A high power density submicron electron beam source

An electron-optical system (with a thermal field electron source-cathode) is introduced. The system is designed to form on the target surface submicron microprobes of a power density exceeding the ablation threshold ( approximately 10(8)W/cm(2)) of condensed media. The numerical modeling of electron paths carried out using a software package (TAU) developed by the authors has shown that the proposed electron-optical system is capable of forming microprobes of a power density comparable with that of modern high-power pulsed laser sources (up to approximately 10(11)W/cm(2)).     

Collective Thomson scattering of a high power electron cyclotron resonance heating beam in LHD (invited)

Collective Thomson scattering (CTS) system has been constructed at LHD making use of the high power electron cyclotron resonance heating (ECRH) system in Large Helical Device (LHD). The necessary features for CTS, high power probing beams and receiving beams, both with well defined Gaussian profile and with the fine controllability, are endowed in the ECRH system. The 32 channel radiometer with sharp notch filter at the front end is attached to the ECRH system transmission line as a CTS receiver. The validation of the CTS signal is performed by scanning the scattering volume. A new method to separate the CTS signal from background electron cyclotron emission is developed and applied to derive the bulk and high energy ion components for several combinations of neutral beam heated plasmas.     

Measuring the density of a molecular cluster injector via visible emission from an electron beam

A method to measure the density distribution of a dense hydrogen gas jet is presented. A Mach 5.5 nozzle is cooled to 80 K to form a flow capable of molecular cluster formation. A 250 V, 10 mA electron beam collides with the jet and produces H(α) emission that is viewed by a fast camera. The high density of the jet, several 10(16)?cm(-3), results in substantial electron depletion, which attenuates the H(α) emission. The attenuated emission measurement, combined with a simplified electron-molecule collision model, allows us to determine the molecular density profile via a simple iterative calculation.     

A source of a high-power relativistic electron beam with high brightness

A ribbon diode of a U-2 accelerator (800 kV, ∼30 kA) intended for generating a high-intensity electron beam for heating plasma in a GOL-3 multimirror magnetic trap (Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences) is described. The parameters of the beam characterized by a high brightness (∼7 kA/(cm² sr)) in a magnetic field of ∼5 T resulting from a numerical simulation of the beam formation process are presented. The results of simulation of the beam transport and transformation of the profile of its cross section during movement of electrons in a curvilinear guiding magnetic field are presented. The calculated cross section is compared to the beam imprint on a target.     

电子束焊接在运输机械传动部件中的应用

简要介绍电子束焊接技术的基本特点,着重分析电子束焊接技术在汽车变速箱、重型卡车桥壳、摩托车传动离合器、工程矿山机械动力换档变速箱离合器以及联合收割机传动轴等方面的应用。     

Master controller of a high-voltage power unit source of an electron beam welding device

This paper describes the structure and control algorithms of a controller of a high-voltage source with an output voltage of 60 kV and a power of up to 30 kW. The source is designed to be used as part of a power unit of an electron-beam welding device developed at the Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences (BINP SB RAS). High-quality welds require a stable electron beam energy. Herewith, a standard operation mode is quick and deep modulation of the electron current. The problem of achieving high-quality control and limiting the transient distortions of output voltage of the source is solved. The error of establishing and stabilizing the output voltage is 0.1%, which allows obtaining high-quality welding. Transient distortions at 100% modulation of the load current do not exceed the value of ±1%, which, along with fast reaction of the source to a load breakdown (energy released during breakdown is smaller than 15 J), protects the welded parts and elements of the gun from being damaged by an electron beam.     

柱塞结构对高压脉动水锤装置产生压力冲击的影响

高压脉动水锤装置产生压力冲击的过程中,柱塞起着传递能量和产生冲击的作用,其结构上的尺寸比例与水锤装置的输入、输出压力比值存在一定的关系.文章通过假设,理论分析得出了这一关系式,并通过实验来进行了测试验证,得出结论为水锤装置压力比极值所对应的柱塞直径比位于1:3～1:2之间.最后针对理论与实验之间的差异进行了简单的分析.     

制造用高功率激光器光束质量的评价与测量

建立了制造用高功率激光器光束质量的评价体系与测量方法,研究了该体系所采用的评价参数、测量原理、测量方法、测量仪器以及测量结果的计算和分析方法.首先,对目前存在的评价激光光束质量的参数进行了比较和判断.接着,以光束传输比(M2)和光束参数积(Kf)为重点,阐述了光束质量评价参数与光束束宽定义之间的关系,提出了工业应用背景...     

Infrared thermography of a high-power neutral beam target

In conjunction with an experiment on high-power neutral beam injection for a fusion device, infrared thermography has been used to observe the beam-target interaction in a prototype injector vessel. The infrared radiation from the beam itself was studied, which allowed the evaluation of the signal to noise ratio in the injection experiment.     

强激光器光路对准检测系统研究

针对复合轴强激光系统光路装调的需求,充分考虑了轴系多,功率密度大等特点,设计出一种光路对准检测方法,对上下行光路进行自准直.同时在上行光路中,建立基准光,利用基准镜内缘的小孔,进行光路对准检测.     

高功率激光热效应对合束系统的影响

提出利用镀膜合束的方法对三路光束进行合束用于高功率红外激光合束系统设计。考虑系统中关键元件使用的红外材料ZnSe易受热效应影响,采用光机热耦合分析方法,研究了在温度边界条件固定时,各波段激光所产生的耦合热效应对各路激光波前畸变的影响,同时定性分析了系统中存在的激光偏置热效应。研究结果显示,系统中各波段的激光波前畸变均方根值(RMS)均满足设计要求(各波段波前畸变小于λ/8);激光偏置造成的波面高频成分增大了长波激光波前畸变量,但高频成分对系统波前畸变影响依然满足要求;轴向温差可在35s达到平衡,对光束波前造成主要影响的是各块镜片的面型畸变。根据分析结果搭建了实验平台,利用系统中短波400 W激光进行实验,采集了该条件下的面型并与仿真结果进行了对比,实验结果验证了该分析方法计算结果的准确性。     

平滑化窄脉冲高功率准分子激光放大技术

对于高功率准分子激光,光学角多路和诱导空间非相干(EFISI)光束平滑是高功率准分子激光压缩脉宽、提高功率密度和实现靶面均匀辐照的有效途径,其应用涉及前端至靶前的各个环节,主要体现为平滑化窄脉冲激光的传输放大问题.首先介绍了基于散射法开展的部分相千源前端技术及脉冲整形的初步研究结果,利用直接法和反射率耦合方法,研究了5...     

Calculation of the variable-profile electron beam for electron coolers

Interaction of an electron beam with a cooled ion beam makes it possible to reduce its phase volume, perform accumulation of particles, and suppress various “heating” effects. The electron beam can also be used as a target for an electron-ion recombination reaction, which offers a chance to carry out atomic physics experiments and ensure slow uniform extraction of the ion beam from the storage ring. A high-perveance electron beam with a variable profile is required for effective cooling, while a high current density and a low energy of transverse motion of electrons in the beam is needed for extraction by means of recombination. It is shown that a convex cathode placed in a magnetic field can be used to form such a beam. A high current density can be attained with this shape of the cathode, but additional efforts must be focused on optimizing the gun’s optics in order to obtain a low energy of transverse motion of particles. Since ions repeatedly pass through the cooling section during their lifetime at different values of the betatron oscillation phase, the rates of recombination and cooling are dependent on the rms electron velocity averaged over the volume in which the beam interaction occurs. The proposed design of the gun with a convex cathode 10.2 mm in diameter ensures formation of a variable-profile electron beam with a nominal current of 1 A and a current density of 1.2 A/cm². The rms energy of Larmor gyration of electrons at the exit from the gun, averaged over the beam cross section (the “transverse” temperature) is 1 eV. A focusing electrode that forms the Pierce optics near the edge of the cathode, an electrode controlling the beam profile, and an anode are included in the optics of the electron gun.     

On the accuracy of high impulse voltage measurements

Measurements and tests on solid dielectrics with lightning or switching impulses have received considerable attention because they are concerned in the optimal design of internal insulation for high voltage apparatus. Accuracy of measurements relating to the above phenomena is generally deemed very important. In this paper a model is proposed and an investigation is attempted regarding the accuracy of such measurements. The results are confirmed through laboratory measurements. According to the results presented, the value of the grounding resistance is a crucial parameter that affects measurement accuracy; it must never exceed the value of 0.5 Ω.     

高功率激光合束器工作可靠性能评估方法研究

为降低高功率激光在单根光纤中的传输风险,提出基于多光纤传输的激光非相干空间合束19×1圆斑合束器。基于“内外同心圆+中心”同轴排列方式,采用光线追迹法进行合束器的光学设计,同时为实现合束器长期运行可靠性评估,基于多激光束同步照射光学元件的体吸收模型,采用有限元方法对合束器内部透镜的温度、热畸变和热应力等进行研究。结果表明,在10 kW激光照射30 mins下,合束器内部透镜的最高温度为381.11 K,远低于熔融石英1 900 K的软化点温度,热畸变相关的最大光圈数为0.07,远小于1个光圈数的透镜加工公差,热应力最大值为14.02 MPa,小于熔融石英4.5 GPa的屈服应力。此外实验测得合束器输出总功率可达10.43 kW。本研究对评价其他高功率激光系统的长期运行可靠性提供了有效的方法参考。     

An alternative method for the measurement of the mechanical impulse of a vertically directed blast

An alternative method for the measurement of the total mechanical impulse of a vertically directed blast due to an explosive charge is presented. The method differs from apparatus that employ a vertically displaced mass (similar in principle to the ballistic pendulum) in that a relatively compact spring-damper system is employed to constrain the movement of the mass. The mechanical impulse is determined by integrating, with respect to time, the net force applied to the spring-damper system. The details of an explosive impulse measuring instrument rated to 12 kN s are presented.     

The importance of beam alignment and crystal tilt in high resolution electron microscopy

The relative influences of crystal tilt and beam alignment on high-resolution electron-microscopic imaging have been investigated. With the use of contrast transfer theory in generalised dimensionless form, the major effect of slight beam misalignment has been shown to be the introduction of an antisymmetric phase shift in the diffracted beams so that the presence of any such misalignment cannot be detected by the standard diagnostic tool of high-resolution electron microscopy, namely the optical diffractogram. Specific image simulations, at 100 and 500 keV, for materials of both small and large unit cells (SnO₂ and Ti₂Nb₁₀O₂₉ respectively) show, however, that even slight beam tilt can have a marked effect on the images of crystalline materials, causing considerable spurious detail and a loss of expected symmetry. The various options for ensuring accurate beam and crystal alignment are briefly reviewed, and some aspects of the alignment problems are demonstrated using some recent experimental images recorded at 500 kV.     

Microstructure and mechanical properties of similar and dissimilar stainless steel electron beam and friction welds

Microstructure and mechanical properties of similar and dissimilar welds of austenitic stainless steel (AISI 304), ferritic stainless steel (AISI 430), and duplex stainless steel (AISI 2205) have been studied. Welding processes electron beam welding and friction welding were used. Optical, scanning electron microscopy, and electron probe microscopy were carried out to study the microstructural changes. Residual stress, hardness, tensile strength, and impact toughness testing were conducted to study mechanical behavior. Dissimilar metal electron beam welds of austenitic–ferritic, ferritic–duplex, and austenitic–duplex stainless steel welds contained coarse grains, which are predominantly equiaxed on austenitic, duplex stainless steel side, and they are columnar on the ferritic stainless steel side. Diffusion of elements was significant in electron beam welding and insignificant in friction welds. Austenitic–ferritic stainless steel exhibited tensile residual stress on the ferritic stainless steel side adjacent to the interface, compressive stresses on the austenitic stainless steel side that matches with the delta ferrite microstructure observed in this region. High compressive stresses were noted on duplex stainless steel side interface compared to austenitic stainless side interface. The highest tensile strength was observed in duplex–austenitic stainless steel joints. The impact strength and notch tensile strength of electron beam weldments are higher than the friction weldments. All electron beam and friction welds showed toughness lower than parent metals.     

Microstructure and tribological properties of Al-Pb alloy modified by high current pulsed electron beam

In the present work, Al-Pb alloy was irradiated by high current pulsed electron beam. X-ray diffractometer, electronic probe microanalysis, scanning electron microscopy and Knoop hardness indentation were used to characterize the microstructure and mechanical property of Al-Pb alloy. The results show that the microstructure and mechanical property can be greatly improved. The tribological properties of high current pulsed electron beam irradiated Al-Pb alloy were investigated under dry sliding conditions using a pin-on-disc type wear testing machine. The overlapped zone beneath the melted zone exhibits good resistance to wear. Optical observation and scanning electron microscopy analysis reveal that the low wear rate and lowest level in coefficient of friction at high load level for irradiated Al-Pb alloy are due to a lubricious tribolayer covering almost the entire worn surface. The wear mode varies from oxidative wear at low load to film spalling at high load and, finally, adhesive wear.