Optimum transmission for a 3He neutron polarizer

Following recent achievements in polarizing gaseous 3He targets by optical pumping at room temperature, polarized helium-3 is now the most promising polarizer for thermal and epithermal neutrons and should soon compete favorably with existing Heusler polarizing crystals. Because it is gaseous, a degree of freedom exists in such a filter: the pressure of the gas in the cell. This parameter allows a choice to be made in the filter design: for a given polarization of 3He, one is able to increase the pressure, to favor neutron beam polarization, or to stay at relatively low pressure to favor the filterʹs transmission. s paper, we discuss this point in the framework of a classical polarized neutron experiment, and we compare our more general results with the quality factor Q=PT, which is generally taken as standard for such a filter.