2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16081We consider a possible technique for mode-locking an atom laser, based on the generation of a dark soliton in a ring-shaped Bose-Einstein condensate, with repulsive atomic interactions. The soliton is a kink, with angular momentum per particle equal to \hbar/2. It emerges naturally, when the condensate is stirred at the soliton velocity, and subsequently outcoupled with a periodic Raman pulse-train. The result is a replicating coherent field inside the atom laser. We give a numerical demonstration of the generation and stabilization of the soliton.8 pages, 4 figures, using BoxedEPS macros; email correspondence to huang@mit.eduCondensed Mattertext