Development of a magnetically shielded compact 3He polarizer

The method of polarizing 3He via metastability exchange optical pumping is well known since the early 1960s. Since then hyperpolarized gases have found manifold applications in fundamental science as well as in medical research. The present polarizer apparatus in Mainz used as central facility is well established and can produce up to three standard liters of gas per hour with a polarization of 60-65 %, sufficient for medical applications. For basic research where higher degrees of polarization are needed one can reach up to 78 % at a production rate of one standard liter per hour. To provide the users with high polarization degrees and big amounts of polarized gas a compact apparatus was designed. Using this compact polarizer as local polarizing facility enables the users to avoid polarization losses during shipping. For the new polarizer several concepts had to be developed to minimize the size while retaining the production rate and polarization degree. There have been efforts in optimizing optics, polarization conserving compression of the gas and homogenization of the magnetic field. By using a closed cylinder of soft magnetic material a relative field gradient of better than ΔB/B<3.8.10-4 cm-1 has been obtained, which is needed to have the desired gradient relaxation time for sufficient polarization. Further results are presented in this talk.