Each 6” wafer contains:four 2k×4k, one 2k×2k,eight 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 thick9 Control wafers: 650 m thickExpect 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:

US Institutions:Fermilab, University of Illinois at Urbana-Champaign, University of Chicago, Lawrence Berkeley National Laboratory, CTIO, University of Michigan, University of Pennsylvania, the Ohio State University

UK-DES Collaboration: University College London, University of Cambridge, University of Edinburgh, University of Portsmouth, University of Sussex

Spain-DES Collaboration: Institut d'Estudis Espacials de Catalunya, Institut de Fisica d'Altes Energies, CIEMAT-Madrid

Brazil-DES Consortium: scientists from Observatorio Nacional, Centro Brasileiro de Pesquisas Fisicas, Universidade Federal do Rio de Janeiro and Universidade Federal do Rio Grande do Sul.

The Dark Energy Survey Instrument, DECam

The 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. The 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 (see poster by T. Shaw)• CCD readout system is based on the Monsoon system developed by NOAO, but customized to meet DES density requirements:• Each video board will have 12 instead of 8 channels.• Each clock board will produce 135 clock signals, instead of 32. This is enough for 9 CCDs.• Will be housed in 3 thermally controlled crates with backplanes split for independent readout of 4 slots (up to 9 CCDs) and 6 slots (up to 18 CCDs)

DES Prime Focus Cage • A Hexapod supports the optical corrector and CCD vessel. Provides focus and lateral adjustments

• F/8 observations and top-end flip capability is maintained

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 (see poster by H. Cease)• 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 Integration (see poster by J. Thaler)DES 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.

With 8 times the sky coverage, near-IR sensitivity, an improved corrector design, better thermal management, faster readout, real-time focus, and active alignment control, DECam is expected to perform significantly better than Mosaic II. (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 surfaces•Largest element C1 ~ 950 mm diameter•Lenses mounted in Invar cells with radial High Density Polyethylene (HDPE) spacers sized to compensate for the CTE difference between the lens and the cell. •Flexures compensate for the CTE difference between the steel barrel and the Invar cells.

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

Dewarwindow

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C2 C3 C4