Progress with small, high-magnetic-field spheromaks in CTX

Summary form only given. The current CTX program is directed towards using spheromaks as an energy transfer medium to accelerate metal plates to hypervelocity. Success requires high-quality (i.e. clean and long-lived) spheromaks with very high initial magnetic field strength; ultimately, field, high as 10 T may be desired. To facilitate the production of small, high-field spheromaks, the following changes to CTX have been made: (a) a new solid-wall flux conserver with a radius of 0.28 m (roughly half the previously used 0.61-m radius) has been installed and (b) the external capacitor bank circuit has been changed to give shorter (≈0.18-ms), higher-power pulses to the pulses to the plasma gun. The highest maximum internal field obtained to date is ≈3.5 T, but the majority of the data obtained thus far are from spheromaks with ≈2.2-2.6-T maximum internal field. The longest total spheromak lifetime has exceeded 1 ms for these conditions. Several interesting types of spheromak behavior observed in this flux conserver are described