We report on further studies of current drive in the SPHEX spheromak devicewhen operated as a spherical tokamak. Previous work has demonstrated that thecurrent amplification factor, defined as the ratio of the toroidal plasmacurrent to the driving gun current, increased linearly with the appliedtoroidal field. Results are presented from a more detailed analysis of thisscaling for a fixed gun current of 60 kA, utilizing direct internalmeasurements of current density and equilibrium modelling of internal magneticfields. The data indicate that the increase in the current amplificationfactor is largely the result of changes in the wavelength of the helicaldistortion of the open flux (identified with the global n = 1 mode) connectedto the helicity injector: the increase in toroidal current on closed fluxsurfaces is much more modest. We discuss changes in current profiles atdiffering applied toroidal fields and demonstrate the operating regime overwhich helicity-injected current drive is effective in SPHEX. The implicationsof this work for proposed helicity injection schemes in the next generation ofspherical tokamaks are discussed.