| Hefei light source (HLS) LINAC was built in 1989. Beam transverse position was observed by fluorescent target, which is a beam-intercept device, has a poor precision and is difficult to digitalize results for further control and processing. So a new beam position monitor (BPM) is to be design for HLS LINAC, which is not beam-intercept, has a good precision and is easy to digitalize results for further processing. This paper is about developing BPM system for HLS LINAC. It is concerned that the BPM system developed can be used at further soft X-ray free electron laser (FEL) device. This paper includes outline of LINAC BPM systems, proposal for HLS HLS LINAC BPM system, theoretical analysis of strip line BPM, design of strip line BPM electrodes, developing of BPM signal processing system, mapping of strip line BPM system, and on-line measurement experiment of strip line BPM system.Chapter one introduces the history of LINAC and its beam measurement, structure of BPM system and the main parameters of BPM systems. Then LINAC BPM system applications are introduced based on two examples such as KEKB and Spring-8 LINAC BPM systems. At last we introduce the present control system of HLS LINAC and make a prospect of upgrade for HLS LINAC BPM system.Chapter two analyses three BPM structures such as button BPM, strip line BPM, cavity BPM and several BPM signal processing proposals such as difference sum ratio, logarithmic ratio, amplitude phase transformation, digitally receiving processing. Taking account of environment and beam characteristic of HLS LINAC, we determine strip line BPM and logarithmic ratio processing as HSL LINAC BPM system proposal. Strip line BPM has a higher signal amplitude, a higher signal noise ratio and a higher space resolution. Logarithmic ration proposal has a rather good response linearity, a big dynamic range and a low cost.Chapter three analyses electromagnetic field of charge with a relativity velocity, mirror charge theory and BPM sensitivity. Then we talk about influence of beam size and nonlinearity to BPM result, and coupling of strip line BPM electrodes.Chapter four introduces application of computer aid design (CAD) in LINAC structure design, design of strip line BPM based on Mafia and measurement of BPM characteristic parameters such as matching resistor, port reflection, time domain response, frequency domain response and strip line coupling. Results show that the strip line has a characteristic resistor of about 50Ω, a reflection of -1.8dB, a bandwidth of 400MHz and a coupling of better than 25dB.Chapter five introduces developing of BPM signal processing system, which consists of front end module, logarithmic detector module, signal acquisition module and software module. The signal processing system has a working frequency of 2856MHz, a processing bandwidth of 10MHz, a detector dynamic range of 40dB, a detector sensitivity of 43.6mV/dB, a trig delay time of 0~1μs and a sampling rate of more than 100Hz. Off-line error measurement shows that the 16-bit system has a 1σ error of not more than 20μm, and 12-bit system has a 1σ error of not more than 30μm.Chapter six introduces BPM mapping methods, mapping bench and control software for HLS LINAC BPM. Mapping results show that strip line BPM has a horizotal sensivity of 1.552 dB/mm and a vertical sensitivity of 1.476 dB/mm. The electric center of BPM has a offset (0.212, 0.450) mm to mechanical centor.
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