Post on 20-Dec-2015
transcript
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IRMS Preliminary results - overview
Optimize Field lenses in collimator and camera to for 1.39m field curvature on NFIRAOS
Get good imaging performance
Get marginal spectroscopy performance.
Recommend collimator re-design to gain full performance.
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Pupil
Simple modification of field lens in collimator to match pupil to cold stop
Looks ok, some colour but with just changing field stop this is what you get.
IRMS MOSFIRE
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Imaging
Modify field flattener in camera and field lens in collimator
Slightly worse, but within the original MOSFIE req. of over 0.97-2.45 microns with no re-focus.
IRMS MOSFIRE
IRMS- Imaging Mode
Field RMS spot diameter
Radius arc-sec pixels
0 0.079 1.27
0.71' 0.095 1.52
1' 0.114 1.82
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Spectroscopy
In addition to collimator field lens and camera field flattener modification, allow for small refocus between spectral bands to improve image quality but image quality still worse than MOSFIRE.
about 82% enslit energy for design residual, so loss of spectral resolution occurs.
IRMS MOSFIRE
*Slit defocus not considered in calculation, calculation for an ideal ‘spherical’ slit mask
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Spectroscopy
MOSFIRE criteria was ensquared energy 80% within 2 pixels (pixels 18 microns ), and MOSFIRE achieve roughly 90% on average for design residual, leaving margin for manufacturing tolerances.Need collimator redesign for new field curvature to regain full performance. Likely able to do this with lenses constrained to original lens groups ( a quick optimization was done which suggested this should be possible)
*Slit defocus not considered in calculation, calculation for an ideal ‘spherical’ slit mask
IRMS - Spectroscopic Mode
Enslit Energy in 2x2 pixels
Y-band
J-band
H-band K-band
avg 84% 83% 81% 82%
max 100% 95% 97% 100%
min 71% 70% 50% 40%
Half-Width (in microns) for 80% enslit energy
Y-band
J-band
H-band K-band
avg 16 17 18 17
max 24 24 33 28
min 9 11 12 12
Width ( in pixels ) for 80% enslit energy
Y-band
J-band
H-band K-band
avg 1.8 1.8 2.0 1.9
max 2.6 2.6 3.6 3.1
min 1.0 1.2 1.3 1.3
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CSU – Configurable Slit Unit
Sag along slit height at slit mask in Keck is 4.17mm, and a 3 tiered arrangement of knife edges was used, for TMT, sag is ~50% more ( 6.4mm) so 5 tiered would probably be used
Sag along dispersion with keck was ~1mm, (@1.5’ )no correction for curvature on Keck, for TMT, will have ~1.6mm (@0.5’), so will have slit ‘blur’ for IRMS ( geometric blur of 24mas or 127nm RMS WFE for +/-0.8mm defocus). Slit losses at field edges will be marginal .