Fast electrons collimating and focusing by an ultraintense laser interacting with a high density layers

The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate and focus electron beams to smaller sizes. The collimation reasons are analyzed by the quasi-static magnetic fields generation inside the beam collimator with HDL. It is found that the energy conversion efficiency is increased by a factor of 2.2 in this new scheme in comparison with the that without HDL. Such a target structure has potential for design flexibility and prevents inefficiencies in important applications such as fast ignition, etc.

Effects of laser waveform on the generation of fast electrons in laser–solid interactions

In the scheme of fast ignition of inertial confinement fusion,the fuel temperature mainly relies on fast electrons,which act as an energy carrier,transferring the laser energy to the fuel.Both conversion efficiency from the laser to the fast electron and the energy spectrum of the fast electron are essentially important to achieve highly effective heating.In this study,a two-dimensional particle in cell simulation is applied to study the generation of fast electrons from solid-density plasmas with different laser waveforms.The results have shown that the slope of the rising edge has a significant effect on fast electron generation and energy absorption.For the negative skew pulse with a relatively slow rising edge,the J×B mechanism can most effectively accelerate the electrons.The overall absorption efficiency of the laser energy is optimized,and the fast electron yield in the middle-and low-energy range is also improved.

Experimental study on fast electron generation during internal crash

Hard x-ray(HXR)burst is found during internal crash in the flat top current stage of experimental advanced superconducting tokamak(EAST)discharges and it is caused by fast electrons.The generated electrons during internal crashes may be an operational safety issue in advanced tokamaks.During an internal crash,locations of fast electron generation from HXR evolution agree with areas of magnetic reconnection from soft x-ray(SXR)tomographic reconstruction.Further statistical analyses show a 27μs time difference between SXR crashes and HXR bursts,and the agreement between time broadening of HXR bursts and estimated characteristic time of magnetic reconnection in EAST.The magnetic reconnections during internal crash are proved to generate fast electrons,by both spatial and temporal agreements.

Study of the fast electron behavior in electron cyclotron current driven plasma on J-TEXT

In J-TEXT tokamak,fast electron bremsstrahlung diagnostic with 9 chords equipped with multichannel analyzer enables detailed studies of the generation and transport of fast electrons.The spatial profiles and energy spectrum of the fast electrons have been measured in two ECCD cases with either on-axis or off-axis injection,and the profiles processed by Abel-inversion are consistent with the calculated power deposition locations.Moreover,it is observed that the energy of fast electrons increases rapidly after turning off the ECCD,which may be attributed to the acceleration by the recovered loop voltage at low electron density.

Theoretical simulation of high-voltage discharge with runaway electrons in sulfur hexafluoride at atmospheric pressure

The results of theoretical simulation of runaway electron generation in high-pressure pulsed gas discharge with inhomogeneous electric field are presented.Hydrodynamic and kinetic approaches are used simultaneously to describe the dynamics of different components of low-temperature discharge plasma.Breakdown of coaxial diode occurs in the form of a dense plasma region expanding from the cathode.On this background there is a formation of runaway electrons that are initiated by the ensemble of plasma electrons generated in the place locally enhanced electric field in front of dense plasma.It is shown that the power spectrum of fast electrons in the discharge contains electron group with the so-called“anomalous”energy.

Sn-doped BiOCl nanosheet with synergistic H^(+)/Zn^(2+)co-insertion for“rocking chair”zinc-ion battery

The development of insertion-type anodes is the key to designing“rocking chair”zinc-ion batteries.However,there is rare report on high mass loading anode with high performances.Here,{001}-oriented Bi OCl nanosheets with Sn doping are proposed as a promising insertion-type anode.The designs of cross-linked CNTs conductive network,{001}-oriented nanosheet,and Sn doping significantly enhance ion/electron transport,proved via experimental tests and theoretical calculations(density of states and diffusion barrier).The H^(+)/Zn^(2+)synergistic co-insertion mechanism is proved via ex situ XRD,Raman,XPS,and SEM tests.Accordingly,this optimized electrode delivers a high reversible capacity of 194 m A h g^(-1)at 0.1 A g^(-1)with a voltage of≈0.37 V and an impressive cyclability with 128 m A h g^(-1)over 2500 cycles at 1 A g^(-1).It also shows satisfactory performances at an ultrahigh mass loading of 10 mg cm^(-2).Moreover,the Sn-Bi OCl//MnO_(2)full cell displays a reversible capacity of 85 m A h g^(-1)at 0.2 A g^(-1)during cyclic test.

Manipulation and optimization of electron transport by nanopore array targets

The transport of sub-picosecond laser-driven fast electrons in nanopore array targets is studied.Attributed to the generation of micro-structured magnetic fields,most fast electron beams are proven to be effectively guided and restricted during the propagation.Different transport patterns of fast electrons in the targets are observed in experiments and reproduced by particle-in-cell simulations,representing two components:initially collimated low-energy electrons in the center and high-energy scattering electrons turning into surrounding annular beams.The critical energy for confined electrons is deduced theoretically.The electron guidance and confinement by the nano-structured targets offer a technological approach to manipulate and optimize the fast electron transport by properly modulating pulse parameters and target design,showing great potential in many applications including ion acceleration,microfocus x-ray sources and inertial confinement fusion.

Filling Ti_(3)C_(2)T_(x)nanosheets into melamine foam towards a highly compressible all-in-one supercapacitor

The development of compressible supercapacitors strongly relies on the design of electrode materials combining superior compressibility,high conductivity with the stable electrochemical cycling performance.In this work,we report a facile yet scalable strategy to construct a highly compressible supercapacitor by integrating the current collector,active materials and the separator into one device.We use the highly compressive melamine foam(MF)as scaffold and the Ti_(3)C_(2)T_(x)nanosheets as the active materials.Filling the few-layer Ti_(3)C_(2)T_(x)nanosheets into the skeleton of MF by capillary force followed by freeze-drying yields the MF/Ti_(3)C_(2)T_(x)composite with superior structural integrity that can be compressed at a large strain of 50%for 100 cycles.The electrochemical performances of the all-in-one supercapacitor were systematically investigated under diverse compression strains.The improved conductivity and reduced ion diffusion length allow the all-in-one supercapacitor to exhibit fast ion and electron kinetics even at high strain of 60%,delivering a maximal volumetric specific energy of 0.37 mWh∙cm^(-3)at power density of 0.42 mW∙cm^(-3)and extraordinary cycling performance during the 2,500 compression cycles.