Abstract
The intense radiation environment of a neutron moderator provides a mechanism for significant up-conversion of parahydrogen to orthohydrogen inside the moderator, as well as intrinsically catalyzing relaxation of orthohydrogen to parahydrogen. It is plausible that the steady-state orthohydrogen fraction of a moderator in a radiation environment such as at the Spallation Neutron Source (SNS) or the European Spallation Source (ESS) is as high as 30 % without supplemental catalysis. Direct measurement of the orthohydrogen fraction in the liquid hydrogen flow itself is essential to predict and monitor moderator performance, especially for thick or flat moderator concepts such as the ones that have been proposed for the ESS and for upgrades to the SNS. Raman spectroscopy provides a well-known method for directly measuring the hydrogen make-up in an unambiguous way. We describe our tests of Raman spectroscopy for application to the measurement of the orthohydrogen fraction of the hydrogen moderators at SNS and at the ESS. As part of this work, we have additionally developed a sample holder that has been used to perform simultaneous Raman and neutron vibrational spectroscopy on the VISION spectrometer at SNS. We discuss our plans to incorporate such a system as a diagnostic for liquid hydrogen moderators at SNS and at the ESS.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
