990901EIS_Opt.1

The Instrument: Optical Design

Dr. John T. Mariska

Data Coordination Scientist

Naval Research Laboratory

202-767-2605

e-mail: mariska@aspen.nrl.navy.mil

Dr. Charles M. Brown

US Instrument Scientist

Naval Research Laboratory

202-767-3578

e-mail: cbrown@ssd5.nrl.navy.mil

990901EIS_RR_Opt.2

EIS Instrument Schematic

SunFilter

GratingPrimary

CCD Long

CCD Short

Slit

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.)

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

990901EIS_RR_Opt.5

Transmission of Al Filter

990901EIS_RR_Opt.6

F/13 Off-Axis Parabola

990901EIS_RR_Opt.7

Spot Diagrams for 0, ± 4 arc min

990901EIS_RR_Opt.8

Summary: RMS Blur of Primary

990901EIS_RR_Opt.9

Grating

Slit

190A

270A

EIS-7TR Spectrometer Layout

990901EIS_RR_Opt.10

Comparison of Designs - Summary

990901EIS_RR_Opt.11

EIS-7T Layout

990901EIS_RR_Opt.12

EIS-7TR Spectrometer Layout270 Å Band

990901EIS_RR_Opt.13

EIS-7TrSuper-Optimized by Roger Thomas

990901EIS_RR_Opt.14

EIS-7Tr Spot Diagrams and Histograms

990901EIS_RR_Opt.15

EIS-7Tr Field of View 190 Å

990901EIS_RR_Opt.16

EIS-7Tr Spot Diagrams 170 - 210 Å

990901EIS_RR_Opt.17

EIS-7Tr Spectral and Spatial Resolution Curved Focal Surface - Short Band

990901EIS_RR_Opt.18

EIS-7Tr Spectral and Spatial Resolution Flat Focal Surface - Short Band

990901EIS_RR_Opt.19

EIS-7Tr Spot Diagrams 250 - 290 Å

990901EIS_RR_Opt.20

EIS-7Tr Field of View 270 Å

990901EIS_RR_Opt.21

EIS-7Tr Spectral and Spatial Resolution Flat Focal Surface - Long Band

990901EIS_RR_Opt.22

Detector Locations - Summary

990901EIS_RR_Opt.23

Groove Freq. Fabrication* Multilayer Peak Wavelength ReferenceGroove Area Microroughness Period Angle of Incidence Vol., PageOptical Figure Manufacturer Bilayers Overall Eff., Groove Eff. Year 1st Order 2nd Order 4800 g/mm RRB, 3.8o Mo/Si 225 Å 125 Å Appl. Opt.40x40 mm2 12-20 Å 128.4 Å 10o 6o April 1Flat Hitachi 18 2.6%, 19% 0.3%, 4% 1999 3600 g/mm HIEB, 3o Mo/Si 128 Å Appl. Opt.19 mm 8 Å 67.5 Å 10o 34, 7338Flat Tayside 35 13%, 23% 1995 3600 g/mm RRB, 3.1o Mo/Si 300 Å 135 Å Appl. Opt.25x75 mm2 10 Å 71.0 Å 10o 10o 34, 6453ROC 4 m B&L 23 - , 40% 1.5%, 4.7% 1995 SKYLAB 3600 g/mm HIEL, 62 Å MoC/Si 235 A Appl. Opt.80x160 mm 3 Å 128 Å 5o

ROC 4 m Zeiss 10 10.5%, 35% J-PEX 2400 g/mm HIEL, 40 Å Mo/Si 150 Å Appl. Opt.

5-8 Å 79 Å 10o 36, 8206Flat Zeiss 30 16%, 33% 1997 2400 g/mm HIEB, 2o Mo/Si 147 Å Appl. Opt.25x75 mm2 5 Å 154 Å 10o 34, 7347ROC 2.2 m Tayside 25 7.5%, 27% 1995 2400 g/mm HIEB, 2.7o Mo/Si 195 Å J. El. Spectr.10x10 mm2 8-15 Å 10o 80, 473ROC 2.2 m Shimadzu 0.2%, 1% 1996 2400 g/mm RRB, 2o Mo/Si 139 Å Appl. Opt.

73.2 Å 10o 32, 4890ROC 2.2 m Hyperfine 40 2.2%, 4.4% 1993 2400 g/mm RRB, 2o Mo/Si 290 Å 151 Å Appl. Opt.

162.5 Å 14o 14o 32, 2422ROC 2.2 m Hyperfine 30 2.5%, 10% 1.5%, 4.5% 1993 *RRB=Ruled Replica Blazed, Blaze Angle HIEB=Holographic Ion-beam Etched Blazed, Blaze Angle HIEL=Holographic Ion-beam Etched Laminar, Groove Depth

Multilayer Gratings Characterized by NRL

990901EIS_RR_Opt.24

Parameter Test Grating1 Rocket Spectrometer2

Grating Area, ROC 25 mm diam, flat 160 x 80 mm2, 4.0 m

Grooves/mm 2400 g/mm 3600 g/mm

Cost, Number of Gratings $22K, 1 $130K, 4+1 setup

Procurement/Delivery Time 12 mon. (ML) 16 mon. (uncoated)

Groove Depth, Optimal Wavelength 40 Å, 160 Å 63 Å, 252 Å

Microroughness (2-40 μm-1) 5 Å 3 Å

Peak Eff., Groove Eff. 16% , 34% 10.5% , 35% (best), Order, Angle 150 Å, +1, 10o 235 Å, +1, 5o

1Seely, Applied Optics 36, 8206 (1997) 2J-PEX mission, Ray Cruddace and Mike Kowalski

NRL Experience With Zeiss Holographic Ion-Etched Laminar Gratings

990901EIS_RR_Opt.25

4167 A

40 A

AFM Image of a Zeiss Holographic Grating

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

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:

990901EIS_RR_Opt.28

Efficiency in the Two Wavebands in Diffraction Orders 1 - 3

Multilayer Grating Efficiency

990901EIS_RR_Opt.29

1. Figure: Off-axis Parabola2. Figure accuracy ~/15 (deviation from perfect parabola in 6328 wl)3. Focal length : 1934 mm +0-1%4. Diameter : 16cm (clear aperture 15cm)5. Off-axis distance 65mm from inside edge (70 mm from clear aperture)6. Blank thickness 1/6 – 1/10 diameter (<2") TBD7. Surface microroughness <5Å rms, 3Å goal8. Material Premium grade Zerodur or ULE TBD9. Surface Quality 20/10 goal, 40/20 required10.Optical Coating; none (ML coating to be applied elsewhere)11.A TBD area on back surface to be polished flat with a measured angle

relative to optical axis to 1'(TBD).12.A scribe line on the back surface must indicate the optical plane with 6'

accuracy.13.A "+" mark shall be scribed on the back surface on the edge nearest the

optical axis. The "+" mark is to be located 70 mm from the optical axis.14.Light-weighting TBD (up to 60% is possible, please quote separately)15.Vendor to supply interferogram for each mirror16.Vendor to measure the microroughness in at least three places on each

mirror with a non contact profilometer.17.NRL to provide shipping containers.Minimum quantity 3 mirrors.

Draft Specifications for Primary

990901EIS_RR_Opt.30

Grating blanks will be fabricated to NRL drawing 3514C.

Ruling frequency: 4200 lines/mm +/- 10 lines/mmgroove uniformity: 0.3 lines/mm over the usable areaoptical figure: toroid, radius geometry shown in drawing 3514C.Dispersion radius (Rt): 1182.94mm (reference dimension) perpendicular to thegroovesCrossed radius (Rs): 1178.28 (reference dimension) parallel to the groovesabove radii are to be perpendicular and parallel to within one arc-minute of thegrooves.centration: toroid vertex to be placed within 0.5mm of the blank centeraverage radius: 1180.6mm +0/-6mmradius ratio: 1.003955 +/- 0.0001surface figure error: <50nm (peak to peak)grating type: holographic laminargroove depth: 60 Angstroms +/- 2 Angstromssurface microroughness: <5 Angstroms required, <3 goalland to groove ratio: 1+/- 0.03

Vendor to provide interferograms of blank figure.Vendor to measure blank microroughness in 3 locations and provide data withgratings.Vendor to perform atomic force microscopy to verify groove depth, land to grooveratio on the gratings.Each grating to be designated with a unique scribed number on the edge.Grating shipping containers to be provided by NRL.

Flight Grating Optical Specifications

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

990901EIS_RR_Opt.32

EIS Is a Stigmatic Spectrometer

990901EIS_RR_Opt.33

EIS Slit and Raster

990901EIS_RR_Opt.34

Instrument Throughput

Throughput for the Entire Optical Chain Has Been Modeled Using

• Mirror Area = 88.4 cm2 (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

990901EIS_RR_Opt.35

Active Region Performance

990901EIS_RR_Opt.36

EIS Quiet Sun Performance

990901EIS_RR_Opt.37

EIS Flare Performance

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: 270.0 Å

– Short Wavelength: 190.0 Å

990901EIS_RR_Opt.39

Long Wavelength Velocity Error Estimates

990901EIS_RR_Opt.40

Short Wavelength Velocity Error Estimates