ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
The results of the experimental testing of the parabolic focusing pyrolytic graphite x-ray monochromator (mono) on the wiggler (2 T) synchrotron radiation (SR) beamline of the VEPP-3 storage ring are presented. The monochromatization and the focusing of x radiation in both vertical and horizontal directions are provided by the optical properties of the parabolic surface of revolution of the properly shaped pyrolytic graphite crystal attached to the parabolic-machined brass support. A single crystal is a half of the parabolic surface 160 mm long and ∼19 mm minimal focus length. The sagittal radii are changed from 10 to 30 mm. The available photon energy range is 7–20 keV on the first harmonic of reflection. The second order of reflection still has a reasonably high intensity comparable with the intensity of the first one; due to this fact the energy range can be extended up to 40 keV. The change of the energy of the monochromatized x radiation is accomplished by the simple vertical shift of a mono; according to this shift the space location of the focal point is also vertically displaced. For the study the mono was placed at a distance of ∼16 m from the source point, so the accepted horizontal divergence of the "white'' SR beam was ∼2 mrad. The mono was supplied with an In–Sn conical collimator to prevent parasitic scattering radiation and to avoid the possible undesirable characteristic emission x-ray lines in the working energy range mentioned above.X-ray imaging of different cross sections (horizontal–vertical, horizontal–longitudinal, vertical–longitudinal) of the focal point space region was performed by the point-by-point scanning of a NaI(Tl) scintillation counter supplied by the pinhole collimator of ∼80 μm in diameter made in the lead disk screen of 2 mm thickness. The achieved size of the focal spot of ∼0.4 (horizontal)×0.7(vertical) mm2 is in a good agreement with theoretical expectations and preliminary computer modeling. In fact, the main role in an extending of the focal spot is the large angular mosaic spread (∼1° FWHM) of the graphite crystal used. The registration of Compton scattered radiation spectra from the acrylic cylinder of 5 mm diameter placed at the focus position by a Si(Li) liquid–nitrogen-cooled solid state detector was conducted to measure the behavior of spectra of monochromatic x radiation output with respect to the longitudinal location of the footprint of a primary SR beam on the parabolic surface of the graphite crystal. The possible applications of the presented mono for the construction of a "middle'' space resolution class of SR based x-ray fluorescence microprobes and other usages such as powerful concentrators of x radiation are discussed and described. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1145736
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