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In this article we investigate novel signatures of radiation reaction via the angular deflection of an electron beam colliding at 90 degrees with an intense laser pulse. Due to the radiation reaction effect, the electrons can be deflected towards the beam axis for plane wave backgrounds, which is not possible in the absence of radiation reaction effects. The magnitude and size of the deflection angle can be controlled by tailoring the laser pulse shapes. The effect is first derived analytically using the Landau-Lifshitz equation, which allows to determine the important scaling behavior with laser intensity and particle energy. We then move on to full scale 3D Monte Carlo simulations to verify the effect is observable with present day laser technology. We investigate the opportunities for an indirect observation of laser depletion in such side scattering scenarios.

Accelerating a free electron to high‐energy forms the basis for studying particle and nuclear physics. Here it is shown that the wave function of such an energetic electron can be further manipulated with the femtosecond intense lasers. During the scattering between a high‐energy electron and a circularly polarized laser pulse, a regime is found where the enormous spin angular momenta of laser photons can be efficiently transferred to the electron orbital angular momentum (OAM). The wave function of the scattered electron is twisted from its initial plane‐wave state to the quantum vortex state. Nonlinear quantum electrodynamics (QED) theory suggests that the GeV‐level electrons acquire average intrinsic OAM beyond ⟨l⟩∼100ℏ$\langle l \rangle \sim 100\hbar $ at laser intensities of 1020 W cm−2 with linear scaling. These electrons emit γ‐photons with two‐peak spectrum, which sets them apart from the ordinary electrons. The findings demonstrate a proficient method for generating relativistic leptons with the vortex wave functions based on existing laser technology, thereby fostering a novel source for particle and nuclear physics. [ABSTRACT FROM AUTHOR]

Abstract Accelerating a free electron to high‐energy forms the basis for studying particle and nuclear physics. Here it is shown that the wave function of such an energetic electron can be further manipulated with the femtosecond intense lasers. During the scattering between a high‐energy electron and a circularly polarized laser pulse, a regime is found where the enormous spin angular momenta of laser photons can be efficiently transferred to the electron orbital angular momentum (OAM). The wave function of the scattered electron is twisted from its initial plane‐wave state to the quantum vortex state. Nonlinear quantum electrodynamics (QED) theory suggests that the GeV‐level electrons acquire average intrinsic OAM beyond ⟨l⟩∼100ℏ at laser intensities of 1020 W cm−2 with linear scaling. These electrons emit γ‐photons with two‐peak spectrum, which sets them apart from the ordinary electrons. The findings demonstrate a proficient method for generating relativistic leptons with the vortex wave functions based on existing laser technology, thereby fostering a novel source for particle and nuclear physics.

In classical electrodynamics, the well-known Lorentz force law falls short of providing a satisfactory result for the trajectory of point-like charged particles when considering that particle's own self-force. While there have been many historical attempts, Gralla, Harte and Wald developed a new model for classical charged particles that is free from pathologies while being consistent with Maxwell's equations and conserves stress-energy. Expanding upon this approach, we derive a relativistically correct, modified Lorentz force law in vector form, which includes radiation reaction, and spin- and magnetic moment-dependent correction terms, suitable to be included in classical electrodynamics lectures and beam dynamics simulation tools. As by-products we obtain evolution equations for mass, spin angular momentum and the radiated power. We compare the new equations to the classical ones and use the new equations to conduct numerical simulations, showing that the results are free of any nonphysical artifacts, and which might be possible to test in future experiments at particle accelerators. The new equations foster improved insight into beam dynamics. [ABSTRACT FROM AUTHOR]

In this third of a series on quantum radiation, we further explore the feasibility of using the memories (non-Markovianity) kept in a quantum field to decipher certain information about the early universe. As a model study, we let a massless quantum field be subjected to a parametric process for a finite time interval such that the mode frequency of the field transits from one constant value to another. This configuration thus mimics a statically-bounded universe, where there is an ‘in’ and an ‘out’ state with the scale factor approaching constants, not a continuously evolving one. The field subjected to squeezing by this process should contain some information of the process itself. If an atom is coupled to the field after the parametric process, its response will depend on the squeezing, and any quantum radiation emitted by the atom will carry this information away so that an observer at a much later time may still identify it. Our analyses show that (1) a remote observer cannot measure the generated squeezing via the radiation energy flux from the atom because the net radiation energy flux is canceled due to the correlation between the radiation field from the atom and the free field at the observer’s location. However, (2) there is a chance to identify squeezing by measuring the constant radiation energy density at late times. The only restriction is that this energy density is of the near-field nature and only an observer close to the atom can use it to unravel the information of squeezing. The second part of this paper focuses on (3) the dependence of squeezing on the functional form of the parametric process. By explicitly working out several examples, we demonstrate that the behavior of squeezing does reflect essential properties of the parametric process. Actually, striking features may show up in more complicated processes involving various scales. These analyses allow us to establish the connection between properties of a squeezed quantum field and details of the parametric process which performs the squeezing. Therefore, (4) one can construct templates to reconstitute the unknown parametric processes from the data of measurable quantities subjected to squeezing. In a sequel paper these results will be applied to a study of quantum radiations in cosmology.

In this third of a series on quantum radiation, we further explore the feasibility of using the memories (non-Markovianity) kept in a quantum field to decipher certain information about the early universe. As a model study, we let a massless quantum field be subjected to a parametric process for a finite time interval such that the mode frequency of the field transits from one constant value to another. This configuration thus mimics a statically-bounded universe, where there is an 'in' and an 'out' state with the scale factor approaching constants, not a continuously evolving one. The field subjected to squeezing by this process should contain some information of the process itself. If an atom is coupled to the field after the parametric process, its response will depend on the squeezing, and any quantum radiation emitted by the atom will carry this information away so that an observer at a much later time may still identify it. Our analyses show that (1) a remote observer cannot measure the generated squeezing via the radiation energy flux from the atom because the net radiation energy flux is canceled due to the correlation between the radiation field from the atom and the free field at the observer's location. However, (2) there is a chance to identify squeezing by measuring the constant radiation energy density at late times. The only restriction is that this energy density is of the near-field nature and only an observer close to the atom can use it to unravel the information of squeezing. The second part of this paper focuses on (3) the dependence of squeezing on the functional form of the parametric process. By explicitly working out several examples, we demonstrate that the behavior of squeezing does reflect essential properties of the parametric process. Actually, striking features may show up in more complicated processes involving various scales. These analyses allow us to establish the connection between properties of a squeezed quantum field and details of the parametric process which performs the squeezing. Therefore, (4) one can construct templates to reconstitute the unknown parametric processes from the data of measurable quantities subjected to squeezing. In a sequel paper these results will be applied to a study of quantum radiations in cosmology. [ABSTRACT FROM AUTHOR]

In this article we investigate novel signatures of radiation reaction via the angular deflection of an electron beam colliding at 90 degrees with an intense laser pulse. Due to the radiation reaction effect, the electrons can be deflected towards the beam axis for plane wave backgrounds, which is not possible in the absence of radiation reaction effects. The magnitude and size of the deflection angle can be controlled by tailoring the laser pulse shapes. The effect is first derived analytically using the Landau–Lifshitz equation, which allows to determine the important scaling behavior with laser intensity and particle energy. We then move on to full scale 3D Monte Carlo simulations to verify the effect is observable with present day laser technology. We investigate the opportunities for an indirect observation of laser depletion in such side scattering scenarios.

Abstract Because radiation is essential in high‐frequency circuits, such as those used in metamaterials and plasmonics, the investigation of radiation loss is important. This study describes the characteristics of radiation loss, which is a radiation reaction in circuits with retarded electromagnetic couplings. The structure of wired metallic spheres is used to demonstrate metamaterial equivalent circuits, where charges and current exist on the spheres and wires, respectively. An inductance matrix and a potential coefficient matrix with retarded electromagnetic couplings are defined to address the radiation reaction. Subsequently, based on the topology of the wires and spheres, an equivalent circuit equation with retardation is formulated to discuss the losses in the resonant circuit caused by the inductive and capacitive elements. Thereafter, the relationship between the resonant frequency and radiation loss caused by the retarded couplings is demonstrated and the difference between the retarded couplings and couplings with transmission lines is clarified. Furthermore, we indicate that retarded coupling generates singularity on a dispersion curve for a one‐dimensional array of resonant circuits. Thus, the circuit with retarded couplings generates novel characteristics of radiation reactions that are not represented by the circuit without retardation. This circuit analysis is expected to afford new aspects in studies on topics, such as metamaterials and plasmonics.

A point charge accelerating under the influence of an external force emits electromagnetic radiation that reduces the increase in its mechanical energy. This causes a reduction in the particle's acceleration. We derive the decrease in acceleration due to radiation reaction for a particle accelerating parallel to its velocity, and show that it has a negligible effect. [ABSTRACT FROM AUTHOR]

The optimum parameters for the generation of synchrotron radiation in ultraintense laser pulse interactions with planar foils are investigated with the application of Bayesian optimization, via Gaussian process regression, to 2D particle-in-cell simulations. Individual properties of the synchrotron emission, such as the yield, are maximized, and simultaneous mitigation of bremsstrahlung emission is achieved with multi-variate objective functions. The angle-of-incidence of the laser pulse onto the target is shown to strongly influence the synchrotron yield and angular profile, with oblique incidence producing the optimal results. This is further explored in 3D simulations, in which additional control of the spatial profile of synchrotron emission is demonstrated by varying the polarization of the laser light. The results demonstrate the utility of applying a machine learning-based optimization approach and provide new insights into the physics of radiation generation in laser--foil interactions, which will inform the design of experiments in the quantum electrodynamics (QED)-plasma regime. [ABSTRACT FROM AUTHOR]

The optimum parameters for the generation of synchrotron radiation in ultraintense laser pulse interactions with planar foils are investigated with the application of Bayesian optimization, via Gaussian process regression, to 2D particle-in-cell simulations. Individual properties of the synchrotron emission, such as the yield, are maximized, and simultaneous mitigation of bremsstrahlung emission is achieved with multi-variate objective functions. The angle-of-incidence of the laser pulse onto the target is shown to strongly influence the synchrotron yield and angular profile, with oblique incidence producing the optimal results. This is further explored in 3D simulations, in which additional control of the spatial profile of synchrotron emission is demonstrated by varying the polarization of the laser light. The results demonstrate the utility of applying a machine learning-based optimization approach and provide new insights into the physics of radiation generation in laser–foil interactions, which will inform the design of experiments in the quantum electrodynamics (QED)-plasma regime.

In ultra-high power laser interaction with plasma, quantum electrodynamics phenomena such as high energy photon emission by electrons, radiation reaction trapping, and anti-particle creation can affect the interaction mechanism. In the present work, the interaction mechanism of the circular and linear laser with an intensity higher than 1023 W/cm2 with rarified plasma in the presence of the radiation reaction force has been investigated using particle in cell simulation. The results indicate that radiation reaction trapping for circular polarization is more effective than the linear one. Also, photons emitted by electrons have a higher density for circular polarization. For both polarizations, at later times of the interaction, considering photon emission and radiation reaction effects lead to the significant decrement of the cut-off energy of electrons. The cut-off energy of the emitted photons for circular polarization is higher than that of linear polarization.

It is possible to accelerate efficiently a charged particle toward the speed of light through a spatially modulated electrostatic field and through the superposition of a spatially modulated magnetic field and a laser. In both cases, the acceleration process requires an adequate initial velocity of the particle and depends on the amplitude of the fields, the length scale of the modulation and the wavenumbers, and frequencies of the fields. The physics behind these accelerators involves a resonance between the particle’s velocity and the field’s phase velocity. The promising results, however, may be affected when the radiation reaction effect is included in the calculations. Understanding the role of the radiation reaction over these schemes is the aim of the present work. As we are going to show, in a counter-intuitive way, the effects of radiation reaction can help to accelerate charge particles under some specific conditions. [ABSTRACT FROM AUTHOR]

Because radiation is essential in high‐frequency circuits, such as those used in metamaterials and plasmonics, the investigation of radiation loss is important. This study describes the characteristics of radiation loss, which is a radiation reaction in circuits with retarded electromagnetic couplings. The structure of wired metallic spheres is used to demonstrate metamaterial equivalent circuits, where charges and current exist on the spheres and wires, respectively. An inductance matrix and a potential coefficient matrix with retarded electromagnetic couplings are defined to address the radiation reaction. Subsequently, based on the topology of the wires and spheres, an equivalent circuit equation with retardation is formulated to discuss the losses in the resonant circuit caused by the inductive and capacitive elements. Thereafter, the relationship between the resonant frequency and radiation loss caused by the retarded couplings is demonstrated and the difference between the retarded couplings and couplings with transmission lines is clarified. Furthermore, we indicate that retarded coupling generates singularity on a dispersion curve for a one‐dimensional array of resonant circuits. Thus, the circuit with retarded couplings generates novel characteristics of radiation reactions that are not represented by the circuit without retardation. This circuit analysis is expected to afford new aspects in studies on topics, such as metamaterials and plasmonics. [ABSTRACT FROM AUTHOR]

Since a classical charged point particle radiates energy and momentum it is argued that there must be a radiation reaction force. Here we present an action for the Maxwellâ€"Lorentz without self-interactions model, where each particle only responds to the fields of the other charged particles. The corresponding stressâ€"energy tensor automatically conserves energy and momentum in Minkowski and other appropriate spacetimes. Hence there is no need for any radiation reaction. [ABSTRACT FROM AUTHOR]

We study the interatomic energy and force of two ground-state atoms in interaction with the fluctuating quantum massless scalar field in vacuum with two different approaches, i.e. the stationary perturbation theory and the DDC formalism [the formalism proposed by Dalibard, Dupont-Roc and Cohen-Tannoudji]. With the DDC formalism, we calculate the interatomic energy in terms of the contributions of vacuum fluctuations and the contributions of the atomic radiation reaction. We find that, in the near region, the contributions of vacuum fluctuations is less important than the contributions of the atomic radiation reaction, and as a result, the interatomic force is attractive and proportional to L− 3. While in the far zone, the contributions of vacuum fluctuations and those of the atomic radiation reaction become equally important, and the interatomic force is attractive and proportional to L− 4. The interatomic energy and force derived with these two different approaches are accurately the same. We comment that the two different approaches deal with the interatomic interaction from different perspectives and have their own advantages. [ABSTRACT FROM AUTHOR]

The electromagnetic self-force of a point charge moving arbitrarily on a rectilinear trajectory is calculated by averaging its retarded electric self-field over a sphere of infinitesimal radius centred on the charge's present position. The finite part of the self-force obtained is the well-established relativistic radiation reaction, while its divergent part implies the pre-relativistic longitudinal electromagnetic mass of Abraham. [ABSTRACT FROM AUTHOR]

We study electron acceleration in a plasma wakefield under the influence of the radiation-reaction force caused by the transverse betatron oscillations of the electron in the wakefield. Both the classical and the strong quantum-electrodynamic (QED) limits of the continuous radiation reaction are considered. For the constant accelerating force, we show that the amplitude of the oscillations of the QED parameter χ in the radiation-dominated regime reaches an equilibrium value determined only by the magnitude of the accelerating field, while the averaged over betatron oscillations radiation reaction force saturates at a value smaller than the accelerating force and thus is incapable of stopping acceleration. We find the parameters of the electron bunch and the plasma accelerator for which reaching such a regime is possible. We also study effects of the dephasing and the corresponding change of the accelerating force over the course of acceleration and conclude that the radiation-dominated regime is realized both in cases of single-stage acceleration with slow dephasing (usually corresponding to bunch-driven plasma accelerators) and multi-stage acceleration with fast dephasing (corresponding to the use of laser-driven accelerators).

We investigate the effect of laser polarization on spatial and momentum distribution of back-reflected e-e+ pairs from the collision of an intense laser pulse (I=5 × 1022 W cm-2) with a counter-propagating 5 GeV electron beam. During the pair production, a significant amount of particles (106-107) are ejected in the opposite direction of the incoming electron beam (back-reflected), they are trapped by and co-propagate with the laser beam, gaining energy up to the GeV level. From our multi-dimensional particle-in-cell studies, we observe that laser polarization affects the angular distribution of these particles: a linearly polarized pulse produces two transversely separated particle jets, while a circular one leads to the formation of a radially symmetric cone-shaped emission. The results presented here add insights for future experiments performed at multi-PW laser facilities. [ABSTRACT FROM AUTHOR]

We have studied influence of STVG in circular motion of massive particle around the Schwarzschild-MOG black hole and discussed the Innermost Stable Circular Orbit (ISCO) and Marginally Bound Orbit (MBO) position of massive test particle. This research explores dynamics of massive particles within the framework of Scalar–Tensor–Vector Gravity (STVG) when navigating the vicinity of Schwarzschild-MOG black holes. The study extends its investigation to the angular velocity of massive particles orbiting Schwarzschild-MOG black holes, comparing it to predictions from general relativity. Finally, we have investigated gravitational analogue of radiation reaction by considering Landau–Abraham–Dirac equation in STVG. We have shown that because of radiation reaction massive test particle falls down to the black hole. [ABSTRACT FROM AUTHOR]

Classical radiation reaction is the effect of the electromagnetic field emitted by an accelerated electric charge on the motion of the charge itself. The self-consistent underlying classical equation of motion including radiation–reaction effects, the Landau–Lifshitz equation, has never been tested experimentally, in spite of the first theoretical treatments of radiation reaction having been developed more than a century ago. Here we show that classical radiation reaction effects, in particular those due to the near electromagnetic field, as predicted by the Landau–Lifshitz equation, can be measured in principle using presently available facilities, in the energy emission spectrum of 30-GeV electrons crossing a 0.55-mm thick diamond crystal in the axial channeling regime. Our theoretical results indicate the feasibility of the suggested setup, e.g., at the CERN Secondary Beam Areas (SBA) beamlines.

After more than a century of history, the radiation-reaction problem in classical electrodynamics still surprises and puzzles new generations of researchers. Here, we revise and explain some of the paradoxical issues that one faces when approaching the problem, mostly associated with regimes of uniform proper acceleration. The answers we provide can be found in the literature and are a synthesis of a large body of research. We only present them in a personal way that may help in their understanding. Besides, after the presentation of the standard answers, we motivate and present a twist to those ideas. The physics of emission of radiation by extended charges (charges with internal structure) might proceed in a surprising oscillating fashion. This hypothetical process could open up new research paths and a new take on the equivalence principle.

When accelerated by a constant force in the lab frame, a classical charge experiences no self force. In this case, the particle radiates without dissipating its kinetic and potential energy. But what happens when the particle enters another region with equal and opposite acceleration? Does the oscillating charge lose its mechanical energy similar to a radiating dipole, even though it seems to lose no mechanical energy within each region of constant acceleration? In this paper, I will show how mechanical energy is transferred to radiation energy via the Schott energy when the particle crosses the boundary between the two regions. In particular, I will show how preacceleration, which is usually regarded as an unphysical effect of the Lorentz–Abraham–Dirac self force, is essential for the energy transfer. Moreover, I will show that the commonly adopted Landau–Lifshitz approximation, which removes preacceleration, introduces second-order secular energy error. On a more fundamental level, the validity of classical electrodynamics is in fact questionable because quantum effects are likely important. The classical prediction can be tested experimentally by observing frequency chirping of radiation, whereby micro physics leaves signatures on macroscopic scales. The required experimental accuracy is estimated. Trap experiments of this type is complementary to collider experiments that endeavor to observe radiation reaction for elementary particles. [ABSTRACT FROM AUTHOR]

The Abraham–Lorentz force is a finite remnant of the UV singular structure of the self-interaction of a point charge with its own field. The satisfactory description of such an interaction needs a relativistic regulator. This turns out to be a problematic point because the energy of regulated relativistic cutoff theories is unbounded from below. However, one can construct point-splitting regulators which keep the Abraham–Lorentz force stable. The classical language can be reconciled with QED by pointing out that the effective quantum theory for the electric charge supports a saddle point producing the classical radiation reaction forces. [ABSTRACT FROM AUTHOR]

Recent high-intensity laser experiments (Cole et al 2018 Phys. Rev. X 8 011020; Poder et al 2018 Phys. Rev. X 8 031004) have shown evidence of strong radiation reaction in the quantum regime. Experimental evidence of quantum effects on radiation reaction and electron–positron pair cascades has, however, proven challenging to obtain and crucially depends on maximising the quantum parameter of the electron (defined as the ratio of the electric field it feels in its rest frame to the Schwinger field). The quantum parameter can be suppressed as the electrons lose energy by radiation reaction as they traverse the initial rise in the laser intensity. As a result the shape of the intensity temporal envelope becomes important in enhancing quantum radiation reaction effects and pair cascades. Here we show that a realistic laser pulse with a faster rise time on the leading edge, achieved by skewing the temporal envelope, results in curtailing of pair yields as the peak power is reduced. We find a reduction in pair yields by orders of magnitude in contrast to only small reductions reported previously in large-scale particle-in-cell code simulations (Hojbota et al 2018 Plasma Phys. Control. Fusion 60 064004). Maximum pairs per electron are found in colliding 1.5 GeV electrons with a laser wakefield produced envelope 7.90 × 10 ^−2 followed by a short 50 fs Gaussian envelope, 1.90 × 10 ^−2 , while it is reduced to 8.90 × 10 ^−5 , a factor of 100, for an asymmetric envelope.

State-of-the-art numerical simulations of quantum electrodynamical (QED) processes in strong laser fields rely on a semiclassical combination of classical equations of motion and QED rates, which are calculated in the locally constant field approximation. However, the latter approximation is unreliable if the amplitude of the fields, a _0 , is comparable to unity. Furthermore, it cannot, by definition, capture interference effects that give rise to harmonic structure. Here we present an alternative numerical approach, which resolves these two issues by combining cycle-averaged equations of motion and QED rates calculated in the locally monochromatic approximation. We demonstrate that it significantly improves the accuracy of simulations of photon emission across the full range of photon energies and laser intensities, in plane-wave, chirped and focused background fields.

Using a test-particle model, we examine direct laser acceleration of electrons within a magnetic filament that has been shown to form inside a laser-irradiated plasma. We focus on ultra-high intensity interactions where the force of radiation friction caused by electron emission of electromagnetic radiation must be taken into account. It is shown that even relatively weak superluminosity of laser wave fronts—the feature that has been previously neglected—qualitatively changes the electron dynamics, leading to a so-called attractor effect. As a result of this effect, electrons with various initial energies reach roughly the same maximum energy and emit roughly the same power in the form of x-rays and gamma-rays. Our analysis implies that the primary cause of the superluminosity is the laser-heated plasma. The discovered strong interplay between superluminosity and radiation friction is of direct relevance to laser-plasma interactions at high-intensity multi-PW laser facilities.

A classical model of radiation reaction for the betatron oscillation of an electron in a plasma wakefield accelerator is presented. The maximum energy of the electron due to the longitudinal radiation reaction is found, and the betatron oscillation damping due to both the longitudinal and transverse radiation reaction effects is analyzed. Both theoretical and numerical solutions are shown with good agreements. The regime that the quantum radiation takes effect is also discussed. This model is important for designing future plasma based super accelerators or colliders.

The Landau–Lifshitz (LL) equation has been proposed as the classical equation to describe the dynamics of a charged particle in a strong electromagnetic field when influenced by radiation reaction. Until recently, there has been no clear experimental verification. However, aligned crystals have remedied the situation: here, as in Nielsen et al CERN NA63 Collaboration (2020 Phys. Rev. D 102 052004), we report on a quantitative experimental test of the LL equation by measuring the emission spectra of electrons and positrons penetrating aligned single crystals. The recorded spectra are in remarkable agreement with simulations based on the LL equation of motion with moderate quantum corrections for recoil and, in the case of electrons in axially aligned crystals, spin and reduced radiation intensity.

We present new exact solutions of the Landau–Lifshitz (LL) and higher-order LL equations describing particle motion, with radiation reaction, in intense electromagnetic fields. Through these solutions and others we compare the phenomenological predictions of different equations in the context of the conjectured ‘radiation-free direction’ (RFD). We confirm analytically in several cases that particle orbits predicted by the LL equation indeed approach the RFD at extreme intensities, and give time-resolved signals of this behaviour in radiation spectra.

A charged particle subject to strong external forces will accelerate, and so radiate energy, inducing a self-force. This phenomenon remains contentious, but advances in laser technology mean we will soon encounter regimes where a more complete understanding is essential. The terms ‘self-force’ and ‘radiation reaction’ are often used synonymously, but reflect different aspects of the recoil force. For a particle accelerating in an electromagnetic field, radiation reaction is usually the dominant self-force, but in a scalar field this is not the case, and the total effect of the self-force can be anti-frictional. Aspects of this self-force can be recast in terms of spacetime geometry, and this interpretation illuminates the long-standing enigma of a particle radiating while experiencing no self-force.

The equation of motion for a radiating charged particle is known as the Lorentz–Abraham–Dirac (LAD) equation. The radiation reaction force in the LAD equation contains a third time-derivative term, called the Schott term, which leads to a runaway solution and a pre-acceleration solution. Since the Schott energy is the field energy confined to an area close to the particle and reversibly exchanged between particle and fields, the question of how it affects particle motion is of interest. In here we have obtained solutions for the LAD equation with and without the Schott term, and have compared them quantitatively. We have shown that the relative difference between the two solutions is quite small in the classical radiation reaction dominated regime.

A new spin-dependent deflection mechanism is revealed by considering the spin-correlated radiation-reaction force during laser-electron collision. We found that such deflection originates from the non-zero work done by the radiation-reaction force along the laser polarization direction in each half-period, which is larger/smaller for spin-anti-paralleled/spin-paralleled electrons. The resulted anti-symmetric deflection is further accumulated when the spin-projection onto the laser magnetic field is reversed in adjacent half-periods. The discovered mechanism dominates over the Stern–Gerlach deflection for electrons of several hundreds of MeV and 10 PW-level laser peak power. The results provide a new perspective to study the strong-field QED physics in quantum radiation-reaction regime and an approach to leverage the study of radiation-dominated and strong-field QED physics via particle spins.

Multi-petawatt laser systems will open up a novel interaction regime mixing collective plasma and quantum electrodynamic processes, giving rise to prolific generation of gamma-ray photons and electron–positron pairs. Here, using particle-in-cell simulations, we investigate the physics of the interaction of a 10 ^24 W cm ^−2 intensity, 30 fs duration, circularly polarized laser pulse with a long deuterium plasma at classically overcritical electron density (10 ^22 cm ^−3 ). We show that radiative trapping of the plasma electrons causes a high-density (∼5 × 10 ^23 cm ^−3 ), quasineutral electron–ion bunch to form inside the laser pulse. This phenomenon is accompanied by up to ∼40% energy conversion efficiency of the laser into gamma rays. Moreover, we find that both the radiation-modified Laplace force and the longitudinal electric field exerted on the positrons created by the multiphoton Breit–Wheeler process can accelerate them to GeV-range energies. We develop a theoretical model, the predictions of which provide a good match to the simulation results. Finally, we address the influence of the ion mass, showing that the laser absorption and positron acceleration is enhanced with deuterons compared to protons.

We study electron acceleration within a sub-critical plasma channel irradiated by an ultra-intense laser pulse ( a _0 > 100 or I > 10 ^22 W cm ^−2 ). In this regime, radiation reaction significantly alters the electron dynamics. This has an effect not only on the maximum attainable electron energy but also on the phase-matching process between betatron motion and electron oscillations in the laser field. Our study encompasses analytical description, test-particle calculations and two-dimensional particle-in-cell simulations. We show single-stage electron acceleration to multi-GeV energies within a 0.5 mm-long channel and provide guidelines how to obtain energies beyond 10 GeV using optimal initial configurations. We present the required conditions in a form of explicit analytical scaling laws that can be applied to plan the future electron acceleration experiments.