Relativistically induced transparency and compressed fusion targets
We study impact of QED effects on relativistically induced transparency in plasma. The relativictic induced transparency is the key phenomenon in the fast igntion schemes for Inertial Confinement Fusion. We have simulated propagation of 100 kJ, 15 fs in a compressed ICF target. The γ quanta generati...
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irk-123456789-1121612017-01-18T03:02:50Z Relativistically induced transparency and compressed fusion targets Pukhov, A.M. Kostyukov, I.Yu. Нелинейные процессы в плазменных средах We study impact of QED effects on relativistically induced transparency in plasma. The relativictic induced transparency is the key phenomenon in the fast igntion schemes for Inertial Confinement Fusion. We have simulated propagation of 100 kJ, 15 fs in a compressed ICF target. The γ quanta generation appears to be the main mechanism of laser energy absorption while the positrons carry less than a percent of the laser energy. The laser pulse propagates 50 μm distance in the dense plasma and an empty channel has been created. Досліджено вплив КЕД-ефектів на релятивістську індуковану прозорість у плазмі. Релятивістська індукована прозорість – ключове явище у різних схемах «швидкого підпалу» для реалізації інерціального термоядерного синтезу. Проведено числове моделювання поширення лазерного імпульсу з енергією 100 кДж та тривалістю 15 фс у скомпресованій лазерній мішені. З результатів моделювання виходить, що генерація гама-квантів є напевно основним механізмом поглинання лазерної енергії. Показано, що лазерний імпульс поширюється 50 мкм у щільній плазмі, створюючи плазмовий канал. Исследовано влияние КЭД-эффектов на релятивистскую индуцированную прозрачность в плазме. Релятивистская индуцированная прозрачность – ключевое явление в различных схемах «быстрого поджига» для реализации инерциального термоядерного синтеза. Проведено численное моделирование распространения лазерного импульса с энергией 100 кДж и длительностью 15 фс в скомпрессированной лазерной мишени. Из результатов моделирования следует, что генерация гамма-квантов является, по-видимому, основным механизмом поглощения лазерной энергии. Показано, что лазерный импульс распространяется 50 мкм в плотной плазме, образуя плазменный канал. 2013 Article Relativistically induced transparency and compressed fusion targets / A.M. Pukhov, I.Yu. Kostyukov// Вопросы атомной науки и техники. — 2013. — № 4. — С. 245-247. — Бібліогр.: 10 назв. — англ. 1562-6016 PACS: 52.65.Rr, 52.38.Ph http://dspace.nbuv.gov.ua/handle/123456789/112161 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Нелинейные процессы в плазменных средах Нелинейные процессы в плазменных средах |
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Нелинейные процессы в плазменных средах Нелинейные процессы в плазменных средах Pukhov, A.M. Kostyukov, I.Yu. Relativistically induced transparency and compressed fusion targets Вопросы атомной науки и техники |
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We study impact of QED effects on relativistically induced transparency in plasma. The relativictic induced transparency is the key phenomenon in the fast igntion schemes for Inertial Confinement Fusion. We have simulated propagation of 100 kJ, 15 fs in a compressed ICF target. The γ quanta generation appears to be the main mechanism of laser energy absorption while the positrons carry less than a percent of the laser energy. The laser pulse propagates 50 μm distance in the dense plasma and an empty channel has been created. |
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Article |
| author |
Pukhov, A.M. Kostyukov, I.Yu. |
| author_facet |
Pukhov, A.M. Kostyukov, I.Yu. |
| author_sort |
Pukhov, A.M. |
| title |
Relativistically induced transparency and compressed fusion targets |
| title_short |
Relativistically induced transparency and compressed fusion targets |
| title_full |
Relativistically induced transparency and compressed fusion targets |
| title_fullStr |
Relativistically induced transparency and compressed fusion targets |
| title_full_unstemmed |
Relativistically induced transparency and compressed fusion targets |
| title_sort |
relativistically induced transparency and compressed fusion targets |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2013 |
| topic_facet |
Нелинейные процессы в плазменных средах |
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http://dspace.nbuv.gov.ua/handle/123456789/112161 |
| citation_txt |
Relativistically induced transparency and compressed fusion targets / A.M. Pukhov, I.Yu. Kostyukov// Вопросы атомной науки и техники. — 2013. — № 4. — С. 245-247. — Бібліогр.: 10 назв. — англ. |
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Вопросы атомной науки и техники |
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2025-07-08T03:28:55Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2013. №4(86) 245
RELATIVISTICALLY INDUCED TRANSPARENCY
AND COMPRESSED FUSION TARGETS
A.M. Pukhov1,3, I.Yu. Kostyukov2,3
1Unviersity of Dusseldorf, Dusseldorf, Germany;
2Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia;
3Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia
E-mail: pukhov@tp1.uni-duesseldorf.de
We study impact of QED effects on relativistically induced transparency in plasma. The relativictic induced
transparency is the key phenomenon in the fast igntion schemes for Inertial Confinement Fusion. We have simulated
propagation of 100 kJ, 15 fs in a compressed ICF target. The γ quanta generation appears to be the main mechanism
of laser energy absorption while the positrons carry less than a percent of the laser energy. The laser pulse
propagates 50 μ m distance in the dense plasma and an empty channel has been created.
PACS: 52.65.Rr, 52.38.Ph
The laser technology has experienced a tremendous
development over the last decades. The ever higher
laser peak powers and focused intensities have been
achieved that revolutionized science. The revolution
begann in 1985 with the invention of CPA (Chirped
Pulse Amplification) Today, it is the workhorse of most
laser amplification systems. Later, the OPCPA (Optical
Parametric Chirped Pulse Amplification) has been
introduced. Being based on CPA, it employs nonlinear
crystals to transfer energy from a long pump pulse to the
seed. It is now used for broadband, few cycles pulse
amplification. Finally, about 15 years ago, a new
compression technique based on Backwards Raman
Scattering (BRA) and Backwards Compton Scattering
Amplification (BCSA) were proposed. These two do not
require expensive gratings, and thus eliminate the major
hurdle in ultrahigh high peak power pulse amplification.
The laser pulse can be amplified in plasma − a medium
that can survive extremely high intensities. Extremely
high energy fluencies can be achieved, many orders of
magnitude above the limitation set up by solid density
gratings. This opens the path beyond the exawatt,
towards the zettawatt in the laser power.
The C3 (Cascaded Conversion Compression)
concept has been recently put forward within the
European iZEST project (International Center for
Zettawatt-Exawatt Science and Technology) that targets
possible efficient compression of 10 kJ to MJ, ns pulses
delivered by NIF or LMJ-like laser, into fs pulses of the
highest quality. This technique employs CPA to produce
a first-stage compression, followed by BRA for a
second-stage compression, together with OPCPA to
produce a strong seed pulse. The combination of the
three is optimized over the joint compression
technologies of both compression stages.
If successfull, the C3 technology will result in ultimate
laser power and intensity. Assuming, we succeed
compressing 100 kJ energy in a focal spot of σ = 10 μm
and pulse duration of 10=τ fs, the peak intensity would
be as high as 24
0 103= ⋅I W/cm2. If the laser pulse has
the wavelength of μλ 1= m, the normalized laser
amplitude 00 /= ωmceEa would be 1000>0a . Because
of the huge amplitude, any solid state material would
become transparent to these ultra-intense laser pulses.
Plasmas with densities above the critical one
2
2
0
4
=
e
mnc π
ω (1)
are opaque for linear elecromagnetic waves with the
frequency 0ω . However, when the plasma particles
become relativistic and acquire large relativistic γ-
factor, the critical density must be renormalized:
2
2
0
4
=
e
mnrel
c π
ωγ . (2)
Due to the relativistic mass correction of the
electrons, the ultra-intense laser pulse can propagate
much deeper into the dense material.
According to the similarity theory [7], the relativistic
laser-plasma interaction is governed by the main
similarity parameter
cna
nS
0
= . (3)
The −S number can be roughly interpreted as a
relativistically corrected critical density ratio. Yet, it
does not mean that media with 1>S are always opaque
and media with 1<S are always transparent. The
particular interaction depends also on other details like
the laser polarization, focal spot radius, density gradient,
etc. However, the similarity theory claims that if a
plasma with the density 0n is transparent for a laser
with 1>0a , then a plasma with the density 1n will be
transparent for a laser pulse with the amplitude
0101 /= nnaa . In this sense, the 1≈S indeed marks the
boundary of relativistic transparency.
One of the potential applications for the
relativistically induced transparency mught be the fast
igntion in ICF (Inertial Confinement Fusion). The
original fast ignition scheme [8] suggests two laser
pulses. The first laser pulse should drill a channel
through overdense plasma corona and was intended to
be some 100 ps long. The second shorter and intenser
pulse, the igniting one, would propagate through the
preform channel and deliver enough energy to the
compressed target core for the ignition. However, it is
unclear whether the channel boring can be completed by
a low intensity long laser pulse as the plasma
surrounding the channel is heated continously by the
same laser pulse and at some point the kinetic plasma
pressure may overcome the light pressure of the drilling
laser. This would stop the channel boring.
ISSN 1562-6016. ВАНТ. 2013. №4(86) 246
If one succeeds compressing an ICF laser into 10 fs
and focus it down to the amplitude a0 > 1000, the
compressed ICF target may become relativistically
transparent very close to the core. Such a laser pulse
would propagate through the corona shoveling the
plasma aside and open an empty channel, in which a
lower intensity ignition laser pulse can freely propagate.
In this work, we try to simulate this scenario using the
full three dimensional code VLPL (Virtual Laser
Plasma Laboratory) [9].
Fig. 1. Laser pulse at 70 μ m before the center of the
compressed target. (a) Normalized laser intensity
( ) ( )20
2
0 //= ωω mceBmceEI + ; (b) plasma density in
critical densities cnn/ ; (c) normalized energy density
of γ-quanta 2/= mcnWn cγ
; (d) normalized density
of positrons np/nc
At the laser intensities 2410=I W/cm2 and above,
QED (quantum electrodynamics) effects must be taken
into account. The emission of γ-quanta and the
correspoding momentum recoil must be incorporated
into the electron equation of motion. Also, the
electromagnetic fields are so huge that the γ-quanta start
producing abundand electron-positron pairs. All these
effects were introduced into the VLPL code. In our
simulations, we took a compressed ICF target consisting
of pure deuterium with the density profile
( )22
0 /exp=)( σrnrn − with 25
0 10=n cm-3 and σ = 30 μm.
The laser pulse was a circularly polarized Gaussian one
with the envelope ( ) ( )2222
0 /exp/exp=),( τσρ ρ tatra −− with
the peak amplitude a0 = 2000, the focal spot radius
σρ = 5 μm and the pulse duration 14=τ fs. The laser
was focused to converge exactly at the center of the
target. The first laser pulse harmonic at the wavelength
of λ = 1 μm was assumed. In this configuration, the
similarity parameter at the target center is 5=S .
Fig. 1 shows the simulation results when the laser
pulse is about 70 μm away from the target center. We
see a shock wave formed at the sharp laser-plasma
interface. Abundand production of γ-photons and
positrons begins at this point. The energy density of the
γ-quanta becomes comparable with the laser energy
density and the peak positron density is higher than
1023 cm-3 here that is above the solid density.
Finally, the laser pulse stops some 50 μm before the
geometrical center of the compressed core as is shown
in Fig. 2. The background plasma density here was
about n ≈ 6⋅1023cm-3. About 40% of the laser energy has
been converted into energetic particles at this point.
Fig. 2. Laser pulse is completely absorbed at about
50 μm before the geometrical center of the compressed
target. (a) Normalized laser intensity
( ) ( )20
2
0 //= ωω mceBmceEI + ; (b) plasma density in critical
densities cnn/ ; (c) normalized energy density
of γ-quanta 2/= mcnWn cγ ; (d) normalized density
of positrons np/nc
Fig. 3 shows the energy spectra. Apparently, the
deuterons acquire the highest energies per particle via
the relativistic shock wave acceleration [10]. The laser
energy has been deposited into different particles as
shown in Fig. 4. Surprizingly, most of the laser energy
has been spent to generate radiation. About 60% has
been converted into γ-quanta. Some 35% percent remain
in deuterons, and only 5% carry the electrons. Less than
1% of the laser energy is converted into positrons. It is
the radiation damping that prevented electrons from
acquiring too much energy. As soon as the electrons
became energetic enough, they radiated their energy
away. Thus, plasma at these extreme intensities is an
efficient convertor of laser energy into hard
electromagnetic radiation.
In conclusion, we have simulated relativistic
transparency of a compressed ICF target irradiated by a
100 kJ, 15 fs laser pulse of amplitude а0 = 2000. We
have shown that laser-plasma interaction at these
intensities is dominated by QED effects. Our PIC
simulations have included generation of γ-quanta and
electron-positron pairs in the strong laser fields. The γ-
quanta generation appears to be the main mechanism of
laser energy absorption. We also observe dense bunches
of positrons. Yet, the positrons carry less than a percent
of the laser energy.
a
b
b
a
c
c
d
d
ISSN 1562-6016. ВАНТ. 2013. №4(86) 247
Fig. 3. Energy spectra of particles
Fig. 4. Percentage of energy deposited into particles
of different species
The laser was able to propagate up to 50 μm
distance from the target geometric center. An empty
channel has been created up to the plasma density of
about 6⋅1023cm-3. This channel can be used to send an
igniting beam of lower intensity to the compressed core.
ACKNOWLEDGEMENTS
This work has been supported by the Government of
the Russian Federation (Project № 14.B25.31.0008), by
Russian Fond for Basic Research, by the Ministry of
Science and Education of the Russian Federation, the
Russian Federal Program «Scientific and scientific-
pedagogical personnel of innovative Russia» and by
DFG TR18 project.
REFERENCES
1. D. Strickland and G. Mourou. Compression of
amplified chirped optical pulses // Optics
Communications. 1985, v. 56(3), p. 219-221.
2. I.N. Ross et al. The prospects for ultrashort pulse
duration and ultrahigh intensity using optical
parametric chirped pulse amplifiers // Opt. Commun.
1997, v. 144, p. 125.
3. V.M. Malkin, G. Shvets, and N.J. Fisch. Fast
Compression of Laser Beams to Highly Overcritical
Powers // Physical Review Letters. 1999, v. 82,
p. 4448-4451.
4. G. Shvets, N.J. Fisch, A. Pukhov, J. Meyer-ter-
Vehn. Superradiant amplification of an ultrashort
laser pulse in a plasma by a counterpropagating
pump // Physical Review Letters. 1998, v. 81 (22),
p. 4879-4882.
5. G.A. Mourou et al. Exawatt-Zettawatt pulse
generation and applications // Optics Communications
285, iss. 5, 1 March 2012, p. 720-724.
6. http://www.izest.polytechnique.edu/
7. S. Gordienko, A. Pukhov. Scalings for
ultrarelativistic laser plasmas and
quasimonoenergetic electrons // Physics of Plasmas.
2005, v. 12, p. 043109.
8. M. Tabak et al. Ignition and high gain with ultrapowerful
lasers // Phys. Plasmas. 1994, v. 1, p. 1626.
9. A. Pukhov. Three-dimensional electromagnetic
relativistic particle-in-cell code VLPL (Virtual Laser
Plasma Lab) // Journal of Plasma Physics. 1999,
v. 61(3), p. 425-433.
10. L. Ji, A. Pukhov, B. Shen. Ion acceleration in
dragging field of a light-pressure-driven piston //
arXiv:1302.4611v1 (2013).
Article received 10.04.2013.
РЕЛЯТИВИСТСКАЯ ИНДУЦИРОВАННАЯ ПРОЗРАЧНОСТЬ И ОБЖАТИЕ ЛАЗЕРНОЙ
МИШЕНИ ДЛЯ ИТС
А.М. Пухов, И.Ю. Костюков
Исследовано влияние КЭД-эффектов на релятивистскую индуцированную прозрачность в плазме. Реля-
тивистская индуцированная прозрачность – ключевое явление в различных схемах «быстрого поджига» для
реализации инерциального термоядерного синтеза. Проведено численное моделирование распространения
лазерного импульса с энергией 100 кДж и длительностью 15 фс в скомпрессированной лазерной мишени. Из
результатов моделирования следует, что генерация гамма-квантов является, по-видимому, основным
механизмом поглощения лазерной энергии. Показано, что лазерный импульс распространяется 50 мкм в
плотной плазме, образуя плазменный канал.
РЕЛЯТИВІСТСЬКА ІНДУКОВАНА ПРОЗОРІСТЬ ТА СТИСКАННЯ ЛАЗЕРНОЇ МІШЕНІ ДЛЯ ІТС
А.М. Пухов , І.Ю. Костюков
Досліджено вплив КЕД-ефектів на релятивістську індуковану прозорість у плазмі. Релятивістська інду-
кована прозорість – ключове явище у різних схемах «швидкого підпалу» для реалізації інерціального термо-
ядерного синтезу. Проведено числове моделювання поширення лазерного імпульсу з енергією 100 кДж та
тривалістю 15 фс у скомпресованій лазерній мішені. З результатів моделювання виходить, що генерація
гама-квантів є напевно основним механізмом поглинання лазерної енергії. Показано, що лазерний імпульс
поширюється 50 мкм у щільній плазмі, створюючи плазмовий канал.
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