An Accurate Low Current Measurement Circuit for High-Resolution Energy Spectroscopy Systems
Keywords:
Low beam current, I/V Converter, Operational amplifier, BandwidthAbstract
With the development of radioactive ion beam physics, heavy-ion beams have been applied to the treatment of deep-seated inoperable tumors in the therapy terminal of the Heavy ion Research Facility in Lanzhou (HIRFL) located at the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). An accurate low current measurement circuit was developed to monitor the beam current at 10fA range. The circuit consisted of a low current high sensitivity I/V converter with a dynamic bandwidth. A low offset voltage precision amplifier and new guarding and shielding techniques were used in the I/V converter circuit which allowed as to measure current up to 10fA with a current gain of 0.43 V/fA and noise less than 50 fA. This paper will also show a T-network configuration which was used for boosting bandwidth.
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