I3_015_Pukhov.ppt
21
Generation of particle beams Generation of particle beams and X-rays and X-rays in ultra-relativistic laser- in ultra-relativistic laser- plasmas plasmas . . A. Pukhov 1 , S. Gordienko 1,2 , T. Baeva 1 , O.Shorokhov 1 , S. Kiselev 1 1 Institut für Theoretische Physik Universität Düsseldorf 2 L.D.Landau Institute for Theoretical Physics, Moscow
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Transcript of I3_015_Pukhov.ppt
Generation of particle beams Generation of particle beams and X-rays and X-rays
in ultra-relativistic laser-in ultra-relativistic laser-plasmasplasmas..
A. Pukhov1, S. Gordienko1,2, T. Baeva1, O.Shorokhov1, S. Kiselev1
1Institut für Theoretische PhysikUniversität Düsseldorf
2L.D.Landau Institute for Theoretical Physics, Moscow
04/10/23 [email protected]
OutlineOutline Ultra-relativistic similarity theoryUltra-relativistic similarity theory
Origin of the “ponderomotive” scalingsOrigin of the “ponderomotive” scalingsfor electron “temperatures”for electron “temperatures”
Experimental observation of Weibel Experimental observation of Weibel instabilityinstability
High harmonics from plasma surfaces: High harmonics from plasma surfaces: the universal power-law spectra up to the universal power-law spectra up to X-raysX-raysand coherent focusingand coherent focusing
04/10/23 [email protected]
SSSimilarity for Ultra-Relativistic Similarity for Ultra-Relativistic Plasmas, Plasmas,
II2210101818 W Wmm22/cm/cm22
The similarity parameter (S-number)
Valid for the Vlasov-Maxwell electron dynamics, a021 :
Gordienko, Pukhov Phys. Plasmas 12, 043109 (2005)
04/10/23 [email protected]
The similarity parameter (S-number)
Dynamics of plasmas with S=const is similar. Electrons move along the same trajectories, their momenta scale as
Gordienko, Pukhov Phys. Plasmas 12, 043109 (2005)
SSSimilarity for Ultra-Relativistic Similarity for Ultra-Relativistic Plasmas, Plasmas,
II2210101818 W Wmm22/cm/cm22
The S-number has the role of relativistically corrected plasma density.It separates relativistically overdense plasmas, S>>1,
from relativistically underdense ones, S<<1.
04/10/23 [email protected]
Scalability of laser-plasmas, Scalability of laser-plasmas, SS=const=const
If we know one interaction regime with a0 and n0, then it can be scaled so that
The energy of hot electrons scales as
The number of hot electrons scales as
The laser power scales as
04/10/23 [email protected]
Similarity in Fast Ignition Similarity in Fast Ignition context:context:
“ponderomotive “ponderomotive temperatures”temperatures”
1018 1019 1020 1021
1
10
100
Teff = I1/2
Tef
f , M
eV
Intensity, W/cm2
Ne /
MeV
Energy, MeV
0.0 100.0 200.0 300.0 400.0 500.0104
106
108
1010
1012
1 TW, 1018 W/cm2
100 TW1020 W/cm2
1000 TW1021 W/cm2
50 MeV
14 MeV
0.8 MeV
10 TW, 1019 W/cm2
4.5 MeV
Pukhov, Meyer-ter-Vehn, Sheng, Phys. Plasmas, 1999
Electron energies scale as I1/2 ~ a.Electron numbers scale as I1/2 ~ a.
Why these scalings?Interaction regime is quite complex and clearly non-ponderomotive
04/10/23 [email protected]
““Ponderomotive temperatures”Ponderomotive temperatures”in exponential preplasmasin exponential preplasmas
X
ne = nc exp(x/L)
L=30m
Laser
e-
Interaction is automatically self-similar, because laser pulses are always reflectedat the relativistic critical density, S ~ 1.
“Ponderomotive” scalings are in fact similarity scalings!
04/10/23 [email protected]
The RAL ExperimentThe RAL Experiment
VULCAN Laser Energy – 350 Jduration – 750 fs
R. Jung, et al. Phys. Rev. Lett. 94, 195001 (2005)
04/10/23 [email protected]
The RAL Experiment:The RAL Experiment: Electron SpectraElectron Spectra
PIC simulation“cold”
“hot”
R. Jung, et al. Phys. Rev. Lett. 94, 195001 (2005)
04/10/23 [email protected]
Experimental observation Experimental observation of the Weibel Instabilityof the Weibel Instability
Second harmonic emission from rear surface of 250 µm foam target.
Two concentric circles of filaments
R. Jung, J. Osterholz, K. Lowenbruck, S. Kiselev, G. Pretzler, A. Pukhov, O. Willi, S. Kar, M. Borghesi, W. Nazarov, S. Karsch, R. Clarke, D. Neely Phys. Rev. Lett. 94, 195001 (2005)
Laser: 350 J, 750 fs
04/10/23 [email protected]
Nonlinear Weibel Nonlinear Weibel InstabilityInstability
2D PIC simulations by Honda et al., Phys. Rev. Lett. (2000).
04/10/23 [email protected]
Filamentation, Filamentation, 3D PIC Simulation3D PIC Simulation
(▲) Transverse cuts of electron density
(+) The x-component of the quasi-static magnetic field.
10µm
20µm
100µm
(+)
(+)
(+)
(▲)
(▲)
(▲)
Two rings of filaments
04/10/23 [email protected]
Harmonics from plasma surfaces:Harmonics from plasma surfaces:the analytical theorythe analytical theory
S.Gordienko, A.Pukhov, O.Shorokhov, T.Baeva, Phys. Rev. Lett. 93, 115002 (2004).
Relativistically oscillatingapparent reflection point
E(X(t))=0.
X(t), (t)
Ion
boun
dary
The reflected pulse contains high harmonics
S.Gordienko, A.Pukhov, O.Shorokhov, T.Baeva, Phys. Rev. Lett. 94, 103903 (2004).
04/10/23 [email protected]
Analytical Form of the Universal Analytical Form of the Universal SpectrumSpectrum
log I n
log n
In n-2.5
n=42
ncutoff=83
Similarity theory states that a if S = const.
S.Gordienko, A.Pukhov, O.Shorokhov, T.Baeva, Phys. Rev. Lett. 94, 103903 (2004).
04/10/23 [email protected]
Reflected radiation spectra in 1D PIC Reflected radiation spectra in 1D PIC simulations simulations
1 10 100 1000 n/0
-2.5a0=20a0=10a0=5
102
104
106
108
1010
1012
Inte
nsit
y, a
.u.
The Gaussian laser pulse a=a0exp[-(t/)2]cost is incident onto an overdense plasma layer with n=30nc, .The color lines correspond to laser amplitudes a0=5,10,20.The broken line marks the analytical scaling -2.5.
S.Gordienko, A.Pukhov, O.Shorokhov, T.Baeva, Phys. Rev. Lett. 93, 115002 (2004).
04/10/23 [email protected]
Temporal profile of the reflected Temporal profile of the reflected radiationradiation
t / 2
Ref
lect
ed s
igna
l int
ensi
ty, a
.u. Unfiltered signal: train of
attosecond pulses
Harmonics with n<300 filtered out: train of zeptosecond pulses
the 300-zeptosecond pulse zoomed
S.Gordienko, A.Pukhov, O.Shorokhov, T.Baeva, Phys. Rev. Lett. 93, 115002 (2004).
04/10/23 [email protected]
Characteristics of the plasma Characteristics of the plasma harmonicsharmonics
1. The spectrum is the universal slow-decaying power law I ~ -2.5.
2. The cut-off frequency scales fast with the plasma -factor: c / 0 = 83
max
3. The shortest pulse duration scales as ~1/c=1/83
max
4. The harmonics are coherent and phase-locked
04/10/23 [email protected]
Coherent Harmonics Coherent Harmonics Focusing Focusing
S.Gordienko, A.Pukhov, O.Shorokhov, T.Baeva, Phys. Rev. Lett. 94, 103903 (2004).
Because all the harmonics are phase locked, their fields in the focus interfere constructively leading to an enormous intensity boost
04/10/23 [email protected]
3D PIC Simulation of CHF 3D PIC Simulation of CHF
Linear focusing
CHFLaser pulse with a0=3 is reflected from a concave plasma surface with n/nc=5, focal distance R0=4.
04/10/23 [email protected]
The CHF Intensity Scaling The CHF Intensity Scaling from 1D PIC Simulationsfrom 1D PIC Simulations
IQED
I CH
F, W
/cm
2
I0, W/cm2
04/10/23 [email protected]
SummarySummary
Ultra-relativistic laser-plasmas are characterized by the similarity number S = ne / anc
Spectra with “ponderomotive temperatures” are in fact due to the Ssimilarity scalings
Weibel instability has been observed experimentally
Harmonics from plasma surfaces are phase-locked, coherent and have universal power-law spectra
The Coherent Harmonics Focusing may boost the intensity above the vacuum breakdown threshold
