Dual Highly Stable 150-kV Divider

A highly stable (± 1-ppm) 500-kV power supply is being developed for use in a high-resolution (~1-Å) electron microscope. One of the critical components in such a power supply is, of course, the feedback element, which, in this case, is a resistive voltage divider. A dual 150-kV divider has been constructed to determine the stability of such devices. The dividers are compared in a guarded Wheatstone bridge circuit and appear to be stable to within a few parts in 108 when operating at 150 kV. The high-voltage section of each divider consists of 150 1-M¿ resistors.