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1. Responsible Person
Paul Zschack (630) 252-0860 (voice) (630) 252-0862 (fax) zschack@anl.gov
2. Introduction
The UNICAT mission is to provide advanced x-ray techniques to a diverse scientific community. Station 33-BM-B will provide resources for X-ray Absorption Spectroscopy (XAS) and Extended X-ray Absorption Fine Structure (EXAFS) to investigate and characterize catalyst performance and poisoning. This station will also provide for monochromatic x-ray topography techniques to characterize lattice defects and residual strain in single-crystal materials. Station 33-BM-C will function as a multi-purpose scattering facility capable of high resolution scattering with excellent energy resolution. This facility is intended to support advanced materials research as well as condensed matter physics. Primary usage by UNICAT members will encompass structural crystallography, diffuse x-ray scattering and magnetic x-ray scattering.
3. Source Characteristics
APS Dipole Bending Magnet - 5 mRad acceptance
4a. Optics Specification for 33-BM-B
Tunability: 2.4-40 KeV (planned) Energy Resolution (DE/E): 10-4 Demagnification: 1.4 Beamsize (v x h): 1.5 x 0.25 mm2 (ideal) Beam Divergence (v x h) 0.42 x 7.8 mrad2
4b. Optics Specification for 33-BM-C
Tunability: 2.4-40 KeV (planned) Energy Resolution (DE/E): 10-4 Demagnification: 1.0 Beamsize (v x h): 1.4 x 0.28 mm2 (ideal) Beam Divergence (v x h) 0.13 x 3.0 mrad2
5. Beamline Description
The optical design of the beamline includes a vertically collimating x-ray mirror followed by a double crystal monochromator and a vertically focusing mirror. The double crystal monochromator will use symmetric, asymmetric, and sagittal focusing crystals. The mirrors will be Pd coated to provide harmonic rejection, and maintain excellent reflectivity below about 24 KeV. (For operations above 24 KeV, the mirrors will be removed). The combination of optical elements is designed to allow maximum flexibility while preserving beam brilliance, and simultaneously optimizing energy and momentum transfer resolution. Aborption spectroscopy and anomolous scattering techniques will greatly benefit from energy resolution below the lifetime broadened core hole width. The monochromatic, focused beam will then be used in either experimental end-station. Operations time is therefore split between the two experimental enclosures.
6. Detectors
Current plans for detectors include: film, two dimensional CCD camera(s), linear sensitive proportional counters, solid state Ge & Si(Li) detectors, gas-filled proportional counters, gas-filled ion chambers, scintillation detectors, and assorted analyzing crystals.
7. Experimental Equipment
Station 33-BM-B will provide the platform and detectors required for absorption spectroscopy. Planned for this capability is a gas handling system which will permit investigation with sample cells in gaseous environments. This station will also include a topography imaging stage for the characterization of misorientation and strain in thin films and single crystal materials. Station 33-BM-C will contain a multi-axis goniometer for crystallography and scattering investigations. This Huber 4-circle goniometer has been modified to accommodate a two-stage helioplex cryostat for low temperature investigations. Much of this end-station equipment (such as cryostats, sample cells, detectors, etc.) will be shared with the general purpose scattering station on the UNICAT insertion device beamline. Specialized end-station equipment may only be available through special arrangement with the CAT.
8. Beamline Control & Data Acquisition
Beamline control will be provided through a SUN UNIX platform, using the EPICS control system (channel access calls) and distributed VME crates. Diffractometer control and data acquisition software are undecided at this time.
9. Beamline Status
Operations began in 2001. |
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