Transcript The Instrument: Optical Design

The Instrument: Optical Design
Dr. Charles M. Brown
US Instrument Scientist
Naval Research Laboratory
202-767-3578
e-mail: [email protected]
990901EIS_Opt.1
Dr. John T. Mariska
Data Coordination Scientist
Naval Research Laboratory
202-767-2605
e-mail: [email protected]
EIS Instrument Schematic
Sun
Filter
Primary
Slit
CCD Long
CCD Short
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Grating
EIS Design Optimization Criteria
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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
•
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Detector Must Clear Input Path (etc.)
EIS-7Tr Design Heritage
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Trendy: Paraboloid Telescope
– Only Two Reflections
990901EIS_RR_Opt.4
•
SERTS: Toroidal Grating
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J-PEX: Laminar Rulings
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EIT and Trace: Sectored Multilayer Coatings
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Sumer: Primary Mirror Scan Concept
Transmission of Al Filter
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F/13 Off-Axis Parabola
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Spot Diagrams for 0, ± 4 arc min
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Summary: RMS Blur of Primary

(arc min)
0
1
2
3
4
5
10
15
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X (E-W)
RMS
blur
(m)
0
0.48
0.96
1.43
1.91
2.38
4.76
7.12
X
RMS blur
(arc sec)
Y (N-S)
RMS blur (m)
Y
RMS blur
(arc sec)
0
0.048
0.096
0.143
0.191
0.238
0.476
0.712
0
0.44
0.89
1.33
1.77
2.20
4.43
6.67
0
0.044
0.089
0.133
0.177
0.220
0.443
0.677
EIS-7TR Spectrometer Layout
Slit
Grating
270A
190A
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Comparison of Designs - Summary
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EIS-7T Layout
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EIS-7TR Spectrometer Layout
270 Å Band
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EIS-7Tr
Super-Optimized by Roger Thomas
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EIS-7Tr Spot Diagrams
and Histograms
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EIS-7Tr Field of View 190 Å
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EIS-7Tr Spot Diagrams 170 - 210 Å
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EIS-7Tr Spectral and Spatial Resolution
Curved Focal Surface - Short  Band
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EIS-7Tr Spectral and Spatial Resolution
Flat Focal Surface - Short  Band
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EIS-7Tr Spot Diagrams 250 - 290 Å
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EIS-7Tr Field of View 270 Å
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EIS-7Tr Spectral and Spatial Resolution
Flat Focal Surface - Long  Band
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Detector Locations - Summary
Grating and
Wavelength
4200 l/mm
270 Ѓ
190 Ѓ
4800 l/mm
270 Ѓ
190 Ѓ
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DetХr X
(mm)
DetХr Z
(mm)
DetХr 
(deg)
131.243 -432.865 5.9544
163.172 -430.810 5.1353
76.224 -438.728 4.5761
115.014 -435.483 5.5044
Multilayer Gratings Characterized
by NRL
Groove Freq.
Groove Area
Optical Figure
Fabrication*
Microroughness
Manufacturer
Multilayer
Period
Bilayers
4800 g/mm
40x40 mm2
Flat
3600 g/mm
19 mm
Flat
3600 g/mm
25x75 mm2
ROC 4 m
RRB, 3.8o
12-20 Å
Hitachi
HIEB, 3o
8Å
Tayside
RRB, 3.1o
10 Å
B&L
SKYLAB
HIEL, 62 Å
3Å
Zeiss
J-PEX
HIEL, 40 Å
5-8 Å
Zeiss
HIEB, 2o
5Å
Tayside
HIEB, 2.7o
8-15 Å
Shimadzu
RRB, 2o
3600 g/mm
80x160 mm
ROC 4 m
2400 g/mm
Flat
2400 g/mm
25x75 mm2
ROC 2.2 m
2400 g/mm
10x10 mm2
ROC 2.2 m
2400 g/mm
Reference
Vol., Page
Year
Mo/Si
128.4 Å
18
Mo/Si
67.5 Å
35
Mo/Si
71.0 Å
23
Peak Wavelength
Angle of Incidence
Overall Eff., Groove Eff.
1st Order
2nd Order
225 Å
125 Å
10o
6o
2.6%, 19%
0.3%, 4%
128 Å
10o
13%, 23%
300 Å
135 Å
10o
10o
- , 40%
1.5%, 4.7%
MoC/Si
128 Å
10
235 A
5o
10.5%, 35%
Appl. Opt.
Mo/Si
79 Å
30
Mo/Si
154 Å
25
Mo/Si
150 Å
10o
16%, 33%
Appl. Opt.
36, 8206
1997
Appl. Opt.
34, 7347
1995
J. El. Spectr.
80, 473
1996
Appl. Opt.
32, 4890
1993
Appl. Opt.
32, 2422
1993
Mo/Si
73.2 Å
ROC 2.2 m
Hyperfine
40
2400 g/mm
RRB, 2o
Mo/Si
290 Å
162.5 Å
14o
ROC 2.2 m
Hyperfine
30
2.5%, 10%
*
RRB=Ruled Replica Blazed, Blaze Angle
HIEB=Holographic Ion-beam Etched Blazed, Blaze Angle
HIEL=Holographic Ion-beam Etched Laminar, Groove Depth
990901EIS_RR_Opt.23
147 Å
10o
7.5%, 27%
195 Å
10o
0.2%, 1%
139 Å
10o
2.2%, 4.4%
151 Å
14o
1.5%, 4.5%
Appl. Opt.
April 1
1999
Appl. Opt.
34, 7338
1995
Appl. Opt.
34, 6453
1995
NRL Experience With Zeiss Holographic
Ion-Etched Laminar Gratings
Parameter
Test Grating1
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 m-1)
5Å
3Å
Peak Eff., Groove Eff.
, Order, Angle
16%, 34%
150 Å, +1, 10o
10.5%, 35% (best)
235 Å, +1, 5o
1Seely, Applied
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Rocket Spectrometer2
Optics 36, 8206 (1997) 2J-PEX mission, Ray Cruddace and Mike Kowalski
AFM Image of a Zeiss Holographic
Grating
40 A
4167 A
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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.26
Groove Efficiency
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•
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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.27
Multilayer Grating Efficiency
Efficiency in the Two Wavebands in Diffraction Orders 1 - 3
990901EIS_RR_Opt.28
Draft Specifications for Primary
1. Figure: Off-axis Parabola
2. 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") TBD
7. Surface microroughness <5 rms, 3 goal
8. Material Premium grade Zerodur or ULE TBD
9. Surface Quality 20/10 goal, 40/20 required
10.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 mirror
16.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.
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Flight Grating Optical Specifications
Grating blanks will be fabricated to NRL drawing 3514C.
Ruling frequency:
4200 lines/mm +/- 10 lines/mm
groove uniformity: 0.3 lines/mm over the usable area
optical figure:
toroid, radius geometry shown in drawing 3514C.
Dispersion radius (Rt): 1182.94mm (reference dimension) perpendicular to the
grooves
Crossed radius (Rs): 1178.28 (reference dimension) parallel to the grooves
above radii are to be perpendicular and parallel to within one arc-minute of the
grooves.
centration:
toroid vertex to be placed within 0.5mm of the blank center
average radius:
1180.6mm +0/-6mm
radius ratio:
1.003955 +/- 0.0001
surface figure error: <50nm (peak to peak)
grating type:
holographic laminar
groove depth:
60 Angstroms +/- 2 Angstroms
surface microroughness:
<5 Angstroms required, <3 goal
land to groove ratio: 1+/- 0.03
Vendor to provide interferograms of blank figure.
Vendor to measure blank microroughness in 3 locations and provide data with
gratings.
Vendor to perform atomic force microscopy to verify groove depth, land to groove
ratio on the gratings.
Each grating to be designated with a unique scribed number on the edge.
Grating shipping containers to be provided by NRL.
990901EIS_RR_Opt.30
Scientific Performance
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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
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Modeled the Instrument Throughput
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Simulated the Ability of the Instrument to Measure Doppler Shifts and
Nonthermal Velocities As a Function of Count Rate
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EIS Is a Stigmatic Spectrometer
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EIS Slit and Raster
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Instrument Throughput
Throughput for the Entire Optical Chain Has Been Modeled Using
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Mirror Area = 88.4 cm2 (Half of a 15 cm Diameter Mirror)
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Grating Groove Efficiency = 0.40
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Detector Quantum Efficiency = 0.80
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Obscuration by Front Filter Support Structure = 0.80
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Obscuration by Mesh Supporting Front Filter = 0.80
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Wavelength-Dependent Transmission Curves for Two Thin Al Filters
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Wavelength-Dependent Multilayer Efficiencies for Mirror and Grating
Computed by J. Seely
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Slit Width = 1 Arcsec
•
Solar Spectra Computed Using Chianti Atomic Physics Database and
Emission Measure Curves for Quiet Sun, Active Regions, and Flares
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Active Region Performance
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EIS Quiet Sun Performance
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EIS Flare Performance
990901EIS_RR_Opt.37
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.38
Long Wavelength
Velocity Error Estimates
990901EIS_RR_Opt.39
Short Wavelength
Velocity Error Estimates
990901EIS_RR_Opt.40