Background: The Beijing Radioactive Isotope Separator Online (BRISOL) is one of the important experimental equipment in the improving project of Tandem accelerator. Its performance is heavily affected by the stability of the weak current measurement system. Purpose: The aim is to develop a robust weak current amplifier for the low level measurement system of BRISOL. Methods: After analyses of the composition and the difficulties of weak beam measurement system in BRISOL

effectual measures were taken to design the weak current amplifier. Many factors that may influence the low current measurement and some design problems were paid special attention to the implementation of this weak current amplifier by using specific design software for circuit layout

programmable logic controllor (PLC) for baseline drift correction

etc. Results: Considerable experimental tests were carried out in a variety of harsh environments for the weak current measurement system in BRISOL

and promising results were achieved. Conclusion: The anti-interference ability and reliability of the weak current amplifier were verified. The performance of the weak current measurement system can meet the requirements of beam diagnostic system. Abstract