1. Cryogenics, Cryostat, Optics Technology Development
Maria Salatino & Abby Vieregg
Argonne-2018:
Cosmology with CMB-S4
March

2. PEOPLE WHO CONTRIBUTED TO THE CMB-S4 CCO WORKING GROUP
D. Barkats, B. Benson, S. Bryan, C. Coppi,
M. Hasselfield, C. Hill, H. Hui, A. Kusaka,
F.T. Matsuda, J. McMahon, L. Moncelsi, J. Nagy,
G. Pisano, J. Ruhl, A. Schillaci, A. Suzuki,
K. L. Thompson, Z. Xu

3. THE STARTING POINT: THE CDT REPORT
The portion of the CDT strawperson concept related to Cryogenics+Optics
100mK operating temperature w/ dilution refrigerator
Frequency coverage up to 270 GHz band
Two telescope designs:
14x 0.5m aperture, (30-270)GHz cameras
entirely cryogenic
3x 6m aperture, (20-270)GHz cameras
cold reimaging optics
Polarization modulators required? Informed from Stage-III results

4. 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-S4
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 cryocoolers per receiver [~20 PULSE-TUBES, ~250kW]
=> LOTS of optical elements!!

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

6. 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 S3 development)
AR coating on lens and HWP performance/ systematics
Magnetic shielding
Window manufacturing
Cryostat delivery and assembly complexity
Cryogenics
mK: dilution fridge (S3 dev), Kelvin: PT Coolers
Color code:
Critical benefits from TD
Potentially significant benefits from TD
Fairly mature technology (may still benefit from TD)

7. 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-S4 for the Decadal CDR
Wednesday morning: organization of the CCO work after the
Argonne meeting.