3He neutron spin filter at ILL

The strongly spin-dependent absorption of neutrons in nuclear spin polarized (3) (H) over right arrow e opens the possibility to polarize neutrons over the full-spectrum of cold, thermal and epithermal neutrons. At ILL a neutron spin filter (NSF) development started which uses the direct optical pumping of metastable He-3 atoms in a He-3 plasma at 1 mbar. At present 0.5 bar 1 of gaseous He-3 can be polarized within 1 h. Subsequent polarization-preserving compression by a two-stage compressor system enables one to prepare NSF cells of about 300 cm(3) volume in the required pressure range of several bars. A remote type of operation based on relaxation times of up to 100 h has been demonstrated in a first survey of experiments. Two representative examples are discussed which demonstrate the high potentiality for many polarized neutron-scattering applications. (C) 1998 Elsevier Science B.V. All rights reserved.