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![(Color online) Two sources of electron radiation in the plasma layer at t = 9.2T 0. (a) Radiation field of the electron sheets [blue (dark gray) line, increased by 90 times for better visibility], radiation of the same sheets calculated for β x = 0 [magenta (medium gray) line, also increased by 90 times], electron density [cyan (light gray) line], vector potential of the standing wave (black line), and electric field of the right-going wave (dashed red line). (b) Phase spaces x − β x [blue (dark gray) line] and x − β y [cyan (light gray) line] for the electrons of the layer. The electrons, which form two radiation sources, are enclosed with ellipses. The parameters of the interaction are the same as in Fig. 1.](profile/Min-Sup-Hur/publication/232714158/figure/fig6/AS:667201984012292@1536084757563/Color-online-Two-sources-of-electron-radiation-in-the-plasma-layer-at-t-92T-0-a.jpg)
(Color online) Two sources of electron radiation in the plasma layer at t = 9.2T 0. (a) Radiation field of the electron sheets [blue (dark gray) line, increased by 90 times for better visibility], radiation of the same sheets calculated for β x = 0 [magenta (medium gray) line, also increased by 90 times], electron density [cyan (light gray) line], vector potential of the standing wave (black line), and electric field of the right-going wave (dashed red line). (b) Phase spaces x − β x [blue (dark gray) line] and x − β y [cyan (light gray) line] for the electrons of the layer. The electrons, which form two radiation sources, are enclosed with ellipses. The parameters of the interaction are the same as in Fig. 1.
Source publication
Generation of petawatt-class pulses with a nearly single-cycle duration or with a strongly asymmetric longitudinal profile using a thin plasma layer are investigated via particle-in-cell simulations and the analytical flying mirror model. It is shown that the transmitted pulses having a duration as short as about 4 fs (1.2 laser cycles) or one-cycl...
Contexts in source publication
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... (here and below the momenta are normalized with mc). Note that for an electron, which is free and motionless before interaction with an electromagnetic wave, during interaction, transverse and longitudinal momenta tend to zero simultaneously, and there is no increase for the longitudinal velocity at that times. This effect is clearly seen in Fig. 8(b), where the phase spaces x − β x and x − β y for the electrons are presented. The electrons enclosed with a red ellipse near x ≈ 15.3 have small transverse velocities β y and ultrarelativistic longitudinal velocities β x , which are greater than 0.999 for some of ...
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... opposite directions along x will be considerably greater than the radiation of two motionless sheets. Since for β ⊥ = 0 the radiation field is equal to zero, the peaks of the radiation field will be positioned near these points, where β ⊥ ≈ 0 and β x 1. The radiation field of the electrons at t = 9.2T 0 (just before transmission) is presented in Fig. 8(a) [(blue (dark gray) line, increased by 90 times for better visibility] and in Fig. 5 [green (dark gray) line, increased by 15 times]. The radiation of the electron sheets supposing they are motionless along x is also presented in Fig. 8(a) [magenta (medium gray) line, also increased by 90 times]. These radiations were calculated by ...
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... ≈ 0 and β x 1. The radiation field of the electrons at t = 9.2T 0 (just before transmission) is presented in Fig. 8(a) [(blue (dark gray) line, increased by 90 times for better visibility] and in Fig. 5 [green (dark gray) line, increased by 15 times]. The radiation of the electron sheets supposing they are motionless along x is also presented in Fig. 8(a) [magenta (medium gray) line, also increased by 90 times]. These radiations were calculated by summation of radiation fields of all electron sheets in some cell obtained from Eq. (1) (note that this is the instant radiation and it does not equal the total radiation of the plasma layer at t = 9.2T 0 ). From Fig. 8(a), one can conclude ...
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... along x is also presented in Fig. 8(a) [magenta (medium gray) line, also increased by 90 times]. These radiations were calculated by summation of radiation fields of all electron sheets in some cell obtained from Eq. (1) (note that this is the instant radiation and it does not equal the total radiation of the plasma layer at t = 9.2T 0 ). From Fig. 8(a), one can conclude that, generally, there are two sources producing high-amplitude radiation. One source of radiation is formed in the region, where the electron density is maximal [radiation of the electrons from x 15.7 to x 16 in Fig. 8, also marked with the red ellipse in Fig. 8(b)]. This source is motionless along x (or moves slowly ...
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... the instant radiation and it does not equal the total radiation of the plasma layer at t = 9.2T 0 ). From Fig. 8(a), one can conclude that, generally, there are two sources producing high-amplitude radiation. One source of radiation is formed in the region, where the electron density is maximal [radiation of the electrons from x 15.7 to x 16 in Fig. 8, also marked with the red ellipse in Fig. 8(b)]. This source is motionless along x (or moves slowly as a whole with the ion velocity) so the role of the longitudinal velocity is not very important here [the radiation field of this source is approximately equal to the radiation of the same sheets calculated for β x = 0; cf. blue (dark ...
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... the total radiation of the plasma layer at t = 9.2T 0 ). From Fig. 8(a), one can conclude that, generally, there are two sources producing high-amplitude radiation. One source of radiation is formed in the region, where the electron density is maximal [radiation of the electrons from x 15.7 to x 16 in Fig. 8, also marked with the red ellipse in Fig. 8(b)]. This source is motionless along x (or moves slowly as a whole with the ion velocity) so the role of the longitudinal velocity is not very important here [the radiation field of this source is approximately equal to the radiation of the same sheets calculated for β x = 0; cf. blue (dark gray) and magenta (medium gray) lines in Fig. ...
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... in Fig. 8(b)]. This source is motionless along x (or moves slowly as a whole with the ion velocity) so the role of the longitudinal velocity is not very important here [the radiation field of this source is approximately equal to the radiation of the same sheets calculated for β x = 0; cf. blue (dark gray) and magenta (medium gray) lines in Fig. 8(a)]. Because of the very small dimensions of the radiation source (less than λ 0 /2), it can radiate ...
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... second radiation source is formed by the electron sheets, which are near the point where β y ≈ 0 and β x ≈ 1 (from x 15.2 to x 15.4 in Fig. 8). Here, the role of the longitudinal velocity is very important, and the radiation field of this source is considerably greater than the radiation of the same sheets calculated for β x = 0 [cf. blue (dark gray) and magenta (medium gray) lines in Fig. 8(a) near point x = 15.3]. The maximal amplitude of the radiation of this source can be ...
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... at the position of this electron. So the position of each point where A = 0 and β y = 0 is defined by the vector potential solely and, thus, the radiations of all electrons near this point have the same phase, which is determined by the vector potential [in spite of different longitudinal velocities of the electrons; cf. blue and black lines in Fig. 8(a)]. Before transmission, the points of A = 0 move slowly to the right because the reflected wave has a decreased frequency (due to acceleration of ions and slow motion of the boundary). In this case, the radiation field of such a point cannot sum up coherently and grow in time so the amplitude of the total radiation is small. When ...
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Citations
... The fast ions, accelerated in the channel, show a high directionality and may be used to heat a pre-compressed target core to fusion conditions. The ultra-intense EUV laser pulses with durations of several femtoseconds used in this scheme might be obtained by relativistic laser-foil interaction with the method combining the relativistic flying mirror and dispersion compensation technique, [31][32][33][34] which can make light intensification toward the Schwinger limit. 35 By optimizing the plasma density scale length, pulse contrast, and beam quality, 36,37 there is still room for improvements in the harmonics conversion efficiency. ...
A scheme of using two-color laser pulses for hole boring into overdense plasma as well as energy transfer into electron and ion beams has been studied using particle-in-cell simulations. Following an ultra-short ultra-intense hole-boring laser pulse with a short central wavelength in extreme ultra-violet range, the main infrared driving laser pulse can be guided in the hollow channel preformed by the former laser and propagate much deeper into an overdense plasma, as compared to the case using the infrared laser only. In addition to efficiently transferring the main driving laser energy into energetic electrons and ions generation deep inside the overdense plasma, the ion beam divergence can be greatly reduced. The results might be beneficial for the fast ignition concept of inertial confinement fusion.
... Numerous simulations have exploited the TOR to accelerate ions 7-10 , shape intense laser pulses [11][12][13][14][15] and produce X-rays [16][17][18][19] with unique characteristics. However, so far, clear observation 1 Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA, 2 Ludwig-Maximilan-Universität, München, D-85748 Garching, Germany, 3 Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany, 4 Centre for Plasma Physics, Department of Physics and Astronomy, Queens University Belfast BT7 1NN, UK. *e-mail: sasi@lanl.gov; ...
Overdense plasmas are usually opaque to laser light. However, when the
light is of sufficient intensity to drive electrons in the plasma to
near light speeds, the plasma becomes transparent. This process--known
as relativistic transparency--takes just a tenth of a picosecond. Yet
all studies of relativistic transparency so far have been restricted to
measurements collected over timescales much longer than this, limiting
our understanding of the dynamics of this process. Here we present
time-resolved electric field measurements (with a temporal resolution of
~ 50fs) of the light, initially reflected from, and subsequently
transmitted through, an expanding overdense plasma. Our result provides
insight into the dynamics of the transparent-overdense regime of
relativistic plasmas, which should be useful in the development of
laser-driven particle accelerators, X-ray sources and techniques for
controlling the shape and contrast of intense laser pulses.
A numerical simulation of the interaction of a laser pulse with ultrathin targets has revealed a possibility of generating thin dense relativistic electron layers. The maximum kinetic energy of the electron mirror can be gained using an optimal combination of the target thickness and the laser pulse intensity and duration. It is proposed to use an additional (second) laser target, located at an optimal distance from the first target to cut off the laser pulse from the electron layer when the latter gains a maximum kinetic energy. This relativistic electron mirror can be used for efficient generation of 'hard' coherent radiation via counter reflection of an additional (probe) laser pulse from the mirror.
A versatile shaping of a laser pulse using relativistic transparency in
an overdense plasma has been studied. First we present the propagation
of a linearly polarized pulse through an overdense plasma and a
semi-phenomenological 1-dimensional formula to calculate the
channel-digging speed. Second the pulse shaping both in longitudinal and
transverse directions using a non-uniform plasma slab is presented by
2-dimensional particle-in-cell simulations. The second subject is a
unique point of this work in the context of relativistic transparency
and pulse shaping. Furthermore the 2-dimensional results are shown to be
in a good agreement with the 1-dimensional formula of the
channel-digging. The shaping scheme using non-uniform plasmas gives more
freedom to the control of the shape of ultraintense pulses for various
purposes.
We analyse the steepening of the leading edge of femtosecond petawatt pulses with the use of plasma layers and show that, at an electron density several times higher than the critical one, an asymmetric (in time domain) pulse can be produced with an amplitude of the first half-wave differing little from the maximum pulse amplitude. Using numerical simulation, we have studied the interaction of such pulses with nanometre-thick films, including the generation of relativistic electron mirrors and the reflection of a counterpropagating probe pulse from such mirrors. The resulting coherent X-ray pulses have a duration of ~120 as and a power of ~600 GW at a wavelength of ~13 nm. Our results demonstrate that the reflectivity of a relativistic electron mirror situated in the accelerating pulse field is independent of the probe pulse amplitude when it increases up to the accelerating pulse amplitude.
We report a comprehensive analysis of an earlier proposed method which employs ultrahigh-power (petawatt) circularly polarised laser radiation to generate multiply charged ion beams in its interaction with a nanostructured two-component target; the ion beams are intended for application in nuclear physics. The problems of heavy atom ionisation in a superstrong laser field and laserinduced acceleration of the resultant ions to energies of ~20 – 30 MeV/nucleon are considered.
A new method of generation of high-energy highly charged ion beams is proposed. The method is based on the interaction of petawatt circularly polarized laser pulses with high-Z compound targets consisting of two species of different charge-to-mass ratio. It is shown that highly charged ions produced by field ionization can be accelerated up to tens of MeV/u with ion (actually with Z≤25) beam parameters like density and total charge inaccessible in conventional accelerators. A possibility of further ionization of the accelerated ion bunches in foil is also discussed.
Relativistic electromagnetic penetration behavior is reexamined in the
relativistic transparency region. The interaction is modeled by the
relativistic hydrodynamic equations coupled with the full system of Maxwell
equations, which are solved by a fully implicit energy-conserving numerical
scheme. For the first time, we have studied the penetration behavior through
ultra-short circularly polarized and linearly polarized laser pulses
interaction with over-dense plasmas. It is shown that for the ultra-short
circularly polarized laser penetration occurs through a soliton like behavior,
which is quite consistent with the existing studies. However, we have found
that the ultra-short linearly polarized laser penetrates through a breather
like behavior, and there is an energy transition mechanism with a frequency
$2\omega_0$ between the penetrated breather like structure and the background
plasmas. A qualitative interpretation has been given to describe this mechanism
of energy exchange.
