Download ppt - EUS NI spectrograph design constraints

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 ZEMAX2. optical quality of the single-mirror off-axis telescope3. possibility of three wavelength ranges between 58 nm and 126.8 nm4. design of focal plane with 116.8 nm to 126.8 nm channel5. some thoughts on thermal aspects:

a) Semi-transparent telescope mirrorb) 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 mmdistance from vertex: 50 mmfocal length: 700 mmimage scale: 1arcsec = 3.4 micronsspectrograph:grating: varied-line-space on ellipsoidmagnification: 3.6image scale: 12 m/arcsecdispersion: 5 A/mm spectral scale: 60 mA/12m

(40 mA/8m)

1 arcsec

Design of NI spectrographDesign of NI spectrograph


Design of single-mirror telescopeDesign of single-mirror telescope

1 arcsec

1 ar

csec

off axis parabola telescope:aperture size: 70 mmdistance from vertex: 50 mmfocal length: 700 mmimage scale: 1arcsec = 3.4 microns


• 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 m

m

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!

250

mmslit


Accommodation of long-wavelength Accommodation of long-wavelength bandband

He I O VMg XO 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 distributionPresentation 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

%R r

%A r

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 SiO2and 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

radiator radiator

toroidal heat rejection mirror


900 mm

70 m

m

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

250

mmslit

heat rejection mirror - 116.5 nm (58

nm)- 126.8 nm (63

nm)