  We have built an atomic microwave power standard based on the electromagnetic
interaction with laser-cooled atoms. The atoms traversed a waveguide
transmission line, and under the effect of the radiation, the internal state
populations underwent a Rabi flopping oscillation. Measurement of the
oscillation frequency allowed the determination of the incident microwave
power. As many of 60 oscillations were observed over a dynamic range of 20 dB
and the standard deviation of the measurements was about 0.02%. The measured
frequency was compared to a calculated one and an agreement of 1.3% with an
uncertainty of 5% (rectangular) was found.
