Field generation and sustainment and their effects on energy transport in SSPX

In SSPX, coaxial gun helicity and current injection generate a spheromak, amplifying applied poloidal magnetic flux and driving toroidal current, balancing plasma helicity changes and ohmic losses. The spatial distribution of losses depends on helicity and current transport and flux geometry, helicity transport, electron temperatures, and the self-consistent distribution of current and field. Critical is the degree of flux surface closure; current drive on perfectly closed surfaces requires a changing surface poloidal flux. Data and current drive models, including hyper-resistivity and NIMROD, describe dominant processes in SSPX. The extent and nature of flux surface closure impact electron energy confinement; electron temperature profiles thus provide clues about closure and the physics of thermal conductivity.