O. Hignette

Bio: O. Hignette is an academic researcher from European Synchrotron Radiation Facility. The author has contributed to research in topics: Metrology & Beamline. The author has an hindex of 15, co-authored 38 publications receiving 1154 citations.

The ID23-2 structural biology microfocus beamline at the ESRF

Abstract: The first phase of the ESRF beamline ID23 to be constructed was ID23-1, a tunable MAD-capable beamline which opened to users in early 2004. The second phase of the beamline to be constructed is ID23-2, a monochromatic microfocus beamline dedicated to macromolecular crystallography experiments. Beamline ID23-2 makes use of well characterized optical elements: a single-bounce silicon (111) monochromator and two mirrors in Kirkpatrick–Baez geometry to focus the X-ray beam. A major design goal of the ID23-2 beamline is to provide a reliable, easy-to-use and routine microfocus beam. ID23-2 started operation in November 2005, as the first beamline dedicated to microfocus macromolecular crystallography. The beamline has taken the standard automated ESRF macromolecular crystallography environment (both hardware and software), allowing users of ID23-2 to be rapidly familiar with the microfocus environment. This paper describes the beamline design, the special considerations taken into account given the microfocus beam, and summarizes the results of the first years of the beamline operation.

Efficient sub 100 nm focusing of hard x rays

Abstract: An x-ray beam with energy of 20.5keV has been efficiently focused down to a spot size as small as 90nm×90nm by a Kirkpatrick–Baez reflecting mirrors device. The first mirror, coated with a graded multilayer, plays both the role of vertical focusing device and monochromator, resulting in a very high flux (2×1011photons∕s) and medium monochromaticity (ΔE∕E∼10−2). Evaluation of the error contributions shows that the vertical focus is presently limited by the mirror figure errors, while the horizontal focus is limited by the horizontal extension of the x-ray source. With a gain in excess of a few million, this device opens up new possibilities in trace element nanoanalysis and fast projection microscopy.

Development of a new state‐of‐the‐art beamline optimized for monochromatic single‐crystal and powder X‐ray diffraction under extreme conditions at the ESRF

Abstract: A new state-of-the art synchrotron beamline fully optimized for monochromatic X-ray diffraction at high pressure and high (or low) temperature is presented. In comparison with the old high-pressure beamline ID30, this new beamline exhibits outstanding performance in terms of photon flux and focusing capabilities. The main components of this new instrument will be described in detail and compared with the performance of beamline ID30. In particular, the choices in terms of X-ray source, X-ray optics, sample environment and detectors are discussed. The first results of the beamline commissioning are presented.

Multi-segmented piezoelectric mirrors as active/adaptive optics components

Abstract: The angular acceptance of piezoelectric (Pzt) bimorph mirrors is limited by the maximum length of commercially available Pzt ceramic plates. To overcome this limit and manufacture longer devices, several (2n + 1) 150 mm-long bimorph Pzt stacks were assembled side-to-side. Two prototype mirrors, 450 (n = 1) and 750 (n = 2) mm long, were designed, assembled, polished and optically characterized. They are fully UHV compatible and are now installed in the monochromatic section of the ESRF beamlines ID26 and ID32. Both mirrors cover the full range of required bending radii (1 km concave–3.5 km convex). Junctions between segments do not spoil the optical surface quality. The surface slope error r.m.s. can be kept well below 1 arcsec over the full bending range. Adaptive compensation for low-frequency figure errors was shown to be easy and reliable. After compensation, residual shape errors are of the order of 40 nm r.m.s. over 700 mm.

Incoherent x-ray mirror surface metrology

Abstract: In this paper we describe an x-ray long trace profiler (XLTP) that takes an x-ray synchrotron beam as a wavefrontreference. According to results of experiments conducted on the Optics Beamline at the ESRF, this instrument allows us tomeasure surface slope errors with precision and accuracy better than 25 nrad (rms) and 50 nrad (mis), respectively, with alateral resolution of 5 mm in the meridional and less than I mm in the sagittal direction.A very similar technique was developed to figure in situ mirrors mounted on mechanical benders into a stigmatic shape formicrofocusing purposes. Micron spot sizes were achieved without difficulty and submicron precision should be possible.The technique is particularly useful if energy tunability is needed. The emphasis has been put on automation and speed ofthe measurement.Keywords: Surface metrology, x-ray mirrors, active optics, microfocusing, synchrotron radiation, multilayers. 1. INTRODUCTION In the light of recent experiments using coherence it became evident that x-ray mirrors for synchrotron radiation are still notgood enough"2. The quality of mirrors and of multilayer substrates must be extremely high to preserve the coherence ofthird generation synchrotron sources. This also applies to focusing and spherical waves. For example, in microdiffractionexperiments applied, e.g., to high pressure studies, the microimage of the source, regarding both the small size and thepurity, should not be degraded by the focusing optics. Whereas highly perfect single crystals do not affect coherence, theslope errors of the best presently available mirrors and multilayer imperfections have shown to deteriorate the phasecontrast significantly. In the following we will briefly recall what are the requirements for mirror quality.A height error Lz of a surface reflecting x-rays at a grazing angle generates a peak-to-valley (PV) phase distortion Ltp

Structure-Guided Evolution of Cyan Fluorescent Proteins Towards a Quantum Yield of 93%

Abstract: Cyan variants of green fluorescent protein (CFPs) are widely used as donors in FRET experiments. Here, a new CFP, mTurquoise2, is developed, which displays a high-fluorescence quantum yield and a long mono-exponential fluorescence lifetime.

Breaking the 10 nm barrier in hard-X-ray focusing

Abstract: X-ray sources such as free-electron lasers offer the potential to study matter at unprecedented spatial and temporal resolution. But that potential is limited by the poor quality of conventional X-ray optical elements. An in situ technique that corrects for wavefront aberrations and allows X-rays to be focused to a spot just 7 nm wide could provide a solution.

Compression curves of transition metals in the Mbar range: Experiments and projector augmented-wave calculations

Abstract: The ambient temperature equations of state (EoS) of iron, cobalt, nickel, zinc, molybdenum, and silver have been measured by x-ray diffraction. These transition metals were compressed using diamond anvil cells with a helium pressure transmitting medium. The maximum pressure reached during these experiments varied between 65 GPa (for cobalt) and 200 GPa (for iron). This work completes previous measurements on six other metals [Phys. Rev. B 70, 094112 (2004)] to quantify the differences between ab initio calculations and experiment on a large experimental set of transition metals. The compression curves of iron, cobalt, nickel, zinc, molybdenum, silver, platinum, and gold are also calculated ab initio within the density-functional theory (DFT) formalism using the projector augmented-wave (PAW) method and different exchange-correlation functionals (LDA, GGA-PBE, GGA-PBEsol). The difference between PAW and available all-electron calculations is found to be negligible up to very high pressures. The success of each exchange-correlation functional is correlated with the atomic number. For all metals, the bulk modulus becomes overestimated at high pressure. In addition, this extended data set of metals' EoS enables to reduce further, but marginally, the systematic uncertainty of the high-pressure metrology based on the ruby standard.

Quasihydrostatic equation of state of iron above 2 Mbar.

Abstract: The compression curve of iron is measured up to 205 GPa at 298 K, under quasihydrostatic conditions in a diamond anvil cell. Above 150 GPa, the compression of this metal is significantly higher than previously measured under nonhydrostatic conditions. The same compression curve is also calculated ab initio and the deviation between experiment and theory is clearly established. A formulation of the equation of state of iron over a large pressure and temperature range, based on the current data and existing shock-wave data, is also proposed. Implications for the Earth's core are discussed.