Moving double layers

Using a triple-plasma device, moving double layers have been produced by abruptly increasing the plasma density in the region of the double layers. Propagation velocities up to 3.5 c_s have been achieved with their velocity scaling as $\text{ν ～ (2e ×}\text{δ?}\text{T}{}_{\mathrm{<mtext>e</mtext>}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{c}{}_{\mathrm{<mtext>S</mtext>}}$.