The High Altitude Observatory (HAO) at the National Center for Atmospheric Research (NCAR) The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are COSMO Large Coronagraph Preliminary Design Review Birefringent Filter Design and Polarimetry Steven Tomczyk National Center for Atmospheric Research Boulder, Colorado – Nov 16, 2015
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The High Altitude Observatory (HAO) at the National Center for Atmospheric Research (NCAR)The National Center for Atmospheric Research is sponsored by the National Science Foundation.
Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
COSMO Large CoronagraphPreliminary Design Review
Birefringent Filter Design and PolarimetrySteven Tomczyk
National Center for Atmospheric Research
Boulder, Colorado – Nov 16, 2015
COSMO PDR (November 16-17, 2015) Birefringent Filter Design and Polarimetry
Birefringent Filter Design
Relevant documents:
COSMOLC-DE-7001 (Tunable Filter Design and Development)
𝜀 𝜀 /𝑝𝐿 𝜀 /𝑝𝐿 𝑎 ]Following Ichimoto et al., 2008, we need to calibrate the response matrix elements to an accuracy of
Response matrix relates observed and actual Stokes vector
ε = 10-4 (to meet 1 G magnetic field error),a = 0.05 (following Ichimoto et al.),PL = maximum linear polarization = 0.1,PC = maximum circular polarization = 10-3 (corresponding to 10 G).
COSMO PDR (November 16-17, 2015) Birefringent Filter Design and Polarimetry
Polarimetry
COSMO LC needs 10-4 precision in V/I, not accuracyV is anti-symmetric wrt line center, need amplitude to determine magnetic field (Lin, Kuhn, Coulter, 2004)
Can calibrate I > Q,U,V using data itself, look in continuum where polarization is absent (e.g. Lites and Ichimoto, 2013)
COSMO PDR (November 16-17, 2015) Birefringent Filter Design and Polarimetry
Calibration
Insert calibration optics with known Mueller matrixPolarizerRetarderPolarizer + RetarderRotate them
,
References:Elmore, D.F., “A polarization calibration technique for the advanced stokes polarimeter”, 1990, NCAR Technical Note NCAR/TN-355+STR, NCAR, Boulder, Colorado.Ichimoto, et al., “Polarization Calibration of the Solar Optical Telescope onboard Hinode”, 2008, Solar Phys. 249, 233.
COSMO PDR (November 16-17, 2015) Birefringent Filter Design and Polarimetry