 2007

Publication series

NameJoint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007

Other

OtherJoint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007
CountryUnited States
CityMonterey, CA
Period4/15/074/19/07

Fingerprint

Scintillator
Sequential Algorithm
neutron spectra
Least Square Algorithm
pulse amplitude
Unfolding
Neutron
scintillation counters
Liquid
liquids
Energy Spectrum
energy spectra
fissionable materials
neutrons
linear equations
neutron sources
least squares method
Normal Equations
Subspace Methods
Least-squares Solution

All Science Journal Classification (ASJC) codes

  • Mathematics(all)
  • Nuclear and High Energy Physics

Cite this

Yunlin, X., Flaska, M., Pozzi, S., Protopopescu, V., & Downar, T. (2007). A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators. In Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007 (Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007).
Yunlin, Xu ; Flaska, Marek ; Pozzi, Sara ; Protopopescu, Vladimir ; Downar, Thomas. / A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators. Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007. 2007. (Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007).
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abstract = "In this paper, we present a neutron spectrum unfolding technique based on a modification of the least-squares method. The main innovation is the use of a Krylov subspace iteration method to solve the least-squares normal equations. This method was employed because it performs better on ill-conditioned systems of linear equations as compared with standard direct-solution methods. Three different least-squares solution techniques are compared and evaluated in terms of (i) accuracy in the prediction of the energy spectrum, (ii) computational efficiency, and (iii) robustness to noise. The unfolding is performed on measured pulse-height distributions as well as pulse height distributions generated with the Monte Carlo code MCNP-PoliMi. Using this code, neutron energy depositions on the constituents of the scintillator are individually tracked, and the light output generated at each interaction is suitably accounted for. This procedure allows for a very accurate simulation of the liquid scintillator detector response. The precise knowledge of the neutron energy spectrum provides information not only about the presence or absence of fissile material, but also about the characteristics of the material. We show that the proposed technique performs well in the unfolding of neutron pulse-height distributions from Monte Carlo simulations, and fairly well for a measured distribution from a Cf-252 neutron source.",
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Yunlin, X, Flaska, M, Pozzi, S, Protopopescu, V & Downar, T 2007, A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators. in Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007. Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007, Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007, Monterey, CA, United States, 4/15/07.

A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators. / Yunlin, Xu; Flaska, Marek; Pozzi, Sara; Protopopescu, Vladimir; Downar, Thomas.

Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007. 2007. (Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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T1 - A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators

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AU - Downar, Thomas

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N2 - In this paper, we present a neutron spectrum unfolding technique based on a modification of the least-squares method. The main innovation is the use of a Krylov subspace iteration method to solve the least-squares normal equations. This method was employed because it performs better on ill-conditioned systems of linear equations as compared with standard direct-solution methods. Three different least-squares solution techniques are compared and evaluated in terms of (i) accuracy in the prediction of the energy spectrum, (ii) computational efficiency, and (iii) robustness to noise. The unfolding is performed on measured pulse-height distributions as well as pulse height distributions generated with the Monte Carlo code MCNP-PoliMi. Using this code, neutron energy depositions on the constituents of the scintillator are individually tracked, and the light output generated at each interaction is suitably accounted for. This procedure allows for a very accurate simulation of the liquid scintillator detector response. The precise knowledge of the neutron energy spectrum provides information not only about the presence or absence of fissile material, but also about the characteristics of the material. We show that the proposed technique performs well in the unfolding of neutron pulse-height distributions from Monte Carlo simulations, and fairly well for a measured distribution from a Cf-252 neutron source.

AB - In this paper, we present a neutron spectrum unfolding technique based on a modification of the least-squares method. The main innovation is the use of a Krylov subspace iteration method to solve the least-squares normal equations. This method was employed because it performs better on ill-conditioned systems of linear equations as compared with standard direct-solution methods. Three different least-squares solution techniques are compared and evaluated in terms of (i) accuracy in the prediction of the energy spectrum, (ii) computational efficiency, and (iii) robustness to noise. The unfolding is performed on measured pulse-height distributions as well as pulse height distributions generated with the Monte Carlo code MCNP-PoliMi. Using this code, neutron energy depositions on the constituents of the scintillator are individually tracked, and the light output generated at each interaction is suitably accounted for. This procedure allows for a very accurate simulation of the liquid scintillator detector response. The precise knowledge of the neutron energy spectrum provides information not only about the presence or absence of fissile material, but also about the characteristics of the material. We show that the proposed technique performs well in the unfolding of neutron pulse-height distributions from Monte Carlo simulations, and fairly well for a measured distribution from a Cf-252 neutron source.

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M3 - Conference contribution

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BT - Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007

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Yunlin X, Flaska M, Pozzi S, Protopopescu V, Downar T. A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators. In Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007. 2007. (Joint International Topical Meeting on Mathematics and Computations and Supercomputing in Nuclear Applications, M and C + SNA 2007).