X-Spec: A multi-object, trans-millimeter-wave spectrometer for CCAT

X-Spec is a multi-beam, R=400-700 survey spectrometer covering 190-520 GHz under development for CCAT. It measure the bright atomic fine-structure and molecular rotational transitions that cool galaxies´ interstellar gas, in particular, the 158 μm rest-frame [CII] transition which is accessible from z=9.5 to z=3.5, With the wide bandwidth and multi-object capability, X-Spec/CCAT will be more powerful than ALMA for redshift-blind galaxy surveys and tomographic intensity mapping. X-Spec uses SuperSpec filterbank spectrometer technology with TiN KIDs. Because the density of sources is small, galaxy follow-up will be most efficient with a front-end steering unit which we have prototyped. Our baseline instrument concept has 84 steered beams arrayed over the 1 degree CCAT field, each beam couples to 4 chips (2 bands × 2 polarizations) each chip with ~500 detectors, making a total of ~170,000 KIDs in the full instrument.