QUIET Q/U Imaging ExperimenT
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Transcript of QUIET Q/U Imaging ExperimenT
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QUIETQ/U Imaging ExperimenT
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QUIET Project
Miami Physics Conference 2009December 16
Raul Monsalve for the QUIET CollaborationUniversity of Miami
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What is QUIET ?
• Radiotelescope that measures intensity and polarization of the CMB
• Located in Chile
• Main science objective is to improve characterization of E-mode polarization and detect the difficult B-mode polarization
• Two phases are planned. Phase-I is ongoing, started in August 2008. Phase II is planned to start in 2012, in a larger
scale, improving the techniques learned during phase-I
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CALTECH
STANFORD
FERMILAB
U. CHICAGO
COLUMBIA
U. MIAMI
JPL
SITE
MANCHESTER
OSLO
MPI-BONN
KEK
PRINCETON
OXFORD
QUIET Collaboration
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Science Goals
• We can measure the polarisation of the CMB the same way as for light
• The Stokes parameters quantify the polarization properties of a light ray▫ I = no filter at all ▫ Q = linear polarizer at 0 and 90°▫ U = linear polarizer at -45 and 45 °▫ V = circular polarizer
• I is just the temperature
• Q and U combine to form E- and B-modes
• No known physical process can generate V-polarized CMB radiation
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Status and Forecast on the EE and BB characterization
Science Goals
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Site and Instrumentation
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Site• Chajnantor Scientific Reserve in Chile at 5080 m above sea level• Among the best places for mm and submm astronomy• Access to CBI infrastructure• Accessible at all times• 1 hour drive from San Pedro de Atacama• Good sky coverage• For outside work bottled oxygen systems are used• Oxygen concentration in control room is increased ~27%
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Q Band W Band
Frequency 40 GHz 90 GHz
N° of HEMT Detectors
17/2 84/6
Resolution 28 arcmin (FWHM) 12 arcmin (FWHM)
Telescope Type Crossed Dragone Crossed Dragone
Module Sensitivity 300 μK s½ 550 μK s½
Array Sensitivity 70 μK s½ 60 μK s½
Observation Period Oct 2008 – June 2009 June 2009 – Mid 2010 ?
Phase-I Summary
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Mount
• Inherited from CBI• Alt-Az axes• Rotation about optical axis (boresight axis)• Elevation range limited to 43 deg < el < 87 deg
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Optics
• Crossed Dragone design • 1.4 m primary and secondary mirrors• FWHM: 28 (Q) and 12 (W) arcmin
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Horn Arrays
• Conical corrugated feed horn arrays• Excellent beam symmetry• Low sidelobe response• Low cross-polarization• Broad frequency band• Typical FWHM of ~7 deg• Built by UM
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OMTs
• Splits incoming radiation into L and R• 20% bandwidth• Low loss• High isolation on the output ports to avoid temperature-to-polarization leakage
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Detector Modules
• Heart of the receiver • Polarimeter on a chip• Automated assembly and operation• Measuring of Q and U simultaneously in each pixel• Operate at ~20K
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Module/OMTs
Seven element demonstration array
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Receiver
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Calibration and Preliminary
Data
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Polarization
MOONOnce/7 days,
Relative Gains,Angles
NOISE SOURCEOnce/1.5 hours,Relative Gains,
Angles
TAU AOnce/2 days,
Absolute Gains,Angles, Beams
SKY-DIPOnce/1.5 hours,Relative Gains,
Stability
JUPITEROnce/7 days,
∆T Gains,Beam
Gain Stability
Temperature
Calibration Strategy
+ supplemental measurements
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Beam Shape using Jupiter
Calibration
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Tau A Gains
Moon Polarization Fits
Calibration
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CMB Analysis
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Observation Regions
4x(15x15)=900 [deg²]
Patch Centers
• Low foreground regions in coordination with ABS, Polarbear (Multifrequency measurements for galactic foreground removal)• Distribution to allow continuous scanning
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Average 68.1%
Downtime mainly due to:-Mechanical Problems-Generator problems-Bad weather
Telescope Operation during Q-Band Season
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Phase-I, EE Power-spectra Forecasts
Q W
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Patch 2a Results (PRELIMINARY)
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Other Interesting ObservationsGalactic Center Polarization Maps with Q-Band Data (PRELIMINARY)
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Other Interesting ObservationsGalactic Center Temperature Map with Q-Band Data (PRELIMINARY)
QUIET WMAP
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Phase-II
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Phase-II Summary
Ka Band Q Band W Band
Frequency 32 GHz 40 GHz 90 GHz
N° of modules (P/T) 16/2 55/6 1389/108
Beamsize (FWHM) 28 arcmin 20 arcmin 8.5 arcmin
Module Sensitivity 165 μK s½ 178 μK s½ 364 μK s½
Beginning operations 2013 ?
N° of telescopes 3
Telescope type Crossed Dragone
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Phase-II Power-spectra Forecasts
Current Performance Likely Improvement (noise, duty cycle, 1/f)
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Appendix
• Alternate technique to identify gravitational lensing effects (Zaldarriaga(1999), Hu(2002))
• Lens reconstruction: Lensing Deflection Field calculation from cross-correlation of E- and B-modes
• Stronger constraints on cosmological parameters than using B-mode power spectrum
• By measuring shape and amplitude of the Deflection power spectrum QUIET Phase-II can place constraints on parameters such as:
• Neutrino mass (Maltoni, 2004)
• Dark energy density (Stompor, 1999)
• Spatial curvature (Stompor, 1999)
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Summary
• QUIET Science:• Experiment addressing fundamental questions in physics
• Taking the CMB polarization knowledge to new levels
• QUIET Status:• Largest HEMT-based focal plane array ever deployed, using state of the
art MMIC packaging techniques
• Phase-I observing and proposing Phase-II to start in 2012/2013
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Systematic Errors
o Overall signal sizeo Overall gain calibrationo Beamsize calibrationo Pointing error
o Fake signal sourceo Instrumental I->Q/U : caused by OMT, 1% for Q-band. Negligible. o Gain fluctuations : up to 20% negligible for phase I.
o E->B mixing sourceo Polarization angle : calibration better than 5% for phase I. o Optics cross polarization : only affects by order of ∆ө²o Q/U gain mismatch : relative gain between Q and U stable.o Patch geometry : finite patch, patch irregularity, pixelization
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Systematic Errors
E->B, Patch geometry