Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission
Por:
Grammer K.B., Alarcon R., Barrón-Palos L., Blyth D., Bowman J.D., Calarco J., Crawford C., Craycraft K., Evans D., Fomin N., Fry J., Gericke M., Gillis R.C., Greene G.L., Hamblen J., Hayes C., Kucuker S., Mahurin R., Maldonado-Velázquez M., Martin E., McCrea M., Mueller P.E., Musgrave M., Nann H., Penttilä S.I., Snow W.M., Tang Z., Wilburn W.S.
Publicada:
8 may 2015
Resumen:
Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. Unfortunately, the pair correlation function g(r) inferred from neutron scattering measurements of the differential cross section dsdO from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43 and 16.1 meV on liquid hydrogen at 15.6 K (which is dominated by the parahydrogen component) using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1 meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra nonequilibrium component of orthohydrogen. Liquid parahydrogen is also a widely used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. We describe our measurements and compare them with previous work. © 2015 American Physical Society.
Filiaciones:
Grammer K.B.:
University of Tennessee, Knoxville, TN 37996, United States
Alarcon R.:
Arizona State University, Tempe, AZ 85281, United States
Barrón-Palos L.:
Univ Nacl Autonoma Mexico, Inst Fis, Mexico City 01000, DF, Mexico
Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, México D. F., 01000, Mexico
Blyth D.:
Arizona State University, Tempe, AZ 85281, United States
Bowman J.D.:
Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
Calarco J.:
University of New Hampshire, Durham, NH 03824, United States
Crawford C.:
University of Kentucky, Lexington, KY 40506, United States
Craycraft K.:
University of Tennessee, Knoxville, TN 37996, United States
University of Kentucky, Lexington, KY 40506, United States
Evans D.:
University of Virginia, Charlottesville, VA 22904, United States
Fomin N.:
University of Tennessee, Knoxville, TN 37996, United States
Fry J.:
Indiana University, Bloomington, IN 47405, United States
Gericke M.:
University of Manitoba, Winnipeg, MB R3T 2N2, Canada
Gillis R.C.:
Indiana University, Bloomington, IN 47405, United States
Greene G.L.:
University of Tennessee, Knoxville, TN 37996, United States
Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
Hamblen J.:
University of Tennessee-Chattanooga, Chattanooga, TN 37403, United States
Hayes C.:
University of Tennessee, Knoxville, TN 37996, United States
Kucuker S.:
University of Tennessee, Knoxville, TN 37996, United States
Mahurin R.:
University of Manitoba, Winnipeg, MB R3T 2N2, Canada
Middle Tennessee State University, Murfreesboro, TN 37130, United States
Maldonado-Velázquez M.:
Univ Nacl Autonoma Mexico, Inst Fis, Mexico City 01000, DF, Mexico
Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, México D. F., 01000, Mexico
Martin E.:
University of Kentucky, Lexington, KY 40506, United States
McCrea M.:
University of Manitoba, Winnipeg, MB R3T 2N2, Canada
Mueller P.E.:
Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
Musgrave M.:
University of Tennessee, Knoxville, TN 37996, United States
Nann H.:
Indiana University, Bloomington, IN 47405, United States
Penttilä S.I.:
Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
Snow W.M.:
Indiana University, Bloomington, IN 47405, United States
Tang Z.:
Indiana University, Bloomington, IN 47405, United States
Los Alamos National Laboratory, Los Alamos, NM, United States
Wilburn W.S.:
Los Alamos National Laboratory, Los Alamos, NM, United States
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