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The Millimeter-Wave Bolometric Interferometer (MBI)

The Millimeter-Wave Bolometric Interferometer (MBI). Greg Tucker Brown University. MBI Collaboration. Brown University Greg Tucker Jaiseung Kim Andrei Korotkov Chin Lin Wong University of California San Diego Brian Keating Evan Bierman. University of Wisconsin – Madison

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The Millimeter-Wave Bolometric Interferometer (MBI)

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  1. The Millimeter-Wave Bolometric Interferometer (MBI) Greg Tucker Brown University

  2. MBI Collaboration Brown University Greg Tucker Jaiseung Kim Andrei Korotkov Chin Lin Wong University of California San Diego Brian Keating Evan Bierman University of Wisconsin – Madison Peter Timbie Seth Bruch Amanda Gault Peter Hyland Siddharth Malu Cardiff University Lucio Piccirillo Peter Ade Carolina Calderon Phil Mauskopf • University of Richmond • Ted Bunn N.U.I. Maynooth J. Anthony Murphy Créidhe O’Sullivan LLNL Shafinaz Ali Thisresearchis supported by grants from: NASA, WisconsinSpaceGrant Consortium, RhodeIsland Space Grant

  3. CMB Interferometers Need to extend to more frequencies & more receivers (modes)

  4. Why Use an Interferometer for the CMB? - Angular resolution - better than filled dish of same diameter - Field-of-view determined by beamsize of array elements (no beam distortions off-axis) - Measures power spectrum directly - Measures both Temperature and Polarization anisotropy - Coherent or incoherent receivers/detectors possible

  5. Challenges for Interferometry Correlator/beam combiner - scalable, low loss Phase modulation - scalable, low loss Image reconstruction - for foreground removal Bandwidth/coherence tradeoff

  6. Field-of-View for Interferometer Path length difference: θB Coherence length: λ2/∆λ θFOV ≤ (λ/∆λ)(λ/B). e.g. 20% spectral bandwidth sets the maximum baseline to about 5 times the diameter of each antenna Subdivision of band solves problem

  7. Some Systematics in Polarization Instruments • Cross-polar beam response • Beam ellipticity • Sidelobes • Polarization angle • Relative pointing • Calibration - relative and drift • Optics temperature drift Hu, Hedman & Zaldarriaga (2003) TFCR (2005)

  8. Systematics bad worse worst

  9. Systematic Effects

  10. Adding Interferometer - MBI is an adding interferometer (DASI and CBI use coherent receivers to form multiplying interferometers) For polarization we want to measure E E x y A phase shifter is required to obtain the “cross-term”

  11. Beam Combination • Michelson: signals are split and combined pairwise • (M.Hattori, Tohoku University) • Fizeau: signals from all antennas appear at all detectors • Fizeau approach has lower noise in background-limited case, • in low n limit, Zmuidzinas (2003) • We have been pursuing two Fizeau approaches: • Guided waves - Butler combiner (waveguide or microstrip) • Quasioptical combiner using a telescope

  12. Waveguide Beam Combiner

  13. Single-Baseline Test of MBI Input Horns He3 Refrigerator Beam combiner

  14. Quasioptical Beam Combiner Cryostat Feed horn antennas Phase Shifters 45° CW twist rectangular wave guide 45º CCW twist rectangular wave guide Bolometer Array Parabolic mirror

  15. Effect of Phase Shifting Six baselines (Four feeds) Single Baseline (Two feeds)

  16. MBI Schematic - Four feedhorns (6 baselines) - 90 GHz (3 mm) - ~1o angular resolution – search for B-mode polarization - 8o FOV - Sequential phase switching with waveguide Faraday rotators

  17.               Scheme with quasi-optical beam combination Windows 300K thermal filter #1 77K thermal filter #2 77K blocking filter (8cm-1LPE) Feed horns 77K thermal filter #3 4K blocking filter (5cm-1LPE) Circular-to-rectangular WG adapter Phase shifter ±45deg WG twists Rectangular-to-circular WG adapter Horns illuminating primary mirror HDPE lenses Yoshinaga filters Secondary mirror 4K blocking filter (4cm-1LPE) Primary mirror 300mK edge defining filter #1 300mK edge defining filter #2 HDPE lenses Bolometer unit

  18. Bolometers More sensitive above 90 GHz than HEMT amplifiers Spiderweb bolometers (JPL) Polarizations selected by single mode waveguides (not PSBs) Array of 16 bolometers in the focal plane Bolometers cooled to 340 mK using 3He refrigerator

  19. Status of MBI MBI cryostat and He3 MBI pointing platform Pine Bluff Observatory

  20. Status of MBI Fizeau combiner Butler combiner

  21. Status of MBI Phase shifters from UCSD Filters from Cardiff Bolometers from JPL

  22. Characteristics and Sensitivity(Fizeau)

  23. Why Use an Interferometer for the CMB? • - Simple optics - can form beams with arrays of corrugated horn antennas • Symmetric beam patterns • Low sidelobes • - No polarization or emission from mirrors • - Correlation measurement is stable, measures Stokes U directly on a single detector (no differencing of detectors) • - Instantaneous differencing of sky signals without scanning

  24. Status of MBI

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