Design of Support for BPM Displacement Measurement System for Half and EPICS Connection
59
C.H. Wang, P. Lu, B.G. Sun, L.L. Tang, T.Y. Zhou
USTC/NSRL, Hefei, Anhui, People’s Republic of China
The beam orbit stability is an important parameter to measure the stability of the synchrotron radiation source. As for the fourth-generation storage ring, the emittance and beam size continue to decrease and higher requirements are being put for-ward for beam orbit stability. There are two main factors that affect the stability of the beam orbit. One is the vibration of the ground and other systems, which requires highly mechanically stable support. The other is due to synchrotron radiation and changes in ambient temperature, which lead to the expansion and deformation of the vacuum chamber, causing BPM movement and misjudging the position of the beam orbit. The misjudging will introduce errors in the orbit feedback system and decrease the stability of the beam orbit. Therefore, a set of offline BPM (beam position monitor) displacement measurement system with high stability was built. However, considering the adverse effect of the INVAR36 on magnetic field and the drift of the displacement data, we added carbon fiber to the new support for BPM displacement measurement probes. Besides we realized the function of real-time reading BPM displacement data through EPICS. This article mainly introduces the support design and EPICS connection of the BPM displacement measurement system.
The Design of a Fast Orbit Feedback System for Hefei Advanced Light Facility
Y.L. Li, B.G. Sun
USTC/NSRL, Hefei, Anhui, People’s Republic of China
In order to improve the stability of the beam orbit, the fast orbit feedback system (FOFB) is employed to eliminate the undesirable interference from various sources. The paper will present the design of the design of the global Fast Orbit Feedback for Hefei Advanced Light Facility (HALF). The FOFB system aims to stabilize the electron beam position towards an ideal electron beam orbit. The FOFB system employs high-speed board series PXIe-7902 board of National Instruments (NI) to realize the design of the communication controller (CC) and the algorithm calculation. The PXIe-7902 called cell has a built-in Xilinx Virtex-7 586T and 24 two-way digital channels. Which allows connecting 12 Liberal BPMs at most to receive the beam position values. A two-tier communication architecture is applied in the CC design. The beam position monitors are directly connected to cell and do not communicate each other. Which liberates the tasks of BPMs and make the task concentrated on the cell. The correction output is connected to the power supply to adjust the correctors to reach beam stability.
In this paper, a quad-slits interferometer using visible light is designed to measure the transverse beam size of Hefei Light Source-II (HLS-II). According to the beam parameters of the B7 source point, the preliminary simulation results are obtained by using the Synchrotron Radiation Workshop (SRW) code. Furthermore, the core parameters of the quad-slits components in the interferometer are optimized. Among, the optimum slits-separations of dH and dV are acquired to be 6.0 mm and 10.0 mm, respectively. It is shown that the simulated results are consistent with the theoretical values, which provides a reference value for performing the related experiments in the future.
Observation and Analysis of Island Phenomenon in the Storage Ring Light Source
373
Y.K. Zhao, S.S. Jin, P. Lu, B.G. Sun, L.L. Tang, J.G. Wang, F.F. Wu, T.Y. Zhou
USTC/NSRL, Hefei, Anhui, People’s Republic of China
In the previous experimental investigations and measurements using the radio-frequency (RF) phase modulation method to study the longitudinal beam characteristics of the Hefei Light Source-II (HLS-II), we found that the longitudinal bunch distributions under different modulation frequencies and amplitudes have great difference. In order to further explore island phenomenon and better understand beam motion associated with external RF phase modulation, the streak camera is exploited to effectively observe the longitudinal bunch profile and distribution in single-bunch filling mode. In addition, the dependence between island size, bunch dilution effect and modulation frequency are also discussed in detail. This is meaningful for researching the impact of RF noise on longitudinal beam dynamics, beam manipulation, and machine maintenance and debugging.
Design and Simulation of the Coupling Structure for Single Resonant Cavity Bunch Length Monitor
377
H.X. Tuo, P. Lu, Q. Luo, B.G. Sun, F.F. Wu, T.Y. Zhou
USTC/NSRL, Hefei, Anhui, People’s Republic of China
The measurement of the bunch length can better realize the monitoring of the beam, because the bunch length is one of the important longitudinal parameters of the beam. In this paper, a new single-cavity bunch length monitor is proposed, whose coupling structures consist of two kinds of filters. One is a low pass filter, the other is a band pass filter. The coaxial low-pass filter is used to couple out lowfrequency signals, and the band-pass filter is used to couple higher-frequency signals. According to the beam characteristics of the National Synchrotron Radiation Laboratory (NSRL)based on the tunable infrared laser energy chemistry research large-scale experimental device (FELiChEM), we perform simulation in CST. The simulation results show that the monitor can measure the bunch length of the FELiChEM device very well, and the simulation measurement error is less than 2%.
High Speed Parallel Digital Signal Processing Structure in Bunch-By-Bunch Position Measurement Based on FPGA
434
R.Z. Wu, P. Lu, B.G. Sun, L.L. Tang
USTC/NSRL, Hefei, Anhui, People’s Republic of China
In storage ring, the measurement of bunch-by-bunch positions can help to obtain abundant beam dynamics characteristic information, diagnose the instability of beam motion and provide a basis for the suppression of instability. However, the measurement of bunch-by-bunch requires one analog-to-digital converter (ADC) with high sampling rate and one processor with fast digital signal processing (DSP)ability. With the development of electronics, high sampling rate ADCs are no longer a problem. Therefore, high-speed DSP has become the key. In this paper, a parallel digital signal processing architecture based on polyphase decomposition is proposed. This architecture realizes the GHz DSP speed on the programmable gate array (FPGA), which can be used as the infrastructure of high-speed DSP in the bunch-by-bunch position measurement system.
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R.Z. Wu, P. Lu, B.G. Sun, L.L. Tang, Y.G. Wang, F.F. Wu, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People’s Republic of China
In order to improve the performance of Hefei Light Source (HLS-II), it is necessary to study various problems of nonlinear beam dynamics in the storage ring, so as to optimize the beam filling mode and injection mode, and then improve the intensity and brightness of HLS-II. In beam dynamics, bunch-by-bunch can provide detailed information of beam bunches and help beam researchers to study the problems of beam bunches deeper. Therefore, HLS-II diagnostics group has developed an on-line bunch-by-bunch three-dimensional measurement system based on high bandwidth and high speed oscilloscope.
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