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A kilopixel array of TES bolometers for ACT: Development, Testing, and First Light

A kilopixel array of TES bolometers for ACT: Development, Testing, and First Light. ¼ array. Low Temperature Detectors 12, P03 July 26, 2007 M. D. Niemack, Princeton University Y. Zhao, E. Wollack, R. Thornton, E. R. Switzer, D. S. Swetz, S. T.

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A kilopixel array of TES bolometers for ACT: Development, Testing, and First Light

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  1. A kilopixel array of TES bolometers for ACT:Development, Testing, and First Light ¼ array Low Temperature Detectors 12, P03 July 26, 2007 M. D. Niemack, Princeton University Y. Zhao, E. Wollack, R. Thornton, E. R. Switzer, D. S. Swetz, S. T. Staggs, L. Page, O. Stryzak, H. Moseley, T. A. Marriage, M. Limon, J. M. Lau, J. Klein, M. Kaul, N. Jarosik, K. D. Irwin, A. D. Hincks, G. C. Hilton, M. Halpern, J. W. Fowler, R. P. Fisher, R. Dunner, W. B. Doriese, S. R. Dicker, M. J. Devlin, J. Chervenak, B. Burger, E. S. Battistelli, J. Appel, M. Amiri, C. Allen, and A. M. Aboobaker

  2. ACT Science: Observations: Atacama Cosmology Telescope Growth of structure CMB to l~10,000 wwwphy.princeton.edu/act Eqn. of state Cluster (SZ, KSZ X-rays, & optical) Neutrino mass Diffuse SZ Ionization history OV Power spectrum Lensing X-ray Optical Theory Collaboration: NIST CUNY Haverford INAOE Princeton Cardiff Columbia NASA/GSFC U. Toronto Rutgers UBC UPenn U. Catolica U. KwaZulu-Natal UMass U. Pittsburgh

  3. Kilopixel Array Overview • Detector Parameter Selection • Screening and assembly • Dark bolometer measurements • Optical time constants • First light! • Current status

  4. Parameter Selection • Critical Parameters: Noise level, Psat , f3dB • SQUID noise • Time-domain multiplexing aliasing  select low TES resistance so high current noise dominates SQUID noise • Saturation power, Psat • Predicted load at 145 GHz < 2 pW •  saturation power for biasing uniformity and f3dB de Korte, et al. (2003)

  5. Pre-screening and Assembly • Pre-screen mux chips and shunt chips • Assemble components into columns Light • Assemble columns into array Det chip (32 pixels) Shunt chip Nyquist chip Mux chip ¼ filled array thermometer 8x32 bolometer array

  6. Array Assembly and Si Coupling Layer Evanescently coupled Si layer matches bolometer impedance to free space …also protects array …currently being tested Light

  7. Pre-Assembly Column Screening • Test every pixel • V-phi, Tc, I-V, Rshunt, noise • Repairs • Disconnect oscillating and problematic detectors • Short failed SQUIDs • ~90% yield on first ¼ array SRDP Vacuum Ports, Electronics 1 m Dewar Flange 4He Bath Vacuum Can 4He Pot 3He Pot Flex Column (1x32TES) 3 cm

  8. Noise and Nyquist Inductor Selection TES Absorber Si Aliasing Estimate • Compare noise and aliasing estimates pre- and post-Nyquist inductor • Find maximum decrease in aliasing after adding inductor, without causing oscillations Bolometer Model (R. Dunner & T. Marriage)

  9. Optical time constants – CCam prototype • ACT scans in azimuth 5o p2p during observations CCam Light • Chopper wheel measurements • 3 bolometer types follow trend • Consistent f3dBbetween 0.25 – 0.75 * Rn • Drives us to select higher Psat isothermal, no L

  10. First Light! • CCam prototype on ACT • Scanning Obs. of Jupiter Caveats: • Mirror alignment • Non-ideal optics • Ladder • Focus • Plate scale looks good ~38’/mm

  11. Status & Thanks • Completed majority of testing of remaining columns for array • Finishing last MBAC receiver tests • Testing data acquisition with more CCam observations • Aligning mirrors Thank you: Cardiff Univ. for supplying CCam filters A. Dahlen, B. Harrop, T. Essinger-Hileman, K. Martocci, L. Parker, and A. Sederberg for help with detector screening and assembly All other members of the ACT Collaboration

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