High-Stability, Long-Duration Flat-Top Magnetic Field Generation Using a Novel Two-Stage Magnetic Compensation Circuit

Flat-top pulsed magnetic field (FTPMF) with high stability and long duration is imperative for scientific applications such as nuclear magnetic resonance (NMR) and specific heat measurement. This paper introduces a novel circuit design aimed at augmenting the stability and duration of the FTPMF using a multi-capacitor power supply. It is an invasive coil paired with a quasi-two-stage circuit for precision current regulation. The current control circuit ensures the invasive coil receives an ultra-low ripple current by MOSFET operating in the active region. The front stage is a MOSFET operating in the switching state to provide a voltage envelope for the second stage, thereby reducing the voltage drop and power loss of the second stage MOSFET. Furthermore, this paper proposes a design method for optimizing circuit parameters and system controls. Finally, to verify the validity of the theory, a 20T/110 ms/85ppm experimental prototype is developed. The experimental results show that the proposed topology reduce the device heat generation, and improves the flat-top duration as 4.7 times of the conventional scheme.