The toroidal mirror for single-pulse experiments on ID09B

Abstract ID09 is a dual-purpose beamline dedicated to time-resolved and high-pressure experiments. The time-resolved experiments use a high-speed chopper to isolate single pulses of x-rays. The chopper is installed near the sample (focal spot) and the shortest usable opening time depends on the sharpness of the vertical focusing. In the 16-bunch mode, the opening window of the chopper has to be reduced to 0.300 µs to select single pulses of x-rays. This can only be achieved by lowering the height in the chopper tunnel to 0.143 mm. To ensure a reasonable transmission though the tunnel, we have built a very precise toroidal mirror that focuses the beam 22.4 m downstream in M= 0.677 geometry. The 1.0-m long silicon mirror is curved by gravity into a near perfect toroid with a meridional radius of 9.9 km. The curvature is fine-tuned by a push stepper motor that works from below. The figure error from the gravity sag and the correcting force is less than 0.3 µrad and the polishing error is 0.7 µrad (rms) over the central 450-mm part of the mirror. The measured size of the polychromatic focus is 0.100 x 0.070 mmh x mmv in agreement with the prediction from the long-trace-profiler at the ESRF. The small focus, which integrates the entire central cone of the U17 undulator, is the result of superb optical quality, fine-control of curvature, a strain-free mount, a vibration free cooling system and careful alignment

Iron Storage within Dopamine Neurovesicles Revealed by Chemical Nano-Imaging

Altered homeostasis of metal ions is suspected to play a critical role in neurodegeneration. However, the lack of analytical technique with sufficient spatial resolution prevents the investigation of metals distribution in neurons. An original experimental setup was developed to perform chemical element imaging with a 90 nm spatial resolution using synchrotron-based X-ray fluorescence. This unique spatial resolution, combined to a high brightness, enables chemical element imaging in subcellular compartments. We investigated the distribution of iron in dopamine producing neurons because iron-dopamine compounds are suspected to be formed but have yet never been observed in cells. The study shows that iron accumulates into dopamine neurovesicles. In addition, the inhibition of dopamine synthesis results in a decreased vesicular storage of iron. These results indicate a new physiological role for dopamine in iron buffering within normal dopamine producing cells. This system could be at fault in Parkinson's disease which is characterized by an increased level of iron in the substancia nigra pars compacta and an impaired storage of dopamine due to the disruption of vesicular trafficking. The re-distribution of highly reactive dopamine-iron complexes outside neurovesicles would result in an enhanced death of dopaminergic neurons

White light diffraction patterns of amplitude and phase zone plates

The polychromatic properties of the Fresnel zone plate, Gabor zone plate, phase reversal zone plates and kinoform lens are studied. The polychromatic intensity in the diffraction patterns on these plates has been computed and the influence of Gaussian spectral filters is shown. Also, the distributions of illuminance and chromaticity in the diffraction patterns and along the optical axis, have been calculated for several zone numbers. The results obtained are discussed and compared for the different plates. © 1979Peer Reviewe

Miroir simple-ou multi-couches à courbure variable pour microfocalisation de rayonnement synchrotron X

Une optique X focalisante de grande efficacité a été développée et testée. Elle se compose d'un miroir de petite dimension monté sur un courbeur mécanique à 2-moments de base de pivots flexibles. Les principaux avantages de ce système sont l'accordabilité en énergie, la conservation du flux et la possibilité d'interchanger le miroir. Une procédure de mise en forme du miroir en ligne a été diveloppée pour minimiser la taille de la tache focalisée avec une précision inférieure au microradian. Un exemple de réalisation est présenté, dans lequel des multicouches à gradient latéral ainsi qu'un dépôt simple couche d'iridium ont été utilisés pour couvrir une gamme d'énergie entre 7 keV et 30 keV. Avec un facteur de dégrandissement de 128 (tests effectués sur la ligne BM5 de l'ESRF) des tailles de spot inférieures au micromètre ont été obtenues. Le gain maximal en flux à 20 keV était de 535 (688 à 13 keV)

Hard X-ray microscopy with reflecting mirrors status and perspectives of the ESRF technology

Third génération synchrotron sources allow imaging at high energy with sub-micron resolution. The reflective optics Systems, with their high efficiency and achromatic nature are promising approaches towards that goal. The Kirkpatrick Baez (KB) technology, being developed at the ESRF, has achieved a measured spot size of $0.16 \times 0.21$ $\mu$m at 20.5 keV on the ID19 beamline. Despite non-perfect optics, nearly diffraction size has been achieved in one direction. Examples of projection full field and microfluorescence scanning imaging are reported. The expected performance of these Systems under coherent illumination and their applications are discussed in view of the progress achieved in optical manufacturing technology

Future metrology needs for synchrotron radiation mirrors

An international workshop on metrology for X-ray and neutron optics, the first of its kind, was held March 16-17, 2000, at the Advanced Photon Source at Argonne National Laboratory. Engineers and scientists from around the world met to evaluate current metrology instrumentation and methods used to characterize the surface figure and finish of long, grazing-incidence optics used in synchrotron radiation beamlines, and to consider future needs for synchrotron, FEL, and neutron sources

Future metrology needs for synchrotron radiation mirrors

An international workshop on metrology for X-ray and neutron optics, the first of its kind, was held March 16-17, 2000, at the Advanced Photon Source at Argonne National Laboratory. Engineers and scientists from around the world met to evaluate current metrology instrumentation and methods used to characterize the surface figure and finish of long, grazing-incidence optics used in synchrotron radiation beamlines, and to consider future needs for synchrotron, FEL, and neutron sources