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In a typical synchrotron beamline, the interaction of photon beams with different materials generates free electric charges in devices such as ionization chambers, photodiodes, or even isolated metallic structures (e.g., blades, blocks, foils, wires). These free charges can be measured as electric current to diagnose the photon beam intensity, profile, position, or stability. Sirius, the new 3GeV fourth-generation Brazilian light source, may accommodate up to 38 beamlines, which combined will make use of hundreds of instruments to measure such low-intensity signals. This work reports on the design and test results of a transimpedance amplifier developed for low current measurements at Sirius’ beamlines. The device presents low noise, high accuracy, and good temperature stability providing 5 selectable ranges (from 500pA to 7.3mA) to measure bipolar currents achieving femtoampere resolution under certain conditions. Considering low bandwidth applications, the results suggest noise performance comparable to commercial bench instruments. Additionally, the project definitions and plans for the development of a family of low current ammeters will be discussed.
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