Robust measurement of para-ortho H<sub>2</sub> ratios to characterise the ISIS hydrogen moderators

We present an experimental study to determine the para-hydrogen concentration in the hydrogen moderators at the ISIS pulsed neutron and muon source. The experimental characterisation is based on neutron transmission experiments performed on the VESUVIO spectrometer, and thermal conductivity measurements using the TOSCA para-hydrogen rig. A reliable estimation of the level of para-hydrogen concentration in the hydrogen moderators is of crucial importance in the framework of a current project to completely refurbish the first target station at ISIS. Moreover, we report a new measurement of the total neutron cross section for normal hydrogen at 15 K on the broad energy range 3 meV-10 eV suggesting a revision of the most recent nuclear libraries for incident neutron energies lower than 10 meV. Finally, we characterise systematic errors affecting the para-hydrogen level estimation due to conversion from para to ortho hydrogen, as a function of the time a batch of gas spends in every component of our gas panel and apparatus.

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“…A schematic diagram of the experimental apparatus [19] is shown in Fig. 2, and it is discussed in detail in this section.…”

Section: Methodsmentioning

confidence: 99%

Measurement of the para-hydrogen concentration in the ISIS moderators using neutron transmission and thermal conductivity

Romanelli

Rudić

Zanetti

et al. 2018

Nuclear Instruments and Methods in Physics Research Section A:

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“…Traditionally, the core technique employed at VESUVIO has been neutron Compton scattering (NCS) [19][20][21][22][23]. Due to the recent upgrades in the instrumentation, sample environment, and software [19,20,24,[26][27][28][29][30], VESUVIO has become a very versatile tool, enabling concurrent measurements using techniques such as NCS, energy-dependent neutron transmission [29,[31][32][33][34][35][36][37][38][39], neutron diffraction [30,40,41], and gamma spectroscopy [24,[42][43][44][45]. The aforementioned techniques, especially when applied concurrently, enable the investigation of a plethora of physical and chemical properties of condensed matter systems.…”

Section: Introductionmentioning

confidence: 99%

Glass Transition in Rice Pasta as Observed by Combined Neutron Scattering and Time-Domain NMR

2021

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Experimental protocols aiming at the characterisation of glass transition often suffer from ambiguity. The ambition of the present study is to describe the glass transition in a complex, micro heterogeneous system, the dry rice pasta, in a most unambiguous manner, minimising the influence of technique-specific bias. To this end, we apply an unprecedented combination of experimental techniques. Apart from the usually used NMR and DSC, we employ, in a concurrent manner, neutron transmission, diffraction, and Compton scattering. This enables us to investigate the glass transition over a range of spatio-temporal scales that stretches over seven orders of magnitude. The results obtained by neutron diffraction and DSC reveal that dry rice pasta is almost entirely amorphous. Moreover, the glass transition is evidenced by neutron transmission and diffraction data and manifested as a significant decrease of the average sample number density in the temperature range between 40 and 60 °C. At the microscopic level, our NMR, neutron transmission and Compton scattering results provide evidence of changes in the secondary structure of the starch within the dry rice pasta accompanying the glass transition, whereby the long-range order provided by the polymer structure within the starch present in the dry rice pasta is partially lost.

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Robust measurement of para-ortho H₂ ratios to characterise the ISIS hydrogen moderators

Cited by 2 publications

References 8 publications

Measurement of the para-hydrogen concentration in the ISIS moderators using neutron transmission and thermal conductivity

Measurement of the para-hydrogen concentration in the ISIS moderators using neutron transmission and thermal conductivity

Glass Transition in Rice Pasta as Observed by Combined Neutron Scattering and Time-Domain NMR

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Robust measurement of para-ortho H2 ratios to characterise the ISIS hydrogen moderators

Cited by 2 publications

References 8 publications

Measurement of the para-hydrogen concentration in the ISIS moderators using neutron transmission and thermal conductivity

Measurement of the para-hydrogen concentration in the ISIS moderators using neutron transmission and thermal conductivity

Glass Transition in Rice Pasta as Observed by Combined Neutron Scattering and Time-Domain NMR

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Robust measurement of para-ortho H₂ ratios to characterise the ISIS hydrogen moderators