摘要：ANL （Argonne National laboratory） and the National Science Center ＂Kharkov Institute of physics technology＂ （NSC KIPT, Kharkov, Ukraine） jointly propose to design and build a 100 MeV/100 kW linear accelerator which will be used to drive the neutron source subcritical assembly. The linac has ahnost finished assembly in KIPT by a team from the Institute of High Energy physics （IHEP, Beijing, China）. The design and measurement result of the accelerating system of the linac will be described in this paper.

摘要：A new generation of storage ring-based light sources, called diffraction-limited storage rings（DLSR）, with emittance approaching the diffraction limit for multi-ke V photons by using multi-bend achromat lattice, has attracted worldwide and extensive studies of several laboratories, and been seriously considered as a means of upgrading existing facilities in the imminent future. Among various DLSR proposals, the PEPX design demonstrated that it is feasible to achieve sufficient ring acceptance for off-axis injection in a DLSR, by designing the lattice based on the ‘thirdorder achromat’ concept and with a special high-beta injection section. For the High Energy Photon Source（HEPS）planned to be built in Beijing, a PEPX-type lattice has been designed and continuously improved. In this paper, we report the evolution of the PEPX-type design for HEPS, and discuss the main issues relevant to the linear optics design and nonlinear optimization.

摘要：In this paper we will show a cavity and higher order mode （HOM） coupler designing scheme for the Circular Electron-positron Collider （CEPC） main ring. The cavity radio frequency （RF） design parameters are shown in this paper. The HOM power is calculated based on the beam parameters in the Preliminary Conceptual Design Report （Pre-CDR）. The damping results of the higher order modes （HOMs） and same order modes （SOMs） show that they reach the damping requirements for beam stability.

摘要：A new generation of storage ring-based light sources,called diffraction-limited storage rings（DLSRs）,with emittance approaching the diffraction limit for multi-keV photons by means of multi-bend achromat lattices,has attracted extensive studies *** various DLSR proposals,the hybrid multi-bend achromat concept developed at the European Synchrotron Radiation Facility（ESRF） predicts an effective way of minimizing the emittance while keeping the required chromatic sextupole strengths to an achievable *** the High Energy Photon Source planned to be built in Beijing,an ESRF-type lattice design consisting of 48 hybrid seven-bend achromats is proposed to reach emittance as low as 60 pm-rad with a circumference of about 1296 *** dynamic aperture,allowing vertical on-axis injection,and moderate momentum acceptance are achieved simultaneously for a promising ring performance.

摘要：A baseline design for the High Energy Photon Source has been proposed, with a natural emittance of 60 *** within a circumference of about 1.3 kilometers. Nevertheless, the nonlinear performance of the design needs further improvements to increase both the dynamic aperture and the momentum acceptance. In this study, genetic optimization of the linear optics is performed, so as to find all the possible solutions with weaker sextupoles and hence weaker nonlinearities, while keeping the emittance at the same level as the baseline design. The solutions obtained enable us to explore the dependence of nonlinear dynamics on the working point. The result indicates that with the same layout, it is feasible to obtain much better nonlinear performance with a delicate tuning of the magnetic field strengths and a wise choice of the working point.

摘要：In the lattice design of a diffraction-limited storage ring（DLSR） consisting of compact multi-bend achromats（MBAs）, it is challenging to simultaneously achieve an ultralow emittance and a satisfactory nonlinear performance, due to extremely large nonlinearities and limited tuning ranges of the element parameters. Nevertheless, in this paper we show that the potential of a DLSR design can be explored with a successive and iterative implementation of the multi-objective particle swarm optimization（MOPSO） and multi-objective genetic algorithm（MOGA）. For the High Energy Photon Source, a planned kilometer-scale DLSR, optimizations indicate that it is feasible to attain a natural emittance of about 50 pm·rad, and simultaneously realize a sufficient ring acceptance for on-axis longitudinal injection, by using a hybrid MBA lattice. In particular, this study demonstrates that a rational combination of the MOPSO and MOGA is more effective than either of them alone, in approaching the true global optima of an explorative multi-objective problem with many optimizing variables and local optima.

摘要：In order to meet the requirements of the Circular Electron Positron Collider(CEPC),a 650-MHz 2-cell superconducting cavity was proposed and *** this study,we show the progress in the cavity design for the *** radio frequency and mechanical designs are ready for the first design version,called CEPC-V1.A cryomodule,which consists of two 650-MHz 2-cell cavities,was scheduled the last ***,prototypes of the 2-cell cavity based on this design were fabricated and tested the following *** vertical test results show that multipacting(MP)exists from 10 to 19 MV/*** will increase the operational risk of the CEPC,while the continuous-wave operation for the 650-MHz cavity is 19.7 MV/*** trapped modes were also found,which exist because of the identical half-cell ***,a few improvements regarding MP and more efficient extraction of higher-order mode power are discussed.A new type of cavity design,called CEPC-V2,is also discussed in this paper.

摘要：The Accelerator Driven Sub-critical(ADS)system is a strategic plan to solve the nuclear waste problem for nuclear power plants in ***-energy particle accelerators and colliders contain long strings of superconducting devices,superconducting radio frequency cavities,and magnets,which may require cooling by 2 K superfluid helium(HeliumⅡ).2 K superfluid helium cryogenic system has become a research hot spot in the field of superconducting *** this study,the ADS Injector-I 2 K cryogenic system is examined in *** cryogenic system scheme design,key equipment,and technology design,such as the 2 K Joule–Thomson(J–T)heat exchanger and cryomodules CM1+CM2 design,are examined,in addition to the commissioning and operation of the cryogenic *** ADS Injector-I 2 K cryogenic system is the first 100 W superfluid helium system designed and built independently in *** ADS proton beam reached 10 Me V at 10 m A in July 2016 and 10 Me V at 2 m A in continuous mode in January 2017 and has been operated reliably for over 15,000 h,proving that the design of ADS Injector-I 2 K cryogenic system,the key equipment,and technology research are reasonable,reliable,and meet the *** research into key technologies provides valuable engineering experience that can be helpful for future projects such as CI-ADS(China Initiative Accelerator-Driven System),SHINE(Shanghai High Repetition Rate XFEL and Extreme Light Facility),PAPS(Platform of Advanced Photon Source technology),and CEPC(Circular Electron-Positron Collider),thereby developing national expertise in the field of superfluid helium cryogenic systems.

摘要：We present the first phase R&D for the 800 kW cw, 650MHz klystron for the future circular electron-positron collider (CEPC) project in China. The CEPC requires 192 klystrons and it is desired to be designed in the Institute of High Energy physics, CAS, and manufactured domestically. Therefore, we present the manufacturing schedule of this project; the three-stage development from the beam test tube to the klystron having a high efficiency structure. Design of the beam test tube that comprises electron gun and collector is presented. First, gun simulation having a modulating anode is performed using DGUN software. The uniform beam trajectories with a beam perveance of 0.64 mu A/V-3/2 are simulated. We employ a Ba-dispenser cathode of radius 35mm with phi 10 hole at the center and obtain a current density on cathode less than 0.45 A/cm(2). The beam trajectories are also simulated over beam test tube of length about 2m with a magnetic field of 213 Gauss. Thermal analysis of the collector is performed using the ANSIS-CFX code and hence the cooling structure is determined. Mechanical design is almost carried out and it is in manufacturing stage.

摘要：This paper presents the first phase of design, analysis, and simulation for the klystron coaxial radio frequency（RF）output window. This study is motivated by 800 kW continuous wave（CW）, 650 MHz klystrons for the future plan of circular electron–positron collider（CEPC） project. The RF window which is used in the klystron output section has a function to separate the klystron from the inner vacuum side to the outside, and high RF power propagates through the window with small power dissipation. Therefore, the window is a key component for the high power klystron. However, it is vulnerable to the high thermal stress and multipacting, so this paper presents the window design and analysis for these problems. The microwave design has been performed by using the computer simulation technology（CST） microwave studio and the return loss of the window has been established to be less than-90 d B. The multipacting simulation of the window has been carried out using MultiPac and CST particles studio. Through the multipacting analysis, it is shown that with thin coating of TiN, the multipacting effect has been suppressed effectively on the ceramic surface. The thermal analysis is carried out using ANSYS code and the temperature of alumina ceramic is lower than 310 K with water *** design result successfully meets the requirement of the CEPC 650 MHz klystron. The manufacturing and high power test plan are also described in this paper.