ELT Studies in Japan Masanori Iye (NAOJ)

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ELT Studies in JapanMasanori Iye (NAOJ)

• ReOrganization of NAOJ4 to NINS (as of Apr. 1,
  2004)
• 3 times larger in budget and staff, increased
  flexibility?
• Future Planning WG for Opt/IR community
• gt White Book (2004 summer)
• No Specific Budget for ELT RD
• gt request for 5 year RD budget to
  JST/MEXT
• Yet, some studies are under way for a 30m JELT.
• Reports on individual studies
• Caution including yet-personal
  perspectives!

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Baseline Specification Japan ELT
M1 F/1.5, segmented 30m, CFRP/Glass/Ceramic TBD
M2, M4 3 aspheric mirror system, adaptive M2,M4
Foci 2 (4) Nasmyth focal stations, No aberration
FOV 10 arcmin radius half circle, flat focal plane
?bands 0.39-5 micron
Instruments Opt Spectrograph, IR Spectrograph, Cameras..
Enclosure Diameter lt 90m

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Some new initiatives

• Optical design 3 Aspheroc mirrors (Nariai/Iye)
• Coated CFRP replication segment (Mitsubishi/NAOJ)
  
• ZPF segment(Taiheiyo Cement/NAOJ)
• High precision grinding machine (Nagase Integrex)
• Light weight structure (Nagoya Univ., Mitsubishi)
• Direct Drive Motor (Mitsubishi)
• Segment support adjust (Kyoto Univ., Melco)
• ELID grinding (RIKEN)
• LGS 188 element AO (NAOJ)
• AO PSF Simulations (NAOJ)
• Site Study(NAOJ)

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Optics 3 Asph. Mirror Telescope (Nariai/Iye)

• characteristics
• /aberration free
• /flat image plane
• /M4 conjugate to
• 16km
• /shorter telescope
• /two arms on each Nasmyth stage
• 4m DMs?

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JELT Optics Layout
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Superb image quality diffraction size_at_0.6um10mas
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CAD Model 30m telescope with 3 aspheric mirrors
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Nasmyth layout
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FEM analysis for JELT
AZ Thrust Hydrostatic Bearing with Drive
Journal
EL Radial and Thrust Hydrostatic Bearing with
Drive
Yoke Structure
AZ Track
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Characteristics of Yoke Structure
Tube (assumed mass 750 tons)
Yoke (Mass 350 tons)
Natural Frequency Analysis Model
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Segment Fabrication

• New zero-expansion material for segments
• 1) coated CFRP replica fabrication(Melco)
• gt low cost, suppression of humidity
  deformation
• 2) ZPF grinding/polishing
• Zero-expansion Pore-Free ceramic (Japan
  Ceratech/ Taiheiyo cement)
• Direct Grinding (Nagase Integrex)
• no/little polishing gt reduction of
  time/cost

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Test on coated CFRP

• Cyanate CFRP
• CTE 30ppb /C, light weight 1.5g/cm3
• Cheaply replicated from mother mold.
• Affordable surface roughness
• Deformation for absolute dehydration 20ppm
• with time scale of 500hrs
• Water tight coating to give 100 times longer
• time scale may give lt 3ppb change in 1 hour.
• Need for static correction?

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Weight increase rate of dehydrated CFRP due to
moisture absorption in laboratory

• 
  
  
  

No Material Coating
1 Epoxi NM-35 No
2 Cyanate EX1515 No
3 Cyanate NM-25 No
4 Cyanate EX1515 0.3um
5 Cyanate EX1515 0.6um
6 Cyanate EX1515 15um
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CFRP Tests at Subaru enclosure

• Cyanate CFRP protected by Al foil was monitored
  for its weight variation at 10-7 mass resolution
  during three months at Mauna Kea.

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• /Deformation due to the variable moisture content
  in 2 months was 220ppb, 4 times larger than
  thermal deformation of ULE, 60ppb, for 20C
  change.
• gt Reducable by optimizing plastic material
  and/or carbon content?

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Zero-expansion Pore-Free CeramicJapan
Ceratech/Taiheiyo Cement

• Thermally zero-expansion material (10ppb)
• Stronger than glass for damaging ( twice)
• Machinable and polishable just like glass.
• Aluminum deposition can be made.
• Follows temperature variation 3 times faster than
  glass.
• Acceptable surface roughness (a few nm rms).
• Light weight structuring and sagged disk feasible
  
• New facility plan for production of larger disks.
• Somewhat less expensive than glass(?)

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Physical characteristics of materials
Unit CFRP C/SiC Glass ZPF
Young modulus E 120 400 90 150
Density ? g/cm3 1.5 2.65 2.53 2.54
CTE a ppm/K 0.03 2.6 0.02 0.02
Conductivity ? 50 125 1.6 5.3
Heat Capacity - - 820 800
Max Stress 800 175 80 240
Roughness rms nm 7.4 1 4
Stiffness/mass E/? 80 150 35 60
Thermal stability ?/a 1700 50 80 260
Size lt 2m lt 2m lt8m lt1m
Cost low high high medi
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Long-term stability

• Zero-expansion Pore Free ceramic ZPF (Taiheiyo
  Cement)

Event Date Surface Errot (?) Refl.
As polished As polished Jan. 2001 0.045 87
1.5 year later 1.5 year later May,2002 0.048 -
Heated to 250 C Heated to 250 C June, 2002 0.050 -
2.0 year 2.0 year Jan., 2003 0.052 -
2.5 year 2.5 year May, 2003 0.042 -
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Zero-expansion Pore-Free Ceramic (ZPF)10ppb(at
0C), High elasticity, Pore-free, Cementable,
Long term stability, Light weight structure,
Polishable

• Polished at NAOJ
• roughness7nm rms

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30cm ZPF honeycomb mirror

• Honey comb structure
• 2.4 gt 1.7g/cm3 (30 reduction)
• Polished by NIKON to 1/12 ?rms without a
  problem
• No apparent print through of back
• structure

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RMS 14nm surface roughness
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High Precision Grinding Machine (Nagase Integrex)

• Work stage up to 4mx2m!
• Friction free hydrostatic bearing gt 10nm
  accuracy
• 1nm resolution
• Dynamic balancing of spinning tool

Yamagata Industrial Research Inst.
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High Precision Nagase Grinding Machine

• FMOS aspheric Schmidt plate 28x24cm, loose
  specification for fiber imaging
• One-time grinding off
• Roughness 80nm
• Figure error 200nm metrology measurement
• Iterative grinding with optical interferometric
  measurement has just tested on 10cm ZPF.

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1st NC grinding experiments

• Three 10cm ZPF disks ground to R30cm sphere
• ZPF1 rotated, 1500,
• ZPF2 rotated, 3000, a few hours work,
• (smaller R at the center)
• but surface error lt 3 ?over 65 of the
  surface
• ZPF3 raster scanned, 0.5mm then 0.1mm pitch,
  overnight grinding gt (grinding tracks visible)
  
• figure error under evaluation.
• Remember this is the result of first 5 days and
  optimizations of parameters are yet to be seeked
  for!!!

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1st NC grinding w. rotation

• 3000 grit, PVlt3?(over 65 area)

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1st NC grinding in raster mode
1st day(June 17th) result PRELIMINARY
Apparently needs to optimize the grinding head
shape, pitch, speed of raster
0.5mm 0.1mm
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Light Weight Structure
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Solid-State Sum Frequency Generating Sodium Laser
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(Laser Diode pumped) Mode-locked NdYAG Lasers
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SUMMARY

• Experiencing to have a major reformation of
  research organizations and is hoping to take this
  chance to promote an ELT plan.
• Has some expertise around Subaru Telescope
• Inviting a few new industries for RDs toward
  cost saving realization of ELTs.
• Tentatively drawing a 30m ELT plan.
• Applying for a 11M RD budget to MEXT/JST
• Is open for participating in international
  collaboration to construct ELTs.