Bose-Einstein Condensation at Gakushuin University

Last updated on Aug 8, 2000

In the night of 19 July 2000, we achieved BEC with rubidium atoms!

(a) (b)(c)

Absorption images of rubidium atoms taken after 20-ms expansion from a magnetic trap. (a)Thermal cloud with a temperature of about 500nK (just before phase transition). (b)Bimodal structure of thermal cloud and Bose-condensate. (c)pure Bose-condensate. The final rf frequency is (a)1.24MHz, (b)1.23MHz, and (c)1.22MHz. The field of view is 1mm x 1mm.

False color image (optical density) of the above data.

The experimental details are as follows:

atomic species: 87Rb, |F MF> = |2 +2>

loading: double MOT system with novel cw loading

magnetic trap: a cloverleaf magnetic trap (B'=220G/cm, B''=125G/cm2 at I =375A)

loading time: 5 s

initial number of atoms in UHV MOT: 1 x 109

initial number of atoms in magnetic trap: 7 x 108

lifetime of magnetic trap: 90s

evaporation time: 25 s (from 50MHz to around 1.2MHz)

transition temperature: about 500 nK

number of condensed atoms: about 105

total time to create a BEC: about 35s (including loading, adiabatic compression, and evaporative cooling)

(Further details will be appear in this web page in near future)


Some pictures of the experimental apparatus

Whole apparatus

Double MOT system

Upper MOT chamber

Lower MOT glass cell and cloverleaf coil


The work that led to BEC has been advanced by the efforts of:

Kenichi Ito

Ryo Namiki

Students contributing to this work have included:

Katsutoshi Kondo

Yuichi Sasaki

Tsunetoshi Sakano

Soichiro Nakamura

The senior staffs involved in this work are:

Yoshio Torii (research associate)

Takuya Hirano (associate professor)

If you have any comments or questions, please mail to

BEC homepage

hirano-lab top page