Responsivity calibration of the LoWEUS spectrometer

Area of Science:

• Plasma Physics
• Atomic Spectroscopy
• Instrument Calibration

Background:

• Accurate plasma diagnostics are crucial for fusion energy research.
• The Long-Wavelength Extreme Ultraviolet Spectrometer (LoWEUS) requires in situ calibration for reliable operation.
• The Lithium Tokamak Experiment (LTX) provides a suitable environment for such calibrations.

Purpose of the Study:

• To perform an in situ calibration of the relative responsivity function of the LoWEUS instrument.
• To assess the accuracy of the CHIANTI atomic database for oxygen emission lines in a tokamak plasma.
• To quantify the spectral responsivity variations across the 120-300 Å range.

Main Methods:

• In situ calibration using naturally occurring oxygen spectral lines within the LTX plasma.
• Comparison of measured spectral line intensities with theoretical predictions from the CHIANTI database.
• Utilizing a 3rd-degree polynomial fit to characterize the relative responsivity function.

Main Results:

• A relative responsivity function for LoWEUS was successfully determined.
• Discrepancies between measured and predicted relative line intensities were quantified.
• Spectrometer responsivity was found to vary by approximately a factor of 30 across the 120-300 Å wavelength range.

Conclusions:

• The in situ calibration provides a critical correction factor for LoWEUS measurements.
• The results highlight the importance of instrument-specific calibration in spectroscopic diagnostics.
• The findings contribute to more accurate plasma characterization in fusion devices like LTX.