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BICEP Modern Experimental Cosmology: New tools for CMB Astronomy Yuki Takahashi

BICEP Modern Experimental Cosmology: New tools for CMB Astronomy Yuki Takahashi. 2007/2/6. BICEP. Instrument design overview Characterization Detectors (polarization sensitive bolometers) Time constants Relative gains Polarization orientation / cross-polar leakage

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BICEP Modern Experimental Cosmology: New tools for CMB Astronomy Yuki Takahashi

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  1. BICEPModern Experimental Cosmology: New tools for CMB AstronomyYuki Takahashi 2007/2/6

  2. BICEP • Instrument design overview • Characterization • Detectors (polarization sensitive bolometers) • Time constants • Relative gains • Polarization orientation / cross-polar leakage • Optics (feedhorns, filters, lenses, baffles) • Spectral profile • Beam • Sidelobe profile • Observation techniques • Preliminary results

  3. BICEP overview (55L/110L)

  4. Bolometers Neutron Transmutation Doped Ge G ~ 60 pW/K τ = C/G ~0.4 V

  5. Time constants(for de-convolving time streams) τ ~ 20 ms Relative Gains (for differencing / adding) to < 0.3% accuracy Elevation nod T(q) = Tatm/sin(q) Tatm~10K http://www.pages.drexel.edu/~brooksdr/DRB_web_page/papers/UsingTheSun/airmass.gif

  6. Polarization Orientation(±1°, to prevent E=>B mixing) Crosspolar Leakage (=> degraded efficiency) e : 5~10 %

  7. Feedhorns, metal-mesh filters • Blocks l shorter than: • 2.7 mm for 100 GHz • 1.7 mm for 150 GHz • 2 blocker filters.

  8. Focal Plane& 2 Lenses

  9. Beams (for making maps)Pointing, widths, ellipticity Spectral profile (measure any mismatch to account for different slopes between CMB and atmosphere) Used Fourier Transform Spectrometer. 100 GHz 150 GHz

  10. Forebaffle + Ground Screen to attenuate diffracted ground radiation

  11. Mount (AZ, EL, Boresight)

  12. Chosen Fields Galactic foreground w/ Eta Carina: 12.5% Galactic calibration: ~3% CMB field: 75%

  13. Observation Strategy Total CMB efficiency ~ 54%

  14. Temp (mK) BICEP WMAP (“observed” w/ BICEP)

  15. E-mode (mK) 100 GHz - 150 GHz 100 GHz + 150 GHz

  16. Refrigerator • 4He/3He/3He sorption • 1~2 / 0.35 / 0.25 K

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