| Paper | Title | Page |
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| MOPML055 | Preliminary Physics Design of a Linac with the Variable Energy for Industrial Applications | 530 |
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| This paper describes the physics design of a S-band (2856 MHz) linear accelerator (linac) with variable energy tuning. The system consists of a DC gun for generating electron, prebuncher for velocity modulation and two travelling wave (TW) accelerating sections for acceleration. The accelerating structure is a 2'Ð/3 mode constant gradient TW structure, which comprises TW buncher cells, followed by uniform cells. The structure is designed to accelerate 45 keV electron beam from the electron gun to 3.2 MeV, and then 10 MeV. An important feature of the TW linac is that the RF output power of the first linac is as the RF input power of the second linac. Three dimensional transient simulations of the accelerating structure along with the input and output couplers have been performed to explicitly demonstrate this feature. Beam dynamics is performed to calculate the beam parameter. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML055 | |
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| THPAK147 | Super-Period Multi-Bend Achromat Lattice with Interleaved Dispersion Bumps for the HALS Storage Ring | 3597 |
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| We have proposed a multi-bend achromat (MBA) lattice concept, called the MBA with interleaved dispersion bumps, in which two pairs of interleaved dispersion bumps are created in each lattice cell. Due to that many nonlinear effects can be effectively cancelled out within one cell and also many knobs can be used for nonlinear optimization, this MBA concept has given both large dynamic aperture (DA) and large dynamic momentum aperture in the lattice design of the Hefei Advanced Light Source (HALS). In this paper, to further enlarge DA, we extend the concept to the case of a super-period lattice consisting of two cells. In the super-period lattice, there are 1.5 pairs of bumps in each cell. A super-period 7BA lattice is preliminarily designed for the HALS, and a larger DA is obtained. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK147 | |
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| THPAK148 | Preliminary Study of a Nine-Bend Achromat Lattice for a Diffraction-Limited Storage Ring | 3600 |
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In recent years, multi-bend achromat (MBA) lattices have been widely used for the design of diffraction-limited storage rings (DLSRs) being developed around the world as the next-generation storage ring synchrotron sources. To better solve the problem of very serious non-linear dynamics in the DLSR lattice design, recently we proposed a new MBA lattice concept called the MBA lattice with interleaved dispersion bumps *, which was then applied to designing 7BA lattices for the Hefei Ad-vanced Light Source (HALS), with the result showing rather good nonlinear dynamics performance. In this paper, a 9BA lattice also following our MBA concept is preliminarily designed as a possible option for the HALS with a natural emittance of less than 30 pm·rad. Since generally the 9BA lattice can have a much lower emit-tance than the usually used 7BA lattice, the work in the paper will provide an inspiration for the existing third-generation synchrotron sources to upgrade to DLSRs with much lower emittances.
* Zhenghe Bai et al., MOPH13, Proc. SAP2017, Jishou, China, 2017. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK148 | |
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| THPAK152 | Study of GF Symplectic Tracking Method and Compensation for the EPU104 at the HLS-II | 3603 |
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| An elliptically polarized undulator (EPU) was applied to obtain high-brightness coherent synchrotron radiation at the upgraded Hefei Light Source, HLS-II. However, the EPU has serious dynamic effects on the beam performances including close orbit, emittance and dynamic aperture etc. when installed at the storage ring. In order to understand the effects, a Taylor expanded generating method was adopted to generate a fast and symplectic map for particle tracking. As for the compensation of the EPU, striplines were equipped above and below the vacuum chamber to reduce the nonlinear effects. With the symplectic tracking routine and the surface fitting method, different parameters such as dynamic aperture and the driving terms, could be set as the objective function to accomplish the optimization of the EPU. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK152 | |
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| THPMK018 | Design of a rotationally symmetric S-band photocathode RF gun | 4336 |
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| The photocathode RF gun is one of the most critical components for high quality electron beam sources. The asymmetric multi-pole field contributes to the transverse emittance growth and degrades the beam quality. In order to overcome the problem, we propose a novel rotationally symmetric 1.6 cell RF gun to construct the symmetric field in this paper. The concrete proposal is that a coaxial cell with a symmetrical distribution of four grooves is concatenated to the first 0.6 cell at the photocathode end to form a new resonant cell (NRC) to mantain the symmetric multi-pole field in 1.6 cell. Our simulations indicate that 3D multi-pole fields of NRC are with the perfect symmetry. After that, the profile of the RF gun is optimized to improve the shunt impedance and mode separation and make the surface peak electric field at the photocathode end. Our simulations demonstrate promising outlook of using coaxial cell for photocathode RF guns with various applications. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK018 | |
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| THPMK120 | Hefei Advanced Light Source: A Future Soft X-Ray Diffraction-Limited Storage Ring at NSRL | 4598 |
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| To meet the fast-growing demands for high-quality low-energy photon beams, a new synchrotron radiation light source conception was brought forward several years ago by National Synchrotron Radiation Laboratory, which was named Hefei Advanced Light Source (HALS). The dominant radiation of HALS will be located in the VUV and soft X-ray region, which will be complementary with that of SSRF and HEPS. Except for high brilliance, high transverse coherence will be another signature feature of HALS. To achieve these goals, a multi-bend achromat based diffraction-limited storage ring was adopted as the main body of HALS. The general description and preliminary design of HALS will be briefly presented in this paper. Under the support of the Chinese Academy of Sciences and local government, the preliminary research and development (R&D) for HALS is undergoing. Several key technologies will be developed in the R&D project, which will lay good foundation for the construction of HALS. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK120 | |
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| THPMK121 | Design of the Second Version of the HALS Storage Ring Lattice | 4601 |
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| In this paper, a new multi-bend achromat (MBA) lat-tice concept that we recently proposed for diffraction-limited storage rings is described, where two pairs of interleaved dispersion bumps are created in each cell and also most of the nonlinear effects produced by the sextupoles located in these bumps can be cancelled out within one cell. Following this concept, two 7BA lattices have been designed for the Hefei Advanced Light Source storage ring as the second version lattic-es, one with uniform dipoles and the other with nonu-niform dipoles. The latter has a lower natural emit-tance of 23 pm·rad, in which longitudinal gradient bends and anti-bends are employed. The optimized nonlinear dynamics for these two lattices are rather good, and especially the dynamic momentum aperture can be larger than 8% without off-momentum tunes crossing non-structure half-integer resonance lines. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK121 | |
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| THPMK123 | Initial Design on the High Quality Electron Beam for the Hefei Advanced Light Source | 4605 |
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Funding: Work is supported by China Postdoctoral Science Foundation (Grant No. 51627901) and Chinese Universities Scientific Fund (Contract WK2310000063) The Hefei Advanced Light Source (HALS) was proposed as a future soft X-ray diffraction-limited storage ring with a Free Electron Laser (FEL) at National Synchrotron Radiation Laboratory (NSRL). We present a design for a high brightness electron source as an injector of a 2.4 GeV linac-based diffraction limited storage ring and a free electron laser. The electron beams with low emittance and high peak current will be generated from a photoinjector and designed to fulfill the requirement of the HALS. To compress the bunch length and enhance the pulse current, velocity bunching scenario by a deceleration injection phase is designed. Owing to a linear compression, the electron beam is expected to be extremely short with a further magnetic compression. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK123 | |
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| THPMK124 | The Radiation Source for a Pre-Bunched THz Free Electron Laser | 4608 |
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Funding: Work is supported by National Natural Science Foundation of China (Grant No. 51627901) Electron beam, generated in a photoinjector and bunched at terahertz (THz) frequency, will excite the coherent THz radiation when entering an undulator. We present a scheme of the radiation source for the pre-bunched THz free electron laser (FEL). The physical design of electron source is described in detail. The radiation frequency is widely tunable by both the pulse train tuning and the undulator gap tuning. It is simulation proved that the radiation power is greatly enhanced in our scheme. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK124 | |
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| THPMK126 | Numerical Method for Longitudinal Dynamics of a Terahertz Cherenkov Free Electron Laser Driven by a Mev Picosecond Electron Beam | 4614 |
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Funding: Natural Science Foundation of China (11705198, 11775216) China Postdoctoral Science Foundation (2017M622023) Fundamental Research Funds for the Central Universities (WK2310000061) Corrugated or dielectric structures have been widely used for producing electron bunch train or THz radiation source. Recently, a novel scheme of sub-terahertz free electron laser (FEL) from a metallic pipe with corrugated walls driven by a non-ultra-relativistic (<10 MeV) picosecond electron beam was proposed and analyzed using the Vlasov-Maxwell equations. In this paper, we use the dielectric loaded waveguide instead, and a numerical method for the longitudinal beam dynamics and electromagnetics of the FEL interaction is presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK126 | |
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| THPMK127 | Terahertz Smith-Purcell Radiation From the High-Harmonic Component of Modulated Electron Beam From Dielectric Structure | 4617 |
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Funding: Supported by National Nature Science Foundation of China(11705198, 11775216) In this paper, a new radiation scheme, which adopts the high order harmonic of modulated electron beam from dielectric loaded waveguide to excite the Smith-Purcell terahertz (THz) radiation, is proposed and in-vestigated by numerical simulations. The results show that the radiation with frequency close to 1.0 THz is generated, while, the fundamental bunching frequency of electron beam is 0.28 THz. Thus, this scheme offer a new method to get the higher frequency THz radiation. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK127 | |
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| THPMK130 | Study of Beam Instabilities with a Higher-Harmonic Cavity for the HALS | 4623 |
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| Hefei Advanced Light Source (HALS), a diffrac-tion-limited storage ring is on the design. In HALS project, a passive higher-harmonic cavity may be added in order to increase the beam lifetime of the storage ring. When the storage ring is operated with a small momentum compaction, instabilities limit the utility of the high-er-harmonic cavity. In this paper, we run an algorithm (analytic modeling) to consider the Robinson instabilities for normal and superconducting cavity respectively. The Robinson instabilities are predicted with and without mode coupling. Coupled-bunch instability induced by resonant interaction with parasitic longitudinal mode is also considered. The analytic modeling may be used to give rf-cavity parameters that are more conducive to stability. The results show that the storage ring can oper-ate at a higher beam current and the parasitic high-er-order mode of the fundamental cavity has less impact on the beam by using superconducting harmonic cavity. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK130 | |
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| THPMK135 | Corrector Layout Optimization Using NSGA-II for HALS | 4629 |
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| In this paper, we present a method to find the global optimum correctors layout based NSGA-II algorithm when the number of correctors is limited to be equal to the number of BPMs. We prove that this method works well with HALS. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK135 | |
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| THPML124 | Design of Beam Position Fast-Correction Magnet Power Supply for HALS | 4967 |
| SUSPL082 | use link to see paper's listing under its alternate paper code | |
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Funding: Supported by 'Hefei Advanced Light Source Pre-research Project' Hefei Advanced Light Source (HALS) is the fourth-generation radiation light source that is being pre-researched in China. Ultra-low emittance of the beam requires higher performance of power supply system. We designed a fast correcting power supply for the beam measurement needs. We adopted the all-digital method, the current closed-loop feedback used the AD7766 with 24-bit resolution as its A/D converter. And we added the corresponding constant temperature control, chain protection, etc. The small-signal frequency response of this system can reach more than 5kHz. The detail design scheme is described in this paper. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML124 | |
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| THPML134 | Design of the Magnets of the HALS Project | 4998 |
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Funding: Work supported by the National Nature Science Foundation of China under Grant Nos.11375176 * hlxu@ustc.edu.cn ** zhbo@ustc.edu.cn The Hefei Advanced Light Source (HALS) is a future soft X-ray diffraction-limited storage ring at NSRL, this project aims to improve the brilliance and coherence of the X-ray beams and to decrease the horizontal emittance. The lattice of the HALS ring relies on magnets with demanding specifications, including combined function dipole-quadrupoles (DQs) with high gradients, dipoles with longitudinal gradients (DLs), high gradient quadrupoles and strong sextupoles. The combined dipole-quadrupole design developed is between the offset quadrupole and septum quadrupole types. The longitudinal-gradient dipoles are permanent magnets. The quadrupoles and sextupoles rely on a more conventional design. All the magnets have been designed using POSSION, Radia, and OPERA-3D. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML134 | |
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| THPML135 | Design of the Combined Function Dipole-Quadrupoles (DQS) with High Gradients | 5001 |
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Funding: Work supported by the National Nature Science Foundation of China under Grant Nos.11375176 * hlxu@ustc.edu.cn **zhbo@ustc.edu.cn Combined dipole-quadrupoles (DQs) can be obtained with the design of tapered dipole or offset quadrupole. However, the tapered dipole design can not achieve a high gradient field, as it will lead to poor field quality in the low field area of the magnet bore, and the design of offset quadrupole will increase the magnet size and power consumption. Finally, the dipole-quadrupole design developed is between the offset quadrupole and septum quadrupole types. The dimensions of the poles and the coils of the low field side have been reduced. The 2D pole profile is simulated and optimized by using POSSION and Radia, while the 3D modle using Radia and OPERA-3D. The end shimming and chamfer are modelled to meet the field uniformity requirement. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML135 | |
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| THPML136 | Study of Secondary Electron Generation and Transport in Diamond | 5004 |
| SUSPF025 | use link to see paper's listing under its alternate paper code | |
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| Energetic primary electrons (~ keV) impinging on the diamond film with its both surface under bias field in ~ MV/m, will excite secondary electron (SE) response including SE generation & transport. Although there have been 3D Monte Carlo (MC) simulation to study the two processes, this paper will introduce another method. Based on optical dielectric model, 3D MC simulation was implemented to study the generation process, and SE generation function was obtained by fitting the calculations. Using this function, the diffusion-drift equation of charge carriers (electron and hole) can be solved in 1D for the transport process, and the variation of SE depth distribution with time can be obtained. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML136 | |
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