1. Long Term Exposure of Candidate First Wall Materials on XAPPER February – 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.

2. 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...

3. JFL—6/3/04 XAPPER 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

4. JFL—6/3/04 The new chamber gives us a dramatic improvement in efficiency and usability  We took delivery of the new chamber on April 22

5. 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 ~mm 2 )  Were surprised to observe single- shot damage throughout the sample; this indicates a fluence >1 J/cm 2  Now, the challenge is to back off from this maximum fluence in a controlled & predictable manner We have increased our maximum fluence with a better optic and improved alignment 1000 pulses30,000 pulses 3000 pulses10,000 pulsessingle shots

6. JFL—6/3/04 We have increased our maximum fluence, (Cont’d.) Unexposed: 33 nm rmssingle pulse: 290 nm rms 3000 pulses: 4.1  m rms Missing data due to angle being too steep for white-light interferometer to resolve

7. JFL—6/3/04 We have developed the RadHeat code to model pulsed 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/cm 2 –XAPPER rep-rated melt fluence is only ~0.8 J/cm 2

8. 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

9. JFL—6/3/04 RadHeat IFE results

10. 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/m 2 -K)

11. 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

12. JFL—6/3/04 RadHeat shows that XAPPER can roughly match the predicted peak temperature at a fluence of ~0.7 J/cm 2

13. JFL—6/3/04 Tungsten roughening experiments at 10 Hz and ~0.7 J/cm 2 Pre-irradiation: rms = 20 nm peak-valley = 100 nm After 10 4 pulses: rms = 72 nm peak-valley = 780 nm Powder met. exposures:

14. JFL—6/3/04 Tungsten roughening experiments at 10 Hz and ~0.7 J/cm 2, (Cont’d.) Pre-irradiation: rms = 10 nm peak-valley = 52 nm After 3  10 4 pulses: rms = 72 nm peak-valley = 880 nm Single crystal exposures:

15. JFL—6/3/04 Tungsten roughening experiments at 10 Hz and ~0.7 J/cm 2, (Cont’d.)

16. JFL—6/3/04  The foam was hit in 10 spots each for 10 4 pulses  The sample was moved by 500  m between exposures Tungsten foam has been hit with a much higher fluence than in previous experiments Pre-irradiationPost-irradiation

17. 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

18. 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 10 5  Additional foam exposures  how to characterize? Next steps

19. JFL—6/3/04 Backup slides

20. JFL—6/3/04 The XAPPER experiment is used to study damage from x-ray exposures  Source built by PLEX LLC: –Provides x-rays from 80-150 eV –Operation for ~10 7 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