DESCRIPTION
The Materials Science and Powder Diffraction Beamline is devoted to high resolution powder diffraction and high pressure powder diffraction using diamond anvil cells.
The beamline operates between 8 and 50 keV. This energy range covers very well the desirable range for almost any powder diffraction experiment, and at the same time it is possible to perform both total scattering experiments, and high pressure diffraction, for which it is desirable and sometimes necessary to have high energy sources (E > 30 KeV).
To accommodate the different experimental techniques there are two experimental end stations, one devoted to high resolution powder diffraction and the second one to high pressure experiments.
STATUS
BL04-MSPD is in full operation since 2012 giving service to public and proprietary research users.
TECHNICAL SPECIFICATIONS
| Photon Energy Range | 8 - 50 keV |
|---|---|
| Flux at sample | ~ 4 1012 ph/s |
| Energy resolution | 2 10-4 |
| Beam size at sample | variable: 1.5 x 5mm2 to 0.010 x 0.040mm2 |
| Beam divergence at sample | variable |
COMPONENTS
| Source | Superconducting Wiggler SCW31 |
|---|---|
| Insertion Device (ID) | Superconducting wiggler with short period length. The actual K-value can be set with the current in the superconducting coils. At its maximum K = 6.08 the critical energy is Ec = 12.5 keV. The K-value can be reduced for experiments at lower energies |
Parameters
| Material | Superconducting coils |
|---|---|
| Period | 31 mm |
| Number of periods | 60.5 |
| K Max | 6.08 |
| Photon source size (FWHM) | 0.65 x 0.1 mm2 (HxV) |
| Photon source div. (FWHM) | 1.4 x 0.18 mrad2 (HxV) |
Detectors
| Powder Diffraction Station | |
|---|---|
| Mythen detector (PSI Detector group/Dectris) | 6 Modules (Dectris/PSI Detectors group) Strip-pitch 50µm Radius 550mm Covered Angular Range 40˚ Energy Range 8 - 30keV |
|
MAD26: High Resolution Detector
|
13 Channels with Si 111 and Si 220 crystals |
| High Diffraction Station | |
|---|---|
CCD camera, SX165 (Rayonix) |
Area: round, 165mm diameter |
LAYOUT
To allow for the different applications the optical layout has to be flexible. Two main configurations can be distinguished:
| Mirrored mode | 8-40keV |
|---|---|
| Unmirrored mode | > 40keV |
The positions for the main components are:
| ID center | 0 m |
|---|---|
| Gate valve of Front End FE | 18.2 m |
| M1 collimating mirror | 20 m |
| DCM Double Crystal Monochromator | 23.5 m |
| KB-mirror (vertical) | 30.9 m |
| KB-mirror (horizontal) | 31.3 m |
| HP station 1 | 32 m |
| PD station 2 | 35 m |
Mirror 1 collimates the beam in vertical direction by a mechanical bender, thus increasing the energy resolution. It has three stripes with different coatings (Pt, Rh, Si) to adapt reflectivity and harmonic suppression to the different energy ranges.Besides, it also reduces the heat load on the monochromator and is therefore externally water cooled. The glancing angle of the mirror is 2mrad.
The crystal in the monochromator downstream M1 is a Si 111. To preserve energy resolution and flux at the sample under high heat load the crystals are externally cooled with liquid nitrogen. By doing this either thermal expansion is reduced as well as the conductivity of silicon is increased compared to room temperature values.
(I) Mirrored mode 7 - 40keV (II) Un-mirrored mode >40keV
For high pressure and total scattering experiments it is important to access considerable high energies. For this setup the mirror can be moved out of the beam path. Instead a KB- mirror system using Multilayers can be inserted to focus the beam on station 1. The KB-mirror is applicable in the energy range of about 20-50keV and can also be used together with the collimating mirror M1. They are placed 1.1m and 0.7m upstream station 1 on a granite table.
Monochromator
| Type | Si(111) Double Crystal with long 2nd crystal |
|---|---|
| Gap between crystals | 10 mm (variable) |
| Absorbed power | 670 W (worst-case conditions) |
KB mirrors
| Vertical Focusing Mirror | Horizontal Focusing mirror | |
|---|---|---|
| Type | Elliptically bent mirror | Elliptically bent mirror |
| Substrate | Si | Si |
| Coating material | Multilayer | Multilayer |
| Angle of incidence | 5 - 10 mrad | 5 - 10 mrad |
| Mirror length | 300 mm | 300 mm |
