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Einstein Polarization Interferometer for Cosmology ( EPIC )

Einstein Polarization Interferometer for Cosmology ( EPIC ). Peter Timbie University of Wisconsin - Madison. Beyond Einstein SLAC May 12-14 2004. EPIC Mission Concept Study Team. CMB Power Spectrum. C Farese et al.(2003). C. POLAR Upper Limit. Z re ~ 30.

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Einstein Polarization Interferometer for Cosmology ( EPIC )

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  1. Einstein Polarization Interferometer for Cosmology(EPIC) Peter Timbie University of Wisconsin - Madison Beyond Einstein SLAC May 12-14 2004

  2. EPIC Mission Concept Study Team

  3. CMB Power Spectrum

  4. C Farese et al.(2003) C POLAR Upper Limit Zre ~ 30 Reionization Peak Josh Gundersen,

  5. CMB Polarization Detections! WMAP TT/10 WMAP TE DASI EE

  6. Experimental Challenges • Sensitivity • Angular resolution • Modulation - spatial “chop” - polarization (Q--U) • Atmosphere • Temperature stability • Instrumental polarization • Antenna sidelobes

  7. Sensitivity of CMB Detector Systems vs Epoch Dicke COBE WMAP Maxipol Planck Penzias & Wilson Inflation Probe

  8. Detectors micromachined Si legs • bolometers are capable of reaching background limit from CMB • cooled to < 100 mK • superconducting transition-edge thermistors (TES) • readout with SQUID multiplexers waveguide x-section Si frame at 100 mK Waveguide-coupled bolometer from MSAM balloon-borne telescope

  9. Angular Resolution PLANCK telescope DASI interferometer

  10. Why use an interferometer for CMB? Systematics! • simple optics – no reflectors, which can polarize light • correlation measurement is stable, measures Stokes U directly on a single detector (no differencing) • instantaneous differencing of sky signals without scanning • angular resolution ~ 2X better than filled dish of same dia • measures both Temp and Polarization anisotropy

  11. Consider rotations: y  x Example: for   /4 Stokes Parameters For a linearly polarized wave, where Stokes parameters are: -additive -coordinate-dependent

  12. The Spinning CorrelationPolarimeter CMB Ground Screens Ex Ey y N  OMT x E Gx Gy 0°, 180° Phase Shifter Multiplier TP-y TP-x

  13. Correlation Polarimeter

  14. Ryle’s Phase-switching Interferometer (1952) Correlation of signal from 2 antennas

  15. 3-Element Interferometer Angular Response Functions

  16. Examples of window functions for a 2-element interferometer. Window Functions 2-element interferometer baselines 64 diameter filled dish

  17. Polarized Foregrounds

  18. EPIC Overview • Goal 1: measure gravitational waves from inflation • Goal 2: measure gravitational lensing of CMB • 4-year mission, observe full sky 2X per year • > 6 frequency bands for foreground removal • Multiple interferometric arrays (>2) at each wavelength for l-space ranges covering l = 2 to >400 • Measures Stokes I, Q, U interferometrically for l > 40, directly for l < 40 • Bolometric (TES) detectors (> 2700) cooled to ~ 50 mK • Multiplexed SQUID readout

  19. The Millimeter-Wave Bolometric Interferometer (MBI) • 8 feedhorns (23 baselines) • 90 GHz (3 mm) • ~1o angular resolution – search for B-mode pol’n • 7o FOV • under construction, first light expected winter 2005 • White Mountain, CA (13,500 ft)

  20. Single-Baseline Test horn antennas beam combiner

  21. EPIC Mission Concept Study Tasks • Sensitivity analysis • Optimize l-space coverage of arrays • Optimize frequency coverage for foregrounds (WMAP, Planck, etc. results are key) • Beam combiner • Phase shifters • Data analysis/simulations of aperture synthesis • Cryogenics

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