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

Transcription

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

2 Brown University Greg Tucker Jaiseung Kim Andrei Korotkov Jerry Vinokurov MBI Collaboration University of Wisconsin Madison Peter Timbie Amanda Gault Peter Hyland Siddharth Malu University of California San Diego Brian Keating Evan Bierman University of Richmond Ted Bunn University of Illinois Ben Wandelt Cardiff University Peter Ade Phil Mauskopf Manchester Lucio Piccirillo Giampaolo Pisano N.U.Ireland, Maynooth Créidhe O Sullivan This research is supported by grants from: NASA, Wisconsin Space Grant Consortium, Rhode Island Space Grant

3 Imaging vs Interferometry correlator Visibilities V(u,v) FT FT

4 CMB Interferometers ν (GHz) FOV # ant s receivers DASI 30 5 o 13 HEMT CBI HEMT MINT SIS VSA 30 7 o 14 HEMT BIMA HEMT OVRO HEMT

5 CMB Interferometers ν (GHz) FOV # ant s receivers DASI 30 5 o 13 HEMT CBI HEMT MINT SIS VSA 30 7 o 14 HEMT BIMA HEMT OVRO HEMT Need to extend to more frequencies & more receivers (modes)

6 Why use an interferometer for CMB? (1) Systematics Simple optics view sky directly with arrays of corrugated horns - Symmetric beam patterns - Low sidelobes - No polarization or emission from mirrors Field-of-view determined by beamsize of array elements (no beam distortions off-axis)

7 Why use an interferometer for CMB? (2) Stability of correlation measurement; Stokes U measured directly on single detectors (no differencing of detectors) Instantaneous differencing of sky signals without scanning Power spectrum measured directly Both temperature and polarization power spectra measured Coherent or incoherent receivers/detectors possible Angular resolution

8 Beam Systematics bad worse worst Approach Q U (E B) ΔT Q,U (ΔT E,B) T Q,U (T E,B) Power difference cross-talk mismatched beam mismatched pointing gain errors Interfere linear polarizations cross-talk cross-talk cross-polar beam OK! Interfere circular polarizations gain errors cross-talk cross-polar beam OK!

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

10 Ryle s Adding Interferometer (1952) phase switch detector Lock-in recorder

11 Beam Combination - Michelson: signals are split and combined pairwise (M.Hattori, Tohoku University) - Fizeau: signals from all antennas appear at all detectors (MBI) - Fizeau approach has lower noise in background-limited case, in low n limit, Zmuidzinas (2003) - Quasioptical beam combiner using a telescope (guided wave Butler combiner also possible)

12 Quasioptical Beam Combiner

13 7 o FOV 1 o resolution MBI-4 5 cm Bolometers

14 CCD Interferometry of Venus

15 MBI-16 With OMTs Polarizations from single feed horns also interfere (imaging mode) sensitive to the large angular scales.

16 The Millimeter-Wave Bolometric Interferometer (MBI-4) Four feedhorns (six baselines) 90 GHz (3 mm) Fizeau (optical) beam combiner ~1 o angular resolution search for B-mode polarization 7 o FOV Input unit Liquid nitrogen tank Liquid helium tank Secondary mirror 3 He refrigerator Primary mirror Bolometer unit

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

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

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20 1 m MBI-4 Instrument

21 The MBI mount in action

22 The MBI mount in action

23 3 He refrigerator MBI-4 Instrument 15 cm Bolometers from JPL

24 MBI-4 Bolometers For future MBI? ACBAR bolometers from JPL BUG Backshort Under Grid from GSFC

25 Pine Bluff Observatory Moving the calibration tower to PBO

26 MBI Antenna Pine Bluff Observatory Far-field map of primary beam, fringes & sidelobes System passband System scattering matrix Overmoded 8 mm circular pipe (6 db loss) 12 m RF sweeper GHz Tilt tower 12 m MBI

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30 To do: Integrate on the sky Measure sensitivity Add OMTs to test imaging mode