| Beijing Electron Positron Collider (BEPC) is a world leading collider working in the tau-charm energy region, which can also be used as a high performance synchrotron radiation facility. After being upgrated, the new BEPCII is now running in a double ring, multi-bunch and large crossing angle collision mode with a two orders higher luminosity, which at the same time causes a much higher beam realted radiation background that may damage the center beam pipe and subdetectors. BESIII is the large detector of BEPCII. The 12 channel online dose rate monitoring system now running on BESIII,which is an important part of BESIII slow control system, gives a method of background measurement and radiation protection.For the test beam facility as an important part of BEPCII, dose rate monitoring in the target chamber will be significant for all the related experiments and radiation protection; the research of beam background experiments around the key area of BESIII storage ring is of great significance for the better understanding of the mechanism and position of beam lost, which is useful for increasing beam life and decreasing beam background. The analysis gives evidence that the radiation environment of the two objects of experiment measurement is similar to that in BESIII collision zone, thus the same dose rate detector can be used. Based on full research of 12 channel online dose-rate monitoring scheme in Beijing Spectrometer Slow Control System,combined with the actual characteristics and needs in test beam target chamber and the BESIII storage ring ,this paper designed the 16 channel online dose rate monitoring system used for test beam target chamber radiation monitoring and background research. PT1000 temperature sensor and low frequency filter in software in MCU ensure sufficient accuracy of temperature measurement, which makes the dose rate measurement accuracy meeting the engineering requirements; lower computer is composed by FPGA and microprocessor ColdFire5282, which transferd signal data and command with PC through ethernet and serial port.First this paper introduces the meaning of the new version online dose rate monitoring system and the selection of the detectors, then describes the principle design of the system from the software and hardware aspects separately. The hardware sector is focused on the front-end A/D conversion of signal data、FPGA system and the embedded ColdFire5282 system. In the software part, the establishment of embedded uClinux platform、the design of user code in FPGA and MCU、the data processing in Labview is described. Finally, the measurement accuracy test of the new version system and the maintenance and improvement of 12 channel online dose rate monitoring system is given.Through the test of temperature and dose rate measurement accuracy of the system, the results show that the system can meet the expectation functions fully. It has been used in the radiation monitoring in test beam target chamber and the research of background, and some meaningful data has been provided already. |
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