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Coulomb’05 High intensity beam dynamics September 12 - 16, 2005 – Senigallia (AN), Italy. From long-range interactions to collective behaviour and from hamiltonian chaos to stochastic models Yves Elskens umr6633 CNRS — univ. Provence Marseille. - PowerPoint PPT Presentation
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Senigallia, September 2005 1
From long-range interactions
to collective behaviour
and from hamiltonian chaos
to stochastic modelsYves Elskens
umr6633 CNRS — univ. ProvenceMarseille
Coulomb’05 High intensity beam dynamicsSeptember 12 - 16, 2005 – Senigallia (AN), Italy
http://www.crcpress.com/shopping_cart/products/product_detail.asp?sku=IP464
Senigallia, September 2005 2
• 1. Effective dyn., collective deg. freedom
• 2. Kinetic concepts
• 3. Vlasov
• 4. Limitations, extensions : macroparticle, granularity (N<), entropy production...
• 5. Boltzmann, Landau, Balescu-Lenard
• 6. Quasilinear limit : transport
Senigallia, September 2005 3
1. Long range yields collective degrees of freedom
• Ex. mollified Coulomb (Fourier truncated) : H(q,p) = i
pi2/(2m)
- n i,j kn-2 cos kn.(qi-qj) dt
2 qj = (1/m) n En(qj)
En(x) = - j kn-1 sin kn.(x-qj)
r,n Ar,n(t) sin (kn.x - r,nt)with envelopes A varying slowlyAntoni, Elskens & Sandoz, Phys. Rev. E 57 (1998) 5347
Senigallia, September 2005 4
1 wave and 1 particle
• Integrable system
• Locality in velocity : p-j/kj 2 ~ 4 j Ij1/2
Senigallia, September 2005 5
Beam-plasma paradigm
Underlying plasma electrostatic modes (Langmuir, Bohm-
Gross)
Senigallia, September 2005 6
M waves and N particles
• Effective lagrangian
• Effective hamiltonian H(p, q, I, ) = i pi
2/2 + j j Ij - i,j j Ij1/2 cos (kjqi-j)
coupling type mean field (global), 2 speciesconstants : H, P = i pi + j kj Ij
Senigallia, September 2005 7
Effective hamiltonian
• Dynamical reduction to an effective lagrangian and hamiltonian (“good chaos” vs quasi-constants of motion) N0 >> M + N1 Ex. : N0 particles, Coulomb
M modes (collective, principal) + N1 particles (resonant or test)
Effective dynamics & thermodynamics
Elskens & Escande, Microscopic dynamics of plasmas and chaos (IoP, 2002)
Senigallia, September 2005 8
2. micro- < ... < macroscopic :Kinetic concepts
• Phase space for the dynamics : R6N
Instantaneous state : x = ((q1,p1), ..., (qN,pN))
Probability distribution : f(N)(x,t) dNx Realization : f(N)(y,t) = j=1
N (yj-xj(t))
Evolution (Liouville) : df/dt = -[H,f] tf + j (pj/m).f /qj + j Fj(x).f /pj = 0
Senigallia, September 2005 9
Kinetic concepts
• Observations : space (Boltzmann) R6
Instantaneous state : {(q1,p1), ..., (qN,pN)}Marginal distribution :
f(1)(q1,p1,t) dq1dp1 = .. f(N)(q1,p1,t) j=2
N dqjdp1 ... symmetrized :
f(1s)(q,p,t) = N-1 j f(1)(qj,pj,t)
Senigallia, September 2005 10
Kinetic concepts
• Realization : f(1s)(y,t) = N-1 j=1N (yj-xj(t))
Evolution (BBGKY) : tf(1) + (p/m).qf(1) + F(q,p).pf(1) = 0
with F(q,p) = F[f (N)] = ...
Senigallia, September 2005 11
Kinetic concepts
• Fluid moments : n(q,t) = N f(1s)(q,p,t) dpn u(q,t) = N (p/m) f(1s)(q,p,t) dp...
• Conservation laws by integration and closure
Senigallia, September 2005 12
Kinetic concepts
• Weak coupling : molecular independence approximation
f(N)(q,p,t) j f(1)(qj,pj,t)
... coherent with Liouville ? No !
... supported by dynamical chaos ?
... good approximation ?
Senigallia, September 2005 13
3. Vlasov
• Coupling of mean field type : F1(q,p) = F1[f (N)] = N-1 j=2
N F1j(qj-q1) and for N :
F1(q,p) F1j(q’-q1) f (1s) (q’,p’) dq’dp’ if the force is smooth enough (not pure Coulomb – OK if mollified)then : Vlasov
Spohn, Large scale dynamics of interacting particles (Springer, 1991)
Senigallia, September 2005 14
Vlasov
• Estimates for separation of solutions f(1s)(y,t) - g(1s)(y,t) < f(1s)(y,0) - g(1s)(y,0) et
: majorant for Liapunov exponent in R6N
idea : test particles norm . weak enough for Dirac
Senigallia, September 2005 15
Vlasov
• Ex. : g(1s)(y,0) “smooth” f(1s)(y,0) = N-1 j=1
N (yj-xj(0)) f(1s)(y,0) - g(1s)(y,0) < c N-1/2
• limN limt limt limN
Firpo, Doveil, Elskens, Bertrand, Poleni & Guyomarc'h, Phys. Rev. E 64 (2001) 026407
Senigallia, September 2005 16
4. M waves and N particles
• Effective hamiltonian mean field, 2 species H(p, q, I, ) = i pi
2/2 + j j Ij - i,j j Ij1/2 cos (kjqi-j)
• for M fixed, N : Vlasov
• M=1 : free electron laser, CARL, ...
Senigallia, September 2005 17
4.1. Cold beam instability
Senigallia, September 2005 18
Cold beam instability
Senigallia, September 2005 19
Cold beam instability
Senigallia, September 2005 20
Cold beam instability
Senigallia, September 2005 21
4.2. Instability and damping
Warm beam : L = c df/dv
Senigallia, September 2005 22
Warm beam instability
Senigallia, September 2005 23
Warm beam instability
Senigallia, September 2005 24
Warm beam instability
N2 : Lt = 200
Senigallia, September 2005 25
Warm beam instability
N2 : Lt = 200particles initially in range0.99 < v < 1.00 1.03 < v < 1.04
Senigallia, September 2005 26
Vlasov
• Casimir invariants dt f(1s)(q,p,t) = 0
dt [f(1s)(q,p,t)] dq dp = 0 (if exists) conserve all entropies !
• Trend to equilibrium ? No hamiltonian attractor !... but weak convergence g(q,p) f(1s)(q,p,t) dq dp (for any g)via filamentation
Senigallia, September 2005 27
Warm beam instability
Senigallia, September 2005 28
4.3. Thermalization (M=1) Dynamics : non-linear regimes (trapping)
Canonical ensemble : phase transition
Firpo & Elskens, Phys. Rev. Lett. 84 (2000) 3318
Senigallia, September 2005 29
Thermalization (M>>1)
Y. Elskens & N. Majeri (2005)
Senigallia, September 2005 30
4.4. Chaos & entropy production
• Chaos : Liapunov exponents > 01 = sup limt ln x(t) / x(0) 1+2 = sup limt ln a12(t) /
a12(0) a12(t) = x1(t) x2(t)
...
Senigallia, September 2005 31
Chaos & entropy production
• Hamilton Poincaré-Cartan : dt j=1
3N dpj dqj = 0 symmetric spectrum 6N-j = -j
Liouville : dt j=13N dpjdqj = 0
sum j=16N j = 0
no attractor !
Senigallia, September 2005 32
Chaos & entropy production
• Dynamical complexity : entropy production per time unit
dSmacro/dt < kB hKS ~ kB j j+
Arnold & Avez, Problèmes ergodiques de la mécanique classique (Gauthier-Villars, 1967)Pesin, Russ. Math. Surveys 32 n°4 (1977) 55 Elskens, Physica A 143 (1987) 1Dorfman, An introduction to chaos in nonequilibrium statistical mechanics (Cambridge, 1999)
Senigallia, September 2005 33
5. Kinetic approach : Boltzmann and variations
• Forces with short range (collisions), dilutionBoltzmann Ansatz : tf(1s) + (p/m).qf(1s) + Fext(q,p).pf(1s)
= Q[f(2s)] (BBGKY) Q[f(1s) f(1s)] (non-local in p)
= (f+(1s) f*+(1s) - f(1s) f*(1s)) b(, p*-p) d
dp*
Senigallia, September 2005 34
Boltzmann
• Valid with probability 1 in Grad limit : N , Nr2 = cst
for 0 < t < free/5or for expansion in vacuum...
longer time ? open problem !
Spohn, Large scale dynamics of interacting particles (Springer, 1991)
Senigallia, September 2005 35
Boltzmann
• Entropy :n sBoltzmann(q,t) = - kB f(1s)(q,p,t) ln (f(1s)(q,p,t)/f0)
dp
• H theorem : dsBoltzmann/dt > 0and = iff f(1s) locally maxwellian ; then sBoltzmann[f(1s)] = smicrocan[n,e]
Senigallia, September 2005 36
Boltzmann
• Irreversibility... byproduct of symmetry (microreversibility) of collisions
• H theorem : tool for existence and regularity of solutions
Friedlander & Serre, eds, Handbook of mathematical fluid dynamics (Elsevier, 2001,... )
Senigallia, September 2005 37
Landau, Balescu-Lenard-Guernsey
• Forces with long range and collisionstf(1s) + (p/m).qf(1s) + Fext(q,p).pf(1s)
= - p. U.(p* - p) (f(1s) f*(1s)) dp*
U = (...)dk (Coulomb, Fourier)
Senigallia, September 2005 38
Landau, Balescu-Lenard-Guernsey
• H theorem, maxwellian equilibria• Diagrammatic derivation... “challenge for
the future”
Balescu, Statistical dynamics (Imperial college press, 1997) Spohn, Large scale dynamics of interacting particles (Springer, 1991)
Senigallia, September 2005 39
6. M waves and N particles(weak Langmuir turbulence)
Senigallia, September 2005 40
M waves and N particles
• Effective hamiltonian H(p, q, I, ) = i pi
2/2 + j j Ij - i,j j Ij1/2 cos (kjqi-j)
mean field type coupling, 2 species
constants : H, P = i pi + j kj Ij
Senigallia, September 2005 41
1 wave and 1 particle
• Integrable system
• Locality in velocity : p-j/kj 2 ~ 4 j Ij1/2
Senigallia, September 2005 42
1 particle in 2 waves
• Resonance overlaps = [2(1I1
1/2)1/2+2(2I21/2)1/2] / / 1/k1 - 2/k2
Senigallia, September 2005 43
1 particle in M waves
Bénisti & Escande, Phys. Plasmas 4 (1997) 1576
Senigallia, September 2005 44
Quasilinear limit
• 0 < corr ~ M-1 < t < QL (gas : cf. free) dt q = v dt v = j j kj Ij
1/2 sin (kjq - j) ~ white noise
QL > J-1/3 ln s4/3 (or larger)
• t > box : dynamical independencebox ~ J-1/3
Senigallia, September 2005 45
Stochasticity in parameters dynamical chaos
(1 particle in M waves)
Senigallia, September 2005 46
Stochasticity in parameters dynamical chaos
Senigallia, September 2005 47
Quasilinear limitresonance box (Bénisti & Escande)
Senigallia, September 2005 48
Quasilinear limit : M (s), j random
• Dense wave spectrum vj+1-vj = vj ~ M-1 : “particle diffusion” (Smoluchowski-Fokker-Planck)
t f = v (2 J v f )
• Coupling coefficients (v) = (j/kj) = N j
2/4
• Waves : J(v) = J(j/kj) = kj Ij /(N vj)
Senigallia, September 2005 49
Quasilinear limit : M (s), N
• Dense wave spectrum vj+1-vj = vj ~ M-1 : t f = v Q
• Many particles, poorly coherent : induced and spontaneous emission
t J = Q
• Reciprocity of wave-particle interactions Q = 2 J v f – Fspont f Fspont(v) = - 2 /(N vj)
Senigallia, September 2005 50
Quasilinear limit
• H theorem S = - [f ln (f /f0) + (2)-1 Fspont ln J] dv
• No Casimir invariants for f(v,t)
• Phenomenological equations of markovian type : regeneration of instantaneous stochasticity by “good dynamical chaos”
Senigallia, September 2005 51
Conclusion• Long-range mean field, collective
degrees of freedom + fewer particles
• Smooth Vlasov (+ macroparticle)
• Mean field (e.g. charged particles) simpler than short range (gas) for H-theorem and kinetic eqn
• limN limt limt limN
• N< finite grid
Senigallia, September 2005 52
Senigallia, September 2005 53
Landau damping(non dissipative)
Senigallia, September 2005 54
Landau damping
Senigallia, September 2005 55
Landau damping
Senigallia, September 2005 56
Landau damping Dynamics : non-linear regimes (trapping)
Canonical ensemble : phase transition
Firpo & Elskens, Phys. Rev. Lett. 84 (2000) 3318