the dipole blockade

Our Experimental Setup

A critical parameter to the experiment is having high Magneto-Optical Trap (MOT) densities in order to obtain good counting statistics.  For this purpose we have assembled a double-MOT system, where the atoms are first collected in a glass cell, and then pushed into a second UHV chamber, where the atoms are collected again.  This also gives us a controllable method with which to change the density of the atomic sample used, and thus measure the blockade effect versus atomic density. The magnetic coils used in the secondary chamber to create the quadrupole field for the MOT are water cooled to allow for high magnetic field gradients necessary for a compressed MOT as is discussed below.  To achieve a diffraction limited focus of the Rydberg excitation laser, gradium lenses have been built into the chamber.  Electrodes have also been built into the chamber to provide the background electric field necessary for observing the dipole blockade effect, and an ionization pulse for detecting the Rydberg atoms on the Microchannel Plate detector.  The blue light used for the Rydberg excitation is from a a 960nm diode laser which goes through a frequency doubling cavity.  The blue laser is locked to a simple pressure-tuned Fabry-Perot interferometer.  The laser is scanned by pushing a bellow in and out which in turn changes the index of refraction of the air inside the Fabry-Perot.  With this locking technique we have can scan the blue laser over 3GHz with a laser line width of 4.5MHz.