Fast and dense magneto-optical traps for strontium

We improve the efficiency of sawtooth-wave adiabatic-passage cooling for strontium atoms in three dimensions and combine it with standard narrow-line laser cooling. With this technique, we create strontium magneto-optical traps with 6×10⁷ bosonic ⁸⁸Sr (1×10⁷ fermionic ⁸⁷Sr) atoms at phase-space densities of 2×10^-3 (1.4×10^-4). Our method is simple to implement and is faster and more robust than traditional cooling methods.