Bolometric%20Adding%20Interferometry:%20MBI%20

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Bolometric Adding InterferometryMBI QUBIC
Peter Timbie University of
Wisconsin - Madison
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CMB Interferometers
??(GHz) FOV ants 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

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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 Ex and Ey 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

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Interferometer Beam Systematics
Interferometers measure visibilities
n1
n2
y
j
uij
i
x
X
Beam mismatch, distortion, etc. do not couple T
into Stokes U visibility. E.F. Bunn PRD 75,
083517 (2007)
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Beam Combination for Large N

• 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?
• 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)

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Ryles Adding Interferometer (1952)
visibility
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Adding Interferometerfor Many Horns
N horns
OMTs
2N phase modulators

beam combiner
detectors
single-horn auto-correlation
Stokes U visibilities
Stokes I visibilities
total power
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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
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Interference pattern

• 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., arxiv0806.0380, AA 497
(2009) 963
Hyland et al., arXiv 0808.2403v1, MNRAS 393
(2009) 531
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Sensitivity - comparison to imager

• Both systems have
• 256 horns
• 1? angular resolution
• background-limited bolos
• 25 bandwidth
• Interferometer
• co-adds redundant visibilities
• has 1000 detectors

data pts from simulation
Hamilton et al., arxiv0807.0438, AA 491-3
(2008) 923-927 updated with bandwidth and
accurate NET calculations
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The Millimeter-Wave Bolometric Interferometer
(MBI-4)

• Fizeau (optical) beam combiner
• 4 feedhorns (6 baselines)
• 90 GHz (3 mm)
• 1o angular resolution
• 7o FOV

Antennas
Phase modulators
Liquid nitrogen tank
Liquid helium tank
Secondary mirror
3He refrigerator
Primary mirror
Bolometer unit
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MBI Assembly

15 cm
19 spider-web bolos (JPL) (PSBs not required)
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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 OSullivan, 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
University of Paris - APC Romain Charlassier, Jean-Christophe Hamilton, Michel Piat
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MBI-4 at Pine Bluff ObservatoryMadison, WI

• First light March 2008
• Beam maps March 2009
• See poster by Amanda Gault

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MBI-4 interference fringes
Observed Signal (Bolometer 9)
Simulated Signal

• Baseline formed by horns 2 and 3
• Observed Gunn oscillator on tower

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

• Off-axis quasi-optical beam combiner

Sky
25 cm
4K
4K
4K
back horns
4K
60 cm
40 cm
4K
10 cm
Cryostat
300 mK
70 cm
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QUBIC Design

• 6 modules of 144 entry horns
• 14 deg. primary beams
• square compact configuration
• multipole range 25-150
• 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

25cm
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QUBIC program

• 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 lt l lt 150)
• 6 Bolometric interferometer modules
• 144 horns/module (90, 150, 220 GHz)
• 25 Bandwidth
• Full instrument in 2012-2013

2006
BRAIN Pathfinder
MBI-4
2007
2008
2009
2010
QUBIC first module
2011
QUBIC
2012
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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