The Neutron Optics Group
The group of neutron optics is active in various fields of instrumental development and experimental support. Our activities concerns 5 main directions:
1) Production of polarized 3He for neutron instrumentation
We operate HELIOS, a MEOP (metastability exchange optical pumping) station for the production of polarised 3He gas, which is used by several instruments at the FRM II to perform neutron polarisation analysis. In addition to the continuous work on improving and optimising the HELIOS facility to reach highest degree of polarisation, we support the users of 3He at FRM II instruments by developing glass vessels for 3He to be introduced into the instrumental neutron beam-line, and specific magnetic cages to maintain very homogeneous magnetic fields across the 3He volume.
2) Construction of Neutron Guides
In cooperation with the instrument responsibles and the construction group we design and construct the neutron guides for all instruments at the FRM II according to their special needs. Especially in the neutron guide hall great care was taken to design optimised multi-structure shielding to maintain the low background level.
3) Operation of the Neutron Reflectometer TREFF
In collaboration with JCNS we have built the general-purpose neutron reflectometer NOSPEC TREFF. It consists of 2 consequent Bragg crystals to produce a mono-energetic neutron beam, a polarising unit, a rotateble target station, a beam analyser unit, and a position sensitive detector, which is moveable around the target. The instrument will serve for testing of super mirrors, Bragg crystals and for scientific research.
4) Production of Super Mirrors
We operate a sophisticated sputtering lab. It is equipped with a sputtering facility that allows the production of 1m long super mirror elements for neutron guides. The substrate elements are prepared in a clean room and introduced from there directly into the tempering and glowing chamber of the sputtering machine to condition the surface. After moving in the main chamber the metallic layers were deposited. Sofar m values up to 2.6 have been achieved; further developments towards higher m or polarising mirrors are under progress.
5) Crystal Development
A special crystal lab is being accomplished. Here we have equipment to treat crystals mechanically and to characterize them with a modern x-ray diffractometer. The development of more efficient diffraction crystals for neutrons is envisaged