Update on Armor Simulation Experiments At Dragonfire Facility

1
Update on Armor Simulation Experiments At
Dragonfire Facility

• Farrokh Najmabadi, John Pulsifer, Mark Tillack
• HAPL Meeting
• August 8-9, 2006
• General Atomic
• Electronic copy http//aries.ucsd.edu/najmabadi
  /TALKS
• UCSD IFE Web Site http//aries.ucsd.edu/IFE

2
Summary of the Activities

• Homework from MWG
• Measure the vertical size of hills/valleys on the
  exposed samples
• Done. Issues with profiling
• Sample test on a variety of temperatures and
  material.
• Waiting for samples from ORNL
• We had found a definite change in sample response
  at 2,500k.
• Plans from Previous Meeting
• Improve Experimental set up to improve overall
  accuracy.
• New sample positioning system and heater
• New optical train for the thermometer
• Capability to perform experiments with NdYAG
  (IR) and KrF (UV) lasers.
• In-situ and real-time optical microscopy of
  sample evolution

3
Profilmetery of Exposed Samples

• Surface profile of samples were measure with two
  method
• Stylus profiler (advertised resolution nm)
• Optical profiler (advertised resolution nm)
• Results shown in the next slides are for Sample
  11 at 104 shots.

11, 200mJ, 773K, Max 3,000K (2,200K DT)
105 shots
103 shots
104 shots
4
Stylus and Optical Profilers Agree Quite Well
for Smooth Surfaces

• 1D and 2D optical results give significantly
  different Rt
• Reasonable agreement for smooth surfaces
• Optical profile has lower transverse resolution

84 nm
Ra23 nm Rt173 nm
88 nm
5
Stylus and Optical Profilers Do NOT agree for
Exposed Sample (11A)

• Optical profiling is not very trustworthy over
  large vertical ranges, especially when sharp
  vertical features exist
• A stylus can not penetrate as deeply into narrow
  cracks (100 nm max lateral resolution)

Ra1 ?m Rt20 ?m
1.55 ?m
Ra950 nm Rt7480 nm
 6 ?m
6
Surface Profile Measurement

• There is a factor of four difference in Ra
  between Stylus and Optical profilers.
• Neither profilers are meant to be used to
  measure the depth of deep cracks.
• Optical microscopy/SEM of a cut section of a
  sample can be used to calibrate the surface
  profile measurement.

7
Previous Experimental Setup Was Dictated by the
High-Temperature Sample Holder
High-Temperature Sample holder

• All alignment had to be done in air.
• Laser/thermometer head had to be realigned for
  exposure of new portion of the sample.
• No control of diagnostics during the run.
• No external diagnostics capability because sample
  was too far from windows.

QCM
Thermometer head
8
New Experimental Setup
translator electronics
9
New Experimental Setup
10
Precise temperature measurement requires small
enough spot size and sharp image.

• Two-lens formulas were used to roughly size the
  thermometer head and compute the spot size (100
  mm).
• The thermometer head was focused on the sample by
  coupling a diode laser to the fiber and adjusting
  the objective to get a sharp image. The diode
  laser spot was roughly centered in the middle of
  drive laser foot-print.

11
Improvements were made to the precision,
resolution and repeatability of the thermometer
measurements

• We are working on a new thermometer head design
  using free space lenses.
• A CCD camera is used to focus the thermometer
  head correctly and find the exact spot size.
• A three-lens system allows changing the spot size
  (help in setting the light intensity in the
  thermometer and allow for a larger range of
  temperature measurement)
• The objective of the thermometer head is mounted
  on a translation stage which would allow sweeping
  the thermometer spot over the laser beam spot and
  measure temperature profile of the target in real
  time.

12
In-situ microscopy allows us to monitor
microstructure evolution during testing
Basler camera and K2 Infinity microscope 1280x1
024 resolution 25 fps STD
objective (higher mag available)
USAF resolution target - 64 line pairs/mm - 16
?m resolution
13
The In-situ Microscopy Is Operational

• Test of in-situ microscopy was performed with
  another laser which does not have a smooth
  profile too clearly see the results.
• Camera is placed vertically laser profile is
  rotated by 90o

14
Image sequence of W surface evolution
15
Plans

• Complete New Experimental Set-up
• Thermometer with the new imaging system
• In-situ microscopy Different lighting, shutter
  timing,
• Demonstrate operation with KrF laser.
• Sample runs per MWG list.
• We generate a mountain of data before the test
  (cleaning and sample preparation), and during our
  tests (sample temperature, chamber pressure, as
  a function of time)
• Are these data needed?
• If so, how should we to store and report them?

16
Extra Slides
17
Spatial profile of laser
18
Spatial profile of laser
19
Experimental Setup
High-Temperature Sample holder
20
Spectroscopy Confirms Thermometer Measurements
21
Sample behavior changes at 2,500K
22
Armor Irradiation Test Matrix

• Laser Energy Initial Temp (K) Max. Temp (K) DT
  (K)
• 200 773 2,980 2,200
• 100 773 2,200 1,400
• 85 300 1,200 900
• 150 300 2,500 2,200
• 150 773 2,700 1,900
• 50 773 1,200 400
• Samples Powder metallurgy tungsten samples from
  Lance Snead.
• All shot at 103, 104, and 105 shots

• No Visible damage on Samples 13 and 16 (i.e.,
  there is even no discoloration at the laser spot)

23
Damage appears at 2,500K (not correlated with DT)
12A, 100mJ, 773K, Max 2,200K (1,400K DT)
14A, 150mJ, RT, Max 2,500K (2,200K DT)
11A, 200mJ, 773K, Max 3,000K (2,200K DT)
15A, 150mJ, 773, Max 2,700K (1,900K DT)
24
Effects of Shot Rate and Temperature Rise
14A, 150mJ, RT, Max 2,500K (2,200K DT)
15A, 150mJ, 773, Max 2,700K (1,900K DT)
105 shots
103 shots
104 shots
25
Effects of Shot Rate and Temperature Rise
14A, 150mJ, RT, Max 2,500K (2,200K DT)
11A, 200mJ, 773K, Max 3,000K (2,200K DT)
105 shots
103 shots
104 shots
26
Summary and Plans

• 1) It appears that material response (powder
  metallurgy samples) depends sensitively on the
  maximum sample temperature and not on temperature
  rise.
• More sample tests (different laser energies and
  at least two samples per point).
• Test on single-crystal tungsten.
• Repeat experiments with KrF laser
• 2) Thermometer
• Thermometer can measure down to 1,200oC (i.e.,
  1,500oC maximum temperature during the laser
  shot).
• A 1 MHz, steady-state thermometer has been
  deployed on PISCES facility. A 10-MHz version
  will be developed this summer.
• 3) Experimental setup
• Experimental set up has to be modified to improve
  overall accuracy.
• QMS was operational during exposure of samples
  11-15. Material accumulation on QMS crystal was
  similar to tests without the sample. We need to
  establish the baseline for material loss
  experiments.

27
Experimental Setup
High-Temperature Sample holder
28
Summary and Plans

• It would be great if MWG provides input on
  experiments to be conducted, specially with the
  aim of cross-referencing different experiments.
• Run conditions
• Pre and post examination of samples
• We generate a mountain of data before the test
  (cleaning and sample preparation), and during our
  tests (sample temperature, chamber pressure, as
  a function of time)
• Are these data needed?
• If so, how should we to store and report them?
• It would be great to have a standard sample size
  so that we do not need to modify sample holder.