MOPB —  Poster in Monday   (10-Jul-23   16:55—18:20)
Paper Title Page
MOPB001 Terahertz-Driven MeV Electron Bunch Compression and Streaking 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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MOPB002
 Preliminary Research of Laser-Beam Interaction in Dielectric Structure  
 
  • S.J. Fan
    TUB, Beijing, People’s Republic of China
  
  The acceleration gradient of traditional accelerator has met the threshold due to the RF breakdown effect. Then the concept of DLA (dielectric laser accelerator) was proposed. As a kind of DLA structure, dual-pillar structure was studied in the field of theory, simulation and experiment. Based on CST with PIC simulation in dual-drive acceleration mode, dual-drive deflection mode and single-drive acceleration mode, the results of the distribution of EM field, damage threshold assessment and size of beam bunch are simulated. For dual-drive acceleration mode, the effect of different input phase of bunch on 3D bunch size is discussed. For deflection mode, the effect from EM field and self-interaction force on the transverse velocity is discussed with the variation of the transverse size of the beam observed in simulation. For single-drive acceleration mode, the effect of distribution Bragg reflector on the energy gain of beam and acceleration gradient is discussed based on the comparison of different drive modes. Based on theory and simulation result, possible experiment scheme is preliminary designed, including hundred-micron acceleration experiment based on dual-drive mode.  
poster icon Poster MOPB002 [0.525 MB]  
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MOPB003 Study on a Polarization Controllable Undulator for High-Gain Free Electron Lasers 18
 
  • R. Huang, Q.K. Jia
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  • L.J. Chen
    CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
  
  Funding: Work is supported by National Natural Science Foundation of China (12175224, 11805200)
SASE FEL can generate intense and coherent linearly-polarized X-ray when high energy electron beams travelling through a long planar undulator. It is also of great importance and interest to control the polarization of FEL. One possible solution is utilizing a customized undulator to adjust the magnetic field direction. By tuning the displacement of the magnetic block arrangement, variation of polarization could be achieved. In this paper we study on a polarization controllable undulator to realize the variable polarized magnetic field. Different shapes and design considerations of the magnetic block configuration will be introduced. The value of peak field and the region of good field will be analysed and discussed. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB003  
About • Received ※ 01 July 2023 — Revised ※ 08 July 2023 — Accepted ※ 09 July 2023 — Issued ※ 20 July 2024
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MOPB004 Lowest Longitudinal and Transverse Resistive-wall Wake and Impedance for Nonultra-relativistic Beams 21
 
  • J.Z. Tang
    TUB, Beijing, People’s Republic of China
  
  With the development of the steady-state microbunch(SSMB) storage ring, its parameters reveal that the ultra-relativistic assumption which is wildly used is not valid for the electron beam bunch train. For a bunch train with a length in the 100nm range, spacing of 1um, and energy in the hundred MeV range, the action angle of the space charge force is estimated by {r/γ}. The space charge effect of the mirror current loop formed in the wall with a scale of 1cm will have a sustained effect on approximately dozens of microbunches behind the source particle. The strength of the interaction between such bunches and the potential instability it may cause needs careful evaluation. At the same time, the effect of the space charge inside a single bunch due to space charge effect also needs to be considered. We reorganized the lowest-order longitudinal wakefield under non-extreme relativistic conditions, and modified the inconsistent part in the theoretical derivation in some essays of the lowest-order transverse wakefield. We present the modified theoretical results and analysis. The action area are then divided into three parts. It lays foundation in future research.  
poster icon Poster MOPB004 [1.278 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB004  
About • Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 22 November 2023
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MOPB005 Design of Beam Dynamics for a High-Power DC Proton Accelerator at the MeV Level 24
 
  • Z.-F. He, M.H. Zhao
    SINAP, Shanghai, People’s Republic of China
  • W. Wan
    ShanghaiTech University, Shanghai, People’s Republic of China
  
  This paper aims to design the beam dynamics of a MeV-level high-power DC proton accelerator for use in high-voltage accelerators. The high-power proton accelerator has essential applications such as ion implantation equipment, neutron therapy equipment, and accelerator-based neutron source equipment. With the increasing use of high-voltage generators due to their stable and reliable operation, these accelerators have gained significant popularity in the field. The paper discusses the design considerations of the accelerator equipment, including the functions and requirements of the acceleration tube, electric field distribution, and voltage holding issues. Additionally, the paper focuses on the design aspects of beam optics, encompassing topics such as electric field distribution, beam focusing, beam transmission, divergence, and the impact of space charge effects on beam quality. Calculations and optimizations are performed based on the parameters and requirements specific to high-voltage accelerators. Finally, the paper presents and analyzes the results of the accelerator tube and beam optics design.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB005  
About • Received ※ 30 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 04 October 2024
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MOPB006
 Narrowband Impedance Studies in the HEPS Storage Ring  
 
  • N. Wang, J.T. Li, S.K. Tian, S. Yue
    IHEP, Beijing, People’s Republic of China
  • S. Yue
    University of Chinese Academy of Sciences, Beijing, People’s Republic of China
  
  The High Energy Photon Source (HEPS) is a fourth-generation synchrotron radiation facility with design beam emittance of less than 60 pm. Impedance modeling is an important subject due to the adopted small beam pipe as well as the tight requirements from beam collective effects. Narrowband impedances can be generated by the discontinuity of the vacuum chamber or the finite conductivity of the beam pipe. The coupled bunch instabilities caused by the narrowband impedances could restrict the beam current or perturb the synchrotron radiations. In this paper, the narrowband impedances in the HEPS storage ring are investigated element by element. Their influence on the beam instability and heat load are discussed.  
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MOPB007
 Arbitrary Temporal Shaping of Electron Bunches from a Photocathode Gun  
 
  • T. Wang
    PKU, Beijing, People’s Republic of China
  
  Electron bunches with specific temporal distributions may be used in many fields. As for a photocathode gun, the temporal distribution of electron bunches can be changed by shaping the drive laser. Recently, an advanced drive laser system PULSE (Peking University drive Laser System for Electron source) has been developed. With its temporal shaping module, arbitrary temporal profile adjusting of electron bunches has been demonstrated on the DC-SRF-II photocathode gun. This work presents our study results.  
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MOPB008 Approximation of Space Charge Effect in the Presence of Longitudinal Magnetic Fields 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 icon 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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MOPB009
 Harmonic cavity dynamics studies: efficient methods and new type of Robinson instabilities  
 
  • T.L. He, Z.H. Bai, G.Y. Feng, W.M. Li, W.W. Li, L. Wang
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  In order to cope with the intrabeam scattering effect induced emittance growth, the Touschek scattering effect induced beam lifetime limitation and the beam-impedance coupling effect induced instability growth, harmonic cavities are used to stretch the bunch and provide Landau damping, which has become a necessary choice for modern advanced synchrotron light sources. However, harmonic cavities operated in bunch lengthening mode can cause some adverse effects such as beam loading, Robinson instability, etc., which possibly pose a limitation on the maximum bunch lengthening. This paper will report on our research progress on harmonic cavity dynamics associated with efficient methods for bunch lengthening calculation and new type of Robinson instabilities.  
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MOPB010 Impact of NEG Coating Thickness and Resistivity on Beam Coupling Impedance 30
 
  • T.L. He, Z.H. Bai, W.W. Li, H. Xu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  In diffraction-limited storage rings, non-evaporable getter (NEG) coatings are generally used to assure the ultrahigh vacuum, which, however, also increase the beam coupling impedance that can affect beam dynamics. Ignoring the influence of coating roughness, the impact of NEG coatings on the impedance mainly depends on the coating thickness and resistivity. In this paper, we investigate the impedance characteristics of a round CuCrZr vacuum chamber coated by NEG with different thickness and resistivity.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB010  
About • Received ※ 29 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 12 August 2024  
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MOPB011
 Bunch Adaptive Shaping Based on Spatial Light Modulator  
 
  • Z.Q. Liu, S. Huang
    PKU, Beijing, People’s Republic of China
  
  The second generation of direct current-superconducting radio frequency (DC-SRF-¿) photocathode electron gun drive laser system utilizes a liquid crystal-spatial light modulator (SLM) to generate high-fidelity shaped laser beams with arbitrary spatial profiles by the polarization-mask shaping method. These adaptive lasers are then transmitted to the photocathode of photocathode electron gun can generate electron bunches with special spatial distributions. The electron beams distribution can be produced highly similar to the laser, where space charge is negligible. Based on the electron beams imaging, this work proposes a method for rapidly quantum efficiency (QE) mapping under low-charge conditions, and then using a feedback method by adjusting laser distribution to produce more uniform electron beam. This method can correct irregularities caused by both laser distribution and spatial QE. At present, the experiments have been preliminarily carried out on the DC-SRF-II of Peking University.  
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MOPB013
 Correction of Electron Beam Aberration Due to Multipole Fields in a Continuous-Wave Photocathode Gun  
 
  • H.Y. Jia, S. Huang
    PKU, Beijing, People’s Republic of China
  
  Continuous-wave photocathode guns can deliver electron beams with high repetition rates and high average currents, but their achievable accelerating gradients and cathode fields are relatively low. This leads to a large beam size at the gun exit due to space charge effects, which makes the beam more sensitive to optical aberrations and poses challenges for low-emittance electron beam transmission. This work focuses on the aberration caused by multipole fields. It analyzes the effects of quadrupole, sextupole, octupole and higher order fields on beam shape and transverse emittance, and proposes a beam-based method for rapid characterization and correction of multipole fields. Additionally, an experimental study is being conducted on the DC-SRF-II photocathode gun at Peking University, with corresponding correctors designed for the quadrupole and sextupole fields in the beamline. The experimental results show that the electron beam aberration due to multipole fields can be effectively corrected through appropriate corrector settings, resulting in improved beam symmetry and reduced emittance.  
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MOPB014 Development of a Vlasov Solver for Arbitrary Sub-optimal Lengthening Conditions in Double-RF System 34
 
  • J.Y. Xu, N. Wang, H.S. Xu, Y. Zhang
    IHEP, Beijing, People’s Republic of China
  • C.T. Lin
    IASF, Shenzhen, Guangdong, People’s Republic of China
  
  Solving Vlasov equation is a classic method for analyzing collective beam instabilities. Considering longitudinal impedance and the nonlinear longitudinal potential well, we developed a new Vlasov solver which can be used to study the transverse mode-coupling instability under the arbitrary sub-optimal lengthening and the optimal lengthening conditions in a double-RF system. Several different techniques to deal with the radial direction of longitudinal phase space have been tested. Numerical discretization method is selected in this paper. The development of the solver is presented in details here. Benchmarks and crosscheck of the solver have been made and presented as well.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB014  
About • Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 21 August 2024
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MOPB015
 Optimization Design of Photocathode Injector Assisted by Deep Gaussian Process  
 
  • T. Xin, Z. Sunpresenter
    IHEP, Beijing, People’s Republic of China
  
  The Circular Electron-Positron Collider (CEPC) has high requirements for bunch charge, transverse emittance, and longitudinal length at the injector exit. Consequently, designing a high-performance injector has become a challenge. Therefore, we propose a method of searching in a high-dimensional parameter space using a multi-objective genetic algorithm to optimize the beam at the injector exit ,with an initial charge of 10 nC. Since the full simulation of bunch transportaion with spacecharge effect is extremly time consuming, we adopted the deep Gaussian process as an surrogate model to solve this issue. A total of 16 geometric parameters and 10 beam element parameters have been determined in this paper. We presented an design optimization for an injector consisting of a L-band radio frequency electron gun, a pair of solenoids, and a traveling wave tube. After calculating 6500 effective solutions, and good solutions are observed on the comprehensive performance. The corresponding transverse normalized emittance is 26.14 pi mm.mrad, and the rms beam length is 0.8 mm. Compared with the current design, the beam energy is increased by about 25%,the emittance is reduced by about 70%.  
poster icon Poster MOPB015 [0.563 MB]  
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MOPB016 Matching Section Optics Design for the MeV Ultrafast Electron Beam Experimental Facility 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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MOPB017 Analysis of the Fluctuation of Resonance Driving Terms for Nonlinear Lattice Optimization 41
 
  • B.F. Wei, Z.H. Bai, G.Y. Feng, J.J. Tan
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  Minimizing resonance driving terms (RDTs) of nonlinear magnets is a traditional approach to enlarge the dynamic aperture (DA) of a storage ring. The local cancellation of nonlinear dynamics, which is adopted by some diffraction-limited storage rings, is more effective than the global cancellation. The former has smaller fluctuation of RDTs along the ring. In this paper, the correlation between two kinds of RDT fluctuations is found. The qualitative analysis shows that minimizing the RDT fluctuations is beneficial for controlling the crossing terms and thus enlarging the DA. This qualitative analysis is supported by the statistical analysis of nonlinear solutions of a double-bend achromat lattice.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB017  
About • Received ※ 10 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 11 April 2024  
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MOPB018 Longitudinal Beam Dynamics Design for Super Tau-Charm Facility 45
 
  • L.H. Zhang, J.Y. Tang
    USTC/SNST, Hefei, Anhui, People’s Republic of China
  • S.Y. Li, T. Liu, Q. Luo
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  The project of Super Tau-Charm Facility (STCF) pro-posed in China, as a new-generation high-luminosity e⁺/e⁻ collider in the low-energy region with the center-of-mass energy of 2¿7 GeV, is well underway. The luminosity is targeted at 1.0×1035 cm-2s⁻¹ at the optimized beam energy of 2 GeV. Longitudinal beam dynamics becomes of great importance for the STCF due to the constraints from the novel beam-beam effect called coherent X-Z instability and severe beam collective effects. In this paper, we will develop an iterative optimization model for the STCF longitudinal beam dynamics design, which takes into account the influence of transverse dynamics, coherent X-Z instability, and collective effects.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB018  
About • Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 01 November 2023  
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MOPB019 Development Status of Beam Dynamics Software APES for CEPC 49
 
  • W.B. Liu, Z. Duan, H. Geng, T. Xin, Y. Zhang, Y.L. Zhao
    IHEP, Beijing, People’s Republic of China
  • Y.X. Dai, Z.H. Li, W.B. Liu, M.Y. Su, Y. Zhang
    UCAS, Beijing, People’s Republic of China
  • X.H. Lu
    IHEP CSNS, Guangdong Province, People’s Republic of China
  
  Funding: Innovative Fund of IHEP
The physical design and research work of China Electron Positron Collider (CEPC) is an unprecedented challenge in the field of international accelerator collider. In the simulation research, many physical phenomena must be considered, including large Piwinski angle, crab waist colliding, strong nonlinear effect, energy sawtooth, beam-beam, etc. To address this challenge, a software project APES is proposed in 2021. And this project received support from the IHEP innovative fund in 2022. The progress and future plans of APES project will be introduced in the poster. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB019  
About • Received ※ 05 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 16 September 2024  
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MOPB020
 Investigation of Multipole Field Effects and Cavity Shape Optimization for Lower Emittance in Rf Guns  
 
  • C. Li, W. Wan
    ShanghaiTech University, Shanghai, People’s Republic of China
  • Q. Gu
    SSRF, Shanghai, People’s Republic of China
  
  The presence of multipole fields in an RF gun leads to an increase in the emittance and energy spread of the electron beam. In an RF gun with cylindrical symmetry, when fed through a single port, the quadrupole field components near the axis are larger than the dipole field components. In order to achieve lower emittance and energy spread, it is necessary to study the effect of cavity shape on the multipole fields and eliminate the impact of multipole fields on the electron beam emittance in the RF gun. In this paper, we investigated the multipole field components of three different cavity shapes, and ultimately found that both the racetrack-shaped cavity and the elliptical cylindrical cavity have smaller multipole field components compared to the cylindrical cavity.  
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MOPB021
 Energy Stabilization of High-charge Laser Plasma Accelerator Electron Beams via Hybrid Plasma Dechirper  
 
  • X.Y. Shi, D.Z. Li, J. Wang, H.S. Xu, M. Zeng
    IHEP, Beijing, People’s Republic of China
  
  As the beam quality of laser plasma accelerators (LPAs) improves, potential application of an LPA as the injector of a booster of a synchrotron light source becomes more and more realistic. Even though, it is still very challenging because the energy jitter and energy spread of the-state-of-the-art LPAs are not small enough. There have been proposals, which are successful to suppress the energy jitter and energy spread simultaneously by implementing magnetic chicane together with active dechirper, for relatively low charge conditions (e.g., tens of pC). However, this method is not very effectivewhen the bunch charge becomes an order of magnitude higher due to the heavy beam loading. In this paper, we present a novel method which can suppress the energy jitter and reduce the energy spread simultaneously even with heavy beam loading. Preliminary particle-in-cell (PIC) simulations showed that such a design can reduce the energy jitter and energy spread of the 500 pC bunches from ±2% and 2.39% to less than 0.33% and 0.8%, respectively, with high transmission efficiency (>89%).  
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MOPB023
 A Compact X-ray Light Source Based on a Weak-focus Accelerator  
 
  • Z. Dong, Z.X. Shao, T. Zhang
    USTC, Hefei, Anhui, People’s Republic of China
  
  The X-ray provided by the synchrotron radiation light source becomes an irreplaceable scientific research mean for physics, chemistry, biology, medicine, and other fields. Although there are already many light source facilities around the world, and some new advanced light source facilities are being designed and built, the limited experiment time, high construction cost and huge building scale limit the number of light sources. Accelerator scientists are working on developing new compact light sources. The compact storage ring based on the weak focusing principle is a potential X-ray light source. Desktop Hard X-ray Source is a novel X-ray light source based on compact accelerator. DHXS is composed of an injector, a beam transmission line, and a compact storage ring. The injector of DHXS is a linac, which can provide beam current of about 200mA. The compact storage ring uses a complete combination functional magnet as the main magnet, with a beam orbit radius of only about 15cm. Now DHXS has completed the design, and the entire device size is about 2m * 3m. The preliminary calculation results show that the photon flux can reach above 1E9, and the prototype is under manufacturing.  
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MOPB024
 Accelerator-Based High-Throughput Material Physical Property Measurement System in Terahertz Near-Field  
 
  • Z.X. Shao, Z. Dong, T. Zhang
    USTC, Hefei, Anhui, People’s Republic of China
  • L. Wang, Z.R. Zhou
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  Superconductor, multiferroic material, giant magnetoresistance etc.,are keystones to information, energy, optoelectronics industries. Inside the THz band, their common characteristic properties are all related to the THz complex optical constant, and they also strongly interact with the ultrafast THz waves, resulting in many fascinating phenomena in physics. Applying the combinatorial material synthesis technique, a key step in the Materials Genome Initiative (MGI) project, requires a novel ‘step-less¿high-throughput characterization method that is still unavailable today, mainly because of the diffraction limit of the THz waves. In this program we will develop a new high throughput material characterization system under the THz near-field, integrating with varying magnetic, temperature and electrical fields. The system will directly measure the complex dielectric constant tensor, which correlates directly to the superconductor bandgap, magnetoelectric coupling, resistance and dielectric constant in the THz band, and plasmonic resonance. This system will be useful in the MGI project to realize highly efficient material screening, and will thus very helpful for finding new materials.  
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MOPB025
 Damping Trapped Modes in Vacuum Chamber of Heps in-Air Undulators  
 
  • J.T. Li
    IHEP, Beijing, People’s Republic of China
  
  The HEPS is the fourth-generation light source under construction. For the requirements for high-brightness, a large number of in-air undulators with small gaps will be installed in the storage ring and become one of the important impedance contributors. Photon absorbers will be commonly used in the vacuum chamber of the in-air undulators to shielding the vacuum components downstream which are sensitive to the synchrotron radiations. Due to the existence of photon absorbers, some trapped modes in the transverse planes will be excited by the beam passage. In this paper, a series of numerical simulations are performed to investigate the detailed properties of the trapped modes. In addition, according to electromagnetic field distribution of the trapped modes, damping strategies are investigated to mitigate their influence to the beam instabilities.  
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MOPB026 Physical Design for EEHG Beamlines at S3FEL 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 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 icon 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 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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MOPB029 Multi-bunch Operation Mode for Simultaneously Serving SASE and Seeding FEL Beamlines 66
 
  • X.F. Wang
    Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China
  • X.M. Li, J.T. Sun, X.M. Yang, Y. Yu, W.Q. Zhang
    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
  
  Modern free-electron laser (FEL) facilities are de-signed to simultaneously serve multiple undulator lines to provide x-ray pulses with high peak power and tunable wavelengths. To satisfy different scientific demands, it is preferred to make the separate undulator lines work under different FEL schemes, such as the self-amplified spontaneous emission (SASE) scheme and the echo-enabled harmonic generation (EEHG) scheme. However, different FEL schemes have differ-ent requirements on the beam longitudinal distribu-tion. Here, we propose to use multiple bunches to sim-ultaneously serve the undulator lines and put the bunches at different acceleration phase to change the bunch length with two compressor chicanes. The ac-celeration phase for each bunch is varied by adjusting the time delays of the photocathode drive laser pulses with the accelerator settings unchanged. The start-to-end simulation demonstrates that a fs bunch with high peak current can be produced to serve the SASE line while a bunch with hundred-of-fs length and uniform current distribution can be produced to serve the EEHG line. The FEL performances are simulated and discussed.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB029  
About • Received ※ 25 June 2023 — Revised ※ 10 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 07 September 2024
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MOPB030 Physical Design of an S-Band Cold Cathode RF Gun 70
 
  • T.H. He, H. Xu, K. Zhou, Z. Zhou
    CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
  
  In recent years, the properties of new field emission materials have been gradually improved with the advancement of materials research fields, which have provided the possibility for the research and realization of cold cathode RF guns. A 0.32+1 cell S-band RF gun was designed based on the emission properties of carbon nanotube films and ultra nano diamond films. This article mainly introduces the selection of electron gun cavity, RF design and corresponding thermal analysis. The physical design results basically meet the design requirements.  
poster icon Poster MOPB030 [1.010 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB030  
About • Received ※ 28 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 21 November 2023
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MOPB031 Studies on Beam Injection System for Wuhan Advanced Light Source Storage Ring 73
 
  • Y. Zou, Y. Chen, J.H. He, H.H. Li
    IAS, Wuhan City, People’s Republic of China
  
  Wuhan Advanced Light Source is the low-energy 4th generation advanced light source, proposed by Wuhan University. It includes a 1.5 GeV of full-energy LINAC injector, a 180 m circumference of low-emittance storage ring, and a series of state-of-the-art beam lines. The standard 7BA magnetic focusing structure is adopted for the storage ring to lower the beam emittance and the lattice has been well- designed and optimized by multiple-objective genetic algorithm to maximize the dynamic aperture and energy acceptance. The dynamic aperture of the storage ring at injection can reach up to 10 mm in the horizontal plane, which makes the off-axis beam injection method possible. An off-axis beam injection scheme based on the pulsed nonlinear magnet is to be employed for the storage ring. Detailed studies about the beam injection scheme, including the beam optical design, nonlinear magnet design and optimization, have been performed and multi-particle simulations have also been carried out to study the beam injection procedure.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB031  
About • Received ※ 01 July 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 11 July 2023
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MOPB032
 Simulation of Efficient Interaction Between Terahertz Pulse and Electron Beam  
 
  • L. Wang
    Tsinghua University, Beijing, People’s Republic of China
  
  Free electron laser(FEL) or inverse free electron laser(IFEL) coupling is one of the best options for efficient interaction of electron beam and radiation in the terahertz frequency range, but the slippage effects heavily limit the efficiency. Here we use a waveguide to match the velocities of the terahertz pulse and electron beam, which extends the interaction length and allows a higher energy extraction. We design a GPT custom element to calculate the FEL and IFEL interaction in a waveguide. Under the "zero slippage" condition, it is possible to generate terahertz radiation with the center frequencies of 0.5~1THz. Our results also indicate an average energy efficiency of more than 10%. The waveguide IFEL interaction driven by a near single-cycle THz pulse is studied as well. We discuss its application for acceleration and compression of a relativistic electron beam. Using a terahertz pulse with an energy of about 1 ¿J, our simulation predicts 160keV energy gain of an 8MeV electron beam and compression of a 1ps electron beam in a 0.3m undulator.  
poster icon Poster MOPB032 [0.656 MB]  
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MOPB034 Start to End Simulation for A Compact THz-FEL 76
 
  • R.Y. Luo, Q.S. Chen
    HUST, Wuhan, People’s Republic of China
  
  Funding: This work is supported by the National Natural Science Foundation of China(No.12175077)
An oscillator type terahertz free electron laser (THz-FEL) is under construction at Huazhong University of Science and Technology (HUST). The designed electron beam energy ranges from 8 MeV to 14 MeV, and the radiation frequency ranges from 3 THz to 10 THz. FEL requires high quality electron beams of emittance, energy spread, bunch charge etc. To know the overall facility performance, a start to end simulation (from electron gun to the end of the oscillator) of the THz-FEL is performed. The simulation of the electron gun to the exit of the linac is performed using PARMELA, where the effect of space charge effects is considered. In addition, the effect of beam loading effect is considered for the linac. The transport line is matched and simulated using ELEGANT. GENESIS 1.3 and OPC is used for the lasing process. Results of the simulation are presented and discussed in this paper. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB034  
About • Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 18 October 2024
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MOPB035 Beam Dynamics Study of a Photo-Injector at Wuhan Light Source 79
 
  • Z.Y. Dai, Y. Chen, J.B. Guan, J.H. He, Z. Hui, H.H. Li, L.X. Liu, Z.S. Liu, Y. Nie, J. Wang, J.H. Zhong, W. Zhou, Y. Zou
    IAS, Wuhan City, People’s Republic of China
  • H.C. Shi
    Zhejiang University, Institute for Fusion Theory and Simulation, Hangzhou, People’s Republic of China
  
  A photo-injector is under development at Wuhan Light Source (WHLS) to provide beams for the 1.5 GeV storage ring proposed as a fourth-generation synchrotron radiation light source and a future free electron laser (FEL) facility. The photo-injector and the following LINAC will be able to produce electron beams with low emittance (<2 mm·mrad), high bunch charge (~1 nC), small energy spread (<0.5%) , and short bunch length, which meet the requirements of the ring injection and the FEL operation simultaneously. The injector boosts the bunch energy to 100 MeV, which is mainly composed of a photocathode RF gun working at 2998 MHz, two solenoid coils for emittance compensation, and two 3-meter-long 2998 MHz traveling-wave (TW) accelerator units. Beam dynamics optimization of the photo-injector is presented in detail, which has been performed with multi-objective genetic algorithm (MOGA) combining theoretical analysis and ASTRA code. After optimization, the 95% projected transverse emittance has reached as low as 0.45 mm·mrad with an RMS bunch length of about 1.0 mm at a bunch charge of 1 nC.  
poster icon Poster MOPB035 [2.643 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB035  
About • Received ※ 28 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 12 November 2023  
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MOPB036 Compact Accelerator Light Source for Industrial Applications 82
 
  • Q.L. Zhang, C.L. Li, K. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • Y. Lu
    Zhangjiang Lab, Shanghai, People’s Republic of China
  • K. Wang
    SINAP, Shanghai, People’s Republic of China
  • Y.X. Wang
    UCAS, Beijing, People’s Republic of China
  
  Synchrotron radiation has great application potential in industry. However, the large scale of modern light source has limited it from popular use. Compact accelerator light source has many virtues such as small scale, cost effectiveness, maintenance convenience, etc., which make it a main solution of light source application in industry. The idea has attracted great interests from many institutes, and much effort has been put into its research and development. In this paper we present a design of compact accelerator light source with very small scale. The lattice is very simple to ensure its compactness, while the beam parameters remain flexible to industry needs.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB036  
About • Received ※ 30 June 2023 — Revised ※ 10 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 25 December 2023
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MOPB037 Generalized Longitudinal Strong Focusing: A Ring-Based Beam Manipulation Technique 85
 
  • Z.Z. Li, X.J. Deng, Z. Pan, C.-X. Tang
    TUB, Beijing, People’s Republic of China
  • A. Chao
    SLAC, Menlo Park, California, USA
  
  Generalized longitudinal strong focusing (GLSF), a ring-based beam manipulation technique, has been proposed to generate steady-state, nanometer-long electron bunches in laser-driven storage rings. Coherent EUV radiation can thus be produced with greatly enhanced power and photon flux, benefiting a wide range of scientific and industrial communities. The GLSF mechanism invokes precise transverse-longitudinal coupling dynamics and exploits the ultralow vertical beam emittance. In a GLSF ring, kW-level coherent EUV radiation is attainable.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB037  
About • Received ※ 28 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 20 June 2024
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MOPB038
 Achromatic Beam Design for a Laser-Driven Proton Therapy Accelerator  
 
  • K.D. Wang
    PKU, Beijing, People’s Republic of China
  
  Laser-driven ion acceleration is one of the research hotspots in the field of accelerator in recent years. The high energy ion beam accelerated by laser has the characteristics of small size, narrow pulse width and good directivity, so it has many potential applications. This work will introduce the beam line dynamics design of a laser driven proton radiotherapy planned to be completed by Peking University. The beam line will be used as the key system of the laser proton radiotherapy application demonstration device, and the beam transport system will complete the follow-up operation. The whole beam design can provide horizontal and vertical irradiation modes respectively. It can efficiently collect the large divergence beam generated by the laser. It also contains a complete energy selection system, which can effectively select the energy dispersion of the laser accelerated beam to meet the application requirements. Finally, the beam accelerated by laser passes through the beam transport system to provide a proton beam with a diameter of less than 5 mm and an energy propagation of less than 5% at the horizontal and vertical irradiation targets.  
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MOPB039 Low-Alpha Storage Ring Design for Steady-State Microbunching to Generate EUV Radiation 88
 
  • Z. Pan, A. Chao, X.J. Deng, W.-H. Huang, Z.Z. Li, C.-X. Tang
    TUB, Beijing, People’s Republic of China
  
  A new concept is proposed for minimizing the longitudinal emittance of a low momentum compaction factor (low-alpha) storage ring which has the capability to stably store sub-femtosecond electron bunches for the first time. This storage ring is designed for Steady-State microbunching (SSMB) to generate kW level average power EUV radiation. The proposed design approach can be applied to any quasi-isochronous storage rings to yield very high radiation power due to longitudinal coherence of the radiation. We obtain an optimal lattice design by minimizing global and local momentum compaction factors simultaneously and the result of single-particle tracking shows that the electron beam with equilibrium rms bunch length of about 40 nm can be stored in this ring. Nonlinear dynamics is studied for this lattice.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB039  
About • Received ※ 03 July 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 31 December 2023
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