Production and transport of radioactive francium for magneto-optical trapping

The goal of our experiment is to collect alkali atoms in a magneto-optical trap (MOT) for high-precision spectroscopy and for the study of parity violation in atomic systems. We are focusing on francium isotopes, which are particularly suitable for these purposes. The production of francium is achieved by sending a 100-MeV 18 O beam from the Tandem-XTU accelerator on a thick gold target. The extraction of Fr is enhanced by heating the target to 1200 K and by biasing it at 3 kV. The ions are transported to the magneto-optical trap (MOT) through an 8-m electrostatic beam line. The diagnostic systems for monitoring the beam intensity ( 10 5 ions s) are based on silicon surfacebarrier detectors sensitive to the α particles from Fr decays. Beams of stable Rb can also be used for optimizing the transport and trapping processes. At injection into the MOT cell, the beam is neutralized and released in atomic form by a heated yttrium foil. Details on Fr production, transport and neutralization are presented.