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990901EIS_Opt.1 The Instrument: Optical Design Dr. John T. Mariska Data Coordination Scientist Naval Research Laboratory 202-767-2605

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Presentation on theme: "990901EIS_Opt.1 The Instrument: Optical Design Dr. John T. Mariska Data Coordination Scientist Naval Research Laboratory 202-767-2605"— Presentation transcript:

1 990901EIS_Opt.1 The Instrument: Optical Design Dr. John T. Mariska Data Coordination Scientist Naval Research Laboratory Dr. Charles M. Brown US Instrument Scientist Naval Research Laboratory

2 990901EIS_RR_Opt.2 EIS Instrument Schematic Sun Filter Grating Primary CCD Long CCD Short Slit

3 990901EIS_RR_Opt.3 EIS Design Optimization Criteria Overall Length < 3 Meters Overall Width < 0.5m Telescope Mirror Diameter 150mm Plate Scale 1 arc-sec/Pixel Spatial –13.5 Micron Pixels Two Wavelength Bands of 40 Å Width –Short Wavelength Centered at 190Å –Long Wavelength Centered at 270Å Two Detectors Cover 40Å Each 4200 l/mm Grating-Single Ruling Density –Half ML Coated for 190Å –Half ML Coated for 270Å Detector Must Clear Input Path (etc.)

4 990901EIS_RR_Opt.4 EIS-7Tr Design Heritage Trendy: Paraboloid Telescope –Only Two Reflections SERTS: Toroidal Grating J-PEX: Laminar Rulings EIT and Trace: Sectored Multilayer Coatings Sumer: Primary Mirror Scan Concept

5 990901EIS_RR_Opt.5 Transmission of Al Filter

6 990901EIS_RR_Opt.6 F/13 Off-Axis Parabola

7 990901EIS_RR_Opt.7 Spot Diagrams for 0, ± 4 arc min

8 990901EIS_RR_Opt.8 Summary: RMS Blur of Primary

9 990901EIS_RR_Opt.9 Grating Slit 190A 270A EIS-7TR Spectrometer Layout

10 990901EIS_RR_Opt.10 Comparison of Designs - Summary

11 990901EIS_RR_Opt.11 EIS-7T Layout

12 990901EIS_RR_Opt.12 EIS-7TR Spectrometer Layout 270 Å Band

13 990901EIS_RR_Opt.13 EIS-7Tr Super-Optimized by Roger Thomas

14 990901EIS_RR_Opt.14 EIS-7Tr Spot Diagrams and Histograms

15 990901EIS_RR_Opt.15 EIS-7Tr Field of View 190 Å

16 990901EIS_RR_Opt.16 EIS-7Tr Spot Diagrams Å

17 990901EIS_RR_Opt.17 EIS-7Tr Spectral and Spatial Resolution Curved Focal Surface - Short Band

18 990901EIS_RR_Opt.18 EIS-7Tr Spectral and Spatial Resolution Flat Focal Surface - Short Band

19 990901EIS_RR_Opt.19 EIS-7Tr Spot Diagrams Å

20 990901EIS_RR_Opt.20 EIS-7Tr Field of View 270 Å

21 990901EIS_RR_Opt.21 EIS-7Tr Spectral and Spatial Resolution Flat Focal Surface - Long Band

22 990901EIS_RR_Opt.22 Detector Locations - Summary

23 990901EIS_RR_Opt.23 Multilayer Gratings Characterized by NRL

24 990901EIS_RR_Opt.24 1 Seely, Applied Optics 36, 8206 (1997) 2 J-PEX mission, Ray Cruddace and Mike Kowalski NRL Experience With Zeiss Holographic Ion-Etched Laminar Gratings

25 990901EIS_RR_Opt.25 AFM Image of a Zeiss Holographic Grating

26 990901EIS_RR_Opt.26 Laminar Grating Efficiency Calculation Computer Code Accounts for the Multilayer Coating: – Thickness and Optical Properties of the Layer Materials – Interdiffusion Layer Thickness and Microroughness Laminar Groove Pattern: 4200 G/mm, Equal Land and Groove Widths, Uniform Groove Depth EIS7 Optical Model:  = 6.388° and  = 8.526° Optimal Groove Depth Is H = (p /2)/(cos  + cos  ) Where P = 1, 3,... – H = /4 for Normal Incidence – H Varies Slowly With  and  58 Å Groove Depth Is Optimum for  = 6.388° and = 232 Å. EIS7 LONG Waveband: – 20 Mo/mosi2/si Periods – 2d = 290 Å, Rpk = 24% at = 268 Å EIS7 SHORT Waveband: – 20 Mo/mosi2/si Periods – 2d = 210 Å, Rpk = 31% at = 195 Å

27 990901EIS_RR_Opt.27 Groove Efficiency Groove Efficiency  Multilayer Grating Efficiency / Multilayer Coating Reflectance Laminar Grating With 4200 Grooves/mm and: –Equal Land and Groove Widths  Zero Even-Order Groove Efficiency –Groove Depth h = 58 Å  Zero 0th-Order Groove Efficiency at  4h = 232 Å. Odd-Order Groove Efficiencies Varies Slowly With Wavelength and Angle:

28 990901EIS_RR_Opt.28 Efficiency in the Two Wavebands in Diffraction Orders Multilayer Grating Efficiency

29 990901EIS_RR_Opt.29 Draft Specifications for Primary

30 990901EIS_RR_Opt.30 Flight Grating Optical Specifications

31 990901EIS_RR_Opt.31 Scientific Performance Achieving the EIS Scientific Goals Requires an Instrument That Can Obtain Sufficient Numbers of Detected Photons in a Single 3–20 s Exposure to Characterize Emission Line Profiles of Interest To Verify This, We Have Modeled the Instrument Throughput Simulated the Ability of the Instrument to Measure Doppler Shifts and Nonthermal Velocities As a Function of Count Rate

32 990901EIS_RR_Opt.32 EIS Is a Stigmatic Spectrometer

33 990901EIS_RR_Opt.33 EIS Slit and Raster

34 990901EIS_RR_Opt.34 Instrument Throughput Throughput for the Entire Optical Chain Has Been Modeled Using Mirror Area = 88.4 cm 2 (Half of a 15 cm Diameter Mirror) Grating Groove Efficiency = 0.40 Detector Quantum Efficiency = 0.80 Obscuration by Front Filter Support Structure = 0.80 Obscuration by Mesh Supporting Front Filter = 0.80 Wavelength-Dependent Transmission Curves for Two Thin Al Filters Wavelength-Dependent Multilayer Efficiencies for Mirror and Grating Computed by J. Seely Slit Width = 1 Arcsec Solar Spectra Computed Using Chianti Atomic Physics Database and Emission Measure Curves for Quiet Sun, Active Regions, and Flares

35 990901EIS_RR_Opt.35 Active Region Performance

36 990901EIS_RR_Opt.36 EIS Quiet Sun Performance

37 990901EIS_RR_Opt.37 EIS Flare Performance

38 990901EIS_RR_Opt.38 Velocity Resolution Estimates of Errors in Velocity Measurements Assume Dispersion –Long Wavelength: 25.7 km s -1 Per Pixel (0.023 Å) –Short Wavelength: 36.5 km s -1 Per Pixel (0.023 Å) Spectral Resolution –Long Wavelength: 11.0 mÅ rms (21.5 fwhm) –Short Wavelength: 10.7 mÅ rms (24.1 fwhm) CCD Pixel Size: 13.5 Microns Nonthermal Velocity: 20.0 km s -1 Formation Temperature of Emission Line: 1.5 MK Atomic Mass 56 Rest Wavelength –Long Wavelength: Å –Short Wavelength: Å

39 990901EIS_RR_Opt.39 Long Wavelength Velocity Error Estimates

40 990901EIS_RR_Opt.40 Short Wavelength Velocity Error Estimates

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