ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
With the assessment of the third generation of synchrotron-radiation sources, insertion devices (ID) are going to become extensively used. The choice of the ID field configuration allows the optimization of the photon flux at the desired energy. This attractive situation results in a much higher flux on optical elements, mainly on monochromators for which new cooling schemes have to be developed. These latter must be characterized under operating conditions and generally, the figure of merit for monochromators is the rocking curve (RC) measurement. By varying the ID field, the monochromator may be fully characterized with regard to the heat load. To achieve this aim, we have proposed and tested a double-crystal setup where a Si analyzer crystal installed in backscattering geometry (BSG) is coupled with a silicon p-i-n photodiode as the detection system (Fig. 1). The analyzer was a standard Si wafer (111) orientation, from which we used the following Bragg reflections: 333, 444, 555, 777, 888, 999, ... to measure the RCs of monochromators keeping the analyzer fixed. We were then able to probe the formers at the respective energies 5.9, 7.9, 9.9, 13.8, 15.8, 17.8 keV, etc. Setting the analyzer crystal in BSG, we get several-fold benefits from the method: (1) A very good angular resolution (∼10−6 rad) when one combines the BSG analyzer with narrow slits (∼100 μm). (2) A high-energy resolution yielding to a calibration of the monochromator with an accuracy better than 1 eV.(3) The analyzer crystal attenuates the reflected intensity which avoids the use of any scatterer foil to count the number of photons. We directly used photodiodes which are well known to respond linearly to radiation intensities and to have a high dynamic range (more than 6 decades). (4) No fine mechanics is needed for the analyzer, just a simple manual turntable can be used to set the analyzer in BSG through the utilization of a laser beam. Results on different tests for operating liquid–N2-cooled channel-cut monochromators at microfocus and high brilliance beamlines will be presented and discussed. We gratefully acknowledge the support of the ESRF EDS group, especially C. Riekel, P. Engström, I. Snigireva, M. Kocsis, P. Bösecke, and O. Diat. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1145714
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