Development, fabrication, and metrology of the electro-optical breadboard model for the reflection grating array of the XMM Grating Spectrometer

A prototype array consisting of eight diffraction gratings has been fabricated for the XMM Reflection Grating Spectrometer. A component of the full spectrometer is an array of approximately 200 diffraction gratings. The diffraction gratings were produced using lightweight silicon carbide substrates and a replication technique. The prototype array was developed and assembled using the same tolerances as the flight arrays which have typical tolerances of 3 micrometers in translation and sub-arc seconds in rotation. The metrology applied during inspection and assembly included precision linear measurements, full aperture figure measurements, and angular interferometry.