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The Beijing Electron Positron Collider II (BEPCII) has achieved a series of achievements in high energy physics study. Along with the deepening of the research, more important physics is expected in higher energy region (>2.1 GeV). As the upper limit of BEPCII design energy is 2.1 GeV, an urgent upgrade is required for BEPCII. To achieve a higher luminosity at higher energy, the number of RF cavities is expected to be doubled. The baseline design which kept the survey of the North Collision Region (NCR) unchanged for the upgrade of BEPCII has been studied in previous work. In this paper, we show an alternative design that modifies the survey of NCR, but enables the online maintenance of both RF cavities in each ring of BEPCII. The dynamic aperture tracking result shows that the lattice could meet the injection requirement of BEPCII beam with reasonable margin., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Beijing Electron Positron Collider II (BEPCII) has achieved a series of achievements in high-energy physics study. Along with the deepening of the research, more important physics is expected in higher energy regions (>2.1 GeV). As the upper limit of BEPCII design energy is 2.1GeV, an urgent upgrade is required for BEPCII. To achieve a higher luminosity at higher energy, the number of RF cavities is expected to be doubled. In this paper, the lattice design for the upgrade of BEPCII is studied. The dynamic aperture tracking result shows that the lattice could meet the injection requirement of the BEPCII beam with a reasonable margin., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Wire scanners are widely used for measuring beam emittance in both electron and hadron accelerators. Gaussian fitting is the most commonly used method in processing the wire scanner data. But in hadron machines, beams are normally not gaussian distribution due to the action of nonlinear forces such as space charge effect. Under these circumstances, there would be big deviations if the wire scanner data was still fitted with gaussian distributions. This paper introduces generalized Gaussian distribution in the processing the wire scanner data measured in the ADS injector-I. The results using different fitting method will be compared., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Machine Detector Interface (MDI) is the key research area in electron-positron colliders, especially in CEPC, it is one of the criteria to measure the accelerator and detector design performance. In this paper, we will introduce the CEPC superconducting magnets design, solenoid compensation, synchrotron radiation and mask design, detector background, collimator, mechanics assembly etc on, which are the most critical physics problem., Proceedings of the 62th ICFA ABDW on High Luminosity Circular e$^+$e$^-$ Colliders, eeFACT2018, Hong Kong, China

Circular electron-positron collider (CEPC) is a dedi-cated project proposed by China to research the Higgs boson. The collider ring provides e⁺ e⁻ collision at two interaction points (IP). The luminosity for the Higgs mode at the beam energy of 120GeV is 3*10³⁴ cm⁻²s⁻¹ at each IP while the synchrotron radiation (SR) power per beam is 30MW. Furthermore, CEPC is compatible with W and Z experiments, for which the beam ener-gies are 80 GeV and 45.5 GeV respectively. The lumi-nosity at the Z mode is higher than 1.7*10³⁵ cm⁻²s⁻¹ per IP. Top-up operation is available during the data taking of high energy physics. The status of CEPC will be introduced in detail in this paper., Proceedings of the 62th ICFA ABDW on High Luminosity Circular e$^+$e$^-$ Colliders, eeFACT2018, Hong Kong, China

Circular electron-positron collider (CEPC) is a dedi-cated project proposed by China to research the Higgs boson. The collider ring provides e⁺ e⁻ collision at two interaction points (IP). The luminosity for the Higgs mode at the beam energy of 120GeV is 3*10³⁴ cm⁻²s⁻¹ at each IP while the synchrotron radiation (SR) power per beam is 30MW. Furthermore, CEPC is compatible with W and Z experiments, for which the beam energies are 80 GeV and 45.5 GeV respectively. The luminosity at the Z mode is higher than 1.7*10³⁵ cm⁻²s⁻¹ per IP. Top-up operation is available during the data taking of high energy physics. Super Proton-Proton Collider (SPPC) is envisioned to be an extremely powerful machine, with centre mass energy of 75 TeV, a nominal luminosity of 1.0*10³⁵ cm⁻²s⁻¹ per IP, and an integrated luminosity of 30 ab⁻¹ assuming 2 interaction points and ten years of running. The status of CEPC and SPPC will be introduced in detail in this paper., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The 10 MeV accelerator-driven subcritical system (ADS) Injector I test stand at Institute of High Energy Physics (IHEP) is a testing facility dedicated to demonstrate one of the two injector design schemes [Injector Scheme-I, which works at 325 MHz], for the ADS project in China. The ion source was installed since April of 2014, periods of commissioning are regularly scheduled between installation phases of the rest of the injector. Early this year, continuous wave (CW) proton beam has been successfully obtained with energy of 10MeV and average beam current around 2 mA, the single spoke cavities with smallest developed beta (βg=0.12) were applied and successfully commissioned. Single spoke cavities with higher beta (βg=0.21) were also adopted for the last cryomodule of 25MeV proton linac, and 170uA CW proton beam were shooting through recently. This contribution reports the details of the development of the C-ADS SRF accelerator at IHEP and the challenges of the CW machine commissioning, Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

The 100km double ring configuration with shared su-perconducting RF system has been defined as baseline by the circular electron positron collider (CEPC) steering committee. Based on this new scheme, we will get higher luminosity for Higgs (+170%) keeping the beam power in preliminary conceptual design report (Pre-CDR) or to reduce the beam power (19 MW) while keeping same luminosity. CEPC will be compatible with W and Z ex-periment. The luminosity for Z is designed at the level of 1035 cm⁻²s^{−1}. The requirement for the energy acceptance of Higgs has been reduced to 1.5% by enlarging the ring to 100 km. The optics of arc and final focus system (FFS) with crab sextupoles has been designed, and also some primary dynamic aperture (DA) results were introduced., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

CADS Injector-I accelerator is a 10-mA 10-MeV CW proton linac, which uses a 3.2-MeV normal conducting 4-Vane RFQ and superconducting single-spoke cavities for accelerating. Eight wire scanners are designed and used to measure the beam profile of CADS Injector-I. In this paper principal of operation, instrumentation and programming of these wire scanners are discussed. Some results of beam profile and emittance measurement with these wire scanners are also presented., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

At the energies envisioned for the FCC-ee the synchrotron radiation produces not only closed orbit effects but also some dynamics effects including strong "beta-synchrotron" coupling due to radiation in the final focus quadrupoles. Past experience with LEP and other machines as well as the implications for the new wave of circular electron collider proposals will be discussed., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

CEPC is a circular electron and positron machine designed to study the property of the Higgs boson. The beam energy for CEPC is thus chosen to be 120GeV. At such a high energy, synchrotron radiation has pronounced effect on the beam behavior. In this paper, we will show the synchrotron radiation effect in the CEPC single ring design, namely, the closed orbit, linear optics and dynamic aperture. Analytical analysis will be given trying to explain the phenomenon., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

IHEP has proposed a circular electron and positron collider (CEPC) to study the properties of the Higgs boson. In the baseline design, the circumference of CEPC will be taken as 50-70km. The single ring scheme and the partial double ring scheme are now both under study. In the single ring scheme, the electron and positron beam will share the beam pipes, thus a special orbit is needed to avoid the beam colliding at positions except the Interaction Points (IPs). While in the partial double ring scheme, the two beams will be separated into two beam pipes in the parasitic collision positions. This paper will show the latest design of the CEPC lattice, including both the pretzel and partial double ring scheme. Some critical issues that we encountered when designing the lattices will be discussed., Proceedings of the 58th ICFA Advanced Beam Dynamics Workshop on High Luminosity Circular e^+e^- Colliders, eeFACT2016, Daresbury, UK

High power is the development tendency of proton accelerator, so obtaining uniform beam distribution on target becomes more and more important and critical. The method of using step-like field magnets to obtain a uniform beam distribution on target was presented. In the beamdump line of CADS injector-I test facility four step-like field magnets have been installed to uniform beam distribution to reduce the maximum current density on the beamdump. The magnetic field of step-like field magnets have been measured and discussed in this paper. The simulation results and measurement results of beam uniformization are presented., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

CEPC is a future Circular Electron and Positron Collider proposed by China to mainly study the Higgs boson. Its baseline scheme is double ring scheme and alternative scheme is partial double ring scheme. This paper will present the optics design for the main ring of double ring scheme. CEPC will also work as W and Z factories. Compatible optics design for W and Z mode will be presented as well., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Beam-Gas scattering (BG) and Beam-Thermal photon scattering (BTH), although not so serious as Radiative Bhabha scattering (RBB) and Beamstrahlung (BS), are also important components of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam-gas and beam-thermal photon scattering in simulation and designed collimators to suppress the radiation level on the machine and the detector., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

As a test facility, the design goal of C-ADS Injector I is a 10mA, 10MeV CW proton linac, which uses a 3.2MeV normal conducting RFQ and superconducting single-spoke cavities for accelerating. The RF frequency of C-ADS Injector I accelerator is 325 MHz. In accordance to the progress of construction and considering the technical difficulties, the beam commissioning of C-ADS Injector I is carried out in 3 phases: Phase 1, with ECRIS + LEBT + RFQ + MEBT + TCM (two superconducting cavities), to reach 3.6 MeV; Phase 2, with ECRIS + LEBT + RFQ + MEBT + CM1 (seven superconducting cavities), to reach 5 MeV; Phase 3, with ECRIS + LEBT + RFQ + MEBT + CM¹⁺ CM2 (same as CM1), to finally achieve the design goal of C-ADS Injector I. This paper summarizes the beam commissioning in 3 phases and focusing on the third phase., Proceedings of the 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2016, Malmö, Sweden

The transverse emittance at C-ADS injector-I has been measured by the wire scanners at the Medium Energy Beam Transport-I (MEBT1). We have studied the effect of different fitting methods for obtaining the beam sizes on the emittance result, the result will be presented in this paper. The validation study of the quad-scan method with the presence of space charge effect at 10 mA will also be shown, and finally the quad-scan results will be compared with the multi-wire results., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

Superconducting linear accelerator is the tendency in linac design with the development of superconducting RF technology. Superconducting cavities used as accelerating section in low energy Hadron linac are more and more common. The 5MeV test stand of CADS accelerator Injector I is composed of an ion source, a LEBT, a 325MHz RFQ, a MEBT, a cryogenic module (CM1) of seven SC spoke cavities (β=0.12) , seven SC solenoids, seven cold BPMs and a beam dump. The phase and amplitude setting of superconducting cavity are very important at the operation of accelerator, so beam based measurement of cavity phase and amplitude is necessary. Beam based phase scan is the most simple and effective method. Because the significant velocity changes in superconducting cavity at low energy section, the effective voltage is changing with cavity phase, meanwhile the synchronous phase is non-linear with LLRF phase. Above two problem make the cavity phase determination difficult. New date fitting method is proposed to solve these problem in this paper. Some measurements of spoke cavities in the CADS CM1 are also presented., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

A preliminary design of the CEPC ring with pretzel orbit will be presented. The ring and pretzel orbit will be designed for 50 bunches, as required in the CEPC Pre-CDR. The linear optics, as well as the non-linear chromaticity compensation with the presence of pretzel orbit will be described. Different phase advance difference between the long and short straight sections, have been tried to optimize the dynamic aperture, the results will be shown in this paper., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

In this paper, we introduced the layout and lattice design of Circular-Electron-Positron-Collider (CEPC) partial double ring (PDR) scheme. The baseline design of CEPC is a single beam-pipe electron positron collider, which has to adopt pretzel orbit scheme. And it is not suitable to serve as a high luminosity Z factory. If we choose partial double ring scheme, we can get a higher luminosity with lower power and be suitable to serve as a high luminosity Z factory. In this paper, we discussed the details of CEPC partial double ring lattice design and showed the dynamic aperture study and optimization., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The C-ADS accelerator is a CW (Continuous-Wave) proton linac with 1.5 GeV in beam energy, 10 mA in beam current, and 15 MW in beam power. CADS Injector-I accelerator is a 10-mA 10-MeV CW proton linac, which uses a 3.2-MeV normal conducting 4-Vane RFQ and superconducting single-spoke cavities for accelerating. The 5MeV test stand of CADS accelerator Injector I is composed of an ion source, a LEBT, a 325MHz RFQ, a MEBT, a cryogenic module (CM1) of seven SC spoke cavities (β=0.12) , seven SC solenoids, seven cold BPMs and a beam dump. Emittance measurement is very important for the understanding of beam behavior and matching to the next accelerating section. Detailed emittance measurement with double-slit method after CM1 are presented in this paper., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The 10 MeV accelerator-driven subcritical system (ADS) Injector I test stand at Institute of High Energy Physics (IHEP) is a testing facility dedicated to demonstrate one of the two injector design schemes [Injector Scheme-I, which works at 325 MHz], for the ADS project in China. The ion source was installed since April of 2014, periods of commissioning are regularly scheduled between installation phases of the rest of the injector. 6.05 MeV proton energy has been achieved with average beam current of 10 mA by 7 SC spoke cavities at present. This contribution reports the details of the commissioning results together with the challenges of the CW machine commissioning., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

CEPC is a Circular Electron and Positron Collider proposed by China to mainly study the Higgs boson. In order to achieve factory luminosity, a strong focusing system and low-emittance are required. A momentum acceptance as large as 2\% is also required to get a reasonable beam lifetime. This is one of the key issues of the CEPC accelerator physics. In this paper, the optics design of the interaction region and the optimization of dynamic aperture for the whole ring (single ring scheme) will be presented., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Radiative Bhabha scattering and Beamstrahlung effects are dominant mechanism of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam loss background in simulation and designed a series of collimators to suppress the radiation level on the machine and the detector., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The institute of High Energy Physics has proposed an electron positron collider ring with a circumference of 50-100km to study the Higgs boson. Since the proposal was made, the lattice design for CEPC has been carried out and a preliminary conceptual design report has been written at the end of 2014. In this paper, we will describe the philosophy and results of our lattice design. The procedure of dynamic aperture optimization will be shown. A specific issue for CEPC, the pretzel orbit, which has been found distorting the linear lattice for a considerable amount, will be examined. The ways that we are trying to correct the pretzel orbit effect and the result will be shown. We will also discuss the saw tooth effect on the linear lattice and dynamic aperture of the ring., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

CEPC (Circular Electron and Positron Collider) is a circular Higgs Factory with optimized energy 240 GeV. In order to achieve luminosity as high as 2×10³⁴/cm²/s, CEPC calls for a small vertical beta function at IP (betay∗=1.2 mm) which was provided by the final focus of the interaction region. In this paper, a preliminary design of the CEPC interaction region was presented. The optimization of dynamic aperture with interaction region insertion and the machine detector interface was discussed as well., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The 1.6 GeV proton synchrotron proposed in the CSNS Project is a 25 Hz rapid-cycling synchrotron (RCS) with injection energy of 80 MeV. Beam power is aimed to 100 kW at 1.6 GeV. The power supply system consists of seven subsystems. Those power supplies have three operation modes: DC mode, AC plus DC mode and programmable pulse mode. This paper will introduce the Power supply system status in recent years., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

With the discovery of the higgs boson at around 125GeV, a circular higgs factory design with high luminosity (L ~ 10³⁴ cm⁻²s⁻¹) is becoming more popular in the accelerator world. The CEPC project in China is one of them. To reduce the cost, pretzel scheme was considered in CEPC orbit design. The presence of every kind of errors and misalignments will destroy the pretzel orbit. In this paper, we correct the distorted pretzel orbit in the CEPC main ring using the dipole correctors and beam position monitors. The pretzel orbit was recovered and the maximum corrector strengths are got., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The CEPC (China Electron-Positron Collider) project is in the pre-research stage. When the beam energy of booster is 120 GeV, the magnetic field of deflection magnet is 640 G. In order to save funds for scientific research, we are ready to select the injection energy for 6 GeV, this corresponds to a magnetic field about 32 G. In such a low magnetic field, the effects of earth's magnetic field and ambient temperature variations cannot be ignored. In this paper, first written the collection procedures for magnetic field value and ambient temperature values by Labview software, then used a one-dimensional probe to measure the background magnetic field for three directions (Bx, By, Bz) and the value of the ambient temperature values, the time of data collection for each direction are more than 24 hours (every minute collecting a set of values). Finally, plus the different currents (3A, 6A.. 15A) to the dipole magnet, the time of measured and the data collected by over 24 hours. Based on the results of the analysis of large amounts of data, summarized and analyzed the effect of Earth's magnetic field and ambient temperature for dipole magnet in a low magnetic field., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

With the discovery of the higgs boson at around 125GeV, a circular higgs factory design with high luminosity (L ~ 10³⁴ cm⁻²s⁻¹) is becoming more popular in the accelerator world. To achieve such high luminosity, a final focus system in non-local chromaticity correction scheme with very low β functions at the interaction point is designed. The narrow momentum bandwidth is a crucial problem of this kind of design. It is shown that by introducing additional sextupoles the momentum acceptance of the CEPC final focus system can be increased by about a factor of four., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The C-ADS accelerator is a CW (Continuous-Wave) proton linac with 1.5 GeV in beam energy, 10 mA in beam current, and 15 MW in beam power. C-ADS Injector-I accelerator is a 10-mA 10-MeV CW proton linac, which uses a 3.2-MeV normal conducting 4-Vane RFQ and superconducting single-spoke cavities for accelerating. The frequency of RFQ accelerator is 325 MHz. The test stand composed of an ECR ion source, LEBT, RFQ, MEBT and beam dump have been installed and the first stage of beam commissioning have been finished at IHEP in 2014 mid-year. At 90% duty factor, we got 11 mA proton beam at RFQ exit with 90% beam transmission efficiency, while 95% beam transmission efficiency at 70% duty factor. The energy after RFQ was measured by TOF method with FCTs. The transverse emittance measured by double-slits emittance meter was 0.135 π mm-mrad, which of detailed data analysis will be presented in this paper., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The C-ADS project is building a test facility at the Institute of High Energy Physics. The design goal of the test facility is 10MeV beam energy with a continuous beam current of 10mA. To sustain the 100kW CW beam power at the beam dump, a beam distribution transform system is designed. The Step Field Magnets (SFMs) are used to transform the beam distribution from Gaussian to uniform. In this test stand, two sets of SFMs will be employed to manipulate the beam distribution. At the first commissioning stage, the bump dump line will be connected to the Medium Energy Beam Transport-1 (MEBT1) to test the beam manipulation scheme. The design and error analysis of this 3MeV beam dump line will be discussed in this paper., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The crossed-planar undulator is a promising scheme for full polarization control in an x-ray FEL*. For SASE FELs, it has been shown a maximum degree of circular polarization of about 80% is achievable**. In this paper, we study the effectiveness of a cross undulator for a seeded x-ray FEL. The degree of circular polarization for both the fundamental and the harmonic radiation are considered., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan