Terahertz-driven positron acceleration assisted by ultra-intense lasers.

Generation and acceleration of energetic positrons based on laser plasma have attracted intense attention due to their potential applications in medical physics, high energy physics, astrophysics and nuclear physics. However, such compact positron sources face a series of challenges including the beam dispersion, dephasing and unstability. Here, we propose a scheme that couples the all-optical generation of electron-positron pairs and rapid acceleration of copious positrons in the terahertz (THz) field.

Ultra-intense laser field amplification from a petawatt-class laser focusing in moderate density plasma.

The rapid development of laser technologies promises a significant growth of peak laser intensity from 10 W/cm to >10 W/cm, allowing the experimental studies of strong field quantum-electrodynamics physics and laser nuclear physics. Here, we propose a method to realize the ultra-intense laser field amplification of petawatt-class laser pulse in moderate density plasma via relativistic self-focusing and tapered-channel focusing. Three-dimensional particle-in-cell simulations demonstrate that almost an order of magnitude enhancement of laser intensity is possible even though the γ-ray radiation results in massive laser energy loss.

Ultra-brilliant GeV betatronlike radiation from energetic electrons oscillating in frequency-downshifted laser pulses.

Electrons can be accelerated to GeV energies with high collimation via laser wakefield acceleration in the bubble regime and emit bright betatron radiation in a table-top size. However, the radiation brightness is usually limited to the third-generation synchrotron radiation facilities operating at similar photon energies. Using a two-stage plasma configuration, we propose a novel scheme for generating betatronlike radiation with an extremely high brilliance.

Betatron radiation polarization control by using an off-axis ionization injection in a laser wakefield acceleration.

Tunable X-ray sources from a laser-driven wakefield have wide applications. However, due to the difficulty of electron dynamics control, currently the tunability of laser wakefield-based X-ray sources is still difficult. By using three-dimensional particle-in-cell simulations, we propose a scheme to realize controllable electron dynamics and X-ray radiation.

Copious positron production by femto-second laser via absorption enhancement in a microstructured surface target.

Laser-driven positron production is expected to provide a non-radioactive, controllable, radiation tunable positron source in laboratories. We propose a novel approach of positron production by using a femto-second laser irradiating a microstructured surface target combined with a high-Z converter. By numerical simulations, it is shown that both the temperature and the maximum kinetic energy of electrons can be greatly enhanced by using a microstructured surface target instead of a planar target.

Dense relativistic electron mirrors from a Laguerre-Gaussian laser-irradiated micro-droplet.

We investigate dense relativistic electron mirror generation from a micro-droplet driven by circularly polarized Laguerre-Gaussian lasers. The surface electrons are expelled from the droplet by the laser's radial electric field and evolve into dense sheets after leaving the droplet. These electrons are trapped in the potential well of the laser's transverse ponderomotive force and are steadily accelerated to about 100 MeV by the longitudinal electric field.

Attosecond electron bunches from a nanofiber driven by Laguerre-Gaussian laser pulses.

Generation of attosecond bunches of energetic electrons offers significant potential from ultrafast physics to novel radiation sources. However, it is still a great challenge to stably produce such electron beams with lasers, since the typical subfemtosecond electron bunches from laser-plasma interactions either carry low beam charge, or propagate for only several tens of femtoseconds. Here we propose an all-optical scheme for generating dense attosecond electron bunches via the interaction of an intense Laguerre-Gaussian (LG) laser pulse with a nanofiber.

Ultra-bright γ-ray emission and dense positron production from two laser-driven colliding foils.

Matter can be transferred into energy and the opposite transformation is also possible by use of high-power lasers. A laser pulse in plasma can convert its energy into γ-rays and then e e pairs via the multi-photon Breit-Wheeler process. Production of dense positrons at GeV energies is very challenging since extremely high laser intensity ~10 Wcm is required.

Ultra-bright γ-ray flashes and dense attosecond positron bunches from two counter-propagating laser pulses irradiating a micro-wire target.

We propose a novel scheme to generate ultra-bright ultra-short γ-ray flashes and high-energy-density attosecond positron bunches by using multi-dimensional particle-in-cell simulations with quantum electrodynamics effects incorporated. By irradiating a 10 PW laser pulse with an intensity of 10 W/cm onto a micro-wire target, surface electrons are dragged-out of the micro-wire and are effectively accelerated to several GeV energies by the laser ponderomotive force, forming relativistic attosecond electron bunches. When these electrons interact with the probe pulse from the other side, ultra-short γ-ray flashes are emitted with an ultra-high peak brightness of 1.

Directional enhancement of selected high-order-harmonics from intense laser irradiated blazed grating targets.

Relativistically intense laser solid target interaction has been proved to be a promising way to generate high-order harmonics, which can be used to diagnose ultrafast phenomena. However, their emission direction and spectra still lack tunability. Based upon two-dimensional particle-in-cell simulations, we show that directional enhancement of selected high-order-harmonics can be realized using blazed grating targets.

All-optical bright γ-ray and dense positron source by laser driven plasmas-filled cone.

An all-optical scheme for bright γ-rays and dense ee pair source is proposed by irradiating a 10 W/cm laser onto a near-critical-density plasmas filled Al cone. Two-dimensional (2D) QED particle-in-cell (PIC) simulations show that, a dense electron bunch is confined in the laser field due to the radiation reaction and the trapped electrons oscillate transversely, emitting bright γ-rays forward in two ways: (1) nonlinear Compton scattering due to oscillation of electrons in the laser field, and (2) Compton backwardscattering resulting from the bunch colliding with the reflected laser by the cone tip. Finally, the multi-photon Breit-Wheeler process is initiated, producing abundant ee pairs with a density of ∼ 10m.

[Experimental research on remote sensing spectrometer's instrument response function].

Remote sensing spectrometers were widely used in the fields such as spectral measure and trace gas supervision in atmosphere. The instrument response functions should be measured to eliminate the effect of the spectrometer. The instrument response functions of MCT detector and InSb detector in BLUKER TENSOR 37 passive FTIR spectrometer were measured in the present paper.