Network: Perfect crystal neutron optics

• Research unit: EU RFP
• Project number: 96.0263

Key words (English)

Neutron physics; neutron optics; perfect crystals; ultra small angle neutron scattering (USANS)

Alternative project number (English)

EU project number: FMRXCT960057

Research programs (English)

EU-programme: 4. Frame Research Programme - 10.1 Stimulation of training and mobility

Short description (English)

See abstract

Further information (English)

Full name of research-institution/enterprise:
Paul Scherrer Institut PSI / ETH Zürich
Labor für Neutronenstreuung

Partners and International Organizations (English)

Atominstitut der österreichischen Universitäten, Wien, ISIS Spallation Neutron Source, Didcot (UK)

Abstract (English)

The main work in 2001 was the experimental comparison of the new crystal design set up with other concepts. The new crystal design is based on channel cut Si (111) crystals for 3 reflections each, where the backside of the individual crystals is not plane parallel to the reflecting surface. By successively changing from single reflection, plane parallel crystals to the mentioned new design and by introducing Cd in the beam path at several positions, the theoretical explanation for the origin of the worse resolution of the old crystal design could be confirmed.
For these measurements the background on the TOPSI beamline at the spallation neutron source SINQ at PSI was reduced by new shielding. In this way the signal to background ratio could be improved by more than one order of magnitude compared to former measurements. It was shown that a mechanical coupling and a vibration reduction by an optical bench is not necessary. The much simpler set up with the monochromator crystal on the second axis of TOPSI and the analyzer crystal on the detector arm gave the same resolution.
Ultra small angle neutron scattering (USANS) will be a permanent option on TOPSI. For this purpose a series of constructive modifications are being performed. A repetition of the mentioned measurements on the reflectometer ADAM at the Institute Laue-Langevin (ILL) at Grenoble showed that background is still the limiting factor on TOPSI, so the main effort has to be put on new detector shielding.

Publication: M. Villa: 'Optimiertes Kristalldesign für ein Doppelkristall-Diffraktometer''
(PhD Thesis, TU Vienna, 2002).

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 96.0263