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Nausicaa

The Computing for Science (CS) group supports ILL scientists, students and visitors in a number of activities including data analysis, instrument simulation and sample simulation.

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Nausicaa

Nausicaa collaboration

The NAUSICAA (Neutron AUgmented Sαβ In Cross sections Alternative Assessment) project is a collaborative research study including the ILL, the IRSN, the CEA, the TUM, the ESS, the University of Florence and the Ecole Polytechnique de Montréal. This project started mid-2014, and aims at improving the accuracy of the international neutron cross section libraries for reactor physics by introducing direct measurements. The most direct consequence of this project will be the tremendous improvement heavy water reactors and cold sources modelling. This project is organized under the auspices of the OECD/NEA, which will bring us a strong support, and in collaboration with the IAEA.

One caveat of the neutron cross section libraries is indeed the evaluation process of thermal neutron cross sections in liquids, especially in hydrogenated liquids in which inaccurate approximations are employed. This problem could be solved by the direct use of measured structure factors S(Q,ω), where Q is the neutron momentum transfer and ω is the neutron energy transfer. Until now all evaluations related to thermal neutron were based upon experiments performed with a momentum transfer Q=0, like IR or Raman. The extension on the whole Q domain is carried out by approximate laws which become clearly wrong in the case of liquids like water. This means that measurements of a real S(Q,ω) enable to get rid of the extension laws approximations and thus to significantly enhance the accuracy of the cross sections.

The first step of the study is now completed. A paper has been submitted for light and heavy water and a detailed report has been published in the framework of the CRISP project. We have demonstrated the feasibility and the reliability of this method. Two additional steps are foreseen in the next future and will be carried out in parallel. One is the acquisition and refinement of accurate data on light and heavy water in several conditions of temperature and pressure, from ambient to supercritical conditions. The other is the study of cryogenic liquids like liquid hydrogen and deuterium, which will require several years to carry out the measurements in the best conditions.

Nausicaa achievements

Symmetrised dynamic structure factor S(q, ω) of light (left) and heavy (right) water around 300K, combining molecular dynamics and experimental data sets. The S(q, ω) contour plot is shown in log 10 scale. (c) E. Farhi JNST 2014.

We have performed neutron scattering experiments on water (light and heavy) as a complement to molecular dynamics simulations.

In addition, work has been done with l-D2 and l-H2, in the CRISP collaboration.

 

 

Experimental and molecular dynamics data from [1]. The density of states (frequency spectrum) must be normalised to 1.
Data setD2OH2O
vDOS from NAMD

[vDOS D2O NAMD txt]

[vDOS H2O NAMD txt]

S(q,w) from NAMD (separate coherent and incoherent)

[Sqw D2O NAMD]

[Sqw H2O NAMD]

gDOS from ILL experiments (merging all temperatures). This is a very approximate result.

[ D2O gDOS ]

[ H2O gDOS ]

Experimental data (2010) experiment 1-10-9

Whenever using any of this data, you should cite E. Farhi,et al,  J.Nucl. Sci. Tech. 52 (2015) 844.

Data is in HDF format that you can open with  iFit and LAMP (or HDFView).

IN4 was operated at lambda=1.1 Angs, and IN5 was operated at 2 Angs. P=1atm.

250K (ice) [IN4]

295K [IN5]

296K [IN4]

325K [IN4]

empty cell [IN4]

empty cell [IN5]

285K [IN5]

290K [IN5]

294K [IN4]

300K [IN5]

302K [IN4]

311K [IN4]

323K [IN4]

empty cell [IN4]

empty cell [IN5]

 

 

Experimental data (2015) experiment 1-04-90

This data is not yet available for public use (not published).

T=300-540K

P=1-600b

T=300-540K

P=1-600b
S(q,w) from GROMACS coherent contribution only
S(q,w) from ILL experiments (total) (merging all temperatures)

[Sqw D2O exp]

[Sqw H2O exp]

 

References:

[1] E. Farhi, G. Ferran, W. Haeck, E. Pellegrini and Y. Calzavara, "Light and heavy water dynamic structure factor for neutron transport codes", J.Nucl. Sci. Tech. 52 (2015) 844 ; DOI: 10.1080/00223131.2014.98400

[2] McStas and ACE(MCNP) data files. (JNST 2014 above). DISCLAIMER: not fully qualified. We hope to improve gradually the reliability of this data, and extend its range in temperature, pressure, pH, ...

[3] E. Guarini, "Moderator neutron cross-section data. The neutron cross section of the hydrogen liquids: substantial improvements and perspectives" CRISP WP11 T2 report (July 2014)

[4] E. Guarini, M. Neumann, U. Bafile, M. Celli, D. Colognesi, E. Farhi, and Y. Calzavara, "Velocity autocorrelation in liquid parahydrogen by quantum simulations for direct parameter-free computations of neutron cross sections", Phys. Rev. B 92 (2015) 104303. DOI: 10.1103/PhysRevB.92.104303

[5] ILL experiment 1-04-90 (2015): FARHI Emmanuel; CALZAVARA Yoann; FERRAN Ghislain; GUARINI Eleonora; HAECK Wim;INIDJEL Gaetan; JAISWAL VAIBHAV; NOGUERE Gilles; OLLIVIER Jacques; ROLS Stephane and SCOTTA Juan Pablo. (2015). Measurement of light and heavy water thermal cross sections for neutron transport codes, up to 350C and 150 bar, Institut Laue-Langevin (ILL) doi:10.5291/ILL-DATA.1-04-90.

[6] ILL experiment 1-10-9 (2010).

Nausicaa meeting June 2015

The 2nd Nausicaa meeting took place at the ILL on June 29-30th 2015. We discussed recent progress on the evaluation of neutron scattering cross section estimates from S(a,b) and more specifically of measurements required, and benefits from molecular dynamics simulation using NAMD, GROMACS and POLARIS.

 

You can find below a list of documents to download, including the Agenda and some of the presentations given.

Nausicaa agenda and presentations (June 2015 )

Our tools

In order to achieve the goals of the Nausicaa project, we make use of:

  • Neutron scattering time-of-flight spectroscopy, to acquire a portion of the S(q,w) dynamic structure factor. At the ILL, we use IN4, IN5, IN6 and BRISP
  • Molecular dynamics: to simulate atom/molecule trajectories. We use: NAMD, VASP.
  • Molecular Dynamics data treatment: to transform the MD trajectories into the S(q,w) dynamic structure factor by double Fourier transform. We use: nMoldyn
  • Experimental data browser: to import the spectrometer data files. We use: LAMP.
  • Data merge: to gather experimental data sets from different instruments, and molecular dynamics. We use: iFit.
  • Virtual experiment: to simulate the experimental artefacts (multiple scattering, absorption...). We use: McStas.
  • Reactor modeling neutron transport code. We use: MCNP.

 

 

Nausicaa Partners

The Nausicaa consortium is formed of the following partners

 

In addition, ANL, AECL, IAEA, NEA/OECD and Areva take part as observers.

 

The Bariloche group also contributes actively in this area. See their extensive results.

 

At the ILL, the project is a collaboration between the Computing for Science group, and the Bureau Projets et Calculs (BPC).