The 3He filter project at HMI Berlin

Nuclear-spin polarised gaseous He-3 serves as a polarising filter for neutron beams. It can be used for a broad range of neutron wavelengths and also for divergent beams, since the polarisation mechanism is decoupled from the beam optics. This method is the most promising technique for polarising neutron beams at spallation sources. Hence the realisation of such a flexible tool for neutron scattering is a focal point in the instrumental development programme at the HMI Berlin. The method we favour to polarise He-3 is that of optical pumping via the metastable 2(3)S(1) and 2(3)P states. The He-3 station will include a unit for the polarisation of the Helium, a compressor to produce sufficient number densities of He atoms and filter cells to store the polarised gas. An overview on the status of the project at the HMI will be given. (C) 1999 Elsevier Science B.V. All rights reserved.