  An ultra-high magnetic field was generated by the electro-magnetic flux
compression technique under a reduced seed magnetic field condition and
achieved maximum magnetic field intensity was investigated. An ordinal pickup
coil measurement fails due to the dielectric breakdown at around 500 T. On the
other hand, by utilizing the magneto-optical Faraday rotation method with a
small probe, the measureable maximum magnetic field increased significantly. It
was found that reduced seed field increases the maximum magnetic field, but
with a reduced size of the final bore. A highest magnetic field over 763 T and
possibly up to 985 T approaching 1000 T was detected.
