Realization of Bose-Einstein condensation in a rubidium vapor using a simple double magneto-optical trap

Since the first experimental demonstration of Bose-Einstein condensation (BEC) in an alkali-metal vapor, this subject has been attracting remarkable interests in the physics society. Hundreds of theoretical works concerning this subject have been reported so far. However, the number of reports about BEC experiments is much less than that of the theoretical works. This is because only a few experimental groups have succeeded in realizing BEC due to the experimental complexity and difficulties. The first step to create BEC in alkali-metal vapor is to collect a large number of atoms (/spl sim/-10/sup 9/) in an ultrahigh vacuum (/spl sim/10/sup 11/ torr). Recently, a double magneto-optical trap (MOT) system has been utilized for the first step. In this system, the atoms are first captured in a MOT from a vapor, and then transferred through a thin tube to the second MOT in an ultrahigh vacuum. To transfer the atoms, a pushing beam and a magnetic field are usually required to guide the atoms along the transfer tube. In the paper we report a simple double MOT system which uses neither a push beam nor a magnetic field to transfer the atoms. The atoms are transferred just by gravity. We can collect up to 2 x 10/sup 9/ rubidium atoms in the ultrahigh-vacuum MOT with this system and can achieve the BEC.