Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

Particle-in-Cell Charged Particle Simulations, plus Monte Carlo Collisions with Neutral Atoms, PIC-MCC

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.

https://inspirehep.net/files/1a1b5df14b99817efacbba4f155adbb4

Hefei Advanced Light Source: A Future Soft X-Ray Diffraction-Limited Storage Ring at NSRL

The upgrade project of the Hefei Light Source (HLS), named HLS-II, is under way, which includes the reconstruction of its storage ring. The HLS-II storage ring has lower emittance and more straight sections available for insertion devices as compared with the present HLS storage ring. The scan method is applied to the linear lattice optimization for the HLS-II storage ring to get thorough information about the lattice. To reduce the amount of computation, several scans with different grid spacing values are conducted. In addition, the calculation of the chromatic sextupole strength for the achromatic mode is included in the scan, which is useful for nonlinear lattice optimization. To better analyze the obtained solutions in the scan, the lattice properties and the variables of quadrupole strengths are statistically analyzed. The process of selecting solutions is described in detail, including the choice of the working point, the settings for the emittance and optical functions, and the restriction of maximum magnet strength. Two obtained lattices, one for the achromatic mode and the other for the non-achromatic mode, are presented, including their optical functions and optimized dynamic apertures.

http://iopscience.iop.org/article/10.1088/1674-1137/37/1/017001/pdf

Lattice optimization for the HLS-II storage ring

Automatic data archiving and visualization at HLS-II

As the special machines that can accelerate charged particle beams to high energy by using electromagnetic fields, particle accelerators have been widely applied in scientific research and various areas of society. The development of particle accelerators in China started in the early 1950s. After a brief review of the history of accelerators, this article describes in the following sections: particle colliders, heavy-ion accelerators, high-intensity proton accelerators, accelerator-based light sources, pulsed power accelerators, small scale accelerators, accelerators for applications, accelerator technology development and advanced accelerator concepts. The prospects of particle accelerators in China are also presented.

Particle Accelerators in China

To enhance the performance of Hefei Light Source, which was designed and constructed two decades ago, an upgrade project is undergoing. The detail upgrade scheme was described in this paper. Firstly, the magnet lattice of storage ring should be reconstructed with 4 DBA cells, whose advantages are lower beam emittance and more straight section available for insertion devices. Secondly, the beam diagnostics, main power supply, transverse and longitudinal multi-bunch feedback, beam control and manipulation system would be upgrade to improve the beam orbit stability. Finally, the injection system of storage ring and injector, which is composed of electron linac and beam transfer line, would be updated in order to assure smooth beam accumulation process under new low emittance lattice. With above measures, it is hopeful to increase the brilliance of Hefei Light Source by two orders approximately. INTRODUCTION HLS is a dedicated second generation VUV light source, whose main body is composed of 800MeV electron storage ring, 200MeV linac and beam transfer line. HLS was designed and constructed in the late 1980s; ten years ago, Phase II Upgrade Project was carried out and more beamlines were built successfully. The main parameters of HLS were listed in table 1. There are two factors affecting light source performance: large beam emittance and less number of straight sections. Table 1: Main Parameters of HLS Injection/Operation Energy 200/800 MeV Circumference 66.13m Magnet Lattice 4×TBA RF Frequency 204MHz Transverse Tunes 3.54/2.60 Momentum Compaction 0.048 Energy Loss 16.3keV/turn Beam Intensity 250~300mA Beam Emittance ~160nm⋅rad Parameters of straight section 3.36m×4 = 13.4m Number of undulator 2 MOTIVATION OF UPGRADE VUV synchrotron radiation plays the essential roles in the quantum control, catalysis, combustion and blame, high temperature super-conductivity, etc. Unfortunately, HLS can’t meet the requirements of some advanced SR experiments due to lower brilliance. There are three keys to improve HLS performance: increasing the number of insertion devices, lowering beam emittance and improving the beam orbit stability. UPGRADE OF MAGNET LATTICE Considering theoretical minimum beam emittance and number of straight section, separate function DBA was adopted as the standard cell of ring. Similar to many light sources, the length of straight section in the arc was increased to install undulators. The layout of new magnet lattice is showed in the Figure 1. Two optional focusing parameters were designed, which is named as mode A and mode B. The mode A is an achromatic mode, whose dispersion in the long straight section is zero. In contrast, the mode B is a distributed dispersion mode, whose emittance is smaller than that of mode A. The Figure 2 and Figure 3 displayed the Twiss and dispersion function of two modes. Figure 1: Magnet layout of HLS II storage ring. Work supported by NSFC (10875127 and 10979045) wanglin@ustc.edu.cn ____________________________________________ ork supported by (10875127 and 10979045) anglin ustc.edu.cn WEPEA043 Proceedings of IPAC’10, Kyoto, Japan 2588 02 Synchrotron Light Sources and FELs A05 Synchrotron Radiation Facilities 0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 14 16 18 20 β an d η fu nc tio ns /m Long itud inal positions /m β x β y 10 *η ξ Figure 2: β and dispersion function of mode A. 0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 14 16 18 20 β an d η fu nc tio ns /m Longitudinal positions /m βx βy 10*η Figure 3: β and dispersion function of mode B. Table 2: Main parameters of HLS II Mode A Mode B Operation energy 800MeV Circumference 66.13m RF frequency 204MHz Transverse tunes 4.41/3.21 4.44/3.20 Momentum compaction 0.0205 0.0183 Emittance 36nm.rad 20nm.rad Radiation loss 16.74kev/turn Beam intensity > 300mA Parameters of straight section (4m + 2.3m)×4 = 25.2m

https://epaper.kek.jp/IPAC10/papers/wepea043.pdf

The upgrade project of hefei light source (hls)

The conceptual of Hefei Advanced Light Source, which is an advanced VUV and Soft X-ray source, was developed at NSRL of USTC. According to the synchrotron radiation user requirements and the trends of SR source development, some accelerator-based schemes were considered and compared; furthermore storage ring with ultra low emittance was adopted as the baseline scheme of HALS. To achieve ultra low emittance, some focusing structures were studied and optimized in the lattice design. Compromising of emittance, on-momentum and off-momentum dynamic aperture and ring scale, five bend acromat (FBA) was employed. In the preliminary design of HALS, the emittance was reduced to sub nm ? rad, thus the radiation up to water window has full lateral coherence. The brilliance of undulator radiation covering several eVs to keVs range is higher than that of HLS by several orders. The HALS should be one of the most advanced synchrotron radiation light sources in the world.

http://iopscience.iop.org/article/10.1088/1674-1137/33/S2/033/pdf

Conceptual design of Hefei advanced light source

To enhance the performance of Hefei Light Source, which was designed and constructed two decades ago, an upgrade project would be carried out in the near future. The detail upgrade scheme was described in this paper. Firstly, the magnet lattice of storage ring should be reconstructed with 4 DBA cells, whose advantages are lower beam emittance and more straight section available for insertion devices. Secondly, the beam diagnostics, main power supply, transverse and longitudinal multi‐bunch feedback, beam control and manipulation system would be upgrade to improve the beam orbit stability. Finally, the injection system of storage ring and injector, which is composed of electron linac and beam transfer line, would be updated in order to assure smooth beam accumulation process under new low emittance lattice. With above improvement, it is hopeful to increase the brilliance of Hefei Light Source by two orders approximately. After three‐year upgrade project, the performance of HLS would meet the demands of advanced SR users.To enhance the performance of Hefei Light Source, which was designed and constructed two decades ago, an upgrade project would be carried out in the near future. The detail upgrade scheme was described in this paper. Firstly, the magnet lattice of storage ring should be reconstructed with 4 DBA cells, whose advantages are lower beam emittance and more straight section available for insertion devices. Secondly, the beam diagnostics, main power supply, transverse and longitudinal multi‐bunch feedback, beam control and manipulation system would be upgrade to improve the beam orbit stability. Finally, the injection system of storage ring and injector, which is composed of electron linac and beam transfer line, would be updated in order to assure smooth beam accumulation process under new low emittance lattice. With above improvement, it is hopeful to increase the brilliance of Hefei Light Source by two orders approximately. After three‐year upgrade project, the performance of HLS would meet the demands of adv...

The upgraded scheme of Hefei Light Source

In order to improve the performance of the Hefei Light Source (HLS), in particular to get higher brilliance synchrotron radiation and increase the number of straight section insertion devices, an upgrade project called HLSII will be launched soon. The storage ring lattice, which has a double bend achromatic structure with four periods, comprises eight dipoles, 32 quadrupoles and 32 combined function sextupoles. The design and analysis of the magnets are shown in this paper, along with the optimization of the multipurpose combined function magnet, which consists of three magnets: skew quadrupole, horizontal dipole and vertical dipole, with the main sextupole magnet. This type of magnet is the first one that has been designed and used in China. The mechanical design and fabrication procedures for the magnets are also presented.

The magnet design for the HLS storage ring upgrade project

The Hefei Advanced Light Source(HALS) is a super low emittance storage ring and has a very short beam life time. In order to run the ring stablely, top-up injection will be necessary. The injection system will greatly affect the quality of beam. This article first gives a physics design of the injecting system. Then the injecting system is tracked under different errors. The responses of storage beam and injecting beam are given in the article.

Conceptual design of Hefei Advanced Light Source (HALS) injection system

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