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Advanced Multilayer Monochromator

Advanced Multilayer Monochromator

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This multi-layer monochromator uses a matched pair of multi-layers to select a relatively wide energy bandpass beam from a white beam source.

For some experiments, the high energy resolution of perfect crystals is not required and the higher flux possible with multi-layers can reduce exposure times and speed data collection.

The energy range of multi-layer monochromators can be from ~50eV to >20keV depending on the multi-layer design selected. The energy resolutions (ΔE/E) achieved are typically a few percent, but depend on the multi-layer design. Multi-stripe multi-layers can be supplied to give additional energy ranges.

An optional lateral translation system enables a white beam bypass mode or permits the selection of multi-stripes depending on the orientation of the multi-layer mirrors.

Specifications

Vacuum<= 10-9 mbar
Max. bakeout temp.Up to 150°C
(depends on multi-layer)
Energy range~50eV to >20keV
(depends on multi-layer)
Multi-layer mountingPitching frame to keep input/
output beams parallel
Motorised motionsPitching angle (0-45°)
Longitudinal translation (0-550mm)
typical
Manual adjustmentsBeam offset (1-60mm)
Roll (±7.5mrad)

Examples

Example 1 – energy range 50-800eV

Fixed offset up to 60mm. Each mirror has three stripes with different multi-layer coatings to cover the energy range. The different stripes can be selected for use by motorised
adjustment of the horizontal linear slides located under the vacuum vessel.

The mirrors are mounted so that the first multi-layer mirror deflects the beam upwards and the second mirror deflects the beam downwards. The output beam is therefore parallel to the incoming beam but higher.

Pitch angle First & Second Mirror
Range 0 to 45° grazing incidence
Resolution <1μrad
Stripe 1
(low)
2
(medium)
3
(high)
Energy range 50-95eV 90-194eV 190-800eV
Materials Mo/Si Mo/B4C Ni/C or Ni/B4C
Bi-layer thickness 200Å 110Å 50Å
Thickness ratio Γ 0.8 0.5 0.5

Example 2 – energy range 1 – 20keV

Fixed offset up to 30mm. The mirrors are mounted so that the first multi-layer mirror deflects the beam sideways to the right and the second mirror deflects the beam to the left. The output beam is therefore parallel to the incoming beam but offset to the right.

Pitch angle First & Second Mirror
Range 0 to 12° grazing incidence
Resolution <1μrad
Parameter Multi-layer mirror
Bi-layer thickness 30Å
Multi-layer coating Mo/B4C
Energy resolution ΔE/E 2.5% FWHM at E=8keV
Reflectivity >=70% per optic at 8keV