A New Method for Dead Time Calibration and a New Expression for Correction of WDS Intensities for Microanalysis

Area of Science:

• Analytical Chemistry
• Materials Science
• Spectroscopy

Background:

• Accurate quantification in electron probe microanalysis (EPMA) is hindered by detector dead time effects, particularly at high count rates.
• Existing calibration methods may rely on assumptions about picoammeter linearity, a critical parameter in EPMA.

Purpose of the Study:

• To introduce a novel "constant k-ratio" method for calibrating detector dead time in wavelength dispersive spectrometers (WDS).
• To provide improved dead time expressions and best practices for instrument calibration.
• To enable accurate quantitative analysis of major, minor, and trace elements at high beam currents.

Main Methods:

• Measuring k-ratios (intensity ratios) as a function of beam current for specific emission lines.
• Utilizing the principle that k-ratios remain constant with beam current for accurate dead time calibration.
• Simultaneously comparing k-ratios across multiple spectrometers to ensure consensus.

Main Results:

• The "constant k-ratio" method provides accurate dead time calibration without relying on picoammeter linearity.
• The method allows for the evaluation of picoammeter linearity, enhancing EPMA calibration reliability.
• Demonstrated ability to perform quantitative analysis of major, minor, and trace elements with high accuracy and sensitivity.

Conclusions:

• The "constant k-ratio" method offers a robust approach to dead time correction in WDS, crucial for high-accuracy EPMA.
• This method facilitates reliable inter-laboratory comparisons by ensuring k-ratio consensus.
• Improved calibration enables simultaneous analysis of diverse elemental concentrations and supports advanced techniques like X-ray mapping.