  Experimental validation is presented for a new type of microwave diagnostic,
first introduced in the theoretical study in M. Usoltceva et al., Rev. Sci.
Instrum. 93, 013502 (2022). A new term is adopted for this technique to
highlight its difference from interferometry: intensity refractometry. The
diagnostic allows measuring electron density, and in this work, it is applied
at the edge of a tokamak. The implementation of this technique at ASDEX
Upgrade, called Microwave Intensity refractometer in the Limiter Shadow (MILS),
provides the first experimental proof of the diagnostic concept. Densities
predicted by MILS are compared to several other diagnostics. The agreement and
discrepancy in various radial regions of the density profile are analyzed and
possible reasons are discussed. A wide density coverage is shown in the example
discharges with densities from 2*10^17 m^-3 to 2*10^19 m^-3 at the limiter
position. In these experiments, the radial location of the measurements varied
from 5 cm in front of the limiter (up to 1 cm inside the separatrix was
measured) to 3 cm in the limiter shadow. Experimental challenges of MILS
operation and data processing are presented.
