Optical layout

beamline_overview.png

Beamline overview

This is a short description of the optical elements. For more details, see the beamline wiki.

Mirror M1

  • Objectives: vertical collimation + harmonic rejection.
  • Rh-coated Si rod.
  • Flat bendable.
  • Incidence angles: 0-7mrad.
  • Optical surface: 1150x80mm.
  • Water cooled.
  • Escaped when working at energy higher than 22keV.

Monochromator

  • Objectives: energy selection + horizontal focusing, in the range 4 - 40keV.
  • Double crystal, variable exit height.
  • Equiped with Si[220] (but Si[111] also possible).
  • Nitrogen cooled first crystal with a setpoint at -165°C.
  • Permanent feedback for parallelism optimization.
  • Bendable second crystal.

Mirror M2

  • Objectives: vertical focusing + harmonic rejection.
  • Rh-coated Si rod.
  • Flat bendable.
  • Incidence angles: 0-7mrad.
  • Optical surface: 1250x80mm.
  • Escaped when working at energy higher than 22keV.

Slits

  • Micrometric slits under vacuum - "Patisson" type - Conception and realisation : Bird & Tole
  • Slits 2 and 3 are water cooled and temperature is monitored with K thermocouples:
  • Tungsten Carbide blades thickness : 6mm.
  • Radius on the working edge : 3 mm.
  • Limit Switches : Baumer H75/80 (1 micron).
  • Vertical slits 3 have Renishaw Readhead RGH24 encoder (resolution: 1 micron)

Sample positionning

  • Height position adjusted versus the monochromator angle (precision about 1µm) via the table height (ht). Beam position on the sample is thus constant during an EXAFS scan.
  • Sample holder allows:
    • transverse and vertical translations
    • rotation (360°)
    • goniometric rotations (±7°)

Detection

  • Transmission mode: diodes collecting photons scattered by air in a black chamber for both incident and transmited intensity measurements.
  • Fluorescence mode: 30-element Ge detector (resolution about 300eV).