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

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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

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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

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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

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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

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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

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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)

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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

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RadHeat shows that XAPPER can roughly match the predicted peak temperature at a fluence of ~0.7 J/cm2

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0.0 0.5 1.0 1.5 2.0

Time (seconds)

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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:

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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:

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Tungsten roughening experimentsTungsten roughening experimentsat 10 Hz and ~0.7 J/cmat 10 Hz and ~0.7 J/cm22, (Cont’d.), (Cont’d.)

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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

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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

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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

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Backup slidesBackup slides

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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