We have observed evaporative cooling of magnetically trapped sodium atoms. A novel technique, rf induced evaporation, was used to reduce the temperature by a factor of 12 and increase the phase space density by more than 2 orders of magnitude. The elastic collision cross section of cold sodium atoms in the $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ , ${m}_{F}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}1$ hyperfine state was determined to be $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ c ${\mathrm{m}}^{2}$ , which implies a positive value of the scattering length.We have observed evaporative cooling of magnetically trapped sodium atoms. A novel technique, rf induced evaporation, was used to reduce the temperature by a factor of 12 and increase the phase space density by more than 2 orders of magnitude. The elastic collision cross section of cold sodium atoms in the $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$, ${m}_{F}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}1$ hyperfine state was determined to be $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ c${\mathrm{m}}^{2}$, which implies a positive value of the scattering length.

Physical Review LettersJun 26, 1995260 citations

Evaporative Cooling of Trapped Atoms

Wolfgang Ketterle, N. J. van Druten

Advances in atomic, molecular, and optical physicsJan 1, 1996602 citations

Optimized evaporative cooling for sodium Bose-Einstein condensation against three-body loss

Takahiko Shobu, Hironobu Yamaoka, Hiromitsu Imai +2 more

We report on a highly efficient evaporative cooling optimized experimentally. We successfully created sodium Bose-Einstein condensates with 6.4\ifmmode\times\else\texttimes\fi{}10 ${}^{7}$ atoms starting from 6.6\ifmmode\times\else\texttimes\fi{}10 ${}^{9}$ thermal atoms trapped in a magnetic trap by employing a fast linear sweep of radio frequency at the final stage of evaporative cooling so as to overcome the serious three-body losses. The experimental results such as the cooling trajectory and the condensate growth quantitatively agree with the numerical simulations of evaporative cooling on the basis of the kinetic theory of a Bose gas carefully taking into account our specific experimental conditions. We further discuss theoretically a possibility of producing large condensates, more than 10 ${}^{8}$ sodium atoms, by simply increasing the number of initial thermal trapped atoms and the corresponding optimization of evaporative cooling.We report on a highly efficient evaporative cooling optimized experimentally. We successfully created sodium Bose-Einstein condensates with 6.4\ifmmode\times\else\texttimes\fi{}10${}^{7}$ atoms starting from 6.6\ifmmode\times\else\texttimes\fi{}10${}^{9}$ thermal atoms trapped in a magnetic trap by employing a fast linear sweep of radio frequency at the final stage of evaporative cooling so as to overcome the serious three-body losses. The experimental results such as the cooling trajectory and the condensate growth quantitatively agree with the numerical simulations of evaporative cooling on the basis of the kinetic theory of a Bose gas carefully taking into account our specific experimental conditions. We further discuss theoretically a possibility of producing large condensates, more than 10${}^{8}$ sodium atoms, by simply increasing the number of initial thermal trapped atoms and the corresponding optimization of evaporative cooling.

Physical Review ASep 20, 20118 citations

F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1

, ${m}_{F}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}1$ hyperfine state was determined to be $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ c

{\mathrm{m}}^{2}

, which implies a positive value of the scattering length.

We report on a highly efficient evaporative cooling optimized experimentally. We successfully created sodium Bose-Einstein condensates with 6.4\ifmmode\times\else\texttimes\fi{}10

{}^{7}

atoms starting from 6.6\ifmmode\times\else\texttimes\fi{}10

{}^{9}

thermal atoms trapped in a magnetic trap by employing a fast linear sweep of radio frequency at the final stage of evaporative cooling so as to overcome the serious three-body losses. The experimental results such as the cooling trajectory and the condensate growth quantitatively agree with the numerical simulations of evaporative cooling on the basis of the kinetic theory of a Bose gas carefully taking into account our specific experimental conditions. We further discuss theoretically a possibility of producing large condensates, more than 10

{}^{8}

sodium atoms, by simply increasing the number of initial thermal trapped atoms and the corresponding optimization of evaporative cooling.