  An imaging refractrometer can be used to describe the properties of a
high-energy density plasma by analyzing the transverse intensity distribution
of a laser beam that has passed through the plasma. The output of the
refractrometer can be directly calibrated in terms of beam deflection angles
using ray transfer matrix analysis. This paper describes a novel way to
calibrate the refractrometer output in terms of the spatial wavenumbers of the
transverse intensity distribution of the laser beam. This is accomplished by
replacing the plasma with a gridded structure that modulates the transverse
intensity of the beam, producing an intensity distribution with a known Fourier
Transform. This calibration technique will generate a one-to-one mapping of
deflection angle to wavenumber and will enable measurement of the size of
Fourier space available to the system. The spectrum of wavenumbers generated
when the laser beam passes through a high-energy density plasma may contain
information about the types of density fluctuation that are present in the
plasma.
