METIS PFM Polarimeter Calibration M Casti G Capobianco

METIS PFM Polarimeter Calibration M. Casti, , G. Capobianco, S. Fineschi INAF – Astrophysical Observatory of Torino (OATo), Italy 28/09/2017 METIS PFM Polarimeter Calibration 1

METIS PMP - Bandpass filter (580 -640 nm) [BP] - Quarter wave retarder [QW] - Achromatic Liquid Crystal Variable Retarder [ALCVR] - Analyzer [LP] 18/01/2016 TMTC Meeting 2

Polarimeter alignment scheme Detector 18/01/2016 TMTC Meeting 3

Polarimeter alignment scheme 18/01/2016 TMTC Meeting 4

Reference system (VL Fields) From Zemax Optical CAD I-COR_5. 4_vis. 0. zmx XZmx From: Metis coordinates memo (M. Romoli) X=0 o – Y=2. 9 o XILS ZZmx YZmx ZILS Fast axis orientation YZmx ZILS X=2. 9 o – Y=0 o YILS Fast axis orientation XZmx ZZmx XILS YILS

Polarimeter Reference Frame Linear Pre Polarizer 28/09/2017 VL Source METIS PFM Polarimeter Calibration 6

Polarimeter Reference Frame ZPILS YPILS XPILS ZILS YILS XILS 28/09/2017 METIS PFM Polarimeter Calibration 7

Polarization Flat Field Set-up Pre-polarizer Calibrated Diode Flat-field Panel

Polarimeter Modulation & Demodulation : LCVR retardance mi: set of 4 measurements i=0, 1, 2, 3 Theoretical LCVR retardances i = 0 , 90 , 180 , 270 : X=modulation matrix 9

Polarimeter Modulation & Demodulation Theoretical LCVR retardances i = 0 , 90 , 180 , 270 X+ = theoretical demodulation matrix 10

28/09/2017 METIS PFM Polarimeter Calibration 11

Prepolarizer @ 0 deg Where: k = a exp(- b V k) + c exp(- d V k) 28/09/2017 METIS PFM Polarimeter Calibration 12

Prepolarizer @ 45 deg 23/09/2017 METIS PFM Polarimeter Calibration 13

Prepolarizer @ 90 deg 28/09/2017 METIS PFM Polarimeter Calibration 14

Prepolarizer @ 135 deg 28/09/2017 METIS PFM Polarimeter Calibration 15

Prepolarizer @ 0 deg and 90 deg 28/09/2017 METIS PFM Polarimeter Calibration 16

Prepolarizer @ 0 deg and 90 deg 28/09/2017 METIS PFM Polarimeter Calibration 17

Prepolarizer @ 45 deg and 135 deg 28/09/2017 METIS PFM Polarimeter Calibration 18

Prepolarizer @ 45 deg and 135 deg 28/09/2017 METIS PFM Polarimeter Calibration 19

Retardance vs V 0 ltage Fitting model: k = a exp(- b V k) + c exp(- d V k) 28/09/2017 METIS PFM Polarimeter Calibration 20

Intensity vs Rotation curve

Intensity vs Rotation curve

Demodulation Matrix: Polarization efficiency:

Demodulation Matrix We considered the value of optical retardance obtained @ V = 14 V and we chose four voltages associated to 4 optical retardance angles separated by 90 deg Demodulation Matrix: Polarization efficiency:

Demodulation Matrix we considered the voltages associated to the following optical retardance angles : 90°, 180°, 270° and 360° Demodulation Matrix: Polarization efficiency:

Polarization Performances Air vs Vacuum Air 23/09/2017 METIS PFM Polarimeter Calibration 26

Polarization Flat-Fielding 23/09/2017 METIS PFM Polarimeter Calibration 27

ALCVR Modulation scheme (for CME detection) 45 0 90 135 Sect. 3 Sect. 2 Sect. 1 Sect. 4 Sect. 5 135 Sect. 1&5 90 Sect. 2&6 0 Sect. 3&7 45 Sect. 4&8 Linear polarizer Sect. 8 Sect. 6 Sect. 7 Polarization vector of the K-corona Polarization vector after rotation by PMP Linear polarizer acceptance axis 18/01/2016 TMTC Meeting 28

Conclusions • • Voltage set for max polarization efficiency Polarization performances in air and vacuum Voltage set vs CMS detection sectors (TBC) Polarization flat-fielding (work in progress) 23/09/2017 METIS PFM Polarimeter Calibration 29