The Study Of The New Type BLM System For The HLSII Storage Ring

The BLM system of an electron storage ring can obtain the position and quantity information of beam loss by detecting the shower electrons, which are produced by electrons impacting on the vacuum chamber wall. This system plays an important role in the troubleshooting, running status monitoring and beam lifetime studying of the ring. Now HLS (Hefei Light Source) is being upgraded to HLSII. Its emittance will be much lower than before; therefore the Touschek scattering will increase significantly and become the dominant factor of beam loss. As the beam loss situation of HLSII will be much more different from that of HLS, it is necessary to build a new BLM system for the new ring.This paper analyzes the distribution features of different kinds of lost electrons, introduces the operation parameters of the new machine and discusses the way to choose proper monitoring positions. Based on these comprehensive analysis, a new BLM system for HLSII is proposed.Because the BLM system detects beam loss indirectly by the shower electrons outside the vacuum chamber, it is necessary to find out the relationship between the shower electrons and the lost electrons. In this paper, the distributions of shower electrons when lost electrons impact on different walls of the vacuum chamber, and how the beam loss monitoring data on a certain wall will be influenced by those electrons lost on other walls have been studied by using Monte-Carlo code EGSnrc. This work will be very useful for preliminary research of the new BLM system like the adjustment of the detectors mounting position and the further processing of the monitoring data.We have discussed the selection of the beam loss detectors’ type, and the technical solution for Data Acquisition System. The PIN photodiode BLMs, which has been successfully employed at DESY is finally chosen for the BLM system of HLSII. A distributed data acquisition system based on Ethernet technology has been designed for the workstation to collect the signals from all of the distributed detectors along the ring of HLSII.This system has been successfully applied in the HLSII storage ring, and been qualified as a strong tool in machine diagnosing, beam lifetime study, and radiation protection.