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Instrument Sketches. David Elmore National Center for Atmospheric Research. May 2003. Instruments. K-coronagraph Linear polarization from Thomson scattering Whole corona Successor to MLSO K-coronameters Prominence Magnetograph Hanl é effect in Helium d3

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Instrument sketches
Instrument Sketches

  • David Elmore

  • National Center for Atmospheric Research

May 2003


Instruments
Instruments

  • K-coronagraph

    • Linear polarization from Thomson scattering

    • Whole corona

    • Successor to MLSO K-coronameters

  • Prominence Magnetograph

    • Hanlé effect in Helium d3

    • Field of view comparable to prominence dimensions

  • Coronal Magnetograph

    • Stokes parameters in Fe XIII due to Zeeman effect and resonance scattering

    • Approximately 1 solar radius field

  • Keep current HeI (CHIP) and H-a (PICS)


Why now
Why now?

  • Scientific interest

  • High speed, high quantum efficiency detectors are and are becoming available – more photons/pixel-sec

  • Fast, efficient, simple polarization modulators are available

  • Inexpensive video processing electronics


Koronagraph requirements
Koronagraph – requirements

  • Possible requirements

    • Field of view ~3 D0

    • Spatial resolution ≤ 10 arc-seconds

    • Polarimetric sensitivity 5 x 10-10pB0

    • Time cadence ≤ 180 seconds (Mk4 SN in < 10sec)

  • Derived parameters

    • Number of pixels ~1152 x ~1152

    • Aperture 32mm @775nm, 91mm @ 2.2mm

    • Background/Signal 40,000 @ 10 mB0 sky, 0.5 eff.

    • Captured flux 4 x 106 e-/pixel-sec-beam

    • Detector full well 400,000 e- @50fps & 50mB0 sky

    • Readnoise < 200 e- @ 5mB0 sky


Koronagraph detectors
Koronagraph -- Detectors

  • Line array

    • Aperture X band pass is too large ~1 meter aperture

  • CCD area arrays

    • Frame rate X full well X QE is insufficient

  • Hybrid arrays

    • Rockwell HyVisI: 2 beams * 350,000 e-full well * 50 fps OK

    • C3Po: 1 beam * 700,000 e- full well * 50fps OK


Koronagraph telescopes
Koronagraph -- Telescopes

  • Internally Occulted Lyot Coronagraph

    • Reflector

      • Achromatic, therefore good occulting and simple re-imaging

      • Polarization of off-axis system is a concern

      • Information on experience with ground-based reflecting coronagraphs is requested (thank you Rainer)

    • Refractor

      • Demonstrated low scatter

      • Possibly larger size needed to get narrow pass band and good occulting

      • Air-spaced doublet is a possibility


Koronagraph wavelength
Koronagraph -- Wavelength

  • Very red (800nm)

    • High QE silicon detectors

    • Good ability to flat field

  • K-band (2.2mm)

    • Darker sky compared to corona compared to 800nm

    • More telescope diffraction therefore larger detector dynamic range needed

    • What will be used for polarization modulator?


Koronagraph starting point
Koronagraph – Starting point

  • On axis refractor

    • 100mm objective

    • 1500mm focal length

    • 22.5nm pass band @ 800nm

    • Dual beam HyVisI or C3Po

    • Ferroelectric liquid crystal polarization modulator

    • 2.8 m total length (Mk4 is 4 m)

    • Video processing to remove aerosols







Prominence magnetograph requirements
Prominence Magnetograph – Requirements

  • Possible requirements

    • Field of view 0.25 R0 x 0.125 R0

    • Spatial resolution ≤ 4 arc-seconds

    • Time cadence ≤ 10 seconds

    • Spectral resolution 20pm @ 587.6nm

    • Stokes I, Q, U, and V

  • Derived parameters

    • Number of spatial samples ~128 x ~64

    • Spectral sample ~ 10pm


Prominence magnetograph sketch
Prominence Magnetograph – Sketch

  • Spectrograph following Haosheng Lin’s concept

    • 128 x 64 fiber array

    • 8 x 8 spectra

    • 0.35nm spectral range, but <0.175nm pre-filter

  • Telescope is a clone of Koronagraph

  • Detector C3Po

    • 1024 x 1024 pixels

    • 128 spatial samples

    • 128 spectral samples (3pm each)


Prominence magnetograph telescope looks a lot like koronagraph
Prominence Magnetograph – Telescope(looks a lot like Koronagraph)

Spectrograph

Fibers



Coronal magnetograph requirements
Coronal Magnetograph – Requirements

  • Possible requirements

    • Field of view ~ 1 R0

    • Spatial resolution ≤ 4 arc-seconds

    • Time cadence ≤ 10 minutes

    • Stokes parameters I, Q, U, V

    • Spectral resolution ≤ Line width

  • Derived parameters

    • Objective diameter is set by filter diameter, field of view, and filter acceptance angle


Coronal magnetograph starting point
Coronal Magnetograph – Starting Point

  • Telescope

    • Field of view ~ 1 R0

    • Spatial resolution ~ 4 arc-seconds

    • Time cadence ≤ 1 hour

    • Stokes parameters I, Q, U, V

    • Optimize spatial spectral data cube through use of a tunable filter

  • Derived parameters

    • Filter pass band comparable to lines, ~0.14nm

    • 512 x 512 pixels

    • 40cm or greater objective


Coronal magnetograph sketch
Coronal Magnetograph – Sketch

Ray Smartt’s One Shot design with larger objective and Steve’s COMP section

COMP section

40cm asphere

3.6 meters


Coronal magnetograph comp section
Coronal Magnetograph – COMP section

Camera Lens

LCVR Tunable Lyot filter

Occulter

Telecentric Lense


Coronal magnetograph imaging
Coronal Magnetograph – Imaging

Lyot Filter

Wollaston

IR Detector

Camera Lens

Lyot Stop




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