Langmuir probes for plasma plume diagnostics

Summary form only given. Langmuir probes are highly versatile plasma diagnostic tools. Triple Langmuir probes (TLP) can be used to measure electron the temperature (T_e) and density (n_e) with time resolution. This ability gives a unique opportunity to observe the time evolution of discontinuities formed at the interaction of a plasma flow with a static background plasma. Adding a fourth probe, perpendicular to the flow direction, creates a quadruple Langmuir probe (QLP) which enables the measurement of plasma velocities. Being able to compare the fluid motion velocity with the propagation speed of perturbations will help identify the discontinuities observed, for example to distinguish between a shock in the ambient plasma from the arrival of the ablation plasma front. Results from TLP measurements and progress on QLP development will be presented.