Relativistic ponderomotive forces in the field of intense laser radiation

Castillo, A. J.; Milant’ev, V. P.

doi:10.1134/s1063784214090138

Cited by 5 publications

(5 citation statements)

References 13 publications

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“…First, we study the analytically predicted scattering angles as a function of initial transverse displacement. In fact, from numerical checks we find our above conjecture confirmed that in the focus dominated regime those electrons are scattered into the largest angles that are initially at a transverse displacement x w v ,0 peak 0 = Ŵ ( )and that the peak scattering angle is accordingly well reproduced by equation (33). Next, from a full numerical propagation of the electron trajectories according to equation (4) we find that at asymptotic times after the interaction with the laser focus the distribution of transverse velocities, which is equivalent to the distribution of scattering angles, is indeed confined to a circular disk (see figure 4(a)).…”

Section: Numerical Benchmarkssupporting

confidence: 54%

“…Of these we naturally have to consider the earlier time, as we do not wish to consider re-entry into the focal volume. Comparing (33) and (36) we find that in this case of Ω>1/2 the analytical result does not predict a continuous distribution of scattering angles for varying initial displacements x ⊥,0 but is discontinuous at x ,0 max . To see this, it is sufficient to note that in this regime x l w l sin sin ,0…”

Section: Focus Dominated Ponderomotive Scatteringmentioning

confidence: 76%

“…Such, so-called ponderomotive scattering of the electrons was subject of numerous previous publications [18][19][20][21][22][23]. In the relativistic regime, a generalized ponderomotive force equation was derived from a Hamiltonian approach [24] with many alternative derivations [25][26][27][28][29][30][31][32][33][34] and experimental confirmation [35,36] following. These studies were later used in a series of technical and fundamental applications [37,38].…”

Section: Introductionmentioning

confidence: 99%

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Ultra-intense laser pulse characterization using ponderomotive electron scattering

2019

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We present a new analytical solution for the equation of motion of relativistic electrons in the focus of a high-intensity laser pulse. We approximate the electron's transverse dynamics in the averaged field of a long laser pulse focused to a Gaussian transverse profile. The resultant ponderomotive scattering is found to feature an upper boundary of the electrons' scattering angles, depending on the laser parameters and the electrons' initial state of motion. In particular, we demonstrate the angles into which the electrons are scattered by the laser scale as a simple relation of their initial energy to the laser's amplitude. We find two regimes to be distinguished in which either the laser's focusing or peak power are the main drivers of ponderomotive scattering. Based on this result, we demonstrate how the intensity of a laser pulse can be determined from a ring-shaped pattern in the spatial distribution of a high-energy electron beam scattered from the laser. We confirm our analysis by means of detailed relativistic test particle simulations of the electrons' averaged ponderomotive dynamics in the full electromagnetic fields of the focused laser pulse.for providing this key laser parameter is the combination of three different and distinct measurements: (a) pulse energy of the fully amplified, collimated beam; (b) pulse duration of a fraction of the collimated beam, typically not at full amplification; and (c) focus imaging of typically a not fully amplified and with attenuating elements transported beam. There is a number of shortcomings of this approach: (a) it does not necessarily yield the energy concentrated within the focus; (b) it may differ across the beam profile due to radial dispersion and further nonlinear effects [41,42]. (c) It is a time-and spectrum-integrated measurement. Due to the previous effects as well as radial group delay and chromatic aberrations [43,44], the pulse duration in the focus can be much longer than measured with (b) and exhibit time structures varying with the focal position. Hence, the typical procedure yields rather an upper limit of peak intensity.Atomic effects have been proposed and employed to yield a measure of peak intensity [45][46][47], but were restricted to non-relativistic intensities. At higher intensity, atomic ionization is followed by significant electron acceleration which can also provide information on peak intensity and focus size [48,49]. Experimental realizations of this concept were successfully implemented at mildly relativistic intensities [50,51]. Relativistic, intensity-dependent plasma effects like ion acceleration [52][53][54][55], on the other hand, are not feasible since they are quite sensitive to the temporal contrast of the laser pulse [9, 56], as the plasma formation prior to the pulse peak strongly affects the energy conversion during the peak. Hence, measurements of laser-scattered electron distributions could be a reasonable alternative, especially when relying on beam profile measurements which are much simpler than spectral measuremen...

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Section: Numerical Benchmarkssupporting

confidence: 54%

Section: Focus Dominated Ponderomotive Scatteringmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

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Ultra-intense laser pulse characterization using ponderomotive electron scattering

2019

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“…However, it is necessary that the quickly oscillating members have small amplitude in order to apply the averaging method. This can be achieved if we firstly exclude in the equations of motion the quickly oscillating members with large amplitudes [20,21]. In this regard, we will make the replacement of the transverse components of the particle momentum vector, which is convenient to use in the complex form: In the equation (14) the first member on the right is quickly oscillating with large amplitude.…”

Section: Averaged Equations Of Motion For a Charged Particlementioning

confidence: 99%

On the radiation losses during motion of an electron in the field of intense laser radiation

Dobrova

Валерьевна²,

Milantiev

et al. 2019

Discrete and Continuous Models

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Motion of the relativistic electron in the field of intense laser pulse of the arbitrary shape is considered. The pulse dimension is supposed to be of the order of the Gaussian laser beam dimension in the focal plane. It is supposed that the pulse is propagating along the external constant magnetic field. In the paraxial approximation the corrections of the first order to the vectors of the field of radiation as well as the force of the radiation friction are taken into account. Averaged relativistic equations of motion of electron are obtained with the help of averaging over the fast oscillations of the laser radiation. It is shown that with taking into account corrections of the first order to the field vectors an averaged force arises. This force is defined by pulsed character of radiation and proportional to the intensity but not to gradient of intensity. It is shown that radiation losses are of little importance in the transverse plane but may considerably act on the longitudinal motion of electron.

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“…As most ultra-intense lasers yield pulses containing several cycles of the optical carrier wave, neglecting the electrons' sub-cycle quivering is sufficient to first-order a cycle averaged approach. The resulting ponderomotive scattering, arising from the radial gradient of the laser's intensity profile, was extensively studied in the non-relativistic regime [39][40][41][42][43][44], later translated to the relativistic regime [45][46][47][48][49][50][51][52][53][54][55] and experimentally observed [56,57].…”

Section: Introductionmentioning

confidence: 99%

Characterization of ultra-intense laser in radiation damping regime using ponderomotive scattering

Holkundkar¹,

Mackenroth²

2022

Plasma Phys. Control. Fusion

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We present a novel approach to analyzing phase-space distributions of electrons ponderomotively scattered off an ultra-intense laser pulse and comment on implications for thus conceivable in-situ laser-characterization schemes. To this end, we present fully relativistic test particle simulations of electrons scattered from an ultra-intense, counter-propagating laser pulse. The simulations unveil non-trivial scalings of the scattered electron distribution with the laser intensity, pulse duration, beam waist, and energy of the electron bunch. We quantify the found scalings by means of an analytical expression for the scattering angle of an electron bunch ponderomotively scattered from a counter-propagating, ultra-intense laser pulse, also accounting for radiation reaction (RR) through the Landau-Lifshitz (LL) model. For various laser and bunch parameters, the derived formula is in excellent quantitative agreement with the simulations. We also demonstrate how in the radiation-dominated regime a simple re-scaling of our model's input parameter yields quantitative agreement with numerical simulations based on the LL model.

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Relativistic ponderomotive forces in the field of intense laser radiation

Cited by 5 publications

References 13 publications

Ultra-intense laser pulse characterization using ponderomotive electron scattering

Ultra-intense laser pulse characterization using ponderomotive electron scattering

On the radiation losses during motion of an electron in the field of intense laser radiation

Characterization of ultra-intense laser in radiation damping regime using ponderomotive scattering

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