QUIET-I and QUIET-II: HEMT-based coherent CMB polarimetry Great Lakes Cosmology Workshop X June 14, 2010 Immanuel Buder (for the QUIET Collaboration) Department of Physics, U. of Chicago
Outline Science Motivation QUIET Experiment Timeline QUIET Collaboration Phase I Instrumentation and Observation Phase I Analysis Status QUIET Phase II Plan
Science Motivation CMB Polarization Anisotropy Inflation, Primordial Gravity Waves Baumann (2009) WMAP Science Team Primordial B-mode Gravitational Lensing B-mode
QUIET Timeline Phase I Development Q-Band Observing Q-Band Analysis W-Band Observing (Finish Dec. 2010) Phase II October 2008: Start Q-Band observing August 2009: Start W-Band Observing Late 2010? Start Phase II
QUIET Collaboration Chicago (KICP) Fermilab Michigan Manchester Oxford Oslo MPI-Bonn Stanford (KIPAC) KEK Caltech JPL Columbia Princeton Miami Observing Site Chajnantor Plateau, Chile 5 countries, 14 institutions, ~35 scientists
QUIET Phase I Summary Frequencies 44 (Q-Band) / 95 (W-Band) GHz Angular resolutions 27 / 12 (FWHM) arcmin at each freq Field centers and sizes 181/-39, 78/-39, 12/-48, 341/-36 4x(15 15) = 900 Ra/Dec (Deg) Telescope type Detector type crossed MizuguchiDragone Phaseswitch (4kHz&50Hz), Boresight, Sky rotation, Fast scan HEMT Location Chajnantor(Atacama),Chile Polarization Modulations Instrument NEQ/U 64 / 57 Size (Deg2) Bolometer, HEMT etc. µk s1/2, combined Q and U Observation time range Oct. 2008 Dec. 2010 Planned observing time 3600 / 7500 hours 0.5 (?) No foreground assumed Projected limit on r
QUIET Detectors Miniaturized pseudocorrelation polarimeter on a chip, making large arrays feasible 3cm module (W-Band) cf. CAPMAP polarimeter, ~30cm
QUIET Module Operation L=EX+iEY Simultaneously Measures Q and U linear polarization parameters Gain difference between legs does not fake a signal Modulation 1/f noise reduction Double-modulation cancels temperature to polarization leakage in the module R=EX iey HEMT Amplifiers +1 ±1 Phaseswitch 4kHz & 50Hz 180 Coupler Detector Diode Q L± +Q R 2 90 Coupler +U U L± ir 2
Phase I Detector Array Septum Polarizer Module W-Band array (90 elements): the world's largest HEMT-based array polarimeter
Phase I Instrument Receiver Feedhorn array Septum Polarizers Detector Modules Groundscreen Secondary Mirror Primary Mirror Electronics 3-axis Mount (azimuth, elevation, boresight): boresight rotation allows additional polarization modulation and suppresses residual temperature to polarization leakage
QUIET Observations 4 CMB 2 Galaxy Science CMB Patches chosen to minimize foregrounds Each patch is ~15 x 15
Observing Site Chajnantor Plateau, Atacama, Chile 5 km elevation Very low moisture Year-round observing, day and night Sky rotation causes the patches to rise and set Follow with constant elevation azimuth scans Sky rotation modulates polarization each day
Q-Band Analysis: CMB Signal is small and there are many possible contaminations Null tests verify cuts, calibration, treatment of systematic effects Divide data into two subsets (e.g. good/bad weather) Make maps m1 and m2 Compute CMB power of null map m1 - m2 Preliminary Q-Band Null Test Suite (~40)
W-Band Analysis Status W-Band observation continuing until end of 2010 Sensitivity (57 µk s1/2), responsivity, detector polarization angle, temperature to polarization leakage, optics sidelobes measured in field Scan Frequency
QUIET Phase II Technology demonstrated in Phase I Increase number of modules to ~1600 Same frequencies as Phase I plus 32 GHz for foreground control Phase II Phase I
Phase II Science Forecast High S/N measurement of E-mode to ell ~2000 B-mode measurement to ell ~1200 Detect r or limit to ~0.018 (at 2 ) Detect lensing at ~35 limit m < 0.3 ev
Conclusions QUIET is a CMB polarimeter with a unique design based on HEMT detector technology HEMT technology gives us unique means of controlling systematics and access to low frequency (synchrotron) foreground characterization Look for Phase I results soon Phase II will have sensitivity to detect B-modes with technology and control of systematic effects proven in Phase I
Backup Slides
Q-Band Analysis: Galaxy ~100 hours of data from one Galactic patch in Q-Band Top: WMAP Bottom: QUIET PRELIMINARY
Phase I Science Forecast Q-Band E-mode (MC sim.) B-mode results compared to existing measurements Q-Band (data collected) W-Band will be the world best
TT Assembly Replace Septum Polarizer with OMT+Magic Tee to measure temperature anisotropy
Stokes Parameters E Eb y Ea Ex 2 x 2 y Q=E E U = Ea2 Eb2