He-3 neutron spin-filter

Neutron spin-filters (NSF) using gaseous polarized He-3 offer the possibili ty to polarize neutrons over the full spectrum of cold, thermal and hot neu trons. This report gives an account of the present status of the NSF develo pment programme at ILL. The polarization technique is based on direct optic al pumping of metastable He-3 atoms in a low pressure discharge cell with a subsequent polarization-preserving mechanical compression of the gas up to several atmospheres, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nu clear spin relaxation times of order 100 h. A first survey of their use und er experimental conditions is given. (C) 1999 Elsevier Science B.V. All rig hts reserved.