The MRCAT Insertion Device line is fully operational and is used primarily for spectroscopy and fluorescence mapping experiments. The Bending Magnet line is fully operational and is available for spectroscopy.
Wide energy range monochromator
We currently have a double crystal monochromator with direct drive air bearings and two sets of crystals: Si (111) and Si (311) which span the energy range from 4.8 keV to 65 keV. The first crystals are side-cooled with liquid nitrogen.
The second crystals have a piezoelectric tuning actuator with a.c. feedback and a Bragg-normal motion which permits some degree of fixed-offset operation. In combination with the multichannel scaler electronics described below, we are able to take complete EXAFS scans of 1000 eV in under 1 min.
Harmonic rejection mirror
The MRCAT beamline has a 60 cm long flat harmonic rejection mirror with Pt and Rh coatings. This mirror resides in the experimental station and may be moved vertically in or out of the beam as the experiment requires.
Basic microfocusing capability is now available. our system consists of a separate kinematically mounted table of out own design with a vibration isolation breadboard and positioning systems for sample, microscope and Kirkpatrick-Baez mirrors. The minimum spot size for the current mirrors is approximately 5m×5m. The system has been used for fluorescence mapping and spectroscopy experiments. A new microprobe with x-ray emission spectroscopy capability is being developed.
High energy angle-resolved photoemission
A Scienta ARPES system is available for collaborative experiments.
Wide energy range monochromator
We currently have an Oxford Si (111) monochromator consisting of a water-cooled first crystal designed by the IIT Center for Synchrotron Radiation Research and Instrumentation (CSRRI) and a 50 mm long second crystal which provides an energy range of 4.0 keV to 32 keV from the fundamental reflection. The second crystal operates at 50% detuning for removal of harmonics. The experimental station is 25 m from the source which provides a relatively high photon flux density without the need of focusing optics. Changing the edge energy is exceptionally easy through the use of a Python program which allows the user to select the element to be measured. In combination with the multichannel scaler electronics, we are able to take complete EXAFS scans of 1000 eV in about 4 min.
The MRCAT sector is currently equipped with 22 cm long aluminum spectroscopy ion chambers for use in transmission mode x-ray absorption spectroscopy and 6 smaller Cornell-type ion chambers which may be mounted on the spectroscopy rail for special purposes. Three Lytle-type fluorescence detectors are also available. Data collection is through a standard instrument chain of Keithley electrometers, V-F converters and a 32 channel multichannel scaler. The multichannel scaler permits continuous of the energy and the goniometer detector motors.
The MRCAT instrumentation also includes a single-element YAP scintillation detector and a 19-element solid state detector for dilute XAFS and Fluorescence measurements. At the present time, we are limited to approximately collection times of greater than 6 s per data point with the Ge detector. A 4-element Vortex detector is available primarily for use at the bending magnet line and additional 4-element Vortex detectors from the APS Detector Pool can be easily integrated into the beamline as needed.
Bent Laue fluorescence analyzers are also available upon request.
Data acquisition is handled by the MX system, written by William Lavender. A preliminary manual as well as source code is available at http://mx.iit.edu