Progress in the production of polarized ³He in Jülich

The implementation in Jülich of ³He spin filters for neutrons has progressed substantially. Apparatus for polarization via metastable ³He atoms in an RF-excited plasma has been constructed and polarization of ³He above 60% has been achieved. The compressors now in construction have been designed with the major goal of bringing of all components containing polarized gas as close as possible, thereby, minimizing the length of connecting lines which otherwise contribute excessively to polarization losses on account of their unfavorable ratio of surface to volume. The compressors are the result of a cooperative effort between groups at HMI (Berlin) and IFF (Jülich). For the spin-exchange method we are working on a new approach, namely, the use of potassium instead of the standard choice, rubidium, as the alkali metal. We expect a much higher polarization of the ³He nuclei due to the much higher efficiency of K-³He spin transfer. In addition, we plan tests of filter cells including two separate chambers. One chamber is where the ³He is continuously optically polarized while the filter is in the neutron beam while the other chamber is the actual neutron spin filter. In this way, we can achieve a better environment for each of these vital functions. The transfer of the polarization will be by diffusion and convection.