Download presentation
Presentation is loading. Please wait.
Published byPaul Carson Modified over 8 years ago
1
Ion Mitigation for Laser IFE Optics Ryan Abbott, Jeff Latkowski, Rob Schmitt HAPL Program Workshop Atlanta, Georgia, February 5, 2004 This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48
2
Burn and debris ions are a threat to final optics Low chamber pressures result in significant ion fluences to final optics that could induce: –sputtering –roughening, bubbles –changes in optical properties Current design calls for 10 mTorr Xe Original Sombrero burn alphas (188 keV) at 500 mTorr Burn alphas (up to several MeV) at 50 mTorr
3
The ion mitigation concept: protect optics with modest B fields Final Optic Magnetic Field Fusion Chamber Ion Paths Beam Tube Wall Background Gas Helmholtz Coil
4
The DEFLECTOR code predicts ion paths through chamber DEFLECTOR Ion Charge States Stopping in Background Gas B Field Interactions B Field Shape Beam Tube Geometry Target Ion Spectra SRIM Stopping Tables Ion Stopping or Impact Positions Incidence Angles for Wall Impacting Ions Total Energy Deposited in Gas, Wall, and Optic Kinetic Energies of Wall & Optic Impacting Ions
5
DEFLECTOR data can be plotted to visualize multiple effects Three dimensional impact and stopping positions (wall impacting ions with a 0.050 T field) Trend plots (He impact angle characteristics)
6
Modest fields are can deflect ions away from final optics A 0.125T field reduces the total energy incident upon a final optic at 20 m by a factor of 40,000. A 0.150T field can deflect all target burn and debris ions. 0.050T0.100T0.150T
7
Magnets would have modest power requirements r1r1 r2r2 BoBo r z
8
Ions impacting the beam tube wall may cause sputtering HydrogenHelium Carbon Gold
9
Sputtering is enhanced for grazing incidence impacts Gold Stiff ions (high mass, high energy) are more weakly influenced by the magnetic field Ions have initial trajectories ~parallel to tube walls & stiff ions are only perturbed a minor amount strike at grazing incidence. Gold ions illustrate this well Because the entire energy range of gold ions impact at shallow angles, this species may present a serious sputtering threat
10
A sputtering product calculation example for gold DEFLECTOR calculates fluxes and angles for all wall impacting ions. This will allow coupling with SRIM to predict the sputtering threat: Gold Ion Energy (MeV) Impacts @ > 88 o Yield for Iron (atoms/ion) Average Atom Energy (keV) Range in 10mTorr Xe (m) Number of Sputtered Atoms 51.84x10 11 1203.00.342.21x10 13 202.02x10 12 1554.50.413.13x10 14 353.67x10 10 1475.00.435.39x10 12 505.92x10 6 1805.00.431.07x10 9 Depending on where the impact occurs, most or all gold sputtering products may be stopped by the background gas Results may differ for Aluminum or other beam tube materials A gas puff may be required to flush the beam tubes of sputtering products
11
DEFLECTOR will determine sputtering yield and transport SRIM Sputtering Tables Sputtering products and propagation in background gas toward optic Total Ion / Sputter threat to final optics
12
Further work Fully characterize sputtering threat Account for ion charge state distributions and production of neutrals Investigate alternate beam tube geometries to prevent ion backscatter Detailed magnet designs Neutronics analyses Couple DEFLECTOR & RadHeat to characterize beam-tube and optic heating TART Model of Sombrero Chamber
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.