Stabilization of magnet current using Voltage standards

A stable high current source is frequently used for various magnetic metrology applications such as magnetic field generation for /spl gamma/'/sub p/, measurement and for testing various magnetic sensors. As a current stabilization method, a feedback scheme based on a voltage reference was previously suggested. We tested the feedback method for 1 A solenoid current using Zener voltage standard, and attained stability of 2/spl times/10/sup -8/. Comparing the result with previous one using programmable Josephson voltage standard, we found the limitation of the attained stability is mainly from the feedback scheme, not from the stability of voltage reference. The 1 A is magnitude of the SI ampere (A), and current at which the /spl gamma//sub p/' measurement is carried out.