PRESS-MAG-O: A new facility to probe materials and phenomena under extreme conditions

In the recent years, several experiments performed under high magnetic fields (HMFs), at high pressure (HP) and/or at low temperature (LT) have led to spectacular discoveries in condensed matter. In many new systems, although challenging, it is strategic to perform a magneto-optical analysis, to investigate the phonon behavior in the far infrared (IR) domain. By combining HMF and HP in a wide temperature (T) range to perform concurrently IR magneto-optics and ac-magneto-dynamic experiments, it will be possible to achieve unique information on systems and/or new phenomena, almost impossible to obtain with standard spectroscopic methods. Here we present PRESS-MAG-O, a new facility under construction that will perform HP experiments under HMF in a wide T range. The system is expected to be operational by the end of 2008 and will be tested at SINBAD, the IR synchrotron radiation beamline operational since 2001 at DAΦNE (Double Annular Φ-factory for Nice Experiments), the storage ring of the INFN Frascati National Laboratory (LNF). While for IR experiments an interferometer will be used, for the magneto-dynamic experiments a SQUID magnetometer in the 10 Hz-2 KHz frequency range will be utilized. HP will be applied to samples by a Cu-Be diamond anvil cell (DAC), so that the device will be able to collect FTIR spectra and high harmonic ac susceptibility data in a dc magnetic field up to 8 T and to about 20 GPa in a wide temperature range (4.2-200 K).     

A differential pumping system to deliver windowless VUV photons at atmospheric pressure

In order to deliver VUV (vacuum ultraviolet) photons under atmospheric pressure conditions, a differential pumping system has been built on the DISCO beamline at the SOLEIL synchrotron radiation facility. The system is made of four stages and is 840 mm long. The conductance‐limiting body has been designed to allow practicable optical alignment. VUV transmission of the system was tested under air, nitrogen, argon and neon, and photons could be delivered down to 60 nm (20 eV).     

A new methodology for the near-surface strain measurement on Pd-Ag-Sn alloy

With the development of modern synchrotron sources, high-energy X-ray diffraction plays an important role in the residual stresses analysis of materials. This paper deals with the development of a new high-energy synchrotron X-ray diffraction (HESXRD) stress evaluation method for improving the near-surface strain measurement. For this purpose a new Monte Carlo simulation program has been developed to modelize any synchrotron radiation instrument. Futhermore conventional X-ray diffraction measurements have also been carried out after chemical etching, to define the surface and in-depth stresses of the sample, thus giving a reference to test the synchrotron radiation measurements. It has been shown that the reliability of this method is better than 5 μm. This method has been applied to a machined palladium alloy (Pd-Ag-Sn) plate substrate.     

Deformation cubic anvil press and stress and strain measurements using monochromatic X-rays at high pressure and high temperature

A system for deformation experiments under high pressure using a deformation cubic apparatus, with monochromatic synchrotron radiation, has been developed at beamline AR-NE7A, Photon Factory, KEK High Energy Accelerator Research Organization, Japan. We have conducted deformation experiments of fayalite using this new system at pressures up to 5 GPa and temperatures up to 1073 K, and successfully conducted the stress and strain measurements during the deformation.     

A new beamline for infrared microscopy in the SR center of Ritsumeikan University

A new beamline for an infrared (IR) microspectroscopy is under construction in the SR center of Ritsumeikan University. We designed an optical system which collects synchrotron radiation (SR) photons by installing one toroidal mirror and two plane mirrors in the storage ring chamber. As a result, the acceptance angle can be widened up to 250 mrad in horizontal and 63 mrad in vertical. Our aim is to develop an IR microspectroscopy beamline with spatial resolution of the order of sub micron from mid-IR to far-IR. In this paper, we present a designed optical system of IR microspectroscopy and the results of ray-tracing.     

DISCO: a low‐energy multipurpose beamline at synchrotron SOLEIL

DISCO, a novel low‐energy beamline covering the spectrum range from the VUV to the visible, has received its first photons at the French synchrotron SOLEIL. In this article the DISCO design and concept of three experimental stations serving research communities in biology and chemistry are described. Emphasis has been put on high flux generation and preservation of polarization at variable energy resolutions. The three experiments include a completely new approach for microscopy and atmospheric pressure experiments as well as a `classical' synchrotron radiation circular dichroism station. Preliminary tests of the optical design and technical concept have been made. Theoretical predictions of the beam have been compared with the first images produced by the first photons originating from the large‐aperture bending‐magnet source. Results are also reported concerning the cold finger used to absorb hard X‐ray radiation in the central part of the synchrotron beam and to avoid heavy thermal load on the following optics. Wavelength selection using monochromators with different gratings for each experimental set‐up as well as beam propagation and conditioning throughout the optical system are detailed. First photons comply very well with the theoretical calculations.     

铁磁形状记忆合金Mn2NiGa中应力诱发马氏体相的结构和磁性

采用金刚石对顶砧高压装置（DAC）和同步辐射X射线光源法,对Heusler类型的磁性形状记忆合金Mn₂NiGa的结构进行了原位高压X射线衍射测量,并对卸载后的受压样品进行了磁测量.实验观察到材料在室温下分别在0.77 GPa和20 GPa压力下发生了两次不可逆结构相变：马氏体相变和两种不同马氏体间的等结构相变.同时加压使马氏体结构中产生了大量的缺陷,造成了严重的晶格畸变,致使马氏体结构的矫顽力提高了近10倍,达到204 kA/m.结果发现,加压处理造成样品马氏体相饱和磁化强度的大幅度 关键词： 铁磁形状记忆合金 2NiGa')" href="#">Mn₂NiGa 高压 同步辐射     

Highly resolved transmission infrared microscopy in polymer science

Over the last few years, the use of synchrotron-based IR sources for high-resolution microspectroscopy has been a subject of great interest. The special characteristics of synchrotron radiation allow one to obtain high quality IR spectra at high spatial resolution using commercial grade IR microscopes situated at IR beamlines. The application of this technique to the study of polymeric materials is discussed, with examples from a series of heterogeneous polymeric materials, which include polymer blends and fibre-reinforced polymer composites, from studies undertaken at the MIRAGE Beamline, LURE, Paris, France.     

IR synchrotron diagnostics. Part 1: Wide-band long-focus optics

An optical channel for extracting, transporting, and applying (to a detector) IR synchrotron radiation covering a wide wavelength range is developed. The design and study of optical systems with long-focus entrance objective and mirror lenses, as well as with a field condenser lens, are reported. Practical use of IR optics combined with integrated and position-sensitive detectors in accelerator experiments with synchrotron radiation is described.     

Pump−probe experiments at the TEMPO beamline using the low‐α operation mode of Synchrotron SOLEIL

The SOLEIL synchrotron radiation source is regularly operated in special filling modes dedicated to pump–probe experiments. Among others, the low‐α mode operation is characterized by shorter pulse duration and represents the natural bridge between 50 ps synchrotron pulses and femtosecond experiments. Here, the capabilities in low‐α mode of the experimental set‐ups developed at the TEMPO beamline to perform pump–probe experiments with soft X‐rays based on photoelectron or photon detection are presented. A 282 kHz repetition‐rate femtosecond laser is synchronized with the synchrotron radiation time structure to induce fast electronic and/or magnetic excitations. Detection is performed using a two‐dimensional space resolution plus time resolution detector based on microchannel plates equipped with a delay line. Results of time‐resolved photoelectron spectroscopy, circular dichroism and magnetic scattering experiments are reported, and their respective advantages and limitations in the framework of high‐time‐resolution pump–probe experiments compared and discussed.     

New high-power source of directional electromagnetic radiation

A new source of electromagnetic radiation in a wide spectral range can be based on multiple contactless deflection of the beams of charged particles in a circular channel. The radiation with wavelengths ranging from submillimeter to radio ranges can be generated using nonrelativistic electrons. Directional radiation is obtained at relativistic energies. The IR, optical, and UV radiation can be generated. The X-ray and gamma-radiation can be obtained at relatively high energies. The new source is compared with the source of synchrotron radiation. The radiation intensity at energies of 1–2 GeV is relatively high, since strong currents are possible in the ring channel. The channeling and synchrotron emission are simultaneously obtained at relatively small (several tens of nanometers) internal diameters of the ring.     

Determination of the dielectric function of porous silicon by high-order laser-harmonic radiation

Porous-silicon reflectance has been determined over a large energy range, from 1 eV to 16 eV, by combining a NIR/visible/UV spectrometer with a new VUV light source as laser-harmonic radiation. The porous-silicon dielectric function was deduced from reflectance measurements by Kramers–Kronig analysis. We point out that, for the first time, laser harmonics have been applied in the optical characterization of materials as a new and suitable alternative to synchrotron radiation. Received: 9 January 2001 / Accepted: 28 April 2001 / Published online: 20 June 2001     

Ionic to electronic dominant conductivity in Al2(WO4)3 at high pressure and high temperature

Electrical conduction and crystal structure of Al₂(WO₄)₃ at 400 °C have been studied as a function of pressure up to 5.5 GPa using impedance methods and synchrotron radiation X-ray diffraction, respectively. AC impedance spectroscopy and DC polarization measurements reveal an ionic to electronic dominant transition in electrical conductivity at a pressure as low as 0.9 GPa. Conductivity increases with pressure and reaches a maximum at 4.0 GPa, where the conductivity value is 5 orders of magnitude greater than the 1 atm value. Upon decompression, the conductivity retains the maximum value until the sample is cooled at 0.5 GPa. The high pressure-temperature X-ray diffraction results show that the lattice parameters decrease as pressure increases and the crystal structure undergoes an orthorhombic to tetragonal-like transformation at a pressure ∼3.0 GPa. The change of conduction mechanism from ionic to electronic may be explained by means of pressure-induced valence change of W⁶⁺→W⁵⁺, which results in electron transfer between W⁵⁺-W⁶⁺ sites at high pressure.     

Semianalytical theory of focusing synchrotron radiation by an arbitrary system of parabolic refracting lenses and the problem of nano-focusing

It has been shown that an arbitrary system of parabolic refracting lenses does not change the shape of the Gaussian wave function of a synchrotron radiation beam. Only three parameters of the wave function change, for which the recurrent formulas are derived. These formulas allow one to perform quickly and accurately the calculation of optical properties of an arbitrary system of lenses. The parameters of the radiation beam calculated by the developed method have been compared to the results of the theory of continuously refracting lens. It has been shown that both approaches give surprisingly close values. The problem of focusing the beam to a nanometer size is discussed. A two-lens system has been proposed, which can provide a five-fold increase in the number of photons inside the focus, although we failed to decrease the beam size.     

Experimental system for X-ray magnetic diffraction under extreme conditions

An experimental system for X-ray magnetic diffraction (XMD) under extreme conditions was constructed on the beamline BL39XU at SPring-8. This system aims at studying magnetic properties of ferromagnets through the measurements of magnetic form factors under the conditions of low temperature (5 K), high magnetic field (6 T) and high pressure (10 GPa). This system consists of a superconducting magnet (SCM), a diamond anvil cell (DAC), a two-axis manipulator for the DAC, a five-axis goniometer for the SCM, and an X-ray polarizer with a phase plate. Details of this system are presented. Experimental results on uranium telluride are shown as a performance test with this instrumentation.     

The high‐resolution diffraction beamline P08 at PETRA III

The new third‐generation synchrotron radiation source PETRA III located at the Deutsches Elektronen‐Synchrotron DESY in Hamburg, Germany, has been operational since the second half of 2009. PETRA III is designed to deliver hard X‐ray beams with very high brilliance. As one of the first beamlines of PETRA III the high‐resolution diffraction beamline P08 is fully operational. P08 is specialized in X‐ray scattering and diffraction experiments on solids and liquids where extreme high resolution in reciprocal space is required. The resolving power results in the high‐quality PETRA III beam and unique optical elements such as a large‐offset monochromator and beryllium lens changers. A high‐precision six‐circle diffractometer for solid samples and a specially designed liquid diffractometer are installed in the experimental hutch. Regular users have been accepted since summer 2010.     

Experimental attempts to measure non-collinear local magnetisation

Representing atomic magnetic moments as simple vectors has limitations when applied to systems in which orbital moments, or significant spin-orbit coupling is present. These phenomena are associated with interactions leading to non-collinearity in the magnetisation distribution. Several experimental techniques are available to probe such non-collinearity. The most direct is to measure both the magnitude and direction of the magnetic interaction vectors, which give its Fourier components. Such measurements are now becoming possible for antiferromagnets with the advent of a new generation of neutron polarimeters, which will allow both greater geometric flexibility and higher precision. However, up to now non-collinear magnetisation distributions have been revealed by more indirect means. Polarised neutron flipping ratio measurements can give only a single component of the magnetic interaction vector directly. However, the special geometric properties of the interaction vector and the symmetry breaking properties of an applied field can be exploited to obtain evidence of non-collinearity in the magnetisation distribution even from such limited data.     

Quantitative estimation of thermal contact conductance of a real front‐end component at SPring‐8 front‐ends

The thermal contact conductance (TCC) of a real front‐end component at SPring‐8 has been quantitatively estimated by comparing the results of experiments with those of finite‐element analyses. In this paper one of the methods of predicting the TCC of a real instrument is presented. A metal filter assembly, which is an indirect‐cooling instrument, was selected for the estimation of the TCC. The temperature of the metal filter assembly for the maximum heat load of synchrotron radiation was calculated from the TCC that is expected under normal conditions. This study contributes towards the ongoing research program being conducted to investigate the real thermal limitation of all front‐end high‐heat‐load components.     

Single crystal x-ray diffraction with a synchrotron source in a mdac at low temperature

Abstract

A new diamond anvil cell and a helium flow cryostat have been developed for x-ray diffraction on single crystals at low temperatures and high pressures using the white radiation of a synchrotron beam. This novel instrument especially enables continuous change of sample temperature and pressure without any adjustment of alignment. A minimum temperature of 46 K has been reached.

Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’, Daresbury Laboratory 20-21 July 1991     

Effects of hydrogen etching process on the structural and optical properties of nano-crystalline diamond films

In this work, hydrogen etching method is applied to improve the quality of nano-crystalline diamond (NCD) films grown from hot-filament assisted chemical vapor deposition (HFCVD) system. From the characteristics of the structure and optical property, the grain size and surface roughness decrease while the optical transmission increase obviously under certain deposition parameters (gas pressure and substrate temperature) and longer etching time. Soft X-ray transmission measurements by synchrotron radiation are also carried out on the NCD films. The result shows that the X-ray transmission has an obvious improvement when the NCD film is fabricated from the hydrogen etching method. And the transmittance reaches 53.3% at X-ray photon energy of 258 eV, which has met the requirement for X-ray mask materials.