Euclid/NISP grism qualification model AIT/AIV campaign: optical, mechanical, thermal and vibration tests

Transcription

1 Euclid/NISP grism qualification model AIT/AIV campaign: optical, mechanical, thermal and vibration tests 18/10/2016 Paper 61 ICSO Biarritz Amandine Caillat a, Anne Costille a, Sandrine Pascal a, Christelle Rossin a, Sébastien Vives a, Benjamin Foulon a, Patrice Sanchez a a Aix Marseille Université, CNRS, LAM (Laboratoire d'astrophysique de Marseille) UMR 7326, 13388, Marseille, France

2 2 Outline Introduction: Euclid space mission, NISP instrument & Grisms Euclid/NISP grisms general description and AIT/V philosophy Grisms optical specificities and manufacturing process Optical tests setups and performances measured on the grism EQM Focus on transmitted efficiency and WFE performances

3 3 Introduction: Euclid space mission Scientific objectives : Dark matter and energy exploration Universe accelerated expansion understanding Millions of galaxies infrared images and spectra needed to reconstruct the 3D map of the Universe Slitless spectroscopy using GRISMs Large field of view high resolved images Position (x,y) of each galaxy on the sky Each galaxy image is dispersed Distance (z) of each galaxy through redshift measurement

4 4 Introduction: Euclid/NISP Instrument Near Infrared SpectroPhotometer 2 rotated wheels: 3 filters for NIR photometry 4 grisms for NIR slitless spectroscopy: 2 spectral bands: nm and nm 3 orientations for nm NISP Structural and Thermal Model Grism glued into its mount ring Rotating wheel with four grisms Grisms development is under LAM responsibility

5 NISP Grisms general description and AIT/V philosophy Optics and mechanics manufactured separately then glued together Mechanical design, vibration and cryo tests done at LAM Optical specifications and verification tests done at LAM 5

6 6 NISP Grisms optical specificities 4 optical functions in 1 grism: Spectral dispersion + no deviation at one λ grating engraved onto a prism hypotenuse Spectral wavefront correction curvature of the grating lines not straight neither parallel Focus curvature of the filter face (+ co-focus required between all grisms and filters) Spectral filtering multilayer (~100) filter deposited on the curved face of the prism Complex manufacturing process Parameter Specification Shape Prismatic with the grating on the hypotenuse and the other face (filter) curved and convex Full diameter 140 +/ mm Clear aperture diameter 136 mm Thickness at the center 12 mm +/ mm Angle between the two faces / (+/- 2 arcmin) Spectral band pass range nm with 100nm for transition to out of band Mean transmitted efficiency on >65 % in order 1 and > 1% in order 0 < in [ ] nm Out of band blocking range and < in [ ] nm levels < in [ ] nm Mean pitch P 72.6±1 µm Groove Height H / µm Line shape Curve defined by "binary 1" surface in Zemax Curvature radius of the filter face mm CX +/ fringes at 633 nm SFE of the filter face on Zernike 5- RMSi < 15 nm Defocus on the grating face (SFE + < 0,5 fringes at 633nm SFE of the grating (SFE + grating RMSi<30nm Filter and gluing effect on SFE of <5 fringes at 633nm, symmetrical on both surfaces Tight budgets for efficiency and WFE distributed between each optical function

7 7 NISP grisms manufacturing process of the optics 1. Parallel plate (Φ150mm) supplied by TRIOPTICS 2. Grating (Φ136mm) made by SILIOS TECHNOLOGIES 4 suppliers work on 1 component Each optical part specified, verified and validated separately 7 months / grism ~100k / grism Transmitted efficiency Grating SFE and focus 3. Prism (Φ140mm) made by WINLIGHT OPTICS Both faces SFE and focus 4. Filter (Φ136mm) made by BALZERS OPTICS Transmitted efficiency Both faces SFE and focus

8 8 Spectral efficiency measurement setup Goal: Measure the spectral transmission of the grism in orders 0 and 1 Spectrophotometer Perkin Elmer Lambda 1050 = NIR source and detector Specific fibered bench to deal with: Grating dispersion and beam deviation Grating + curved filter face chromatic defocus Grism to be measured with a 90mm diameter collimated beam Spectrophotometer OF1 Φ=0,6mm NA=0,22 GRISM P1 F=300m m L1 F=500m m OF2 Φ=1mm NA=0,22 Measured after grating on 90mm diameter on the center Measured after filter manufacturing, on the center and the edges with AOI=0 and ±8

9 Spectral Efficiency of the grism EQM Order 1 on 1250nm-1850nm: min efficiency = 71% (>65% specified), max efficiency = 89% Order 0 on 1250nm-1850nm: average efficiency = 2% (>1% specified) Spectral transmission uniformity better than 1 %, no shift of the spectral bandpass Amandine.caillat@lam.fr 9

10 10 SFE of the Grating face measurement setup Goal: Measure the WFE reflected in order 1 in the visible to be compared to Zemax theory Several reflected orders measured (the most contrasted) in order to: Improve the accuracy Distinguish between substrate and grating contributions Linear fit of each aberration vs order # plot gives: Linear coefficient = Grating contribution Offset = Substrate contribution Fizeau phase-shifting interferometer (λ=633nm) Expander φ100=>150mm Reference plane φ150mm Aberration Zernike coefficients values evolve linearly with the order # GRISM grating face φ 150mm or φ 140mm Measured after each manufacturing step: grating, prism, filter and gluing Tip/Tilt/Rotation Mount

11 11 Grating function of the EQM Grism (1) Example of one individual measurement in the reflected order 6 Interferogram Phase Map Zernike coefficients 10 measurements in each reflected order: Decomposed on Zernike basis Average of each Zernike coefficient one point per order and per aberration unit: nm Measurement Theory Delta Budget Focus -181,9-183,5 1,6 <45 nm X astig 19,6 22,6 3,0 N/A Y astig 0,0-0,5 0,5 N/A X Coma -1,7 0,7 2,4 N/A Y Coma -2,0 0,0 2,0 N/A Spherical -45,1-45,4 0,3 N/A X Trefoil 4,8 5,3 0,5 N/A Y Trefoil 1,4 1,9 0,5 N/A RMS 188,7 190,7 6,3 N/A RMSi 50,2 52,0 6,1 < 30 nm Grating function is within specification for focus and for SFE

12 Grating function of the EQM Grism (2) Example of one individual measurement in the reflected order 6 Interferogram Phase Map Zernike coefficients 10 measurements in each reflected order: Decomposed on Zernike basis Average of each Zernike coefficient one point per order and per aberration unit: nm After grating After prism After filter After gluing Max diff Focus -181,9-183,1-180,5-182,3 2,6 X astig 19,6 21,6 23,3 21,9 Y astig 0,0 0,9 1,8 2,0 X Coma -1,7 2,0-5,5-2,4 Y Coma -2,0 0,2 1,2 1,6 Spherical -45,1-44,9-45,0-44,4 X Trefoil 4,8 5,4 6,0 6,3 Y Trefoil 1,4 2,3 2,1 2,8 RMS 188,5 189,9 187,6 189,1 2,2 RMSi 49,5 50,2 51,4 50,2 1,9 Grating function did not evolve along the manufacturing process Amandine.caillat@lam.fr 12

13 13 Grating face SFE of the EQM Grism After Grating After Filter After Gluing Diff after filter Diff after gluing focus ,1 484, ,1 466,595 X astig , ,98 Y astig -4,45-3,5-40,482 0,95-36,032 X Coma -2,45 58,5 43,542 60,95 45,992 Y Coma -13, ,935-4,65 12,415 Spherical -10,4-2,1-4,426 8,3 5,974 X Trefoil -2,8-3,65-14,6045-0,85-11,8045 Y Trefoil 0,8 2,15 74,565 1,35 73,765 Grating face SFE evolution: Focus and coma added by filter Astigmatism and trefoil added by gluing Results in accordance with previous measurements on prototypes

14 14 SFE of the filter face measurement setup Goal: Control the filter focus and SFE evolution along the manufacturing process Measured interferometrically with a combination of a spherical caliber and a nulling lens (NL) reducing the length of the bench from 10m (Rc of the filter face) to 2m Flat reference measured at 5 positions of the NL around the zero focus position linear fit gives bench calibration (nm RMS/mm NL) and position of the NL for focus=0 (bench WFE) Spherical caliber at Rc~10m and grism filter face measured with the same method at different NL positions NL positions gives the focus of the filter face and the flat reference removal gives the RMSi Grism Curved Face Intelliwave software Nulling lens F=882mm Caliber F=600mm Fizeau phase-shifting interferometer (λ=633nm) Micromesure rail and digital display Measured after each manufacturing step: prism, filter deposition and gluing

15 15 Filter face focus of the EQM Evolution of the focus of the EQM filter face measured: 6,5 fringes on the filter face and 5 fringes on the grating face Differential defocus of 1,5 fringes but symetrical deformation is expected Hypothesis and investigations on-going: The lens supplied is different from the one specified with strong aberrations Reference plane measurement high spherical aberration impacts the focus measurement and is not explained by design Evolution of the bench calibration between the beginning and the end of the EQM manufacturing The multilayer filter disturbs the interferometric measurement The focus measurements of the filter face are under study

16 Filter SFE of the EQM without focus Evolution of the SFE without focus of the filter face is the same as the grating face Filter SFE evolution is similar to the grating face, except for focus: Coma added by filter Astigmatism and trefoil added by gluing Bending (symetrical deformation) hypothesis confirmed

17 17 Conclusion and perspectives Euclid/NISP Grisms are complex optical components with 4 optical functions and stringent optical performances specifications for efficiency and WFE EQM manufacturing is finished - optical verification tests, cryo qualification and metrology done. Last steps: vibration qualification tests (60g DLL) sinus and random are on-going now Optical tests in cryo: defocus measurement Delivered fully qualified to the projet for integration onto the EQM wheel in November 2016 The 4 Flight Models manufacturing is already on-going. Delivery in June 2017.