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Spectrometer simulation

Why we need it now What should be simulated How to do it Work plan Conclusion. Spectrometer simulation. A.Bonissent A.Ealet C.Macaire E.Prieto A.Tilquin. Note in http://www.astrsp-mrs/snap/spectro/spectrosim.ps.

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Spectrometer simulation

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  1. Why we need it now What should be simulated How to do it Work plan Conclusion Spectrometer simulation A.Bonissent A.Ealet C.Macaire E.Prieto A.Tilquin Note in http://www.astrsp-mrs/snap/spectro/spectrosim.ps

  2. Previous stage, only laboratory tests and simulation of slicer alone have been performed. This is sufficient to ensure that an instrument can be built with adequate performance. Now to study the real performances on the full instrument, we need a complete simulation Past

  3. Needed in the present phase for Optimizing the design: balance cost and simplicity (reliability) for best possible physics compute realistic efficiency evaluate tolerance evaluate calibration procedure produce realistic data to develop and test data processing algorithms At term, it will be used in detailed MC studies for physic analysis Why

  4. Optical simulation Library of psf Optomechanical simulation Optimisation process Specifications Optical design No OK ? yes

  5. At the end of phase A, we need a Finaldesign of the instrument with estimated (and justified) performances Simulation and data reduction software for evaluation should be ready well before simulation spring 2003 data reduction prototype spring 2004 Développement plan

  6. Full SNAP simulation Cosmo models instrument analysis Lightcurve spectra Physic parameters Detector pixel data propagation physic Data cube Data reduction Lightcurve spectra SN simulation

  7. Spectrometer simulation x,y,l opticalsim i,j,Qij telescope readout Parameterization constants x,y,l psf1 Pixel parameterization fit slicer Data cube i,j,adc x,y,l psf2 i,j,Qij x,y,l psf3 pixellisation spectrograph

  8. Method Compute Psf and transmission at each x,y,l Telescope xt,yt, TF Slicer xs,ys pupil xp,yp Slit xf,yf prism xl,yl TF Detector xd,yd TF TF TF peif p peif p peif psf TF of amplitude from object plane to pupil plane then to image Apply geometry and phase (zernike) on pupil Apply geometry on image Compute intensity to evaluate efficiency Interpolate position x,y at each step (need parametrisation) Output is position on the detector for each point and wavelength with an associated PSF Very long and CPU intensive

  9. Psf shape and size depends on x,y,l (small amount of) energy is lost by diffraction Geometry affects performance psf slice

  10. 0.9 mm Slice 0 Slice 2 1.7 mm

  11. Zernike polynomial of slicer for l = 1.7 mm Zernike Polynomia from Zeemax are used to introduce aberrations Depend of l,x,y They need to be extrapolate on each point of the image plan Use Neural Network technique to do extrapolation

  12. psf slice Efficiency study Gobal efficiency Telescope+slicer+spectrograph

  13. Simulation checking: spectral resolution R= l/dlpixel

  14. DESIGN OPTIMISATION Test optic Play with optic to study tolerance Efficiency/nb of pixel Visible/IR efficiency vs spectral resolution/detector optimise spatial resolution => detector noise optimisation Reduce Nb of mirrors : better transmission but may need more space, more complex optics TEST DATA Slit effect : Position of SN in slice => translation of spectrum; SN may cover several slices : need to add translated spectra Optical distorsions Pixellization Dithering Detector and electronics : efficiency, noise, cosmics ... Used for :

  15. Distorsions on the detector 20 pixel/slice U spatial dimension Detector pixels do not coincide with l = Cte or x = Cte V spectral dimension

  16. Full simulation of slicer unit OK Full simulation of telescope and spectrometer OK Interpolate for intermediate points using Neural Network technique. OK library of PSF for a grid of x,y,l; under work From library of PSF+ geometry (x,y,l -> detector indices) to be done Pixellisation : integrate over pixels Add dark current, readout noise etc... Include galaxy Dithering (spatial, spectral) If useful, we may use general purpose code developed by CRAL (SNIFS, SN factory). Current Status

  17. Detailed simulation of the spectrometer is needed in this phase to quantify performances CPU intensive : not appropriate for physics simulation Parametric simulation under development, based on the library of PSF should be appropriate for a full SNAP simulation (not for SNAPfast). Conclusion

  18. Spectrograph: Performances Gain on mirror transmission, loose on diffraction/prism (complete simulation) Globally equivalent

  19. Design issues • Spectral resolution : optimization visible /IR • ( R(IR [1-1.4] mm) < 100 but don’t need to join the 2 detectors ) • Polarization:specification needed – impact on spectrograph • Design • Spatial resolution : 0.15”. Issue vs the radiation rate • Wavelength range 1.7 mm short for the Si line , 1.8 mm better • but detector l cut issue , issue on temperature

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