Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

被引：31

作者：

Grammer, K. B. ^{[1
]}

Alarcon, R. ^{[2
]}

Barron-Palos, L. ^{[3
]}

Blyth, D. ^{[2
]}

Bowman, J. D. ^{[4
]}

Calarco, J. ^{[5
]}

Crawford, C. ^{[6
]}

Craycraft, K. ^{[1
,6
]}

Evans, D. ^{[7
]}

Fomin, N. ^{[1
]}

Fry, J. ^{[8
]}

Gericke, M. ^{[9
]}

Gillis, R. C. ^{[8
]}

Greene, G. L. ^{[1
,4
]}

Hamblen, J. ^{[10
]}

Hayes, C. ^{[1
]}

Kucuker, S. ^{[1
]}

Mahurin, R. ^{[9
,11
]}

Maldonado-Velazquez, M. ^{[3
]}

Martin, E. ^{[6
]}

McCrea, M. ^{[9
]}

Mueller, P. E. ^{[4
]}

Musgrave, M. ^{[1
]}

Nann, H. ^{[8
]}

Penttilae, S. I. ^{[4
]}

Snow, W. M. ^{[8
]}

Tang, Z. ^{[8
,12
]}

Wilburn, W. S. ^{[12
]}

机构：

[1] Univ Tennessee, Knoxville, TN 37996 USA

[2] Arizona State Univ, Tempe, AZ 85281 USA

[3] Univ Nacl Autonoma Mexico, Inst Fis, Mexico City 01000, DF, Mexico

[4] Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA

[5] Univ New Hampshire, Durham, NH 03824 USA

[6] Univ Kentucky, Lexington, KY 40506 USA

[7] Univ Virginia, Charlottesville, VA 22904 USA

[8] Indiana Univ, Bloomington, IN 47405 USA

[9] Univ Manitoba, Winnipeg, MB R3T 2N2, Canada

[10] Univ Tennessee, Chattanooga, TN 37403 USA

[11] Middle Tennessee State Univ, Murfreesboro, TN 37130 USA

[12] Los Alamos Natl Lab, Los Alamos, NM USA

来源：

PHYSICAL REVIEW B | 2015年 / 91卷 / 18期

基金：

美国国家科学基金会;

关键词：

INSULATOR-METAL TRANSITION; FLUID MOLECULAR-HYDROGEN; GPA; 1.4; MBAR; MICROSCOPIC STRUCTURE; SOLID HYDROGEN; MODERATOR; STATE; DYNAMICS; HELIUM; TARGET;

D O I：

10.1103/PhysRevB.91.180301

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

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 d sigma/d Omega 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.

引用

页数：6

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