Evaporative Cooling

Huang Wu, Christopher J. Foot

We have simulated the evaporative cooling of trapped atoms using a very efficient method originally introduced for the study of molecular gas dynamics. This straightforward and intuitive method allows the dynamics of the evaporative cooling process to be studied and requires fewer simplifications and assumptions than other methods. In particular, the method is not restricted to distributions close to equilibrium and therefore it can model accurately rapid forced evaporative cooling, which is an important technique for cooling trapped atoms. We present the results of simulations for forced evaporative cooling in one, two and three dimensions.

Huang Wu, Christopher J. Foot

We have simulated the evaporative cooling of trapped atoms using a very efficient method originally introduced for the study of molecular gas dynamics. This straightforward and intuitive method allows the dynamics of the evaporative cooling process to be studied and requires fewer simplifications and assumptions than other methods. In particular, the method is not restricted to distributions close to equilibrium and therefore it can model accurately rapid forced evaporative cooling, which is an important technique for cooling trapped atoms. We present the results of simulations for forced evaporative cooling in one, two and three dimensions.

José Tito Mendonça, Hugo Terças

William D. Phillips

Yosuke Takasu, Takeshi Fukuhara, Masaaki Kitagawa +2 more

Evaporative cooling of ultracold Yb atoms near the quantum-degenerate regime was experimentally studied. Three bosons of 170 Yb, 172 Yb, 176 Yb and two fermions of 171 Yb and 173 Yb were evaporatively cooled in a crossed far-off resonant trap (FORT). We observed that 170 Yb and 172 Yb were not concentrated into the crossed region. We found that, in the cases of 176 Yb atoms, atoms were concentrated well into the crossed region. The following evaporative cooling in the crossed region, however, did not work well. We performed the simultaneous trapping and sympathetic cooling in the crossed FORT by use of 172 Yb-174Yb, 174 Yb- 176 Yb, 172 Yb- 176 Yb, and 171 Yb- 174 Yb pairs. We observed that evaporative cooling worked well. This result shows that we succeeded in the enhancement of the atom collision rate. Especially, by use of 174 Yb- 176 Yb mixture, we obtained cold 176 Yb whose phase space density was 0.02. We observed a large atom loss, which limited the further sympathetic evaporative cooling. We also evaporatively cooled 174 Yb in a 1D optical lattice. Evaporative cooling worked very well because the atoms were initially trapped at a high density. After evaporative cooling, we obtained very cold atoms, and T/T F was estimated to be 1.2.