Production of a spinpolarized keV Sr+ ion beam by laser-optical pumping

Using a well collimated Sr+ ion beam with very small energy spread in combination with collinear laser-optical pumping, we have obtained a beam with high electron spin polarization. The Sr+ ions were produced with μA intensity by surface ionisation in a point-like hot iridium-plated Ta tube and extraction into a beam guiding system. The 52S1252P12 transition was pumped by circularly polarized laser light (421.6 nm) propagating antiparallel to the ion beam. The laser is actively stabilized to the SP transition by means of a newly developed method. The final electron spin polarisation of the ground state for the most abundant 88Sr+ isotope was measured to be greater than 90%.