A permanent-magnet Zeeman slower and magneto-optical trap for calcium atoms for ultracold Rydberg physics

We report the construction and characterization of an experimental setup for producing a cold gas of 40Ca atoms and excite them to high Rydberg states with a resonant three-photon-excitation scheme. The apparatus comprises four stages, each designed in-house. An oven heated to ∼500°C generates an atomic beam that is collimated by a capillary stack. The beam is sent into a passive, permanent-magnet-based Zeeman slower that reduces the atomic velocity to 30 m/s. The slow atoms are captured in a magneto-optical trap (MOT) and cooled to 1.0(3) mK with a trapping time of 16(2) ms. Ground-state atoms in the cold gas are excited to high Rydberg states via resonant excitation through the intermediate 4s4p1P1 and 4s4d1D2 states. The MOT is operated at the center of an electrode stack, which serves to apply continuous and pulsed electric fields and field-ionize the Rydberg atoms for detection. We benchmark our MOT against previous implementations and find its performance consistent with state-of-the-art results in terms of temperature and trapping lifetime. Finally, we demonstrate Rydberg spectroscopy of calcium, confirming the system's suitability for ultracold Rydberg physics experiments.