Enhanced Magnetic Trap Loading for Atomic Strontium
We investigate a technique to improve loading of atomic strontium into a magnetic trap by using a Magneto-Optical Trap (MOT) depumping laser on the 688 nm, 3P1 -3S1, transition. Strontium degenerate gas experiments typically use a 1S0 - 1P1 transition MOT to load a magnetic trap via a slow (~1:150,000) leak to the metastable 3P2 state. The leaked atoms populate the 3P2 and 3P1 states in a 1:2 ratio, which allows for accelerated magnetic trap loading by pumping 3P1 atoms into 3P2 via 3S1. We stabilize the 688 nm laser to within one transition linewidth using slow feedback from a wavemeter. The depumping laser increases atom number in the magnetic trap, and subsequent cooling stages, by up to 70% for the bosonic isotopes and up to 30% for the fermionic isotope of strontium. We discuss the performance of the depumping strategy with respect to laser detuning, intensity, and beam size; and compare our results to a 1D rate equation model of the system.