The electron beam quality determines the main synchrotron radiation characteristics therefore beam diagnostics is of great importance for synchrotron radiation source performance. The real-time processing of the electron beam parameters is a necessary procedure to optimize the key characteristics of the source using feedback loops.
The frequency of electron beam turning in the synchrotron storage ring is about 1 MHz. In multi-bunch mode electrons are grouped into a series of bunches. The bunch repetition frequency depends on the total number of bunches and usually reaches hundreds of MHz. The actual problem is to study multi-bunch beam instabilities.
To solve this problem a high-speed electron beam profile monitor is developed. This device includes a photodetector unit and signal recorder. The photodetector unit is bult on a photodiode strip consisting of 16 integrated avalanche photodiodes. It takes the radiation intensity distribution on the electron beam profile. Electric pulses from the photodiodes are fed to inputs of analog integrators. The integrator operates continuously without reset between two adjacent pulses. Varying continuously the integrator output level consistently takes the value of the every input pulse integral. This technique improves the integrator performance. The integrator is designed for input pulse repetition rate of 200 MHz. The 16-channel signal recorder fixes the integrals values, performs their 12-bit analog-to-digital conversion and buffering in the internal 3 Gb memory. The accumulated data is transferred via Ethernet 100BASE-T.
The device design has been completed. The program shell developing is in progress. The prototype of the analog integrator has been tested. The next stage is the whole device prototyping and testing at Siberia-2 which has a close bunch repetition frequency of 181.6 MHz. The device described must continuously implement 15625000 measurements of the vertical or horizontal electron beam profile at 16 points with a time resolution of 5 ns.