CAPMAPCAPMAP Measuring the Polarization of the Polarization of the C osmic M icrowave M icrowave B ackground B ackground Measuring the Polarization of the Polarization of the C osmic M icrowave M icrowave B ackground B ackground Dorothea Samtleben, Center for Cosmological Physics, University of Chicago

Center for Cosmological Physics (CfCP)  National Science Frontier Center  Founded at the University of Chicago in August 2001 for initially 5 years  Creation of an interdisciplinary environment  14 faculty, 10 center fellows, graduate students, associated postdocs...  National Science Frontier Center  Founded at the University of Chicago in August 2001 for initially 5 years  Creation of an interdisciplinary environment  14 faculty, 10 center fellows, graduate students, associated postdocs...

Research Focus  Theory  Structures in the Universe  Cosmic Radiation Backgrounds  High Energy Particles from Space  Theory  Structures in the Universe  Cosmic Radiation Backgrounds  High Energy Particles from Space Four major research components:

Activities of the Center  Various formal and informal seminars  Workshops (Auger-workshop, COSMO-02)  Visitors  Dedicated outreach and education efforts  Opportunities for sabbaticals for High Energy Physicists  Various formal and informal seminars  Workshops (Auger-workshop, COSMO-02)  Visitors  Dedicated outreach and education efforts  Opportunities for sabbaticals for High Energy Physicists

 Motivation What do we want to learn from our experiment?  Experimental approach Which strategy to choose?  Experimental design What does our experiment look like?  Motivation What do we want to learn from our experiment?  Experimental approach Which strategy to choose?  Experimental design What does our experiment look like? Talk Outline

How can we improve our understanding of nature?  Set up an experiment to study a well defined configuration e.g. High Energy Physics  Study the outcome of an experiment which nature has set up e.g. Astrophysics  Set up an experiment to study a well defined configuration e.g. High Energy Physics  Study the outcome of an experiment which nature has set up e.g. Astrophysics

Setup of nature‘s ‘experiment‘

How can we find out what happened in the early universe?  We do have witnesses!  We will learn about the conditions in the infant universe by a thorough questioning of the witnesses  We can compare our theories with the information they provide and improve our understanding of the evolution of the universe  We do have witnesses!  We will learn about the conditions in the infant universe by a thorough questioning of the witnesses  We can compare our theories with the information they provide and improve our understanding of the evolution of the universe

The witnesses: Photons of the Cosmic Microwave Background Radiation The witnesses: Photons of the Cosmic Microwave Background Radiation -100 mK +100 mK The sky observed at 90 GHz (COBE DMR)

What happened 300,000 years after the Big Bang?  The plasma of photons, protons and electrons became cold enough so that electrons and protons formed first atoms  The universe became transparent  These photons give us a direct snapshot of the infant universe  Still around today but cooled down (shifted to microwaves) due to the expansion of the universe  The plasma of photons, protons and electrons became cold enough so that electrons and protons formed first atoms  The universe became transparent  These photons give us a direct snapshot of the infant universe  Still around today but cooled down (shifted to microwaves) due to the expansion of the universe

Expectations from inflationary models for CMB observations  Blackbody spectrum  Homogeneous, isotropic  On large scales scale-invariant temperature fluctuations (regions were not yet causally connected)  On small scales temperature fluctuations from ‘accoustic oscillations‘ (radiation pressure vs gravitational attraction)  Polarization anisotropies, correlated with temperature anisotropies  Blackbody spectrum  Homogeneous, isotropic  On large scales scale-invariant temperature fluctuations (regions were not yet causally connected)  On small scales temperature fluctuations from ‘accoustic oscillations‘ (radiation pressure vs gravitational attraction)  Polarization anisotropies, correlated with temperature anisotropies

Characteristics of the CMB  Frequency Spectrum  Temperature Anisotropy  Polarization  Frequency Spectrum  Temperature Anisotropy  Polarization Frequency spectrum of the CMB (Compilation by Richard McCray) Frequency spectrum of the CMB (Compilation by Richard McCray)

Temperature Anisotropy of the CMB Dipole due to peculiar velocity of solar system Emission from the galactic plane Remaining CMB anisotropy Dipole due to peculiar velocity of solar system Emission from the galactic plane Remaining CMB anisotropy COBE results

DASI: First Detection of CMB Polarization (September 2002) DASI: First Detection of CMB Polarization (September 2002) Map is 5 degrees square 200 m K m K 5 K5 K

Spherical Harmonics Description of CMB by using spherical harmonics Y lm (q,j ) Y lm Pictures by Clem Pryke

Description of Anisotropies  Usually representation by power spectrum C l (variance at the multipole l)  Angular scale: q ~ 180°/ l  Usually representation by power spectrum C l (variance at the multipole l)  Angular scale: q ~ 180°/ l  Statistical properties of CMB can be observed and compared with theory

Temperature Power Spectra Compilation by Wayne HuCompilation by Max Tegmark

Dependence on cosmological parameters Change in baryon density Change in curvature Animations by Max Tegmark

Why is the CMB polarized? Thomson scattering Radiation incident along this axis Charge moves along this axis Radiation primarily scattered along this axis Charge moves in two directions Unpolarized radiation incident along this axis Polarized radiation scattered in this plane Pictures by Matthew Hedman

Quadrupole pattern Quadrupole pattern in the radiation will create polarization Quadrupole moment in motion of charge Radiation scattered along this axis has a polarized component

A view on the dynamic universe  Quadrupole moments from Temperature anisotropies will be washed out  Dynamics in the early universe determine the polarization spectrum  Quadrupole moments from Temperature anisotropies will be washed out  Dynamics in the early universe determine the polarization spectrum

Density fluctuations E-modes Gravity waves E- and B-modes, Amplitude determined by scale of inflation Different Polarization patterns E-Mode (scalar, even parity) E-Mode (scalar, even parity) B -Mode (vector or tensor, odd parity) B -Mode (vector or tensor, odd parity)

Why did the CMB polarization escape detection for so long?  Highly sensitive detectors  Excellent control of systematics (atmospheric, instrumental)  Excellent angular resolution  Highly sensitive detectors  Excellent control of systematics (atmospheric, instrumental)  Excellent angular resolution Tiny fluctuations (1 part in 1 million) on small angular scale Challenge for the experiments: Tiny fluctuations (1 part in 1 million) on small angular scale Challenge for the experiments:

Comparison of Power Spectra

How to catch and query the witnesses?  Based at ground, balloon, space?  Which frequency to observe?  Which techniques to use (HEMT,Bolometers)?  What is an optimal scanning strategy?  Based at ground, balloon, space?  Which frequency to observe?  Which techniques to use (HEMT,Bolometers)?  What is an optimal scanning strategy?

Height in the atmosphere at which radiation is attenuated by a factor 1/2 Atmospheric Transmission

Are there false witnesses?  Dust  Synchrotron  Point Sources  Dust  Synchrotron  Point Sources  Gravitational Lensing  S-Z from Clusters  ???  Gravitational Lensing  S-Z from Clusters  ??? Compilation by Matthew Hedman

DASI30(13)20‘South Pole CBI30(13) 3‘Atacama (Chile) VLA8.46‘‘Socorro (New Mexico) ATCA8.7(5) 2‘Australia AMIBA90(19)2‘Mauna Loa (Hawaii) SPORT22,32,60,907°ISS, full sky MAP22,30,40(2),60(2),90(4)13‘L2, full sky PLANCK-LFI30(4), 44(6),70(12), 100(34)33,23,13,10L2, full sky BAR-SPORT32,9030‘,12‘Antarctic LDB POLAR307°Wisconsin COMPASS307°Wisconsin PIQUE40,9030‘,15‘New Jersey CAPMAP40(4),90(10)7‘,3‘New Jersey PLANCK-HFI100(4),143(12),217(12), 353(6),545(8),857(6)11‘,8‘,6‘,5‘L2, full sky B2K+X150(4), 240(4) 340(4)10‘Antarctic LDB MAXIPOL150(12) 420(4)10‘US Balloon BICEP150(96)0.7 ° South Pole (?) POLARBEAR150(~3000)10‘South Pole POLATRON902‘Ovro QUEST100,150(~30)6‘Atacama (Chile) DASI30(13)20‘South Pole CBI30(13) 3‘Atacama (Chile) VLA8.46‘‘Socorro (New Mexico) ATCA8.7(5) 2‘Australia AMIBA90(19)2‘Mauna Loa (Hawaii) SPORT22,32,60,907°ISS, full sky MAP22,30,40(2),60(2),90(4)13‘L2, full sky PLANCK-LFI30(4), 44(6),70(12), 100(34)33,23,13,10L2, full sky BAR-SPORT32,9030‘,12‘Antarctic LDB POLAR307°Wisconsin COMPASS307°Wisconsin PIQUE40,9030‘,15‘New Jersey CAPMAP40(4),90(10)7‘,3‘New Jersey PLANCK-HFI100(4),143(12),217(12), 353(6),545(8),857(6)11‘,8‘,6‘,5‘L2, full sky B2K+X150(4), 240(4) 340(4)10‘Antarctic LDB MAXIPOL150(12) 420(4)10‘US Balloon BICEP150(96)0.7 ° South Pole (?) POLARBEAR150(~3000)10‘South Pole POLATRON902‘Ovro QUEST100,150(~30)6‘Atacama (Chile) Overview of Polarization Experiments Experiment Freq in GHz (#chan) Beamsize Location Technique Overview of Polarization Experiments Experiment Freq in GHz (#chan) Beamsize Location Technique Based on compilation by Peter Timbie Interferometer Correlation Polarimeterr Bolometer

Princeton D. Barkats, P. Farese, J. McMahon, S. T. Staggs + undergraduates Chicago C. Bischoff, M. Hedman, D. Samtleben, K. Vanderlind, B. Winstein + undergraduates Miami J. Gundersen, E. Stefaniescu JPL T. Gaier Princeton D. Barkats, P. Farese, J. McMahon, S. T. Staggs + undergraduates Chicago C. Bischoff, M. Hedman, D. Samtleben, K. Vanderlind, B. Winstein + undergraduates Miami J. Gundersen, E. Stefaniescu JPL T. Gaier CAPMAP

CAPMAP Chicago Miami JPL Princeton

Experimental setup  Telescope at Crawford Hill (New Jersey), 7 m dish, off-axis, Cassegrain, 0.05 FWHM beam  Correlation receiver  W-Band ( GHz) and Q-Band (36-45 GHz)  This winter 4 horns, final design 14 horns  Scanning on a small cap (1 degree diameter) around NCP  Telescope at Crawford Hill (New Jersey), 7 m dish, off-axis, Cassegrain, 0.05 FWHM beam  Correlation receiver  W-Band ( GHz) and Q-Band (36-45 GHz)  This winter 4 horns, final design 14 horns  Scanning on a small cap (1 degree diameter) around NCP

G x G y (E a - E b ) E x = E a - E b E y = E a + E b EbEb EbEb EaEa EaEa ExEx ExEx EyEy EyEy Multiplier GyGy GyGy GxGx GxGx 22 Correlation Polarimeter Phase Switch  Signal size ~10 W Amplification crucial  Not affected by drift of relative gains but sensitive to relative phase shifts  Output from multiplier ~ E x, E y eliminated by use of phase switch: signal in one line multiplied by square wave, after multiplication demodulated  Signal size ~10 W Amplification crucial  Not affected by drift of relative gains but sensitive to relative phase shifts  Output from multiplier ~ E x, E y eliminated by use of phase switch: signal in one line multiplied by square wave, after multiplication demodulated

Sensitivity of experiments T sys : System temperature Dn : Bandwidth T int : Integration time D G/G: Relative gain drift of amplifier ~ 1/f amplifier ~ 1/f S: Sensitivity T sys : System temperature Dn : Bandwidth T int : Integration time D G/G: Relative gain drift of amplifier ~ 1/f amplifier ~ 1/f S: Sensitivity Large bandwidth and low system temperature desirable Expected CAPMAP sensitivity: Large bandwidth and low system temperature desirable Expected CAPMAP sensitivity:

Elimination of drifts by ‘chopping‘ Taking the difference of two measurements at different spots on the sky (same azimuthal position) gets ríd off drifts PIQUE data

Experimental setup 7m Telescope Horn Radiometer RF IF IF box Data Acquisition

HornHorn Predicted and measured Beam Pattern Model of the horn 15 cm

Schematics of CAPMAP radiometer  Two different temperature stages: 20 K and room temperature  In RF part rectangular waveguides, in IF part coaxial cables  Two different temperature stages: 20 K and room temperature  In RF part rectangular waveguides, in IF part coaxial cables 82 GHz GHz 2-18 GHz

Setup at Chicago

3 inch (7.6 cm)

IF section

Phase matching In-phase response ~A cos j In-phase response ~A cos j Out of phase response (90 degree switch) ~A sin j Out of phase response (90 degree switch) ~A sin j

Data Acquisition  PCI card, 32 channels  24 bit resolution  Sampling rate ~100 kHz, demodulation in software  Data rate ~250 Hz  7 GByte/day (final design 24 GByte/day)  PCI card, 32 channels  24 bit resolution  Sampling rate ~100 kHz, demodulation in software  Data rate ~250 Hz  7 GByte/day (final design 24 GByte/day)

Work at the telescope...

PIQUE setup at the telescope

First Data – Total Power Channels Moon Jupiter Peak: 200 K Peak: 1 K

First Data – Polarization Channels Moon Tau A (Crab Nebula) Peak: 1 K Peak: 25 mK

AnalysisAnalysis Measure temperature/polarization in a region of the sky and compare with expectation (likelihood analysis): l-coverage determined by beam size d : Data vector C = C N + C T C N : Noise covariance C T : Theory covariance d : Data vector C = C N + C T C N : Noise covariance C T : Theory covariance

Expected Sensitivity CAPMAP expectation DASI result CAPMAP expectation DASI result

Summary and Outlook  CMB is the oldest light in the universe  Provides direct view of the infant universe  Measurement of CMB Polarization is a big experimental challenge, anisotropies of the order of 1 part in 1 million  CAPMAP uses a 7m telescope in New Jersey to observe the polarization at 90 and 40 GHz  Installation of 4 out of 14 horns underway  First data taking winter 2002/2003  CMB is the oldest light in the universe  Provides direct view of the infant universe  Measurement of CMB Polarization is a big experimental challenge, anisotropies of the order of 1 part in 1 million  CAPMAP uses a 7m telescope in New Jersey to observe the polarization at 90 and 40 GHz  Installation of 4 out of 14 horns underway  First data taking winter 2002/2003 Exciting time in cosmology, share it with us at the CfCP!