Endcap-type Paul trap for precision spectroscopy and studies of ion-crystal dynamics

We present the design and fabrication of an endcap-type Paul trap. The trap is designed for studies with Ca+ and Yb+. The design, fabrication process, and characterization are presented in detail, with a focus on trapping a single compensated ion at the rf node. A custom-built imaging system of NA = 0.14 and magnification of ≈22× performs close to the diffraction limit and resolves multi-ion clusters. Controlled ion loading and characterization of the trap are performed using 40Ca+. The experimentally determined quadrupole coefficient of the trap is ≈0.3, which is very close to the design value. The relative frequency shift along the spectroscopy beam due to excess micromotion is at the level of 3.5 × 10−18 for 40Ca+. Applications of this trap encompass single-ion-based optical frequency standards, tests of fundamental physics, the study of mesoscopic Coulomb clusters, and the controlled interaction of a single ion with co-trapped atoms.