High accuracy wavelength calibration for a scanning visible spectrometer

Area of Science:

• Spectroscopy
• Plasma Physics
• Optical Engineering

Background:

• Plasma velocity measurements using spectroscopy demand high wavelength accuracy (≤0.2 Å).
• Existing calibration methods often require frequent recalibration, impacting stability and efficiency.

Purpose of the Study:

• To develop an automated, stable calibration for scanning spectrometers.
• To achieve high wavelength accuracy for visible spectrum measurements without recalibration after grating movement.

Main Methods:

• Implemented an automated calibration fitting spectrometer parameters using multiple calibration spectra.
• Utilized a stepping-motor controlled sine drive for grating movement.
• Incorporated a high-resolution optical encoder (0.075 arc sec) on the grating stage.

Main Results:

• Demonstrated wavelength accuracy of approximately 0.25 Å with the automated calibration and sine drive.
• Achieved enhanced precision of approximately 0.005 Å with the addition of the optical encoder.
• Enabled absolute velocity measurements within approximately 0.3 km/s.

Conclusions:

• The developed automated calibration method provides stable, high wavelength accuracy for spectroscopic plasma velocity measurements.
• Precise velocity measurements require monitoring environmental factors (temperature, pressure) and grating temperature to correct refractive index and groove density.