Armor Simulation Experiments At Dragonfire...
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Armor Simulation Experiments At Dragonfire Facility
Farrokh Najmabadi, John Pulsifer,and Kevin Sequoia
HAPL Meeting
June 2-3, 2004UCLA
Electronic copy: http://aries.ucsd.edu/najmabadi/TALKSUCSD IFE Web Site: http://aries.ucsd.edu/IFE
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Thermo-Mechanical Response of Chamber Wall Can Be Explored in Simulation Facilities
Capability to simulate a variety of wall temperature profiles
Capability to simulate a variety of wall temperature profiles
Requirements:
Capability to isolate ejecta and simulate a variety of chamber environments & constituents
Capability to isolate ejecta and simulate a variety of chamber environments & constituents
Laser pulse simulates temperature evolution
Laser pulse simulates temperature evolution
Vacuum Chamber provides a controlled environment
Vacuum Chamber provides a controlled environment
A suite of diagnostics:Real-time temperature (High-speed Optical Thermometer)Per-shot ejecta mass and constituents (QMS & RGA)Rep-rated experiments to simulate fatigue and material response
Relevant equilibrium temperature (High-temperature sample holder)
A suite of diagnostics:Real-time temperature (High-speed Optical Thermometer)Per-shot ejecta mass and constituents (QMS & RGA)Rep-rated experiments to simulate fatigue and material response
Relevant equilibrium temperature (High-temperature sample holder)
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Status of High-Speed Thermometer
We had achieved excellent reliability Last October: Less than ± 1% change in calibration constant over a 12 day period of tests.~ 2% change in calibration constant after reassembly of thermometer in our new lab. Two issues:
1. Different calibration constants at low and high frequencies!
2. Large ~500 MHz noise in the new lab leading to < ±10% noise in temperature measurements.
We had achieved excellent reliability Last October: Less than ± 1% change in calibration constant over a 12 day period of tests.~ 2% change in calibration constant after reassembly of thermometer in our new lab. Two issues:
1. Different calibration constants at low and high frequencies!
2. Large ~500 MHz noise in the new lab leading to < ±10% noise in temperature measurements.
Single fiber from head to splitter/detector
Band-pass filter/focuser
PMT
Expander/neutral filter
50-50 splitter
PMT
Shorter head.
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450 mJ
Thermometer Is Calibrated Based on The Melting Point of Tungsten
In a set of successive shots, laser energy is increased and temperature measurements have been made. After certain threshold for laser energy, sample temperature does not increase. ⇒ Sample is melted.Calibration constant is determined based on meting point of W (3700 K).Calibration constant during last month run matches those found last September.
In a set of successive shots, laser energy is increased and temperature measurements have been made. After certain threshold for laser energy, sample temperature does not increase. ⇒ Sample is melted.Calibration constant is determined based on meting point of W (3700 K).Calibration constant during last month run matches those found last September.
550 mJ 600 mJ
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Thermometer Measurements Match ANSYS Computations
Jake Blanchard ANSYS Model.8 ns plus.Room temperature initial condition.
Jake Blanchard ANSYS Model.8 ns plus.Room temperature initial condition.
ANSYS Model: Peak Surface Temperature vs. Laser Fluence
0
500
1000
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3500
4000
4500
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
Laser Fluence (J/cm^2)
Tem
pera
ture
(d
eg
C)
Laser fluence is estimated based on laser profile and assuming a reflectivity of ~ 0.4 for W (from tables). Temperature measurement from thermometer (range indicates current noise in the system). No temperature reading at 150 mJ/cm2 shot.
Laser fluence is estimated based on laser profile and assuming a reflectivity of ~ 0.4 for W (from tables). Temperature measurement from thermometer (range indicates current noise in the system). No temperature reading at 150 mJ/cm2 shot.
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ANSYS Model: Thermal Gradient at Surface vs. Laser Fluence
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0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
Laser Fluence (J/cm^2)
dT
/d
z (
deg
C/
nm
)
Both Surface Temperature and dT/dz are Important
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Armor Irradiation Test Matrix
Test environment:Powder metallurgy tungsten samples from Lance Snead.Samples cleaned in sonic bath before test.Laser output energy was fixed. Laser energy on the target was varied using a wave-plate/cube arrangement to ensure constant laser profile on the target.Specular reflected laser light was measured (10-15% of incident laser energy).Post irradiation test: Optical microscopy, WYCO, SEM
Test matrix: Laser energy No. of Shots ConditionSample 1: up to 900 mJ Varied AirSample 2: 150 mJ 100, 1,100, 10,000 VacuumSample 3: 300 mJ 100, 1,100, 10,000 VacuumSample 4: 450 mJ 100, 1,100, 10,000 Vacuum
Test environment:Powder metallurgy tungsten samples from Lance Snead.Samples cleaned in sonic bath before test.Laser output energy was fixed. Laser energy on the target was varied using a wave-plate/cube arrangement to ensure constant laser profile on the target.Specular reflected laser light was measured (10-15% of incident laser energy).Post irradiation test: Optical microscopy, WYCO, SEM
Test matrix: Laser energy No. of Shots ConditionSample 1: up to 900 mJ Varied AirSample 2: 150 mJ 100, 1,100, 10,000 VacuumSample 3: 300 mJ 100, 1,100, 10,000 VacuumSample 4: 450 mJ 100, 1,100, 10,000 Vacuum
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Powder Metallurgy Tungsten Samples After Laser Irradiation
Samples are polished to a “mirror-like”finish. The “damaged” area has a “dull” finish.A brown background is placed in the photograph to enhance contrast.
Samples are polished to a “mirror-like”finish. The “damaged” area has a “dull” finish.A brown background is placed in the photograph to enhance contrast.
1,100 shots1,100 shots 10,000 shots10,000 shots
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False colorFalse color
300 mJ (DT= 2000K, dT/dz=3.5k/nm)50X Optical Microscopy
10,000 Shots1,100 Shots
As seenAs seen
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300 mJ (DT= 2000K, dT/dz=3.5k/nm)500X Optical Microscopy
1,100 Shots
10,000 Shots
No Laser “Transition” Beam Center
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450 mJ (DT= 3000K, dT/dz=5.5k/nm) 500X Optical Microscopy 1,100 Shots
No Laser
“Transition” Beam Center
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450 mJ (DT= 3000K, dT/dz=5.5k/nm) 500X Optical Microscopy Beam Center
No Laser
1,100 shots 10,000 shots
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450 mJ (DT= 3000K, dT/dz=5.5k/nm) 500X Optical Microscopy Transition Region
No Laser
1,100 shots 10,000 shots
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450 mJ (DT= 3000K, dT/dz=5.5k/nm) SEM 100 Shots
No Laser
Beam Center
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SEM Examination of Melted Sample
450 mJ
100 shots
Melted sample
Up to 900 mJ
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Plans for the Next Period
Plans:Repeat experiments with heated samples.Mass loss measurements with RGS and QMS.Higher shot counts.Experiments in intermediate energies: Is there a threshold?Shots with KrF laser (UV) to compare with YAG laser (IR).
Plans:Repeat experiments with heated samples.Mass loss measurements with RGS and QMS.Higher shot counts.Experiments in intermediate energies: Is there a threshold?Shots with KrF laser (UV) to compare with YAG laser (IR).
Questions to Material Working Group:How can we connect microscopic changes in sample to macroscopic changes in properties and lifetime?What should we measure?
Questions to Material Working Group:How can we connect microscopic changes in sample to macroscopic changes in properties and lifetime?What should we measure?