Study on the Shimming Power Supply at room temperature for superconducting magnet

The homogeneity of superconducting magnetic field is one of the important factors determining the spectral resolution and signal-to-noise ratio of NMR spectroscopy. The active shimming is a real-time tuning for a homogeneous magnetic field. In this paper the principle of the active shimming and its process as well as the basic model of room-temperature Shimming Power Supply were investigated. A FPGA-controlled Shimming Power Supply system with Ethernet-based communications was designed. The utilization of Ethernet technique increases the controlling speed of a host computer and the data transfer speed. The FPGA module ensures the precise control and data distribution. The multi-bit DAC insures the high precision and high resolution of currents output. The use of the current-series feedback technique provides a high stability for the output current. The Shimming Power Supply system has features of simple structure, quick response, high integration, high precision, high resolution and independency. It may find wide application in real-time shimming of superconducting magnet.