  We study the dynamical evolution of cold atoms in crossed optical dipole trap
theoretically and experimentally. The atomic transport process is accompanied
by two competitive kinds of physical mechanics, atomic loading and atomic loss.
The loading process normally is negligible in the evaporative cooling
experiment on the ground, while it is significant in the preparation of
ultra-cold atoms in the space station. Normally, the atomic loading process is
much weaker than the atomic loss process, and the atomic number in the center
region of the trap decreases monotonically, as reported in previous research.
However, when the atomic loading process is comparable to the atomic loss
process, the atomic number in the center region of the trap will initially
increase to a maximum value and then slowly decrease, and we have observed the
phenomenon first. The increase of atomic number in the center region of the
trap shows the presence of the loading process, and this will be significant
especially under microgravity conditions. We build a theoretical model to
analyze the competitive relationship, which coincides with the experimental
results well. Furthermore, we have also given the predicted evolutionary
behaviors under different conditions. This research provides a solid foundation
for further understanding of the atomic transport process in traps. The
analysis of loading process is of significant importance for the preparation of
ultra-cold atoms in a crossed optical dipole trap under microgravity
conditions.
