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Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P29
The A- and Gi-SAXS dedicated SAXS instrument at BESSY 7T wiggler
Armin Hoell 1 , Ivo Zizak 1 , Sylvio Haas 1 , Dragomir Tatchev 2 , John Banhart 1
1 Hahn-Meitner Institute Berlin, Department of Materials, D-14109 Berlin – 2 Institute
of Physical Chemistry, Bulgarian Academy of Sciences, BG-1113 Sofia, Bulgaria
The SAXS instrument (7T-WLS-SAXS), on the high brilliance wiggler beamline at
BESSY, has been designed to perform two advanced scattering techniques, ASAXS [1]
and GISAXS [2]. It has been installed at the monochromatic beam of the 7T wiggler at
BESSY. The SAXS instrument runs in timesharing with a magnetic scattering experiment.
Therefore, the detector chamber is based on an air cushion system (Fig. 1) to be
removable. The X-ray energy can be varied between 4.5 keV and 26 keV using a double
crystal monochromator with Si 111 crystals. The photon flux at the sample position
is in the order of magnitude of 10 9 s −1 to 10 11 s −1 , depending on optics and slits
settings. The beam can be focused by the two mirrors and the sagitally curvable 2 nd
monochromator crystal. The SAXS chamber is equipped with a position sensitive 2D
gas detector (20 cm * 20 cm). A MAR CCD detector with 16.5 cm diameter is available
also. One of the two 2D detectors is directly mounted at a vacuum flange at the end of
the scattering beam path. The sample - detector distance can continuously be varied
between about 74 cm and 374 cm. An edge welded bellow system with an inner diameter
of 25 cm is stretched between the beam diagnostics chamber and the beamstop
chamber (Fig. 1). To realize all lengths between 18 cm and 318 cm the bellow system
is divided into two pieces, whereby the longer part can move down into the optical
bench (Fig. 1b) on its own rail system. The advantage of using an edge welded bellow
system in comparision to other instruments [3, 4] is that the sample detector distance
can vary continuously, while having easy access to the detector. The whole scattering
beam path with the optical bench can be tilted up to 3.2 ◦ with respect to the horizontal
that is used in case of GISAXS. The sample environments are not directly fixed to
the described detector chamber. Different sample environments are available or can be
installed, like sample changers under vacuum or normal air conditions, a high temperature
furnace (up to 1000 ◦ C), and a GISAXS furnace to be used in reflection geometry.
[1] A. Hoell, F. Bley, A. Wiedenmann, J. P. Simon, A. Mazuelas, P. Boesecke: Scripta
Mater. 44 (2001) 2234. [2] A. Naudon, and D. Thiaudiere, J. Appl. Cryst. 30 (1997)
822. [3] H.-G. Haubold, K. Gruenhagen, M. Wagener, H. Jungbluth et al: Rev. Sci.
Instrum. 60 (1989) 1943. [4] S. Lequien, L. Goirand, and F. Lesimple: Rev. Sci.
Instrum. 66 (1995) 1725.
Fig. 1: Sketches of the two main configurations of the SAXS
chamber are shown. The sample is positioned in the front of
the big valve. The sample-detector distance can be varied between
750 mm and 3750 mm as shown in the picture. Four
z-stages are used to align the optical bench and to lift up the
detector support by up to 3 ◦
in case of GISAXS. The instrument
is based on an air cushion system.