MISANS Highlights
MISANS Tests at CG-1D at HFIR
Markus Bleuel (left) and Georg Brandl (right) in front of the MIEZE-Box for beam.
The development team for a MISANS (modulated-intensity small-angle neutron scattering) instrument has reported the first results from tests of the technique conducted at HFIR.
MISANS combines a highly collimated cold neutron beam, typically tailored by small-angle neutron scattering, with a variation on spin echo spectrometry called MIEZE (modulation of intensity by zero effort). It provides time resolution in a range from picoseconds to hundreds of nanoseconds.
The MISANS team, led by Jyotsana Lal of Argonne National Laboratory, reported results from the CG-ID beam line at HFIR. The first experiments at HFIR were done in collaboration with Robert Georgii and Georg Brandl from the Technical University of Munich, Markus Bleuel from the Technical University of Delft, Lee Robertson and Lowell Crow from ORNL, and Jack Carpenter from ORNL/Argonne.
Further tests are planned with improved polarization, detector size, and efficiency and a more optimized geometry. Scattering measurements with prototypical samples will be performed to explore the full potential of the technique.
Schematic of the MISANS instrument. The beam is polarized and analyzed using solid-state supermirror transmission polarizers. The entrance (e) and sample (s) coils operate at different frequencies ωe and ωs with a difference, ωd, of up to several megahertz to introduce a rapid sinusoidal oscillation of the intensity at the detector. The signal in a MISANS experiment is the measured contrast loss of these oscillations when a change in neutron velocity occurs in the sample (quasi-elastic broadening of the scattering).
A MIEZE signal not normalized to the incident intensity measured in a SANS geometry with 23 and 50 kHZ modulation frequency on a chopped neutron beam. The distance from the chopper to the detector was ~3.5 meters. The contrast, which contains the desired relaxation-time information in the scattering application, was above 40%. The Fourier time resolution was in the range of 1–100 ps.
References
- M. Köppe, M. Bleuel, R. Gähler, R. Golub, P. Hank, T. Keller, S. Longeville, U. Rauch, and J. Wuttke, “Prospects of resonance spin echo,” Physica B 266, 75–86 (1999).
- R. Golub, R. Gähler, and T. Keller, “A plane wave approach to particle beam magnetic resonance,” Am. J. Phys. 62, 779–788 (1994).
- M. Bleuel, K. Littrell, R. Gaehler, and J. Lal, “MISANS a method for quasi-elastic small angle neutron scattering experiments,” Physica B 356 1–4, 213–217 (2004).
- M. Bleuel, M. Broll, E. Lang, K. Littrell, R. Gahler, and J. Lal, “First tests of a MIEZE (modulated intensity by zero effort) -type instrument on a pulsed neutron source,” Physica B–Condensed Matter 371 (2), 297–301 (2006).
