Extreme Sample Environments Research Articles

An experimental procedure to determine quantitative muon Knight shifts

Muon Knight-shift measurement are experimentally rather challenging as in most setups one does not have a direct way of measuring the external magnetic field applied to the sample. Here we show, a way to overcome this problem and suggest a suitable sample mounting and correcting scheme. This enables us to quantitatively determine the correct Knight-shift values even in extreme sample environments where a separate measurement of the externally applied magnetic field by means of NMR or additional µSR is not feasible or practical.

Commissioning of the novel Continuous Angle Multi-energy Analysis spectrometer at the Paul Scherrer Institut.

We report on the commissioning results of the cold neutron multiplexing secondary spectrometer CAMEA (Continuous Angle Multi-Energy Analysis) at the Swiss Spallation Neutron Source at the Paul Scherrer Institut, Switzerland. CAMEA is optimized for efficient data acquisition of scattered neutrons in the horizontal scattering plane, allowing for detailed and rapid mapping of low-energy excitations under extreme sample environment conditions.

Understanding quantum materials under extreme sample environments

Understanding quantum materials under extreme sample environments

DEMAND, a Dimensional Extreme Magnetic Neutron Diffractometer at the High Flux Isotope Reactor

A two-dimensional (2D) Anger camera detector has been used at the HB-3A four-circle single-crystal neutron diffractometer at the High Flux Isotope Reactor (HFIR) since 2013. The 2D detector has enabled the capabilities of measuring sub-mm crystals and spin density maps, enhanced the efficiency of data collection and phase transition detection, and improved the signal-to-noise ratio. Recently, the HB-3A four-circle diffractometer has been undergoing a detector upgrade towards a much larger area, magnetic-field-insensitive, Anger camera detector. The instrument will become capable of doing single-crystal neutron diffraction under ultra-low temperatures (50 mK), magnetic fields (up to 8 T), electric fields (up to 11 kV/mm), and hydrostatic high pressures (up to 45 GPa). Furthermore, half-polarized neutron diffraction is also available to measure weak ferromagnetism and local site magnetic susceptibilities. With the new high-resolution 2D detector, the four-circle diffractometer has become more powerful for studying magnetic materials under extreme sample environment conditions; hence, it has been given a new name: DEMAND.

MultiFLEXX - The new multi-analyzer at the cold triple-axis spectrometer FLEXX

The first experimental characterization of a multiple energy analysis wide angle backend for a cold triple-axis spectrometer is reported. The multi-analyzer module MultiFLEXX employs 155 detection channels which simultaneously probe an extensive range in wavevector and energy transfer. Successful mapping of magnetic excitations in MnF2 and Ho demonstrate order of magnitude gains in data collection efficiency using this novel type backend. MultiFLEXX is competitive to standard triple-axis spectroscopy in terms of energy resolution and signal-to-noise ratio. A minority of the detector channels is affected by spurious signals inherent to this multiplexing concept. The characteristic signature of these spurious signals easily allows for their discrimination. The instrument concept focuses on detection efficiency in the horizontal scattering plane which makes it an ideal technique for fast mapping and parametric studies including extreme sample environment.

SENJU: a new time-of-flight single-crystal neutron diffractometer at J-PARC.

SENJU is a new single-crystal time-of-flight neutron diffractometer installed at BL18 at the Materials and Life Science Experimental Facility of the Japan Accelerator Research Complex (J-PARC). The diffractometer was designed for precise crystal and magnetic structure analyses under multiple extreme sample environments such as low temperature, high pressure and high magnetic field, and for diffraction measurements of small single crystals down to 0.1 mm3 in volume. SENJU comprises three choppers, an elliptical shape straight supermirror guide, a vacuum sample chamber and 37 scintillator area detectors. The moderator-to-sample distance is 34.8 m, and the sample-to-detector distance is 800 mm. The wavelength of incident neutrons is 0.4-4.4 Å (first frame). Because short-wavelength neutrons are available and the large solid angle around the sample position is covered by the area detectors, a large reciprocal space can be simultaneously measured. Furthermore, the vacuum sample chamber and collimator have been designed to produce a very low background level. Thus, the measurement of a small single crystal is possible. As sample environment devices, a newly developed cryostat with a two-axis (ω and φ axes) goniometer and some extreme environment devices, e.g. a vertical-field magnet, high-temperature furnace and high-pressure cell, are available. The structure analysis of a sub-millimetre size (0.1 mm3) single organic crystal, taurine, and a magnetic structure analysis of the antiferromagnetic phase of MnF2 have been performed. These results demonstrate that SENJU can be a powerful tool to promote materials science research.

Neutron and X-ray Diffraction from Exotic Magnets in Pulsed Magnetic Fields

Magnetic fields obtained by discharging a large capacitor bank through Helmholtz coils can be produced in excess of 25 T for relatively short periods of time, ~ 1 msec and longer. When combined with modern facilities for diffraction at modern neutron and synchrotron x-ray sources, one can study the structure and phase diagrams of new materials under extremes of magnetic field. I will present two such studies, each focussing on a new magnetic material which exhibit exotic low temperature states. I will show time-resolved neutron Laue diffraction on the multiferroic magnet MnWO4 [1], and time-resolved synchrotron x-ray studies of large magneto-elastic effects in the geometrically-frustarted pyrochlore magnet Tb2Ti2O7 [2], both in magnetic fields up to ~ 30 T. Such studies of new materials in extreme sample environments can be very revealing as to the nature of their exotic low temperature states.

A low temperature nonlinear optical rotational anisotropy spectrometer for the determination of crystallographic and electronic symmetries.

Nonlinear optical generation from a crystalline material can reveal the symmetries of both its lattice structure and underlying ordered electronic phases and can therefore be exploited as a complementary technique to diffraction based scattering probes. Although this technique has been successfully used to study the lattice and magnetic structures of systems such as semiconductor surfaces, multiferroic crystals, magnetic thin films, and multilayers, challenging technical requirements have prevented its application to the plethora of complex electronic phases found in strongly correlated electron systems. These requirements include an ability to probe small bulk single crystals at the μm length scale, a need for sensitivity to the entire nonlinear optical susceptibility tensor, oblique light incidence reflection geometry, and incident light frequency tunability among others. These measurements are further complicated by the need for extreme sample environments such as ultra low temperatures, high magnetic fields, or high pressures. In this review we present a novel experimental construction using a rotating light scattering plane that meets all the aforementioned requirements. We demonstrate the efficacy of our scheme by making symmetry measurements on a μm scale facet of a small bulk single crystal of Sr2IrO4 using optical second and third harmonic generation.

Optimization of multi-channel neutron focusing guides for extreme sample environments

In this work, we present and discuss simulation results for the design of multichannel neutron focusing guides for extreme sample environments. A single focusing guide consists of any number of supermirror-coated curved outer channels surrounding a central channel. Furthermore, a guide is separated into two sections in order to allow for extension into a sample environment. The performance of a guide is evaluated through a Monte-Carlo ray tracing simulation which is further coupled to an optimization algorithm in order to find the best possible guide for a given situation. A number of population-based algorithms have been investigated for this purpose. These include particle-swarm optimization, artificial bee colony, and differential evolution. The performance of each algorithm and preliminary results of the design of a multi-channel neutron focusing guide using these methods are described. We found that a three-channel focusing guide offered the best performance, with a gain factor of 2.4 compared to no focusing guide, for the design scenario investigated in this work.

Probing static and dynamic correlations in matter under extreme conditions: Concept of multi-purpose instrument at the European Spallation Source

Properties of neutrons, in particular high penetration depth for most materials, make them very powerful for studying matter under extreme conditions, e.g. high pressures or magnetic fields. A new generation of high power spallation neutron sources, such as the existing SNS and J-Parc and the coming ESS, brings neutron scattering in extreme environments to a completely new level. Indeed, measurements of smaller samples, use of more complex equipment and neutron instruments optimized for operation with extreme sample environment become readily available. The latter is actually one of the most important factors contributing to the field. In this paper a novel concept of an instrument for extreme environments at the ESS is presented. The main feature of the Extreme Conditions Instrument is its multi-purpose nature. It is not optimized for a single scattering technique but combines in a balanced way elastic (Diffraction and Small Angle Neutron Scattering) and inelastic capabilities. Such a concept enables effective combination of neutron scattering with a state-of-the-art sample environment independent of the complexity, dimensions and transportability of the latter. In addition, all available types of neutron experiments can be performed at the same thermodynamic conditions. The instrument concept has been verified by Monte-Carlo ray-tracing simulations and the results for instrument operation modes are compared with world-class instruments.

Two-dimensional resonant magnetic soft X-ray scattering set-up for extreme sample environment

The newly built MagSAXS (magnetic small-angle X-ray scattering) set-up dedicated to the direct two-dimensional measurement of magnetic scattering using polarized synchrotron radiation in extreme sample environments is presented. Pure optical transport of the image is used to record the magnetic scattering with a two-dimensional CCD visible-light camera. The set-up is able to probe magnetic correlation lengths from the micrometer down to the nanometer scale. A detailed layout is presented along with preliminary results obtained at several beamlines at Synchrotron SOLEIL. The presented examples underline the wide range of possible applications spanning from correlation lengths determination to Fourier transform holography.

Tests of modulated intensity small angle scattering in time of flight mode

We report results of tests of the MISANS technique at the CG-1D beamline at the High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL). A chopper at 40 Hz simulated a pulsed neutron source at the beamline. A compact turn-key MISANS module operating with the pulsed beam was installed and a well characterized MnSi sample was tested. The feasibility of application of high magnetic fields at the sample position was also explored. These tests demonstrate the great potential of this technique, in particular for examining magnetic and depolarizing samples, under extreme sample environments at pulsed sources, such as the Spallation Neutron Source (SNS) or the planned European Spallation Source (ESS).

The XIPHOS diffraction facility for extreme sample environments

The XIPHOS diffraction facility for extreme sample environments

Instrumentation for fast in-situ X-ray structure measurements on non-equilibrium liquids

Probing the structure of non-equilibrium melts is important to advance the fundamental understanding of liquids and glass formation and development of new materials. Combined use of high flux, high energy X-rays and fast large area detectors enables in-situ probing of liquids suspended and laser beam heated in an aerodynamic levitator. High-energy X-rays provide high resolution data and avoid the complications of multiple scattering and absorption within the sample. The use of non-contact processing, heating, and measurement enables deep supercooling and avoids the need for corrections due to scattering by the container. The technique provides an extreme temperature sample environment for measurements at rates of 5 spectra per second from superheated and supercooled liquids.

XIPHOS: expanding the experimental envelope to extreme sample environments

XIPHOS: expanding the experimental envelope to extreme sample environments

Probing ore deposits formation: New insights and challenges from synchrotron and neutron studies

The understanding of the physico-chemical processes leading to the formation and weathering of ore deposits plays an increasingly important role in mineral exploration. Synchrotron, neutron, and nuclear radiation are contributing to this endeavour in many ways, including (i) support the modelling of ore transport and deposition, by providing molecular-level understanding of solvent–solute interaction and thermodynamic properties for the important metal complexes in brines, vapours, and supercritical fluids over the range of conditions relevant for the formation of ore deposits (i.e., temperature 25–600 °C; pressure 1–10 9 Pa; and fluid compositions varying from hypersaline (e.g., >50 wt% NaCl) to volatile-rich (e.g., CO 2, CH 4, and H 2S)); (ii) track the fluids that travelled through rocks and predict their ore-forming potential by analysing hydrothermal minerals and remnants of those fluids trapped in these minerals as ‘fluid inclusions’; (iii) characterize the biochemical controls on metal mobility in soils to predict the geochemical footprint of a buried mineral deposit. X-ray fluorescence (XRF), particle-induced X-ray emission (PIXE), and X-ray absorption spectroscopy (XAS) are the most common techniques used in support of mineral exploration. Analytical challenges are related to (i) the complexity of heterogeneous natural samples, which often contain only low concentrations of the elements of interest; (ii) beam sensitivity, especially for redox-sensitive elements in aqueous fluids or biological samples; (iii) extreme sample environments, e.g. , in-situ study of fluids at high pressure and temperature. Thus, critical improvements need to be made on a number of fronts to: (i) develop more efficient detectors, able to map large areas in heterogeneous samples (e.g. , 10 6–10 8 pixels per map), and also to collect a maximum number of photons to limit sample exposure and beam damage; (ii) integrate techniques (e.g., XRF, XAS, and X-ray diffraction (XRD)) on a single beamline, and promote synergy between neutron-, synchrotron-, and nuclear microprobe-based methods; (iii) advance the theory (e.g., quantitative XANES interpretation; X-ray extended range technique (XERT) measurements) to gain maximum information from the hard-won datasets.

Versatile inelastic neutron spectrometer (VINS) project for J-PARC

We have proposed a Versatile Inelastic Neutron Spectrometer (VINS) for the spallation neutron source at the Materials and Life Science Facility (MLF), Japan Proton Accelerator Research Complex (J-PARC). VINS is a direct-geometry Fermi chopper spectrometer designed to provide considerably high neutron flux with moderate energy and Q resolutions. VINS is characterized by its wide energy and Q range (0.5<Δ E<1000 meV and Q< 40 Å −1 at Δ E=1000 meV), enabled by an array of detectors covering large solid angle [−30°<2 θ<130° horizontally and −30°< φ<30° vertically (2.8 Sr)]. Monte Carlo ray-tracing simulation estimates the sample position neutron flux as high as roughly 1×10 6 neutrons cm −2 s −1 for the Δ E/ E i∼5% mode at E i=10 meV. With these wide E– Q coverage and high neutron flux, VINS will be one of the most efficient and versatile inelastic spectrometers at J-PARC. Target science ranges from conventional solid-state physics, such as highly correlated electron systems, frustrated magnets and relaxors, to rather interdisciplinary areas, exemplified by glasses, quasicrystals, polymers and liquids. A particular focus is placed on extreme sample environments; high magnetic-field and high-pressure environments are planned.

ThALES—towards the next generation cold neutron three-axis spectrometer

After 20 years of successful science the cold neutron three-axis spectrometer IN14 will undergo profound modifications. The so-called ThALES—three axis low energy spectroscopy—project will implement state-of-the art neutron optics in order to increase the over-all count-rate by one order of magnitude, to provide an efficient, easy-to-use polarization option, to extend the kinematic range and to adapt the experimental zone to extreme sample environment.

Magnetic imaging with soft x-ray spectroholography

We present recent advances in imaging magnetic nanostructures via lensless holographic x-ray techniques. In addition to the tunable energy and polarization this method also uses the coherent photon flux that is now available at third generation synchrotron radiation sources. Our spectroscopic imaging technique is based on the direct Fourier inversion of a holographically formed interference pattern, thus we refer to it as spectroholography. By exploiting the magnetic dichroism in resonance at the L3 absorption edges of the magnetic transition metals (wavelength of ∼1–2nm and energy of ∼700–900eV), images of magnetic nanostructures have been obtained with a spatial resolution below 50nm. Using Si3N4-membrane substrates we combine in our experimental setup the sample itself rigidly with the holographic mask structure consisting of an 800nm gold layer with a micronsized object aperture and a nanosized reference hole on the backside of the membrane. Such a compact implementation leaves plenty of space for installing extreme sample environments such as high magnetic fields and low temperatures that are difficult to combine with conventional x-ray imaging techniques based on focusing optics.

SAXS/WAXS experiments using extreme sample environments

By using high intensity synchrotron radiation X-ray beam lines it is possible to study the structural evolution of materials exposed to extreme conditions like high temperatures, pressure, etc. This possibility creates scope for real time investigations of structural development relevant to manufacturing conditions. The devitrification of glass with the cordierite composition is one of such processes. This process takes place at temperatures in excess of 1000 °C. Combined small and wide angle X-ray scattering experiments have been performed. From these experiments we have been able to derive temperature parameters required to grow monodisperse crystalline particles in an amorphous matrix. By controlling the amount of crystallisation inducing metal ions and the temperature profile the crystalline volume fraction and particle size can be tailored to the required properties. Another example of the use of extreme conditions is the realignment behaviour of smectic-A liquid crystals under the influence of magnetic fields. This is an interesting subject since smectic liquid crystals are thought to be candidates for faster switching devices in for instance liquid crystal displays. The mechanism of reorientation is still not well understood. Time-resolved X-ray scattering experiments in fields up to 10 T will be described. All the results described in this overview have been recently obtained in collaboration with a number of groups. In this text the emphasis will be on the instrumentation aspects of the work and the importance that sample environments can have for experiments in material science. The full results will be published elsewhere.