  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.
