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High-performance Apparatus for Bose-Einstein Condensation of Rubidium

High-performance Apparatus for Bose-Einstein Condensation of Rubidium. MIT/Harvard Center for Ultracold Atoms ( CUA ) , Research Laboratory of Electronics and Department of Physics, Massachusetts Institute of Technology,. Yoshio Torii Erik Streed Micah Boyd Gretchen Campbell

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High-performance Apparatus for Bose-Einstein Condensation of Rubidium

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  1. High-performance Apparatus for Bose-Einstein Condensation of Rubidium MIT/Harvard Center for Ultracold Atoms (CUA), Research Laboratory of Electronics and Department of Physics, Massachusetts Institute of Technology, Yoshio Torii Erik Streed Micah Boyd Gretchen Campbell Pavel Gorelik Dominik Schneble David Pritchard Wolfgang Ketterle

  2. Abstract We have developed a high-performance apparatus for producing Bose-Einstein condensates (BEC) of 87Rb atoms. It features a Zeeman slower that delivers up to 1011 slowed atoms per second into the main UHV (< 10-11 torr) chamber where the BECs are created. For the slowing and trapping light, we built a stable diode-laser-based optical system, including a high-power tapered amplifier. With this apparatus we can collect 1010 atoms in the MOT within 2 s and create BECs containing 4 x 106 atoms in the F = 1, mF = -1 ground state every 25 s. This is, to our knowledge, the largest number ever achieved for the Rb BECs and about one order of magnitude larger than obtained with conventional double-MOT loading schemes

  3. The Rb Team (uppre row) Dominik Schneble Micah Boyd, Yoshio Torii. (lower row) David Pritchard, Gretchen Campbell, Wolfgang Ketterle, Erik Streed. (not pictured) Pavel Gorelik

  4. The whole apparatus

  5. Vapor pressure of the Alkali

  6. Na Oven (BECII@MIT)

  7. Rb Oven at Orsay F= 4 x 1011 thermal atoms/s From D-thesis of Bruno Desruelle, Orsay (1999)

  8. Rb oven at MIT The end of the oven (Rb ampoule, elbow, and nozzle) is heated to 100-150 degC to produce , whereas the cold cup is cooled to -40 degC to catch the atoms which are not collimated.

  9. Rb Oven and Zeeman Slower The Zeeman coil consists of three segments, each of which carries a current of 5A, 10A, and 30A respectively (from left to right), forming a increasing field profile.

  10. Magnetic field profile of the Zeeman slower Atomic beam direction • The magnetic field profile of the Zeeman slower. The maximum field is 270 G, which corresponds to a capture velocity of 325 m/s (if we assume the final velocity of slowed atoms to be 30 m/s). In the actual experiment we add a bias field of 180 G to the profile field to avoid optical pumping out of the cycling transition.

  11. Acceleration profile of the Zeeman slower • The acceleration profile of the Zeeman slower. a0 = 0.94 x 105 m/s2 is the deceleration of atoms illuminated by a resonant laser light with a intensity of 10 mW/cm2 (six time the saturation intensity of 1.64mW/cm2). The design goal was to keep the deceleration below 70 % of this maximum value.

  12. Velocity distribution of the slowed atomic beam (a) (b) Absorption spectra (a) and corresponding velocity distributions (b)of slowed (pink) and unslowed (purple) atomic beams at a oven temperature of 170 deg C. The flux of slowed (unslowed) atoms is 1.5 x 1011 (2 x 1012) atoms/s. In the figure you can see that most of the atoms with a velocity below 300 m/s are slowed to a final velocity of 30 m/s.

  13. The flux of Zeeman Slowed atoms

  14. Loading profile of the MOT Loading profiles of the MOT at different oven temperatures. At T = 150 deg C, the initial loading rate is 5.7 x 1010 atoms/s, which is close to the independently measured atomic flux of 6.7 x 1010 atoms/s at the same oven temperature. With this flux, the number of atoms in the MOT saturates at 4 x 1010 atoms within 2 s. The diameter (FWHM) and total power of the MOT beams are 2 cm and 60mW.

  15. Optical Setup

  16. TA-100

  17. Optical Setup

  18. Electronics

  19. Computer Control

  20. n = 1.20 MHz n = 1.14 MHz n = 1.08 MHz T  Tc = 600 nK N0 = 4 x 106 Phase Transition of 87Rb atoms Time-of-flight absorption images of magnetically trapped 87Rb atoms after 20-s evaporative cooling (upper row), and their cross sectional profiles (lower row). The final evaporation frequency is shown in each image. BEC phase transition occurred at a temperature of 600 nK. A pure condensate contains 4 x 106 Rb atoms.

  21. Properties of our Rb BEC • MOT Loading Time : 5 s (oven @110 degC) • # of atoms in the MOT : 1010 • Magnetic Trap : Cloverleaf (nr=180 Hz , nz =10 Hz) • # of atoms in the Magnetic Trap : 3 x 109 • Atomic state in the Magnetic Trap : F = 1, mF = -1 • Evaporation time : 15 s • Transition Temp. : 600 nK • # of atoms in the condensate : 4 x 106 • Duty cycle : 25 s

  22. I.I. Rabi PhD Norman Ramsey PhD Dan Kleppner PhD PhD PhD Under- graduate Dave Pritchard RandyHulet Bill Phillips PhD Postdoc Eric Cornell Wolfgang Ketterle Carl Wieman

  23. Hour distribution Distribution of the times when data images were takenduring one year between 2/98-1/99

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