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Beamline: E2 (RÖMO I)
X-Ray Double Crystal Monochromator
The RÖMO I experimental station occupies a radiation hutch divided into two separate sections, the upstream section housing an X-Ray double-crystal monochromator in non-dispersive geometry, the down-stream section accomodating the experimental apparatus. The incident radiation is unfocused, originating from a bending magnet located at a distance of approximately 35 m from the station.
The two crystals of the monochromator are mounted on a one-circle goniometer with an option to monitor angular positions through an angle decoder (resolution 10-4 deg., precision ±0.5"). Both crystals are piezo-driven to enable remotely controlled fine tuning as well as dynamic stabilization of the output intensity and periodic scanning motions in connection with a capacitive angle detector on the second crystal and appropriate driving electronics.
Typical experiments that are conveniently performed at this station range from X-ray absorption spectroscopy (EXAFS, XANES, magn. XAS, REFLEXAFS) to dynamical diffraction (X-ray interferometry, diffraction from multi-layer structures, multi-beam cases, DEXTER) and X-ray standing wave measurements on solid or liquid interfaces.
In the downstream section of the hutch these experiments are set-up on an optical table which can be adjusted in height by computer. In the figure below two special arrangements for EXAFS and X-ray standing wave measurements are indicated schematically, other combinations of instruments are easily realized.
In addition, a MBE facility is located outside the hutch. This facility features a baby chamber which can be used for transfers of samples under UHV conditions to other experimental stations such as RÖMO, RÖWI, BW1, BW2, or CEMO.
Applications
Determination of interface structures and phonon eigenvectors by means of x-ray standing waves.
X-ray absorption spectroscopy (EXAFS, XANES, magn. XAS, REFLEXAFS)
Dynamical diffraction (X-ray interferometry, diffraction from multi-layer structures, multibeam cases, DEXTER)
X-ray Fresnel reflection
Literature on Instrumentation
A. Krolzig, G. Materlik and J. Zegenhagen, Nucl. Instr. Meth. 208 (1983) 613
A. Krolzig, G. Materlik, M. Swars and J. Zegenhagen, Nucl. Instr. Meth. 219 (1984) 430
Instrument Specification
| Source (4.5 GeV) | bending magnet, Ec=16.6 keV beam size 1.3 x 3.0 mm FWHM vert. electron beam divergence 0.06 mrad FWHM | ||||
| Incident photon energy | ~ 5keV ... 80 keV | ||||
| Distance source-monochromator |  35m | ||||
| FWHM vert. | | Ee- | Ephot | | |
| | | 10 keV | 40 keV | | |
| | 5.3 GeV | 7.6 mm | 5.0 mm | | |
| | 3.7 GeV | 6.5 mm | 3.6 mm | | |
| max. FWHM hor. | 20 mm | ||||
| Monochromator | double crystal monochromator that can be operated in N2 or He atmosphere. Several combinations of sym. Ge or Si and asym. Si crystal sets for standard reflections and different asymmetry angles are available. | ||||
| Detectors | ionization chambers, NaI scintillation detector with analog and pulse- counting mode, Si(Li) detector, integrated sample/proportional counter assembly to monitor total electron yields from sample. Experimental control and data Acquisition: CAMAC, µVax II computer, multi-channel analyzer | ||||
