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The Cylinder Radio Telescope: Observing the CMB

The Cylinder Radio Telescope: Observing the CMB. Paul A. Fleiner Ph 70 Popular Presentation May 10, 2011. Outline. Radio Astronomy 21cm Baryon Acoustic Oscillations ( BAOs ) Cylinder Telescope Prototype Possible Sites Challenges Looking Ahead. Radio Astronomy: The Beginning.

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The Cylinder Radio Telescope: Observing the CMB

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  1. The Cylinder Radio Telescope:Observing the CMB Paul A. Fleiner Ph 70 Popular Presentation May 10, 2011

  2. Outline • Radio Astronomy • 21cm Baryon Acoustic Oscillations (BAOs) • Cylinder Telescope • Prototype • Possible Sites • Challenges • Looking Ahead

  3. Radio Astronomy: The Beginning • Early Attempts • Nikola Tesla, Oliver Lodge • Attempted to observe radio emissions from the sun • Unsuccessful • Technical Limits

  4. Radio Astronomy • First RA observations • Karl Jansky, 1930s • Bell Labs

  5. Jansky’s Discovery • Investigating source of interference in short-wave trans-Atlantic transmissions • Initially thought source was solar • Happened every 23 hours, 56 minutes • Actually Milky Way

  6. Modern Radio Telescopes • Very Large Array (VLA) • New Mexico, 1980 • $78.5m, ~$10,000/m2 • Square Kilometer Array (SKA) • Australia, 2024 • >$2b, $1,000/m2 (Target)

  7. How do they work?

  8. What We “See” • Hydrogen atom moving away from us is redshifted: • f=700MHz • λ=42cm • Hydrogen atom at rest: • F=1420MHz • λ=21cm

  9. Baryon Acoustic Oscillation (BAO) • Method of tracking expansion of universe • About 400,000 years after Big Bang • Universe expanded, temperature cooled • Electrons and protons combine to form H • Photons no longer Thompson scattered • Observing these photons gives us a “ruler” for measuring expansion

  10. BAO • Can use the ruler to plot the redshift • Can create a 3D mapping of the universe through time • Measure the expansion • Will help us quantify “dark energy”

  11. Cylinder Radio Telescope • Popular from 1960-1980 • Abandoned in favor of devices with cryogenically cooled pre-amps • Illinois 400 ft Telescope, circa 1960

  12. CRT Enabling Technology • Low Noise Amplifiers (LNAs) are much cheaper • T<<300K • Increased capabilities of Analog to Digital Converters (ADCs) • Better Digital Signal Processing • GPUs, FPGAs • More sophisticated FFTs (N log N) • High speed, low power, low cost • Reduces the cost to ~$100/m2

  13. CRT Design • Parabolic half-cylinders • Focuses radio waves radially inward • Strikes axial array of antennas • Key Requirements • High Resolution • Overall array size, time observed • Large Sky Coverage • Number of channels • Large Redshift Range • Bandwidth

  14. CMU Prototype • Built by Prof. Peterson’s group in Pittsburgh

  15. Goal Design • Array of 10 cylinders • 10m wide, 100m long • Coverage • 20,000 sq. degrees • Frequency Range • 300-1500MHz • Bandwidth • >200MHz

  16. Challenges • Synchrotron frequency, free-free emission • Total 21cm signal is ~300µK • 21cm BAO signal is only ~300nK • Instrument Calibration • Environment Calibration • RF Interference • Far from power lines, most electronics

  17. Possible Sites • Several in Morocco

  18. Moving Forward • Model removal of foreground noise • Build 2 to 3 cylinders • 10m wide, 50m long • Set up larger prototypes in less noisy place • Actually remove noise

  19. Acknowledgements • Professor Jeff Peterson, CMU • Kevin Bandura, PhD Candidate • Bruce Taylor, Communication and Facilities Consultant

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