Analysis of higher harmonic contamination with a modified approach using a grating analyser

Area of Science:

• Physics
• Synchrotron Radiation Science
• Spectroscopy

Background:

• Toroidal grating monochromators (TGMs) are essential for generating monochromatic soft x-ray beams.
• Accurate quantification of higher harmonic contributions is critical for spectral purity.
• Conventional methods for estimating harmonic contamination can be inaccurate due to overlapping diffraction orders.

Purpose of the Study:

• To develop and validate a modified approach for calculating harmonic contamination in TGM soft x-ray spectra.
• To accurately quantify harmonic content in the 50-360 Å wavelength range.
• To assess the impact of harmonic contamination on spectral analysis and filter characterization.

Main Methods:

• Analysis of soft x-ray spectra from the Indus-1 synchrotron source TGM.
• Utilizing a 1200 l/mm diffraction grating for spectral dispersion.
• Implementing a modified method to subtract overlapping higher-order contributions from the first-order peak.

Main Results:

• Harmonic contamination is <15% in the 90-180 Å range and increases to 6%-60% between 150-260 Å.
• Harmonic contamination is significantly low below 90 Å due to the Indus-1 critical wavelength of 61 Å.
• The modified method's results align well with multilayer reflectivity data analysis.

Conclusions:

• The proposed modified approach provides accurate harmonic contamination assessment for TGM spectra.
• Understanding harmonic content is vital for precise spectral analysis and applications like filter transmission fitting.
• The study contributes to improved data reliability in soft x-ray spectroscopy.