A New Intensity Adjustment Technique of Emission Spectral Analysis When Measured at the Upper Limit of the Dynamic Range of Charge-Coupled Devices

Abstract

The article presents a method of mathematical correction to be applied to the results of measuring the intensity of spectral lines using charge-coupled devices (CCDs) in the presence of the blooming effect. This technique is particularly applicable in atomic emission spectroscopy. It enables expansion of the dynamic range of spark emission spectrometers and significantly minimizes the result distortions of the measurements taken in the area of high element concentrations. The authors devised a mathematical model and proposed an algorithm to adjust the measured intensity of analytical lines at the photo detector upper limit, in addition to an algorithm for processing data from the spectra recording system. The proposed mathematical algorithm was integrated into the software for the SPAS-02 and SPAS-05 spark spectrometers produced in Russia, and tested in determining the chemical composition of steels. The findings show that the actual dispersion of the analytical line intensity distribution may exceed the measured dispersion by a factor of 1.5, and their intensities may differ by a factor of 2. This algorithm may be implemented in atomic emission spectrometer software and makes it possible to adjust the calibration curves for a range of high alloying element concentrations when the analytical line intensity is at the upper limit of the CCD dynamic range.

Keywords

• calibration
• charge-coupled image sensors
• impurities
• metrology
• plasma devices
• spectral analysis