Research On Deformation Measurement Technology Of Vacuum Chamber Window In Refractive Index Measurement

The vacuum chamber is one of the important parts of the air refractive index measurement system.The windows on both sides of the vacuum chamber are used to close the vacuum chamber.When measuring the refractive index of air,the deformation of the vacuum chamber window caused by the pressure difference between the vacuum chamber and the outside world cannot be avoided,which will affect the accuracy of the refractive index measurement.Therefore,obtaining the deformation of the vacuum chamber window is the key technical of refractive index measurement.In order to further improve the accuracy of refractive index measurement,this paper verifies the resolution accuracy of the F-P interferometer based on the F-P interference principle,and builds an experimental system that can realize the deformation measurement of the vacuum chamber window,mainly using interference signal measurement and frequency measurement methods.Comparing and analyzing the results obtained by the two measurement methods with the German PTB measurement values,the deformation of the vacuum chamber window is finally obtained.Before carrying out the deformation measurement of the vacuum chamber window experiment,based on the analysis of F-P interference principles with different laser incident angles,a precision verification experiment system based on a scanning F-P interferometer is firstly set up.And apply an audio signal affect to the accuracy verification system.The response of the system is very sensitive and the response signal changes are very significantly.Then,the scanning F-P interferometer is set up to measure the wavelength of the laser beam to be measured.During the experiment,it is found that there is a stable difference between the wavelength value of the standard laser beam and the measurement result which is 0.00431 nm.It is characterized by the difference between the decimal parts of the two laser wavelength values.The experimental results show that F-P interference has the characteristics of high sensitivity and high resolution,can meet the needs of deformation measurement.The F-P etalon is designed,and the deformation measurement system of the vacuum chamber window is set up.The interferometric signal measurement and frequency measurement are used to measure the deformation of the vacuum chamber window.When using interference signal measurement,perform a resolution calibration experiment on the F-P etalon at first,and according to the calibration experiment results,obtain the deformation measurement of the vacuum chamber window.When using frequency signal measurement,use the Double-Pass Optial System and the Beat frequency to get the deformation measurement of the vacuum chamber window.The experimental result is 10 nm.Compared with the PTB measurement result,the measurement result differs by 2 nm.The deformation measurement of the vacuum chamber window is realized,and the system error of the refractive index measurement is reduced.Experiments are performed using a refractive index measurement system based on the Koster prism.The measurement results are compared with the theoretical calculations based on Edlen formula,it is found that there is a difference in the seventh place after the decimal point.Subsequently,the refractive index measurement is corrected,the influence of environmental factors on the measurement results is analyzed and corrected.The refractive index measurement accuracy is maintained at the order of 10^-8.Finally,the influence of the vacuum chamber window deformation on the refractive index measurements is corrected to maintain the refractive index measurement accuracy at the order of 10^-9.