Research On Key Technologies Of Photon Beam Position Measurement At HLS

The beam orbit stability is a very important performance index of the synchrotron radiation light source. The stability of the synchrotron radiation beam directly determines the quality of the experimental results. For the users who require the light source with high stability and high-precision, it is very important to measure and stabilize the beam position and angle of the light source. Measuring the position of photon beam mainly relies on the development of Photon Beam Position Monitor(PBPM) and the signal processor for photon beam position. And stabilization of the position of the photon beam depends on the study of the feedback system. In this thesis, the author will study the key technologies of measuring and stabilizing photon beam position for Hefei Light Source(HLS), with the help of the advanced technologies in foreign countries. To be more specific, the aim is to measure the position of photon beam more precision, and to further stabilize the position and angle of specific light source, in order to improve the quality of photon beam.The double blade PBPM, double wire PBPM and the split PBPM usually used in bending beamline can only measure the vertical position of photon beam, but cannot measure the position of photon beam from the horizontal and vertical direction at the same time. So we introduced the four-quadrant PBPM, the product of CETC44, and applied it in machine diagnostic beamline(MDBL) at HLS. The experimental results show that the four-quadrant PBPM is able to measure the position of photon beam from both the horizontal and vertical directions for a long time with great precision and stability.The sensitivity of the double blade PBPM, double wire PBPM and the split PBPM we usually used is greatly affected by the changes of the slit (or the size of photon beam). With the help of the advanced technology in foreign countries, we develop the staggered blade-type PBPM for the first time in China, and propose the application of two new calculation methods, ratio and logarithm ratio, to the signal processing of the staggered blade-type PBPM. The results of theoretical simulation and analysis show that the sensitivity of the staggered blade-type PBPM only relates to its structural parameters and the dimensional changes of the photon beam can be ignored.The HLS has two sets of PBPM system. One is based on VXI Bus PBPM system, which only supports the A/E method and is with a smaller linear range. The other is the homemade log-ratio PBPM system, which only supports two photocurrent signal inputs. Both systems cannot meet the data processing requirements of the newly developed staggered blade-type PBPM. Therefore, we have introduced Libera Photon, a mature commercialized digital signal processor made by IT company in Slovenia, and conduct a study on its application at HLS. It can effectively support multi-channel inputs of photocurrent signal with Log-ratio calculation, and improve the overall performance of the system.The slow feedback system of the storage ring beam orbit at HLS only can feedback and correct the beam position of the ring’s24Beam Position Monitor(BPM), and cannot correct the position and angle of light sources. Although HLS had developed a photon beam position feedback system based on one PBPM, but this system only can feedback the position of the PBPM, the effect is poor for the other positions in the beamline, and this system cannot realize real-time feedback. In order to stabilize the position and angle of particular light source, we develop a new photon beam position feedback system based on two PBPMs, which also can realize real-time feedback. It is workable and effective.Finally, the thesis summarise the key technologies of photon beam position measurement, and provid some advises for the future work.This work is supported by the Natural Science Foundation of China (10675118,11175173).