A heavy ion beam probe for the Madison Symmetric Torus

A heavy ion beam probe (HIBP) is being developed for application on the Madison Symmetric Torus (MST). It will be used to make measurements of the plasma space potential Phi(r), fluctuations in potential <(Phi)over tilde>(r), the electron density n(e)(r), fluctuating electron density (n) over tilde(e)(r), and radial electric field E-r(r) from the core to the edge region of the plasma in MST. While information on these quantities can and has been obtained with probes inserted in the surface region, none of the above measurements have been made in the core of a hot reversed field pinch. Measurements of Phi(r), E-r(r), and n(e)(r) have been well established in previous HIBP systems on tokamaks such as Impurities Studies Experiment, Texas Experimental Tokamak (TEXT), and TEXT Upgrade, stellarators such as Advanced Toroidal Facility and Compact Helical System and Bumpy Tori such as Elmo Bumpy Torus and Nagoya Bumpy Torus. Less well developed in terms of HIBP measurements are equilibrium and fluctuating magnetic fields. Because the confining field on MST is determined by plasma conditions, some effort has been made in the design of the MST beam probe to make it possible to characterize B before, during, and after the plasma discharge. (C) 1999 American Institute of Physics. [S0034-6748(99)75901-0].