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Methoden und Instrumentierung Vortrag: Do., 12:10–12:30 D-V41
High Gain Focusing Optics for Stress and Local Texture Measurement at
the Materials Science Diffractometer STRESS-SPEC at FRM-II
Ulf Garbe 1 , Joana Rebelo-Kornmeier 2 , Andreas Ostermann 3 , Michael
Hofmann 3
1 GKSS Forschungszentrum, Max-Planck-Str. 1, D-21502 Geesthacht – 2 HMI, BENSC,
Glienickerstr. 100, D-14109 Berlin – 3 FRM-II, TU München, Lichtenbergstr. 1, D-
85747 Garching
In response to the development of new materials and the application of materials and
components in new technologies the direct measurement, calculation and evaluation of
textures and residual stresses has gained worldwide significance in recent years. Nondestructive
analysis for phase specific residual stresses and textures is only possible by
means of diffraction methods. In order to cater for the development of these analytical
techniques the new Materials Science Diffractometer STRESS-SPEC has been installed
recently at the new reactor FRM-II to be equally applied to texture or residual stress
analyses by virtue of its flexible configuration and high neutron flux at the sample
position [1]. The results of our first user experiments show that small gauge volumes
down to 1x1x1 mm 3 can be easily used for residual stress measurements. However,
with measurement points deeply embedded in components the primary slit has to be
positioned far away from the scattering center thus causing a poor definition of the
nominal gauge volume. Here we present the results of simulations where the primary
slit is replaced by a parabolic focussing guide which provides a good definition of a
small gauge volume even deep within components and a substantial flux increase at
the sample position.
In addition the combination of intensity increase provided by the focussing guide
together with the extension of the existing PSD-detector will enable local texture measurements
[3] in a short timescales and also 3-D texture mapping is realistic. Currently
even with the high flux of STRESS-SPEC the measuring time per pole figure amounts
up to 14 hours using a gauge volume of 2x2x2 mm 3 . Simulations are presented to
demonstrate the possible gains using two or three position sensitive detectors, all installed
at the same position in 2θ with different χ angles. In this way more orientations
are detected at the same time. Together with the focussing guide due to the neutron
flux increase and the reduced number of necessary sample orientations local texture
measurements with high spatial resolution will be possible.
[1] M. Hofmann, R. Schneider, G.A. Seidl, J. Rebelo-Kornmeier, R.C. Wimpory, U.
Garbe and H.-G. Brokmeier, Physica B, in press.
[2] C. Schanzer, P. Böni, U. Filges, T. Hils, Nucl. Instr. and Meth. A 529 (2004) 6368.
[3] C.S.Choi, H.J. Prask S.F. Trevino, J. Appl. Cryst. 12, (1979) 327-331.