Author: Mountford, B.
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Development of a Pair of Medium Energy X-Ray Absorption Spectroscopy Beamlines at Australian Synchrotron  
  • B.A. Pocock
    AS - ANSTO, Clayton, Australia
  • C. Glover, B. Mountford
    ASCo, Clayton, Victoria, Australia
  The Medium Energy X-ray absorption spectroscopy (MEX) beamlines are designed to perform routine, high throughput XAS experiments in the energy range 1.7 to 13.6 keV; split over two beamlines. This energy range is often overlooked but allows access to useful absorption K-edges of Si, P, S, Cl and Ca. Individual components of this system are relatively common, however the large number of components and broad functionality makes for a difficult integration challenge. Both beamlines are supplied by a single bending magnet, with the MEX2 beam being separated away by a pair of side bounce, cylindrically bent mirrors. MEX1 utilises a pair of multi stripe mirrors (Si, B4C and Rh) to access the desired energy range. Energy selection is performed by Double Crystal Monochromators (DCM), which are designed for both step and slew scanning. The end stations of both beamlines have Silicon Drift Detectors (SDD) and multiple ion chambers to facilitate fluorescence and transmission measurements. Sample temperatures can be controlled with any of the three helium recirculating cryostats or heaters. High Energy Resolution Fluorescence Detection (HERFD) experiments can be performed using either the single crystal spectrometer (MEX2) or the five crystal spectrometer (MEX1). MEX1 also includes a microprobe which uses a Kirkpatrick-Baez (KB) mirror to focus to a several micron spot. Given the energy range, attenuation of the photons is a particular challenge. These end stations are designed to minimise beam attenuation and maximise experiment versatility by selectively allowing high vacuum or helium environments in different regions. Removable windows and custom designed interfaces between components minimises the number of windows in the beam path which would have further attenuated photons.  
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Nanoprobe Beamline Stability Optimization at the Australian Synchrotron  
  • M. Semeraro, N. Afshar, C.M. Kewish
    AS - ANSTO, Clayton, Australia
  • B. Mountford
    ASCo, Clayton, Victoria, Australia
  • M.D. de Jonge
    ANSTO, Menai, New South Wales, Australia
  The Nanoprobe beamline is one of the most technically challenging beamlines within the Australian Synchrotron ANSTO BRIGHT program. The Nanoprobe will host a suite of x-ray mapping capabilities at spatial resolutions down to 60 nanometres. This extreme resolution target requires an overall length of over 100 m entailing high stability for optical components. The first part of the beamline will be sitting on the main building floor and will include two mirrors, two monochromators (DMM and DCM), a Secondary Source Aperture, plus all ancillary components. The end station will be situated in a satellite building, connected to the main building by a tunnel hosting the 50m UHV beam transfer pipe. The end station will host a pair of KB mirrors, the sample stages, multiple detectors and several beam inspection devices. There are several mechanical challenges that need to be overcome in the realisation of the beamline. Within the main building, we need to ensure the mechanical stability of the mirrors, the monochromators and the secondary source aperture. To reduce the vibration impact on the vertical displacement, we have opted for an all-horizontally deflecting optical scheme. Separated and isolated slabs are required, as well as mechanical isolation of vibration sources from the optical components. Thermal stability requirements are also challenging. Fundamental height above floor level requires thermal stability better than 0.05 C under the mirrors. Careful attention to materials selection and design is required for the end station to contain thermal drifts. Achieving these stabilities requires a careful approach as conventional HVAC systems bring vibration and air turbulence. This paper describes the design strategies adopted to optimize beamline components stability.  
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