Accumulative atom detection by magneto-optical trap for near-field optical funnel

We use a magneto-optical trap as an integrating counter for descending cold atoms. In the case of cold Rb-87 atoms with an initial mean temperature of 9 muK, 60% of the total number of 2.6 x 10(7) are captured after a 26-cm free-fall and trapped for a long time of 270s. From the capture efficiency and the decay time, the minimum detectable flux intensity of a cold Rb-87 atomic beam is estimated to be 2 x 10(5) atom/cm(2)-s. The atom-counting system is used for detection and evaluation of a cold atomic beam produced out of a near-field optical funnel.