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IFE foam characterizationAbbas Nikroo, Fred Elsner, Annette Greenwood
High Z coatings for IFE applicationsAbbas Nikroo, Elizabeth Stephens, Ron Petzoldt,
Matthew Dicken, Annette Greenwood
Presented at the HAPL Review MeetingNovember 13-14, 2001
Pleasanton, Ca
Report on foam characterization
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Pixels
Transmission profile through NC region
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Transmission profile through similar walls
Acrylic rod
Foam annulus
TMPT foam shellIn isopropanol
xx
OD ≈ 800 µm
Shadowgraphy may be used to measure diameter, OOR and NC
Idea: use foam annulus of accurately know dimensions as surrogate for shells
Acrylic mold dissolved in foam casting solvent at polymerization temperatures!
Machinedmold
Areal density uniformity may be measured by IR absorption
Foam Wedge in CS2
Logo viewed through ~1mm of DVB foam
Foam is placed in index matched fluid to eliminate scatteringIndex matching fluid is non-organic to avoid cluttered IR spectrum
IR Beam
IR absorption by DVB lines provides areal density uniformity information
Dibutyl phthalate
DVB foam in CCl4
exchange
Solvent exchange is in process to clean up IR spectrum
Samples still contain significant amounts of the
foam solvent dibutyl phthalate
… will continue solvent exchange- determine viability of method
High Z coatings
Gold coated polymer shells
Project objectives and summary
• Deposit high Z coatings : Au Pd Au-Pd – sputter coated
– Deposition conditions
• Coat foam shells :
• full density polymer shells, poly-alpha-methylstyrene (PAMS), as surrogates
• Target survival calculations :
• Measure reflectivity of deposited films
• Expect : Au better than Pd
• Fill time-Tritium inventory
• Measure permeability of deposited films
• Expect: Pd better then Au
• Does rapid filling with Pd outweigh the loss in reflectivity?
• What are the properties of Au-Pd mixtures?
Reported on at last meeting-reviewed here
Coating thickness measurements:
Coating uniformity on the shell Shell-to-shell variations within a batch Batch-to-batch variations Used X-ray fluorescence measurements
Reflectance measurements of deposited films
Ellipsometry: determines n,k: optical constants- can calculate reflectivity, R( need to send out-takes time!- VIS+NIR+IR
Direct measurements: In house at GA: Vis+IR-used as check on ellipsometry data In our lab at GA: IR only- used for scoping studies
Permeability measurements on shells
Tests for anticipated problems with Pd exposure to D2
A number of different measurements need to be performed on coatings
Electro-magnetic shaker
High Z target
Bounce Pan
Knobs:
Pressure Power Source-to-substrate distance Bouncing
Ar+
High Z coating are deposited by physical vapor deposition: sputtering
Shells bounce vigorously during coating process
Proper bouncing leads to very uniform coatings
Coating thickness is normally measured by using a witness plate
A=R2
A=4R2
Coatings on shells :
4x less than flats
Scattering => variable factor
Using Witness Plate to Predict Thickness
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Time of Run
Witness Prediction
XRF Prediction
Witness plate measurement is an indirect measurement of thickness on shells
X-ray fluorescence (XRF) can give a direct measurement
Bounce Pan
Witness Plate not where shells bounce
Geometrically
ExcitationX-ray beam
Au X-rayfluorescence
X-ray detector
Au coating
Side View
Two wall Au fluorescencePolymer shell x-ray absorbance is negligible
Eventual beam block forsingle wall measurement
X-ray fluorescence measurements allow more accurate determination of high Z coating thickness and uniformity
Top View
Rotating shell gives two wall uniformity:w+w’
Since one wall is fixed while rotatingThis gives one wall uniformity as well
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Gold thickness measurements
y = 0.9205x
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Thickness by XRF, Å
Used for calibration of x-ray data
X-ray fluorescence gave an accurate measure of gold thickness on flats (calibrated against AFM)Error bar are self-imposed limits of ± 10%
X-ray fluorescence measurements were calibrated against atomic force microscope measurements
Au Shells Permeability v. PAMS
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Gold coated shells were permeable to He and D2 …
… however, permeation time approx. 6-10 times longer than the polymer~ 220-390 A coating
Reflectivity of 400A deposited Au film ~ 96%
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Pd-90 deg sputterPd 45 deg sputter
Wavelength, µm
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Deposition conditions can dramatically affect reflectivity of coatings
90 degree deposition
45 degree depositionUsed in co-sputtering
Shell to shell collisions are probably responsible for small defects on shell surfaces
10 µm
Elimination of these defects needs to be studied
patches
High Z coatings of a number of different compositions have been made
Au only 100 -
Pd only - 100
Au-Pd 51 49Au-Pd 69 31Au-Pd 79 21
Pd+ 80 A Au 15 86
Coating Au at.% Pd at.%
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Permeability Reflectivity