We report a novel approach for preparing a Bose–Einstein condensate (BEC) of 87 Rb atoms using an electro-pneumatically driven transfer of atoms into a quadrupole-Ioffe magnetic trap (QUIC trap). More than 5 × atoms from a magneto-optical trap are loaded into a spherical quadrupole trap and then transferred into an Ioffe trap by moving the Ioffe coil towards the center of the quadrupole coil thereby changing the distance between the quadrupole trap center and the Ioffe coil. The transfer efficiency is more than 80%. This approach is different from the conventional approach of loading the atoms into a QUIC trap wherein the spherical quadrupole trap is transformed into a QUIC trap by changing the currents in the quadrupole and the Ioffe coils. The phase space density is then increased by forced rf evaporative cooling to achieve Bose–Einstein condensation of more than 10 5 atoms.
We report a novel approach for preparing a Bose–Einstein condensate (BEC) of 87 Rb atoms using an electro-pneumatically driven transfer of atoms into a quadrupole-Ioffe magnetic trap (QUIC trap). More than 5 × atoms from a magneto-optical trap are loaded into a spherical quadrupole trap and then transferred into an Ioffe trap by moving the Ioffe coil towards the center of the quadrupole coil thereby changing the distance between the quadrupole trap center and the Ioffe coil. The transfer efficiency is more than 80%. This approach is different from the conventional approach of loading the atoms into a QUIC trap wherein the spherical quadrupole trap is transformed into a QUIC trap by changing the currents in the quadrupole and the Ioffe coils. The phase space density is then increased by forced rf evaporative cooling to achieve Bose–Einstein condensation of more than 10 5 atoms.
We demonstrate Bose-Einstein condensation of rubidium atoms in a simple low-power magnetic trap. This trap combines the quadrupole with the Ioffe configuration ~QUIC trap! and consists of just three coils. Magneto-optically trapped Rb atoms are first loaded into the linear trapping potential of a magnetic quadrupole, which is then converted into the parabolic geometry of an Ioffe trap. During this process two spherical quadrupole traps with perpendicular axes merge and the trapped atomic cloud moves close to the magnetic field producing coils, resulting in tight confinement of the atoms while the power dissipation of the trap remains low. The magnetically trapped atoms are cooled to below the phase transition of Bose-Einstein condensation by rf-induced evaporation. @S1050-2947~98!51210-3#
We demonstrate Bose-Einstein condensation of rubidium atoms in a simple low-power magnetic trap. This trap combines the quadrupole with the Ioffe configuration (QUIC trap) and consists of just three coils. Magneto-optically trapped 87Rb atoms are first loaded into the linear trapping potential of a magnetic quadrupole, which is then converted into the parabolic geometry of an Ioffe trap. During this process two spherical quadrupole traps with perpendicular axes merge and the trapped atomic cloud moves close to the magnetic field producing coils, resulting in tight confinement of the atoms while the power dissipation of the trap remains low. The magnetically trapped atoms are cooled to below the phase transition of Bose-Einstein condensation by rf-induced evaporation.
The apparatus and procedure required to generate a pure Bose-Einstein condensate (BEC) consisting of about half a million 87Rb atoms at a temperature of <60 nK with a phase density of >54 is described. The atoms are first laser cooled in a vapour cell magneto-optical trap (MOT) and subsequently transferred to an ultra-low pressure MOT. The atoms are loaded into a QUIC trap consisting of a pair of quadrupole coils and a Ioffe coil that generates a small finite magnetic field at the trap energy minimum to suppress Majorana transitions. Evaporation induced by an RF field lowers the temperature permitting the transition to BEC to be observed by monitoring the free expansion of the atoms after the trapping fields have been switched off.PACS Nos.: 03.75.Fi, 05.30.Jp, 32.80.Pj, 64.60.i
Summary form only given.Since its first observation in 1995, Bose-Einstein condensation (BEC) experiments in dilute gases have been performed with only a few different kinds of magnetic traps. We have performed a BEC experiment with /sup 87/Rb atoms in a Ioffe-Pritchard magnetic potential, which opens up the possibility to study, e.g., Bose-Einstein condensates released in only one dimension. Our trap consists of a clip-like coil, which generates a pure two-dimensional (2D) quadrupole field for radial confinement. The axial confinement is provided by two plane pinch coils inside the clip-coil. These two coils create a bottle field. Two additional Helmholtz coils on the same symmetry axis are used to compensate the homogeneous part of the bottle field. By continuously varying the currents through the coils, the trapping potential can be changed from a 3D spherical harmonic to a 2D linear potential. The change can be done adiabatically or nonadiabatically by switching off the axial confinement slowly, or instantaneously respectively. This opens up the possibility to study 1D nonlinear atom optics. In combination with, e.g., far detuned light sheets, a Fabry-Perot type interferometer for a condensate might be realizable. Our experiments are performed in a vacuum system with two magneto-optical traps, which serves as the source of cold atoms for the magnetic trap. 10/sup 9/ atoms are captured in less than one minute. RF-induced evaporative cooling is used to increase the phase space density of the trapped atomic cloud. The BEC phase transition occurs at a temperature of 550 nK with 10/sup 6/ particles in the trap. Pure condensates with more than 10/sup 5/ atoms were produced.
Since its first observation in 1995, Bose-Einstein condensation (BEC) experiments in dilute gases have been performed with only a few different kinds of magnetic traps. We have performed a BEC experiment with /sup 87/Rb atoms in a Ioffe-Pritchard magnetic potential, which opens up the possibility to study, e.g., Bose-Einstein condensates released in only one dimension. Our trap consists of a clip-like coil, which generates a pure two-dimensional (2D) quadrupole field for radial confinement. The axial confinement is provided by two plane pinch coils inside the clip-coil. These two coils create a bottle field. Two additional Helmholtz coils on the same symmetry axis are used to compensate the homogeneous part of the bottle field. By continuously varying the currents through the coils, the trapping potential can be changed from a 3D spherical harmonic to a 2D linear potential. The change can be done adiabatically or nonadiabatically by switching off the axial confinement slowly, or instantaneously respectively. This opens up the possibility to study 1D nonlinear atom optics. In combination with, e.g., far detuned light sheets, a Fabry-Perot type interferometer for a condensate might be realizable. Our experiments are performed in a vacuum system with two magneto-optical traps, which serves as the source of cold atoms for the magnetic trap. 10/sup 9/ atoms are captured in less than one minute. RF-induced evaporative cooling is used to increase the phase space density of the trapped atomic cloud. The BEC phase transition occurs at a temperature of 550 nK with 10/sup 6/ particles in the trap. Pure condensates with more than 10/sup 5/ atoms were produced.
We have studied the locomotion track of (87)Rb Bose-Einstein condensate during decompressing the trap into the center of the glass cell in a quadrupole-Ioffe configuration trap. In order to change the position of the BEC, the current in the quadrupole coils is reduced while the current in the Ioffe coil keeps constant. Because of the strongly reduced trap frequencies of the moved trap, the BEC considerably sags down due to the gravity. Thus an inflexion point exists in the process of moving BEC. When rubidium atoms go over the inflexion point, they cannot keep in balance under the gravity and the force provided by a magnetic field, and flow downward and towards Ioffe coil. By utilizing this effect, the trapped atoms with the spin state |F = 2,mF = 1>, which are left over in the BEC, can be separated from the BEC of |F = 2,mF = 2> state.