共查询到20条相似文献,搜索用时 46 毫秒
1.
S. A. Aseev B. N. Mironov V. G. Minogin S. V. Chekalin V. S. Letokhov 《JETP Letters》2009,90(1):13-17
A method based on an original electron microscope created for investigating photoelectron beams is presented. It ensures a
nanometer spatial resolution and picosecond time resolution. Electrons appearing when a metal needle is irradiated by femtosecond
laser pulses are transmitted through a dielectric microcapillary and are subjected to a ponderomotive potential created by
femtosecond laser radiation focused near the capillary tip. The position-sensitive detection scheme allows for the detection
of the spatial profile of a photo-electron beam with a magnification of K ≅ 4 × 104. The time structure of the photoelectron beam is visualized by scanning the delay time between laser pulses irradiating the
needle and a laser pulse focused near the capillary tip. 相似文献
2.
基于扭曲向列型液晶空间光调制器的旋光特性, 根据空间光调制器所加电压和加载相位与旋光角度的对应关系, 设计了可以生成多种涡旋矢量光的通用光路. 利用该原理和光路系统, 在实验上生成了多种携带轴对称相位的矢量光以及图案般复杂的矢量光, 观察和检测了它们的偏振特性, 获得了较好的实验结果. 并且模拟了具有涡旋相位的矢量光的紧聚焦场, 分析了它们的紧聚焦特性. 由于这种生成矢量光的方法光路装置简单、操作容易, 产生矢量光的过程中几乎不损失能量, 并且不存在聚焦过程, 因此在如强激光矢量光束与物质相互作用、激光加速等方面具有重要的应用潜力. 相似文献
3.
Collective properties of a relativistic electron beam injected into a high intensity optical lattice
I. A. Andriyash Ph. Balcou V. T. Tikhonchuk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):533-540
Behaviour of a relativistic electron bunch, injected and trapped in a high intensity
optical lattice resulting from the interference of two laser beams is studied. The optical
lattice modifies the phase space distribution of the electron bunch due to the trapping
and compression of the electrons by a ponderomotive force. High-frequency longitudinal
beam eigenmodes of the trapped electron bunch are described in the framework of fluid and
kinetic models. Such beam oscillations are expected to play a pivotal role in a stimulated
Raman scattering of laser beams on the electrons. 相似文献
4.
A phase-only spatial light modulator is used in conjunction with a spatial filter to provide independent control of the phase and amplitude of a laser beam. Continuous amplitude modulation of the beam is achieved with a resolution relevant to beam shaping of high-energy laser beams. Amplitude beam correction in a closed loop is demonstrated. 相似文献
5.
Fengnian Lü 《中国光学快报(英文版)》2006,4(10)
Image relaying is presented as a technique for aligning beams onto mm-sized target of high power laser. On the basis of summarizing the preceeding work on the near-field image relaying of multiple spatial filters,the far-filed image relaying is suggested firstly. The near-field and far-field image relaying properties of multiple spatial filters in laser beams automatic alignment system are analyzed. A geometrical optics approach and an ABCD ray matrix theory are used throughout. The reasonable and optimum scheme for automatically aligning multi-pass beam paths is presented and demonstrated on the multi-pass amplifier system of the SG-Ⅲ prototype. 相似文献
6.
Y.W. Chan 《Physics letters. A》1980,76(1):25-27
On the basis of Palmer's criterion for the self-bunching effect of a relativistic electron beam in a helical magnetic field, it is shown that coherent X-rays can be generated from relativistic electron beams backscattered by laser beams without the need of any resonant cavity. 相似文献
7.
A free-electron laser (FEL) operating in the quantum regime can provide a compact and monochromatic x-ray source. Here we present the complete quantum model for a FEL with a laser wiggler in three spatial dimensions, based on a discrete Wigner-function formalism taking into account the longitudinal momentum quantization. The model describes the complete spatial and temporal evolution of the electron and radiation beams, including diffraction, propagation, laser wiggler profile and emittance effects. The transverse motion is described in a suitable classical limit, since the typical beam emittance values are much larger than the Compton wavelength quantum limit. In this approximation we derive an equation for the Wigner function which reduces to the three-dimensional Vlasov equation in the complete classical limit. Preliminary numerical results are presented together with parameters for a possible experiment. 相似文献
8.
Miroslav Pardy 《International Journal of Theoretical Physics》2006,45(3):647-659
We find the solutions of the Dirac equation for two plane waves (laser beams) and we determine the modified Compton formula for the scattering of two photons on an electron. The practical meaning of the two laser beams is, that two laser beams impinging on a target which is constituted from material in the form a foam, can replace 100–200 laser beams impinging on a normal target and it means that the nuclear fusion with two laser beams is realistic in combination with the thermonuclear reactor such as ITER. 相似文献
9.
Electron acceleration in the inverse free electron laser (IFEL) with a helical wiggler in the presence of ion-channel guiding and axial magnetic field is investigated in this article. The effects of tapering wiggler amplitude and axial magnetic field are calculated for the electron acceleration. In free electron lasers, electron beams lose energy through radiation while in IFEL electron beams gain energy from the laser. The equation of electron motion and the equation of energy exchange between a single electron and electromagnetic waves are derived and then solved numerically using the fourth order Runge-Kutta method. The tapering effects of a wiggler magnetic field on electron acceleration are investigated and the results show that the electron acceleration increases in the case of a tapered wiggler magnetic field with a proper taper constant. 相似文献
10.
V. N. Shvayko A. G. Krechetov B. P. Aduev A. V. Gudilin S. A. Serov 《Technical Physics》2005,50(6):732-735
An experimental setup for studying spectral-kinetic and space-dynamic characteristics of explosion-induced luminescence from
energetic materials is described. Explosion is initiated by nanosecond-and picosecond-wide electron and laser beams. Explosive
luminescence of a single sample is detected in a spectral interval 450 nm wide with a spectral resolution of 2 nm and a spatial
resolution of 50 μm. The time resolution, which is determined by a radiation source, is 30 ps. 相似文献
11.
Bharuthram R Parashar J 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,60(3):3253-3256
Cross-focusing of two copropagating laser beams in a plasma is investigated using paraxial ray theory. If the lasers have a frequency difference equal to the electron plasma frequency, they can drive a large amplitude plasma wave. The ponderomotive force due to the plasma wave forces the plasma electrons outwards thereby generating a parabolic density profile giving rise to cross-focusing. The results show a decrease in threshold for focusing by two orders of magnitude as compared to focusing due to the ponderomotive force of the laser beams. 相似文献
12.
Lindau F Lundh O Persson A McKenna P Osvay K Batani D Wahlström CG 《Physical review letters》2005,95(17):175002
The spatial distribution of protons, accelerated by intense femtosecond laser pulses interacting with thin target foils under oblique irradiation are investigated. Under certain conditions, the proton beams are directed away from the target normal. This deviation is towards the laser forward direction, with an angle that increases with the level and duration of the amplified spontaneous emission pedestal before the main laser pulse. In addition, for a given laser pulse, this beam deviation increases with proton energy. The observations are discussed in terms of different electron acceleration mechanisms and target normal sheath acceleration, in combination with a laser-controllable shock wave locally deforming the target rear surface. 相似文献
13.
Chuaqui H. Favre M. Soto L. Wyndham E.S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(6):778-783
Experimental observations are presented of prebreakdown electron beam generation in a transient hollow cathode discharge (THCD) in a vacuum. The discharge driver consists of a 400-kV maximum voltage, 25-nF Marx operated at 450-J stored energy coupled to a 120-ns, 1.5-Ω coaxial line. Electron beams with peak currents up to tens of kA are observed when a pulsed Nd:YAG laser is used to produce a plasma at the back of the cathode surface, inside the hollow cathode region (HCR). It is found that a plasma density of a few 1018 cm-3 in a volume of a few mm3 is required to generate intense electron beams. Optimal conditions are determined by varying the position of the laser focal spot inside the HCR and the time delay between the laser and the applied voltage. The main features of the electron beams are similar to those observed in conventional THCD at pressures in the 10-200 mtorr range 相似文献
14.
Fuchs J Cowan TE Audebert P Ruhl H Gremillet L Kemp A Allen M Blazevic A Gauthier JC Geissel M Hegelich M Karsch S Parks P Roth M Sentoku Y Stephens R Campbell EM 《Physical review letters》2003,91(25):255002
The evolution of laser-generated MeV, MA electron beams propagating through conductors and insulators has been studied by comparing measurement and modeling of the distribution of MeV protons that are sheath accelerated by the propagated electrons. We find that electron flow through metals is uniform and can be laser imprinted, whereas propagation through insulators induces spatial disruption of the fast electrons. Agreement is found with material dependent modeling. 相似文献
15.
The possibility of using a panoramic detector with a television signal-recording system in an apparatus to observe Thomson
scattering of laser radiation by a nonrelativistic electron beam is discussed. Panoramas of Thomson and Rayleigh scattering
and of the electron beam luminescence are presented. Estimates are given of the sensitivity and spatial resolution of the
apparatus. Results of panoramic and single-point methods of investigation are compared. Possibilities for extending the range
of the Thomson scattering method to measure the density distribution in nonrelativstic electron beams are discussed.
Zh. Tekh. Fiz. 69, 80–83 (June 1999) 相似文献
16.
This paper presents propagation of two cross-focused intense hollow Gaussian laser beams(HGBs) in collisionless plasma and its effect on the generation of electron plasma wave(EPW) and electron acceleration process,when relativistic and ponderomotive nonlinearities are simultaneously operative. Nonlinear differential equations have been set up for beamwidth of laser beams, power of generated EPW, and energy gain by electrons using WKB and paraxial approximations. Numerical simulations have been carried out to investigate the effect of typical laser-plasma parameters on the focusing of laser beams in plasmas and further its effect on power of excited EPW and acceleration of electrons. It is observed that focusing of two laser beams in plasma increases for higher order of hollow Gaussian beams,which significantly enhanced the power of generated EPW and energy gain. The amplitude of EPW and energy gain by electrons is found to enhance with an increase in the intensity of laser beams and plasma density. This study will be useful to plasma beat wave accelerator and in other applications requiring multiple laser beams. 相似文献
17.
18.
Self-Injection and Acceleration of Monoenergetic Electron Beams from Laser Wakefield Accelerators in a Highly Relativistic Regime 下载免费PDF全文
H.Yoshitama ;T.Kameshima ;谷渝秋 ;郭仪 ;焦春晔 ;刘红杰 ;彭翰生 ;唐传铭 ;王小东 ;温贤伦 ;温天舒 ;吴玉迟 ;张保汉 ;朱启华 ;黄晓军 ;安维民 ;黄文会 ;唐传祥 ;林郁正 ;王小东 ;陈黎明 ;H.Kotaki ;M.Kando ;K.Nakajima 《中国物理快报》2008,25(8):2938-2941
Self-injection and acceleration of monoenergetic electron beams from laser wakefield accelerators are first investigated in the highly relativistic regime, using 100 TW class, 27 fs laser pulses. Quasi-monoenergetic multi- bunched beams with energies as high as multi-hundredMeV are observed with simultaneous measurements of side-scattering emissions that indicate the formation of self-channelfing and self-injection of electrons into a plasma wake, referred to as a 'bubble'. The three-dimensional particle-in-cell simulations confirmed multiple self-injection of electron bunches into the bubble and their beam acceleration with gradient of 1.5 GeV/cm. 相似文献
19.
在100TW掺钛蓝宝石飞秒激光器上利用光学CCD相机和光学多道分析仪,分别在靶背法线方向测量了超热电子光辐射的空间分布和光谱.测量结果显示:光辐射空间分布图案呈圆环状,而辐射区域有发散角和光强分布,且包含多种辐射成分.光辐射光谱在800nm附近出现尖峰,是激光的基频(ω0)波,这一现象归因于超热电子束在输运的过程中产生的微束团而引起的相干渡越辐射(CTR).随着激光能量的增加,CTR光谱峰向红光方向移动,基频波红移的主要原因是由于等离子体临界面的迅速膨胀.如果考虑超热电
关键词:
超热电子
光辐射
共振吸收
红移 相似文献
20.
Z. Wang Y. Zhang P. Li S. Sang C. Yuan H. Zheng C. Li M. Xiao 《Applied physics. B, Lasers and optics》2011,104(3):633-638
We report experimental observations of intensity modulation and spatial splitting of four-wave mixing (FWM) signal beams which
can be effectively controlled by the polarization states of the pumping laser beams. Due to the periodic change of the pumping
beam’s polarization states, the intensity of the FWM beam also evolves periodically. The periodic spatial splitting phenomenon
has been observed in both x- and y-directions. The cases with/without the dressing beams are compared. Such studies can be very useful in better understanding
the formation of spatial solitons and for signal processing applications, such as spatial beam splitter, routing, and switching. 相似文献