Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P22
The Wide Angle Spin Echo Spectrometer Project WASP at ILL
Peter Fouquet 1 , Bela Farago 1 , Catherine Pappas 2 , Phillip M. Bentley 2 ,
Ferenc Mezei 2
1 Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France – 2 Hahn-Meitner-
Institut, Glienicker Str. 100, 14109 Berlin, Germany
This presentation will give an overview of design and projected performance of the new
ILL spin echo spectrometer WASP (Wide Angle SPin echo spectrometer). At present,
ILL offers two spin-echo only spectrometers to the user community specialized in high
signal (IN11) and high resolution (IN15), respectively. The aim of the project is to
increase the detection and acceptance angle of the high signal spectrometer IN11 by
changing the design of the magnetic coils.
The design of WASP profits from the experience gained with the novel spectrometer
SPAN which has recently been commissioned at the Hahn-Meitner Institute in Berlin,
Germany [1]. In the SPAN/WASP design nearly perfect 360 o field symmetry is achieved
by replacing the conventional collinear NSE field solenoids by a pair of anti-Helmholtz
solenoids placed above and below the neutron beam plane. Furthermore, careful field
analysis revealed that within this design a near perfect cos 2 field shape [2] can be
created along the neutron trajectories, so that field correction can be minimized.
We will present improvements on field optimization calculations using Biot-Savart field
calculations and Monte Carlo raytracing calculations. Very recently we have incorporated
genetic algorithms into our design package. Using this tool we have been able to
accelerate the rather complex coil design with typically more than 10 free parameters.
[1] C. Pappas et al.i, Physica B 297 (2001) 14.
[2] C.M.E. Zeyen et al., IEEE Trans. Magn. 24 (1988) 1540.
[3] P.M. Bentley et al., Physica B, accepted.