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

Romanelli, Giovanni; Rudić, Svemir; Zanetti, Matteo; Fernandez-Alonso, Félix; Gorini, G.; Krzystyniak, M.; Škoro, G.

doi:10.1016/j.nima.2018.01.039

Cited by 15 publications

(26 citation statements)

References 36 publications

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“…Similar plans are being implemented both for VESPA design and TOSCA secondary spectrometer upgrade, characterizing the neutronic response of the different materials and components that will be used in the final instruments, and validating the models used to design them. For instance, some of the materials to be used in the instruments are being tested, by studying their neutron transmission properties, as recently demonstrated on VESUVIO [20].…”

Section: Discussionmentioning

confidence: 99%

Neutronic developments on TOSCA and VESPA: Progress to date

Zanetti

Bellissima

Rosso

et al. 2019

Physica B: Condensed Matter

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A B S T R A C TWe report recent developments regarding the TOSCA (ISIS, UK) and VESPA (ESS, Sweden) neutron broadband chemical spectrometers, both joint ventures between CNR (IT) and ISIS (UK). TOSCA has seen the first major upgrade since it first became operational over fifteen years ago. The new design of the primary spectrometer, which exploits a state-of-the-art, high-m neutron guide and associated chopper system, is boosting the useful neutron flux by over an order of magnitude. Feasibility studies for an upgrade of the secondary spectrometer have been performed, outlining an additional order-of-magnitude gain in performance. In the case of VESPA, the novel characteristics and challenges arising from a long-pulse spallation source such as ESS are part of the drivers of the instrument design. For both the primary and secondary spectrometers, a detailed analysis of expected performance, supported by both simulations and analytical models, is being carried out, also capitalizing from experience on TOSCA. Indeed, for instrument design and optimization, extensive neutron-transport simulations and baseline studies of neutronic response have become a must, along with extensive benchmarking against much-needed experimental data. All these combined efforts represent the first opportunity to benchmark a broadband, high-resolution chemical spectrometer in terms of measured vs. simulated response. High-resolution broadband chemical spectrometersInelastic Neutron Scattering (INS) as a vibrational spectroscopy technique [1] is widely used across chemistry, materials science, biology, and beyond. The workhorses for this kind of studies can be called "High-resolution Broadband Chemical Spectrometers". Here, we focus on time-of-flight instruments at pulsed spallation sources in socalled indirect geometry, and whereby final-energy selection is attained with a crystal after scattering by the sample. With them, good-quality spectra (i.e. high count rate and resolution) can be obtained with reasonably small quantities of specimen and easy operation. This type of instruments is generally divided into a Primary Spectrometer (PS), dedicated to neutron delivery from a moderator to the sample, and a Secondary Spectrometer (SS) which processes neutrons scattered from the sample and delivers them to the detectors.In the PS the polychromatic beam, coming from the moderator, is generally worked on by a chopper system (i.e. shaping or cleaning it) and transported onto the sample by a neutron delivery device (e.g. an evacuated tube or a super-mirror guide). The SS is arranged in such a way that the final energy of neutrons that can be detected after scattering by the sample is fixed. This is achieved via the use of an analyser crystal, typically HOPG (Highly Oriented Pyrolytic Graphite), which selects the neutrons through Bragg scattering. In order to eliminate higher-order crystal reflections, a low-pass energy filter is used. The filter is typically made with a thick block of beryllium, selecting the bandwidth by exploiting the Bragg cut...

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Section: Discussionmentioning

confidence: 99%

Neutronic developments on TOSCA and VESPA: Progress to date

Zanetti

Bellissima

Rosso

et al. 2019

Physica B: Condensed Matter

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“…The empty containers were then separately measured at the same temperatures as the samples. Both sample and empty-container neutron transmissions were measured as a function of the incident neutron energies, normalising to the transmission spectrum of the empty instrument, a protocol routinely applied in broadband transmission experiments on VESUVIO [30][31][32][33][34]. The mass of the isopropanol sample was 0.89 g. Given the total bound scattering cross-section values of H, C, and O and the sample stoichiometry, C 3 H 8 O, the mass of 0.89 g corresponded to the sample transmission for epithermal neutrons (above the incident neutron energy of 1 eV) at the level of 0.86.…”

Section: Methodsmentioning

confidence: 99%

Neutron Compton Scattering: from proton momentum distribution to muonium hyperfine coupling constant in the isopropyl radical

2019

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We establish a fast and reliable benchmarking protocol for predictions of Muon Spin Resonance observables. To this end, we apply neutron Compton scattering (NCS) to study the nuclear momentum distributions of the proton and deuteron in the condensed phase of the isopropyl and d-isopropyl alcohols. By subtracting the time-of-flight NCS spectra of both compounds we demonstrate that the proton momentum distribution in the OH group of isopropanol and the deuteron momentum distribution in the OD group in d-isopropyl can be studied selectively. The siteselective application of the NCS method enables the calculation of the magnitude of the frequency isotope effect for the proton in OH along the hydrogen bond direction. By comparing the magnitude of the frequency isotope effect with values predicted for simple model potentials we are able to perform the appraisal of the degree of anharmonicity of the OH proton environment. Assuming that the effective potential felt by the OH proton along the hydrogen-bond direction can be satisfactorily described by the Morse potential, we are able to calculate its dissociation constant D and decay constant a. Finally, assuming that the same Morse potential describes the local binding of Muonium in the mioniated isopropyl radical, we are able to predict its width of momentum and position distributions and the kinetic and zero-point energy. Based on these results, we are able to provide a conservative bound for the magnitude of the isotope effect on the muonium hyperfine interaction without resorting to a complicated and computationally expensive methodology based on the application of path integrals.

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“…Furthermore, the capabilities available with neutron transmission can be increased by including a monitor with both spatial-and energy-resolution, therefore making neutron imaging available, with possible applications to the characterisation of catalytic processes as in the case of [12]. Such a detector would serve as a monitor for a more robust correction of DINS data, and as a diagnostic tool.…”

Section: Outlook and Ways Forwardmentioning

confidence: 99%

“…Looking at the proceedings of the VI (2014) [1] and VII (2017) international workshops on eV neutron spectroscopy [2], one can notice how the use of Deep Inelastic Neutron Scattering (DINS) to characterise Nuclear Quantum Effects (NQEs) mostly on hydrogen dynamics [3] has lead to MAss-selective Neutron SpEctroscopy (MANSE), whereby the Nuclear Momentum Distributions (NMDs) of several elements in a given sample are accessed at the same time [4,5,6]. Furthermore, a number of recent investigations carried out on the VESUVIO spectrometer [7], the flagship instrument for eV neutron spectroscopy at the ISIS Facility [8], successfully combined DINS with concurrent Neutron Diffraction (ND) measurements [9,10], or employed broad-range Neutron Transmission (NT) [11,12]. Moreover, a novel trend of concurrent characterisation of condensed-matter systems by means of DINS, ND, and Neutron Resonance Capture Analysis (NRCA) is proving to be a potent strategy and thus is gaining momentum [13].…”

Section: Introductionmentioning

confidence: 99%

The road to a station for epithermal and thermal neutron analysis

Romanelli

Krzystyniak

Festa

et al. 2018

J. Phys.: Conf. Ser.

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Abstract.Despite the large variety of research interests and themes motivating the current neutron research included in this collection, we have found common denominators characterising the manner in which the chosen research methodology tries to tackle the envisaged scientific questions. This article attempts to characterise those trends in current research with the aim of identifying the main mid-to-long term opportunities faced by electron-Volt neutron spectroscopy. The main realisation from this exercise is that the scientific community seems eager to combine neutron-based techniques over a broad energy range. To this end, the most natural choice seems to be to resort to neutron instruments where such capabilities are already present from the outset, with the most prominent example being the VESUVIO spectrometer at the ISIS pulsed neutron and muon source in the UK. However broad the operational basis of the existing neutron beamline infrastructure may be, progress, achievable only through further instrument upgrades, is the only way forward. The need to move forward is clearly seen within the community and is well documented by the research presented in this collection. This need for a substantial upgrade has crystallised in the form of a proposition to build a station rather than a conventional beamline, for Epithermal and Thermal Neutron Analysis station, hereafter ETNA.

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

Cited by 15 publications

References 36 publications

Neutronic developments on TOSCA and VESPA: Progress to date

Neutronic developments on TOSCA and VESPA: Progress to date

Neutron Compton Scattering: from proton momentum distribution to muonium hyperfine coupling constant in the isopropyl radical

The road to a station for epithermal and thermal neutron analysis

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