Abstruct-
This paper describes the development of a new type
of microwave power standard based on atomic resonances. An
atomic Rabi frequency is proportional to the magnetic field
strength of the resonant microwave; the proportionality constant
is determined only from fundamental constants and atomic quantum
theory. The microwave field strength that corresponds to microwave
power is thus uniquely determined by the Rabi frequency.
The proportionality constant can thus serve as the basis for a
new microwave power standard. This paper confirmed that the
Rabi frequency of cesium-133 (133Cs) atoms in a rectangular
cell is proportional to the incident microwave field strength. A
rectangular Cs glass cell was developed and inserted into a WR90
waveguide—an industrially practical waveguide that permits the
impedance analysis necessary to measure microwave power. The
microwave field strength in the Cs cell can be adjusted to arbitrary
values proportional to the Rabi frequency. The relative expanded
uncertainties of the effective microwave magnetic field strength
Heff for the coverage factor k = 2, which is typically less than
7%, averaged 4%. The dynamic range of the available Rabi
frequency was 31.9 dB.
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