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Preliminary Design of the Spectropolarimeter for Arago

Martin Pertenaïs1,2

Coralie Neiner1 (PI), Laurent Parès2, Jean-Michel Reess1, Pernelle Bernardi1, Frans Snik3, Gerard van Harten3

1Paris Observatory (FR)2IRAP-CNRS, University of Toulouse (FR)

3Leiden Observatory, Leiden Univsersity (NL)

Punta Leona 2nd December 2014

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François Arago

1811 : Arago discovered rotary polarization experimentally (Quartz)

Polarimetry was born !!

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Scientific goals

• What is the life cycle of matter ? (star formation, evolution and death) ISM Characterization Young (PMS) stars in accretion All kinds of stars (Massive stars, Solar-like stars…) Late stages of evolution (Supergiants, supernovae,…)

• How do stars impact the formation of planets and the emergence of life? Star-Planet interactions (stellar wind, magnetic interaction,…) Space weather (irradiation of the planet by the star,…)

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Specifications

Specification RequirementSpectral range [119 nm ; 888 nm]UV Resolution 25 000

Visible Resolution 35 000

S/N 100Typical exp. time 30 min (OBA stars, V=7)

1h (FGK stars, V=7)Target Magnitude V=3-10Vrad accuracy 1 km.s-1 (in absolute)

0.1 km.s-1 (for magnetic fields measurement)Polarization accuracy 10-3

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Instrument Scheme

Telescope Polarimeter Spectro-graph

VIS Detector

UV Detector

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Telescope

Spec. :

- SNR 100 - V=7 Star - 30 min exposure time

Þ 1.3m diameter Cassegrain telescope

F/13

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Instrument Scheme

Telescope Polarimeter Spectro-graph

VIS Detector

UV Detector

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PolarimeterAim : create a polychromatic polarimetric modulator

• 4 MgF2 stacked wave plates with fast-axis angle and thicknesses:

(a1,d1), (a2,d2),(a3,d3),(a4,d4)

• Optimization on these 8 variables

• The stack of the 4 plates takes 6 different angular positions (0°,30°,60°,90°,120° et 150°)

d1 d2 d3 d4

a1 a3a2 a4

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PolarimeterAim : create a polychromatic polarimetric modulator

• Definition of a demodulation matrix D such as: Sin=D.Iout

• The extraction efficiencies of the Stokes parameters *:

• T ≈57.7%

• The extraction is achromatized and not the retardance of the plates!

* Optimum modulation and demodulation matrices for solar polarimetry, JC del Toro Inista and Collados (2000)

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Polarimeter

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Instrument Scheme

Telescope Polarimeter Spectro-graph

VIS Detector

UV Detector

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Spectrograph

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Instrument Scheme

Telescope Polarimeter Spectro-graph

VIS Detector

UV Detector

Classical CCD detector (13µm pixel pitch)

MCP Detectors (20µm pixel pitch)

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To take home

• High-resolution spectropolarimetry

• Precise Full Stokes (IQUV) measurement

• From FUV (119 nm) to NIR (888 nm)

• Exciting science !

Thank you for your attention !

Contacts : martin.pertenais@irap.omp.eu coralie.neiner@obspm.fr

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Thank you for your attention !

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SNR figures

SNR

Wavelength (nm)

SNR

Wavelength (nm)

T=9790 KMag = 10Exposure Time = 30min

T=16000 KMag = 7Exposure Time = 30min

Considering an optical transmission in the UV of 3% and 10% in the VIS, and a quantum efficiency in the UV of 35% and 70% in the visible

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Spectral band Minimum SNR Magnitude V Spectral type Maximum exposure time [min]

Visible

[390-890] nm100 7 all 30

UV

[119-320] nm100 7 OBA 30

UV

[119-320] nm100 7 FGK 60

UV

[119-320] nm100 10 Chromospheric emission

lines of M dwarfs 60

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Birefringence MgF2

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Focal planes

A p e r t u r e F u l l X W i d t h : 3 0 . 0 0 0 0A p e r t u r e F u l l Y H e i g h t : 3 0 . 0 0 0 0

Scale: 32.0000 Millimeters

U V M A G _ c o m p l e t . Z M XC o n f i g u r a t i o n s 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 1 0 , 1 1 , 1 2

F o o t p r i n t D i a g r a mU V M A G M o n t a g e p u p i l l e b l a n c h e2 0 / 1 1 / 2 0 1 4S u r f a c e 9 6 : R a y X M i n = - 9 . 6 2 4 1 R a y X M a x = 1 2 . 1 3 5 4R a y Y M i n = - 1 2 . 1 1 2 9 R a y Y M a x = 1 3 . 4 5 1 1M a x R a d i u s = 1 7 . 6 4 4 4 W a v e l e n g t h = A l l

% r a y s t h r o u g h = 9 8 . 4 2 %

A p e r t u r e F u l l X W i d t h : 1 2 0 . 0 0 0 0A p e r t u r e F u l l Y H e i g h t : 1 4 . 0 0 0 0

Scale: 14.2000 Millimeters

U V M A G _ c o m p l e t . Z M XC o n f i g u r a t i o n s 1 3 , 1 4 , 1 5 , 1 6 , 1 7 , 1 8 , 1 9 , 2 0 , 2 1 , 2 2 , 2 3 , 2 4 , 2 5 , 2 6 , 2 7 , 2 8

F o o t p r i n t D i a g r a mU V M A G M o n t a g e p u p i l l e b l a n c h e2 0 / 1 1 / 2 0 1 4S u r f a c e 9 6 : R a y X M i n = - 4 9 . 4 1 9 6 R a y X M a x = 4 9 . 6 5 6 1R a y Y M i n = - 5 . 4 4 6 9 R a y Y M a x = 5 . 2 6 9 1M a x R a d i u s = 4 9 . 9 3 1 3 W a v e l e n g t h = A l l

% r a y s t h r o u g h = 9 8 . 4 2 %

Frame size 30 x 30 mm

UVFrame size 120 x 14 mm

100 mm

Visible :

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Back-up polarimeter

x

x 2x ¿)()tan(6

nx