1-3 July, 2009The Path to CMBPol Bolometric Adding Interferometry: MBI & QUBIC Peter Timbie University of Wisconsin - Madison

CMB Interferometers  (GHz) FOV# ant’sreceivers DASI305o5o 13HEMT CBI3044’13HEMT MINT15030’4SIS VSA307o7o 14HEMT BIMA306’6HEMT OVRO304’9HEMT T-W455o5o 2SIS BAM ’2Bolo VLA5, 8, 167’27HEMT SZA30, 9010’, 3’8HEMT

Why CMB Interferometry? Systematics! simple optics - beams can be formed with corrugated horn arrays - symmetric beam patterns, low sidelobes, no mirrors - no off-axis aberrations correlates E x and E y on a single detector to measure Stokes U (no differencing of detectors) differences sky signals (measures visibilities) without scanning simple observing strategy - measure U and Q on each field by rotating about optical axis measures Temp and Polarization power spectra directly angular resolution ~ 2X better than imager of equivalent diameter coherent (HEMTs) or incoherent (bolometers) systems possible

Interferometer Beam Systematics j n1n1 n2n2 u ij i Beam mismatch, distortion, etc. do not couple T into Stokes U visibility. [E.F. Bunn PRD 75, (2007)] y x X Interferometers measure visibilities:

Beam Combination for Large N 1.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) - power? - bandwidth? 2.Fizeau (Butler): signals from all antennas appear at all detectors Guided-wave adding interferometer (Butler combiner, Rotman lens) Quasioptical adding interferometer using a telescope (MBI, EPIC-I, QUBIC)

Ryle’s Adding Interferometer (1952) “visibility”

Adding Interferometer for Many Horns OMTs total power single-horn auto-correlation Stokes U visibilities N horns 2 N phase modulators beam combiner detectors Stokes I visibilities  //   ….

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

Interference pattern 1 horn 1 baseline total signal The interference pattern is imaged on the bolometer array Each pixel measures a linear combination of all visibilities with different phase shifts Sequences of phase shift modulations allow reconstruction of all visibilities in optimal way In a close-packed array, many baselines are redundant - these need to be ‘co-added’ [ Charlassier et al., arxiv: , A&A 497 (2009) 963] [Hyland et al., arXiv : v1, MNRAS 393 (2009) 531]

Both systems have: 256 horns 1  angular resolution background-limited bolos 25 % bandwidth Interferometer: co-adds ‘redundant’ visibilities has 1000 detectors Sensitivity - comparison to imager [Hamilton et al., arxiv: , A&A (2008) ] updated with bandwidth and accurate NET calculations] data pts from simulation

The Millimeter-Wave Bolometric Interferometer (MBI-4) Fizeau (optical) beam combiner 4 feedhorns (6 baselines) 90 GHz (3 mm) ~1 o angular resolution 7 o FOV Antennas Liquid nitrogen tank Liquid helium tank Secondary mirror 3 He refrigerator Primary mirror Bolometer unit Phase modulators

MBI Assembly 19 spider-web bolos (JPL) (PSB’s not required) 15 cm

MBI Team Brown UniversityGreg Tucker, Andrei Korotkov Jaiseung Kim University of RichmondTed Bunn University of ManchesterLucio Piccirillo Cardiff UniversityPeter Ade, Carolina Calderon National University of Ireland - MaynoothCreidhe O’Sullivan, Gareth Curran University of Wisconsin - MadisonPeter Timbie, Amanda Gault Peter Hyland, Siddharth Malu University of IllinoisBen Wandelt UC San DiegoEvan Bierman, Brian Keating University of Paris - APCRomain Charlassier, Jean- Christophe Hamilton, Michel Piat

MBI-4 at Pine Bluff Observatory Madison, WI First light March 2008 Beam maps March 2009 See poster by Amanda Gault

MBI-4 interference fringes Baseline formed by horns 2 and 3 Observed Gunn oscillator on tower Observed Signal (Bolometer #9) Simulated Signal

MBI Interference Fringes

The QUBIC collaboration University of Wisconsin USA University of Richmond USA IUCAA, Pune India La Sapienza, Roma, Italia Universita di Milano- Bicocca Italia CESR Toulouse France Maynooth University Ireland Manchester University UK CSNSM Orsay France IAS Orsay France APC Paris France Brown University USA QU Bolometric Interferometer for Cosmology Google Maps A merging of MBI (USA) with BRAIN (Europe)

The QUBIC instrument concept Off-axis quasi-optical beam combiner Bolometer array phase shifters hornsbackhorns 4K 300 mK 4K Cryostat Sky ~70 cm ~60 cm ~10 cm ~25 cm ~40 cm

6 modules of 144 entry horns – 14 deg. primary beams – square compact configuration – multipole range : – ~900 TES bolometers / module – ~10000 baselines / module – phase switch redundant baselines simultaneously - phase steps of 15 degrees - sequence length ~500 steps 3 channels : 90,150,220 GHz 25% Bandwidth Modular Cryogenics – One 4K pulse tube for 6 modules – 100 mK focal plane r ~ 0.01 in one year of data QUBIC Design Primary (entry) horns ~ 25cm QUBIC (144x6, ( Significan ce Secondary (reemitting) horns

QUBIC program BRAIN Pathfinde r QUBIC first module QUBIC 2011 MBI MBI-4 Prototype – 4 horns bolometric interferometer – works in Wisconsin (2008 and 2009) – Fringes observed ! BRAIN Pathfinder – Site testing, logistics – Atmosphere characterization at Dome C –(effective temperature, polarization...) 2 campaigns, January 2006 and 2007 Third campaign starting next Antarctic summer QUBIC – Search for primordial B-modes (50 < l < 150) – 6 Bolometric interferometer modules – 144 horns/module (90, 150, 220 GHz) – 25% Bandwidth – Full instrument in – Target : r ~ 0.01 in 1 year of data

Next steps for Bolometric Interferometry phase modulators are critical - multiple phase states (~ 5 bits) - 1 ms switching speed - several technologies under study: Faraday, MEMs, s/c nanobridge switches, varactor diode simulations of systematic effects, scan strategies foreground removal in visibility space QUBIC see poster by T.K. Sridharan for alternate BI approach