Francium sources and traps for fundamental interaction studies

摘要: Francium is one of the best candidates for atomic parity nonconservation (APNC) and search permanent electric dipole moments (EDMs). APNC measurements test weak force between electrons nucleons at very low momentum transfers. They also represent a unique way to detect nucleon-nucleon interactions. EDMs are instead related time-reversal symmetry. Preliminary these fundamental precision studies in spectroscopy development magneto-optical traps (MOT), which partially compensate lack stable Fr isotopes. At LNL Legnaro, francium produced by fusion 100-MeV 18O with 197Au thick target, followed evaporation neutrons from compound nucleus. diffuses inside hot target (1200 K) surface ionized injection 3 keV an electrostatic beamline. Typically, we produce 1×106 (210Fr ions)/s primary flux 1.5×1012 particles/s. We have studied yields as function beam energy, intensity, temperature. Information on efficiency bulk diffusion, desorption ionization deduced. The then enters Dryfilm-coated cell, where it neutralized heated yttrium plate. escape time neutral (diffusion + desorption) approximately 20 s 950 K, measured dedicated setup. In MOT, use 6 orthogonal Ti:sapphire laser beams main pumping transition stabilized diode repumper. Fluorescence trapped atoms observed cooled CCD camera, order reach noise levels stray light equivalent 50 atoms. Systematic tests being done improve trapping efficiency. plan further develop LNL; parallel, will study EDM techniques systematics alkalis Pisa, Siena, Ferrara.