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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. - PowerPoint PPT Presentation
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A. Ealet Berkeley, december 2002 1
Spectrometer simulation
Note in http://www.astrsp-mrs/snap/spectro/spectrosim.ps
● Why we need it now● What should be simulated● How to do it● Work plan● Conclusion
A.BonissentA.EaletC.MacaireE.PrietoA.Tilquin
A. Ealet Berkeley, december 2002 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
A. Ealet Berkeley, december 2002 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
A. Ealet Berkeley, december 2002 4
Specifications
OK ?
Optical design
Optical simulation
No
Optomechanical simulation
Library of psf
yes
Optimisation process
A. Ealet Berkeley, december 2002 5
● At the end of phase A, we need a Final design of the instrument with estimated (and justified) performances
● Simulation and data reduction software for evaluation should be ready well before
simulation spring 2003data reduction prototype spring 2004
Développement plan
A. Ealet Berkeley, december 2002 6
● Full SNAP simulation
SN simulation
analysis
propagation
Data reduction
instrument
Detector pixel data
physic
Data cube
Lightcurvespectra
Lightcurvespectra
Cosmo models
Physic parameters
A. Ealet Berkeley, december 2002 7
● Spectrometer simulation
telescope
optical sim
readout
pixellisation
slicer
spectrograph
fit Data cubei,j,adc
Parameterization constants
x,y,
x,ypsf1
x,y,psf2
x,y,psf3
i,j,Qij
i,j,Qij
Pixel parameterization
A. Ealet Berkeley, december 2002 8
TF of amplitude from object plane to pupil plane then to imageApply geometry and phase (zernike) on pupilApply geometry on imageCompute intensity to evaluate efficiencyInterpolate 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
Method
Telescopext,yt,
Slicerxs,ys
Slitxf,yf
prismxl,yl
Detectorxd,yd
pei
Compute Psf and transmission at each x,y,
pupilxp,yp
TF
p peipei ppsf
TFTF TF TF
A. Ealet Berkeley, december 2002 9
Psf shape and size depends on x,y,(small amount of) energy is lost by diffractionGeometry affects performance
psf
slice
A. Ealet Berkeley, december 2002 10
0.9 m
1.7 m
Slice 0
Slice 2
A. Ealet Berkeley, december 2002 11
Zernike Polynomia
from Zeemax are used to introduce aberrations
Depend of,x,y
They need to be extrapolate on each point of the image plan
Use Neural Network technique to do extrapolation
Zernike polynomial of slicer for = 1.7 m
A. Ealet Berkeley, december 2002 12
psf
slice
Efficiency study
Gobal efficiencyTelescope+slicer+spectrograph
A. Ealet Berkeley, december 2002 13
R=/pixel
Simulation checking: spectral resolution
A. Ealet Berkeley, december 2002 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 :
A. Ealet Berkeley, december 2002 15
Distorsions on the detector
U s
patia
l dim
ensi
on
V spectral dimension
Detector pixelsdo not coincide with = Cte or x = Cte
20 pixel/slice
A. Ealet Berkeley, december 2002 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,; under work
From library of PSF+ geometry (x,y,-> 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
A. Ealet Berkeley, december 2002 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
A. Ealet Berkeley, december 2002 18
Spectrograph: Performances
telescope
Relay optics
Slicer
Optic straylight diffra.
Spectro
Mirrors prism dichroic
Detector
Vis / NIR
#elements
4 1 3 1 1 2 1 1 1 1
Efficiency/ 0.98 0.98 0.98 0.99 0.95 0.98 0.81 0.95 0.9
0.6
(0.8)
cumulative 0.92 0.90 0.85 0.84 0.80 0.77 0.62 0.59 0.53
0.35
(0.47)
Gain on mirror transmission, loose on diffraction/prism (complete simulation)Globally equivalent
A. Ealet Berkeley, december 2002 19
Design issues
•Spectral resolution : optimization visible /IR( R(IR [1-1.4] m) < 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 m short for the Si line , 1.8 mm betterbut detector cut issue , issue on temperature