spirou : a nir chelle spectropolarimer for cfhtspirou: instrument concept a cass module featuring: a...
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SpIRou: a nIR échelle spectropolarimer for CFHT
JF Donati et alLATT: Petit, Paletou
LAOG: Bouvier, ForveilleLESIA: CatalaLAM: MoutouUK: Cameron
TW: TrungC: Wade
CFHT: AlbertES: Martin
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science drivers : examples exoplanets orbiting very-low-mass stars
star forming regions
magnetic fields of very cool stars
stellar environments/envelopes
higher sensitivity to earth-like planetsplanet formation in new regime of star/disc mass
frequency of planets around low-mass stars~400 stars (up to M9)
better contrast & better view of embedded objectsclumps and magnetic fields in protostellar discsangular momentum evolution & planet formation
>200 stars (mK<11)
better sensitivity & molecular linesdynamo processes in fully convective stars
angular momentum evolution & planet formation>200 stars (mK<11)
better sensitivity & new spectral diagnosticsgeometry & chemical composition of diffusing envelope
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science drivers : others
black holes in obscured AGNs
IMF in starbust galaxies
damped Ly-alpha systems
etc...
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a scientific nicheexisting instruments
in construction or planned
Phoenix/Gemini: R=75K with 0.17” slit, 0.8-2.5μm, cov: 0.02μmNIRSPEC/Keck2: R=25K with 0.40” slit, 0.9-5.5μm, cov: 0.2μm
IRCS/Subaru: R=20K with 0.14” slit, 1.0-3.0μm, cov: 0.2μmCRIRES/VLT: R=40K with 0.5” slit, 1.0-5.0μm, cov: 0.02μm
GIANO/TNG: R=50K with 0.50” slit, 0.9-2.5μm, full cov, 2009?PRVS/Gemini: R=50K, fiber fed, 0.9-1.8μm, full cov, 2010?
NAHUAL/GTC: R=50K with 0.175” slit, 0.9-2.4μm, full cov, 2011?
no spectropolarimetry!!
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SpIRou: instrument concept
a Cass module featuring:
a cryogenic spectrograph featuring:
an atmospheric dispersion corrector (ADC)an image stabilising module (tip-tilt)
all usual spectroscopic calibration facilitiesan achromatic polarimeter
a fiber bundle feeding the spectrograph
injection module w/ image slicer (and fibre scrambler?)a large cryostat cooled at 75 K
complete spectrograph optics (collimators, grating, Xdisp, camera, CCD)
goal performances: 0.9-2.4μm, full coverage in 1 exposure @ R=50K15% throughput (everything included)
polarimetric capabilities & precise RVs
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Cass module: overview
transmission tip-tilt:
viewing/guiding module:
use tiltable glass plate to correct image motionscollects light in the L band w/ pickup plate
corrects @ 50 Hz and delivers median seeing < 0.65”
checks polarimeter entrance pinholecorrects low-frequency image drifts
ADC: corrects atmospheric refraction up to airmass 2.7
calibration facilities: halogen and thorium lamps for calibrationsprovide simultaneous thorium spectrum
mostly similar to ESPaDOnS
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polarimeter: overview
focal reducer:
achromatic analyser:
triplet pair converting f/8 beam to f/3.5
1 fixed quarter-wave Fresnel rhomb 2 rotating half-wave rhombs
1 wollaston prism
entrance aperture: 1.5” circular pinhole in tilted mirror collects 90% of incoming stellar light
remaining light reflected towards viewing/guiding module
optical fibre bundle: 2 polarisation fibres + 1 reference fibreultra-low OH silica fibre (100/110μm core/clad)
30m fibre: 80% @ 2μm, 50% @ 2.2μm, a few % @ 2.4μmscrambler?
mostly similar to ESPaDOnS
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polarimeter: overview
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spectrograph optics: overview
diffraction grating:
2 parabolic off-axis collimators:
23.2 gr/mm w/ size 154x306mmfull domain w/ orders #83 (0.92μm) to #32 (2.4μm)
single parent (f=120cm, d=60cm)pupil size 15cm
light injection module: Bowen/Walraven slicer providing 3slices/fiberf/3.6 to f/8 focal reducer
prism Xdisperser: minimum/average interorder distance 0.65/0.75mm
R=50K, complete coverage up to 2μm (84% complete @ 2.4μm)
camera: working @ f/2, f=30cm, d=17cm, psf < 18μm over 10° fov
detector: 2kx2k hawaii-2 detector, 18μm square pixels
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spectrograph optics: overview
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cryogenic tank: overview
optical bench: mounted isostatically on a hexapod systemacting as tank for LN2, goal stability of 0.01°
inner structure w/ cells & floors for homogeneous filling4mm aluminium cover on which optics is mounted
cooling time 1.5d, using 400 l of LN2maintain cold with 22 l/d of LN2
heaters to ensure a warm-up time of ~1d
cryogenic tank: 1.3x1.9m stainless steel cylinder in 2 partsstandard 30-layer thermal shield
same as GIANO
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cryogenic tank: overview
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cryogenic tank: overview
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cryogenic tank: overview
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expected performances
peak total throughput: ~15%
S/N=100 in 1hr @ mJ=13 and mK=12
S/N=10 in 1hr @ mJ=15.5 and mK=14.5
polarimeter+fiber+slicer: ~40%spectrograph+detector: ~40%
detector noise: ~20e-
RV=20m/s in 20min @ mH=11-13 (?)
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pending questions
IR thermal emission?
cryogenic tank?
spectrograph optical design? dioptric vs. catadioptric camera @ 75Kglass for Xdisperser
image quality
include all spectrograph or only camera & detectortemperature stability
simpler designs
cool slicer optics, fiber and polarimeter?drop K band (or part of it)
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agenda & budgetagenda: ~2013
budget: ~2 M€
work share
may 2007: PDR for CFHT Users’ meeting2009: FDR & funds2012: acceptance
2013: implementation @ commissionning @ CFHT
detector: 0.5 M€optics: 0.7 M€
mechanics: 0.5 M€control & overheads: 0.2 M€
France: LATT/OMP - LAOG/OSUG - LESIA/OPMTaiwan - UofM? - UH? - CFHT?
all suggestions welcome!!