Transient compression of a MOT and high intensity fluorescent imaging of optically thick clouds of atoms

We describe a way to compress Cs atoms in a MOT to temporarily reach spatia l densities of 10(12) atoms/cm(3). The method entails starting off with mor e atoms than will ultimately be used, and then changing parameters so the a toms rush toward the trap center. For some time during the compression, col lisional losses at the center are more than offset by newly arriving atoms. We monitor the compression with a high intensity fluorescent technique tha t is well suited to providing accurate number and density measurements for large dimension clouds that are very optically thick. (C) 2000 Published by Elsevier Science B.V. All rights reserved.