Magneto-optical trap for thulium atoms

Thulium atoms are trapped in a magneto-optical trap using a strong transition at $410$ nm with a small branching ratio. We trap up to 7×10⁴ atoms at a temperature of $0.8(2)$ mK after deceleration in a $40$-cm-long Zeeman slower. Optical leaks from the cooling cycle influence the lifetime of atoms in the magneto-optical trap which varies between $0.3$ and $1.5$ s in our experiments. The lower limit for the leaking rate from the upper cooling level is measured to be $22(6)$ s^-1. The repumping laser transferring the atomic population out of the $F=3$ hyperfine ground-state sublevel gives a $30%$ increase for the lifetime and the number of atoms in the trap.