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Blobrana


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Posts: 131433
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EBEX Balloon Borne Experiment
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Title: The EBEX Balloon Borne Experiment - Optics, Receiver, and Polarimetry
Author: The EBEX Collaboration: Asad M. Aboobaker, Peter Ade, Derek Araujo, François Aubin, Carlo Baccigalupi, Chaoyun Bao, Daniel Chapman, Joy Didier, Matt Dobbs, Christopher Geach, Will Grainger, Shaul Hanany, Kyle Helson, Seth Hillbrand, Johannes Hubmayr, Andrew Jaffe, Bradley Johnson, Terry Jones, Jeff Klein, Andrei Korotkov, Adrian Lee, Lorne Levinson, Michele Limon, Kevin MacDermid, Tomotake Matsumura, Amber D. Miller, Michael Milligan, Kate Raach, Britt Reichborn-Kjennerud, Ilan Sagiv, Giorgio Savini, Locke Spencer, Carole Tucker, Gregory S. Tucker, Ben Westbrook, Karl Young, Kyle Zilic

The E and B Experiment (EBEX) was a long-duration balloon-borne cosmic microwave background polarimeter that flew over Antarctica in 2013. We describe the experiment's optical system, receiver, and polarimetric approach, and report on their in-flight performance. EBEX had three frequency bands centered on 150, 250, and 410~GHz. To make efficient use of limited mass and space we designed a 115~cm^2sr high throughput optical system that had two ambient temperature mirrors and four anti-reflection coated polyethylene lenses per focal plane. All frequency bands shared the same optical train. Polarimetry was achieved with a continuously rotating achromatic half-wave plate (AHWP) that was levitated with a superconducting magnetic bearing (SMB). Rotation stability was 0.45~\% over a period of 10~hours, and angular position accuracy was 0.01~degrees. This is the first use of a SMB in astrophysics. The measured modulation efficiency was above 90~\% for all bands. To our knowledge the 109~\% fractional bandwidth of the AHWP was the broadest implemented to date. The receiver that contained one lens and the AHWP at a temperature of 4~K, the polarizing grid and other lenses at 1~K, and the two focal planes at 0.25~K performed according to specifications giving focal plane temperature stability with fluctuation power spectrum that had 1/f knee at 2~mHz. EBEX was the first balloon-borne instrument to implement technologies characteristic of modern CMB polarimeters including high throughput optical systems, and large arrays of transition edge sensor bolometric detectors with mutiplexed readouts.

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Blobrana


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RE: EBEX balloon
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McGill Cosmology Instrumentation Laboratory

Our team has started to arrive at McMurdo station, Antarctica, for the long duration stratospheric balloon flight of EBEX... Francois (PhD student) arrives this week, Kevin (PhD student) next week, and Matt (faculty) the following.
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Blobrana


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Title: EBEX: A balloon-borne CMB polarisation experiment
Authors: Britt Reichborn-Kjennerud (1), Asad M. Aboobaker (2), Peter Ade (3), Françcois Aubin (4), Carlo Baccigalupi (5), Chaoyun Bao (2), Julian Borrill (6), Christopher Cantalupo (6), Daniel Chapman (1), Joy Didier (1), Matt Dobbs (4), Julien Grain (7), William Grainger (3), Shaul Hanany (2), Seth Hillbrand (1), Johannes Hubmayr (8), Andrew Jaffe (9), Bradley Johnson (10), Terry Jones (2), Theodore Kisner (6), Jeff Klein (2), Andrei Korotkov (11), Sam Leach (5), Adrian Lee (10), Lorne Levinson (12), Michele Limon (1), Kevin MacDermid (4), Tomotake Matsumura (13), Xiaofan Meng (10), Amber Miller (1), Michael Milligan (2), Enzo Pascale (3), Daniel Polsgrove (2), Nicolas Ponthieu (7), Kate Raach (2), Ilan Sagiv (2), Graeme Smecher (4), Federico Stivoli (14), Radek Stompor (15), Huan Tran (10),
Matthieu Tristram (16), Gregory S. Tucker (11), Yury Vinokurov (11), Amit Yadav (17), Matias Zaldarriaga (17), Kyle Zilic (2), ((1) Columbia University, New York, NY, (2) University of Minnesota, Minneapolis, MN, (3) Cardiff University, Cardiff, United Kingdom, (4) McGill University, Montréal, Quebec, Canada, (5) Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy, (6) Lawrence Berkeley National Laboratory, Berkeley, CA, (7) Institut d'Astrophysique Spatiale, Universite Paris-Sud, Orsay, France, (8) National Institute of Standards and Technology, Boulder, CO, (9) Imperial College, London, England, United Kingdom, (10) University of California, Berkeley, Berkeley, CA, (11) Brown University, Providence, RI, (12) Weizmann Institute of Science, Rehovot, Israel, (13) California Institute of Technology, Pasadena, CA, (14) Institut National de Recherche en Informatique et Automatique, Universite Paris-Sud, Orsay, France, (15) CNRS, Laboratoire Astroparticule et Cosmologie (APC), Université Paris Diderot, Paris, France, (16) Laboratoire de l'Accélérateur Linéaire, Université Paris Sud, CNRS, Orsay, France, (17) Institute for Advanced Study, Princeton, NJ)
et al. (6 additional authors not shown)

EBEX is a NASA-funded balloon-borne experiment designed to measure the polarisation of the cosmic microwave background (CMB). Observations will be made using 1432 transition edge sensor (TES) bolometric detectors read out with frequency multiplexed SQuIDs. EBEX will observe in three frequency bands centred at 150, 250, and 410 GHz, with 768, 384, and 280 detectors in each band, respectively. This broad frequency coverage is designed to provide valuable information about polarised foreground signals from dust. The polarised sky signals will be modulated with an achromatic half wave plate (AHWP) rotating on a superconducting magnetic bearing (SMB) and analysed with a fixed wire grid polariser. EBEX will observe a patch covering ~1% of the sky with 8' resolution, allowing for observation of the angular power spectrum from \ell = 20 to 1000. This will allow EBEX to search for both the primordial B-mode signal predicted by inflation and the anticipated lensing B-mode signal. Calculations to predict EBEX constraints on r using expected noise levels show that, for a likelihood centred around zero and with negligible foregrounds, 99% of the area falls below r = 0.035. This value increases by a factor of 1.6 after a process of foreground subtraction. This estimate does not include systematic uncertainties. An engineering flight was launched in June, 2009, from Ft. Sumner, NM, and the long duration science flight in Antarctica is planned for 2011. These proceedings describe the EBEX instrument and the North American engineering flight.

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Blobrana


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The EBEX balloon was launched on the 11th June 2009.
EBEX launch 11
EBEX Launch, 6/11/09


EBEX is a balloon-borne polarimeter designed to measure the intensity and polarisation of the cosmic microwave background radiation. Measurements of the polarisation of the CMB could probe an inflationary epoch that took place shortly after the big bang and significantly improve constraints on the values of several cosmological parameters. EBEX will also provide critical information about the level of polarised Galactic dust which will be necessary for all future CMB polarisation experiments.

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First, what everyone is dying to know: No, we don't have the payload back yet. The soil near where EBEX landed is very loose and sandy, and the recovery truck actually got stuck, digging its rear tire into a nice hole about half the diameter of the tire and they had to call a tow truck to help pull it out. Recovery of the gondola is waiting on getting some heavy equipment (something with tracks, like a bulldozer or the like) to drag the recovery truck in so they can put the gondola on the trailer.
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