Armor Simulation Experiments At Dragonfire Facilityaries.ucsd.edu/NAJMABADI/TALKS/HAPL/0406-HAPL-Exp.pdf¾Laser fluence is estimated based on laser profile and assuming a reflectivity

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?