A 30-cm objective grating for far-UV astronomy: theoretical study and laboratory tests.

Area of Science:

• Astronomy
• Astrophysics
• Spectroscopy

Background:

• Faint astronomical sources require high-resolution spectroscopy in the EUV and far-UV ranges.
• Existing spectroscopic instruments may have limitations in sensitivity or resolution for these targets.

Purpose of the Study:

• To theoretically design and experimentally validate an objective grating for high-resolution EUV/UV spectroscopy.
• To assess the performance of the grating in terms of resolving power, effective area, and scattered light.

Main Methods:

• Theoretical calculations were performed to determine the feasibility and geometrical parameters of an aspheric grating blank.
• A large-sized grating was manufactured and tested in a vacuum environment.
• The grating was coupled with a photon-counting detector for performance evaluation.

Main Results:

• The theoretical design demonstrated the feasibility of using an aspheric grating blank.
• Experimental calibration confirmed the grating's capabilities.
• A resolving power of 3 x 10^4 was achieved.
• A total equivalent effective area of approximately 5-10 cm^2 was obtained.
• A very low scattered light level, 10^-4 to 10^-5 of the peak value, was measured.

Conclusions:

• The developed objective grating is suitable for high-resolution spectroscopy of faint astronomical sources in the EUV and far-UV.
• The grating offers a promising combination of high resolving power, significant effective area, and low scattered light.