Adding Interferometry for CMBPol Peter Timbie University of Wisconsin - Madison
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Adding Interferometry for CMBPol Peter Timbie University of Wisconsin - Madison QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 27 August 2008 CMBPol Technology Workshop 1 Imaging and Interferometry tor a l rre co Visibilites V(u,v) FT Cl Cl l 27 August 2008 FT l CMBPol Technology Workshop 2 Outline Why interferometry? Challenges Beam combination: pairwise vs ‘all-on-one’, multiplying vs adding Guided-wave beam combiner Quasi-optical beam combiner MBI EPIC Interferometer Required technologies (bolometric interferometer) horn antenna arrays OMTs phase modulators Discussion beam combiner/correlator filters bolometers/readout 100 mK cooler 27 August 2008 CMBPol Technology Workshop 3 CMB Interferometers Interferometers for the CMB 27 August 2008 ν (GHz) FOV # ant’s receivers DASI 30 5o 13 HEMT CBI 30 44’ 13 HEMT MINT 150 30’ 4 SIS VSA 30 7o 14 HEMT BIMA 30 6’ 6 HEMT OVRO 30 4’ 9 HEMT T-W 45 5o 2 SIS BAM 90-270 42’ 2 Bolo VLA 5, 8, 16 7’ 27 HEMT SZA 30, 90 10’, 3’ 8 HEMT CMBPol Technology Workshop 4 Why CMB Interferometry? Systematics! • simple optics - forms beams with corrugated horn arrays - symmetric beam patterns, low sidelobes, no mirrors • no off-axis aberrations • Stokes U measured by correlation of Ex and Ey on a single detector (no differencing of detectors) • differences sky signals without scanning • measures power spectrum directly • measures both Temp and Polarization anisotropy • coherent (HEMTs) or incoherent (bolometers) systems possible • angular resolution ~ 2X better than imager of equivalent diameter • CMB polarization first detected with interferometer (DASI) • simple scan strategy - rotate about optical axis, move on to new pixel 27 August 2008 CMBPol Technology Workshop 5 Interferometer beam systematics: example n1 n2 VijU = ∫ dn1 dn2Gix (n1 )G jy (n2 ) Eix (n1 )E jy (n2 ) y i x uij X j U(n1 )e = ∫ 2πiu ij ⋅n 1 dnGix (n)G jy (n)U(n)e δ(n1 − n2 ) i 2πu ij ⋅n So - beam mismatch, distortion, etc. do not couple T into Stokes U visibility measurement. 27 August 2008 CMBPol Technology Workshop 6 Challenges for Interferometry • beam combiner - scalable, low loss • “fringe smearing” from wide bandwidths • simulations 27 August 2008 CMBPol Technology Workshop 7 Beam Combination 1. 2. Pairwise (Michelson): signals are split and combined pairwise • N(N-1)/2 pairs (78 for N = 13, 4950 for N =100) • multiplying correlator (coherent receivers only) a. analog (DASI/CBI) b. digital (most radio interferometers) see Coherent Detectors, C. Lawrence et al. - power? - bandwidth? • adding correlator with bolometers: M. Hattori, Tohoku University Fizeau (Butler): signals from all antennas appear at all detectors • Fizeau approach has lower noise in background-limited case, in low n limit (Zmuidzinas 2003) • Hamilton et al. (astro-ph/0807.0438) compares to imaging • Guided-wave adding interferometer (Butler combiner, Rotman lens) • Quasioptical adding interferometer using a telescope (MBI) 27 August 2008 CMBPol Technology Workshop 8 Ryle’s Adding Interferometer (1952) “visibility” 27 August 2008 CMBPol Technology Workshop 9 Adding interferometer for N > 2 E ⊥1 + E||1 E ⊥ 2 + E||2 E ⊥N + E||N N horns OMTs 2N phase modulators // ⊥ // ⊥ // ⊥ …. beam combiner detectors …. ( E ⊥1 + E||1 + ...E ⊥N + E|| N ) N × ( E ⊥1 + E||1 + ...E ⊥N + E|| N ) ∗ N 2 2 (E ⊥1 + ...E⊥N ) + (E ⊥1 E ||1 + ...E ⊥N E||N ) + (E⊥1 E||2 + ...E⊥1 E||N ) + (E⊥1 E ⊥ 2 + ...E|| E||N ) = N total power single-horn auto-correlation Stokes U visibilities Stokes I visibilities 10 I. Guided-wave beam combiner • Waveguides or planar transmission line • Butler combiners (N inputs and N outputs) • Rotman lens (N inputs, > N outputs) • Losses may restrict to coherent receivers (with gain) 27 August 2008 CMBPol Technology Workshop 11 Rotman Lens interferometer scheme (see poster by R.A. Watson & L. Piccirillo) 2D horn array (HEMTs) Rotman Lens stack Anti-reflection resistive layer φφ φφ Orthogonal cross stack φφ φφ Geometric delays OMTs T Q array Detector array Diode Diode detector φφ Phase switches U Idealised Rotman interferometer scheme showing the input TQU maps and the paths through to the detectors. The signal from each sky element reaches each horn with different geometric delays. OMTs split the signals into different hands of polarization which are then phase switched independently before being input to the first Rotman stack. The column followed by the row stack performs a Fourier transform and the Fourier transform of these detected outputs gives the visibility information. 27 August 2008 CMBPol Technology Workshop 12 The Rotman Lens: Alternative to Butler combiner (Watson & Piccirillo) Antenna ports A C D Du mm yp ort s rt s po Rotman lens (Rotman and Turner 1963) is a planar transmission line implementation of the quasi-optical combiner. D um m y po rts rts po y mm Du D my um B -7π /8 -7π /16 7π /16 -5π /8 7π /8 -5π /16 -3π /8 5π /16 -3π /16 -π/8 5π/8 3π /16 -π/16 3π/8 π/16 π/8 7π /8 7π /16 5π/8 -7π /16 3π/8 5π /16 -7π /8 π/8 3π /16 -5π /16 π/16 -3π /16 -5π /8 -π/16 -3π /8 -π/8 Beam ports HFSS simulation of a Rotman Lens. The relative phase on the outputs is given in different colours for each antenna port. 27 August 2008 It consists of a set of beam and antenna ports either side of a specially shaped parallel plate cavity through which the waves propagate. The design is simple and many inputs and outputs can be easily incorporated, unlike a Butler combiner It can be implemented cheaply in microstrip and using high dielectric constant substrate (εr>10) can reduce size sqrt(εr) (>3). CMBPol Technology Workshop 13 II. Adding interferometer with a quasioptical beam combiner • Millimeter-wave Bolometric Interferometer (MBI) • EPIC Interferometer 27 August 2008 CMBPol Technology Workshop 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 27 August 2008 CMBPol Technology Workshop 15 The Millimeter-Wave Bolometric Interferometer (MBI) Antennas • Fizeau (optical) beam combiner Phase modulators • 4 feedhorns (6 baselines) • 90 GHz (3 mm) • ~1o angular resolution • 7o FOV Liquid nitrogen tank Liquid helium tank Secondary mirror 3 He refrigerator Primary mirror Bolometer unit 27 August 2008 CMBPol Technology Workshop 16 Effect of Phase Shifting Single Baseline Six baselines (Two feeds) (Four feeds) 27 August 2008 CMBPol Technology Workshop 17 MBI Assembly 15 cm 19 spider-web bolos (JPL) 27 August 2008 CMBPol Technology Workshop 18 MBI Team Brown University Greg Tucker, Andrei Korotkov Jaiseung Kim University of Richmond Ted Bunn University of Manchester Lucio Piccirillo Cardiff University Peter Ade, Carolina Calderon National University of Ireland - Maynooth Creidhe O’Sullivan, Gareth Curran University of Wisconsin - Madison Peter Timbie, Amanda Gault Peter Hyland, Siddharth Malu University of Illinois Ben Wandelt UC San Diego Evan Bierman, Brian Keating 27 August 2008 CMBPol Technology Workshop 19 First light at Pine Bluff Observatory Madison, WI March 2008 27 August 2008 CMBPol Technology Workshop 20 MBI interference fringes Tucker et al. SPIE 2008 27 August 2008 CMBPol Technology Workshop 21 Einstein Polarization Interferometer for Cosmology (EPIC) Mission Concept 25 cm at λ = 0.3 cm Corrugated horns OMTs RF phase modulators Fizeau beam combiner Backshort Under Grid (BUG) TES array (NASA/GSFC) 64-element module (1 of 16) Interference fringes measured in focal plane by bolometer array 22 EPIC LEO Mission Concept 250 GHz 90 GHz module (1 of 8) 0.25 m dia 150 GHz 60 GHz 30 GHz 0.9 m 1.75 m dia 23 EPIC LEO Mission Concept • Measure CMB E and B mode polarization over full sky to foreground limit (T/S ~ 0.01) Scaled close-packed corrugated horn arrays: 30-300 GHz ~15o FOV, ~ 1o synthesized beams Total # horns N ~ 1024 (= # modes) x 2 pol’ns Interferometer: signals cross-correlated - between horns: N(N-1)/2 visibilities for small scales Arrays - between 2 polarizations for each horn: “correlation polarimetry” for large scales LHe Dewar Lifetime > 1yr from 900 km Earth orbit (COBE) Spacecraft Bus 27 August 2008 CMBPol Technology Workshop 24 EPIC sensitivity calculation • • • • • • • • • • • each array module has N = 64 antennas, 2 polarizations signal from each antenna spread out over focal plane of 4N = 256 detectors phase-modulated fringe signal meas’d independently by each detector background-limited detectors in focal plane of beam combiner η = 0.5, 20 % BW 4N demodulated signals are then added in quadrature to compute visibility repeat for each of the 2N(2N-2)/2 visibilities (all baselines) add in quadrature signals from other arrays at 90 GHz 1 - year integration over full sky (“Knox” formula) see J. C. Hamilton et al. (astro-ph/0807.0438) - comparison with imager, coherent interferometer - simulation 27 August 2008 CMBPol Technology Workshop 25 EPIC Sensitivity 27 August 2008 CMBPol Technology Workshop 26 Interferometer “Fringe Smearing” • 1-D simulation • diffuse source (CMB) with flat power spectrum • horn aperture D ~ 17λ ~7° FWHM beam QuickTime™ and a decompressor are needed to see this picture. horn spacing D 2D 4D 6D 8D 12D 16D 27 August 2008 CMBPol Technology Workshop 27 Horn Antenna Arrays • need close-packed arrays of ~ 8 x 8 antennas from 30 GHz to 300 GHz • total of 1024 horns for EPIC Interferometer • platelet arrays (see Gundersen and Wollack) • smooth-walled horns (Yassin et al.) 27 August 2008 CMBPol Technology Workshop 28 G. Yassin Easy machining! 29 30 Ortho-mode transducers • separate X/Y linear or R/L circular polarization modes • input: interface to circular horn output • output: interface to phase modulator (waveguide or transmission line) • low-loss (< 0.5 dB) • low cross-coupling (< - 40 dB?) • bandwidth ~ 30% • mass production? 1024 required, bands from 30 GHz - 300 GHz • see ClOVER design, Giampaolo Pisano et al. 27 August 2008 CMBPol Technology Workshop 31 CIOVER OMT • G. Pisano et al. IEEE Micr. and Wireless Comp. Lett. 17(4) 2007 • electroformed copper QuickTime™ and a decompressor are needed to see this picture. • WR10 waveguide band (75-110 GHz) • ms’d return loss -22 dB avg. across band • ms’d isolation -45 dB avg. across band • 100’s req’d for ClOVER 27 August 2008 CMBPol Technology Workshop 32 Phase Modulators • require 2 for each antenna (one per polarization) • input interfaces to OMT output (w’guide or transmission line) • ~ 30% bandwidth • low insertion loss (< 0.5 dB) • low amplitude modulation • step through a phase sequence similar to Walsh function - co-add signals from redundant baselines (Charlassier et al. ‘08) - # steps minimized by having multiple phase angles (Hyland, Follin, & Bunn arXiv:0808.2403v1) • for 8 x 8 array - steps of 360/15 = 24° is optimal - sequence length is 675 steps • switching speed > 100 Hz • waveguide Ferrite Rotation Modulator (FRM) see B. Keating • planar modulators (MEMs and SIS) see A. Kogut 27 August 2008 CMBPol Technology Workshop 33 Ferrite phase shifter performance Gault, Malu, Bierman, Keating, et al. 27 August 2008 CMBPol Technology Workshop 34 Bolometers • filled arrays required to capture all radiation in focal plane • # pixels ~ 4 X Nhorns for each interferometer module • near photon noise limit for -optical efficiency of ~ 12% ( ~ 50% / 4) -bandwidth 30% -CMB background loading • Backshort Under Grid (BUG) arrays for GISMO (λ = 2 mm) - increase 64 pixels → 256 pixels - reduce G - extend to λ = 1 cm - $400K/yr for 3 years • other candidates? 27 August 2008 CMBPol Technology Workshop 35 Adding Interferometer Systems Complete systems are required to test the concept MBI-4 …. MBI/BRAIN Simulations have just become available this year: R.A. Watson & L. Piccirillo (poster) J.-C. Hamilton et al. (2008) ArXiv 0807.0438 27 August 2008 CMBPol Technology Workshop 36 Initial simple simulations of Rotman interferometer (Watson & Piccirillo) TQU HEALpix map PSD1 VL-HR PSD2 VL-VR PSD3 HL-VL PSD4 HL-VR PSD5 HL-HR PSD6 HR-VR The simulation was carried on a 4x4 array shown in figure 4 with a 5o FWHM with a spacing of 20 wavelengths between elements using a HEALpix TQU map generated by synfast using a concordance model. The signal from each HEALpix pixel is traced through all horns through the Rotman stacks to the detectors where the complex sum is made and its contribution detector power determined Geometry of dual polarization elements Correlation pairs for each PSD lock-in The lower panels show the real and imaginary parts of visibilies recovered by the FFT on the different phase switched detector stacks. The stronger unpolarized signals (CMB fluctuations) can be seen on PSD channels 2, 5 and 7 with weaker polarized U visibilities at 10% on PSDs 1,3,4 and 6 37 Sky BRAIN/MBI 10 cm horns 30 K First module for deployment at Dome C, Antarctica 30 K phase shifte rs back horns 60 cm Workshop at APC, Paris, June ‘08 “Bolometric Interferometry for the B-mode Search” 40 cm 30 K 10 cm 300 mK Bolometer array 70 cm Bolometric Radiation INterferometer •France MBI •United States –Astroparticule et Cosmologie (APC), Paris •Brown University –Centre d’Étude Spatiale de Rayonnements (CESR), Toulouse –Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Orsay •University of Wisconsin, Madison –Institut d’Astrophysique Spatiale (IAS), Orsay •University of Richmond •Italy •UC San Diego •University of Illinois –Università di Milano - Bicocca –Università di Roma - La Sapienza •United Kingdom •University of Wales, Cardiff •United Kingdom •University of Manchester –University of Manchester 38 •NUI Maynooth –University of Wales - Cardiff Adding Interferometer Technology Readiness Technology corrugated horn antennas (singles) platelet arrays smooth-wall horn arrays OMT (< 100 GHz) ClOVER OMT (150 GHz?) phase modulator - ferrite (2 state, <150 GHz) - MEMs/SIS (2 state) beam combiner - quasi-optical - guided-wave focal plane bolometer arrays - NTD Ge - Backshort-Under-Grid TES LHe Cryostat Sub-K Cooler: Single-shot ADR 27 August 2008 TRL 9 5 3 9 4/5 Heritage WMAP & COBE QUIET TBD WMAP ClOVER 5 2/3 BICEP & MBI PAPPA 5 2 MBI TBD 8 6 9 9 Planck & Herschel GISMO Spitzer, ISO, Herschel, COBE ASTRO-E2 CMBPol Technology Workshop 39 Summary Why interferometry? Challenges Beam combination: pairwise vs ‘all-on-one’ Guided-wave beam combiner Quasi-optical beam combiner MBI EPIC Interferometer Required technologies (bolometric interferometer) horn antenna arrays OMTs phase modulators beam combiner/correlator filters bolometers/readout 100 mK cooler 27 August 2008 CMBPol Technology Workshop 40
