laser requirements and prospects for gemini ao program
Post on 08-Jan-2016
20 Views
Preview:
DESCRIPTION
TRANSCRIPT
Dec. 7, 1999 Laser Development Meeting 1
Laser Requirements and Laser Requirements and ProspectsProspects
for Gemini AO Programfor Gemini AO Program
Céline d’OrgevilleGemini Laser Systems Engineer
Dec. 7, 1999 Laser Development Meeting 2
Gemini AO programGemini AO program
NORTH
SOUTH
1999
2000
2001
2002
2003
2004
Altair w/ NGSAltair w/ NGSAltair w/ LGSAltair w/ LGS
Hokupa’aHokupa’a 3636 8585
2W LGS2W LGSCP Hokupa’aCP Hokupa’a 8585
CP Multi-LGS MCAOCP Multi-LGS MCAO
Dec. 7, 1999 Laser Development Meeting 3
CP LGS AO System CP LGS AO System parametersparameters
• AO = Hokupa’a 85 elements – curvature WFS– 85 subapertures– 1 kHz frame rate– 70 to 80 photodetection events/subap./frame– 8-1 SNR
• LGS– 1 Laser Guide Star– 2W dye laser
Dec. 7, 1999 Laser Development Meeting 4
MK LGS AO System MK LGS AO System parametersparameters
• AO = ALTAIR – Shack-Hartmann WFS– 12x12 subapertures– 500 Hz to 1 kHz frame rate– 310 to 800 photodetection events/subap./frame– 15-1 to 25-1 SNR– 0.04 to 0.08 arcsec tilt measurement accuracy– 0.05 to 0.1 m rms WF through servo
• LGS– 1 Laser Guide Star– High power laser (Spec. is 12 W equivalent CW laser)
Dec. 7, 1999 Laser Development Meeting 5
CP multi-LGS MCAO System CP multi-LGS MCAO System parametersparameters
• MCAO – 2 to 3 DMs, 4 to 5 WFSs– 12x12 to 16x16 subapertures– 500 Hz to 1 kHz frame rate– 200 to 500 photodetection events/subap.(16x16)/frame– 10-1 to 20-1 SNR– 0.05 to 0.10 arcsec tilt measurement accuracy– 0.05 to 0.1 m rms WF through servo
• LGS– 4 to 5 Laser Guide Stars– High power lasers (Spec. similar to MK or somewhat lower)
Dec. 7, 1999 Laser Development Meeting 6
Laser systems requirementsLaser systems requirements
Laser requirements CP LGS AO MK LGS AO CP multi-LGS MCAO
Average power2 W CW laserGoal: 3W CW laser
12 W equiv. CW laserGoal: 18 W equiv. CW laser
< 5x 12 W equiv. CW laser
Beam quality < 1.5 DL1
ReliabilityMTBF (critical) > 900 h of operationMTBF (minor) > 100 h of operation
Staffing 1 laser specialist + 2 laser technicians for both MK and CP
Laser delivery Oct. 2000 Jan. 2001 June 2003
System operation Aug. 2001 Jan. 2002 March 2004
Observation use Once every other night (12 hours)
1 DL = Diffraction Limited2 MTBF = Mean Time Between Failure
Dec. 7, 1999 Laser Development Meeting 7
Laser systems power & Laser systems power & beam quality requirementsbeam quality requirements
• CP LGS AO system(1) Simulation of 85 actuator curvature sensor
performances with LGS (F. Rigaut’s AO modeling code)
(2) Derive CW laser power requirement using J. Telle’s “slope efficiency” number
(3) Compared the power requirement with Imperial College theoretical calculations & achieved experimental photon returns
Dec. 7, 1999 Laser Development Meeting 8
Laser systems power & Laser systems power & beam quality requirementsbeam quality requirements
• MK LGS AO system(1) Simulation of 12x12 subap. Shack Hartmann WFS
performances with LGS (F. Rigaut’s AO modeling code) for an ideal gaussian beam at zenith
(2) Derive power requirements for different laser formats using J. Telle’s “slope efficiency” numbers
(3) Multiply by coeff. 2 (resp. 3) to set the power requirements (resp. goal) while taking real laser beam and 45 degree elevation angle specification into account
Dec. 7, 1999 Laser Development Meeting 9
Laser systems power & Laser systems power & beam quality requirementsbeam quality requirements
• CP multi-LGS MCAO system(1) Optimal estimator calculations with Brent
Ellerbroek’s AO modeling code, using MTF-based approach to model LGS shape and WFS measurement accuracy (0 and 45 degree calculations, beam quality, lenslet and CCD degradations included)
(2) Derive power requirements for different laser formats using J. Telle’s “slope efficiency” numbers
Dec. 7, 1999 Laser Development Meeting 10
Promising laser design Promising laser design approachesapproaches
• Compact and potentially reliable sources like diode-pumped solid-state lasers and fiber lasers
• Among them:- Sum-frequency solid state lasers
› Thin disk laser (Nanolase, France – John Telle, SOR)› “Standard” Nd:YAG zig-zag slabs (Lincoln Lab, Tom Jeys –
UoChicago, Ed. Kibblewhite & Lite Cycles, LLNL …)
- Raman laser (UoArizona, Tom Roberts -…)- Raman fiber laser (Lite Cycles - IRE-POLUS Group,
Germany)
• And very likely others than we might not be aware of…
Dec. 7, 1999 Laser Development Meeting 11
Key physics and Key physics and engineering issuesengineering issues
• Sum frequency lasers: – heat management in the laser crystals (power
limitation) and 1.32 m laser (difficult to build)
• Fiber lasers: – too wide a spectral bandwidth due to Brillouin
scattering
• General: – insufficient level of automation
Dec. 7, 1999 Laser Development Meeting 12
Gemini prospects for laser Gemini prospects for laser R&DR&D
• No R&D currently supported• Required development schedule
– related to the MCAO laser systems delivery dates (June 2003)
• R&D activities should start by the end of 2000• R&D activities should focus on key components
for operational high power lasers– Examples: 1.32 m laser, sum-frequency mixing in
non-linear crystals at high power levels, narrow-band fiber lasers, etc.
top related