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1.
Characteristics of terahertz coherent transition radiation generated from picosecond ultrashort electron bunches 下载免费PDF全文
This paper presents a method of generating terahertz (THz)
coherent transition radiation (CTR) from picosecond ultrashort
electron bunches including single and train bunches, which are
produced by a photocathode radio frequency gun. The radiation
characteristics of THz CTR including formation factor and energy
spectrum are analysed in detail. With the help of a 2-dimensional
particle-in-cell simulation, the radiation characteristics including
power, energy and magnetic field are analysed. The results show that
the radiation frequency can be adjusted by tuning the repetition
frequency of the train bunch and the energy can be enhanced with the
train bunches. 相似文献
2.
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
3.
David Tzach Robert Buschauer Gregory Benford 《International Journal of Infrared and Millimeter Waves》1981,2(1):71-82
After eliminating reflections from the walls of the plasma container, we observed polarization of the coherent synchrotron radiation from a relativistic electron beam rotating in a plasma. Several features of the polarization agree well with calculations based on the single particle synchrotron radiation theory. A particular polarization ratio (Fig. 3) does not, however. We deduce from this direct diffraction of the radiation by the beam electrons. This is strong evidence for beam-particle bunches of size cm. Also, there must be some absorption of the extraordinary wave to account for the observations. We suggest a way to apply these results to measure the pitch angle of the beam.Work supported by Army Research Office. 相似文献
4.
光学渡越辐射具有良好的方向性,通过对光学渡越辐射空间分布曲线进行拟合可以对束流发散角进行计算。采用理论计算的方法,分析了电子入射到金属-介质界面时,入射角变化对光学渡越辐射二维空间分布的影响。计算分析表明,光学渡越辐射在特定偏振方向上的分布并不仅仅由电子束在该方向的发散角分量决定,同时还受到其他方向发散角分量的影响。计算对比了电子束散角一维分布和二维分布模型下光学渡越辐射空间分布的差异。结果表明,采用一维分布模型拟合计算的电子束均方根发散角存在偏差,较二维分布拟合结果偏小。 相似文献
5.
Influence of spatiotemporal coupling on the capture-and-acceleration-scenario vacuum electron acceleration by ultrashort pulsed laser beam 下载免费PDF全文
This paper investigates the properties of the ultrashort pulsed beam aimed to the
capture-and-acceleration-scenario (CAS) vacuum electron acceleration. The result
shows that the spatiotemporal distribution of the phase velocity, the longitudinal
component of the electric field and the acceleration quality factor are
qualitatively similar to that of the continuous-wave Gaussian beam, and are slightly
influenced by the spatiotemporal coupling of the ultrashort pulsed beam. When the
pulse is compressed to an ultrashort one in which the pulse duration TFWHM
<5T0, the variation of the maximum net energy gain due to the
carrier-envelope phase is a crucial disadvantage in the CAS acceleration process. 相似文献
6.
One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the intense electron-beam produced by a linear induction accelerator. The system features two characteristics. The first one concerns the system synchronization signal triggered by the following edge of the main output waveform from a Blumlein switch. The synchronous precision of about 1 ns between the electron beam and the image capture time can be reached in this way so that the electron beam emittance at the desired time point can be obtained. The other advantage of the system is the ability to obtain the beam spot and beam divergence in one measurement so that the calculated result is the true beam emittance at that time, which can explain the electron beam condition. It provides to be a powerful beam diagnostic method for a 2.5 kA, 18.5 MeV, 90 ns (FWHM) electron beam pulse produced by Dragon I. The ability of the instantaneous measurement is about 3 ns and it can measure the beam emittance at any time point during one beam pulse. A series of beam emittances have been obtained for Dragon I. The typical beam spot is 9.0 mm (FWHM) in diameter and the corresponding beam divergence is about 10.5 mrad. 相似文献
7.
One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the intense electron-beam produced by a linear induction accelerator. The system features two characteristics. The first one concerns the system synchronization signal triggered by the following edge of the main output waveform from a Blumlein switch. The synchronous precision of about 1 ns between the electron beam and the image capture time can be reached in this way so that the electron beam emittance at the desired time point can be obtained. The other advantage of the system is the ability to obtain the beam spot and beam divergence in one measurement so that the calculated result is the true beam emittance at that time, which can explain the electron beam condition. It provides to be a powerful beam diagnostic method for a 2.5 kA, 18.5 MeV, 90 ns (FWHM) electron beam pulse produced by Dragon I. The ability of the instantaneous measurement is about 3 ns and it can measure the beam emittance at any time point during one beam pulse. A series of beam emittances have been obtained for Dragon I. The typical beam spot is 9.0 mm (FWHM) in diameter and the corresponding beam divergence is about 10.5 mrad. 相似文献
8.
Terahertz radiation from interaction between an electron beam and a planar surface plasmon structure 下载免费PDF全文
The possibility of an electron beam exciting surface plasmons in
conducting metal is discussed in this paper. A planar
perfect-structure with subwavelength holes is proposed. The
phenomenon that mimicking
surface plasmon waves can be excited and amplified by an electron
beam is proved theoretically and numerically. The mechanism of transmission through a subwavelength hole
array is exploited to enhance the interaction between the electron beam
and the mimicking surface plasmons. 相似文献
9.
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
10.
《Physics letters. A》2020,384(16):126321
We have studied the possibilities of using diffracted transition radiation excited by a relativistic electron beam in a single-crystal target to determine the beam divergence. For this purpose, we investigated the expressions we had previously derived that describe the angular density of diffracted transition radiation excited by a relativistic electron beam crossing a thin single-crystal plate. In our calculations, we used the two-parameter model distribution function to represent the angular distribution of ultra-relativistic electrons in the beam. For determining the beam divergence parameters, the methods of two-dimensional objective function minimization were used. The model calculations we performed confirm the efficiency of the above-mentioned methods for determining the divergence of a relativistic electron beam. 相似文献
11.
12.
利用OMA光学多道分析仪测量了激光与薄膜靶相互作用中产生的辐射光谱,在靶后观察到红移的二次谐波发射. 这种二次谐波是v×B加热产生的、具有微脉冲结构的超热电子束在等离子体-真空边界产生的相干渡越辐射(CTR). 随着激光能量的增大,红移峰向长波方向移动,光谱同时发生展宽. 分析认为,等离子体临界面的迅速膨胀是导致二次谐波红移的主要原因. 随着预脉冲能量的增大,临界面膨胀速度增大,导致了发射峰更大的红移. 实验还测量了靶面法线方向的辐射光谱,观察到基频辐射的红移和展宽. CTR为诊断临界面的运动方向和速度提供了一种新的方法.
关键词:
相干渡越辐射
超热电子
超短超强激光
等离子体相互作用 相似文献
13.
Kramers-Krönig(K-K)变换方法被广泛地应用于频域测量中还原超短电子束团分布,成为分析电子束团形状、长度等参量的有效工具. 研究发现,利用该方法分析电子束参量时,自相干曲线基底的选择、低频损耗与高频截止及插值外推位置的选择,对束团参量有重要的影响. 以清华大学加速器实验平台采用相干渡越辐射测试束团长度为例,分析了上述参量的选取对测量结果的影响,讨论了选择K-K变换的关键物理参量的方法.
关键词:
Kramers-Krönig变换
频域测量
超短电子束团
相干渡越辐射 相似文献
14.
Generally, a standard bunching system is composed by an SW pre-buncher, a TW buncher and a standard accelerating section. However, there is one way to simplify the whole system to some extent by using the hybrid buncher, which is a combined structure of the SW pre-buncher and the TW buncher. Here the beam dynamics studies on an S-band bunching system with the hybrid buncher is presented, and simulation results show that similar beam performance can be obtained at the linac exit by using this kind of bunching system rather than the standard one. In the meantime, the structure design of the hybrid buncher is also described. Furthermore, the standard accelerating section can also be integrated with the hybrid buncher, which can further simplify the usual bunching system and lower the construction cost. 相似文献
15.
16.
为了探索超热电子的输运过程,在100 TW掺钛蓝宝石飞秒激光器上利用光学CCD相机和OMA光学多道分析仪,分别在靶背表面法线方向测量了光发射空间分布图案和光谱. 实验测量结果显示,光发射空间分布图案呈圆盘状,在圆盘中明亮而强的光信号呈局部化分布,该现象表明,超热电子在输运的过程中存在成丝效应,引起严重的不稳定性;光发射光谱在3倍频和3/2倍频附近出现尖峰,分别是3次谐波和3/2次谐波,这一现象归因于超热电子束在传输的过程中产生的微束团而引起的相干渡越辐射(CTR);光发射光强随靶厚度的增加而减小.
关键词:
超热电子
相干渡越辐射
输运
不稳定性 相似文献
17.
18.
为了探索超热电子的加热机制,利用光学CCD相机和OMA光学多道分析仪,分别在靶背法线方向测量了光学渡越辐射(OTR)积分成像图案和光谱。实验在100 TW掺钛蓝宝石激光器上进行,飞秒激光与铜膜靶作用后,靶表面发光信号由空间分辨装置聚焦成像并引到CCD或OMA谱仪的狭缝上。测得的积分成像图案呈圆环状,光斑形成区域直径约为225 μm,在圆环边缘附近出现局部化明亮光信号,该现象表明,超热电子在传输的过程中存在成丝效应,其分布也不均匀。光谱在300~500 nm之间出现一系列非周期锐利尖峰,在400 nm(2ω0)附近出现的尖峰应归因于v×B加热机制产生的超热电子引起的相干渡越辐射(CTR)。 相似文献
19.
Based on the dynamic diffraction theory [1], coherent x-ray radiation of a relativistic electron crossing a single-crystal plate at a constant velocity is considered
in the Bragg geometry. In the general case of asymmetric reflection of the radiation from the target, expressions are derived
for the spectral-angular distribution of parametric x-ray radiation (PXR) and diffraction transition radiation (DTR). For
a fixed angle between the electron trajectory and the system of parallel atomic planes of the crystal (Bragg’s angle) it is
shown that a decrease in the angle of electron incidence on the crystal plate gives rise to a significant increase in the
PXR and DTR spectra, and the causes for spectral broadening for each of these radiation mechanisms are different.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 74–83, March, 2009. 相似文献
20.
匀速运动的带电粒子在穿过具有不同介电常数的两种媒质界面时要产生所谓光学渡越辐射。该辐射在粒子的入射平面上呈偏振行为;从辐射强度的角分布可以确定入射粒子的能量。在入射到双膜系统的情况下,由于干涉的发生,在第二膜前表面的强度角分布有振荡行为。利用这些现象,可对脉冲电子束包络半径、束电流密度的横向分布,束能量以及横向散角进行测量,依照这一原理在各LIA加速器上进行的脉冲电子束参数测量,获得的有效数据极大地提高了加速器的调试效率。 相似文献