Each 6” wafer contains: 4 2k×4k, 1 2k×2k, & 8 512×1k

Follows SNAP model:• Foundry performs first 8 steps on 650 m high resistivity wafers (10 kohm-cm)• LBNL has them thinned to 250 m and performs last 3 steps Wafers Delivered to Fermilab:16 Engineering grade 250 m 9 Control wafers: 650 mExpect 5 Science Grade wafers in Feb. 06

CCD Fabrication

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Brenna Flaugher, Fermilab, and Tim Abbott, CTIO, for the Dark Energy Survey Collaboration:Fermilab: J. Annis, H. T. Diehl, S. Dodelson, J. Estrada, B. Flaugher, J. Frieman, S. Kent, H. Lin, P. Limon, K. W. Merritt, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, D. Tucker, W. Wester University of Illinois at Urbana-Champaign: C. Beldica, R. Brunner, I. Karliner, J. Mohr, R. Plante, P. Ricker, M. Selen, J. Thaler University of Chicago: J. Carlstrom, S. Dodelson, J. Frieman, M. Gladders, W. Hu, S. Kent, R. Kessler, E. Sheldon, R. Wechsler Lawrence Berkeley National Lab: N. Roe, C. Bebek, M. Levi, S. Perlmutter University of Michigan: R. Bernstein, B. Bigelow, M. Campbell, D. Gerdes, A. Evrard, W. Lorenzon, T. McKay, M. Schubnell, G. Tarle, M. Tecchio NOAO/CTIO: T. Abbott, C. Miller, C. Smith, N. Suntzeff, A. Walker CSIC/Institut d'Estudis Espacials de Catalunya (Barcelona): F. Castander, P. Fosalba, E. Gaztañaga, J. Miralda-Escude Institut de Fisica d'Altes Energies (Barcelona): E. Fernández, M. Martínez CIEMAT (Madrid): C. Mana, M. Molla, E. Sanchez, J. Garcia-Bellido University College London: O. Lahav, D. Brooks, P. Doel, M. Barlow, S. Bridle, S. Viti, J. Weller University of Cambridge: G. Efstathiou, R. McMahon, W. Sutherland University of Edinburgh: J. Peacock University of Portsmouth: R. Crittenden, R. Nichol, W. Percival University of Sussex: A. Liddle, K. Romer

The Dark Energy Survey Instrument, DECamThe Dark Energy Survey will measure w, the

dark energy equation of state, using 4 complementary techniques:

I. Cluster Counts II. Weak Lensing III. Baryon Acoustic Oscillations IV. Supernovae

Each measurement will individually constrain w, the dark energy equation of state, and the combined constraints will place tight limits on w and its time dependence. DES will give a factor of 3-5 improvement in the DETF Figure of Merit, exceeding the DETF recommendations for a Stage III project.White Papers submitted to Dark Energy Task Force: Dark Energy Survey astro-ph/0510346, Theoretical & Computational Challenges: astro-ph/0510194,5

Combined Filter and Shutter mechanisms between C3 and C4. Filter changer will hold 8 filters.

NOAO Announcement of Opportunity:

Offered an allocation of 525 nights on the existing Blanco 4m Telescope at CTIO during 2009-2015 in exchange for a new wide field instrument.In response, the DES collaboration proposes to build: a new 3 sq. deg camera and prime focus cage, a data management system to process 300 GB/night and produce a public archive 1 yr after data collected.

Survey Definition Measure photometric redshifts of ~ 30 k galaxy clusters and 300 Million galaxies out to redshift of 1.3 Survey 5000 deg2 overlapping with the South Pole Telescope SZ survey and SDSS stripe 82 for calibration 40 deg2 repeated for the Supernovae search

Photometric Redshifts• Measure relative flux in four filters griz to track the 4000 A break• Estimate individual galaxy redshifts with accuracy (z) < 0.1 (~0.02 for clusters)• Precision is sufficient for Dark Energy probes, provided error distributions well measured.• Good detector response in z band filter needed to reach z>1

Elliptical Galaxy Spectrum

DECam / Mosaic II QE comparison

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LBNL Design: (Holland, S. et al. IEEE Trans. Elec. Dev., 50, 225 (2003))

• fully depleted, 250 m thick• backside illuminated• p-channel on n-type• 15 m pixels, 0.27”/pixel• QE> 50% in z-band (825-1100nm)•Read noise < 10 e- @ 250 kpix/sec•Readout time ~17sec

DES CCDs

CCD Readout

• CCD readout system is based on the Monsoon system developed by NOAO. • DES modifications include higher density video boards (12 channel) and a simplified Clock Board • Will be housed in 3 thermally controlled crates:

constant interior for stable electrical performanceexterior temp will track ambient night temp to avoid thermal plumes

DES Prime Focus Cage

Hexapod supportscorrector and CCD vessel. Provides focus and lateral adjustments

Custom vacuum feed through board

DES Focal Plane62 2k×4k Image CCDs 8 2k×k2 CCDs for guiding, focus and lateral alignment

DES CCD vessel• LN2 Cooling system• 12 copper straps connect internal LN2 to focal plane support plate• Bi-pod support for focal plane support plate• Last corrector element serves as window of the CCD vessel• Corrector barrel supports CCD vessel,• Corrector and CCD vessel move together for focus and alignment

Survey Image System Process IntegrationDES will build a new mountain top software system to control the image acquisition and communicate with the new telescope control system, the CCD readout and the Data Management system

CCD Packaging and characterization(see poster by Tom Diehl)

Fermilab has packaged 75 devices in picture-frame and 4-side buttable pedestal packages. The latter fits in the focal plane support plate.

NOAO Community use

Outside DES observing periods, DECam will be available to NOAO community observers in the same classical mode as Mosaic II, through the NOAO proposal review mechanism and with the investigator present at the telescope.

It is a design requirement that DECam should not perform any less efficiently than Mosaic II, in many respects it will perform substantially better (but, N.B., DECam does not incorporate an atmospheric dispersion corrector and non-sidereal tracking will be unguided). The design maintains f/8 secondary capability. DECam will accommodate 8 filters. Normal DES complement will be g, r, i, z & Y with 3 positions available for other filters as they become available.

Non-DES data will pass through the same data management system as DES data for removal of instrument signature, photometric and astrometric calibration. Raw and pipeline-processed data will be archived by NOAO/DPP and by DES.

2.2 deg. FOV Corrector (see poster by S. Kent)

5 fused silica elements, 2 aspheric surfacesLargest element C1 ~ 950 mm diameterLenses mounted in Invar cells with radial High Density Polyethylene (HDPE) spacers sized to compensate for the CTE difference between the lens and the cell and flexure to compensate for the CTE difference between the barrel and the cells. • Lens cells mount to surfaces in corrector

barrel • Two piece steel construction: Conical section support C1• Center barrel section support C2, C3, C4 and the filter/shutter housing• Reinforcing tubes around the filter-shutter system keeping the deflections of C1 and the focal plane to < 25μm.• Initial feedback from optical sensitivity analysis indicates the design is sufficiently stiff.

Dewarwindow

C1

C2 C3 C4