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Robust Heavy Ion Fusion Target

Robust Heavy Ion Fusion Target. Shigeo KAWATA Utsunomiya Univ. Japan U.S.-J. Workshop on HIF December 18-19, 2008 at LBNL & LLNL. Acknowledgments Thanks for Collaborations with Grant, John & Friends in VNL for WDM/HEDM physics + HIF with wobblers! Colleagues in HIF Japan, Sasho, Jacob

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Robust Heavy Ion Fusion Target

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  1. Robust Heavy Ion Fusion Target Shigeo KAWATA Utsunomiya Univ. Japan U.S.-J. Workshop on HIF December 18-19, 2008 at LBNL & LLNL

  2. Acknowledgments Thanks for Collaborations with Grant, John & Friends in VNL for WDM/HEDM physics + HIF with wobblers! Colleagues in HIF Japan, Sasho, Jacob JSPS & MEXT, Japan

  3. / High hd ~ 30~40% / Robust driver with a high rep. / Beam handling / Spherical target with a hybrid implosion / Robust implosion

  4. 80 Without foam in 25.2nsec 60 With foam in 25.1nsec ] 3 r[g/cm 40 20 0 1.5 2.5 3.5 4.5 5.5 r [mm] Advantages of HIF Scheme / High efficiency ~30~40% => Gain~30 with ~10Hz operation / Simple energy deposition / Robust against R-T instability <= large density gradient Large scale Small scale

  5. No 11 80 Without foam in 25.2nsec 60 With foam in 25.1nsec ] 3 r[g/cm 40 20 0 1.5 2.5 3.5 4.5 5.5 r [mm] The Density Valley is Widened by inserting the foam. Without foam Incident beam : 34 [ns] 7 [MJ] Nonunifomity : 2.0 [%] Maximum incidence angle : 30 [degree] With foam Incident beam : 34 [ns] 7 [MJ] Nonunifomity : 4.0 [%] Maximum incidence angle : 40 [degree] Comparison of space profiles of density

  6. No 20 2.5 8 Growth Rate g [1/nsec] 7 gt 2 6 5 1.5 Growth Rate g [1/nsec] gt 4 1 3 2 0.5 1 0 0 0 5 10 15 20 25 30 35 Time [nsec] Estimation of the R-T Instability growth With foam Incident beam : 34 [ns] 7 [MJ] Maximum incidence angle : 40 [degree] Histories of growth rate of the R-T instability with foam

  7. 7 Introduction - Problems of ICF - Flow of inertial confinement fusion Wobbling HIBs => time-dependent energy deposition dE => time-dependent non-uniform acceleration: dg

  8. 8 The Rayleigh-Taylor Instability (RTI) 2π/k 2π/k ρ1<ρ2 gravity high density low density • When a low density fluid supports a high density one under gravity, the fluid instability is caused. • This instability is so called the Rayleigh-Taylor Instability (RTI). • The growth rate of the RTI is

  9. 9 RTI induced by non-uniform gravity ion beam target A non-uniform acceleration (gravity) is generated by non-uniform illumination of heavy ion beams. Because the beam number is finite. The gravity is expressed by the constant term and the non-uniform term, in this study.

  10. 10 RTI induced by non-uniform gravity time

  11. density gravity 10.0 5.0 0.0 The calculation parameters are Simulation model - constant gravity - gravity ρ

  12. 1.0 ρ 10 y [2π] 3 0.0 1.0 0.0 x [2π] 12 Simulation result - constant gravity - density t=0~6 [1/γ] gravity • The RTI is grown by the initial unstable density and the non-uniform gravity distributions.

  13. Oscillation Gravity gravity x 13 HIB axis can be oscillated with a high frequency-> Control of RTI - Oscillating gravity - From the equation, when the gravity oscillation frequency f increases, the RTI perturbation velocity w decreases.

  14. Oscillation Gravity gravity x 14 Control of RTI - Oscillating gravity - The RTI perturbation velocity is approximately written by <-. From the equation, when the gravity oscillation frequency f is increased, the RTI perturbation velocity w decreases.

  15. Single Mode Simulation [constant gravity] 1.0 1.0 y [2π] y [2π] 0.0 0.0 1.0 1.0 0.0 0.0 x [2π] x [2π] t=0~6 [1/γ] density vorticity

  16. Single Mode Simulation [constant gravity] t=5 [1/γ] density vorticity

  17. Single Mode Simulation [oscillation gravity] gravity density 1.1 gravity 1.0 gravity 0.9 1.0 0.0 0.5 x [2π] parameter

  18. Single Mode Simulation oscillation (γ[Hz]) density t=5 [1/γ] t=7 [1/γ] t=9 [1/γ] vorticity

  19. Single Mode Comparison (γt=5) density vorticity constant oscillation (γ[Hz])

  20. Single Mode Comparison(passage of time) constant constant f=1[γ] f=1[γ] f=10[γ] f=10[γ] constant f=1[γ] f=10[γ]

  21. Multi Mode Simulation [oscillation gravity] 1.1 gravity 1.0 0.9 0.5 1.0 0.0 x [2π] gravity gravity parameter

  22. Multi Mode Comparison (t=5 [1/γ]) density vorticity constant oscillation (γ[Hz])

  23. Al 1.00mm 2.69g/cm3 Illumination of Wobblers Parameters Pb+ ion beam Beam number : 12, 32 Beam particle energy : 8GeV Beam particle density distribution : Gaussian Beam temperature of projectile ions : 100MeV with the Maxwell distribution Beam emittance : 1.0 mm-mrad External pellet radius : 4.0mm Pellet material : Al Al pellet structure

  24. Rotation radius 1.5mm Rotation radius 2.0mm Rotation radius 3.0mm Beam radius 1.5~4.0mm Pellet radius 4.0mm Rotation radius 1.5~3.0mm

  25. Rotation radius 1.9mm Beam radius 2.6mm 2.3 % Rotation radius 3.0mm Beam radius 3.2mm 3.2 %

  26. 12-beam 12 beams Rotation radius 1.9mm Beam radius 2.6mm 8.29% 12-HIBs illumination system mm 32-beam 32 beams Rotation radius 1.9mm Beam radius 2.6mm 2.32% 32-HIBs illumination system mm

  27. Mode(1,0) Mode(1,1) Mode(2,2) Mode(2,0) Mode(2,1)

  28. 28 Summary • The Rayleigh-Taylor Instability growth can be reduced by the oscillating gravity (acceleration), that may be realized by wobbling HIBs. • The reduction ratio of the RTI growth depends on the frequency of the gravity oscillation. • Even in the case of the multi mode gravity perturbation, the RTI growth is reduced by the wobbler.

  29. Wobblers may bring a robust uniform target implosion.

  30. Proposal of a Conceptual Design of International HIF Reactor?!? International Collaborative Work! i-HIF Reactor chamber Ion Beam Accelerator target Issues in HIF / Particle Accelerator (Scale, Cost, Energy, etc..) / Physics of Intense Beam (Focusing & Compression, Emittance growth, etc..) / Beam Final Transport (Stable transportation, Interaction with gas, etc..) / Target-Plasma Hydrodynamics, stability, beam illumination scheme, robustness, ignition, burning, … / Reactor design, wall, T breeding, molten salt, material, neutronics, … etc..

  31. Forward focal position Backward focal position Rbeam Fuel pellet Focal Spot Ren advr Rf fmax fmin Rch f Previous work on uniform HIB illumination Pellet injector HIB illumination non-uniformity < a few % Reactor chamber center Displacement dz [J/mm3] Fuel Pellet 2.36×105 Fusion reactor 1.84×105 1.33×105 IFE reactor 8.14×104 3.00×104 (a)dz = 0[mm] (b)dz = 100[mm] Conventional illumination pattern => ~ 50-100mm => non-uniformity > 3.0% Our results => ~ 300-400mm is allowable

  32. Sample (beam profile) Simulation [constant] gravity 1.1e+11 1.0e+11 gravity [m/s2] 0.9e+11 0.9 0.0 0.3 0.6 x [mm] gravity parameter beam profilePn

  33. Sample (beam profile) Comparison (t=0.2 [μsec]) density vorticity constant oscillation (γ[Hz])

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