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CHESS East
F2 Station
F2
Facility Description
The F2 station in CHESS East receives half of the powerful output from the positrons as
they pass through the East 24-pole wiggler. Since 1998 this station has been used
primarily by the macromolecular crystallography users for multi-wavelength anomalous
diffraction (MAD) measurements. A new water cooled collimating mirror has been
installed upstream of the monochromator to reduce the heat load and to
provide better energy resolution for the user. This station has a new double crystal monochromator
as of 1999 to ease the transition to different energies. The monochromator
typically has a pair of vertically diffracting Si(111) crystals with the second crystal
providing sagittal focusing in the horizontal dimension to focus ~2milliradians of beam
to ~3.5mm. The monochromator is designed to provide x-rays from 7.9 keV to
14 keV (0.89 - 1.57 Å).
The offset of the monochromated beam is 2.5 cm. downward from the white beam
position. The vertical and horizontal beam sizes can be controlled by a pair of water
cooled slit systems positioned in front of the monochromator, about 20.6 m from the
wiggler.
For vertical focusing, a Rhodium coated silicon mirror is available (with a critical
angle constant of 67 keV-mrad). It is located 3.3 meters upstream from the beryllium
entrance window in the F2 hutch, which is 25.4 meters from the source, and can deflect the
monochromated beam upward from 0 to 25 mrad without being obscured by the beryllium window
holder. Si(220) crystals are being
constructed to provide even better energy resolution to the MAD user.
The F2 hutch houses a standard CHESS optical table with MacCHESS hardware and an
ADSC Quantum-210 detector. The center of the hutch is 27.2 meters from the wiggler source and
6.5 meters from the F2 monochromator in the F-coffin.
F2 hutch
F2 station summary
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Source: |
e+s,
24 pole wiggler, 1.7 mrad (horizontal) |
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Source size: |
FWHM (horizontal) = 3.76 mm, FWHM (vertical) = 0.944 mm |
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Distance to
source: |
27.2 m to center of hutch |
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Carbon filters: |
0, 1, 2.5, 5, 10, 15, 25 mm (optional) |
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Cave slit sizes: |
0 to 50 mm (horizontal), 0 to 12 mm (vertical) |
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Flux (100mA)(p/s): |
8x1011 doubly-focused into 3.6
mm x 0.32 mm |
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Monochromators: |
Double-bounce downward, offset 25.4 mm |
|
Crystals |
Sag. Focus. |
Energy
(keV) |
 |
 |
/2 |
/3 |
|
Si
(111) |
Yes |
7.9-16 |
1.3 |
0.008 |
0.093 |
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Monochromatic Mirrors: |
|
Type |
Length |
Vertical Focus |
|
E* c(keV-mrad) |
|
Rh
coated Si |
24 inch |
Yes |
|
67.0 |
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Au-coated |
9 inch |
No |
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80.0 |
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Quartz |
9 inch |
No |
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33.2 |
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Float Glass |
9 inch |
No |
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30.6 |
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Typical Experiments: |
Type
|
Energy Range |
Equipment Setup
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MAD |
7.9-16 keV |
Oscillation Camera, mirror #1 |
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Last Update:
2006-09-21
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