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
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)
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.
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
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
1500
2000
2500
3000
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.
ANSYS Model: Thermal Gradient at Surface vs. Laser Fluence
0
1
2
3
4
5
6
7
8
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
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
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
False colorFalse color
300 mJ (DT= 2000K, dT/dz=3.5k/nm)50X Optical Microscopy
10,000 Shots1,100 Shots
As seenAs seen
300 mJ (DT= 2000K, dT/dz=3.5k/nm)500X Optical Microscopy
1,100 Shots
10,000 Shots
No Laser “Transition” Beam Center
450 mJ (DT= 3000K, dT/dz=5.5k/nm) 500X Optical Microscopy 1,100 Shots
No Laser
“Transition” Beam Center
450 mJ (DT= 3000K, dT/dz=5.5k/nm) 500X Optical Microscopy Beam Center
No Laser
1,100 shots 10,000 shots
450 mJ (DT= 3000K, dT/dz=5.5k/nm) 500X Optical Microscopy Transition Region
No Laser
1,100 shots 10,000 shots
450 mJ (DT= 3000K, dT/dz=5.5k/nm) SEM 100 Shots
No Laser
Beam Center
SEM Examination of Melted Sample
450 mJ
100 shots
Melted sample
Up to 900 mJ
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?