Velocity and magnetic field measurements of Taylor plumes in SSX under different boundary conditions

The SSX device has been modified by the addition of a $1~m$ long glass extension for accommodating pulsed theta pinch coils. The Taylor plumes$^*$ are launched from a magnetized plasma gun and flow to an expansion volume downstream. The time of flight (TOF) measurements of these plumes are carried out using a linear array of $\dot B$ probes (separated by $10~cm$). TOF of the plasma plumes from one probe location to the next is determined by direct comparison of the magnetic field structures as well as by carrying out a cross-correlation analysis. With the glass boundary, the typical velocity of the Taylor plumes is found to be $\approx 25~km/s$, accompanied by a fast plasma ($\ge 50~km/s$) at the leading edge. Magnetic field embedded in the Taylor plumes is measured in the expansion chamber using a three-dimensional array of $\dot B$ probes and is found to be $\approx 700~G$. Some flux conservation of the Taylor plumes is provided by using a resistive (soak time $\approx 3~\mu s$) and a mesh (soak time $\approx 170~\mu s >$ discharge time) liner around the glass tube for improving the downstream Taylor state velocity as well as the magnetic field. The results from these different boundary conditions will be presented. * Gray, et al, PRL {\bf 110}, 085002 (2013).