Preliminary Design of Bipolar Current Source with High Stability and Low Noise for Driving Coil of Magnets in Accelerators

Bipolar current sources with a stability better than 10 ppm over ±5A output range are demanded driving magnets coil in accelerators. The stability of the output current will directly affect the stability of the accelerator beam, which in turn affects the stability of particle targeting. However, almost none of the existing current source instruments are specifically optimized for noise and stability. This paper presents a preliminary design of ultra-low noise bipolar current source over ±1A output range with a dual feedback path. The key circuit consists of three parts: high-precision operational amplifier, power amplifier, and current-voltage conversion instrumentation amplifier. The combination of a high-precision operational amplifier and power amplifier takes full advantage of the low noise advantages of precision operational amplifiers and the advantages of high drive capability of power amplifiers. Through the theoretical calculation of stability and the simulation of the total output noise, the parameters of the key components of the circuit are appropriately selected. The test results show that the broadband current noise and the standard deviation of our bipolar current source at 100mA output current is $10{\text{nA}}/\sqrt {{\text{Hz}}} $ and 22.89 ± 0.85μA (RMS, 0.1Hz-500kHz), respectively.