Bose-Einstein Condensation in a Tightly Confining dc Magnetic Trap

Bose-Einstein condensation of sodium atoms has been observed in a novel “cloverleaf” trap. This trap combines tight confinement with excellent optical access, using only dc electromagnets. Evaporative cooling in this trap produced condensates of $5\times {10}^6$ atoms, a tenfold improvement over previous results. We measured the condensate fraction and the repulsive mean-field energy, finding agreement with theoretical predictions.