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Normal-Incidence Design Option for SolO/EUS

Normal-Incidence Design Option for SolO/EUS. Roger J. Thomas NASA/GSFC 2004 November 04. NEXUS : SmEx Proposal. Required EUV spectrograph capabilities Rapid cadence (10s) Large FOV Wide temperature coverage: 20,000 K to 4 MK Doppler measurements of 1-5 km/s 1.2 arcsec spatial resolution.

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Normal-Incidence Design Option for SolO/EUS

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  1. Normal-Incidence Design Option for SolO/EUS Roger J. Thomas NASA/GSFC 2004 November 04

  2. NEXUS : SmEx Proposal • Required EUV spectrograph capabilities • Rapid cadence (10s) • Large FOV • Wide temperature coverage: 20,000 K to 4 MK • Doppler measurements of 1-5 km/s • 1.2 arcsec spatial resolution

  3. NEXUS : SmEx Phase-A Design • Basic components of NEXUS • 2 element normal-incidence optical design • Off-axis parabolic mirror telescope f/9.3 • Toroidal varied-line-space (TVLS) grating spectrograph with a magnification of 5.6 • B4C / Iridium optical coatings • Slit (0.5 arcsec) / Slot (1 arcmin) • Two ICCD detectors • Wavelength ranges (1st order): 443-519 & 561-632 Å • Total optical length: 1400 mm

  4. Future Design Plans (in response to earlier discussions) • Add a 3rd wavelength bandpass • Allow telescope to be slightly Hyperbolic • Increase FOV and spectral coverage • Relax spatial & spectral resolutions • Increase entrance-slit width • Reduce physical instrument dimensions

  5. Design Considerations • Magnifying spectrograph • RI / RO 4 • Large plate scale in small physical length • Most efficient use of available volume • Aberrations corrected by VLS rulings on Ellipsoid • Thermal advantages • All optics see un-concentrated solar radiation • Primary at back: allows shielding and direct radiative cooling • Unwanted light can be reflected out the front

  6. EUNIS/NEXUS TVLS Grating -- Zeiss Measured Groove-Density Variations

  7. EUNIS/NEXUS TVLS Grating -- Zeiss Measured Groove-Profiles

  8. NASA-Goddard Space Flight Center Dr. Roger Thomas TVLS Grating #G5 for EUNIS #3 Carl Zeiss Laser Optics GmbH Grating Technology Dr. Ralf Lenke Dr. Klaus Heidemann Date August 25, 2004 Ref. No. TG04-108 Page 2/4 Groove profile Position [mm] Blaze angle Anti-blaze angle y z [deg] [deg] mean 3.4 16.2 +0.3/-0.4 +1.4/-1.3 The 1st order groove efficiency is calculated in a first approache from the averaged groove profile.  [nm] EFFgr [%] 50.0 64.8 52.5 65.6 55.0 65.8 57.5 65.3 60.0 64.3 62.5 62.9 65.0 61.3

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