Improved energy confinement in spheromaks with reduced field errors

An increase in the global energy confinement time (${\mathrm{\tau }}_{\mathit{E}}$) was obtained in the CTX spheromak by replacing the high-field-error mesh-wall flux conserver with a low-field-error solid-wall flux conserver. The maximum ${\mathrm{\tau }}_{\mathit{E}}$ is now 0.18 ms, an order of magnitude greater than previously reported values of ≲0.017 ms. Both ${\mathrm{\tau }}_{\mathit{E}}$ and the magnetic energy decay time (${\mathrm{\tau }}_{\mathit{W}}$) now increase with central electron temperature, which was not previously observed. These new results are consistent with a previously proposed energy-loss mechanism associated with high edge helicity dissipation.