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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.

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title slide
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.

maxipol collaboration
MAXIPOL Collaboration

Matthew Abroe1 Peter Ade3 Jamie Bock4 Julian Borrill5,6

Jeff Collins2 Pedro Ferreira7 Shaul Hanany1

Andrew Jaffe8Bradley Johnson7 Terry Jones1 Adrian Lee2,9

Tomotake Matsumura1Paul Oxley1Bahman Rabii2 Tom Renbarger1

Paul Richards2 George Smoot2,6,9 Radek Stompor5

Huan Tran2 Celeste Winant2 Proty Wu10 Joe Zuntz8

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, 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

what are the science goals of maxipol
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 and data analysis is now concluding.

maxipol instrument
MAXIPOL Instrument
  • Flight proven
  • MAXIMA hardware.
  • Sun shields not
  • illustrated.
half wave plate hwp polarimeter
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 4f

Q,U signal band

HWP rotation frequency

hwp polarimeter advantages
HWP Polarimeter Advantages
  • Proven astronomical technique

(see Astronomical Polarimetry by Tinbergen).

  • 4f 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.
hwp polarimeter hardware
HWP Polarimeter Hardware

HWP construction:

3.2 mm thick sapphire

anti-reflection coated

with Herasil.

maxipol payload on launch pad
MAXIPOL Payload on Launch Pad

sun shield

light from

the sky

sun-facing surfaces

painted white

terrestrial

emission

baffle

balloon

signals in the time domain
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

signals in the frequency domain
Signals in the Frequency Domain

power spectrum of TOD with hi and gi removed

signals in the frequency domain1
Signals in the Frequency Domain

frequency

domain

representation

of the

beam

power spectrum of TOD with hi and gi removed

HWP rotation frequency

telescope scan frequency

signals in the frequency domain2
Signals in the Frequency Domain

frequency

domain

representation

of the

beam

power spectrum of TOD with hi and gi removed

T signal

band

Q and U

signal

bands

HWP rotation frequency

telescope scan frequency

q u demodulation
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.
polarimeter characterization1
Polarimeter Characterization
  • receiver cross-polarization

and HWP encoder offset

  • modulation efficiency
  • similar measurement

limits instrumental

polarization to < 1%

polarimeter characterization2
Polarimeter Characterization

Modulation Efficiency Across the Array

error in measured

modulation efficiency = 1%

for all array elements

Results agree with predicted performance

assuming Pin = 0.97 and normal incidence for radiation

maxipol 1 flight
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.
primary maxipol 1 scan regions
Primary MAXIPOL-1 Scan Regions
  • MAXIPOL
  • Pointing
  • Illustrated.

SFD Dust Map Extrapolated to 140 GHz

Primary

CMB scan:

7.6 hours

centered on

Beta Ursae

Minoris.

Expected

dust signal =

4.4 ± 0.7 K

Primary

Dust scan:

1.9 hours

centered on

Polaris:

Dust signal =

38 ± 5 K

Schlegel, Finkbeiner and Davis. 1998. ApJ, 500:525-553.

intensity calibration from jupiter
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
data analysis
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.

conclusion
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.
  • Experiences from MAXIPOL are advising future
  • B-mode HWP experiments -- EBEX, Polarbear.

MAXIPOL-0 Launch

slide23
EBEX

expected EBEX performance

  • NASA funded LDB balloon experiment
  • achromatic HWP polarimeter
  • 1476 detectors
  • sensitivity: 0.7 K per pixel Q,U
instrumental signals
Instrumental Signals

same data plotted vs. HWP angle

16 minutes of MAXIPOL TOD

HWP synchronous instrumental signal

largest contributor is instrumental polarization

instrumental signal removal
Instrumental Signal Removal

frequency

domain

representation

of the

beam

power spectrum of TOD

HWP rotation

frequency

instrumental

polarization

telescope scan frequency

differential transmission