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Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P74
IN12-UFO: Innovative techniques for future triple-axis spectroscopy
Wolfgang Schmidt 1 , Karin Schmalzl 1 , Michael Ohl 1
1 Forschungszentrum Jülich, IFF, 52425 Jülich, Germany
The IN12 instrument is operated by the Research Centre at Jülich in collaboration with
CEA Grenoble at the Institute Laue Langevin in Grenoble. As a triple-axis spectrometer
for cold neutrons it is dedicated for high-resolution studies of low-energy excitations.
To meet further challenges as a state-of-the-art instrument IN12 is currently being upgraded
with a multi-analyser option. IN12 will then be equipped with a 2-dimensional
position sensitive detector and an array of fifteen analysers which can be rotated and
positioned individually in order to map the scattered beam on a user-chosen path in
Q-ω-space. We refer to this set-up as IN12-UFO (Universal Focusing Option). The innovative
flexibility of the analyser array is realized by a non-magnetic drive mechanism
where all relevant parameters are controlled by a laser-based optical absolute encoding
system. This is a completely new technique in neutron scattering instrumentation that
will drastically enhance the reliability and reproducibility of the multi-analyser. The
positioning mechanics consists of parallel rails with variable distance which allows to
position the individual analysers so that a) there are no gaps or overlaps as seen from
the sample (optimum coverage) and b) all reflected beams from the analysers meet at
one single focus point on their way to different spots on the detector surface. The focus
point is controlled by a movable diaphragm and provides the only opening between
analyser and detector shielding to prevent cross-talk and to keep the background low.
We will present further details of this set-up, point out its potential for future neutron
instrumentation and demonstrate its flexibility and multiplex advantages for specific
physical applications.
Fig. 1: IN12-UFO - a typical
configuration: Shown are the
flight paths between sample,
analysers and detector with
sample at (0,0) and the horizontal
axis as the direction
of the incident beam. All
units are in cm. The rails
of the array are shown by
the dashed lines. The border
lines of each analyser are
drawn in different colours to
demonstrate coverage and divergence.
Each colour also
represents a different energy.