Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission

L. Barrón-Palos; R. Alarcon; S. Balascuta; C. Blessinger; J. D. Bowman; T. E. Chupp; S. Covrig; C. B. Crawford; M. Dabaghyan; J. Dadras; M. Dawkins; W. Fox; M. T. Gericke; R. C. Gillis; B. Lauss; M. B. Leuschner; B. Lozowski; R. Mahurin; M. Mason; J. Mei; H. Nann; S. I. Penttilä; W. D. Ramsay; A. Salas-Bacci; S. Santra; P. N. Seo; M. Sharma; T. Smith; W. M. Snow; W. S. Wilburn; V. Yuan

doi:10.1016/j.nima.2011.07.051

Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission

L. Barrón-Palos, R. Alarcon, S. Balascuta, C. Blessinger, J. D. Bowman, T. E. Chupp, S. Covrig, C. B. Crawford, M. Dabaghyan, J. Dadras, M. Dawkins, W. Fox, M. T. Gericke, R. C. Gillis, B. Lauss, M. B. Leuschner, B. Lozowski, R. Mahurin, M. Mason, J. MeiH. Nann, S. I. Penttilä, W. D. Ramsay, A. Salas-Bacci, S. Santra, P. N. Seo, M. Sharma, T. Smith, W. M. Snow, W. S. Wilburn, V. Yuan

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Abstract

The NPDGamma collaboration is performing a measurement of the very small parity-violating asymmetry in the angular distribution of the 2.2 MeV γ-rays from the capture of polarized cold neutrons on protons (A _γ). The estimated size of A_γ is 5×10^-8, and the measured asymmetry is proportional to the neutron polarization upon capture. Since the interaction of polarized neutrons with one of the two hydrogen molecular states (orthohydrogen) can lead to neutron spin-flip scattering, it is essential that the hydrogen in the target is mostly in the molecular state that will not depolarize the neutrons (≥99.8% parahydrogen). For that purpose, in the first stage of the NPDGamma experiment at the Los Alamos Neutron Science Center (LANSCE), we operated a 16-l liquid hydrogen target, which was filled in two different occasions. The parahydrogen fraction in the target was accurately determined in situ by relative neutron transmission measurements. The result of these measurements indicate that the fraction of parahydrogen in equilibrium was 0.9998±0.0002 in the first data taking run and 0.9956±0.0002 in the second. We describe the parahydrogen monitor system, relevant aspects of the hydrogen target, and the procedure to determine the fraction of parahydrogen in the target. Also assuming thermal equilibrium of the target, we extract the scattering cross-section for neutrons on parahydrogen.

Original language	English
Pages (from-to)	579-586
Number of pages	8
Journal	Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume	659
Issue number	1
DOIs	https://doi.org/10.1016/j.nima.2011.07.051
State	Published - Dec 11 2011

Funding

This work was supported in part by the U.S. Department of Energy ( Office of Energy Research , under Contract W-7405-ENG-36 ), the National Science Foundation (Grants no. PHY-0100348, PHY-0457219, and PHY-0758018 ), the NSF Major Research Instrumentation program ( NSF-0116146 ), the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Japanese Grant-in-Aid for Scientific Research A12304014 .

Keywords

Hadronic weak interaction
Liquid hydrogen
Neutron capture
Neutron polarization
Neutron scattering
Orthohydrogen
Parahydrogen
Parity violation

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10.1016/j.nima.2011.07.051

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Barrón-Palos, L., Alarcon, R., Balascuta, S., Blessinger, C., Bowman, J. D., Chupp, T. E., Covrig, S., Crawford, C. B., Dabaghyan, M., Dadras, J., Dawkins, M., Fox, W., Gericke, M. T., Gillis, R. C., Lauss, B., Leuschner, M. B., Lozowski, B., Mahurin, R., Mason, M., ... Yuan, V. (2011). Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission. Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 659(1), 579-586. https://doi.org/10.1016/j.nima.2011.07.051

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title = "Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission",

abstract = "The NPDGamma collaboration is performing a measurement of the very small parity-violating asymmetry in the angular distribution of the 2.2 MeV γ-rays from the capture of polarized cold neutrons on protons (A γ). The estimated size of Aγ is 5×10-8, and the measured asymmetry is proportional to the neutron polarization upon capture. Since the interaction of polarized neutrons with one of the two hydrogen molecular states (orthohydrogen) can lead to neutron spin-flip scattering, it is essential that the hydrogen in the target is mostly in the molecular state that will not depolarize the neutrons (≥99.8% parahydrogen). For that purpose, in the first stage of the NPDGamma experiment at the Los Alamos Neutron Science Center (LANSCE), we operated a 16-l liquid hydrogen target, which was filled in two different occasions. The parahydrogen fraction in the target was accurately determined in situ by relative neutron transmission measurements. The result of these measurements indicate that the fraction of parahydrogen in equilibrium was 0.9998±0.0002 in the first data taking run and 0.9956±0.0002 in the second. We describe the parahydrogen monitor system, relevant aspects of the hydrogen target, and the procedure to determine the fraction of parahydrogen in the target. Also assuming thermal equilibrium of the target, we extract the scattering cross-section for neutrons on parahydrogen.",

keywords = "Hadronic weak interaction, Liquid hydrogen, Neutron capture, Neutron polarization, Neutron scattering, Orthohydrogen, Parahydrogen, Parity violation",

author = "L. Barr{\'o}n-Palos and R. Alarcon and S. Balascuta and C. Blessinger and Bowman, {J. D.} and Chupp, {T. E.} and S. Covrig and Crawford, {C. B.} and M. Dabaghyan and J. Dadras and M. Dawkins and W. Fox and Gericke, {M. T.} and Gillis, {R. C.} and B. Lauss and Leuschner, {M. B.} and B. Lozowski and R. Mahurin and M. Mason and J. Mei and H. Nann and Penttil{\"a}, {S. I.} and Ramsay, {W. D.} and A. Salas-Bacci and S. Santra and Seo, {P. N.} and M. Sharma and T. Smith and Snow, {W. M.} and Wilburn, {W. S.} and V. Yuan",

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Barrón-Palos, L, Alarcon, R, Balascuta, S, Blessinger, C, Bowman, JD, Chupp, TE, Covrig, S, Crawford, CB, Dabaghyan, M, Dadras, J, Dawkins, M, Fox, W, Gericke, MT, Gillis, RC, Lauss, B, Leuschner, MB, Lozowski, B, Mahurin, R, Mason, M, Mei, J, Nann, H, Penttilä, SI, Ramsay, WD, Salas-Bacci, A, Santra, S, Seo, PN, Sharma, M, Smith, T, Snow, WM, Wilburn, WS & Yuan, V 2011, 'Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission', Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, vol. 659, no. 1, pp. 579-586. https://doi.org/10.1016/j.nima.2011.07.051

Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission. / Barrón-Palos, L.; Alarcon, R.; Balascuta, S. et al.
In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 659, No. 1, 11.12.2011, p. 579-586.

Research output: Contribution to journal › Article › peer-review

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T1 - Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission

AU - Barrón-Palos, L.

AU - Alarcon, R.

AU - Balascuta, S.

AU - Blessinger, C.

AU - Bowman, J. D.

AU - Chupp, T. E.

AU - Covrig, S.

AU - Crawford, C. B.

AU - Dabaghyan, M.

AU - Dadras, J.

AU - Dawkins, M.

AU - Fox, W.

AU - Gericke, M. T.

AU - Gillis, R. C.

AU - Lauss, B.

AU - Leuschner, M. B.

AU - Lozowski, B.

AU - Mahurin, R.

AU - Mason, M.

AU - Mei, J.

AU - Nann, H.

AU - Penttilä, S. I.

AU - Ramsay, W. D.

AU - Salas-Bacci, A.

AU - Santra, S.

AU - Seo, P. N.

AU - Sharma, M.

AU - Smith, T.

AU - Snow, W. M.

AU - Wilburn, W. S.

AU - Yuan, V.

PY - 2011/12/11

Y1 - 2011/12/11

N2 - The NPDGamma collaboration is performing a measurement of the very small parity-violating asymmetry in the angular distribution of the 2.2 MeV γ-rays from the capture of polarized cold neutrons on protons (A γ). The estimated size of Aγ is 5×10-8, and the measured asymmetry is proportional to the neutron polarization upon capture. Since the interaction of polarized neutrons with one of the two hydrogen molecular states (orthohydrogen) can lead to neutron spin-flip scattering, it is essential that the hydrogen in the target is mostly in the molecular state that will not depolarize the neutrons (≥99.8% parahydrogen). For that purpose, in the first stage of the NPDGamma experiment at the Los Alamos Neutron Science Center (LANSCE), we operated a 16-l liquid hydrogen target, which was filled in two different occasions. The parahydrogen fraction in the target was accurately determined in situ by relative neutron transmission measurements. The result of these measurements indicate that the fraction of parahydrogen in equilibrium was 0.9998±0.0002 in the first data taking run and 0.9956±0.0002 in the second. We describe the parahydrogen monitor system, relevant aspects of the hydrogen target, and the procedure to determine the fraction of parahydrogen in the target. Also assuming thermal equilibrium of the target, we extract the scattering cross-section for neutrons on parahydrogen.

AB - The NPDGamma collaboration is performing a measurement of the very small parity-violating asymmetry in the angular distribution of the 2.2 MeV γ-rays from the capture of polarized cold neutrons on protons (A γ). The estimated size of Aγ is 5×10-8, and the measured asymmetry is proportional to the neutron polarization upon capture. Since the interaction of polarized neutrons with one of the two hydrogen molecular states (orthohydrogen) can lead to neutron spin-flip scattering, it is essential that the hydrogen in the target is mostly in the molecular state that will not depolarize the neutrons (≥99.8% parahydrogen). For that purpose, in the first stage of the NPDGamma experiment at the Los Alamos Neutron Science Center (LANSCE), we operated a 16-l liquid hydrogen target, which was filled in two different occasions. The parahydrogen fraction in the target was accurately determined in situ by relative neutron transmission measurements. The result of these measurements indicate that the fraction of parahydrogen in equilibrium was 0.9998±0.0002 in the first data taking run and 0.9956±0.0002 in the second. We describe the parahydrogen monitor system, relevant aspects of the hydrogen target, and the procedure to determine the fraction of parahydrogen in the target. Also assuming thermal equilibrium of the target, we extract the scattering cross-section for neutrons on parahydrogen.

KW - Hadronic weak interaction

KW - Liquid hydrogen

KW - Neutron capture

KW - Neutron polarization

KW - Neutron scattering

KW - Orthohydrogen

KW - Parahydrogen

KW - Parity violation

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JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Barrón-Palos L, Alarcon R, Balascuta S, Blessinger C, Bowman JD, Chupp TE et al. Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission. Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2011 Dec 11;659(1):579-586. doi: 10.1016/j.nima.2011.07.051

Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission

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Keywords

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