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TECHNI Sintesi della relazione

Project ID: HPRI-CT-1999-50005
Finanziato nell'ambito di: FP5-HUMAN POTENTIAL
Paese: Switzerland

Remanent supermirror neutron polariser

One method to polarise cold neutrons is to use supermirrors (SM), which transmit neutrons of one spin state and reflect the others. Normally these SM polarisers require for an external magnetic field to keep the magnetisation and for a spin flipper behind the polariser, which allows choosing the spin state. The use of remanent SM has the advantage that no strong magnetic fields are required, that may interfere with the sample or the sample environment. Furthermore, it allows switching the magnetisation of the polarisatior and thus the transmitted spin state. In this case a flipper is a surplus.

In the recent years, polarisers of this type have been designed and finally produced on the sputtering plant in our laboratory. Because the polarisers will be used in transmission geometry, material combinations with low absorption have been chosen. The most promising results with respect to the magnetic behaviour were obtained with the system Fe/Si. Several magnetically remanent supermirror coatings were produced. Of these the following two examples are already in use:

- The V-shaped white-beam transmission polariser installed in 2002 in the first collimator tube of SANS-I gives polarisations of 96% (Lambda= 4.7 Angstrom) to 98% (Lambda > 6 Angstrom).

- A prototype spin analyser for the neutron reflectometer and diffractometer Morpheus at SINQ consists of a Si-wafer, coated on both sides with a Fe/Si SM (m =3 with 599 layers). This waver is mounted inside the gap of a small electromagnet which provides the guide field and allows to switch the magnetisation. For this device the polarisation efficiencies are 92% < P (T) < 95% and 95% < P (R) < 98% (H=15Oe).

Informazioni correlate


Jochen STAHN, (Scientist)
Tel.: +41-563102518
Fax: +41-563102939