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排序方式: 共有90条查询结果,搜索用时 15 毫秒
1.
Megaelectronvolt ultrafast electron diffraction (UED) is a promising detection tool for ultrafast processes. The quality of diffraction image is determined by the transverse evolution of the probe bunch. In this paper, we study the contributing terms of the emittance and space charge effects to the bunch evolution in the MeV UED scheme, employing a mean-field model with an ellipsoidal distribution as well as particle tracking simulation. The small transverse dimension of the drive laser is found to be critical to improve the reciprocal resolution, exploiting both smaller emittance and larger transverse bunch size before the solenoid. The degradation of the reciprocal spatial resolution caused by the space charge effects should be carefully controlled.  相似文献   
2.
The experimental result of terahertz (THz) coherent transition radiation generated from an ultrashort electron bunching beam is reported.During this experiment,the window for THz transmission from ultrahigh vacuum to free air is tested.The compact measurement system which can simultaneously test the THz wave power and frequency is built and proofed.With the help of improved Martin-Puplett interferometer and Kramers-Krong transform,the longitudinal bunch length is measured.The results show that the peak power of THz radiation wave is more than 80 kW,and its radiation frequency is from 0.1 THz to 1.5 THz.  相似文献   
3.
 宽带脉冲产生器的谐振特性决定了产生电磁脉冲的频谱,分析了带耦合器的同轴1/4波长谐振器在负载为非完全匹配天线时,天线反射对谐振特性的影响。通过建立级联二端口微波网络分析模型,将非匹配负载的反射系数计入等效耦合器反射系数中,得到了输出脉冲及辐射场频谱与负载反射系数的关系式。数值模拟了包括谐振器、耦合器和天线在内的整个宽带脉冲辐射系统,得到的辐射场频谱与理论预期相符。由于负载反射的影响,在中心频率两侧产生了两个副峰,在高功率实验中也观察到了该现象。  相似文献   
4.
The accelerators should be properly designed to make the radiation field produced by beam loss satisfy the dose limits. The radiation field for high intensity H- cyclotron includes prompt radiation and residual radiation field. The induced radioactivity in accelerator components is the dominant source of occupational radiation exposure if the accelerator is well shielded. The source of radiation is the beam loss when cyclotron is operating. In this paper, the radiation field for CYCIAE-100 is calculated using Monte Carlo method and the radioactive contamination near stripping foil is studied. A method to reduce the dose equivalent rate of maintenance staff is also given.  相似文献   
5.
Magnetic bunch compressor is one of the key technologies on the path to next generation accelerator driven facilities. In this paper we report the design principles and the first experimental research of the bunch compressor developed at Chinese Academy of Engineering Physics (CAEP). The length of the bunch after compressor is found to be about 0.7 ps (rms) and the peak current exceeds 500 A when operated in the optimized condition. The sensitivity of the bunch length on the phase of the acceleration field and magnetic field of the bunch compressor was also measured and analyzed.  相似文献   
6.
刘文鑫  唐传祥  黄文会 《中国物理 B》2010,19(6):62902-062902
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   
7.
The accelerators should be properly designed to make the radiation field produced by beam loss satisfy the dose limits. The radiation field for high intensity H cyclotron includes prompt radiation and residual radiation field. The induced radioactivity in accelerator components is the dominant source of occupational radiation exposure if the accelerator is well shielded. The source of radiation is the beam loss when cyclotron is operating. In this paper, the radiation field for CYCIAE-100 is calculated using Monte Carlo method and the radioactive contamination near stripping foil is studied. A method to reduce the dose equivalent rate of maintenance staff is also given.  相似文献   
8.
唐传祥  刘小寒 《中国物理 C》2009,33(Z2):102-104
In this paper, we present the simulation results of a 1.6 cell X-band photocathode RF gun for ultra-low emittance electron beams. It will work at 9.3 GHz. The emittance, bunch length, electron energy and energy spread at the gun exit are optimized at bunch charge of 1pC using PARMELA. Electron bunches with emittance about 0.1 mm·mrad and bunch length less than 100 fs can be obtained from this gun. A PITZ type coupler is adopted in this gun and an initial simulation by MAFIA is also given in this paper.  相似文献   
9.
RF deflecting cavity can be used for bunch length measurement and is designed to diagnose the beam produced by the photocathode electron gun which was built at Tsinghua University for the Thomson scattering experiment. Detailed discussion and calculation for measuring the 3.5 MeV bunch and another with further acceleration to 50 MeV, which is under development, are presented. A standing-wave deflecting cavity working at 2856 MHz is designed and the power feeding system has been planned.  相似文献   
10.
介绍了采用盘圈(DAW)加速结构在11.43GHz下研制的热阴极微波电子枪注入器,分析了注入器中DAW加速结构支撑杆对于微波特性的影响以及加速结构中的模式重叠问题. 针对该结构的强腔间耦合以及次临近耦合不能忽略的特点,对其调谐方法进行了分析研究.给出了该长腔链热阴极微波电子枪注入器的物理设计及粒子动力学计算结果,电子能量为5—6MeV,脉冲流强为40mA,电子束发射度为3.4πmm.mrad. 该微波电子枪的加工焊接已经完成,文中给出了其冷测结果.  相似文献   
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