Neutron scattering studies of density fluctuations in liquid argon and neon

Applied Science

Neutron Larmor diffraction with double and single precession arm

A review is given of double and single arm Larmor diffraction. With the former a lattice-spacing resolution down to 10-6 can be obtained. The latter is a good high-resolution alternative if the sample or sample environment disturbs the magnetic field, e.g. ferromagnetic samples or applied magnetic fields. By choosing the tilt angle of the precession fields the optimum resolution can be set at a scattering angle at choice. The resolution for both single-crystal and polycrystalline samples is discussed in depth and is compared with conventional neutron-diffraction techniques.RST/Neutron and Positron Methods in MaterialsBedrijfsondersteunin

Larmor neutron diffraction with one precession arm

A new variant of Larmor neutron diffraction, applying only a single precession arm in the initial beam, is proposed. The single arm, together with the polarizer and analyser and possible rotators, are mounted in front of the sample. The great advantage with respect to the case with another precession arm in the reflected beam is that magnetic samples can now be investigated, because depolarization and the Larmor phase change of the beam polarization in the sample after the analyser is no longer of importance for diffraction analysis. The application has lower resolution than the double-arm precession geometry, but is still better than conventional diffraction instruments. The differences will be discussed.RST/Radiation, Science and TechnologyApplied Science

Coherence approach to neutron polarization propagation in instruments

The propagation of the mutual coherence function is a well known method to describe the effects of neutron’s propagation through scattering instruments. This method is extended with the description of the coherence matrix to account for neutron polarization effects and its propagation through an instrument. A propagation law for the coherence matrix and the condition under which it can be used is derived. A rigorous description of polarization analysis is given. The phase-object approximation to describe small angle neutron scattering is extended to incorporate scattering in magnetic materials. The developed theory is applied to spin echo small angle neutron scattering and the neutron depolarization technique.Radiation, Radionuclides and ReactorsApplied Science

Reflection mode XAFS at the Ti K-edge of lithium intercalated TiO2 electrodes

Applied Science

Retrieval of phase information in neutron reflectometry

Neutron reflectometry can determine unambiguously the chemical depth profile of a thin film if both phase and amplitude of the reflectance are known. The recovery of the phase information is achieved by adding to the unknown layered structure a known ferromagnetic layer. The ferromagnetic layer is magnetized by an external magnetic field in a direction lying in the plane of the layer and subsequently perpendicular to it. The neutrons are polarized either parallel or opposite to the magnetic field. In this way three measurements can be made, with different (and known) scattering-length densities of the ferromagnetic layer. The reflectivity obtained from each measurement can be represented by a circle in the (complex) reflectance plane. The intersections of these circles provide the reflectance

Hafnium - an optical hydrogen sensor spanning six orders in pressure

Hydrogen detection is essential for its implementation as an energy vector. So far, palladium is considered to be the most effective hydrogen sensing material. Here we show that palladium-capped hafnium thin films show a highly reproducible change in optical transmission in response to a hydrogen exposure ranging over six orders of magnitude in pressure. The optical signal is hysteresis-free within this range, which includes a transition between two structural phases. A temperature change results in a uniform shift of the optical signal. This, to our knowledge unique, feature facilitates the sensor calibration and suggests a constant hydrogenation enthalpy. In addition, it suggests an anomalously steep increase of the entropy with the hydrogen/metal ratio that cannot be explained on the basis of a classical solid solution model. The optical behaviour as a function of its hydrogen content makes hafnium well-suited for use as a hydrogen detection material.ChemE/Materials for Energy Conversion & StorageRST/Neutron and Positron Methods in Material

RF neutron spin flippers in time of flight Spin-Echo Resolved Grazing Incidence Scattering (SERGIS)

RF coils have been routinely used for Larmor labelling on the Offspec instrument at ISIS. These coils encode directional information via the neutron polarization using a series of parallelogram-shaped pole shoes which can be tuned to different angles with an RF gradient flipper in the centre of each magnet. We report on measurements of the magnetic field integral through the coils in reflection geometry for a range of scattering angles and different pole shoe angles. Such information is mapped out by measuring the phase of the neutron polarisation and the measurements are discussed in light of data on patterned silicon gratings with a dewetted polymer and the visibility of in-plane structures to SERGIS.RST/Fundamental Aspects of Materials and EnergyTechnici PoolBedrijfsondersteunin

Analysis of SESANS data by numerical Hankel transform implementation in SasView

SESANS data analysis has been implemented in the SasView software package, allowing SESANS experiments to be analyzed using a numerical Hankel transformation of isotropic small-angle scattering (SAS) models. The error of the numerical approximation is three orders of magnitude below typical experimental errors. All advanced data fitting features of SasView (multi-model fitting, batch fitting, and simultaneous/constrained fitting) are now also available for SESANS and this is demonstrated by examples of fitting SAS models to SESANS measurements.RST/Radiation, Science and TechnologyRST/Neutron and Positron Methods in MaterialsInstrumenten groepBedrijfsondersteunin

VC-precipitation kinetics studied by Small-Angle Neutron Scattering in nano-steels

Nanosteels are used in automotive applications to accomplish resource-efficiency while providing high-tech properties. Quantitative data and further understanding on the precipitation kinetics in Nanosteels can contribute to fulfil this goal. Small-Angle Neutron Scattering measurements are performed on a Fe-C-Mn-V steel, previously heat-treated in a dilatometer at 650°C for several holding times from seconds to 10 hours. The evolution of the precipitate volume fraction, size distribution and number density is calculated by fitting the experimental Small-Angle Neutron Scattering curves. The effect of phase transformation on precipitation kinetics is also discussed. Complementary Transmission Electron Microscopy, Scanning Electron Microscopy and Inductively Coupled Plasma Optical Emission Spectroscopy measurements are performed to support the Small-Angle Neutron Scattering data analysis.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.(OLD) MSE-1RST/Neutron and Positron Methods in Material