Broad bandpass spin polarizers for the ISIS second target station

The broad bandwidth of the ISIS second target station source (planned to be operational in 2008) provides a significant challenge for the production of highly polarized neutron beams. Four of the seven initial instruments are expected to have, or will develop, polarization capability. This is a significant step forward for ISIS where the only instrument currently equipped for routine polarized neutron-scattering measurements is the CRISP reflectometer. Of the initial instruments at the second target station the PolRef reflectometer is possibly the most demanding with an accessible wavelength range of 0.5-16 Å. Here, the development of designs and some initial test measurements for, relatively compact, compound polarizer designs will be discussed. These designs, based on both ³He and polarizing supermirror technology, will allow as much of the PolRef wavelength range as possible, ∼2-16 Å, to be polarized to greater than 95% without unacceptable beam loss.