Title Slide MAXIPOL A Bolometric BalloonBorne HalfWave Plate

Title Slide MAXIPOL: A Bolometric, Balloon-Borne Half-Wave Plate Polarimeter for Measuring the Polarization of the CMB Bradley R. Johnson NSF and PPARC Postdoctoral Fellow University of Oxford The MAXIPOL payload on the launch pad at the NSBF in Ft. Sumner, New Mexico, September 2002. B. R. Johnson University of Oxford 1

MAXIPOL Collaboration Matthew Abroe 1 Peter Ade 3 Jamie Bock 4 Julian Borrill 5, 6 Jeff Collins 2 Pedro Ferreira 7 Shaul Hanany 1 Andrew Jaffe 8 Bradley Johnson 7 Terry Jones 1 Adrian Lee 2, 9 Tomotake Matsumura 1 Paul Oxley 1 Bahman Rabii 2 Tom Renbarger 1 Paul Richards 2 George Smoot 2, 6, 9 Radek Stompor 5 Huan Tran 2 Celeste Winant 2 Proty Wu 10 Joe Zuntz 8 1) School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA 2) Department of Physics, University of California, Berkeley, CA, USA 3) Department of Physics and Astronomy, Cardiff University, Cardiff, UK 4) Jet Propulsion Laboratory, Pasadena, CA, USA 5) Computational Research Division, Lawrence Berkeley National Lab, Berkeley, CA, USA 6) Space Sciences Laboratory, University of California, Berkeley, CA, USA 7) Astrophysics, University of Oxford, UK 8) Astrophysics Group, Blackett Lab, Imperial College, London, UK 9) Physics Division, Lawrence Berkeley National Lab, Berkeley, CA, USA 10) Department of Physics, National Taiwan University, Taipei, Taiwan B. R. Johnson University of Oxford 2

What are the Science Goals of MAXIPOL? 1) Implement half-wave plate (HWP) polarimetry in a CMB experiment. - MAXIPOL is a pathfinder experiment -- HWP polarimeter techniques and data analysis algorithms will be useful for B-mode experiments. - MAXIPOL is a reimplementation of the MAXIMA hardware - MAXIMA reported best receiver NET -- 40 K sec. - We wanted to develop a polarization modulator -- HWP polarimeter is the best. • Attempt detection of E-mode signal. - Even with the high receiver sensitivity, predictions showed unambiguous E-mode detection would be challenging -- long integration time was required. - We collected data analysis is now concluding. B. R. Johnson University of Oxford 3

MAXIPOL Instrument • Flight proven MAXIMA hardware. • Sun shields not illustrated. B. R. Johnson University of Oxford 4

Cross-Section of MAXIPOL Instrument B. R. Johnson University of Oxford 5

Half-Wave Plate (HWP) Polarimeter • signal amplitude corresponds to polarization magnitude. • signal phase corresponds to polarization orientation. • Q, U sky signals in the frequency domain are away from 1/f noise in sidebands of 4 f HWP rotation frequency B. R. Johnson Q, U signal band University of Oxford 6

HWP Polarimeter Advantages • Proven astronomical technique (see Astronomical Polarimetry by Tinbergen). • 4 f modulation provides strong rejection of systematic error. • I, Q and U maps from ONE detector. • Therefore, not susceptible to differential bolometer gain problems. • Q, U signal is far from typical 1/f noise. • Therefore, best noise performance is achieved. B. R. Johnson University of Oxford 7

HWP Polarimeter Hardware HWP construction: 3. 2 mm thick sapphire anti-reflection coated with Herasil. B. R. Johnson University of Oxford 8

MAXIPOL Payload on Launch Pad sun shield light from the sky sun-facing surfaces painted white balloon B. R. Johnson terrestrial emission baffle University of Oxford 9

Signals in the Time Domain time ordered data is comprised of four primary signals these signals must be rejected modulated sky signals HWP synchronous instrumental signals ie. instrumental polarization note: i is time index cosmic rays, etc. Reference: B. R. Johnson, J. S. Collins Ph. D. theses B. R. Johnson University of Oxford 10

Signals in the Frequency Domain power spectrum of TOD with hi and gi removed B. R. Johnson University of Oxford 11

Signals in the Frequency Domain power spectrum of TOD with hi and gi removed frequency domain representation of the beam HWP rotation frequency telescope scan frequency B. R. Johnson University of Oxford 12

Signals in the Frequency Domain power spectrum of TOD with hi and gi removed T signal band frequency domain representation of the beam Q and U signal bands HWP rotation frequency telescope scan frequency B. R. Johnson University of Oxford 13

Q, U Demodulation • HWP polarimeter works. • Nominal noise level is recovered in the Q, U signal band. • Maps from demodulated data show no systematic error. B. R. Johnson University of Oxford 14

Polarimeter Characterization B. R. Johnson University of Oxford 15

Polarimeter Characterization • receiver cross-polarization and HWP encoder offset • modulation efficiency • similar measurement limits instrumental polarization to < 1% B. R. Johnson University of Oxford 16

Polarimeter Characterization Modulation Efficiency Across the Array 0. 92 0. 93 0. 90 0. 93 0. 94 0. 95 0. 93 0. 92 error in measured modulation efficiency = 1% for all array elements Results agree with predicted performance assuming Pin = 0. 97 and normal incidence for radiation B. R. Johnson University of Oxford 17

MAXIPOL-1 Flight • 26 hour flight from Ft. Sumner, New Mexico, USA in May 2003. • Four regions of the sky were observed. • Jupiter was mapped twice. - beam shape - calibration • CMB dipole was scanned. B. R. Johnson University of Oxford 18

Primary MAXIPOL-1 Scan Regions SFD Dust Map Extrapolated to 140 GHz • MAXIPOL Pointing Illustrated. Primary CMB scan: Primary Dust scan: 7. 6 hours centered on Beta Ursae Minoris. 1. 9 hours centered on Polaris: Expected dust signal = 4. 4 ± 0. 7 K Dust signal = 38 ± 5 K Schlegel, Finkbeiner and Davis. 1998. Ap. J, 500: 525 -553. B. R. Johnson University of Oxford 19

Intensity Calibration from Jupiter beam map from one 140 GHz photometer • Primary calibration from Jupiter observations. • Map and best-fit Gaussian contours overplotted (1, 10, 50 and 90%) • Some photometer beams were not sampled in every pixel • Final calibration results from maximum-likelihood analysis B. R. Johnson University of Oxford 20

Data Analysis • Data analysis is near completion. • Two analysis algorithms are being used -- MADCAP and frequentist approach. • Both methods are producing consistent results. • Q, U maps are Gaussian, contain no detectable systematic error. B. R. Johnson University of Oxford 21

Conclusion • MAXIPOL demonstrated HWP polarimetry works for CMB experiments to the sensitivity limit of the instrument. • Data analysis is near completion. • Results papers are currently being written. • Papers will include Q, U maps and power spectrum estimates. MAXIPOL-0 Launch • Experiences from MAXIPOL are advising future B-mode HWP experiments -- EBEX, Polarbear. B. R. Johnson University of Oxford 22

EBEX expected EBEX performance • NASA funded LDB balloon experiment • achromatic HWP polarimeter • 1476 detectors • sensitivity: 0. 7 K per pixel Q, U B. R. Johnson University of Oxford 23

END B. R. Johnson University of Oxford 24

Wrong Way B. R. Johnson University of Oxford 25

Instrumental Signals 16 minutes of MAXIPOL TOD same data plotted vs. HWP angle HWP synchronous instrumental signal largest contributor is instrumental polarization B. R. Johnson University of Oxford 26

Instrumental Signal Removal power spectrum of TOD HWP rotation frequency domain representation of the beam instrumental polarization differential transmission B. R. Johnson telescope scan frequency University of Oxford 27