Preliminary design of high-power wave-guide/transmission system for multimegawatt CW requirements of 100 MeV proton LINAC

Development of a 100 MeV CW proton LINAC has been planned at CAT. This LINAC will be needing CW rf power in the frequency ranges of 350 MHz and 700 MHz for its RFQ and DTL/CCDTL/SFDTL structures respectively. The power to the accelerating structures will be produced by either 1 MW CW or 250 kW CW klystrons/inductive output tubes (HOM IOTs). The power needed by respective feed points in the structure is max. 250 kW which will be powered by splitting the power from 1 MW klystron/klystrode into four channels by using a wave-guide system. In case of using 250 kW tubes the power to the structures will be provided directly from each tube. Two types of wave-guide transmission system have been considered, viz, WR 2300 for 350 MHz rf needs and WR 1500 for 700 MHz rf needs. The typical wave-guide system has been designed using the 1 MW CW klystron followed by wave-guide filter, dual directional coupler, high-power circulator, three 3 dB magic TEE power dividers to split the main channel into four equal channels of 250 kW each. Each individual channel has dual directional couplers, flexible wave-guide sections and high power ceramic vacuum window. The circulator and each power divider is terminated into the isolated ports by high power CW loads. Out of the four channels three channels have phase shifters. Present paper describes the technological aspects and design specifications-considerations for these stringent requirements.     

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。     

中国散裂中子源二期双spoke超导腔设计

中国散裂中子源是中国第一台、世界第四台脉冲型散裂中子源,其已于2020年2月达到100 kW功率的设计指标,运行稳定高效,供束效率位于国际前列。中国散裂中子源二期升级方案中总束流功率将升级到500 kW,其中直线加速器段将采用超导加速腔结构,束流能量由80 MeV提高到300 MeV。其中在80～165 MeV能量段采用324 MHz双spoke超导腔,在165～300 MeV能量段采用648 MHz 6-cell椭球超导腔。采用CST、COMSOL等仿真软件完成324 MHz双spoke超导腔的电磁、机械设计及优化,达到实际运行指标要求。为了提高腔运行的稳定性,在腔的设计中对E_P/E_acc着重进行了优化,使其尽量降低。     

Progress on the construction of the 100 MeV/100 kW electron linac for the NSC KIPT neutron source

IHEP, China is constructing a 100 MeV/100 kW electron Linac for NSC KIPT, Ukraine. This linac will be used as the driver of a neutron source based on a subcritical assembly. In 2012, the injector part of the accelerator was pre-installed as a testing facility in the experimental hall ≠2 of IHEP. The injector beam and key hardware testing results met the design goal. Recently, the injector testing facility was disassembled and all of the components for the whole accelerator have been shipped to Ukraine from China by the ocean shipping. The installation of the whole machine in KIPT will be started in June, 2013. The construction progress, the design and testing results of the injector beam and key hardware are presented.     

Emission Time Measurements of Light Particles from 40Ar+197Au Collisions in Intermediate Energies

Particle-particle correlation functions have been measured for ⁴⁰Ar+¹⁹⁷Au collisions at E=25 MeV/u.Emission time of light particles has been extracted from correlation functions using the three-body trajectory model.The average emission time varies with the energy of particles. It decreases from about 300 fm/c for low energy particles to about 100fm/c for energetic particles.     

中能区40Ar+197Au反应中轻粒子的发射时间测量

本文报道了25MeV/u ⁴⁰Ar+¹⁹⁷Au反应中粒子-粒子关联函数的实验结果.利用三体弹道模型从关联函数提取了轻粒子发射时间.轻粒子的平均发射时间随粒子能量而变化,从低能时的约300fm/c下降至高能时的约100fm/c.     

Results on two-, three-, and four-body events from the100Mo+100Mo and120Sn+120Sn collisions aroundE/A=20 MeV

Events with 2, 3 and 4 heavy-fragments (A≧20) have been detected in the reactions¹⁰⁰Mo+¹⁰⁰Mo atE/A =18.7, 23.7 MeV and¹²⁰Sn+¹²⁰Sn atE/A=18.4 MeV. The experiments were performed with an array of 12 detectors which together covered a large fraction of the forward hemisphere and allowed a high detection efficiency for these events. Masses and energies of all fragments have been reconstructed by means of an improved version of the kinematic coincidence method. The probabilitiesP ₃ andP ₄ of producing 3- and 4-body events were found to depend mainly on the dissipated energy rather than on the bombarding energy, thus indicating that their origin lies more in the decay properties of the excited fragments than in the dynamics of the interaction. Emission of light particles from the composite system is shown to become more relevant with increasing bombarding energy and may explain the drop of theP ₃ andP ₄ curves at high energy losses. Small deviations of theP ₃ andP ₄ curves at 23.7A · MeV from those at lower bombarding energies were used to estimate the amount of a possible pre-equilibrium light particle emission as a function of impact parameter.     

Isovector quadrupole resonance observed in the 60Ni(13C,13N)60Co reaction at E/A=100 MeV

The charge-exchange reaction 60Ni(13C,13N)60Co at E/A=100 MeV has been studied to locate isovector (deltaT=1) non-spin-flip (deltaS=0) giant resonances. Besides the giant dipole resonance at E(x)=8.7 MeV, another resonance has been observed at E(x)=20 MeV with a width of 9 MeV. Distorted-wave Born approximation analysis on the angular distribution clearly indicated the L=2 multipolarity, attributing the E(x)=20 MeV state to the giant isovector quadrupole resonance.     

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.     

Emission of helium nuclei in heavy ion interactions at energies ≧ 100 MeV/nucleon

The energy and angular distributions of helium particles emitted in interactions between nuclei in the cosmic radiation and nuclei in photoemulsions at energies ≧ 100 MeV/nucleon have been studied. The data obtained is impossible to interpret on the basis of a statistical decay of excited nuclei. For example, it is found that more than 28% of the helium nuclei are emitted in processes different from simple evaporation. The differential energy distribution of the helium nuclei in the energy interval (40–200) MeV can be represented by the relationN(E)dE=constE ^?a dE, wherea≈1.2. The large spread in angles and energies of the fast helium particles emitted in heavy ion interactions can to a certain degree be understood, if it is assumed that interactions between nucleons and clusters of nucleons occur.     

Collective transitions in 100Mo and the mixed configuration IBM

The electromagnetic decay properties of levels in ¹⁰⁰Mo have been studied by Coulomb-excitation yield measurements and lifetime determinations. For the yield measurements thin targets of ¹⁰⁰Mo were bombarded with beams of ¹⁶O and ³²S at 42 and 89 MeV incident energy, respectively. The emitted γ-rays were observed in coincidence with particles detected in a position-sensitive gas proportional counter. In a separate experiment the recoil-distance method was used to determine the lifetimes of levels in ¹⁰⁰Mo excited in the bombardment of a thin target with a ⁵⁸Ni beam of 185 MeV energy. Matrix elements for the observed transitions were deduced from the particle-gamma coincidence yields and from the measured lifetimes. A consistent set of results was obtained. The collective E2 transition rates determined from the analysis were found to be in remarkably good agreement with the predictions of the interacting boson model with configuration mixing.     

大功率辐照加速器的研制

介绍了10MeV/20kW大功率辐照加速器的设计. 该加速器采用返波型行波加速结构加速管, 综合了常规行波加速结构微波反射小、频率稳定性好和驻波加速结构分流阻抗高的优点. 加速器工作于S波段, 中心频率为~2856MHz. 利用自编的模拟程序AccDesign进行物理设计, 设计输出电子束能量为10MeV, 脉冲流强300mA, 加速管总长1.5m, 模拟计算结果显示微波至电子束的转换效率为66%. 同时利用计算机仿真程序对加速腔的温度和应力分布进行了计算, 得到了微波功率损耗对加速腔频率的影响.     

CSNS-II超导椭球腔失谐研究

中国散裂中子源二期束流功率升级到500 kW，直线加速器H-的能量增益由现在的80 MeV提高到300 MeV以上，其中150 ~ 300 MeV能量段采用648 MHz β_g=0.60的5-cell超导椭球腔结构。超导椭球腔具有加速梯度高、结构简单、后处理容易等优点，缺点是结构强度弱、易失谐。本文主要研究该椭球腔的失谐特性。利用COMSOL Multiphysics软件进行了计算分析，在两端固定边界条件下，裸腔的氦压敏感性系数K_P=–45.705 Hz/mbar(1 mbar=100 Pa)，洛伦兹力失谐因子K_L=1.574 Hz/(MV/m)2。增加加强环并优化其位置来改善氦压敏感性系数和洛伦兹力失谐因子，通过计算分析最终确定选择双加强环方案来减小椭球腔的失谐。两个加强环位置分别取在75和120 mm的位置，腔体失谐的改善最大，K_P=6 Hz/mbar，K_L=0.43 Hz/(MV/m)2。为了更准确地计算椭球腔的氦压敏感性系数和洛伦兹力失谐因子，本文引入调谐刚度边界条件进行失谐分析，在椭球腔调谐器端设置30 kN/mm边界条件，另一端固定，计算得到氦压敏感性系数为4.8 Hz/mbar，洛伦兹力失谐因子1.99 Hz/(MV/m)2，满足工程要求。另外，用CST软件对椭球腔的动态洛伦兹力失谐进行了初步分析，用软件Workbench计算了椭球腔的振动本征频率，结果显示，振动本征频率离射频脉冲重复频率及环境振动频率较远，不易发生共振失谐。     

热核衰变中轻粒子的发射时间

报道了25MeV/u ⁴⁰Ar+¹⁹⁷Au反应中裂片符合下的粒子—粒子关联函数及其发射时间.实验测得粒子的平均发射时间为200—300fm/c,表明轻粒子的裂前发射占主导.在平面发射和出平面发射的粒子发射时间相差很少,发射时间是随着粒子能量的改变而发生显著变化,从中速粒子的约300fm/c下降至类弹粒子的约30—100fm/c.     

Decay properties of low-lying levels in100Rh

Zeitschrift für Physik A Hadrons and nuclei - Low-lying levels of100Rh have been investigated with the reaction100Ru(p, nγ)100Rh in the proton energy range 4.4 MeV≦E p≦6 MeV....     

Preliminary design studies of a 100 MeV H−/H+ LINAC as injector for SNS synchrotron/ADS LINAC

It is proposed to construct a spallation neutron source (SNS) at Centre for Advanced Technology (CAT) based on a 1 GeV proton synchrotron with 100 MeV H⁻ LINAC as injector. Additionally, the LINAC can form the first 100 MeV part of a 1 GeV proton LINAC to be built in future for accelerator driven system (ADS) applications. We are exploring a configuration of the 100 MeV LINAC which will consist of an H⁻ ion source, a 4–6 MeV RFQ followed either by a 20 MeV drift tube LINAC (DTL) and 100 MeV separated function drift tube LINAC (SDTL) or a coupled cavity drift tube LINAC (CCDTL) structure. In this paper, we present the results of our preliminary physics design studies of the RFQ-SDTL, RFQ-CCDTL and RFQ-DTL-SDTL configurations. The design of the 4.5 MeV RFQ is discussed along with the matching sections between the RFQ-SDTL/DTL and RFQ-CCDTL. The choice of the accelerator configuration and that of various parameters of the individual accelerator structures under consideration are discussed. The design objectives are to arrive at a configuration which eases heat removal for CW operation and which is less prone to halo formation in order to reduce the beam loss at higher energies.     

100keV质子与低高能质子在绝缘微孔中输运特性的对比分析

为研究中能区带电粒子在绝缘微孔中传输的物理图像,利用MATLAB程序和蒙特卡罗方法建立理论模型,得到入射能量为10 keV,100 keV和1 MeV的质子,以-1?倾斜角入射到微孔后,出射粒子角分布、沉积电荷斑分布,以及粒子在微孔内的运动轨迹等传输特性.研究结果表明,在10 keV的低能区,微孔内壁沉积电荷的导向效应是主要的传输机制.在1 MeV的高能区,进入表面以下多次随机非弹性碰撞是主要的输运机制.在100 keV的中能区,无电荷斑时,主要是以进入表面以下的随机二体碰撞为传输机制;在电荷斑累积过程中,增强的库仑排斥力逐渐抑制入射质子在微孔内壁表面发生电子俘获;当达到充放电平衡后,主要传输机制为电荷斑辅助的近表面镜面散射行为.这一特性加深了对中能区质子在微孔中输运行为的认识,有助于对百keV质子微束的控制和应用.     

花瓣形加速器加速腔结构的优化设计

 介绍了一种新型辐照加速器——花瓣形加速器NB100（10 MeV/100 kW）。用电磁场3维仿真软件模拟计算了此种加速器加速腔的高频特性参数,研究了腔体特性参数与几何尺寸的关系,在考虑电子束渡越时间情况下,优化出了一组频率为100 MHz时的加速腔结构其尺寸为：腔体高度1 547 mm,外筒内半径980 mm,内筒外半径240 mm,内筒倒圆角半径210 mm,外筒倒圆角半径110 mm。计算结果表明：该种新加速腔具有较高的有效分路阻抗和品质因数。     

Effect of plasma scale length on multi-MeV proton production by intense laser pulses

The influence of the plasma density scale length on the production of MeV protons from thin foil targets irradiated at I lambda(2) = 5 x 10(19) W cm(-2) has been studied. With an unperturbed foil, protons with energy >20 MeV were formed in an exponential energy spectrum with a temperature of 2.5+/-0.3 MeV. When a plasma with a scale length of 100 microm was preformed on the back of the foil, the maximum proton energy was reduced to <5 MeV and the beam was essentially destroyed. The experimental results are consistent with an electrostatic accelerating mechanism that requires an ultrashort scale length at the back of the target.     

Influence of radial magnetic field on emittance in the median plane at CYCIAE-100

A 75—100 MeV H- compact cyclotron CYCIAE-100 is being constructed at China Institute of Atomic Energy (CIAE). About 200 μA proton beam will be provided by CYCIAE-100. The imperfection of magnetic fields will remarkably affect the acceleration orbit and beam envelope in CYCIAE-100. The effects to the accelerating beam by the imperfection fields, especially the field components Br on the mid-plane will be analyzed in detail with tracking code COMA. Poles misalignment that causes magnetic imperfection will be described in the paper. According to the simulation results, the tolerance of the poles machining and assembly will be illustrated in this paper.