Laser-produced Plasma Channel Research Articles

Reduction of Electron Dephasing Rate by Bessel Function Laser Pulse Propagation in Underdense Plasma (April 2021)

In laser acceleration dynamics of the electron, the approximate value of the longitudinal component of the electric field has been considered in all analytical and numerical calculations. In this article, an exact analytical expression for the longitudinal component of the electric field in a spindle-shaped laser-produced plasma channel formed by Bessel laser pulse propagation is derived. To this end, first, the dimensions of the channel are obtained by balancing the ponderomotive and electrostatic forces acting on the plasma channel, and then an analytical expression for the longitudinal electric field of the channel is calculated. Finally, substituting the exact fields in the electron equation of motion, the dynamics of the electron inside the channel and also the electron energy gain are studied. The result of the numerical analysis shows that the real longitudinal component of the electric field of the channel changes the electron energy gain significantly. We also found that the longitudinal electric field of laser does not always counteract the transverse component of the field so that the electron can gain or lose energy from both of them simultaneously.

Nonlinear parametric resonance of relativistic electrons with a linearly polarized laser pulse in a plasma channel

The direct laser-acceleration mechanism, nonlinear parametric resonance, of relativistic electrons in a linearly polarized laser-produced plasma channel is examined by a self-consistent model including the relativistic laser dispersion in plasmas. Nonlinear parametric resonance can be excited, and the oscillation amplitude of electrons grows exponentially when the betatron frequency of electron motion varies roughly twice the natural frequency of the oscillator. It is shown analytically that the region of parametric resonance is defined by the self-similar parameter nenca0. The width of this region decreases with nenca0, but the energy gain and oscillation amplitude increases. In this regime, the electron transverse momentum grows faster than that in the linear classical resonance regime.

Brilliant petawatt gamma-ray pulse generation in quantum electrodynamic laser-plasma interaction

We show a new resonance acceleration scheme for generating ultradense relativistic electron bunches in helical motions and hence emitting brilliant vortical γ-ray pulses in the quantum electrodynamic (QED) regime of circularly-polarized (CP) laser-plasma interactions. Here the combined effects of the radiation reaction recoil force and the self-generated magnetic fields result in not only trapping of a great amount of electrons in laser-produced plasma channel, but also significant broadening of the resonance bandwidth between laser frequency and that of electron betatron oscillation in the channel, which eventually leads to formation of the ultradense electron bunch under resonant helical motion in CP laser fields. Three-dimensional PIC simulations show that a brilliant γ-ray pulse with unprecedented power of 6.7 PW and peak brightness of 1025 photons/s/mm2 /mrad2 /0.1% BW (at 15 MeV) is emitted at laser intensity of 1.9 × 1023 W/cm2.

Transient velocity distribution of laser-produced plasma in gaseous media

In this paper, we investigate the transient velocity distribution of laser-produced plasma (LPP) in gaseous media in the field-ionization regime. We derive the velocity distribution by matching the time-varying velocities of LPP with the reference velocity. In order to smooth the distribution functions, we propose a partition scheme to calculate the velocity, in which the time-varying velocity is contributed by two adjacent grids with different weighting factors. The mean kinetic energy is calculated based on the velocity distribution, which holds promise to determine the dynamics of LPP as initial conditions in further studies, for instance, of the evolution of LPP channel.

Chirped pulse amplification of femtosecond pulse sequences in a Ti: sapphire laser

An amplified femtosecond pulse sequence is generated in a multi-TW Ti: sapphire chirped pulse amplification system (JG-II facility). The pulse interval of the pulse sequence is 14.8 ns, corresponding to a frequency of 67.5 MHz. The compressed pulse sequence can reach 122 mJ in 19 independent pulses with a pulse width of about 60 fs. The energy of the pulses declines from 20 mJ to 0.5 mJ, corresponding to a peak power from 1011 W to 1010 W. The pulse sequence has important applications in lengthening the lifetime of the laser produced plasma channel in air and in microfabrication.

Effect of self focusing on the prolongation of laser produced plasma channel

AbstractA theoretical model for the prolongation of lifetime of a gaseous plasma channel formed by two pulse technique at laser intensities below the tunnel ionization threshold is developed. The first laser pulse ionizes the gas completely on the axis and partially off the axis, causing self-defocusing of the pulse. After the passage of the pulse, the plasma expands radially, creating an atom/ion density profile with a minimum on the axis. Partial recombination also sets in. As the second pulse arrives, after a time delay of less than the recombination time (~ns), the electrons get heated, and the recombination rate is slowed down. The second pulse self focuses, enhancing the heating rate and lengthening the lifetime of the plasma channel.

Dipolar-like antenna emission in the radiofrequency range by laser-produced plasma channels in air

Experimental evidence of a dipolar-like antenna emission in the radiofrequency range from a terawatt laser-produced plasma channel in air is, for the first time, obtained. The emitted frequencies exhibit resonances as a function of the plasma length. Possible applications for plasma fundamental parameter measurement, and the plasma heating approach, are discussed.

Effects of shock wave on laser‐induced discharge under a nonuniform DC electric field

AbstractLaboratory experiments and numerical simulations have been carried out to study the mechanisms of laser‐induced discharge under a nonuniform DC electric field as a basic research for the laser‐induced lightning. Plasma was produced between a rod–plane electrode gap. The electron density was measured via the Mach–Zehnder interferometer. The laser‐produced plasma channel serves as an extended rod electrode once the channel becomes a leader. The shock wave generated from the laser‐produced plasma has two effects. It produces a rarefied gas region in the gap, which further decreases the flashover voltage. On the other hand, stagnation at the surface of the rod electrode enhances the gas density and obstructs the leader formation. © 2001 Scripta Technica, Electr Eng Jpn, 137(1): 9–16, 2001

Recombination x-ray lasers of heliumlike nitrogen ions in a plasma waveguide

The laser-produced plasma channel may be a promising means of producing an efficient compact soft-x-ray laser. The plasma parameters in such a plasma waveguide are calculated with a self-similar model. It is shown that nonequilibrium underdense plasmas and candidate ions for recombination laser schemes can be obtained. As an example, the laser gains of the transition 1s3d–1s2p of He-like N ions are calculated for given pumping energies and initial gas densities.

Guiding of electrical discharges under atmospheric air by ultraviolet laser-produced plasma channel

Guiding and triggering of electrical discharges in 0.34 m air gaps by an ultraviolet laser-produced plasma have been demonstrated. An ultraviolet laser pulse (KrF laser, wavelength=248 nm, energy=750 mJ) produced the plasma channel by a focusing lens with a focal length of 1 m. This plasma channel forms a straight discharge channel along the laser beam (guiding ability) and reduces the flashover voltage (triggering ability). We measured the guiding and triggering ability of the laser-produced plasma channel and estimated the state of the plasma channel by calculating the rate equations. From these experiments and simulations, we found that the guiding ability of the ion plasma is mainly due to the formation of the leader from the plasma channel by enhancement of the local fields. The guiding ability of the electron-ion plasma is different from that of the ion plasma.

Application of a plasma waveguide to soft-x-ray lasers

A recently developed laser-produced plasma channel is shown to be a promising means to produce an efficient, compact soft-x-ray laser. The channel provides a route for efficient high-power laser pumping through optical waveguiding of the pump. The channel also acts as a waveguide for generated soft x rays, as it has wavelength-independent mode structure. It is shown that channel creation and guided laser pulses of moderate duration and energy can be highly effective in producing nonequilibrium gas density plasmas and candidate ions for collisional and recombination laser schemes. The nonequilibrium behavior of these plasmas can be exploited to generate substantial population inversions.