Wavenumber Calibration for an Imaging Refractometer

TL;DR

This paper introduces a new calibration method for an imaging refractometer that maps beam deflections to spatial wavenumbers, enabling detailed analysis of plasma density fluctuations through Fourier space characterization.

Contribution

A novel calibration technique using a gridded structure to relate refractometer output to the spatial wavenumbers of the laser beam.

Findings

Calibration method achieves one-to-one mapping of deflection angle to wavenumber

Enables measurement of Fourier space size in the system

Potential to analyze plasma density fluctuations through wavenumber spectrum

Abstract

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.