Odeda Bridges • Sep 11, 2014 • 394 Views
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 • 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? • 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 • 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 • 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 • 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 • 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 • 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 • 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 • 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) Spectrograph Fibers
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 • 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 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 Camera Lens LCVR Tunable Lyot filter Occulter Telecentric Lense
Coronal Magnetograph – Imaging Lyot Filter Wollaston IR Detector Camera Lens Lyot Stop