1-3 July, 2009The Path to CMBPol Bolometric Adding Interferometry: MBI & QUBIC Peter Timbie...
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1-3 July, 20091-3 July, 2009 The Path to CMBPolThe Path to CMBPol
Bolometric Adding Interferometry:MBI & QUBIC
Peter Timbie University of Wisconsin - Madison
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
CMB Interferometers
(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
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
Interferometer Beam Systematics
j
n1 n2
uij €
VijU = dn1∫ dn2Gix (n1 )G jy (n2 ) Eix (n1 )E jy (n2 )
i
€
= dn∫ Gix (n)G jy (n)U(n)ei 2πuij ⋅n€
U(n1 )e2πiu ij ⋅n1δ(n1 − n2 )
Beam mismatch, distortion, etc. do not couple T into Stokes U visibility. [E.F. Bunn PRD 75, 083517 (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)
Adding Interferometer
for Many Horns OMTs
€
E⊥1 + E ||1 2||2 EE +⊥
N
EEEE
N
EEEE NNNN∗
⊥⊥⊥⊥ +++×
+++ )...()...( ||1||1||1||1
€
=(E⊥12 + ...E⊥N
2 ) + (E⊥1E||1 + ...E⊥NE||N ) + (E⊥1E||2 + ...E⊥1E||N ) + (E⊥1E⊥2 + ...E||E||N )
N
total power single-horn auto-correlation
Stokes U visibilities
N horns
2N phase modulators
beam combiner
detectors
€
E⊥N + E||N
Stokes I visibilities
// // //
….
….
Bolometer Array
Parabolic mirror
Phase Shifters
Feed horn antennasCryostat
45° CW twist rectangular wave guide
45º CCW twist rectangular wave guide
Quasioptical Beam Combiner
Interference pattern
1 horn 1 baseline 1 baseline 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:0806.0380, A&A
497 (2009) 963][Hyland et al., arXiv :0808.2403v1, 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:0807.0438, A&A 491-3 (2008) 923-927] updated with bandwidth and accurate NET calculations]
data pts fromsimulation
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
Liquid nitrogen tank
Liquid helium tank
Secondary mirror
3He refrigerator
Primary mirror
Bolometer unit
Phase modulators
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
University of Paris - APC Romain Charlassier, Jean-Christophe Hamilton, Michel Piat
MBI-4 at
Pine Bluff ObservatoryMadison, 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
The QUBIC collaborationUniversity of
Wisconsin USAUniversity
of Richmond
USA
IUCAA, Pune IndiaLa
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 CosmologyGoogle Maps
A merging of MBI (USA) with BRAIN (Europe)
The QUBIC instrument concept• Off-axis quasi-optical beam combiner
Bolometer arrayBolometer array
phase phase shiftersshifters
hornshorns
backbackhornshorns
4K
300 mK
4K
4K
4K
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 : 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 GHz25% 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, (
Signifi
cance
Secondary (reemitting) horns
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QUBIC program
2006
2007
2008
2009
2010
BRAINPathfinder
QUBICfirst module
QUBIC
2011
MBI-4
2012
• 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 2012-2013
– 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