PHASE-SPACE DENSITY IN THE MAGNETOOPTICAL TRAP

We present an investigation of the cesium magneto-optical trap, with p articular regard to the best combination of atomic density and tempera ture that can be produced. Conditions in the trap depend on four indep endent parameters: the detuning and intensity of the Light, the gradie nt of the magnetic field, and the number of atoms trapped. We have var ied all these parameters and measured the temperature and density dist ribution of the trapped cloud. Both the nonlinear variation with posit ion of the restoring force and the reabsorption of photons scattered i n the cloud limit the maximum density, and we present an empirical mod el that takes this into account. This in turn limits the density in ph ase space rho (defined as the number of atoms in a box with sides of o ne thermal de Broglie wavelength). We have observed a maximum rho = (1 .5 +/- 0.5) x 10(-5), with a spatial density of about 2 x 10(11) atoms /cm(3).