Each 6” wafer contains: 4 2k×4k, 1 2k × 2k, & × 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  m Expect 5 Science Grade wafers in Feb. 06 CCD Fabrication ) Brenna Flaugher, Fermilab, and Tim Abbott, CTIO, for the Dark Energy Survey Collaboration: The Dark Energy Survey Collaboration is a collaboration of scientists from Fermilab, the University of Illinois at Urbana-Champaign, the University of Chicago, the Lawrence Berkeley National Laboratory, CTIO, University College London, University of Cambridge, University of Edinburgh, University of Portsmouth, Institut d'Estudis Espacials de Catalunya, Institut de Fisica d'Altes Energies, CIEMAT-Madrid, University of Michigan, University of Pennsylvania, University of Sussex and the Brazil-DES Consortium, a consortium of Brazilian scientists from Observatorio Nacional, Centro Brasileiro de Pesquisas Fisicas, Universidade Federal do Rio de Janeiro and Universidade Federal do Rio Grande do Sul. The institutions from the UK and Spain have formed the UK DES Consortium and the DES-Spain Consortium respectively. At this time, the Project Director and the DES MC are considering applications from Argonne National Laboratory and Ohio State University with the expectation that they will be admitted to the DES in the very near future The Dark Energy Survey Instrument, DECam 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 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 sq. deg overlapping with the South Pole Telescope SZ survey and SDSS stripe 82 for calibration  40 sq. deg repeated for the Supernovae search Photometric Redshifts M easure 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 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 ( nm) Read noise < 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. 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 performance  exterior temp will track ambient night temp to avoid thermal plumes DES Prime Focus Cage Hexapod supports corrector and CCD vessel. Provides focus and lateral adjustments Custom vacuum feed through board DES Focal Plane 62 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 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 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. Dewar window C1 C2C3 C4 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/ , Theoretical & Computational Challenges: astro- ph/ ,5