Y. Shi, D. Blackman, P. Zhu, and A. Arefiev, "Electron pulse train accelerated by a linearly polarized Laguerre-Gaussian laser beam", High Power Laser Science and Engineering (2022).
Paper of any type conference or journal
D. Blackman, R. Nuter, Ph. Korneev, A. Arefiev, and V. Tikhonchuk, "Kinetic phenomena of helical plasma waves with orbital angular momentum", Physics of Plasmas 29, 072105 (2022).
An accurate description of plasma waves is fundamental for the understanding of many plasma phenomena. It is possible to twist plasma waves such that, in addition to having longitudinal motion, they can possess a quantized orbital angular momentum. One such type of plasma wave is the Laguerre–Gaussian mode. Three-dimensional numerical particle-in-cell simulations demonstrate the existence of stable long-lived plasma waves with orbital angular momentum. These waves can be shown to create large amplitude static magnetic fields with unique twisted longitudinal structures. In this paper, we review the recent progress in studies of helical plasma waves and present a new analytical description of a standing Laguerre–Gaussian plasma wave mode along with 3D particle-in-cell simulation results. The Landau damping of twisted plasma waves shows important differences compared to standard longitudinal plasma wave Landau damping. These effects include an increased damping rate, which is affected by both the focal width and the orbital number of the plasma wave. This increase in the damping rate is of the same order as the thermal correction. Moreover, the direction of momentum picked up by resonant particles from the twisted plasma wave can be significantly altered. By contrast, the radial electric field has a subtle effect on the trajectories of resonant electrons.
K. Weichman, J. Palastro, A. Robinson, R. Bingham, and A. Arefiev, "Underdense relativistically thermal plasma produced by magnetically assisted direct laser acceleration", Phys. Rev. Research 4, L042017 (2022).
We introduce the first approach to volumetrically generate relativistically thermal plasma at gas-jet-accessible density. Using fully kinetic simulations and theory, we demonstrate that two stages of direct laser acceleration driven by two laser pulses in an applied magnetic field can heat a significant plasma volume to multi-MeV average energy. The highest-momentum feature is 2D-isotropic, persists after the interaction, and includes the majority of electrons, enabling experimental access to bulk-relativistic, high-energy-density plasma in an optically diagnosable regime for the first time.
Z. Gong, S. S. Bulanov, T. Toncian, and A. Arefiev, "Energy-chirp compensation of laser-driven ion beams enabled by structured targets", Phys. Rev. Research 4, L042031 (2022).
We show using three-dimensional (3D) simulations that the challenge of generating dense monoenergetic laser-driven ion beams with low angular divergence can be overcome by utilizing structured targets with a relativistically transparent channel and an overdense wall. In contrast to a uniform target that produces a chirped ion beam, the target structure facilitates the formation of a dense electron bunch whose longitudinal electric field reverses the energy chirp. This approach works in conjunction with existing acceleration mechanisms, augmenting the ion spectra. For example, our 3D simulations predict a significant improvement for a 2 PW laser pulse with a peak intensity of 5×1022 W/cm2. The simulations show a monoenergetic proton peak in a highly desirable energy range of 200 MeV with an unprecedented charge of several nC and a relatively low divergence that is below 10o.
D. Blackman, Y. Shi, S. Klein, M. Cernaianu, D. Doria, P. Ghenuche, and A. Arefiev, "Electron acceleration from transparent targets irradiated by ultra-intense helical laser beams", Communications Physics 5, 116 (2022).
The concept of electron acceleration by a laser beam in vacuum is attractive due to its seeming simplicity, but its implementation has been elusive, as it requires efficient electron injection into the beam and a mechanism for counteracting transverse expulsion. Electron injection during laser reflection off a plasma mirror is a promising mechanism, but it is sensitive to the plasma density gradient that is hard to control. We get around this sensitivity by utilizing volumetric injection that takes place when a helical laser beam traverses a low-density target. The electron retention is achieved by choosing the helicity, such that the transverse field profiles are hollow while the longitudinal fields are peaked on central axis. We demonstrate using three-dimensional simulations that a 3 PW helical laser can generate a 50 pC low-divergence electron beam with a maximum energy of 1.5 GeV. The unique features of the beam are short acceleration distance (∼100 μm), compact transverse size, high areal density, and electron bunching (∼100 as bunch duration).
Y. He, T. G. Blackburn, T. Toncian, and A. Arefiev, "Achieving pair creation via linear and nonlinear Breit-Wheeler processes in dense plasmas", Physics of Plasmas 29, 053105 (2022).
It has been recently shown that over 109 electron–positron pairs can be produced from light alone at an experimentally accessible laser intensity of 5×1022 W/cm2 by irradiating a target with a pre-formed channel by two counter-propagating laser pulses. Although targets of variable length and channel density have been successfully fabricated and used in recent experiments involving high-intensity lasers, the impact of these parameters on the pair yield by different pair creation processes is yet to be understood. In this paper, we explore, using two-dimensional particle-in-cell simulations, the impact of the channel density and length on pair production by the linear Breit–Wheeler process, nonlinear Breit–Wheeler process, and Bethe–Heitler process at fixed laser intensity. We find that these parameters can be successfully used to increase the linear Breit–Wheeler pair yield. More importantly, the relative contribution of each process can be adjusted by varying the same parameters. We show that this approach allows us to completely eliminate the yield from the nonlinear Breit–Wheeler process while maintaining a significant yield from the linear Breit–Wheeler process. The Bethe–Heitler process plays a secondary role in the considered system, so the majority of the positrons inside the channel are produced from light alone. Our results indicate that a structured target irradiated by two laser beams has the potential to be a versatile platform for future experimental studies of the Breit–Wheeler pair production processes, with the target parameters serving as control knobs.
K. Weichman, A. P. L. Robinson, M. Murakami, J. J. Santos, S. Fujioka, T. Toncian, J. P. Palastro, and A. Arefiev, "Progress in relativistic laser–plasma interaction with kilotesla-level applied magnetic fields", Physics of Plasmas 29, 053104 (2022).
We report on progress in the understanding of the effects of kilotesla-level applied magnetic fields on relativistic laser–plasma interactions. Ongoing advances in magnetic-field–generation techniques enable new and highly desirable phenomena, including magnetic-field–amplification platforms with reversible sign, focusing ion acceleration, and bulk-relativistic plasma heating. Building on recent advancements in laser–plasma interactions with applied magnetic fields, we introduce simple models for evaluating the effects of applied magnetic fields in magnetic-field amplification, sheath-based ion acceleration, and direct laser acceleration. These models indicate the feasibility of observing beneficial magnetic-field effects under experimentally relevant conditions and offer a starting point for future experimental design.
Y. He, I-L. Yeh, T. Blackburn, and A. Arefiev, "A single-laser scheme for observation of linear Breit-Wheeler electron-positron pair creation", New J. Phys. 23, 115005 (2021).
We show that a single laser pulse, traveling through a dense plasma, produces a population of MeV photons of sufficient density to generate a large number of electron-positron pairs via the linear Breit-Wheeler process. While it may be expected that the photons are emitted predominantly in the forward direction, parallel to the laser propagation, we find that a longitudinal plasma electric field drives the emission of photons in the backwards direction. This enables the collision of oppositely directed, MeV-level photons necessary to overcome the mass threshold for the linear Breit-Wheeler process. Our calculations predict the production of 107 electron-positron pairs, per shot, by a laser with peak intensity of just 3×1022 W/cm2. By using only a single laser pulse, the scheme sidesteps the practical difficulties associated with the multiple-laser schemes previously investigated.
L. Esnault, E. d'Humieres, A. Arefiev, and X. Ribeyre, "Electron-positron pair production in the collision of real photon beams with wide energy distributions", Plasma Phys. Control. Fusion 60, 125015 (2021).
The creation of an electron–positron pair in the collision of two real photons, namely the linear Breit–Wheeler process, has never been detected directly in the laboratory since its prediction in 1934 despite its fundamental importance in quantum electrodynamics and high energy astrophysics. In the last few years, several experimental setup have been proposed to observe this process in the laboratory, relying either on thermal radiation, Bremsstrahlung, linear or multiphoton inverse Compton scattering photons sources created by lasers or by the mean of a lepton collider coupled with lasers. In these propositions, the influence of the photons' energy distribution on the total number of produced pairs has been taken into account with an analytical model only for two of these cases. We hereafter develop a general and original, semi-analytical model to estimate the influence of the photons energy distribution on the total number of pairs produced by the collision of two such photon beams, and give optimum energy parameters for some of the proposed experimental configurations. Our results shows that the production of optimum Bremsstrahlung and linear inverse Compton sources are, only from energy distribution considerations, already reachable in today's facilities. Despite its less interesting energy distribution features for the linear Breit–Wheeler pair production, the photon sources generated via multiphoton inverse Compton scattering by the propagation of a laser in a micro-channel can also be interesting, thank to the high collision luminosity that could eventually be reached by such configurations. These results then gives important insights for the design of experiments intended to detect linear Breit–Wheeler produced positrons in the laboratory for the first time.
T. Wang, D. Blackman, K. Chin, and A. Arefiev, "Effects of simulation dimensionality on laser-driven electron acceleration and photon emission in hollow microchannel targets", Phys. Rev. E 104, 045206 (2021).
Using two-dimensional (2D) and three-dimensional (3D) kinetic simulations, we examine the impact of simulation dimensionality on the laser-driven electron acceleration and the emission of collimated γ-ray beams from hollow microchannel targets. We demonstrate that the dimensionality of the simulations considerably influences the results of electron acceleration and photon generation owing to the variation of laser phase velocity in different geometries. In a 3D simulation with a cylindrical geometry, the acceleration process of electrons terminates early due to the higher phase velocity of the propagating laser fields; in contrast, 2D simulations with planar geometry tend to have prolonged electron acceleration and thus produce much more energetic electrons. The photon beam generated in the 3D setup is found to be more diverged accompanied with a lower conversion efficiency. Our paper concludes that the 2D simulation can qualitatively reproduce the features in 3D simulation, but for quantitative evaluations and reliable predictions to facilitate experiment designs 3D modeling is strongly recommended.