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

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 slowed atoms per second into the main UHV (< 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 atoms in the MOT within 2 s and create BECs containing 4 x 10 6 atoms in the F = 1, m F = -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

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

The whole apparatus

Vapor pressure of the Alkali

Na Oven

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

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

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.

Magnetic field profile of the Zeeman slower 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. Atomic beam direction

Acceleration profile of the Zeeman slower The acceleration profile of the Zeeman slower. a 0 = 0.94 x 10 5 m/s 2 is the deceleration of atoms illuminated by a resonant laser light with a intensity of 10 mW/cm 2 (six time the saturation intensity of 1.64mW/cm 2 ). The design goal was to keep the deceleration below 70 % of this maximum value.

Velocity distribution of the slowed atomic beam 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 (2 x ) 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. (a)(b)

The flux of Zeeman Slowed atoms

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 atoms/s, which is close to the independently measured atomic flux of 6.7 x atoms/s at the same oven temperature. With this flux, the number of atoms in the MOT saturates at 4 x atoms within 2 s. The diameter (FWHM) and total power of the MOT beams are 2 cm and 60mW.

Optical Setup

TA-100

Optical Setup

Electronics

Computer Control

Phase Transition of 87Rb atoms = 1.20 MHz  = 1.14 MHz = 1.08 MHz  c = 600 nK    x   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 10 6 Rb atoms.

Properties of our Rb BEC MOT Loading Time : 5 s degC) # of atoms in the MOT : Magnetic Trap : Cloverleaf (   =180 Hz, z =10 Hz) # of atoms in the Magnetic Trap : 3 x 10 9 Atomic state in the Magnetic Trap : F = 1, m F = -1 Evaporation time : 15 s Transition Temp. : 600 nK # of atoms in the condensate : 4 x 10 6 Duty cycle : 25 s

Dan Kleppner Dave Pritchard Eric CornellCarl WiemanWolfgang Ketterle Bill Phillips PhD Postdoc Under- graduate PhD Randy Hulet PhD Norman Ramsey PhD I.I. Rabi PhD

Hour distribution Distribution of the times when data images were taken during one year between 2/98-1/99