SAP2023 - List of Keywords (simulation)

Paper	Title	Other Keywords	Page
MOCXA02	Beam-Beam Interaction with Longitudinal Impedance and Its Application in TMCI Study	impedance, coupling, synchrotron, electron	1
	C.T. Lin IASF, Shenzhen, Guangdong, People’s Republic of China K. Ohmi KEK, Ibaraki, Japan Y. Zhang IHEP, Beijing, People’s Republic of China
	Simulations have showed a novel coherent head-tail instability induced by beam-beam interaction with a large Piwinski angle. The localized cross-wake force has been introduced to explain the instability. The longitudinal impedance would cause coherent and incoherent synchrotron tune shift and distort the particle¿s trajectories in longitudinal phase space. Further beam-beam simulation revealed that the longitudinal impedance has strong impacts on the beam stability, squeezing the horizontal stable tune area seriously. The instability has become an important issue during the designs of CEPC and FCC-ee. In this paper, we develop a transverse mode coupling analysis method that could be used to study beam-beam instability with and without longitudinal impedance. This method can also be applied in synchrotron light sources to study transverse mode coupling instability (TMCI) with longitudinal impedance and harmonic cavity. Some preliminary results at Shenzhen Innovation Light Source (SILF) are also shown.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOCXA02
About •	Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 23 September 2024
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MOPB001	Terahertz-Driven MeV Electron Bunch Compression and Streaking	electron, FEM, timing, laser	14
	Y. Xu, K. Fan, Z. Liu, Y. Song, C.-Y. Tsai, J. Wang HUST, Wuhan, People’s Republic of China
	Electron bunches with ultra-short bunch length and ultra-high timing stability are crucial for various applications. To achieve these desired characteristics, there is a growing interest in employing Terahertz-driven techniques to manipulate and diagnose electron bunches. This paper presents a method capable of compressing and measuring electron bunch lengths. Theoretical and simulation results demonstrate that the bunch length of 54 is reduced to 4 fs by utilizing THz-driven resonant cavity compression, achieving a compression ratio of 13. Furthermore, we also verify the bunch compression using a terahertz-driven streak camera.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB001
About •	Received ※ 28 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 26 February 2024
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MOPB008	Approximation of Space Charge Effect in the Presence of Longitudinal Magnetic Fields	space-charge, controls, electron, emittance	27
	H.Y. Li, H.B. Chen, Q. Gao, W.H. Gu, J.R. Shi, H. Zha TUB, Beijing, People’s Republic of China
	The space charge effect plays a significant role in the evolution of phase space during beam transport. Applying an external longitudinal magnetic field has been shown to effectively reduce beam expansion through the mechanism of beam rotation. In this article, we present a fast approximation algorithm for estimating the impact of an external magnetic field on beam expansion. The algorithm enables efficient computations and provides insights into controlling the phase space dynamics of the beam in the presence of longitudinal magnetic fields.
	Poster MOPB008 [0.447 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB008
About •	Received ※ 30 June 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 30 April 2024
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MOPB016	Matching Section Optics Design for the MeV Ultrafast Electron Beam Experimental Facility	electron, sextupole, quadrupole, dipole	37
	H. Qi, K. Fan, Z. Liu, C.-Y. Tsai, J. Wang HUST, Wuhan, People’s Republic of China
	This paper introduces the design and optimization of the matching section beamline for the ultrafast electron research platform at Huazhong University of Science and Technology (HUST). The matching section serves as a connection between the main beamline and the beam physics research beamline, aiming to achieve efficient and precise control over the electron beam trajectory and parameters. To evaluate its performance, particle tracking simulations using GPT software were conducted. When the beam is set at 3 MeV and 1 pC charge, the matching section is capable of compressing the bunch length to approximately 50 fs. This level of compression is crucial for ultrafast electron research applications, as it enables the study of phenomena that occur on extremely short time scales, demonstrating its effectiveness in achieving precise beam control and compression.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB016
About •	Received ※ 29 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 20 January 2024
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MOPB026	Physical Design for EEHG Beamlines at S3FEL	FEL, electron, undulator, radiation	55
	X.F. Wang Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China C. Feng, Z. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China X.M. Li, J.T. Sun, Y. Yu DICP, Dalian, Liaoning, People’s Republic of China Y.F. Liang, X.M. Yang, H. Yi, L. Zeng, W.Q. Zhang IASF, Shenzhen, Guangdong, People’s Republic of China
	Funding: Work supported by the National Key R&D Program of China (Grant No.2018YFE0203000) and the National Natural Science Foundation of China (Grant No.22288201). The proposed Shenzhen Superconducting Soft X-Ray Free-electron Laser (S3FEL) aims at generating FEL pulses from 1 nm to 30 nm. At phase-I, two undulator beamlines work at ehco-enable harmonic generation (EEHG) principle. The two undulators will cover the spectral ranges 2.3-15 nm (~83-539 eV) and 5-30 nm (~41-248 eV), respectively, when receiving electrons from 2.5 GeV superconducting linac. However, the generated FEL radiation is sensitive to various electron beam properties, e.g., its energy profile influenced by collective effects such as Coherent Synchroton Radiation (CSR), especially at high harmonics. To generate intense full coherent FEL radiation at ultra-short wavelength, a novel technique of EEHG cascaded harmonic lasing method is also considered. Physical design and FEL performance are described in this paper.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB026
About •	Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 18 July 2023 — Issued ※ 04 October 2024
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MOPB027	A Scheme of Fully Coherent X-Ray Free Electron Laser for the Shine Based on Fresh-Slices	electron, FEL, radiation, undulator	59
	YX. Liu SINAP, Shanghai, People’s Republic of China T. Liu SARI-CAS, Pudong, Shanghai, People’s Republic of China
	In this paper, the fresh-slice self-seeding free electron laser scheme is studied, and the feasibility of its application in the SHINE project is analyzed. The scheme used the fresh-slice method to generate the beam with adjustable spatial distribution, which can effectively improve the longitudinal coherence and stability of the self-seeding output radiation. Through the FEL simulation, we demonstrated that this scheme can produce a highly stable, narrow bandwidth pulse output under the SHINE’s parametric conditions, which will be beneficial to further improve the performance of this device in the future.
	Poster MOPB027 [1.524 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB027
About •	Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 02 November 2023
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MOPB028	Investigation on the Trapped Modes of CPMU at HEPS	damping, impedance, synchrotron, wakefield	62
	S. Yue, J.T. Li, S.K. Tian, N. Wang IHEP, Beijing, People’s Republic of China
	The Cryogenic Permanent Magnet Undulator (CPMU) is a crucial component in synchrotron radiation sources. Due to the small magnet gap of CPMU, the interaction between the beam and its surroundings is strong, which can result in a significant contribution to coupling impedance. In this work, the influence of CPMU on coupling impedance was investigated using wakefield and eigenmode solvers. The results indicated that some of the transverse impedance resonances in CPMU were much stronger than the impedance threshold determined by synchrotron radiation damping, which could cause vertical beam instability. To address this issue, different types of damping materials were investigated through simulations to suppress the resonances.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB028
About •	Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 01 October 2023
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TUPB006	Study on XiPAF Synchrotron Nonlinear Dynamics	resonance, synchrotron, space-charge, injection	92
	X.Y. Liu, P.Z. Fang, Y. Li, X.W. Wang, Z.J. Wang, Y. Xiong, H.J. Yao, S.X. Zheng TUB, Beijing, People’s Republic of China Z.M. Wang NINT, Shannxi, People’s Republic of China
	Funding: Work supported by National Natural Science Foundation of China (No.12075131) Xi’an Proton Application Facility (XiPAF) has been operational since 2020, which can accumulate 2e11 protons after injection and 1e11 protons after acceleration. In this paper, we have investigated the XiPAF synchrotron nonlinearity by simulation and experiments, the beam loss occurs with resonance vx+2vy=5 in the absence of space charge, and resonance 2vx-2vy=0 in the presence of space charge. The stripping foil also plays an important role due to its multiple scattering effect and ionization energy loss effect.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB006
About •	Received ※ 29 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 04 December 2023
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TUPB009	General Design of 180 MHz RFQ for BNCT	rfq, cavity, quadrupole, dipole	99
	Z.Q. Ren, Z. Li, W.L. Liao, P.T. Lin, X.B. Luo, X.J. Pu, X.M. Wan, Y.F. Yang SCU, Chengdu, People’s Republic of China
	Accelerator based boron neutron capture therapy (AB-BNCT) is a promising cancer treatment technology. An overall design have been proposed of a 180 MHz radio frequency quadrupole (RFQ) accelerator for BNCT. The particularity of dynamic design of the RFQ is that the average aperture radius changes along the accelerator. Beam dynamics design results show that the length of accelerator which accelerates protons from 35 keV to 2.81 MeV is 5.07 m, and the transmission up to 99.65%. In terms of radio frequency (RF) structure design, two shapes of cross section of cavity were simulated and compared, i.e., quadrilateral cavity and octagonal cavity. The results show that quadrilateral cavity performed better and was finally selected. Meanwhile, in order to keep the frequency of dipole mode away from the working quadrupole mode, 20 pairs of Pi-mode stabilizer rods are considered. The simulation results show that a large mode separation of more than 20MHz between the operating quadrupole mode and nearest dipole mode can be obtained, this is sufficient to deal with the errors caused by machining and misalignment.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB009
About •	Received ※ 09 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 15 July 2023 — Issued ※ 24 July 2024
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TUPB012	Control of CAFe Beam Energy Using Linear Accelerator Simulation Software AVAS and Beam Line Calibration Technology	cavity, solenoid, cryomodule, operation	105
	C. Jin, C. Feng, Y. He, X. Qi, Z.J. Wang IMP/CAS, Lanzhou, People’s Republic of China
	A new accelerator simulation code named Advanced Virtual Accelerator Software (AVAS) was developed by the Institute of Modern Physics, Chinese Academy of Science. Although the code is proposed to simulate the particle transport in the linac of the China Initiative Accelerator Driven System (CiADS), it can be also used for common linacs. We have constructed a framework for the accelerator simulation program AVAS based on the structure, function, parameters, errors, and operational logic of real accelerators. The mapping relationship between the operating parame-ters and simulation parameters of the Chinese ADS Front-end Demo Linac (CAFe) superconducting sec-tion was successfully established through AVAS. In the testing experiment, AVAS successfully set the operat-ing parameters of the CAFe superconducting section, and the deviation between the energy setting value and the actual measurement value was about 0.5%.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB012
About •	Received ※ 30 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 24 March 2024
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TUPB013	Multipole Field Optimization of X-Band High Gradient Structure	multipole, quadrupole, cavity, acceleration	108
	B.Y. Feng, H.B. Chen, Q. Gao, X. Lin, J.R. Shi, H. Zha TUB, Beijing, People’s Republic of China
	The X-band constant gradient acceleration structure plays a crucial role in the VIGAS project. However, the presence of a multipole field component in the struc-ture’s coupler leads to an increase in ray bandwidth and a decrease in yield, ultimately affecting the quality of the generated rays. Through calculations, it has been determined that the quadrupole field component is particularly prominent in the original structure, ac-counting for 29.5% of the fundamental mode strength. Therefore, it is necessary to modify the cavity struc-ture of the coupler. By altering the shape of the cavity to two staggered circles, the objective of reducing the quadrupole field is achieved. The optimized quadru-pole field component now accounts for approximately 0.3% of the fundamental mode strength. Subsequently, the non-resonant perturbation method was employed to simulate and experimentally measure the magnitude of the multipole field component in the actual acceler-ation cavity.
	Poster TUPB013 [0.350 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB013
About •	Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 27 September 2024
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TUPB014	Design of a Large Momentum Acceptance Gantry Based on AG-CCT for Lightweight Proton Therapy Facility	toolkit, lattice, proton, optics	111
	Y.C. Liao, X. Liu, R.Y. Luo, B. Qin, W. Wang HUST, Wuhan, People’s Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China under Grant 11975107, 12205111. Superconducting (SC) gantry can be applied to proton therapy with significantly reduced footprint and weight. However, the relatively lower ramping limit of the SC magnetic field becomes a bottle-neck for fast energy change and beam delivery. The issue can be mitigated by designing a large momentum acceptance (LMA) beam optics. We present the design of an LMA gantry using AG-CCT SC magnets and symmetrical achromatic lattice. A fast degrader is combined in the design so that the gantry can rapidly switch energy during the treatment. The AG-CCT design process and beam transport simulation are all performed with our homemade integrated code CSPT, which has interfaces to Geant-4 and Opera, and can reach a maximum speed-up ratio of ~450 by applying parallel computation technique. The multi-particle simulation based on realistic field distribution proves that the gantry has a large momentum acceptance of ~20%. Due to its large momentum acceptance, the dispersion effect caused by the scanning magnet is not neglectable. A dispersion compensation method, accompanied by a compact nozzle layout, is proposed to achieve a scanning field of 25×25 cm² with a maximum beam energy spread of 5.2%.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB014
About •	Received ※ 28 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 23 April 2024
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TUPB015	Research on First Harmonic Shimming Method of Cyclotron Based on Least Norm Square Solution	MMI, cyclotron, proton, software	114
	J.R. Lu, S. An, T.J. Bian CIAE, Beijing, People’s Republic of China
	The magnetic field measurement of cyclotron and the shimming of isochronous magnetic field are one of the important links in cyclotron. Due to the influence of factors such as processing errors, installation errors, and inhomogeneity of the magnetic properties of mag-net materials, the main magnetic field of the cyclotron will usually deviate from the required isochronous magnetic field and contain a certain amplitude of the first harmonic magnetic field. The existence of the first harmonic magnetic field will rapidly increase the transverse oscillation amplitude and cyclic emittance of the particles, eventually causing beam loss. In order to improve the beam quality of the cyclotron, the shimming technology of the first harmonic magnetic field is essential. In this paper, through the finite element simulation calculation of the main magnet of the cyclotron, a quantitative algorithm for the first harmonic shimming based on the least norm square solution is proposed. At present, this method is being pre-pared for apply to the magnetic field shimming of the 10MeV high-current proton cyclotron of the CIAE.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB015
About •	Received ※ 29 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 18 September 2023
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TUPB016	High-Fidelity Modeling and Transmission Optimization for the Beamline of HUST-PTF	proton, beam-transport, vacuum, coupling	117
	Y.C. Chen, C.L. Liu, X. Liu, B. Qin, W. Wang HUST, Wuhan, People’s Republic of China
	A superconducting cyclotron-based proton therapy facility is under construction at Huazhong University of Science and Technology (HUST-PTF). In previous works, the vacuum chamber’s shape and the tail effect of the energy spectrum are not considered when calculating the transmission efficiency of the beamline. This study proposes a high-fidelity modeling and optimization method for the HUST-PTF beamline based on Monte Carlo simulation using BDSIM. The modeling procedure of the beamline based on BDSIM is briefly introduced. Then verification of the optical parameters are performed on the gantry sections, and the transmission efficiency of the gantry is optimized by analyzing the unexpected beam loss. After optimization, the transmission efficiency at each energy setting point is calculated. The simulation results show that (1) the proposed optimization method improves the gantry’s transmission efficiency from 92.4% to 95.6%; (2) the transmission efficiency calculated by high-fidelity modeling is more accurate than previous simulations because the beam-matter interaction and practical vacuum chamber geometry are considered.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB016
About •	Received ※ 29 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 09 February 2024
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TUPB018	The Design of Nonlinear Regenerative Extraction in 250MeV Protron Superconducting Synchrocyclotron	extraction, synchro-cyclotron, cyclotron, proton	123
	P.T. Lin, Z. Li, W.L. Liao, X.B. Luo, Z.Q. Ren, X.M. Wan, Y.F. Yang SCU, Chengdu, People’s Republic of China
	The objective of this article is to apply the regenerative extraction system to a 250MeV proton superconducting synchrocyclotron. The parameters of the regenerative extraction system are determined by iteratively calculating the appropriate magnetic field and particle trajectory in the region where the magnetic field and particle trajectories interact. This is then combined with the magnetic channel system to achieve the extraction of the beam from the accelerator. In the article, the particle orbit dynamics analysis and the design of relevant parameters for the regenerative extraction system were successfully implemented using Matlab programming. The simulation results showed that the stability in the vertical direction has the greatest impact on the extraction efficiency and determination of the regenerative magnetic field parameters. In order to maximize the particle extraction efficiency, the radial displacement of particles in the last few turns should pass through two identical nodes.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB018
About •	Received ※ 09 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 04 July 2024
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TUPB019	Beam Dynamics in Superconducting Proton Linac	focusing, quadrupole, acceleration, resonance	126
	X.M. Wan, Z. Li, W.L. Liao, P.T. Lin, X.B. Luo, X.J. Pu, Z.Q. Ren, Y.F. Yang SCU, Chengdu, People’s Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China (Grant Nos. 11375122 and 11875197). Beam loss control is a crucial research direction in high-current superconducting linear accelerators (SCL). The research findings include firstly, for continuous beams, when tune depression eta > 0.7, zero current periodic phase advance (σ0t) can partially exceed 90° during transport in solenoid and quadrupole doublet periodic focusing channels. Different results occur when eta < 0.7. Secondly, in the solenoid system, σ0t can partially exceed 90° without significant impact on beam quality. In the quadrupole doublet focusing system, the partial breakdown of 90° affects beam quality. Thirdly, Similar conclusions hold for acceleration effects. Fourthly, numerical analysis shows that double-period structures have more stringent design criteria than fully period structures. The double-period structure can cause envelope instability even if σ0t < 90°. Fifthly, the primary factor causing halo is the 2:1 resonance. Additionally, when eta is small, higher-order resonances can also cause halo.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB019
About •	Received ※ 09 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 08 April 2024
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TUPB025	Influence of Transverse Distribution of Electron Beam on the Distribution of Proton Beam in the Process of Electron Cooling	electron, proton, storage-ring, scattering	137
	X.D. Yang IMP/CAS, Lanzhou, People’s Republic of China
	Funding: National Natural Science Foundation of China No.12275325 The electron cooling process of 20GeV proton beam in EicC was simulated for the eight transverse distribution of electron beam with the help of electron cooling simulation code. The transverse cooling time was obtained in the different transverse distribution of electron beam. The final transverse distribution of proton beam was demonstrated. The simulated results reveal that the transverse distribution of electron beam influences the distribution of proton beam in the process of electron cooling. In the future, this idea was expected to apply to the longitudinal distribution of electron beam. The longitudinal distribution of proton beam was attempted to be controlled by the longitudinally modulated electron beam. As a result, the peak current and longitudinal distribution of proton beam will be controlled by the electron beam. The loss of proton beams will be reduced, and the stored lifetime of proton beam in the storage ring will be extended. The intensity of the proton beam will be maintained for a longer time.
	Poster TUPB025 [2.048 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB025
About •	Received ※ 28 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 06 June 2024
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TUPB029	Wakefield Studies for the Step Structure and the Skin Depth of Coated Dielectric Tubes	wakefield, electron, impedance, FEL	147
	H. Liu SINAP, Shanghai, People’s Republic of China S. Chen, H.X. Deng, B. Liu, Y.M. Wen SARI-CAS, Pudong, Shanghai, People’s Republic of China J.J. Guo Zhangjiang Lab, Shanghai, People’s Republic of China
	Funding: This work was supported by YSBR-042, 12125508, 11935020, 21XD1404100 and JCYJ-SHFY-2021-010. Wakefield issues are always important research objects in free electron laser (FEL) facilities. Since the wakefield in free electron laser facilities usually leads to a decrease of FEL performance, the research of the wakefield impacts is of great significance. Step structures are almost ubiquitous in the overall undulator section of an FEL facility, which always generate critical wakefields. In this paper, we systematically analyze and summarize the wakefield characteristics of step structures including the step-in structure and the step-out structure. In addition, the skin depth issue of the wakefield is still controversial. We study the skin depth of the wakefield field in the vacuum chamber of the kicker in the SHINE, which is made of the dielectric pipe. We proposed the conception of ¿effective skin depth¿ from two different perspectives and wrote simulation codes to calculate the ¿effective skin depth¿. We hope these methods could provide new mentalities for related research in the future.
	Poster TUPB029 [0.392 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB029
About •	Received ※ 30 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 21 September 2023
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TUPB035	Recent Progress of the Beam Background Experiment in the BEPCII	background, experiment, electron, positron	155
	B. Wang, H.Y. Shi, C.H. Yu IHEP, Beijing, People’s Republic of China
	The Beijing Electron Positron Collider II will upgrade to extend the beam energy and the luminosity by increasing the beam current and slightly compressing the beam size, where the beam energy will be extended from 2.3 GeV to 2.8 GeV and the peak luminosity will be up to 1.1×10³³\rm{cm}^-2\rm{s}^-1 at the optimizing beam energy of 2.35 GeV. The BEPCII upgrade is expected to result in challenging levels of beam related background in the interaction region. An precise simulating and mitigating beam background is necessary to protect the BESIII detector and increase the beam current and peak luminosity. The beam related background at BEPCII is mainly from the Touschek effect and the beam gas effect, this paper presents the recent progress of the beam background simulation and experiment.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB035
About •	Received ※ 06 July 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 22 July 2024
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Paper

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Other Keywords

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MOCXA02

Beam-Beam Interaction with Longitudinal Impedance and Its Application in TMCI Study

impedance, coupling, synchrotron, electron

1

C.T. Lin
IASF, Shenzhen, Guangdong, People’s Republic of China
K. Ohmi
KEK, Ibaraki, Japan
Y. Zhang
IHEP, Beijing, People’s Republic of China

Simulations have showed a novel coherent head-tail instability induced by beam-beam interaction with a large Piwinski angle. The localized cross-wake force has been introduced to explain the instability. The longitudinal impedance would cause coherent and incoherent synchrotron tune shift and distort the particle¿s trajectories in longitudinal phase space. Further beam-beam simulation revealed that the longitudinal impedance has strong impacts on the beam stability, squeezing the horizontal stable tune area seriously. The instability has become an important issue during the designs of CEPC and FCC-ee. In this paper, we develop a transverse mode coupling analysis method that could be used to study beam-beam instability with and without longitudinal impedance. This method can also be applied in synchrotron light sources to study transverse mode coupling instability (TMCI) with longitudinal impedance and harmonic cavity. Some preliminary results at Shenzhen Innovation Light Source (SILF) are also shown.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOCXA02

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Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 23 September 2024

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MOPB001

Terahertz-Driven MeV Electron Bunch Compression and Streaking

electron, FEM, timing, laser

14

Y. Xu, K. Fan, Z. Liu, Y. Song, C.-Y. Tsai, J. Wang
HUST, Wuhan, People’s Republic of China

Electron bunches with ultra-short bunch length and ultra-high timing stability are crucial for various applications. To achieve these desired characteristics, there is a growing interest in employing Terahertz-driven techniques to manipulate and diagnose electron bunches. This paper presents a method capable of compressing and measuring electron bunch lengths. Theoretical and simulation results demonstrate that the bunch length of 54 is reduced to 4 fs by utilizing THz-driven resonant cavity compression, achieving a compression ratio of 13. Furthermore, we also verify the bunch compression using a terahertz-driven streak camera.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB001

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Received ※ 28 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 26 February 2024

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MOPB008

Approximation of Space Charge Effect in the Presence of Longitudinal Magnetic Fields

space-charge, controls, electron, emittance

27

H.Y. Li, H.B. Chen, Q. Gao, W.H. Gu, J.R. Shi, H. Zha
TUB, Beijing, People’s Republic of China

The space charge effect plays a significant role in the evolution of phase space during beam transport. Applying an external longitudinal magnetic field has been shown to effectively reduce beam expansion through the mechanism of beam rotation. In this article, we present a fast approximation algorithm for estimating the impact of an external magnetic field on beam expansion. The algorithm enables efficient computations and provides insights into controlling the phase space dynamics of the beam in the presence of longitudinal magnetic fields.

Poster MOPB008 [0.447 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB008

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Received ※ 30 June 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 30 April 2024

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MOPB016

Matching Section Optics Design for the MeV Ultrafast Electron Beam Experimental Facility

electron, sextupole, quadrupole, dipole

37

H. Qi, K. Fan, Z. Liu, C.-Y. Tsai, J. Wang
HUST, Wuhan, People’s Republic of China

This paper introduces the design and optimization of the matching section beamline for the ultrafast electron research platform at Huazhong University of Science and Technology (HUST). The matching section serves as a connection between the main beamline and the beam physics research beamline, aiming to achieve efficient and precise control over the electron beam trajectory and parameters. To evaluate its performance, particle tracking simulations using GPT software were conducted. When the beam is set at 3 MeV and 1 pC charge, the matching section is capable of compressing the bunch length to approximately 50 fs. This level of compression is crucial for ultrafast electron research applications, as it enables the study of phenomena that occur on extremely short time scales, demonstrating its effectiveness in achieving precise beam control and compression.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB016

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Received ※ 29 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 20 January 2024

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MOPB026

Physical Design for EEHG Beamlines at S3FEL

FEL, electron, undulator, radiation

55

X.F. Wang
Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China
C. Feng, Z. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
X.M. Li, J.T. Sun, Y. Yu
DICP, Dalian, Liaoning, People’s Republic of China
Y.F. Liang, X.M. Yang, H. Yi, L. Zeng, W.Q. Zhang
IASF, Shenzhen, Guangdong, People’s Republic of China

Funding: Work supported by the National Key R&D Program of China (Grant No.2018YFE0203000) and the National Natural Science Foundation of China (Grant No.22288201).
The proposed Shenzhen Superconducting Soft X-Ray Free-electron Laser (S3FEL) aims at generating FEL pulses from 1 nm to 30 nm. At phase-I, two undulator beamlines work at ehco-enable harmonic generation (EEHG) principle. The two undulators will cover the spectral ranges 2.3-15 nm (~83-539 eV) and 5-30 nm (~41-248 eV), respectively, when receiving electrons from 2.5 GeV superconducting linac. However, the generated FEL radiation is sensitive to various electron beam properties, e.g., its energy profile influenced by collective effects such as Coherent Synchroton Radiation (CSR), especially at high harmonics. To generate intense full coherent FEL radiation at ultra-short wavelength, a novel technique of EEHG cascaded harmonic lasing method is also considered. Physical design and FEL performance are described in this paper.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB026

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Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 18 July 2023 — Issued ※ 04 October 2024

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MOPB027

A Scheme of Fully Coherent X-Ray Free Electron Laser for the Shine Based on Fresh-Slices

electron, FEL, radiation, undulator

59

YX. Liu
SINAP, Shanghai, People’s Republic of China
T. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

In this paper, the fresh-slice self-seeding free electron laser scheme is studied, and the feasibility of its application in the SHINE project is analyzed. The scheme used the fresh-slice method to generate the beam with adjustable spatial distribution, which can effectively improve the longitudinal coherence and stability of the self-seeding output radiation. Through the FEL simulation, we demonstrated that this scheme can produce a highly stable, narrow bandwidth pulse output under the SHINE’s parametric conditions, which will be beneficial to further improve the performance of this device in the future.

Poster MOPB027 [1.524 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB027

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Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 02 November 2023

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MOPB028

Investigation on the Trapped Modes of CPMU at HEPS

damping, impedance, synchrotron, wakefield

62

S. Yue, J.T. Li, S.K. Tian, N. Wang
IHEP, Beijing, People’s Republic of China

The Cryogenic Permanent Magnet Undulator (CPMU) is a crucial component in synchrotron radiation sources. Due to the small magnet gap of CPMU, the interaction between the beam and its surroundings is strong, which can result in a significant contribution to coupling impedance. In this work, the influence of CPMU on coupling impedance was investigated using wakefield and eigenmode solvers. The results indicated that some of the transverse impedance resonances in CPMU were much stronger than the impedance threshold determined by synchrotron radiation damping, which could cause vertical beam instability. To address this issue, different types of damping materials were investigated through simulations to suppress the resonances.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB028

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Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 01 October 2023

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TUPB006

Study on XiPAF Synchrotron Nonlinear Dynamics

resonance, synchrotron, space-charge, injection

92

X.Y. Liu, P.Z. Fang, Y. Li, X.W. Wang, Z.J. Wang, Y. Xiong, H.J. Yao, S.X. Zheng
TUB, Beijing, People’s Republic of China
Z.M. Wang
NINT, Shannxi, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China (No.12075131)
Xi’an Proton Application Facility (XiPAF) has been operational since 2020, which can accumulate 2e11 protons after injection and 1e11 protons after acceleration. In this paper, we have investigated the XiPAF synchrotron nonlinearity by simulation and experiments, the beam loss occurs with resonance vx+2vy=5 in the absence of space charge, and resonance 2vx-2vy=0 in the presence of space charge. The stripping foil also plays an important role due to its multiple scattering effect and ionization energy loss effect.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB006

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Received ※ 29 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 04 December 2023

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TUPB009

General Design of 180 MHz RFQ for BNCT

rfq, cavity, quadrupole, dipole

99

Z.Q. Ren, Z. Li, W.L. Liao, P.T. Lin, X.B. Luo, X.J. Pu, X.M. Wan, Y.F. Yang
SCU, Chengdu, People’s Republic of China

Accelerator based boron neutron capture therapy (AB-BNCT) is a promising cancer treatment technology. An overall design have been proposed of a 180 MHz radio frequency quadrupole (RFQ) accelerator for BNCT. The particularity of dynamic design of the RFQ is that the average aperture radius changes along the accelerator. Beam dynamics design results show that the length of accelerator which accelerates protons from 35 keV to 2.81 MeV is 5.07 m, and the transmission up to 99.65%. In terms of radio frequency (RF) structure design, two shapes of cross section of cavity were simulated and compared, i.e., quadrilateral cavity and octagonal cavity. The results show that quadrilateral cavity performed better and was finally selected. Meanwhile, in order to keep the frequency of dipole mode away from the working quadrupole mode, 20 pairs of Pi-mode stabilizer rods are considered. The simulation results show that a large mode separation of more than 20MHz between the operating quadrupole mode and nearest dipole mode can be obtained, this is sufficient to deal with the errors caused by machining and misalignment.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB009

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Received ※ 09 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 15 July 2023 — Issued ※ 24 July 2024

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TUPB012

Control of CAFe Beam Energy Using Linear Accelerator Simulation Software AVAS and Beam Line Calibration Technology

cavity, solenoid, cryomodule, operation

105

C. Jin, C. Feng, Y. He, X. Qi, Z.J. Wang
IMP/CAS, Lanzhou, People’s Republic of China

A new accelerator simulation code named Advanced Virtual Accelerator Software (AVAS) was developed by the Institute of Modern Physics, Chinese Academy of Science. Although the code is proposed to simulate the particle transport in the linac of the China Initiative Accelerator Driven System (CiADS), it can be also used for common linacs. We have constructed a framework for the accelerator simulation program AVAS based on the structure, function, parameters, errors, and operational logic of real accelerators. The mapping relationship between the operating parame-ters and simulation parameters of the Chinese ADS Front-end Demo Linac (CAFe) superconducting sec-tion was successfully established through AVAS. In the testing experiment, AVAS successfully set the operat-ing parameters of the CAFe superconducting section, and the deviation between the energy setting value and the actual measurement value was about 0.5%.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB012

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Received ※ 30 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 24 March 2024

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TUPB013

Multipole Field Optimization of X-Band High Gradient Structure

multipole, quadrupole, cavity, acceleration

108

B.Y. Feng, H.B. Chen, Q. Gao, X. Lin, J.R. Shi, H. Zha
TUB, Beijing, People’s Republic of China

The X-band constant gradient acceleration structure plays a crucial role in the VIGAS project. However, the presence of a multipole field component in the struc-ture’s coupler leads to an increase in ray bandwidth and a decrease in yield, ultimately affecting the quality of the generated rays. Through calculations, it has been determined that the quadrupole field component is particularly prominent in the original structure, ac-counting for 29.5% of the fundamental mode strength. Therefore, it is necessary to modify the cavity struc-ture of the coupler. By altering the shape of the cavity to two staggered circles, the objective of reducing the quadrupole field is achieved. The optimized quadru-pole field component now accounts for approximately 0.3% of the fundamental mode strength. Subsequently, the non-resonant perturbation method was employed to simulate and experimentally measure the magnitude of the multipole field component in the actual acceler-ation cavity.

Poster TUPB013 [0.350 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB013

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Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 27 September 2024

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TUPB014

Design of a Large Momentum Acceptance Gantry Based on AG-CCT for Lightweight Proton Therapy Facility

toolkit, lattice, proton, optics

111

Y.C. Liao, X. Liu, R.Y. Luo, B. Qin, W. Wang
HUST, Wuhan, People’s Republic of China

Funding: This work was supported by the National Natural Science Foundation of China under Grant 11975107, 12205111.
Superconducting (SC) gantry can be applied to proton therapy with significantly reduced footprint and weight. However, the relatively lower ramping limit of the SC magnetic field becomes a bottle-neck for fast energy change and beam delivery. The issue can be mitigated by designing a large momentum acceptance (LMA) beam optics. We present the design of an LMA gantry using AG-CCT SC magnets and symmetrical achromatic lattice. A fast degrader is combined in the design so that the gantry can rapidly switch energy during the treatment. The AG-CCT design process and beam transport simulation are all performed with our homemade integrated code CSPT, which has interfaces to Geant-4 and Opera, and can reach a maximum speed-up ratio of ~450 by applying parallel computation technique. The multi-particle simulation based on realistic field distribution proves that the gantry has a large momentum acceptance of ~20%. Due to its large momentum acceptance, the dispersion effect caused by the scanning magnet is not neglectable. A dispersion compensation method, accompanied by a compact nozzle layout, is proposed to achieve a scanning field of 25×25 cm² with a maximum beam energy spread of 5.2%.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB014

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Received ※ 28 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 23 April 2024

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TUPB015

Research on First Harmonic Shimming Method of Cyclotron Based on Least Norm Square Solution

MMI, cyclotron, proton, software

114

J.R. Lu, S. An, T.J. Bian
CIAE, Beijing, People’s Republic of China

The magnetic field measurement of cyclotron and the shimming of isochronous magnetic field are one of the important links in cyclotron. Due to the influence of factors such as processing errors, installation errors, and inhomogeneity of the magnetic properties of mag-net materials, the main magnetic field of the cyclotron will usually deviate from the required isochronous magnetic field and contain a certain amplitude of the first harmonic magnetic field. The existence of the first harmonic magnetic field will rapidly increase the transverse oscillation amplitude and cyclic emittance of the particles, eventually causing beam loss. In order to improve the beam quality of the cyclotron, the shimming technology of the first harmonic magnetic field is essential. In this paper, through the finite element simulation calculation of the main magnet of the cyclotron, a quantitative algorithm for the first harmonic shimming based on the least norm square solution is proposed. At present, this method is being pre-pared for apply to the magnetic field shimming of the 10MeV high-current proton cyclotron of the CIAE.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB015

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Received ※ 29 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 18 September 2023

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TUPB016

High-Fidelity Modeling and Transmission Optimization for the Beamline of HUST-PTF

proton, beam-transport, vacuum, coupling

117

Y.C. Chen, C.L. Liu, X. Liu, B. Qin, W. Wang
HUST, Wuhan, People’s Republic of China

A superconducting cyclotron-based proton therapy facility is under construction at Huazhong University of Science and Technology (HUST-PTF). In previous works, the vacuum chamber’s shape and the tail effect of the energy spectrum are not considered when calculating the transmission efficiency of the beamline. This study proposes a high-fidelity modeling and optimization method for the HUST-PTF beamline based on Monte Carlo simulation using BDSIM. The modeling procedure of the beamline based on BDSIM is briefly introduced. Then verification of the optical parameters are performed on the gantry sections, and the transmission efficiency of the gantry is optimized by analyzing the unexpected beam loss. After optimization, the transmission efficiency at each energy setting point is calculated. The simulation results show that (1) the proposed optimization method improves the gantry’s transmission efficiency from 92.4% to 95.6%; (2) the transmission efficiency calculated by high-fidelity modeling is more accurate than previous simulations because the beam-matter interaction and practical vacuum chamber geometry are considered.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB016

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Received ※ 29 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 09 February 2024

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TUPB018

The Design of Nonlinear Regenerative Extraction in 250MeV Protron Superconducting Synchrocyclotron

extraction, synchro-cyclotron, cyclotron, proton

123

P.T. Lin, Z. Li, W.L. Liao, X.B. Luo, Z.Q. Ren, X.M. Wan, Y.F. Yang
SCU, Chengdu, People’s Republic of China

The objective of this article is to apply the regenerative extraction system to a 250MeV proton superconducting synchrocyclotron. The parameters of the regenerative extraction system are determined by iteratively calculating the appropriate magnetic field and particle trajectory in the region where the magnetic field and particle trajectories interact. This is then combined with the magnetic channel system to achieve the extraction of the beam from the accelerator. In the article, the particle orbit dynamics analysis and the design of relevant parameters for the regenerative extraction system were successfully implemented using Matlab programming. The simulation results showed that the stability in the vertical direction has the greatest impact on the extraction efficiency and determination of the regenerative magnetic field parameters. In order to maximize the particle extraction efficiency, the radial displacement of particles in the last few turns should pass through two identical nodes.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB018

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Received ※ 09 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 04 July 2024

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TUPB019

Beam Dynamics in Superconducting Proton Linac

focusing, quadrupole, acceleration, resonance

126

X.M. Wan, Z. Li, W.L. Liao, P.T. Lin, X.B. Luo, X.J. Pu, Z.Q. Ren, Y.F. Yang
SCU, Chengdu, People’s Republic of China

Funding: This work was supported by the National Natural Science Foundation of China (Grant Nos. 11375122 and 11875197).
Beam loss control is a crucial research direction in high-current superconducting linear accelerators (SCL). The research findings include firstly, for continuous beams, when tune depression eta > 0.7, zero current periodic phase advance (σ0t) can partially exceed 90° during transport in solenoid and quadrupole doublet periodic focusing channels. Different results occur when eta < 0.7. Secondly, in the solenoid system, σ0t can partially exceed 90° without significant impact on beam quality. In the quadrupole doublet focusing system, the partial breakdown of 90° affects beam quality. Thirdly, Similar conclusions hold for acceleration effects. Fourthly, numerical analysis shows that double-period structures have more stringent design criteria than fully period structures. The double-period structure can cause envelope instability even if σ0t < 90°. Fifthly, the primary factor causing halo is the 2:1 resonance. Additionally, when eta is small, higher-order resonances can also cause halo.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB019

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Received ※ 09 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 08 April 2024

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TUPB025

Influence of Transverse Distribution of Electron Beam on the Distribution of Proton Beam in the Process of Electron Cooling

electron, proton, storage-ring, scattering

137

X.D. Yang
IMP/CAS, Lanzhou, People’s Republic of China

Funding: National Natural Science Foundation of China No.12275325
The electron cooling process of 20GeV proton beam in EicC was simulated for the eight transverse distribution of electron beam with the help of electron cooling simulation code. The transverse cooling time was obtained in the different transverse distribution of electron beam. The final transverse distribution of proton beam was demonstrated. The simulated results reveal that the transverse distribution of electron beam influences the distribution of proton beam in the process of electron cooling. In the future, this idea was expected to apply to the longitudinal distribution of electron beam. The longitudinal distribution of proton beam was attempted to be controlled by the longitudinally modulated electron beam. As a result, the peak current and longitudinal distribution of proton beam will be controlled by the electron beam. The loss of proton beams will be reduced, and the stored lifetime of proton beam in the storage ring will be extended. The intensity of the proton beam will be maintained for a longer time.

Poster TUPB025 [2.048 MB]

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reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB025

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Received ※ 28 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 06 June 2024

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TUPB029

Wakefield Studies for the Step Structure and the Skin Depth of Coated Dielectric Tubes

wakefield, electron, impedance, FEL

147

H. Liu
SINAP, Shanghai, People’s Republic of China
S. Chen, H.X. Deng, B. Liu, Y.M. Wen
SARI-CAS, Pudong, Shanghai, People’s Republic of China
J.J. Guo
Zhangjiang Lab, Shanghai, People’s Republic of China

Funding: This work was supported by YSBR-042, 12125508, 11935020, 21XD1404100 and JCYJ-SHFY-2021-010.
Wakefield issues are always important research objects in free electron laser (FEL) facilities. Since the wakefield in free electron laser facilities usually leads to a decrease of FEL performance, the research of the wakefield impacts is of great significance. Step structures are almost ubiquitous in the overall undulator section of an FEL facility, which always generate critical wakefields. In this paper, we systematically analyze and summarize the wakefield characteristics of step structures including the step-in structure and the step-out structure. In addition, the skin depth issue of the wakefield is still controversial. We study the skin depth of the wakefield field in the vacuum chamber of the kicker in the SHINE, which is made of the dielectric pipe. We proposed the conception of ¿effective skin depth¿ from two different perspectives and wrote simulation codes to calculate the ¿effective skin depth¿. We hope these methods could provide new mentalities for related research in the future.

Poster TUPB029 [0.392 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB029

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Received ※ 30 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 21 September 2023

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TUPB035

Recent Progress of the Beam Background Experiment in the BEPCII

background, experiment, electron, positron

155

B. Wang, H.Y. Shi, C.H. Yu
IHEP, Beijing, People’s Republic of China

The Beijing Electron Positron Collider II will upgrade to extend the beam energy and the luminosity by increasing the beam current and slightly compressing the beam size, where the beam energy will be extended from 2.3 GeV to 2.8 GeV and the peak luminosity will be up to 1.1×10³³\rm{cm}^-2\rm{s}^-1 at the optimizing beam energy of 2.35 GeV. The BEPCII upgrade is expected to result in challenging levels of beam related background in the interaction region. An precise simulating and mitigating beam background is necessary to protect the BESIII detector and increase the beam current and peak luminosity. The beam related background at BEPCII is mainly from the Touschek effect and the beam gas effect, this paper presents the recent progress of the beam background simulation and experiment.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB035

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Received ※ 06 July 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 22 July 2024

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