Cryogenics Cryostat Optics Technology Development Maria Salatino Abby

Cryogenics, Cryostat, Optics Technology Development Maria Salatino & Abby Vieregg Argonne-2018: Cosmology with CMB-S 4 1 March 5 2018

PEOPLE WHO CONTRIBUTED TO THE CMB-S 4 CCO WORKING GROUP D. Barkats, B. Benson, S. Bryan, C. Coppi, M. Hasselfield, C. Hill, H. Hui, A. Kusaka, F. T. Matsuda, J. Mc. Mahon, L. Moncelsi, J. Nagy, G. Pisano, J. Ruhl, A. Schillaci, A. Suzuki, K. L. Thompson, Z. Xu 2

THE STARTING POINT: THE CDT REPORT The portion of the CDT strawperson concept related to Cryogenics+Optics • 100 m. K operating temperature w/ dilution refrigerator • Frequency coverage up to 270 GHz band • Two telescope designs: ○ 14 x 0. 5 m aperture, (30 -270)GHz cameras entirely cryogenic ○ 3 x 6 m aperture, (20 -270)GHz cameras cold reimaging optics • Telescope Design ○ 0. 5 m aperture telescopes: refracting (BICEP) or reflecting (ABS); ○ >= 6 m aperture telescopes: Cross-Dragone (SO, QUIET) or Off-set gregorian (Adv. ACT, POLARBEAR 2, SPT-3 G) plus • Polarization modulators required? Informed from Stage-III results 3

STARTING POINT WE USED TO PROCEED WITH TECHNOLOGY DEVELOPMENT PRIORITIZATION • Large Aperture: ○ Three telescopes ○ ~20 optical tubes per telescope • Small Aperture: ○ 14 telescopes ○ 1 optical tube per telescope => ~75 optical tubes for all of CMB-S 4 ○ x 2~4 lenses per tube [150 to 300 lenses!] ○ x 2~? ? metal mesh filters per tube [150 or more filters!] ○ x 0 ~ 1 HWP per tube (Chile, at least) [10’s of HWPs!] ○ x 1 - 2 cryocoolers per receiver [~20 PULSE-TUBES, ~250 k. W] => LOTS of optical elements!! 4

TECHNOLOGY DEVELOPMENT (TD) TOPICS WE INVESTIGATED Category Sub-category TD topic Cryogenics Cryostat Optics 4 K cooling systems Sub-K cooling systems Design Fabrication Testing Performance Modeling Filters Windows Lenses HWP rotators Baffles Optical modeling 5

TOP CCO TECHNOLOGY DEVELOPMENT ITEMS • Sidelobe-related systematics and measurements • Characterization of optical properties of materials at operating temperature • AR production methods and rates • Metal-mesh filter production rate and maximum size • Lens production rate for both lens options (silicon/alumina) • HWP continuous rotation at cryo temp (on going S 3 development) • AR coating on lens and HWP performance/ systematics • Magnetic shielding • Window manufacturing • Cryostat delivery and assembly complexity • Cryogenics m. K: dilution fridge (S 3 dev), Kelvin: PT Coolers Color code: Critical benefits from TD Potentially significant benefits from TD Fairly mature technology (may still benefit from TD) 6

WHERE TO GO FROM HERE ● We still need input on a few topics: baffles, sidelobes, HWP in particular ● So far, we have identified schedule, sensitivity, and systematics impacts on most topics ● Next step: identifying cost impacts ● Tomorrow’s Parallel Session: move toward a reference design of CMB-S 4 for the Decadal CDR ● Wednesday morning: organization of the CCO work after the Argonne meeting. 7