The Atacama B‐Mode Search: CMB Polarimetry with Transition‐Edge‐Sensor Bolometers

The Atacama B‐mode Search (ABS) experiment is a 145 GHz polarimeter designed to measure the B‐mode polarization of the Cosmic Microwave Background (CMB) at large angular scales. The ABS instrument will ship to the Atacama Desert of Chile fully tested and ready to observe in 2010. ABS will image large‐angular‐scale CMB polarization anisotropies onto a focal plane of 240 feedhorn‐coupled, transition‐edge sensor (TES) polarimeters, using a cryogenic crossed‐Dragone design. The ABS detectors, which are fabricated at NIST, use orthomode transducers to couple orthogonal polarizations of incoming radiation onto separate TES bolometers. The incoming radiation is modulated by an ambient‐temperature half‐wave plate in front of the vacuum window at an aperture stop. Preliminary detector characterization indicates that the ABS detectors can achieve a sensitivity of 300 μKs in the field. This paper describes the ABS optical design and detector readout scheme, including feedhorn design and performance, magnetic shielding, focal plane architecture, and cryogenic electronics.

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Polarimetry
transition-edge sensors
bolometers

References(13)

Figures(0)

[1]

Signature of gravity waves in polarization of the microwave background

- Phys.Rev.Lett. 78 (1997) 2054-2057
•
e-Print:
- astro-ph/9609169
•
DOI:
- 10.1103/PhysRevLett.78.2054

[2]

A Probe of primordial gravity waves and vorticity

Marc Kamionkowski
(
- Columbia U.
)
,
Arthur Kosowsky
(
- Harvard-Smithsonian Ctr. Astrophys. and
- Harvard U.
)
,
Albert Stebbins
(
- Fermilab
)

- Phys.Rev.Lett. 78 (1997) 2058-2061
•
e-Print:
- astro-ph/9609132
•
DOI:
- 10.1103/PhysRevLett.78.2058

[3]

CMBPol Mission Concept Study: Prospects for polarized foreground removal

et al.

- AIP Conf.Proc. 1141 (2009) 1, 222
•
e-Print:
- 0811.3915
•
DOI:
- 10.1063/1.3160888

[4]

Five-Year Wilkinson Anisotropy Probe Observations: Likelihoods and Parameters from the WMAP Data

J. Dunkley

- Astrophys.J. 180 (2009) 306-329

[5]

The Linear-Phase Triangular Facet Approximation in Physical Optics Analysis of Reflector Antennas

W.A. Imbriale
,
R.E. Hodges

[6]

Offset multireflector antennas with perfect pattern symmetry and polarization discrimination

C. Dragone

[7]

Unique reflector arrangement with very wide field of view for multibeam antennas

C. Dragone

[8]

Functional Description of Read-out Electronics for Time-Domain Multiplexed Bolometers for Millimeter and Sub-millimeter Astronomy

et al.

- J.Low Temp.Phys. 151 (2008) 3-4, 908-914
•
DOI:
- 10.1007/s10909-008-9772-z

[9]

Characterization and Modeling the Noise and Complex Impedance in Feedhorn-Coupled TES Polarimeters

J.W. Appel

[10]

Measurements of TES Bolometer Uniformity for CMB Polarimeter Arrays

J.E. Austermann

[11]

Optical Properties of feedhorncoupled TES polarimeters for CMB polarimetry

L.E. Bleem

[12]

Planar Orthomode Transducers for Feedhorn-Coupled TES Polarimeters

J. McMahon

[13]

Towards a large format TES array for CMB Polarimetry

K.W. Yoon