Udo Schhle

1
EUS NI spectrograph design constraints

• Contents
• design of normal-incidence spectrograph with
  ZEMAX
• optical quality of the single-mirror off-axis
  telescope
• possibility of three wavelength ranges between 58
  nm and 126.8 nm
• design of focal plane with 116.8 nm to 126.8 nm
  channel
• some thoughts on thermal aspects
• Semi-transparent telescope mirror
• Heat rejection mirror

Udo Schühle Max-Planck-Institute for Solar
System Research Solar Orbiter 5th EUS consortium
Meeting at RAL on 3. March 2006
2
normal-incidence design optical calculations

• Based on previous design of Roger Thomas
• development of varied-line-space grating surface
  for ZEMAX
• ZEMAX calculation with ellipsoid VLS grating
• modified RT design for longer wavelength channel
• verified the design complies with specs
• some possible thermal design solutions

3
off axis parabola telescope aperture size 70
mm distance from vertex 50 mm focal length
700 mm image scale 1arcsec 3.4
microns spectrograph grating varied-line-space
on ellipsoid magnification 3.6 image
scale 12 mm/arcsec dispersion 5 A/mm
spectral scale 60 mA/12mm (40 mA/8mm)
Design of NI spectrograph
1 arcsec
4
Design of single-mirror telescope
off axis parabola telescope aperture size 70
mm distance from vertex 50 mm focal length
700 mm image scale 1arcsec 3.4 microns
1 arcsec
1 arcsec
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Accommodation of three wavelength bands possible?

• favoured wavelength ranges 52 nm 63 nm
• 72 nm 80 nm
• 97 nm 104 nm
• 116.5 nm 126.8 nm
• possible with siliconcarbide optics
• normal incidence design with three wavelength
  ranges from 58.0nm to 126.8nm

6
Accommodation of three wavelength bands possible!
900 mm
70 mm
slit

• 71.0 nm
• 80.0 nm

250 mm

• 97.0 nm
• 104.5 nm

TVLS grating

• 116.5 nm (58 nm)
• 126.8 nm (63 nm)

700 mm
7
Accommodation of long-wavelength band
Si III
C III
N V
C I Si I
O V
Mg X
Mg X
He I
O IV
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Accommodation of long-wavelength band
More useful dynamic range with selective
photocathode distribution
Presentation of wavelength channels to be given
by Luca Teriaca
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Study of a dichroic telescope mirror for 58 nm up

• mirror coating for wavelengths 58 nm and up
  SiC (CVD, hex)
• a thin coating of 10 nm provides good VUV
  reflectivity of 35 to 45
• longer wavelengths can be transmitted by a
  transparent substrate
• mirror temperature can be minimised
• detailed thermal study is possible.
• ? dichroic telescope mirror can transmit 90 of
  the heat!

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Study of a dichroic telescope mirror for 58 nm up
Calculations of David Windt 2001 using optical
constants of SiC
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Study of a dichroic telescope mirror for 58 nm up
10 nm SiC on LiF substrate
independent study is ongoing with samples of
SiO2 and SiC coating of 5 nm, 10 nm, 20 nm
thickness
calculation using optical constants of Palik et
al.
gt heat will be transmitted towards a radiator
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Design of single-mirror telescopeheat
rejection mirror and baffle

• field of incident radiation at slit plane
  -2.6
• ( size of solar image pointing range)
• corresponds to circular range of 64 mm
  diameter!
• unpredictable thermal distortions during orbit
  and pointing changes
• unpredictable stray light in front of the
  spectrometer slit

? toroidal pre-slit mirror
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Design of single-mirror telescopeheat
rejection mirror and baffle
radiator
radiator
toroidal heat rejection mirror
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Thermal baffle design requires space for heat
rejection mirror
900 mm
70 mm
slit

• 75.0 nm
• 85.0 nm

250 mm

• 97.0 nm
• 104.0 nm

TVLS grating

• 116.5 nm (58 nm)
• 126.8 nm (63 nm)

heat rejection mirror
700 mm