Development of an ultra-compact inline transmission grating spectrograph for extreme ultraviolet wavelengths

In this contribution the design, realization, and characterization of a transmission grating spectrograph (TGS) designed for spectral characterization and monitoring tasks at extreme-ultraviolet (EUV) wavelengths are presented. The overall dimensions of the EUV-TGS have been minimized to allow for easy integration in existing beamlines and setups while maintaining sub-Ångström spectral resolution. The main module (length = 40 mm) of the realized EUV-TGS consists of a spectral and a spatial filter and a high-resolution phase-shifting transmission grating with a grating structure periodicity of 80 nm. For spectral characterization and monitoring of a plasma-based EUV radiation source, a two-dimensional detector is positioned in close proximity to the main module. The realized spectrograph prototype can be moved in and out of the beam path, and therefore does not affect spot profiling and general beam alignment tasks. The structural and optical design and performance measurements of the EUV-TGS are presented, demonstrating that this ultra-compact spectrograph can be easily integrated into EUV setups that will benefit from an inline diagnostic option.