SWCam Project Status October 3, 2012 Gordon Stacey 1

Instrument Development Plan Call made from the CCAT Project Office for proposals to design first light instruments for CCAT in the fall of 2011. Proposals due on February 17, 2012 The idea is to bring designs up to the level appropriate for a preliminary design review by July of 2013 Subject to approval, instruments must be ready for a late 2017 deployment. Total study period budget was targeted at ~ $1.3 million. 30 April 2012 CCAT Board Meeting – Toronto, Canada

Evolution of Development Plan Four Proposals submitted to the Project Office SWCam – short wavelength camera LWCam – long wavelength camera X-Spec – direct detection spectrometer CHAI – heterodyne spectrometer Plan was to down-select from these to fit within the tight instrument development budget. Recommendations of the Project Office were presented to the CCAT Board in April 2012 After much conversation, it was decided to accept all four proposals Deemed too early for down-select Budget cap raised, but requests were made for trimmings Actual development cycle had been reduced from 18 months to about 15 Thought process for final selection includes down-select made at PDR, with likely assignment of “first light” and “second light status” 30 April 2012 CCAT Board Meeting – Toronto, Canada

CCAT Board Meeting – Toronto, Canada SWCam: As Proposed Primary Observing bands: 350 μm, 450 μm and possibly 200 μm 7 sub-arrays, each sub-array 88x88 pixels Pixel size base-lined at 1 mm at f/#-2.86  pix = /D at 350 m  each sub-camera captures a 4.4’4.4’ (square) FoV Total 54,208 pixels Total equivalent FoV = 13.1’ diameter Technology: MKID arrays, with TES backup 30 April 2012 CCAT Board Meeting – Toronto, Canada

SWCam Optical Layout Focal plane split into sub-cameras: Keeps off-axis aberrations acceptable Minimizes issues with windows/fore-optics Opens up real estate for focal planes “Solves” field curvature problem

SWCam Optical Layout Seven sub-cameras, each with 7744 pixels Seven sets of optics – silicon baseline with HDPE backup Six identical, with central exception Closed cycle refrigerators

SWCam Detectors Microwave kinetic inductance detectors (MKIDS) TiN based absorber- resonator Lab demonstration at 200 um with low background “MAKO” demonstration camera to deployed on the CSO in late 2012 Backup Technology is TES-based bolometers.

Evolution Over the Summer Going in premise: We wish to build an observatory that is very versatile. The science cases often involve observations with more than one instrument. With a 1 FoV, we can envision simultaneous operation of two instuments, e.g. SWCam and LWCam Fig. 3. Simulated 4 hour exposures using ATACamera on SPT at 350 (left) and 850 (right) m. The 5 circled sources are > 5  detections at 850 m that are not detected at 350 m – these are the high redshift galaxies that we seek. There are 85 - 350 m drop-outs in the image.

CCAT Image Plane Field of View is 2.8 m in diameter Focal plane is very curved SWCam LWCam

First Step: Detailed Optical Modeling We had picked an f/# = pixel size plate scale to: Be on the sweet spot with point source detection limit ~ 0.8 to 1.6 f/# Compromise between mapping speed (which asks for a larger pixel size) and beam size (which asks for a limits pixel size) Also, larger pixel scale makes it easier to be background limited. Pixel size in units of f/#

Off-Axis Performance for SWCam Focused on even Meniscus/Plano-Convex configuration as proposal with even aspheric surfaces Tried tilting and displacing lenses Found good performance for ~ 0.07 to 0.08 (96 pixel radius) circular FoV cameras both on-axis, and 0.08off-axis However , a 0.16 off-axis camera has a restricted FoV ~ 0.04 Can be improved by tilting focal plane and adding a third lens

Radial Spot Diagrams: Center Camera Circle has diameter of first null of Airy pattern

Radial Spot Diagrams: 0.08  off-Axis Camera Circle has diameter of first null of Airy pattern

Radial Spot Diagrams: 0.16  off-Axis Camera Circle has diameter of first null of Airy pattern

Ensquared Energy: on-Axis Camera –Radial Cut

Ensquared Energy: 0.08 deg. Off-Axis Camera

Ensquared Energy: 0.16 deg. Off-Axis Camera

On-Axis Camera might grow to 0.038 FoV 0.08 off-axis Camera barely works for 0.07 FoV 0.16 Off-Axis Camera restricted to 0.04 FoV

The Crux SWCam can be made to perform off-axis, but: Will need tilted focal planes and 3 lens system Every camera will need to be different We HAVE to have any 200 um module on-axis LWCam needs to have telecentric optics due to antenna coupled MKIDs Means arrays cannot be tilted, so that despite the longer wavelengths, they are not much more forgiving to off-axis optics

Solutions Make both instruments suffer Switch between SWCam and LWCam using tertiary But… this means non-simultaneous observing Logjam broken by realizing that simultaneous observing doesn’t buy much Time to confusion vastly different  only ~ 10% loss in efficiency due to non-simultaneity But, must tilt dewars significantly

CCAT Board Meeting – Toronto, Canada 30 April 2012 CCAT Board Meeting – Toronto, Canada

CCAT Board Meeting – Toronto, Canada 30 April 2012 CCAT Board Meeting – Toronto, Canada

CCAT Board Meeting – Toronto, Canada 30 April 2012 CCAT Board Meeting – Toronto, Canada

CCAT Board Meeting – Toronto, Canada 30 April 2012 CCAT Board Meeting – Toronto, Canada

New Dewar Parameters At Nasmyth focus, plate scale is 2.78 m/ A 0.08 radius f.o.v. then corresponds to a lens diameter of 22.24 cm – make 25 cm Minimum clearance between lenses =2.5 cm 3 lenses on a line means 3*25+5 = 80 cm 10 cm for shields means 100 cm.

New Camera Parameters A 0.08 = 288”radius  to 96 pixel radius Total pixel count/camera = 7235 if circular array Total for 7 cameras = 5064 Practicalities: Arrays being developed are 27  16 = 432 pixels on 1 mm pitch. 18 arrays per camera fill a nearly circular FoV with 7776 pixels each, or 5443 totol

288” FoV

Near Term Work Finalize optics: Joe Adams 3-6 weeks Finalize dewar design: Steve Parshley Detector progress: Darren Dowell Lens A/R coating: Mike Niemack/Jason Glenn/German Cortes Software including data acquisition and reduction Readout electronics: Ganesh Rajagopalan