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 sim 500^circC 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 4s4p ^1P₁ and 4s4d ^1D₂ 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.