  The Simons Observatory (SO) will be a cosmic microwave background (CMB)
survey experiment with three small-aperture telescopes and one large-aperture
telescope, which will observe from the Atacama Desert in Chile. In total, SO
will field over 60,000 transition-edge sensor (TES) bolometers in six spectral
bands centered between 27 and 280 GHz in order to achieve the sensitivity
necessary to measure or constrain numerous cosmological quantities, as outlined
in The Simons Observatory Collaboration et al. (2019). The 6~m Large Aperture
Telescope (LAT), which will target the smaller angular scales of the CMB,
utilizes a cryogenic receiver (LATR) designed to house up to 13 individual
optics tubes. Each optics tube is comprised of three silicon lenses, IR
blocking filters, and three dual-polarization, dichroic TES detector wafers.
The scientific objectives of the SO project require these optics tubes to
achieve high-throughput optical performance while maintaining exquisite control
of systematic effects. We describe the integration and testing program for the
SO LATR optics tubes that will verify the design and assembly of the optics
tubes before they are shipped to the SO site and installed in the LATR
cryostat. The program includes a quick turn-around test cryostat that is used
to cool single optics tubes and validate the cryogenic performance and detector
readout assembly. We discuss the optical design specifications the optics tubes
must meet to be deployed on sky and the suite of optical test equipment that is
prepared to measure these requirements.
