long term exposure of candidate first wall materials on xapper february – may 2004 presented by:...
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Long Term Exposure ofLong Term Exposure ofCandidate First Wall Materials on XAPPERCandidate First Wall Materials on XAPPER
February – May 2004February – May 2004
Presented by: Jeff Latkowski
XAPPER Team: Ryan Abbott, Robert Schmitt, Susana Reyes, Ron Pletcher
HAPL Program Workshop
UCLA
June 3, 2004
Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.
JFL—6/3/04
Installation of the new chamber
Modeling of pulsed x-ray and ion heating with RadHeat
Sample exposures:– Powder met tungsten– Single crystal tungsten– Tungsten foam
Upcoming plans
XAPPER has had an eventful few months...XAPPER has had an eventful few months...
JFL—6/3/04
XAPPER now has a new vacuum chamberXAPPER now has a new vacuum chamber
The new chamber provides us with nearly 5 the volume of the original chamber:– Necessary to field advanced diagnostics and control systems– Larger sample tray able to handle sample heater (to 1200ºC)– New sample manipulator provides x-y motion for higher precision and
more efficient use of samples– In-chamber motor-controlled optic manipulator system (3-axis) reduces
wobbling and frees up space on chamber top plate– In-chamber breadboard for mounting of auxiliary components (e.g.,
mirror for viewing of sample surface during irradiation)– Designed to accommodate in-situ laser diagnostic and UCSD’s optical
thermometer– More (and larger) ports for easy access– D. V. Manufacturing (Livermore) delivered on schedule (4 weeks) and
for less than our planned budget
JFL—6/3/04
The new chamber gives us a dramatic The new chamber gives us a dramatic improvement in efficiency and usabilityimprovement in efficiency and usability
We took delivery of the new chamber on April 22
JFL—6/3/04
Powder met tungsten sample #2:– Sample size 5.7 6.2 mm– Initial roughness ~50 nm rms in center
(typical value over any ~mm2)
Were surprised to observe single-shot damage throughout the sample; this indicates a fluence>1 J/cm2
Now, the challenge is to back off from this maximum fluence in a controlled & predictable manner
We have increased our maximum fluenceWe have increased our maximum fluencewith a better optic and improved alignmentwith a better optic and improved alignment
1000 pulses30,000 pulses
3000 pulses 10,000 pulses single shots
JFL—6/3/04
We have increased our maximum fluence, We have increased our maximum fluence, (Cont’d.)(Cont’d.)
Unexposed: 33 nm rms single pulse: 290 nm rms
3000 pulses: 4.1 m rms
Missing data due to angle being too steep for white-light interferometer to resolve
JFL—6/3/04
We have developed the RadHeat code to modelpulsed thermal transients in the first wall and optics
RadHeat is a 1-D heat transfer code for use with multi-material walls irradiated by any number of photon and/or ion spectra in pulsed environments
We are using RadHeat to model the wall temperature response for various materials, target spectra, chamber radii, etc.
We consider not only the first pulse, but the rise to a steady-state condition as well:– XAPPER single-shot melt fluence for tungsten is ~1 J/cm2
– XAPPER rep-rated melt fluence is only ~0.8 J/cm2
JFL—6/3/04
RadHeat IFE results for 8 m radius, 154 MJ target,and 10 mTorr Xe gas. Armor is 1 mm W + 3.5 mm Fe
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RadHeat IFE results
JFL—6/3/04
RadHeat IFE results
T at tungsten/ ferritic steel interface is only ~15 K
Front surface of ferritic steel ratchets up to steady-state temperature of~960 K (assuming back surface heat transfer coefficient of 10 kW/m2-K)
JFL—6/3/04
RadHeat IFE results
We consistently predict a higher peak temperature than that reported by Rene Raffray
We are working with Rene to determine the differences in our calculations
We predict melting on the first shot
JFL—6/3/04
RadHeat shows that XAPPER can roughly match the predicted peak temperature at a fluence of ~0.7 J/cm2
0
500
1000
1500
2000
2500
3000
0.0 0.5 1.0 1.5 2.0
Time (seconds)
Su
rfa
ce
te
mp
era
ture
(K
)
JFL—6/3/04
Tungsten roughening experimentsTungsten roughening experimentsat 10 Hz and ~0.7 J/cmat 10 Hz and ~0.7 J/cm22
Pre-irradiation:
rms = 20 nm
peak-valley = 100 nm
After 104 pulses:
rms = 72 nm
peak-valley = 780 nm
Powder met. exposures:
JFL—6/3/04
Tungsten roughening experimentsTungsten roughening experimentsat 10 Hz and ~0.7 J/cmat 10 Hz and ~0.7 J/cm22, (Cont’d.), (Cont’d.)
Pre-irradiation:
rms = 10 nm
peak-valley = 52 nm
After 3 104 pulses:
rms = 72 nm
peak-valley = 880 nm
Single crystal exposures:
JFL—6/3/04
Tungsten roughening experimentsTungsten roughening experimentsat 10 Hz and ~0.7 J/cmat 10 Hz and ~0.7 J/cm22, (Cont’d.), (Cont’d.)
JFL—6/3/04
The foam was hit in 10 spots each for 104 pulses The sample was moved by 500 m between exposures
Tungsten foam has been hit with a muchTungsten foam has been hit with a muchhigher fluence than in previous experimentshigher fluence than in previous experiments
Pre-irradiation Post-irradiation
JFL—6/3/04
Two key experimental uncertainties remain
A good measurement of the x-ray fluence is difficult to obtain:– Since focused beam is able to melt even tungsten, cannot use pinhole in
front of photodiode– Filtering at an unfocused location / avoid plasma formation at pinhole:
• Very thin (<100 nm) filters are very expensive, especially at large aperture• Thicker filters are relatively cheap, but error bars on the thickness render
measurements useless (4 m Zr foil gives large attenuation, but 10% uncertainty gives rise to huge fluence uncertainty)
The temporal output is also somewhat uncertain:– 40 ns pulse length based upon PLEX’s current risetime measurement
Non-contact optical thermometer should help in both respects:– Fluence measurement is only needed in order to predict temperature– Temporal resolution is adequate to resolve x-ray heating pulse
JFL—6/3/04
Enhance diagnostic capabilities:– Install fast optical thermometer (from UCSD) in late-June/early-July– Bring CCD imaging system to the Advanced Light Source for
calibration of camera/filtering system– In-situ laser surface diagnostic for real-time surface characterization– Bring up residual gas analysis system
Additional tungsten roughening studies:– Utilize sample heater start sample at 500ºC– Measure temperature history and adjust fluence to match peak
temperature predictions for IFE armor– Expose single crystal and powder met. tungsten to various numbers
of pulses from 1 to 105
Additional foam exposures how to characterize?
Next stepsNext steps
JFL—6/3/04
Backup slidesBackup slides
JFL—6/3/04
The XAPPER experiment is usedThe XAPPER experiment is usedto study damage from x-ray exposuresto study damage from x-ray exposures
Source built by PLEX LLC:– Provides x-rays from 80-150 eV
– Operation for ~107 pulses before minor maintenance
– X-ray dose can be altered by changing focus, voltage, gas pressure or species
– Facility is flexible and dedicated to the study of x-ray damage
Z-pinchplasma
Ellipsoidalcondenser
Sample plane
Z-pinchplasma
Ellipsoidalcondenser
Sample plane
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