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Detection Methods

Detection Methods. Coherent ↔ Incoherent Photon Detection ↔ Bolometric Photon Counting ↔ Integrating. Radio Telescopes. Typical Designs Heterodyne Receivers. Jansky’s First Radio Telescope 1933. Grote Reber: 1937 Radio Telescope. The Arecibo Radio Telescope. Heterodyne Receivers.

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Detection Methods

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  1. Detection Methods • Coherent ↔ Incoherent • Photon Detection ↔ Bolometric • Photon Counting ↔ Integrating

  2. Radio Telescopes • Typical Designs • Heterodyne Receivers

  3. Jansky’s First Radio Telescope 1933

  4. Grote Reber: 1937 Radio Telescope

  5. The Arecibo Radio Telescope

  6. Heterodyne Receivers • Mix signal and local oscillator • Mixed signal contains “intermediate frequency” f_signal – f_local but also the sum of the frequencies

  7. Heterodyne Signal Detection

  8. MM and Sub-MM Telescopes • Use both coherent and incoherent detection • Heterodyne receivers for emission-lines • Mostly bolometers for continuum

  9. Millimeter Valley on Mauna Kea

  10. NGC 6334

  11. SMA Receivers

  12. Bolometers • Absorb and thermalize photons • Measure temperature change • Balance between heating and cooling results in long time constants • Typically used in chopped operation

  13. Transition Edge Sensors: Extreme sensitivity to small temperature changes allows to build very sensitive bolometer arrays

  14. Photocathods • The photoelectric effect • Quantum nature of light • Photomultipliers, channel plates …

  15. Photocathod Devices • Cathods • Photomultiplier • Image intensifiers • Microchannel plates

  16. Physics of Semiconductors Basic Quantum Physics Solids Semiconductors PN Junctions

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