Doppler Cooled Ions in a Compact, Reconfigurable Penning Trap

Abstract

We report the design and experimental demonstration of a compact, reconfigurable Penning ion trap constructed with rare-earth permanent magnets placed outside of a trap vacuum enclosure. We describe the first observation of Doppler laser cooling of ions in a permanent magnet Penning trap. We detail a method for quantifying and optimizing the trap magnetic field uniformity in situ using a thermal beam of neutral ${}^{40}$Ca precursor atoms. Doppler laser cooling of ${}^{40}$Ca${}^{+}$ is carried out at 0.65~T, and side-view images of trapped ion fluorescence show crystalline order for both two- and three-dimensional arrays. Measured ${}^{40}$Ca${}^{+}$ trap frequencies confirm the magnetic field characterization with neutral ${}^{40}$Ca. The compact trap described here enables a variety of cold ion experiments with low size, weight, power, and cost requirements relative to traditional electromagnet-based Penning traps.

5 pages, 4 figures, supplemental material