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Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P47
Johann Spectrometer for High Resolution X-ray Spectroscopy
Pavel Machek 1 , Edmund Welter 2 , Wolfgang Caliebe 2 , Ulf Brüggmann 2 ,
Günter Dräger 3 , Michael Fröba 1
1 Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität
Gießen, Heinrich-Buff-Ring 58, 35392 Gießen, Germany – 2 Hamburger Synchrotron
Strahlungslabor (HASYLAB) am Deutsches Elektronen Synchrotron (DESY),
Notkestraße 85, 22607 Hamburg, Germany – 3 Martin-Luther-Universität Halle-
Wittenberg, FB Physik, Friedemann-Bach-Platz, 606108 Halle(Saale), Germany
We present a vacuum Johann spectrometer for inelastic x-ray scattering and high
resolution fluorescence spectroscopy that has been installed at the DORIS III storage
ring in HASYLAB. The spectrometer utilizes spherically bent crystals with a maximum
size of 150 mm and cylindrically bent crystals as dispersive optical elements. Standard
radius of curvature of the crystals is 1000 mm, however, the design of the spectrometer
also facilitates measurements with smaller and larger bending radii. Up to four crystals
are mounted on a revolving crystal changer and thus it is possible to change crystals
without breaking the vacuum. The spectrometer works at fixed Bragg angle, the energy
transfers are obtained by varying the incident photon energy. The measurements are
preferably performed in a dispersive set-up with a sample located inside a Rowland
circle and with a position sensitive detector on the circumference. The vacuum in the
spectrometer tank is typically 10-6 mbar. The sample chamber is separated from the
tank vacuum either by 25 um Kapton windows which allow to measure samples under
ambient conditions or by two gate valves. The spectrometer is currently installed at
wiggler beamline W1 whose working range is 4-10.5 keV and the typical flux at the
sample of 5x10 10 photons/s/mm 2 . The capabilities of the spectrometer are illustrated
by resonant inelastic experiments on 3d transition metals and rare earth compounds,
and by the chemical shift measurements on chromium compounds.