Direct detection submillimeter spectrometer for CCAT

We present a trade study for a submillimeter direct-detection spectrometer operating at the background limit for the Cornell Caltech Atacama Telescope (CCAT). In this study we compare the classical echelle spectrometer ZEUS with the waveguide grating spectrometer Z-Spec. The science driver for this instrument is spectroscopic investigation of high redshift galaxies as their far-IR fine structure line emission is redshifted into the telluric submillimeter windows. The baseline detector consists of SQUID multiplexed TES bolometers and the ideal spectrometer to detect weak lines from distant extragalactic sources is a grating with a resolution of ~103 and a large bandwidth, covering an entire telluric submillimeter window instantaneously. Since the density of high-z sources on the sky is ~100 within a 10'×10' field of view and a redshift range of Δz~0.2 we also explore multi-object (~50 objects) capability, including articulated mirrors and flexible waveguide fibers.