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

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

science drivers : others

black holes in obscured AGNs

IMF in starbust galaxies

damped Ly-alpha systems

etc...

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!!

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

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

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

polarimeter: overview

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

spectrograph optics: overview

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

cryogenic tank: overview

cryogenic tank: overview

cryogenic tank: overview

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 (?)

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)

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!!