Electron Gun for Powerful Short Pulse Gyrotron with Operating Magnetic Field 8 T

High power short pulse gyrotron with operating frequency 395 GHz operating on the second cyclotron harmonic is now under developing at FIR FU. The gyrotron is planned to use in future experiments for plasma diagnostics. For this purpose the output power about 100 kW and pulse duration 100 ns at least are needed. Preliminary estimations of parameters of some versions of the electron guns with accelerating potential U₀= 70-100 kV were performed. Possibilities of non-adiabatic as well as adiabatic guns were considered. It was shown that non-adiabatic system is not reliable for such rather low value of U₀, the adiabatic magnetron injection gun (MIG) is more preferable for the gyrotron design. Analytical estimations of the suitable MIG dimensions and operating regime to form good quality electron beam were fulfilled. Numerical optimization of the gun shape and position was performed. It was shown that in spite of the extremely big ratio of the operating current (I₀= 18 A) to the Langmuir current of the gun, close to 0.4-0.5, the suggested MIG can form the helical electron beam (HEB) which is suitable for gyrotron operation properties.     

Electron Gun for Powerful Large Orbit Gyrotron

In the article, results of numerical simulation of the gun with the cusp of magnetic field are presented. Short pulse version of the gun with explosion emission is investigated. Some preliminary analytical estimation of the beam and gun parameters are performed. Then, numerical optimization of the electrodes shape as well as magnetic field distribution is carried out. For preliminary separation of electrons and formation of the rectilinear beam, anode diaphragm is installed. After then, additional selection of electrons for decreasing the ripple is performed. For this purpose, channel walls are used for interception of some part of the electron beam. Reverse of the magnetic field in the diode part of the gun is formed. So, the formation of the rectilinear beam is combined with the region, where electrons obtain initial gyration energy. To prevent the disperse action of the own beam space charge forces, the system with big gradient of magnetic field (about 0.5-1 kGs/mm) is needed. According to results of the simulation, helical electron beam can be performed even at total compression ratio about 1000 and current density more than 50 kA/cm². The designed electron gun provides acceptable performance for the large orbit gyrotron, such as operating current close to 300 A, the pitch-factor value about 1.5-1.7, deviation of the guiding centers from the axis (the ripple) /10 and /6 for operation on 3-rd and 5-th cyclotron harmonic correspondingly (wavelength =0.5 and 0.3 mm) and velocity spread within the range 10-15%.     

Design of Cavities for a Short Pulse Powerful Large Orbit Gyrotron

Designs of cavities for fundamental and high harmonic operation in Large Orbit Gyrotron (LOG) are discussed. The fundamental operation allows one to use beam currents in the range from 200 A to 300 A achieve output power of the order of 9–10 MW at frequency 143.6 GHz. Mode competition calculations show that stable oscillations in the TE^1,4 mode using high beam currents are possible even with the pitch factor 1.3 which is significantly lower than the design value 1.55. For the second harmonic operation, the maximum current used for excitation of the TE^2,4 mode is 60 A and the optimum magnetic field is 7.6 T. A cavity design for fourth harmonic operation using the TE^4,4 mode is also presented.     

Design of a Large Orbit Gyrotron with a Permanent Magnet System

The paper presents results of numerical analysis and outlines the computer-aided design of a novel high-harmonic gyrotron with a beam of electrons gyrating along axis-encircling trajectories. The electron beam is formed by a novel electron-optical system (EOS) based on an electron gun of diode type with thermionic cathode and gradual reversal of the magnetic field. The results of numerical simulations predict satisfactory performance of the EOS and appropriate beam quality parameters. The tube design allows one to install different cavities optimized for excitation of TE_4,1 mode at the fourth harmonic of the cyclotron frequency or TE_3,1 mode at the third one. The target parameters of the device are: frequency about 112 GHz; output power near 1 kW and efficiency of several percent.     

Numerical Analysis of Weakly Relativistic Large Orbit Gyrotron with Permanent Magnet System

High-harmonic gyro-devices with axis-encircling electron beams known as large orbit gyrotrons (LOG) represent an appealing alternative to the conventional gyrotrons. In this paper we investigate the feasibility of such device operating with low current and low energy electron beams formed by a novel electron gun with a permanent magnet system. The results from the numerical experiments indicate the possibility to excite TE₄₁ mode at fourth harmonic of the cyclotron frequency. Simulations predict generation of microwave radiation with frequency 104 GHz and output power near 1 kW.     

Gyrotron Electron Beams: Velocity and Energy Spread and Beam Instabilities

The stability of the electron beams and maximum share of the electrons oscillatory energy, i.e. finally efficiency, power, and pulse duration of the gyrotron to a considerable extent depend on the velocity and the energy spread (VESP) of the HEB. The basic factors determining VESP in the helical beams are discussed. Among these factors static (initial velocities, cathode heterogeneities, space charge fields) and dynamic (negative mass and diochotron instabilities and a global instability connected with the capture of the electrons in the gyrotron adiabatic trap) factors are considered. Qualitative models of the excitation of the space charge oscillation as well the parasite electromagnetic radiation of the HEB are developed. Some experimental data of the investigation of the parasitic electromagnetic radiation spectrum in one gyrotron are discussed. The methods of the experimental investigation of the VESP are described.     

BEPC实验电子枪系统的研究

E5-4实验电子枪系统是BEPC电子枪系统的改进版本，文中首先对其进行了理论分析，并介绍了利用Y796阴栅组件和新的电源及Pulser系统进行测试的结果，分析了各个参数对束流的影响，给出了电子枪流强与直流高压、pulser 电压、栅偏压、阴极参数等的关系曲线，对BEPCII电子枪系统的研制和调试起到了重要的指导作用.     

Simulation of a High Harmonic Gyrotron with Axis-Encircling Electron Beam and Permanent Magnet

A computer code for simulation of beam-field interaction in a resonant cavity of a gyrotron has been developed. It is based on a self-consistent, time-independent, single-mode physical model. The code has been applied to the analysis of the electrodynamical system of a novel high-harmonic gyrotron with axis-encircling beam and a permanent magnet. In this paper both the physical model and numerical techniques used are outlined. Some results of the numerical experiments are presented and discussed.     

Computer Simulation of Axis-Encircling Beams Generated by an Electron Gun with a Permanent Magnet System

Results from computer aided design of a novel electron gun generating axis-encircling beams are presented and discussed. Numerical experiments were performed by the new version of the software package GUN-MIG named GUN-MIG/CUSP. It is based on a self-consistent relativistic model and is developed as a problem oriented tool for analysis of electron-optical systems with magnetron injection guns (MIG) and electron guns with field reversal (cusp guns), forming axis-encircling beams. As a result of the simulations an electron-optical design of a novel electron gun with permanent magnet system was accomplished. The gun is expected to form high quality beams with small velocity spread and beam ripple. Parameters of the generated beams are appropriate for a prospective weakly relativistic high harmonic large orbit gyrotron (LOG). The development of such device is in progress now at the Research Center for Development of Far-Infrared Region (FIR Center) at Fukui University.     

铁电介质阴极电子枪

给出并分析了铁电介质阴极电子枪的初步数值模拟和实验结果。实验表明其发射电子密度可达110A/cm2。该种电子枪产生的电流密度大于阴极发射电子初始能量为零时的空间电荷限制电流,PIC数值模拟结果表明可以通过给发射电子赋予一定的初始能量来解释这一现象,理论分析认为铁电介质阴极发射电子具有初始能量是合理的。     

铁电介质阴极电子枪

 给出并分析了铁电介质阴极电子枪的初步数值模拟和实验结果。实验表明其发射电子密度可达110A/cm²。该种电子枪产生的电流密度大于阴极发射电子初始能量为零时的空间电荷限制电流,PIC数值模拟结果表明可以通过给发射电子赋予一定的初始能量来解释这一现象,理论分析认为铁电介质阴极发射电子具有初始能量是合理的。     

BEPCⅡ电子枪系统测试与运行

2004年7月BEPCⅡ新电子枪系统在测试台进行了测试, 同年11月投入BEPCⅡ直线加速器运行. 描述了新电子枪系统的测试与运行状态. 电子枪设计电流10A, 脉宽1ns,重复频率50Hz, 脉冲高压200kV, 提供单脉冲和双脉冲运行模式. 通过实验获取了一些重要的关系曲线, 同时进行了初步的双脉冲测试. 流强及发射度测量等测试结果表明设计阶段的计算机模拟数据与实际情况基本相符. 从电子枪实际运行状况来看, 其设计与制造是成功的.     

200kV电子帘加速器的电子束轨迹的计算

采用法国的MAFIA程序计算电场.编制了TRAJ程序,用逐点跟踪计算电子轨迹,得到了束流包络.观察了在高压电场中栅压对束流光学传输的影响,并获得了在不同能量范围内的栅压聚焦作用,为栅压调节提供了理论依据,也为将来对其它规格的电子帘加速器的物理设计积累了十分宝贵的经验.     

Design of a Quasi-Optical System Converting the TE06 Output Mode of a Gyrotron into a Gaussian-Like Beam

Gaussian optics can be used to design a quasi-optical system converting the TE₀₆ mode output (f=388 GHz) of a submillimeter wave gyrotron into a well-collimated, linearly-polarized free-space beam with a circular cross-section. A quasi-optical antenna produces a main beam with an elliptical cross-section, which is then converted by two mirrors into a well-collimated beam with a circular cross-section.     

Design of a Quasi-Optical System to Convert TE0n Mode Outputs of a Gyrotron into Gaussian Beams

In this paper we present a novel design of a quasi-optical system for conversion of gyrotron outputs into gaussian beams. It consists of a quasi-optical antenna, four focusing mirrors (parabolic cylinders) and a filter which removes the side lobes of the beam. The system is capable to convert three TE_0n mode outputs into gaussian beams with waist size of 16.7 mm as well as four TE_1n mode outputs into bi-gaussian beams with waist size of 10.9 mm in width and 16.5 mm in length.     

大回旋cusp电子注数值模拟

新一代宽带、高增益、大功率回旋行波管需要新型的电子注,而大回旋cusp电子注为其实现提供了可能。对大回旋cusp电子注进行系统理论分析,建立了大回旋cusp电子注的物理模型,在理论分析基础上进行了大量数值计算和模拟优化,并对大回旋cusp电子枪设计中的影响因素进行探讨。设计出一支低速度零散、高速度比、低纹波,适用于高次谐波的高功率(54 kV, 2.7 A)cusp电子枪。     

A Self-Organised Bilocal Magnetic Field in the Electron Plasma of Metals

Within the simplest model of metals, namely a gas of electrons with Coulomb interactions, in the presence of a uniform background of positive charge to enforce electric neutrality of the system, we have derived a mechanism by which the Coulomb interaction between the electrons generates a new kind of magnetism. The ground state of the metal is represented by a magnetically ordered state described by a non-local magnetic field. This non-local magnetic field does not produce spin polarisation of electrons, but induces a special long range correlation between electrons of opposite spin. This mechanism results in a theoretical value for the binding energy per electron, which is lower than the corresponding value for the unmagnetised state of the metal. The new magnetic order, proposed and analysed theoretically here, can in principle be experimentally tested.     

微脉冲电子枪模拟计算

用模拟计算的方法,研究了微脉冲电子枪的束流动力学行为.基于微脉冲电子枪的工作原理和束流动力学特点,用VC++语言编制了微脉冲电子枪的辅助设计软件—SEEG对微脉冲电子枪中电子的三维运动进行多粒子跟踪模拟.文中给出了模拟计算的基本原理,经过SEEG程序稳定性的测试,最后应用SEEG程序模拟了一个微脉冲电子枪的束流运动特性.     

基于碳纳米管场致发射的电子枪的初步研究

给出了基于碳纳米管场致发射电子枪的初步研究结果. 碳纳米管场致发射试验证明碳纳米管是一种很好的场致发射材料. 试验中, 在极间场强2.7MV/m的情况下得到的电流发射密度为0.5mA/cm².     

Efficiency Enhancement of Coaxial-Cavity Electron Cyclotron Resonance Maser by Tapering Guide Magnetic Field

A coaxial-cavity cyclotron resonance maser (CRM) oscillator with tapered guide magnetic field is proposed. It is shown that the transmission quality can be improved by tapering the guide magnetic field. Simulation indicates that the efficiency of a millimeter-wave gyrotron oscillator may be reached up to 38.7% by optimizing the tapered magnetic field.