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

L. Barrón-Palos, Ricardo 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

Research output: Contribution to journalArticle

7 Citations (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)579-586
Number of pages8
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume659
Issue number1
DOIs
StatePublished - Dec 11 2011

Fingerprint

liquid hydrogen
thermal neutrons
Neutrons
neutrons
Hydrogen
Liquids
energy
hydrogen
asymmetry
Scattering
cold neutrons
Angular distribution
scattering cross sections
monitors
rays
parity
angular distribution
Protons
Polarization
protons

Keywords

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

ASJC Scopus subject areas

  • Instrumentation
  • Nuclear and High Energy Physics

Cite this

Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission. / Barrón-Palos, L.; Alarcon, Ricardo; 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.; Mei, J.; Nann, H.; Penttilä, S. I.; Ramsay, W. D.; Salas-Bacci, A.; Santra, S.; Seo, P. N.; Sharma, M.; Smith, T.; Snow, W. M.; Wilburn, W. S.; Yuan, V.

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 journalArticle

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
Barrón-Palos, L. ; Alarcon, Ricardo ; 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. ; Mei, J. ; Nann, H. ; Penttilä, S. I. ; Ramsay, W. D. ; Salas-Bacci, A. ; Santra, S. ; Seo, P. N. ; Sharma, M. ; Smith, T. ; Snow, W. M. ; Wilburn, W. S. ; Yuan, V. / Determination of the parahydrogen fraction in a liquid hydrogen target using energy-dependent slow neutron transmission. In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2011 ; Vol. 659, No. 1. pp. 579-586.
@article{fa5b645621014d52b2e1a0052d29b35d,
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 Ricardo 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",
year = "2011",
month = "12",
day = "11",
doi = "10.1016/j.nima.2011.07.051",
language = "English (US)",
volume = "659",
pages = "579--586",
journal = "Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment",
issn = "0168-9002",
publisher = "Elsevier",
number = "1",

}

TY - JOUR

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

AU - Barrón-Palos, L.

AU - Alarcon, Ricardo

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

UR - http://www.scopus.com/inward/record.url?scp=80455173917&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=80455173917&partnerID=8YFLogxK

U2 - 10.1016/j.nima.2011.07.051

DO - 10.1016/j.nima.2011.07.051

M3 - Article

AN - SCOPUS:80455173917

VL - 659

SP - 579

EP - 586

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

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

SN - 0168-9002

IS - 1

ER -