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Title: Ortho- and para-hydrogen in neutron thermalization

The large difference in neutron scattering cross-section at low neutron energies between ortho- and para-hydrogen was recognized early on. In view of this difference (more than an order of magnitude), one might legitimately ask whether the ortho/para ratio has a significant effect on the neutron thermalization properties of a cold hydrogen moderator. Several experiments performed in the 60`s and early 70`s with a variety of source and (liquid hydrogen) moderator configurations attempted to investigate this. The results tend to show that the ortho/para ratio does indeed have an effect on the energy spectrum of the neutron beam produced. Unfortunately, the results are not always consistent with each other and much unknown territory remains to be explored. The problem has been approached from a computational standpoint, but these isolated efforts are far from having examined the ortho/para-hydrogen problem in neutron moderation in all its complexity. Because of space limitations, the authors cannot cover, even briefly, all the aspects of the ortho/para question here. This paper will summarize experiments meant to investigate the effect of the ortho/para ratio on the neutron energy spectrum produced by liquid hydrogen moderators.
Authors:
;
Publication Date:
OSTI Identifier:
674718
Report Number(s):
LA-UR--98-1022; CONF-9709132--; IWCMPNS--1997
ON: DE98006321; TRN: 99:000540
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: International Workshop on Cold Moderators for Pulsed Neutron Sources, Argonne, IL (United States), 29 Sep - 2 Oct 1997; Other Information: PBD: [1998]
Research Org:
Los Alamos National Lab., Los Alamos, NM (United States). Manuel Lujan, Jr. Neutron Scattering Center,
Sponsoring Org:
USDOE Office of Energy Research, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 07 ISOTOPE AND RADIATION SOURCE TECHNOLOGY; THERMALIZATION; MODERATORS; ACCELERATOR FACILITIES; NEUTRON SOURCES; HYDROGEN; ENERGY SPECTRA; SPIN