Charge Monitoring System With ICT For Accelerator Bunch

High-quality electron beam, which has great charge number, low emittance and high stabilization, plays an important role in physics and application of accelerator. Accelerator laboratory of Tsinghua University is doing research on photocathode RF Gun, in order to get high-quality electron beam in the near future. Beam diagnosis technique is important for improving bunch quality. Bunch charge is an important parameter of electron bunch, and measurement of bunch charge is an important part of beam diagnosis.Our task aims at the beam produced by photocathode RF Gun of Accelerator laboratory, Tsinghua University. We have designed a bunch charge monitor system.Principle and frequently used methods of bunch charge measurement are introduced first. Integrating Current Transformer (ICT) is a pivotal part of the system. Its principle,performance and installation are introduced in the article.Parts of the system after ICT consist of preamplifier, gated integrator, AD converter, data collection module and control circuit. ICT output is amplified by preamplifier, in order to increase Signal-to-Noise. By gated integrator, the current pulse of preamplifier output is integrated into a volt signal which is proportional to the bunch charge. The volt signal is converted into a digital signal which can be transmitted to computer and showed on the screen. Control circuit produces trigger signal and control signal required by the system. With simulation of circuit, design of Printed Circuit Board, test of the system, functions of all parts are achieved.The system doesn't destroy the beam, and it can monitor the bunch charge in the high-radiation environment around accelerator. The results of some off-line tests show that this system is feasible.