Development of Unconventional Edge and Scrape-off Layer Measurements Using Compact Diagnostic Neutral and Ion Beams*

We are developing diagnostic beam techniques to enable equilibrium and fluctuation measurements of density (n_e) and magnetic field (B) in edge and scrape-off layers of magnetically confined plasmas. Simultaneous, localized measurements of these parameters will provide unique insight into edge localized modes, current density, turbulence, and transport. A beam of neutral or singly ionized particles is injected into the plasma and undergoes ionization due to electron impact and charge exchange collisions. Analysis of the resultant charged particles yields information about B and n_e at the ionization location within the plasma. The diagnostic is similar to a heavy ion beam probe but has notable differences: the detector is located within the magnetic field of the confinement device, beam energy (and accelerator voltage) requirements are lower, and the system footprint is smaller. We will discuss two areas of innovation: (1) development of a detector and technique that could lead to determination of the magnetic vector potential in the plasma, and (2) simulations of 10-100 keV neutral alkali beams that could be used to probe the edge, scrape-off layer, and regions near the divertor X-point of a large tokamak.