surface-electrode ion trap loaded by laser ablation

traps operated at liquid helium temperatures offer many advantages \newline for exploring new physics, such as quantum interactions between ions \newline and superconductors; cooling may also reduce anomalously high ion \newline heating rates currently observed and attributed to surface charge \newline fluctuations. However, cryogenic traps are traditionally \newline experimentally challenging to realize, due to the careful attention \newline required to thermally anchor the trap, and due to the incompatibility \newline of standard high-temperature ion sources with a cryogenic environment. \newline We demonstrate a new approach to these challenges using a millimeter \newline scale printed-circuit board trap with surface electrode geometry, \newline operated in a liquid helium bath cryostat, to trap and cool strontium \newline 88 ions. The planar aspect of this trap simplifies anchoring to the \newline helium baseplate, and provides clear access for loading ions from an \newline ablation plume produced by $<$7 mJ pulses of a Q-switched Nd:YAG laser \newline incident on a Sr/Al alloy target. We are able to load traps with \newline depths as low as 0.7 eV, and with laser cooling we observe small ion \newline crystals with between one and twenty six optically resolved ions, with \newline individual ion lifetimes averaging 2 hours. Initial estimates based on \newline the observed residual gas collision rates are consistent with a vacuum \newline pressure below 10\^{}{\{}-9{\}} torr, and the true pressure is likely much lower.