Udo Schühle 5. Solar Orbiter EUS Consortium Meeting RAL, 3. March 2006 EUS NI spectrograph design...

Udo Schühle5. Solar Orbiter EUS Consortium MeetingRAL, 3. March 2006

EUS NI spectrograph EUS NI spectrograph design constraintsdesign constraints

Udo SchühleUdo Schühle

Max-Planck-Institute for Solar System ResearchMax-Planck-Institute for Solar System Research

Solar Orbiter 5th EUS consortium MeetingSolar Orbiter 5th EUS consortium Meeting

at RAL on 3. March 2006 at RAL on 3. March 2006

Contents:

1. design of normal-incidence spectrograph with ZEMAX

2. optical quality of the single-mirror off-axis telescope

3. possibility of three wavelength ranges between 58 nm and 126.8 nm

4. design of focal plane with 116.8 nm to 126.8 nm channel

5. some thoughts on thermal aspects:

a) Semi-transparent telescope mirror

b) Heat rejection mirror


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

normal-incidence design optical normal-incidence design optical calculationscalculations


off axis parabola telescope:

aperture size: 70 mm

distance from vertex: 45 mm

focal length: 600 mm

image scale: 1arcsec = 3.0 microns

spectrograph:

magnification: 3.9

image scale: 12 m/arcsec

dispersion: 5 A/mm

spectral scale: 60 mA/12m

(40 mA/8m)

Wavelengths: 54 -64 nm

70 – 80 nm

97 -106.2 nm

R. Thomas design of NI spectrographR. Thomas design of NI spectrograph







spectrograph:

magnification: 3.6

image scale: 12 m/arcsec

dispersion: 5 A/mm

spectral scale: 60 mA/12m

(40 mA/8m)

Wavelengths: 70 – 80 nm

97 -104 nm

116.7 -126.8 nm (57 – 63 nm)

1 arcsec

Design of NI spectrographDesign of NI spectrograph


Design of single-mirror telescopeDesign of single-mirror telescope

1 arcsec

1 a

rcse

c







• favoured wavelength ranges : 52 nm – 63 nm72 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

Accommodation of three wavelength Accommodation of three wavelength bands possible?bands possible?


900 mm

70

mm

TVLS grating

- 71.0 nm

- 80.0 nm

- 116.5 nm (58

nm)

- 126.8 nm (63

nm)

- 97.0 nm

- 104.5 nm

700 mm

Accommodation of three wavelength Accommodation of three wavelength bands possible!bands possible!

25

0 m

mslit


Accommodation of long-wavelength Accommodation of long-wavelength bandband

He IO VMg X

O IV

C III

Si III

N V C I Si I

Mg X


Accommodation of long-wavelength Accommodation of long-wavelength bandband

More useful dynamic range with selective photocathode distribution

Presentation of wavelength channels to be given by Luca Teriaca


Study of a dichroic telescope Study of a dichroic telescope mirror for 58 nm upmirror 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!



Calculations of David Windt 2001 using optical constants of SiC


0

5

10

15

20

25

30

35

40

45

50

55

60

0

10

20

30

40

50

60

70

80

90

100

50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

%Rr

%Ar

Wavelength (nm)

Reflection (

%)

Absorbtance (%)


==> heat will be transmitted towards a radiator

10 nm SiC on LiF substrate*

* calculation using optical constants of Palik et al.

independent study is ongoingwith samples of SiO2

and SiC coating of 5 nm, 10 nm, 20 nm thickness


Design of single-mirror Design of single-mirror telescope:telescope:

heat rejection mirror and baffleheat 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 mirrortoroidal pre-slit mirror


Design of single-mirror Design of single-mirror telescope:telescope:

heat rejection mirror and baffleheat rejection mirror and baffle

radiatorradiator

toroidal heat rejection mirror


900 mm

70

mm

TVLS grating

- 75.0 nm

- 85.0 nm

- 97.0 nm

- 104.0 nm

700 mm

Thermal baffle design requires space for Thermal baffle design requires space for heat rejection mirrorheat rejection mirror

25

0 m

mslit

heat rejection mirror - 116.5 nm (58

nm)

- 126.8 nm (63

nm)

Udo Schühle 5. Solar Orbiter EUS Consortium Meeting RAL, 3. March 2006 EUS NI spectrograph design...

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