共查询到20条相似文献,搜索用时 15 毫秒
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在相对论情况下,导出了速调管(klystron)和契伦柯夫(Cherenkov)器件中考虑空间电荷波影响的被调制电子束的谐波电流公式;并且分析了空间电荷波对电子束群聚的影响:在小信号时使群聚减小;在大信号时使群聚增强。 相似文献
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To simulate the intense bunched beam transport, a computer
program LEADS-3D has been developed. The particle trajectories are
analysed with the Lie algebraic method. The third order
approximation of the trajectory solutions is made with space charge
forces off, and the second order approximation is made with space
charge forces on. The particle distribution in the 3D ellipsoid is
uniform or Gaussian. Most of the conventional beam optical elements
are incorporated in the code. The optimization procedures are
provided to fit the beam lines to satisfy the given optical
conditions. 相似文献
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The betatron matching of a rotationally asymmetric beam in space charge dominated low-energy beam transports (LEBTs) where solenoids are used for the transverse matching has been studied. For better understanding, the coupling elements of a beam matrix are interpreted in special forms that are products of a term defined by the Larmor rotation angle and another by the difference between the beam matrix elements in the two transverse planes. The coupling form originally derived from the rotationally symmetric field in solenoids still holds when taking into account the rotationally asymmetric space charge forces that are due to the unequal emittance in the two transverse planes. It is shown in this paper that when an LEBT mainly comprising solenoids transports a beam having unequal emittance in the two transverse planes and the linear space charge force is taken into account, the initial Twiss parameters can be modified to obtain the minimum and equal emittance at the LEBT exit. The TRACE3D calculations also prove the principle. However, when quadrupoles that are also rotationally asymmetric are involved in between solenoids, the coupling between the two transverse planes becomes more complicated and the emittance increase is usually unavoidable. A matching example using the CSNS (China Spallation Neutron Source) LEBT conditions is also presented. 相似文献
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The betatron matching of a rotationally asymmetric beam in space charge dominated low-energy beam transports (LEBTs) where solenoids are used for the transverse matching has been studied.For better understanding, the coupling elements of a beam matrix are interpreted in special forms that are products of a term defined by the Larmor rotation angle and another by the difference between the beam matrix elements in the two transverse planes.The coupling form originally derived from the rotationally symmetric field in solenoids still holds when taking into account the rotationally asymmetric space charge forces that are due to the unequal emittance in the two transverse planes.It is shown in this paper that when an LEBT mainly comprising solenoids transports a beam having unequal emittance in the two transverse planes and the linear space charge force is taken into account, the initial Twiss parameters can be modified to obtain the minimum and equal emittance at the LEBT exit.The TRACE3D calculations also prove the principle.However, when quadrupoles that are also rotationally asymmetric are involved in between solenoids, the coupling between the two transverse planes becomes more complicated and the emittance increase is usually unavoidable.A matching example using the CSNS (China Spallation Neutron Source) LEBT conditions is also presented. 相似文献
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《Journal of Electrostatics》2014,72(6):457-461
At present, there is no appropriate measurement techniques for space charge. In this paper, a U-shaped cavity device is developed as the space charge measurement device, which can be applied to transmission lines. Its design principle and calculation techniques of design parameter are also introduced. To test the space charge measurement accuracy of the U-shaped cavity device, a space charge generator is developed specifically for this experiment. The test results are excellent and show that the U-shaped cavity device can meet the design requirements. This technique is suitable for space charge measurement under transmission line normally charged work condition. 相似文献
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Among features observed in polyethylene-based materials under high fields, packet-like space charge are frequently reported but without complete theory explaining their formation and propagation. The present contribution reports transient dynamics of packet-like space charge in low-density polyethylene (LDPE) under multi-field coupling conditions based on pulsed electro-acoustic (PEA) method. The measurements were carried out under −125 kV/mm at 20 °C, 40 °C, and 60 °C. Space charge results reveal systematic occurrence of positive packet-like space charge in all samples generated at the anode and then moved toward the cathode. It is observed that higher temperatures contribute to the migration of packet-like space charge and field distortion. Based on the detailed injection model of packet-like space charge, it is shown that electrode injection plays a major role in the formation of positive packet-like space charge, the total amount and depth not only depend on the temperature, but also the negative charges dynamics. Packet-like space charge phenomena at different temperatures still feature NDM relationship with the nonlinear increase of migrate velocity as the rise of temperature. 相似文献
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在相对论情况下,导出了速调管(klystron)和契伦柯夫(Cherenkov)器件中考虑空间电荷波影响的被调制电子束的谐波电流公式;并且分析了空间电荷波对电子束群聚的影响:在小信号时使群聚减小;在大信号时使群聚增强。 相似文献
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线型离子阱中的离子在射频场作用下做宏观的久期运动,久期运动频率与实验参数有关.但当离子阱中囚禁大量同种电荷的离子时,空间电荷效应会导致离子间存在相互排斥的库仑力,使离子的运动频率发生漂移.本文通过求解泊松方程计算了空间电荷产生的附加电场的解析表达式,在小振动近似下理论计算了该附加电场对久期运动频率的影响,模拟了不同离子云中心密度下久期频率的漂移,讨论了离子云的数目、温度与实验参数之间的关系.对用离子阱进行的频标实验、碰撞实验和其他方面的研究都具有重要的指导意义. 相似文献
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为了在无箔二极管电磁PIC模拟中采用与电磁场自洽的空间电荷限制发射模型,对查尔特定律模型、高斯定律模型和一维二极管模型进行了理论分析和实例模拟比较。模拟结果表明,三种模型都能与电磁场自洽并反映外加磁场对发射电流的影响,但高斯定律模型受网格剖分粗细程度的影响较大且容易产生振荡,一维二极管模型在网格参数合理的情况下结果与查尔特定律模型基本接近,但需要求解超越方程,花费时间多。通过对模拟结果进行分析和比较,认为外加磁场对电子发射模型本身的影响很小,在电磁PIC数值模拟中可以不考虑,因此,查尔特定律模型更适合用于无箔二极管的电磁PIC模拟。 相似文献
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Electron beam modeling and analyses of the electric field distribution and space charge effect 下载免费PDF全文
Yueling Jiang 《中国物理 B》2022,31(5):54103-054103
In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam's cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed. 相似文献
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《Journal of Electrostatics》2014,72(4):252-260
In this paper, space charge dynamics under DC electric field of −100 kV/mm in low-density polyethylene (LDPE) and its nanocomposite containing a small amount of MgO nanoparticles were measured using an improved pulsed electro-acoustic (PEA) system. Unlike negative packet-like space charge accumulating in LDPE films, no remarkable space charge was observed in LDPE/MgO nanocomposite films, which indicated that the introduction of MgO nanoparticles played a key role on the space charge suppression. Different with current qualitative models, this paper describes space charge suppression on the basis of simulation using the bipolar charge transport model, which featured bipolar charges injection, transport, trapping, recombination, and extraction process. It was shown from the simulation that trap depth, trap concentration, local electric field and charge injection barrier height were all significant factors on the space charge suppression process. A deeper trap depth in LDPE/MgO nanocomposites made it easier for traps to capture mobile carriers. And a larger trap concentration effectively slowed down the whole carrier movement although there seemed a trap concentration threshold less than 30 Cm−3, above which this effect became slight. In addition, both the high permittivity of LDPE/MgO nanocomposites and low local electric field in the vicinity of cathode led to a larger injection barrier height based on the Schottky injection law, which would tremendously block the charge injection. At last, the suppression mechanism of space charge formation in the LDPE/MgO nanocomposites is presented. 相似文献
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In order to study the effect of epitaxial crystallization on charge transport in low-density polyethylene (LDPE) under multi-field coupling conditions, three typical epitaxial crystallizations, namely disorder (glass substrate), crossover (isotactic polypropylene substrate), and parallel (polytetrafluoroethylene substrate), were prepared and denoted as LD-G, LD-iPP, and LD-PT, respectively. Packet-like space charge through samples was analyzed by the pulsed electro-acoustic (PEA) method. It is shown that different microscopic surface morphologies appeared in the LDPE samples with different epitaxial crystallizations, which, however, do not change the crystalline structure of the bulk. Packet-like space charge phenomena were observed and the distortion field increased with the temperature which could be attributed to the larger amount of charge injection in a shorter period. The differences of the amount and injection rate of the space charge were explained and verified considering the typical chain alignment of epitaxial crystallization, which, in our opinions, contributes to the pass over of positive charge in LD-iPP samples. 相似文献
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首次研究了磁绝缘线振荡器中射频场(包括辐射波场和空间电荷波场)对空间电荷的调制,得到了在饱和时谐波电流一阶分量的公式。这个公式表明:考虑空间电荷波时,在小信号和辐射波与空间电荷波同相的条件下,它将增强谐波电流。在大信号时,情况不确定;谐波电流一阶分量将随二极管上电压的增加而增加,随运行频率和饱和长度的增加而减少。 相似文献