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UID:UW-Physics-Event-3317
DTSTART:20140407T170000Z
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DTSTAMP:20260419T193541Z
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LOCATION:2241 Chamberlin
SUMMARY:The Plasma Physics of Fusion Indirectly Driven with a Laser\, 
 Plasma Physics (Physics/ECE/NE 922) Seminar\, Bob Kirkwood\, Lawrence 
 Livermore National Laboratory
DESCRIPTION:Igniting fusion fuel that is driven indirectly with a lase
 r presents significant challenges for plasma physics because the inten
 se beams required can drive instabilities in the plasma formed in the 
 target.  The instabilities in turn\, can scatter light significantly a
 nd affect power flow and deposition.   The National Ignition Facility 
 (NIF) was constructed to study the physics of inertial fusion and igni
 tion with a laser [1] and has now been in operation for over four year
 s [2].   The design of the facility was based on an understanding of p
 lasma instabilities derived from a series of experiments carried out w
 ith smaller lasers and their modeling.   That work made it clear that 
 the large hot plasmas that would be created when NIFs multiple interse
 cting beams entered a hohlraum target would open a new realm of plasma
  interactions\, where stimulated scattering would not only limit power
  coupling but also provide control of power deposition profiles in the
  target interior [3].   <br>
\n<br>
\nThe initial experiments at NIF [
 4] were also designed based on this understanding which allowed optimi
 zation of laser intensity\, wavelength and spot size\, as well as targ
 et dimensions and materials\, and further indicated the areas of great
 est uncertainty where there was need for final empirical tuning. The r
 ecent studies at NIF have now confirmed for the first time that under 
 ignition relevant conditions plasma instabilities produce self-generat
 ed optical scattering cells that are not only controllable but also us
 eful.   The experiments have further demonstrated that deleterious pla
 sma scatter that depletes power from one set of beams can be compensat
 ed for by inducing a plasma scattering cell that redirects power from 
 another set of beams.  This has allowed induced plasma scattering to b
 ecome the primary means to control the power deposition profile and th
 e resulting implosion symmetry via adjustments to the laser wavelength
 s [5].    These techniques have allowed enhanced target performance th
 at is essential to the present experimental campaigns that study preci
 sion implosions [6]\, and were also an essential ingredient in the rec
 ent demonstration that net energy can be extracted from fusion fuel [7
 ].  This talk will review the plasma physics studied in the first few 
 years of NIC experiments in the context of the earlier work and highli
 ght its importance for fusion ignition with a laser.<br>
\n<br>
\n[1] 
 G. H. Miller\, E. I. Moses\, and C. R. Wuest\, Nucl. Fusion 44\, S228 
 (2004).                                     <br>
\n[2] J. D. Lindl et 
 al Phys. Plasmas 11\, 339 (2004).                                     
                                           <br>
\n[3] R. K. Kirkwood et
  al Plasma Phys. Controlled Fusion 55\, 103001 (2013).                
                     <br>
\n[4] S. H. Glenzer et al Phys. Rev. Lett. 10
 6\, 085004 (2011).                                                    
               <br>
\n[5] P. Michel et al  Phys. Plasmas 17\, 056305 (2
 010).                                                                 
            <br>
\n[6] M. J. Edwards Phys. Plasmas 20\, 070501 (2013). 
                                                                       
     <br>
\n[7] O. A. Hurricane et al Nature 506\, 343 (2014).<br>
\n
URL:https://www.physics.wisc.edu/events/?id=3317
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