arXiv subjects

B. Qiao

Publications and source records attributed to B. Qiao.

At least 19 recordsLinked to original sources

arXiv2024

Laboratory investigation of the interaction between the jet and background, from collisionless to strong collision

The interaction between the supersonic jet and background can influence the process of star formation, and this interaction also results in a change of the jet's velocity, direction and density through shock waves. However, due to the limitations of current astronomical facilities, the fine shock structure and the detailed interaction process still remain unclear. Here we investigate the plasma dynamics under different collision states through laser-driven experiments. A double-shock structure is shown in the optical diagnosis for collision case, but the integrated self-emitting X-ray characteristic is different. For solid plastic hemisphere obstacle, two-layer shock emission is observed, and for the relatively low-density laser-driven plasma core, only one shock emission is shown. And the plasma jets are deflected by $50 ^{\circ}$ through the interaction with the high-density background in both cases. For collisionless cases, filament structures are observed, and the mean width of filaments is roughly the same as the ion skin depth. High-energy electrons are observed in all interaction cases. We present the detailed process of the shock formation and filament instability through 2D/3D hydrodynamic simulations and particle-in-cell simulations respectively. Our results can also be applied to explain the shock structure in the Herbig-Haro (HH) 110/270 system, and the experiments indicate that the impact point may be pushed into the inside part of the cloud.

physics.plasm-ph↗

arXiv2023

Vortex $γ$ photon generation via spin-to-orbital angular momentum transfer in nonlinear Compton scattering

Vortex $γ$ photons with intrinsic orbital angular momenta (OAM) possess a wealth of applications in various fields, e.g.-strong-laser physics, nuclear physics, particle physics and astrophysics-yet their generation remains unsettled. In this work, we investigate the generation of vortex $γ$ photons via nonlinear Compton scattering of ultrarelativistic electrons in a circularly polarized laser pulse. We develop a quantum electrodynamics scattering theory that explicitly addresses the multiphoton absorption and the angular momentum transfer mechanism. In pulsed laser fields, we unveil the vortex phase structure of the scattering matrix element, discuss how the vortex phase could be transferred to the radiated photon, and derive the radiation rate of the vortex $γ$ photon. We numerically examine the energy spectra and beam characteristics of the radiation, while also investigating the influence of finite laser pulses on the angular momentum and energy distribution of the emitted vortex $γ$ photons.

hep-ph↗

arXiv2022

Electron and ion acceleration from femtosecond laser-plasma peeler scheme

Using three-dimensional particle-in-cell simulations, we further investigate the electron and ion acceleration from femtosecond laser-plasma peeler scheme which was proposed in our recent paper (Shen et al 2021 Phys. Rev. X 11 041002). In addition to the standard setup where a laser pulse impinges on an edge of a single tape target, two new variants of the target, i.e., a parallel tape and a cross tape target, were proposed, where strong surface plasma waves can also be efficiently excited at the front edges of the target. By using a tabletop 200 TW-class laser pulse, we observe generation of high-flux, well-collimated, superponderomotive electrons. More importantly, quasimonoenergetic proton beams can always be obtained in all the three setups, while with the single tape case, the obtained proton beam has the highest peak energy and narrowest spectrum.

physics.plasm-ph↗

arXiv2022

A Nuclear-Based Diagnostic Scheme for Nonthermal Ion Spectrum in High Energy Density Plasmas Experiments

The nuclear reactions in a plasma system with energy distribution deviated from Maxwellian are proved to have some unique characteristics including those in their product energy spectrum. Based on this, a new nuclear diagnostic scheme for measuring the nonthermal ion energy spectrum in high-energy-density plasmas is proposed, where the effective temperature and spectral peak of the nonthermal ion energy spectrum are uniquely determined by the spectral width and spectral peak of the product energy spectrum. Then, taking the laser-driven magnetic reconnection experiment as an example, according to the particle-in-cell (PIC) simulation results coupled with the proton-boron (pB) fusion reaction, the pB reaction rate is increased by 4 orders of magnitude; meanwhile, the product spectral peak and spectral width are shifted towards higher energy, deviating from the predictions of the thermal equilibrium assumption, both of which are on account of the accelerated and heated suprathermal protons in magnetic reconnection. Furthermore, analyzing a series of simulation results, the new product spectrum analysis approach suitable for the parameter range of laser-driven magnetic reconnection is found.

physics.plasm-ph↗

arXiv2022

Laboratory observation of plasmoid-dominated magnetic reconnection in hybrid collisional-collisionless regime

Magnetic reconnection, breaking and reorganization of magnetic field topology, is a fundamental process for rapid release of magnetic energy into plasma particles that occurs pervasively throughout the universe. In most natural circumstances, the plasma properties on either side of the reconnection layer are asymmetric, in particular for the collision rates that are associated with a combination of density and temperature and critically determine the reconnection mechanism. To date, all laboratory experiments on magnetic reconnections have been limited to purely collisional or collisionless regimes. Here, we report a well-designed experimental investigation on asymmetric magnetic reconnections in a novel hybrid collisional-collisionless regime by interactions between laser-ablated Cu and CH plasmas. We show that the growth rate of the tearing instability in such a hybrid regime is still extremely large, resulting in rapid formation of multiple plasmoids, lower than that in the purely collisionless regime but much higher than the collisional case. In addition, we, for the first time, directly observe the topology evolutions of the whole process of plasmoid-dominated magnetic reconnections by using highly-resolved proton radiography.

physics.plasm-ph↗

arXiv2020

Hybrid-drive pressure suppressing implosion instabilities and offering nonstagnation hotspot ignition with low convergence ratio for high-gain inertial fusion

In laser-drive ICF, hybrid drive (HD) combined direct drive (DD) and indirect drive (ID) offers a smoothed HD pressure $P_{HD}$, far higher than the ablation pressure in ID and DD, to suppress hydrodynamic instabilities. In this letter, simulations of a new robust HD ignition target show that maximal HD pressure as high as $P_{HD} \sim$ 650 Mbar driven by a novel "bulldozer" effect is achieved, resulting in nonstagnation hotspot ignition at the convergence ratio $C_r \sim $23, and finally, fusion energy gain $\sim$ 10 in total laser energy = 1.42 MJ. Two-dimensional simulations have confirmed that hydrodynamic instabilities are suppressed. A well-fitted scale of maximal HD pressure $P_{HD}$ (Mbar)= $BE_{DD}^{1/4} T_r$ is found from simulations of different targets and laser energies as long as $T_r> 160$ eV, where B is the constant depending on ablator materials, $E_{DD}$ in kJ is DD laser energy and $T_r$ in 100 eV is radiation temperature depending on ID laser energy $E_{ID}$. $P_{HD}\geq$ 450 Mbar is requested for hotspot ignition. This scale from "bulldozer" effect is also available as $E_{DD}$ is reduced to kJ. Experiments have verified $P_{HD}$ about 3.5 times radiation ablation pressure for CH ablator using $E_{ID}=43$ kJ ($T_r \simeq$200 eV) and $E_{DD}$=3.6 kJ, also shown that both backscattering fraction and hot-electron energy fraction for DD laser intensity $\sim 1.8 \times 10^{15} {\rm w\cdot cm^{-2}}$ are about a third of the traditional DD laser-plasma interaction

physics.plasm-ph↗

arXiv2020

Synergistic Longitudinal Acceleration and Transverse Oscillation in High-order Harmonic Generation

We propose and demonstrate that relativistic harmonics with a slowly decaying power law are generated from a femtosecond lase pulse incident parallel to a micro-scale overdense plasma. It is shown that due to the excitation of a strong surface wave, dense electron nanobunches are continuously accelerated forward while oscillating in the transverse laser field. Even around the stationary phase point, relativistic gamma factors of the nanobunches increase considerably, leading to a much stronger attosecond burst, compared to the case with constant gamma. Our two-dimensional particle-in-cell simulations and analytical theory show that this synergistic function promises a power-law harmonic spectrum $I_n/I_0 = n^{-1}$. This is much flatter than the other well-known radiation mechanisms and paves the way to unprecedentedly large energy attosecond pulses.

physics.plasm-ph↗

arXiv2020

Monoenergetic High-energy Ion Source via Femtosecond Laser Incident Parallel to a Microplate

Using fully three-dimensional particle-in-cell simulations, we show that readily available femtosecond laser systems can stably generate proton beams with hundred MeV energy and low spread at $\sim1\%$ level by parallel irradiation of a tens of micrometers long plasma plate. As the laser pulse sweeps along the plate, it drags out a huge charge ($\sim$100 nC) of collimated energetic electrons and accelerates them along the plate surface to superponderomotive energies. When this dense electron current arrives at the rear end of the plate, it induces a strong electrostatic field. Due to the excessive space charge of electrons, the longitudinal field becomes bunching while the transverse field is focusing. Together, this leads to a highly monoenergetic energy spectrum and much higher proton energy as compared to simulation results from typical target normal sheath acceleration and radiation pressure acceleration at the same laser parameters.

physics.plasm-ph↗

arXiv2020

Giant isolated attosecond pulses from two-color laser plasma interactions

A new regime in the interaction of a two-colour ($ω$,$2ω$) laser with a nanometre-scale foil is identified, resulting in the emission of extremely intense, isolated attosecond pulses - even in the case of multi-cycle lasers. For foils irradiated by lasers exceeding the blow-out field strength (i.e. capable of fully separating electrons from the ion background), the addition of a second harmonic field results in the stabilization of the foil up to the blow-out intensity. This is then followed by a sharp transition to transparency that essentially occurs in a single optical cycle. During the transition cycle, a dense, nanometre-scale electron bunch is accelerated to relativistic velocities and emits a single, strong attosecond pulse with a peak intensity approaching that of the laser field.

physics.plasm-ph↗

arXiv2019

Simulating the external magnetic field in short-pulse intense laser-plasma interaction

Imposing an external magnetic field in short-pulse intense laser-plasma interaction is of broad scientific interest in related plasma research areas. We propose a simple method using a virtual current layer by introducing an extra current density term to simulate the external magnetic field, and demonstrate it with three-dimensional particle-in-cell simulations. The field distribution and its evolution in sub-picosecond time scale are obtained. The magnetization process takes a much longer time than that of laser-plasma interaction due to plasma diamagnetism arising from collective response. The long-time evolution of magnetic diffusion and diamagnetic current can be predicted based on a simplified analytic model in combination with simulations.

physics.plasm-ph↗

arXiv2018

Direction and divergence control of laser-driven energetic proton beam using a disk-solenoid target

A scheme for controlling the direction of energetic proton beam driven by intense laser pulse is proposed. Simulations show that a precisely directed and collimated proton bunch can be produced by a sub-picosecond laser pulse interacting with a target consisting of a thin solid-density disk foil with a solenoid coil attached to its back at the desired angle. It is found that two partially overlapping sheath fields are induced. As a result, the accelerated protons are directed parallel to the axis of the solenoid, and their spread angle is also reduced by the overlapping sheath fields. The proton properties can thus be controlled by manipulating the solenoid parameters. Such highly directional and collimated energetic protons are useful in the high-energy-density as well as medical sciences.

physics.plasm-ph↗

arXiv2018

The baryon loading effect on relativistic astrophysical jet transport in the interstellar medium

The composition of the astrophysical relativistic jets remains uncertain. By kinetic particle-in-cell simulations, we show that the baryon component in the jet, or the so-called baryon loading effect (BLE), heavily affects relativistic jets transport dynamics in the interstellar medium. On the one hand, with the BLE, relativistic jets can transport in a much longer distance, because jet electrons draw a significant amount of energy from jet baryons via the Buneman-induced electrostatic waves and the Weibel-mediated collisionless shock; on the other hand, the jet electron phase space distribution may transform from a bottom-wide-single-peak structure to a center-wide-multiple-peak one by increasing the BLE, which largely influences the observed jet morphology. Implications for related astrophysical studies are also discussed.

physics.plasm-ph↗

arXiv2018

Transport of relativistic jet in the magnetized intergalactic medium

The kinetic effects of magnetic fields on the transport of relativistic jet in the intergalactic medium remain uncertain, especially for their perpendicular component. By particle-in-cell simulations, we find that when only jet electrons are fully magnetized, they are directly deflected by the magnetic field, but jet protons are mainly dragged by collective charge-separation electric field. However, when both electrons and protons are fully magnetized, the contrary is the case. Their balance tremendously distorts the jet density and electromagnetic fields, leading to enormous energy exchange between different species and fields. As a result, the electron spectrum energy distribution (SED) gets reshaped and the power law slope of the SED decreases as the magnetic field strength increases. In other words, we may infer that magnetic fields around the relativistic jet play a crucial role in shaping the observed SED.

physics.plasm-ph↗

arXiv2018

Scaling Laws of Ion Acceleration in Ultrathin Foils Driven by Laser Radiation Pressure

Scaling laws of ion acceleration in ultrathin foils driven by radiation pressure of intense laser pulses are investigated by theoretical analysis and two-dimensional particle-in-cell simulations. Considering the instabilities are inevitable during laser plasma interaction, the maximum energy of ions should have two contributions: the bulk acceleration driven by radiation pressure and the sheath acceleration in the moving foil reference induced by hot electrons. A theoretical model is proposed to quantitatively explain the results that the cutoff energy and energy spread are larger than the predictions of "light sail" model, observed in simulations and experiments for a large range of laser and target parameters. Scaling laws derived from this model and supported by the simulation results are verified by the previous experiments.

physics.plasm-ph↗

arXiv2018

Generation of ten kilotesla longitudinal magnetic fields in ultraintense laser-solenoid target interactions

Production of the huge longitudinal magnetic fields by using an ultraintense laser pulse irradiating a solenoid target is considered. Through three-dimensional particle-in-cell simulations, it is shown that the longitudinal magnetic field up to ten kilotesla can be observed in the ultraintense laser-solenoid target interactions. The finding is associated with both fast and return electron currents in the solenoid target. The huge longitudinal magnetic field is of interest for a number of important applications, which include controlling the divergence of laser-driven energetic particles for medical treatment, fast-ignition in inertial fusion, etc., as an example, the well focused and confined directional electron beams are realized by using the solenoid target.

physics.plasm-ph↗

arXiv2018

Multidimensional effects on proton acceleration using high-power intense laser pulses

Dimensional effects in particle-in-cell (PIC) simulation of target normal sheath acceleration (TNSA) of protons are considered. As the spatial divergence of the laser-accelerated hot sheath electrons and the resulting space-charge electric field on the target backside depend on the spatial dimension, the maximum energy of the accelerated protons obtained from three-dimensional (3D) simulations is usually much less that from two-dimensional (2D) simulations. By closely examining the TNSA of protons in 2D and 3D PIC simulations, we deduce an empirical ratio between the maximum proton energies obtained from the 2D and 3D simulations. This ratio may be useful for estimating the maximum proton energy in realistic (3D) TNSA from the results of the corresponding 2D simulation. It is also shown that the scaling law also applies to TNSA from structured targets.

physics.plasm-ph↗

arXiv2017

Injection dynamics of direct-laser accelerated electrons in a relativistic transparency regime

The dynamics of electron injection in the direct laser acceleration (DLA) regime was investigated by means of three-dimensional particle-in-cell simulations and theoretical analysis. It is shown that when an ultra-intense laser pulse propagates into a near-critical density or relativistically transparent plasma, the longitudinal charge-separation electric field excites an ion wave. The ion wave modulates the local electric field and acts as a set of potential wells to guide the electrons, located on the edge of the plasma channel, to the central region, where the DLA takes place later on. In addition, it is pointed out that the self-generated azimuthal magnetic fields tend to suppress the injection process of electrons by deflecting them away from the laser field region. Understanding these physical processes paves the way for further optimizing the properties of direct-laser accelerated electron beams and the associated X/gamma-ray sources.

physics.plasm-ph↗

arXiv2016

Radiation reaction induced spiral attractors in ultra-intense colliding laser beams

The radiation reaction effects on electron dynamics in counter-propagating circularly polarized laser beams are investigated through the linearization theorem and the results are in great agreement with numeric solutions. For the first time, the properties of fixed points in electron phase-space were analyzed with linear stability theory, showing that center nodes will become attractors if the classical radiation reaction is considered. Electron dynamics are significantly affected by the properties of the fixed points and the electron phase-space densities are found to be increasing exponentially near the attractors. The density growth rates are derived theoretically and further verified by particle-in-cell simulations, which can be detected in experiments to explore the effects of radiation reaction qualitatively. The attractor can also facilitate to realize a series of nanometer-scaled flying electron slices via adjusting the colliding laser frequencies.

physics.plasm-ph↗