100 MeV电子直线加速器的物理设计

 能量为100 MeV左右的高性能电子直线加速器是第三代同步辐射光源注入器和自由电子激光注入器的重要组成部分,采用热阴极栅控电子枪、聚束系统和4根SLAC型加速管作为加速器主体结构,一套45 MW的速调管调制器系统和波导系统作为微波功率源系统。设计中,使用了国际通用的模拟软件对加速器的动力学特性进行了数值模拟和参数优化,电子束能量达到100 MeV以上,能散小于1%,归一化发射度小于30 mm·mrad。     

L波段强流单束团注入器的束流动力学计算

自由电子激光器要求高亮度、低能散度的电子束注入波荡器(Undulator)。本文叙述提供高亮度电子束的高频电子直线加速器中的注入器部分的设计计算。注入器由L波段(1300MHz)的十二分频和三分频两个谐振腔预聚束器和一个基波频率的变相速聚束器组成。粒子运动方程中考虑了空间电荷效应和束流负载效应。电子枪的注入参数:脉冲宽度T=4ns;电流I=5A;电子的初始动能E_0=100keV;电子束分布为高斯型。参数优化设计结果:单束团宽度小于25ps,峰值电流达400A以上,电子的平均归一化能量>4,束团内的能量差小于200keV。     

神龙1号加速器束流输运系统研制

神龙1号直线感应加速器由注入器输运段、加速段、聚焦段等3个部分组成。整个束传输线从阴极发射面算起到轫致辐射靶结束，全长约48m，其间数千安培的强流脉冲电子束经过约170mm的二极管加速区，电子能量达到约3．6MeV，再经过4．5m的无加速场漂移区到达注入器出口，随后进入到长38．5m的加速段，在加速段出口时电子能量不低于18MeV；然后进入到长约3．8m的无加速漂移段，经过调整后通过两级磁透镜的聚焦将电子束聚焦到轫致辐射靶上产生X射线。整个束传输线使用了100多个螺线管线圈（包括两个磁透镜）约束电子束的横向发散，     

W–band光注入器的模拟研究

模拟研究了1.6个腔、高梯度的W-band光阴极微波电子枪系统,该系统能产生和加速300pC的电子束团.设计系统由频率91.392GHz光阴极微波电子枪以及频率91.392GHz行波加速结构组成.基于射频直线加速器标度律与数值模拟结果,设计系统能产生能量1.74MeV,电量300pC,束团长度0.72ps,归一化横向发射度0.55mm·mrad的电子束团.研究了高频、高梯度下的束流动力学.由于高梯度,有质动力效应在束流动力学中起重要作用,且由于横向与纵向之间的耦合,在基次空间谐波的情形下,仍然存在着有质动力聚焦效应.     

S波段6 MeV边耦合电子直线加速器的设计研究（英文）北大核心CSCD

近年来,对紧凑、稳定及可靠型电子直线加速器的需求越来越多,其能量主要分布在几百keV到十几个MeV的范围内,其中需求最多的则是能量在MeV量级的微波电子直线加速器。在这种形势下,中国科学院高能物理研究所正在研制一台S波段6 MeV的边耦合电子直线加速器,本文对基于该加速器的模拟计算研究进行了介绍。EGUN和HFSS分别用来设计电子枪和边耦合加速结构。通过将EGUN计算得到的电子束流参数和HFSS计算得到的三维电磁场分布数据引入到PARMELA中,完成了对该加速器的多粒子动力学研究。模拟结果显示,所设计的加速器完全能够满足设计指标的要求。最终,在考虑束流负载效应的因素后,完成了边耦合加速结构的微波结构设计。     

S波段6 MeV边耦合电子直线加速器的设计研究（英文）

近年来,对紧凑、稳定及可靠型电子直线加速器的需求越来越多,其能量主要分布在几百keV到十几个MeV的范围内,其中需求最多的则是能量在MeV量级的微波电子直线加速器。在这种形势下,中国科学院高能物理研究所正在研制一台S波段6 MeV的边耦合电子直线加速器,本文对基于该加速器的模拟计算研究进行了介绍。EGUN和HFSS分别用来设计电子枪和边耦合加速结构。通过将EGUN计算得到的电子束流参数和HFSS计算得到的三维电磁场分布数据引入到PARMELA中,完成了对该加速器的多粒子动力学研究。模拟结果显示,所设计的加速器完全能够满足设计指标的要求。最终,在考虑束流负载效应的因素后,完成了边耦合加速结构的微波结构设计。     

北京自由电子激光装置的设计研究

北京自由电子激光装置(BFEL)是一台工作在中红外区的康普顿型FEL振荡器。由一台30MeV的射频电子直线加速器提供电子束。特点之一是用微波电子枪作为高亮度注入器。本文首先概述了BFEL的一般情形和物理参数.接着用解析公式和模拟的方法论证了电子束的设计目标和激光器的运转特征。最后阐述了BFEL各部分采取的技术路线的特点,内容包括微波枪、加速器和微波系统、调制器、输运系统、摇摆磁铁、光学腔、电子束诊断、准直、自发辐射和激光实验。     

一种在线式电子束能量测量方法

针对直线感应电子加速器中的束流特点,设计了一种在线式电子束能量测量方法。该方法使用分析磁铁和束位置探测器对电子束团切片平均能量进行测量,避免了束团取样带来的误差及测量过程对束流的影响,可以实现电子能量的在线测量。使用该方法对某强流直线感应电子加速器的电子束团能量进行了测量,获得了电子束团切片平均能量随时间变化的曲线,能量测量不确定度为0.177 MeV,能散度测量不确定度为0.39%。     

BEPCⅡ正电子源

BEPCⅡ是一粒子工厂型的正负电子对撞机,为北京正负电子对撞机(BEPC)的改造、升级工程. 它对直线注入器的基本要求是40mA,1.89GeV的正电子束流,发射度1.6μm,能散度好于±0.5%, 保证储存环的注入速率≥50mA/min, 实现TOP OFF注入方式. 因为正电子流强与打靶电子束流功率成正比,采用一把新的10A电子枪来提高打靶电流, 采用新加速结构和65MW速调管SLAC5045把目前140MeV的打靶能量提高到240MeV. 正电子源本身也是一非常关键、极其复杂的系统, 它包括正电子转换靶室、12kA``磁号'脉冲电源、7m长聚焦节、大功率直流电源和支架等. 目前,正电子产生加速器,从电子枪直到正电子源,已经安装到了BEPC直线加速器隧道. 本文将着重介绍正电子源系统的设计、加工和测试.     

多聚焦极栅控电子模拟源的研究

采用电子光学软件设计模拟了一种长焦距多聚焦级的电子枪结构.利用电子透镜原理分析多聚焦极电子枪的电子束斑产生,依据不同栅控电压,分析零场模式、拒斥场模式和肖特基场模式3种阴极电子发射方式下电子聚焦情况.模拟结果表明:拒斥场模式和肖特基场模式对电子束流密度分别有减弱和增强的作用;当聚焦极电压比U1∶U2∶U3∶U4∶U5=5∶8∶15∶70∶100时,能量为30keV的电子束焦斑最小,在10m处焦斑大小为160mm.     

BEPCⅡ Positron Source

BEPCⅡ— an upgrade project of the Beijing Electron Positron Collider (BEPC) is a factory type of e^＋e^－ collider. The fundamental requirements for its injector linac are the beam energy of 1.89GeV for on-energy injection and a 40mA positron beam current at the linac end with a low beam emittance of 1.6μm and a low energy spread of ±0.5% so as to guarantee a higher injection rate (≥50mA/min) to the storage ring. Since the positron flux is proportional to the primary electron beam power on the target, we will increase the electron gun current from 4A to 10A by using a new electron gun system and increase the primary electron energy from 120MeV to 240MeV. The positron source itself is an extremely important system for producing more positrons, including a positron converter target chamber, a 12kA flux modulator, the 7m focusing module with DC power supplies and the support. The new positron production linac from the electron gun to the positron source has been installed into the tunnel. In what follows, we will emphasize the positron source design, manufacture and tests.     

BXERL photo-injector based on a 217 MHz normal conducting RF gun

The Beijing X-ray Energy Recovery Linac (BXERL) test facility is proposed in Institute of High Physics (IHEP). In this proposal, the main linac requires the injector to provide an electron beam with 5 MeV energy and 10 mA average current. An injector based on DC gun technology is the first candidate electron source for BXERL. However, the field emission in the DC gun cavity makes it much more difficult to increase the high voltage to more than 500 kV. Another technology based on a 217 MHz normal conducting RF gun is proposed as the backup injector for this test facility. We have designed this RF gun with 2D SUPERFISH code and 3D MICROWAVE STUDIO code. In this paper, we present the optimized design of the gun cavity, the gun RF parameters and the set-up of the whole injector system. The detailed beam dynamics have been done and the simulation results show that the injector can generate electron bunches with RMS normalized emittance 1.0 uppi mmcdotmrad, bunch length 0.77 mm, beam energy 5.0 MeV and energy spread 0.60%.     

Physics design of a 10 MeV, 6 kW travelling wave electron linac for industrial applications

We present the physics design of a 10 MeV, 6 kW S-band (2856 MHz) electron linear accelerator (linac), which has been recently built and successfully operated at Raja Ramanna Centre for Advanced Technology, Indore. The accelerating structure is a 2π/3 mode constant impedance travelling wave structure, which comprises travelling wave buncher cells, followed by regular accelerating cells. The structure is designed to accelerate 50 keV electron beam from the electron gun to 10 MeV. This paper describes the details of electromagnetic design simulations to fix the mechanical dimensions and tolerances, as well as heat loss calculations in the structure. Results of design simulations have been compared with those obtained using approximate analytical formulae. The beam dynamics simulation with space charge is performed and the required magnetic field profile for keeping the beam focussed in the linac has been evaluated and discussed. An important feature of a travelling wave linac (in contrast with standing wave linac) is that it accepts the RF power over a band of frequencies. Three-dimensional transient simulations of the accelerating structure along with the input and output couplers have been performed using the software CST-MWS to explicitly demonstrate this feature.     

Future developments of INFN-LNL nuclear beam facilities

The accelerator group at INFN-LNL has been mostly engaged, recently, in completing and commissioning the higher current injector of the linac booster ALPI (named PIAVE) and in constructing and assembling the front-end part of a high current driver linac for the RNB facility SPES. PIAVE, designed to accelerate ions with A/Q = < 8.5 up to 1.2 MeV/u, is now completed. The injector has been commissioned with O, Ar, Ne and Xe beams. Neon and argon beams have been delivered to experiments for a total of about 400 hours. A consolidation program of PIAVE and ALPI is planned, so as to deliver a larger variety of beams with a current range  pnA and with an energy exceeding the Coulomb barrier in relevant nuclear reaction cases. The RNB facility SPES, allowing a frontier program in RNB physics, is being designed and prototyped: beams of neutron rich medium-to-heavy mass nuclei will be produced inducing ²³⁸U fission with a 40 MeV 200μA proton beam impinging onto a multi-slice direct target. A further development of ALPI will make it best suitable for the re-acceleration of radioactive nuclear species, after charge breeding and isotope selection.     

The design simulation of the superconducting section in the ADS injector Ⅱ

The high-current superconducting proton linac is being studied for the accelerator-driven system (ADS) project undertaken by the Chinese Academy of Sciences. The injector Ⅱ will be operated at 162.5 MHz, and the proton out from the RFQ with an energy of 2.5 MeV will be accelerated to 10 MeV by two cryo-modules, which are composed of eight superconducting half wave resonance cavities and nine solenoids. In this paper, the design and beam simulation of the superconducting section of the injector Ⅱ, the acceptance calculation and a stability analysis are presented.     

CRRFA-30L波段射频加速器

 主要介绍CRRFA-30L波段射频加速器结构和性能，论述了热阴极射频腔注入器、束流加速系统、微波功率源和控制等结构中主要技术及其研究进展，给出了加速器输出束流参数测量与测量结果分析，达到设计应用要求。     

The ISAC post-accelerator

The acceleration chain of the ISAC facility boosts the energy of both radioactive and stable light and heavy ions for beam delivery to both a medium energy area in ISAC-I and a high energy area in ISAC-II. The post-accelerator comprises a 35.4 MHz RFQ to accelerate beams of A/q ≤ 30 from 2 keV/u to 150 keV/u and a post stripper, 106.1 MHz variable energy drift tube linac (DTL) to accelerate ions of A/q ≤ 6 to a final energy between 0.15 MeV/u to 1.5 MeV/u. A 40 MV superconducting linac further accelerates beam from 1.5 MeV/u to energies above the Coulomb barrier. All linacs operate cw to preserve beam intensity.