Invited Paper-Polarized Ion Sources for Cyclotrons

Since their advent six years ago polarized ion sources have been successfully installed in 15 accelerators of various types around the world, including FF, FM, and isochronous cyclotrons. The advantages of sources over nuclear reactions for providing polarized particles are (1) greater intensity, (2) control of polarization mode and direction, and (3) freedom from background radiation from the primary target. Currently operating polarized ion sources can produce several tenth-microamperes of up to 80% polarized protons or 100% polarized deuterons and negative ion currents a thousand times smaller. Basic principles and recent developments in polarized ion source design and technology will be reviewed, with particular reference to the problems peculiar to cyclotrons. Some of the major contributions to polarized ion source development have been made at cyclotrons laboratories, first at CERN and later at Saclay, where the powerful adiabatic passage process for inducing hyperfine transitions has been extensively developed. More recently, the achievement of axial injection at Birmingham and the successful acceleration of polarized particles in the isochronous cyclotrons there and at Saclay indicate that polarized ion sources installed on this latest range of cyclotrons could provide the most powerful tool yet for examining nuclear polarization phenomena in the intermediate energy region.