HLS-II Storage Ring Research Articles

Research on fusion and deformation analysis of decade' HLS-II control network surveying data

To ensure the long-term stability of the beam and further construction needs, it is necessary to re-measure the particle accelerator regularly. Since 2013, we have been measuring the HLS-II control network with laser trackers and the level for 10 years. Taking HLS-II as the object of study, we introduced the data acquisition strategy for the period of 2013–2023. We analyzed the horizontal and vertical deformation trends of each control point. In the vertical direction, we fused the geometric level and elevation data of the laser tracker network by using MC-GMM (a Gauss-Markov model which considers the uncertainty of Monte Carlo simulation). The analysis results show that, after the HLS upgrade, the annual average settlement of the ground control network tends to be stable. The settlement and horizontal variation of the device are all within a reasonable and controllable range. To ensure stability, accuracy, and efficiency in the measurement, we recommend employing the laser tracker for the re-measurement of the HLS-II storage ring. The data processing flow and methods mentioned in the article can provide a reference for deformation analysis of the upcoming construction of the Hefei Advanced Light Facility (HALF) and other large-scale metrology projects.

Beam Injection Using a Nonlinear Kicker for the HLS-II Storage Ring

The single nonlinear kicker (NLK) injection has been adopted by several synchrotron radiation light source facilities or their upgrades. The injected beam receives a kick from an NLK and goes into the acceptance of the storage ring while the stored beam passes through the center of the NLK where the magnetic field is almost zero. Compared with the local-bump injection, NLK injection requires less space for kickers and causes less disturbance to the stored beam during injection. Currently, a conventional local bump injection including four pulsed dipole kicker magnets is adopted in the HLS-II storage ring. In this paper, we propose an NLK injection scheme by only replacing one kicker with a pulsed NLK for HLS-II. The simulation result is also presented.

Effective improvement of beam lifetime based on radiofrequency phase modulation at the HLS-II storage ring

A radiofrequency (RF) phase modulation method is applied to the Hefei Light Source II storage ring to deeply investigate its longitudinal beam characteristics and improve the beam lifetime. A theoretical analytical model and corresponding experimental measurements of single bunch length and island phenomena are examined. From a series of online machine experiments, we demonstrate that the suitable phase modulation amplitude is 0.02 rad, corresponding to an optimum modulation frequency ranging from 19.6 to 20.7 kHz of the RF system. Furthermore, the overall beam lifetime can be increased by a factor of 2.38 as a result of the beam dilution effect.

Optimization of a Low-alpha Lattice for the HLS-II Storage ring

To generate terahertz radiation at HLS-II, a low-αc lattice scheme is proposed. The new lattice can reduce the bunch length in the storage ring, thus enhancing the coherent synchrotron radiation in the THz region. In this paper, the design and optimization of a low-αc lattice is reported. The new lattice preserves the symmetry of nominal lattice and reduces the first and second order momentum factor at the cost of increasing maximum β function and natural emittance. The bunch length is tracked and the result shows that the low-αc lattice can effectively compress bunches in the storage ring. The performance of this low-αc lattice can be further studied and improved.

Embedded EPICS based beam loss monitor system of HLS-II storage ring

A new beam loss monitor system based on embedded EPICS is developed for the top-off upgrade of HLS-Ⅱ, to monitor the position and value of beam loss of storage ring. The electron shower signals are obtained by the double PIN photodiode detectors around the storage ring, then acquired by the new BLM processors, where the beam loss signals are analysed and distributed to the accelerator control network, by embedded EPICS on embedded Linux system of the BLM processors, and the beam loss data could be obtained in the central control room. The new BLM system could actuate the self-checking function of the double PIN photodiode detectors, eliminate hidden malfunction of the detectors, and improve stability and reliability of the whole system. Preliminary operation shows that the new BLM system can meet the needs of the top-off upgrade of HLS-Ⅱ.

Lattice Tweaking Using A Tune Knob Based On Global Mechanism

The transverse tunes are important parameters for a storage ring and tune knobs are used to adjust the tunes in a specific range. Usually for large rings, a set of quadrupoles is set on the straight sections for the use of tune knob. A tune knob has been designed for the HLS-II storage ring without affecting the twiss parameters of the injection section. This paper introduces the design and online test of this tune knob. The quadrupoles are adjusted according to the simulation results and the tunes are measured and calibrated. The online test results show that the tune knob design works well on the HLS-II storage ring and can be applied for various machine studies.

The Development of Tune Measurement System Based on FPGA at HLSII Storage Ring

The Development of Tune Measurement System Based on FPGA at HLSII Storage Ring

Smoothing analysis of HLSII storage ring magnets**Supported by National Natural Science Foundation of China (11275192) and the Upgrade Project of Hefei Light Source

Hefei Light Source (HLS) has been upgraded to improve the quality and stability of the synchrotron light, and the new facility is named HLSII. However, a final accurate adjustment is required to smooth the beam orbit after the initial instalment and alignment of the magnets. We implement a reliable smoothing method for the beam orbit of the HLSII storage ring. In addition to greatly smoothing and stabilizing the beam orbit, this method also doubles the work efficiency and significantly reduces the number of magnets adjusted and the range of the adjustments.

Development of tune measurement system for HLS-II storage ring

介绍了在合肥光源重大维修改造工程期间，开发的一套基于扫频激励法的工作点测量系统。测量系统硬件包括基于条带BPM的信号拾取电极、前端信号调理模块、一台带跟踪输出的信号分析仪N9000AEP、功率放大器以及用于激励束流的条带激励器。系统控制软件采用EPICS开发，基于EPICS Stream Device设计的输入输出控制器(soft IOC)运行在服务器虚拟机中，通过VXI11协议进行通信实现对信号分析仪的控制和数据获取；用户操作界面采用EPICS平台下的EDM开发，通过Channel Access与IOC通信。在HLS-II储存环上对工作点测量系统进行了在线的调试。调试结果说明，在扫频范围为2.1 MHz到4.1 MHz时，工作点测量系统的统计分辨率在水平方向上好于0.000 3，在垂直方向上好于0.000 2。

Central RF frequency measurement of the HLS-II storage ring**Supported by National Natural Science Foundation of China (11105141, 11175173) and the upgrade project of Hefei Light Source

Central RF frequency is a key parameter of storage rings. This paper presents the measurement of central RF frequency of the HLS-II storage ring with the sextupole modulation method. Firstly, the basis of central RF frequency measurement of the electron storage ring is briefly introduced. Then, the error sources and the optimized measurement method for the HLS-II storage ring are discussed. The workflow of a self-compiled Matlab script used in central RF frequency measurement is also described. Finally, the results achieved by using two data processing methods to cross-check each other are shown. The measured value of the central RF frequency demonstrates that the circumference deviation of the HLS-II storage ring is less than 1 mm.

Broadband impedance calculations and single bunch instabilities estimations of of the HLS-II storage ring**Supported by Natural Science Foundation of China (11175182, 11175180)

The upgrade project of the Hefei Light Source storage ring is under way. In this paper, the broadband impedances of resistive wall and coated ceramic vacuum chamber are calculated using the analytic formula, and the wake fields and impedances of other designed vacuum chambers are simulated by CST code, and then a broadband impedance model is obtained. Using the theoretical formula, longitudinal and transverse single bunch instabilities are discussed. With the carefully-designed vacuum chamber, we find that the thresholds of the beam instabilities are higher than the beam current goal.

Magnetic Field Measurement of the Quadrupole and Sextupole Magnets for HLS-II Storage Ring

The Hefei Light Source upgrade project (HLS-II) contains 8 dipoles, 32 quadrupoles (2 spares), and 32 sextupoles (2 spares) for the storage ring. Magnets were manufactured and magnetic measurements were performed in collaboration with the Institute of High Energy Physics (IHEP), China. Magnet production and validation measurements were finished in December of 2012. Measurements for all quadrupole and sextupole magnets were performed using a harmonic coil magnetic measurements system. This paper describes the magnets and the measurement system and presents results for the integrated field strength, higher order multipole components, offsets between the mechanical and magnetic centers, and the effective length of the multipole magnets.

Lattice study for the HLS-II storage ring

The Hefei Light Source (HLS) is undergoing a major upgrade project, named HLS- II, in order to obtain lower emittance and more insertion device straight sections. Undulators are the main insertion devices in the HLS- II storage ring. In this paper, based on the database of lattice parameters built for the HLS- II storage ring obtained by the global scan method, we use the quantity related to the undulator radiation brightness to more directly search for high brightness lattices. Lattice solutions for achromatic and non-achromatic modes are easily found with lower emittance, smaller beta functions at the center of the insertion device straight sections and lower dispersion in nonzero dispersion straight sections compared with the previous lattice solutions. In this paper, the superperiod lattice with alternating high and low horizontal beta functions in long straight sections for the achromatic mode is studied using the multiobjective particle swarm optimization algorithm.

Design and optimization of a longitudinal feedback kicker cavity for the HLS-II storage ring

In the Hefei Light Source (HLS) storage ring, multibunch operation is used to obtain a high luminosity. Multibunch instabilities can severely limit light source performance with a variety of negative impacts, including beam loss, low injection efficiency, and overall degradation of the beam quality. Instabilities of a multibunch beam can be mitigated using certain techniques including increasing natural damping (operating at a higher energy), lowering the beam current, and increasing Landau damping. However, these methods are not adequate to stabilize a multibunch electron beam at a low energy and with a high current. In order to combat beam instabilities in the HLS storage ring, active feedback systems including a longitudinal feedback system (LFB) and a transverse feedback system (TFB) will be developed as part of the HLS upgrade project, the HLS- II storage ring project. As a key component of the longitudinal bunch-by-bunch feedback system, an LFB kicker cavity with a wide bandwidth and high shunt impedance is required. In this paper we report our work on the design of the LFB kicker cavity for the HLS- II storage ring and present the new tuning and optimization techniques developed in designing this high performance LFB kicker.

Lattice optimization for the HLS-II storage ring

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.