超短电子脉冲在聚焦强激光场中的三维有质动力散射

采用三维测试粒子模拟(test-padicle simulation)的方法，研究了聚焦的飞秒脉冲强激光与超短电子束进行有质动力的散射过程.详细讨论了超短电子束经过不同激光延迟下有质动力散射的空间分布特征和能谱特征.提出了通过测量电子束的空间分布和能谱分布实现对超短脉冲电子束的脉冲宽度测量的方法. 关键词： 有质动力散射 聚焦的飞激光 飞秒电子束     

Collisional radiative model for the M1 transition spectrum of the highly-charged W54+ ions

A detailed-level collisional-radiative model for the M1 transition spectrum of the Ca-like W⁵⁴⁺ ion as observed in an electron beam ion trap (EBIT) was constructed based on atomic data calculated by the relativistic configuration interaction method and distorted wave theory. The present calculated transition energy, rate and intensity of W⁵⁴⁺ M1 transitions are compared with previous theoretical and experimental values. The results are in reasonable agreement with the available experimental and theoretical data. The synthetic spectrum explained the EBIT spectrum in the 12–20 nm region, while a new possibly strong transition has been predicted to be observable with an appropriate electron beam energy. The present work provides accurate atomic data that may be used in plasma diagnostics applications.     

电子直线加速器磁控管频率稳定的自适应线性神经元方法

 电子直线加速器电子束能量的稳定与否取决于功率源工作频率的稳定性,磁控管在短时间内的散谱和轻微跳谱造成稳频系统的控制精度下降,最后电子束的扫描均匀度下降。引入自适应线性神经元方法(ADALINE)和噪声对消技术以消除对工作频率长期稳定性的影响,从而保证了电子束的扫描均匀度。     

Experimental studies of gyrotron electron beam systems

In order to provide electron beams of powerful gyrotrons, magnetron-injection guns operating in the regime of the temperature limited current are used. The electron beam quality and gyrotron performances are defined both by the cathode emission processes and the processes occurring in the electron beam during its formation and transportation. The results of measurements of the energy spectrum and velocity spread of the gyrotron electron beam in different regimes are given. Experimental data on the parameter of efficient emission inhomogeneity for different regimes are presented, as well as the dependencies of electron beam parameters on efficient inhomogeneity of the cathode     

Parameters of the electron beam in a betatron with radial comb-type poles

Expressions for the vector potential and components of the magnetic field induction vector of a betatron with radial comb-type poles are derived. The dynamics of the electron beam in the electromagnetic betatron field is investigated in the process of electron injection and acceleration. It is demonstrated that the azimuthally varying field engender beam beats. However, the amplitudes of beam particle oscillations during acceleration do not exceed their values estimated from the symmetric azimuthal component of the betatron magnetic field induction. The energy spectrum of accelerated electrons is not described by a normal law. In the electron energy spectrum, the relative number of electrons whose energy exceeds the average value is large. Application of poles with radial combs improves the efficiency of electron capture in acceleration. Results of investigations can find application in the development and adjustment of electron beam accelerating systems. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 27–34, October, 2005.     

Effect of an electron beam generated in an X-pinch plasma on the structure of the K spectra of multiply charged ions

The first experimental studies of an electron beam generated in an X pinch on the XP machine (Cornell University, USA) and the BIN machine (P. N. Lebedev Physical Institute, Russian Academy of Sciences) are reported. It is shown that it is possible in an X pinch to isolate the effect of a plasma-generated electron beam on the multiply charged ion radiation. The intensities of the satellite lines corresponding to Li-, Be-, B-, and C-like ions are calculated for the Al spectrum on the basis of a collisional-radiative model with a non-Maxwellian electron distribution in the plasma. The effect of an electron beam on the multiply charged light ion radiation in an X-pinch plasma is demonstrated. Comparing our calculations with the experimental spectra, we conclude that the present model can be used to estimate the electron beam intensity. Zh. éksp. Teor. Fiz. 112, 894–909 (September 1997)     

“Instantaneous” spectrum of passively ionized electrons in a dielectric irradiated by a high-power electron beam

A technique is developed for theoretical analysis, and the “instantaneous energy spectrum,” that is, the energy spectrum of passively ionized electrons in a dielectric irradiated by an electron beam of moderate or high density which arises prior to electron-phonon relaxation is calculated. The source of the beam is usually a high-current electron accelerator. The computation algorithm is designed so as to make it possible to fully take into account and make use of the following data: first, the actual (measured) spectrum of the electron beam; second, the complete electron spectrum of the dielectric, including the spectrum of the density of occupied states, which is continuous within the valence bands and discrete in the region of the low-lying quasiatomic levels; and the spectrum of the density of unoccupied states, which begins in the conduction band and, in a continuous process, turns into the spectrum of quasi-free electrons in the crystal; third, the differential ionization cross-sections of the atoms due to electron impact, which the present report refines so as to take in into account the actual spectrum of the density of the final states; the latter spectrum is continuous within the valence bands and discrete in the region in which the law of dispersion of a band electron turns into the law of dispersion of a quasi-free electron. The results of the theoretical analysis are compared with the data of a numerical experiment carried out in the present report by the Monte-Carlo method using the same initial data. The agreement between the theoretical results and the data from the numerical experiment demonstrates the stability and reliability of the algorithm used to calculate the instantaneous spectrum. The precision of the calculation is determined solely by the initial data. The instantaneous spectrum which is obtained is the initial distribution function for all the kinetic equations describing subsequent relaxation of the electrons in the irradiated dielectric. Tomsk Polytechical Institute. Tomsk State University. Institute of High-Current Electronics, Russian Academy of Sciences (Siberian Division). Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 136–144, November, 1996.     

Amplification of monochromatic short-wavelength radiation during the stochastic deceleration of a relativistic electron stream in an incoherent pump field

The use of incoherent multiwave pump radiation or randomly varying magnetostatic fields (stochastic undulators) for improving the energy conversion efficiency in free-electron lasers based on stimulated wave scattering and the stimulated undulator emission of relativistic electron beams is proposed. It is shown within the quasilinear approximation that the electronic efficiency increases in proportion to the width of the pump spectrum due to enrichment of the spectrum of combination waves which are synchronous with the electron beam and realization of a mechanism of stochastic particle deceleration when the signal wave is monochromatic. At the same time, the efficiency scarcely depends on the spread of the beam parameters, making the use of the method promising for improving the efficiency of free-electron lasers powered by intense relativistic electron beams. Zh. Tekh. Fiz. 67, 77–81 (July 1997)     

Monte Carlo simulation of the dose deposited into GAFCHROMIC® film by X-rays produced by the electron beam of PFMA-3

The electron beam emitted backward by Plasma Focus devices is being investigated as a radiation source for IORT (Intra-Operative Radiation Therapy) applications. A Plasma Focus device is being developed to this aim, to be utilized as an X-ray source. The electron beam is driven to impinge on a 50 μm brass foil, where conversion X-rays are generated. Monte Carlo simulations of the X-ray emission have been conducted with MCNPX, with the purpose of estimating penetration in and dose to human tissue. The electron spectrum had been determined experimentally and is used in the present work as input to the simulations. X-ray emission both from bremsstrahlung and from characteristic lines is predicted. The spectrum is found to be comprised of two components: one peaked at 10 keV and one centred around 50 keV. Doses to film determined from the present simulations are compared to experimental values obtained in a previous work by the authors: the results are found in very good agreement.     

Monte Carlo simulation of electron beam air plasma characteristics

A high-energy electron beam generator is used to generate a plasma in atmosphere. Based on a Monte Carlo toolkit named GEANT4, a model including complete physics processes is established to simulate the passage of the electron beam in air. Based on the model, the characteristics of the electron beam air plasma are calculated. The energy distribution of beam electrons (BEs) indicates that high-energy electrons almost reside in the centre region of the beam, but low-energy electrons always live in the fringe area. The energy deposition is calculated in two cases, i.e., with and without secondary electrons (SEs). Analysis indicates that the energy deposition of SEs accounts for a large part of the total energy deposition. The results of the energy spectrum show that the electrons in the inlet layer of the low-pressure chamber (LPC) are monoenergetic, but the energy spectrum of the electrons in the outlet layer is not pure. The SEs are largely generated at the outlet of the LPC. Moreover, both the energy distribution of BEs and the magnitude of the density of SEs are closely related to the pressure of LPC. Thus, a conclusion is drawn that a low magnitude of LPC pressure is helpful for reducing the energy loss in the LPC and also useful for greatly increasing the secondary electron density in dense air.     

An aes study of a copper-iron sulphide mineral

Synthetic bornite, Cu₅FeS⁴ has been studied by Auger electron spectroscopy. Sputtercleaned bornite shows a sulphur spectrum with three peaks at 138, 147 and 149 eV. These Auger transitions are different from those observed when sulphur is adsorbed on metal surfaces, where the peaks are at 139, 149 and 154 eV. The adsorption of oxygen on the surface of bornite at room temperature results in the formation of a layer of iron oxide and, in addition, the sulphur spectrum loses its fine structure and shows only a single peak at 148 eV. Under the influence of both the ion sputter beam and the electron beam, the surface composition of bornite shows large and rapid changes which are due mainly to movement of mobile Cu⁺ ions through the lattice, this movement being caused by surface charging effects.     

Ejected electron spectrum of sodium autoionizing levels obtained by electron impact excitation 'at 500 eV incident energy

The ejected electron spectrum of sodium vapour has been observed at 90° to the direction af an incident electron beam with kinetic energy 500 eV. Comparisons are made with the ultraviolet absorption data.     

Analysis of the triode gun and the beam dynamics of a standing waveelectron linac

The charge-density integral method is used to analyse a triode gun which will inject electrons into a standing wave electron linac. The effect of space charge on the gun output beam parameters is estimated. The beam dynamics of the entire linac system is studied. The energy spectrum, beam size and divergence at the end of the linac are evaluated neglecting space charge     

CAEP远红外100 μm FEL自发辐射谱的实验研究

在FEL实验中,电子束通过摇摆器,一方面由于周期性磁场作用,电子束轨迹要周期性的摆动,另一方面还要辐射同FEL辐射波长一致的自发辐射,该辐射谱反映电子束、摇摆器集成后的参数。在CAEP(Institute of China Academic Engineering Physics)远红外100 μm FEL实验中,自发辐射谱通过Ge∶Ga低温探头和远红外100 μm光栅谱仪测量。文章侧重从实际摇摆器磁场分析了远红外100 μm FEL的自发辐射谱。     

Comparison of the CKLL first-derivative auger spectra from XPS and AES using diamond,graphite, SiC and diamond-like-carbon films

The carbon KLL first-derivative Auger spectra obtained by numerically differentiating the XPS N(E) line gives a better fine-structure fingerprint of the carbon state than conventional AES. The first-derivative of the X-ray excited (XAES) CKLL spectrum from a diamond-like-carbon (DLC) film exhibited almost the same spectrum as both the XAES and AES spectra from natural diamond. However, the AES spectrum of the DLC film indicated a graphite-like structure due to electron beam damage. Comparison of the XAES and AES spectra suggested that the electron beam used in conventional AES partially changed the plasmon loss structure of carbon in diamond, graphite and β-SiC as well.     

Simulation of the current induced by 63Ni beta radiation

The current generated by radiation from a ⁶³Ni layer of variable thickness is simulated with the actual spectrum of emitted electrons and with their distribution over the angles for Si and SiC taken into account. The dependences of the generation rate for nonequilibrium charge carriers on the depth are obtained for the cases of several Ni film thicknesses for both materials. The results are compared with the simulation results for a monoenergetic electron beam that is perpendicular to a semiconductor detector. It is shown that, for both Si and SiC, it is possible to choose an energy value of the electron beam in a SEM such that the ratio of the currents induced by the SEM beam and beta radiation from ⁶³Ni is essentially independent of the diffusion length.     

Optimization studies of photo-neutron production in high-<Emphasis Type="Italic">Z</Emphasis> metallic targets using high energy electron beam for ADS and transmutation

Monte Carlo calculations have been performed using MCNP code to study the optimization of photo-neutron yield for different electron beam energies impinging on Pb, W and Ta cylindrical targets of varying thickness. It is noticed that photo-neutron yield can be increased for electron beam energies ≥100 MeV for appropriate thickness of the target. It is also noticed that it can be maximized by further increasing the thickness of the target. Further, at higher electron beam energy heat gradient in the target decreases, which facilitates easier heat removal from the target. This can help in developing a photoneutron source based on electron LINAC by choosing appropriate electron beam energy and target thickness to optimize the neutron flux for ADS, transmutation studies and as high energy neutron source etc. Photo-neutron yield for different targets, optimum target thickness and photo-neutron energy spectrum and heat deposition by electron beam for different incident energy is presented.      

强流脉冲电子束时间分辨测试技术研究

简单介绍了LIA注入器中强流脉冲电子束能谱分布及发射度的测量原理.应用变象管扫描相机测量了脉冲宽度为100ns的强流脉冲电子束的能谱分布及发射度两个参量,得到了具有时间分辨本领为1ns的切伦科夫辐射图像.为强流直线感应加速器的研制,提供了实验数据.     

The effect of the earth's magnetic field on auger analysis

Semi-quantitative analyses of thin films or surfaces are commonly obtained from the peak intensities in the differentiated Auger spectrum. To reduce effects of surface roughness, beam focus and electron current, ratios of peak heights are used rather than absolute values. In performing analysis of CdSe single crystal and thin film samples in a commercial Auger analyzer fitted with a cylindrical mirror analyzer (CMA), the ratio of the Cd(376 eV) to Se(1315 eV) peaks was found to vary by as much as 15% when the diameter of the incident electron beam was increased from 5 to 60 μm. The effect was found to be due to an energy-dependent shift of the electron beam caused by the earth's magnetic field. The electron transmission of the CMA was measured as a function of the primary electron beam spot position on the sample. The transmission decreases rapidly once the spot falls outside an area with a radius ～25 μm. Due to this response, the relative shift in position caused by the magnetic field produces variations in peak ratios when the spot size is changed. This effect will produce inaccurate analysis if the Auger peaks differ significantly in energy and the primary electron beam spot size is large, and accounts for the observed 15% variation in $\text{Cd}\text{Se}$ ratio.     

Observation of fine structures in laser-driven electron beams using coherent transition radiation

We have measured the coherent optical transition radiation emitted by an electron beam from laser-plasma interaction. The measurement of the spectrum of the radiation reveals fine structures of the electron beam in the range 400-1000 nm. These structures are reproduced using an electron distribution from a 3D particle-in-cell simulation and are attributed to microbunching of the electron bunch due to its interaction with the laser field. When the radiator is placed closer to the interaction point, spectral oscillations have also been recorded, signature of the interference of the radiation produced by two electron bunches delayed by 74 fs. The second electron bunch duration is shown to be ultrashort to match the intensity level of the radiation. Whereas transition radiation was used at longer wavelengths in order to estimate the electron bunch length, this study focuses on the ultrashort structures of the electron beam.