We have constructed a Zeemanshift Optical Trap (ZOT) for neutral cesium atoms within a sealed cryostat cooled to 4.2K. The low residual background pressure of these temperatures, plus low velocities and masses of the background molecules (mostly He and H{sub 2}), leads to an exceptionally long holding time for trapped Cs atoms in the ZOT. In our initial attempts we measured trap holding times {approximately}5-10 minutes, but increasing this to several hours should be possible. Our latest experimental results will be presented. Long trap holding times may be useful for achieving a Bose condensed gas via evaporative cooling, since thermal relaxation times are fairly long and background gas collisions are therefore important. We are also beginning experiments to trap atoms with superconducting coils inside the cryostat. Our initial aim is to construct microscopic neutral atom traps and other structures with large magnetic field gradients (as high as 10{sup 8} G/cm), where the {triangledown}({rvec {mu}}{center_dot}{rvec B}) force is much greater than has been realized in previous trapping geometries.
We describe techniques for creating long-lived magneto-optical and magnetostatic traps for neutral atoms. These traps exist in a sealed cryogenic environment with a temperature near 4 K, where the background gas pressure can be extremely low. To date we have observed cesium magneto-optical traps with background-limited lifetimes in excess of 1 h, and magnetostatic traps with lifetimes of nearly 10 min. From these observations we use the known He-Cs van der Waals collision cross section to infer typical background gas pressures in our apparatus below 4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}12}$ Torr. With hardware improvements we expect this pressure can be made much lower, extending the magnetostatic-trap lifetimes one to two orders of magnitude. Furthermore, with a cryogenic system one can use superconducting magnets and SQUID detectors to trap and to nondestructively sense spin-polarized atoms. With superconducting microstructures one can achieve very large magnetic-field gradients and curvatures, as high as \ensuremath{\sim}
106 G/cm and \ensuremath{\sim}
109 G/
cm2, respectively, for use in magnetic and magneto-optical traps.
A cryogenic system for the trapping and cooling of neutral atoms is described. The system uses superconducting coils inside a trapping chamber cooled to liquid helium temperatures. The cryogenic nature of the system allows the production of extremely long-lived traps at high field gradients and curvatures. At the highest field gradients, evidence for discrete jumps in the trap fluorescence is presented; these jumps are shown to be due to single atoms entering and leaving the trap. The stability of high field gradient traps is studied, and a newly identified loss mechanism, stochastic diffusion, is shown to be the dominant loss mechanism for such traps. Finally, evidence for evaporative cooling of cesium is presented, and an upper bound to a cross section critical to the evaporation process is obtained.