Based On The Beam Collimation System Development And Related Research

The stability of the electron beam orbit is extremely important to the synchrotron radiation storage ring. The paper developed the beam-based alignment (BBA) system which settled the stable reference orbit for the storage ring of Hefei Light Source (HLS). The Experiments on the instability of the beam orbit, from which the sources of the instability were expected to be discovered, was also involved in this paper. Moreover, the different applications of the digital beam position processer Libera, which contributed in BBA system, were carried out. Many experiments of these applications using Libera were done in this paper.The magnetic centers of the quadrupoles in the electron storage ring are expected to be estimated accurately. When the electron beam misses the magnetic center of a quadrupole when passing it, the beam will encounter the quadrupole's magnetic field which will cause distortion to the beam orbit; and the instability of the power supply will be coupled to the beam orbit consequently. The beam position monitors (BPM) were installed in the storage ring adjacent to quadrupoles at HLS. Therefore, a BPM can be used to label its neighbour quadrupole's magnetic center. Such technique was named beam-based alignment. It is extremely important to label all the quadrupoles' center precisely at HLS since the probability, that there occurs the relative movement between the quadrupole and its neighbour BPM, can be very high because quadrupoles and BPMs do not share one same underpinning.BBA has two different implementation methods: DC k-modulation and AC k-modulation. Large k modulation rate is required when using DC k-modulation to ensure that the BPM can detect the beam orbit variation. However, large k modulation rate will cause large disturbance to the beam orbit which reduces the measurement accuracy. Hysteresis effect also damages the accuracy of the result by DC k-modulation. Measurement error was 100 μm (RMS) when the modulation rate reached 1.5%. In this paper the algorithm was optimized when using DC k-modulation. BBA using AC k-modulation can work with a rather small modulation rate (0.5%). The hysteresis effect does not affect the measurement much when using AC k-modulation. In this paper, a newly designed BBA system was developed after successfully applied large current modulation, PC interface, beam position signal sampling and digital signal processing algorithm. The measurement result error was about 20 pan (RMS) durring system testing experiment. The magnetic centers of the quadrupoles measured by the BBA system played very important role in the slow feedback system.The beam orbit at HLS was drifting all along while the storage ring was operating. To study this phenomenon, the displacement and the temperature variation of the BPM chamber were traced in this paper. By analyzing the tracing results, the main reason that explained the drifting phenomenon was found in this paper, the possible solution to suppress the orbit drifting was proposed.During the development of the BBA system, quadrupole k-modulation was used to measure Beta function value. Digital beam position processor Libera was also discussed in this paper. Several experiments, such as tune measurement, dumping time constant measurement, phase space measurement, were implemented with Libera. To fulfil the tune measurement experiment, a new narrow-band white noise generator, which was based on FPGA and DAC, was designed and applied in this paper to stimulate the electron beam.This work was supported by the Natural Science Foundation of China (10275062 & 10675118).