1 A method for determination of Gaseous Refractivity based onthe

We present a speciic method and its software implementation to determine the refractive index (n) of various gases, analysing the interferometric data of a pressure tunable Fabry-Perot interferometer from visible to VUV region. The principal idea of this method is to apply the Discrete Fourier Transform (DFT) on the data of the light intensity as a function of the gas pressure, in order to determine the total number of interference fringes during the pressure variation. From further analysing the power spectrum of the data we developed a methodology by which we are able to estimate the dispersion of the refractive index. This was achieved by using a unique experimental interferogram obtained with a multiple line spectral emission light source. Simulated and real experimental data have been used to verify the above capabilities. The method has been used to measure the refractivity (n-1), in the VUV region, of the gas radiators of the RICH detectors by analysing the data from the DELPHI refractometer at CERN which is based on a Fabry-Perot interferometer. We present a speciic method and its software implementation to determine the refractive index (n) of various gases, analysing the interferometric data of a pressure tunable Fabry-Perot interferometer from visible to VUV region. The principal idea of this method is to apply the Discrete Fourier Transform (DFT) on the data of the light intensity as a function of the gas pressure, in order to determine the total number of interference fringes during the pressure variation. From further analysing the power spectrum of the data we developed a methodology by which we are able to estimate the dispersion of the refractive index. This was achieved by using a unique experimental interferogram obtained with a multiple line spectral emission light source. Simulated and real experimental data have been used to verify the above capabilities. The method has been used to measure the refractivity (n-1), in the VUV region, of the gas radiators of the RICH detectors by analysing the data from the DELPHI refractometer at CERN which is based on a Fabry-Perot interferometer.