arXiv subjects

Jiansheng Liu

Publications and source records attributed to Jiansheng Liu.

9 recordsLinked to original sources

arXiv2024

Transient chirp reconstruction of electron beam via tightly focused chirped laser pulse

Controlling the phase space of particle beams is essential for the generation of high-quality, ultrashort electron beams in plasma-based accelerators. Accurately diagnosing the transient energy chirp, which evolves rapidly at the onset of acceleration, presents a significant challenge. This paper introduces a novel method for reconstructing the transient energy chirp of ultrashort electron beams by employing tightly focused and chirped laser pulses. We investigate the conditions that enhance the modulation of electron-beam divergence and illustrate the reconstruction of transient chirp based on the intrinsic phase correlation of the modulated divergence as projected onto specific phase space coordinates. Additionally, we estimate the temporal delay between the laser and electron beam by applying a Fourier transform to the reconstructed divergence modulation in the frequency domain. This approach holds promise for optimizing accelerator performance and facilitates the probing of timing jitter in ultrafast electron diffraction with attosecond-level precision.

physics.plasm-ph↗

arXiv2024

Modulating Leidenfrost-like Prompt Jumping of Sessile Droplets on Microstructured Surfaces NPformat

The Leidenfrost effect, namely the levitation and hovering of liquid drops on hot solid surfaces, generally requires a sufficiently high substrate temperature to activate the intense liquid vaporization. Here we report the agile modulations of Leidenfrost-like prompt jumping of sessile water microdroplets on micropillared surfaces at a remarkably mitigated temperature. Compared to traditional Leidenfrost effect occurring above 230 °C, the fin-array-like micropillars enables Wenzel-state water microdroplets to levitate and jump off within 1.33 ms at an unprecedently low temperature of 130 °C by triggering the inertia-controlled growth of individual vapor bubbles at the droplet base. We demonstrate that droplet jumping, resulting from the momentum interactions between the expanding vapor bubble and the droplet, can be deftly modulated by simply tailoring the thermal boundary layer thickness via pillar heights, which acts to regulate the bubble expansion between the inertia-controlled mode and the heat-transfer-limited mode. Intriguingly, the two bubble growth modes give rise to distinct droplet jumping behaviors characterized by constant velocity and constant energy schemes, respectively. This strategy allows the facile purging of wetting liquid drops on rough or structured surfaces in a controlled manner, inspiring promising applications in rapid removal of fouling even settled in surface cavities.

physics.flu-dyn↗

arXiv2019

Polarization sensitive laser intensity inside femtosecond filament in air

Polarization dependence on clamping intensity inside femtosecond filament was experimentally measured in air. By tuning the laser pulse ellipse from linear polarization to circular polarization, the measured clamping intensity inside laser filament is gradually increased up to 1.7 times. The experimental results are in good agreement with the simulation results by solving the extended nonlinear Schrodinger equation (NLSE). The polarization sensitive clamping intensity inside filaments offers an important factor towards fully understanding the polarization related phenomenon observed so far.

physics.optics↗

arXiv2018

A new approach for rain gush formation associated with ionic wind

Based upon experimental observation in the laboratory, we propose that ionic wind from corona discharge inside a thundercloud would play an important role in producing a rain gush. A cyclic chain of events inside a super-saturated environment in a thundercloud is proposed, each event enhancing the successive ones until lightning occurs. These successive events are collision between snowflakes and rimers, charge separation, corona discharge, avalanche ionization, ionic wind originating from the positively and negatively charged masses of cloud, vortex motion and turbulence when mixed with the updraft, more collision, more charge separation, stronger corona discharge, and so on. Meanwhile, avalanche ionization would produce more CCN (cloud condensation nuclei) resulting in more precipitation and hence rimers formation in the super-saturated environment. More collision in the buoyant turbulence would lead to more fusion of droplets and the formation of larger rimers. The cyclic processes would repeat themselves until the electric field between the two oppositely charged masses of cloud was strong enough to induce a breakdown. The latter would create a sudden short circuit between the two charged masses of cloud neutralizing the charges. There would be no more ionic wind, hence, much less buoyant turbulence. The updraft alone would not be sufficiently strong to support larger rimers which would fall down 'suddenly' to the earth surface as a rain gush.

physics.ao-ph↗

arXiv2018

Laser guided ionic wind

We report on a method to experimentally generate ionic wind by coupling an external high voltage electric field with an intense femtosecond laser induced air plasma filament. The measured ionic wind velocity could be as strong as >4 m/s. It could be optimized by changing the applied electric field and the laser induced plasma channel. The experimental observation was qualitatively confirmed by a numerical simulation of spatial distribution of the electric field. This technique is robust and free from sharp metallic electrodes for coronas; it opens a way to optically generate ionic wind at a distance.

physics.plasm-ph↗

arXiv2017

Enhanced betatron radiation by steering a low-energy-spread electron beam in a deflected laser-driven plasma wiggler

Laser wakefield accelerators (LWFA) hold great potential to produce high-quality high-energy electron beams (e beams) and simultaneously bright x-ray sources via betatron radiation, which are very promising for pump-probe study in ultrafast science. However, in order to obtain a high-quality e beam, electron injection and acceleration should be carefully manipulated, where a large oscillation amplitude has to be avoided and thus the emitted x-ray yield is limited. Here, we report a new scheme to experimentally enhance betatron radiation significantly both in photon yield and photon energy by separating electron injection and acceleration from manipulation of the e-beam transverse oscillation in the wake via introducing a slanted thin plasma refraction slab. Particle-in-cell simulations indicate that the e-beam transverse oscillation amplitude can be increased by more than 10 folds, after being steered into the deflected laser-driven wakefield due to refraction at the slab's boundaries. Spectral broadening of the x-rays can be suppressed owing to the small variation in the peak energy of the low-energy-spread e beam in a plasma wiggler regime. We demonstrate that the high-quality e-beam generation, refracting and wiggling can act as a whole to realize the concurrence of monoenergetic e beam and bright x-rays in a compact LWFA.

physics.plasm-ph↗

arXiv2016

Snowfall induced by corona discharge

We demonstrated for the first time the condensation and precipitation (or snowfall) induced by a corona discharge inside a cloud chamber. Ionic wind was found to have played a more significant role than ions as extra Cloud Condensation Nuclei (CCN). 2.25 g of net snow enhancement was measured after applying a 30 kV corona discharge for 25 min. In comparison with another newly emerging femtosecond laser filamentation method, the snow precipitation induced by the corona discharge has about 4 orders of magnitude higher wall-plug efficiency under similar conditions.

physics.gen-ph↗

arXiv2015

Direct observation of laser guided corona discharges

Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. The high voltage corona discharge can be guided along laser plasma filament, and enhanced through the interaction with laser filaments. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This could be advantageous towards laser assisted leader development in the atmosphere.

physics.optics↗

arXiv2014

The Tunable Hybrid Surface Phonon and Plasmon Polariton Modes in Boron Nitride Nanotube and Graphene Monolayer Heterostructures

The hybrid modes incorporating surface phonon polariton (SPhP) modes in boron nitride nanotubes (BNNTs) and surface plasmon polariton (SPP) modes in graphene monolayers are theoretically studied. The combination of the 1D BNNTs and 2D graphene monolayer further improves the modal characteristics with electrical tunability. Superior to the graphene monolayers, the proposed heterostructures supports single mode transmission with lateral optical confinement. The modal characteristics can be shifted from SPP-like toward SPhP-like. Both the figure of merit and field enhancement of hybrid modes are improved over 3 times than those of BNNT SPhP modes, which may further enable sub-wavelength mid-infrared applications.

physics.optics↗