onset of coherent electromagnetic structures in the reb …€¦analytical modelling of the laser...
TRANSCRIPT
Onset of Coherent ElectromagneticStructures in the REB-DT fuel
Interaction of fast Ignition Concern
C. Deutsch*, A. Bret**, M-C. Firpo***, L. Gremillet+, E. Lefebvre+ and A. Lifschitz**LPGP, Université Paris-Sud, 91405 Orsay, France
**ETSII, Universitad Castilla-la-Mancha, 13071 Ciudad-Real, Spain***LPTP, Ecole Polytechnique, 91118 Palaiseau, France
+CEN, B3, 91680 Bruyères le Châtel, France
Frontiers Plasma Physics/TechnologyBANGKOK, March 5-7 2007
Complete scheme for the fast ignition with hole boring in the outer layers of the DT precompressed core
Schematic view illustrating the formation of a coaxial beam channel
FILAMENTATION LINEAR ANALYSIS
0Vk b =⋅rr
kc/ωp
Lin
ear
δ/ω
p
Tp = Tb = 100 eVNp/Nb = 10 EReb = 1 MeV
n = 0.0635 n1 = 0.
n = 0.0635 n1 = 0.026
n = 0. n1 = 0.026
n = 0. n1 = 0.
0.4 0.8-0.1
0
0.1
0.2
0.3
0.4
0.5
0.2 0.6 1
(c)
kc/ωp
Qua
si-L
inea
r δ/
ωp
Tp = Tb = 100 eVNp/Nb = 10 EReb = 1 MeV
n = 0.0635 n1 = 0.
n = 0.0635 n1 = 0.026
n = 0. n1 = 0.026
n = 0. n1 = 0.
0 0.2 0.4 0.6 0.8 1
0
0.01
0.02
0.03
0.04
-0.01
(d)
kc/ωp
δ/ωp
Tp = 500 eV Tb = 500 keVNp/Nb = 1000 EReb = 1 MeV
QL
QL
n = 0.0584
n = 0.
L
L
0.0001 0.001 0.01 0.1 1
-0.04
-0.03
-0.02
-0.01
0
0.01
(a)
In summary, we have demonstrated through an efficient analytical modelling of the laser produced REB interacting with outer less dense layers of the supercompressed DT core that the initial in depth propagation phase of the REB within fast ignitor scenario could be effective on a time scale afforded by the linear growth of the electromagnetic instability, provided due account is given to temperature distributions in projectiles and target, respectively.
Those considerations are even more appropriate for nonrelativistic proton beams which might offer the best option for driving fast ignition, provided their laser efficiency could be increased above 20 percent.
♦ Investigation of the growth rates for the Weibel electromagnetic instability (WEI) in FIS conditions for ICF
♦ p
max
ωδ for REB in the MeV energy range
appears manageable in wedged configuration♦ For intense relativistic electron beams, quasi-
linear growth rates remain below linear ones.♦ δ ≤ 0 for protons in the few tens MeV energy
range ♦ Proton fast ignition (PFI) looks highly
promising
Filamentation in FIS conditions for ICF
H. RUHL, Plasma Sources Sci. Technol. 11, A 154 (2002)
Various InstabilitiesTwo-Stream Instability
Filamentation Instability
Weibel Instability
Beam
Beam
Beam
Ek
kE
Ek
Extreme k-orientations
Maxwell + relativistic Vlasov Eqs. (linear)
Collisionless, no finite size effects
FIS conditions : current + return current
Ions form fixed background
Dielectic tensor T (k, ω). Eigenvectors associated with eigenvalue 0 yield angle (k, E)
Dispersion equation( )
( )
( )( ) ( )[ ] 0kkTkTkTkTionFilamentat-Stream-Two
zxxz22
xzz22
zxx2
k//y0 Ek branch Weibel
2yy
2 =−η−−η−η−η
=
4444444 34444444 2143421
c/ ),k ,(k K z, // Beam 2zx ω=η=
PROSPECTIVE
• Fast ignitor conditions seem able to mitigate the growth of the EMITSF instability
• REB stopping compatible with ICF hot spot ignition
• More work needed to unravel the transition of coherent EM structure → Full non linear ones