共查询到19条相似文献,搜索用时 93 毫秒
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提出了运用双束电子束增加回旋行波放大器带宽的新想法,建立了模型并对其做了理论分析和数值模拟.研究表明:该模型不仅可产生宽的输出带宽和高的输出功率,且与已有宽带模型相比,增益要高得多.当两束电子束的电流均为10A,电压分别为90和153kV,速率比分别为1.0和0.62,纵向动量散度分别为5.5%和1.2%时,器件输出的饱和带宽至少可达到22%,峰值功率和指数增益分别为395kW和62dB,效率为16%;如果在相互作用区的末段对引导磁场进行弱的锥化,可以得到约23%的常量驱动带宽,输出功率仍有280kW.
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根据拉格朗日方程对电子在平滑会切磁场中的径向波动与速度零散的关系进行讨论。运用Matlab,Magic软件相互结合的方法设计电子枪结构和磁场。用Matlab程序模拟单电子在给定电场、磁场中的运动,分析了单电子径向速度对零散的影响,并优化磁场分布。设计的磁场可以有效地减小单电子束径向速度,降低电子束速度零散。用Magic软件对电流为1 A、能量为30 keV的电子束在优化磁场中的运动进行仿真,得到的电子束速度比约为2,速度零散小于2.5%,轴向速度零散小于8.5%。 相似文献
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提出了一种过模复合器件。自洽地导出了由外电磁信号和预群聚电子束同时驱动的一种过模复合器件的辐射波相位锁定方程;讨论了到达锁相运行的时间、频率移动和带宽。分析表明:当由预群聚电子束和外电磁信号同时锁相时,通过调节参数,可以缩短到达锁相运行的时间,减小运行频率对要锁定的频率(外电磁信号频率)的移动和增大锁相运行的带宽。 相似文献
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为了实现高功率微波发生器的小型化,开展了S波段低磁场相对论返波振荡器工作特性的研究工作。由于S波段返波振荡器频率低,对应的电子回旋共振磁场强度也很低,因此低磁场条件下面临着电子束传输效率低和束波互作用效率低两大问题。为解决上述问题,采取下列措施:通过加大电子束与器件内壁的距离,提高电子束传输效率;采用较深的慢波结构作为提取腔,实现高束波互作用阻抗;提取腔前采用浅深度慢波结构,使提取腔区域的电子速度与微波相速同步。粒子模拟证明,以上措施有效,在引导磁场强度仅为0.17 T、电子束电压435 kV、电流6.5 kA的条件下,该返波管获得功率为670 MW、效率约为25%的输出微波。相对于常规S波段相对论返波振荡器的磁场系统(B=0.8 T),适用于该返波管的0.17 T低强度磁场系统螺线管外半径下降了20%,能耗下降了约93.8%。 相似文献
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利用电子束轰击快响应荧光屏获得电子束横截面图像的方法,对100 keV大回旋轨道空心电子束(Cusp电子束)在横截面上的束轮廓及电荷密度分布进行了测量,计算出回旋电子束半径、螺旋角等参数,并与相同条件下的计算机数值模拟结果进行了对比和分析。测量结果表明初始磁场强度从0.003 5 T增加到0008 2 T时,电子束的拉莫半径从3.2 mm增加到3.9 mm,螺旋角从0.7增加到1.0,满足使用此电子束的回旋行波放大器的调试需求。 相似文献
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利用3D PIC软件和乌克兰开发的电子光学计算软件TAU对二次谐波回旋行波管Cusp电子枪进行模拟,提取电子的3维运动速度计算横纵速度比。在阳极电压和阴极电流变化的条件下,对电子速度比和速度零散随之而变化的情况进行了模拟,得到平均速度比1.1和平均速度零散9.5%的结果。基于电子平均半径,并根据电子平均半径与横向速度、纵向速度的关系提出了一种实验测量速度比的方法。当电子轰击荧光屏玻璃时,玻璃上的荧光物质感应到光斑,测量空心光斑的平均半径可计算得到电子速度比,其结果与模拟值误差15%。 相似文献
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The electrostatic fluid accelerator (EFA) generates ionic wind with a simple structure that barely obstructs the free air stream or produce excessive noise. This paper presents the velocity characteristics of an EFA under a high speed free air stream to simulate an EFA‐powered propulsor. The results show that when the EFA generates identical velocity to the free air stream, the EFA contributes 25% of the resultant velocity. When the EFA is replaced by a rotary fan that generates identical velocity to the free air stream, the fan contributes only 13.4% of the resultant velocity. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Quantitative analysis of PC MRI velocity maps: pulsatile flow in cylindrical vessels. 总被引:5,自引:0,他引:5
The accuracy of MR phase contrast (PC) velocity mapping, and the subsequent derivation of wall shear stress (WSS) values, has been quantitatively assessed. Using a retrospectively gated PC gradient-echo technique, the temporal-spatial velocity fields were measured for pulsatile flow in a rigid cylindrical vessel. The experimental data were compared with values derived from the Womersley solution of the Navier-Stokes equations. For a sinusoidal waveform, the overall root-mean-square (rms) difference between the measured and analytical velocities corresponded to 13% of the peak fluid velocity. The WSS derived from the data displayed a 14% rms difference with the analytical model. As an example of a more complicated flow, a triangular saw-tooth waveform was deconstructed into its Fourier components. Velocity maps and the WSS were calculated by the superposition of the individual solutions, weighted by the Fourier series coefficient, for each harmonic. The velocity and experimentally derived WSS agreed with the analytical results (4% and 12% rms difference, respectively). Evaluation of the analytical models allowed an estimate of the inherent accuracy in the measurement of velocity maps and WSS values. 相似文献
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The paper describes the influence of the velocity spread of the electrons on the interaction efficiency and on other operational characteristics in the gyro-peniotron oscillator. Numerical simulation shows a drastic efficiency reduction from more than 45% to less than 30% with an electron velocity spread of 10% for a 35GHz, TE03 mode gyro-peniotron operating at the third harmonic. The operation ranges of the device parameters at a defined efficiency level are also decreased when the velocity spread of the electrons increases. 相似文献
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Simultaneous velocity and temperature measurements in gaseous flow fields using the VENOM technique 总被引:1,自引:0,他引:1
We present an initial demonstration of simultaneous velocity and temperature mapping in gaseous flow fields using a new nitric oxide planar laser-induced fluorescence-based method. The vibrationally excited NO monitoring (VENOM) technique is an extension of two-component velocimetry using vibrationally excited NO generated from the photodissociation of seeded NO(2) [Appl. Opt. 48, 4414 (2009)], where the two sequential fluorescence images are obtained probing two different rotational states to provide both velocity and temperature maps. Comparisons to computational fluid dynamics simulations show that the initial VENOM measurements provide good velocity and temperature maps in the relatively high-density regions of the flow, where the rms uncertainties are approximately 5% for velocity and 9% for temperature. 相似文献
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In order to evaluate the bond strength between the reinforcement and concrete after fire damage, a combination of acoustic through-transmission and pull-out tests were used. Previous studies have shown a 25% decrease in the ultrasonic pulse velocity at 90% of the maximum load at room temperature. The specimens were kept in the oven at an elevated temperature for 1, 2, or 3 h. They were then removed and cooled to room temperature. Inspection was conducted using a high-power ultrasonic pulse velocity system while a pull-out load was applied. The correlation between preheated temperature, acoustic wave velocity, and the applied load was analyzed. Initial results show that bond strength and pulse velocity decreased substantially as the temperature or the heating time increased. 相似文献
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Sir Brian Pippard 《Physics in Perspective (PIP)》2001,3(3):258-270
This is an account of measurements of the velocity of light by James Young (1811-1883) and George Forbes (1849-1936) around 1880 based upon an improved version of Fizeau's toothed-wheel method. They presented evidence for a dispersive effect resulting in a difference in the velocity of 1.8% across the visible spectrum. This conflicted with Albert A. Michelson's measurements and prompted discussions by Lord Rayleigh, Arthur Schuster, Léon Gouy, J. Willard Gibbs, and Paul Ehrenfest that led to the conclusion that not the phase velocity but the group velocity was being measured, and that there was no theoretical foundation for Young and Forbes's result. 相似文献
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Laser velocimetries, such as LDV or laser-2-focus (L2F) velocimetry, have been widely used for a flow measurement in a high-speed rotating impeller. A particle image velocimetry (PIV) is one of the popular velocity measurement techniques for the ability to measure a velocity field. And a PIV offers an extensive velocity field in an extremely shorter measurement time than the laser velocimetries. In the present experiment, a PIV was applied to a flow measurement in a transonic centrifugal impeller. A phase locked measurement technique every 20% blade pitch was performed to obtain a velocity field over one blade pitch of the inducer. The measured velocity field at the inducer of impeller clearly showed a shock wave generated on the suction surface of a blade. The validity of the present technique was also discussed. 相似文献