Sylvain Desert

Toward a new lower limit for the minimum scattering vector on the very small angle neutron scattering spectrometer at Laboratoire Leon Brillouin

The main characteristics of the very small angle neutron scattering spectrometer (VSANS) under construction at the Laboratoire Leon Brillouin are a multibeam pinhole collimator converging onto an image plate detector. By combining tiny collimation (diaphragms of around I or 2 mm in diameter) with the small pixel size of the detector (0.15 x 0.15 mm), very high resolution measurements can be achieved. The resolution function of the instrument contains a contribution from gravity, which is reduced by the intermediate masks of the collimator. Owing to the relatively short length of the VSANS instrument (around 14 m), this effect remains weak, in good agreement with the predictions. With a prototype multibeam collimator, an incident wavelength of 0.9 nm and the detector located at 6 m from the sample, it is possible to access q values as low as 4 x 10(-3) nm(-1) with very high q resolution. Promising preliminary experiments with high q resolution are reported, which open up new fields to the SANS technique.

The new very-small-angle neutron scattering spectrometer at Laboratoire Léon Brillouin

The design and characteristics of the new very-small-angle neutron scattering spectrometer under construction at the Laboratoire Leon Brillouin are described. Its goal is to extend the range of scattering-vector magnitudes towards 2 × 10−4 A−1. The unique feature of this new spectrometer is a high-resolution two-dimensional image-plate detector sensitive to neutrons. The wavelength selection is achieved by a double-reflection supermirror monochromator and the collimator uses a novel multibeam design.

Focusing neutrons with a combination of parabolic and elliptical supermirrors

Cold-neutron focusing is a challenge with regard to improving the flux at the sample, decreasing measurement time and/or gaining statistical reliability. Several techniques are used for neutron focusing, such as simple or multi-beam collimation, refractive or magnetic lenses, and focusing mirrors. In this work, a new device for focusing neutrons using a combination of a parabolic supermirror, an asymmetric slit system and an elliptical supermirror is presented. The aim of this focusing system is to improve the neutron flux at the sample compared to other techniques without either achromatism or absorption. The performance of the device obtained by simulations and measurements with a prototype on a small-angle neutron scattering setup shows a flux gain of four at the sample position and an intensity gain higher than 100 when the sample size can be increased compared to classical setups. Finally the applications for neutron instruments are commented on.

On the design and experimental realization of a multislit-based very small angle neutron scattering instrument at the European Spallation Source

This article reports the design of a versatile multislit-based very small angle neutron scattering (VSANS) instrument working either as a dedicated instrument or as an add-on for any small-angle neutron scattering machine like the proposed SANS instrument, SKADI, at the future European Spallation Source. The use of multiple slits as a VSANS collimator for the time-of-flight techniques has been validated using McStas simulations. Various instrument configurations to achieve different minimum wavevector transfers in scattering experiments are proposed. The flexibility of the multislit VSANS instrument concept is demonstrated by showing the possibility of instrument length scaling for the first time, allowing access to varying minimum wavevector transfers with the same multislit setup. These options can provide smooth access to minimum wavevector transfers lower than ∼4 × 10−5 A−1 and an overlapping of wavevector coverage with normal SANS mode, e.g. with the SKADI wavevector range of 10−3–1.1 A−1. Such an angularly well defined and intense neutron beam will allow faster SANS studies of objects larger than 1 µm. Calculations have also been carried out for a radial collimator as an alternative to the multislit collimator setup. This extends the SANS Q range by an order of magnitude to 1 × 10−4 A−1 with much simpler alignment. The multislit idea has been realized experimentally by building a prototype at Laboratoire Leon Brillouin, Saclay, with cross-talk-free geometry. Feasibility studies were carried out by making VSANS measurements with single- and multislit collimators, and the results are compared with multiple-pinhole geometry using classical SANS analysis tools.

A double-supermirror monochromator for neutron instrumentation at Laboratoire Léon Brillouin

The design and characteristics of a double-supermirror monochromator for neutron instrumentation at the Laboratoire Leon Brillouin are described. The aim of this monochromator is to reduce the intense γ radiation produced by conventional velocity selectors and to avoid a direct view of the guide while keeping a comparable neutron transmission (70%). The monochromator offers a continuous choice of wavelength selection in the range 0.5–2 nm.

LLB Instrumentation Program CAP 2015

The main objectives of the CAP2015 instrumental program are to provide a modern set of neutron instruments to the French and international neutron scattering community and to prepare and train a new generation of neutron users and scientists, in view of the future European spallation source. In 2005, after more than a decade of successful operations of the first-generation instruments at Orphée, Laboratoire Léon-Brillouin (LLB) started its first instrument refurbishment program, CAP2010. The program was established in January 2005 on the basis of internal instrumentation project proposals, which emerged after a comprehensive analysis of performance of existing instruments at LLB.

High intensity multi beam design of SANS instrument for Dhruva reactor

A new and versatile design of Small Angle Neutron Scattering (SANS) instrument based on utilization of multi-beam is presented. The multi-pinholes and multi-slits as SANS collimator for medium flux Dhruva rearctor have been proposed and their designs have been validated using McStas simulations. Various instrument configurations to achieve different minimum wave vector transfers in scattering experiments are envisioned. These options enable smooth access to minimum wave vector transfers as low as ~ 6×10−4 A−1 with a significant improvement in neutron intensity, allowing faster measurements. Such angularly well defined and intense neutron beam will allow faster SANS studies of agglomerates larger than few tens of nm.