Ultrahigh Densities and Volume Recombination inside the Separatrix of the Alcator C-Mod Tokamak

MARFEs are experimentally studied using spectroscopic techniques to determine their internal characteristics. We find the local density and temperature in the MARFE to be (2--3)×10²¹m^-3 and 0.7--1.0 eV, respectively. The volume recombination rate is also large in the MARFE, (5--10)×10²²s^-1, similar in magnitude to the plasma source rate in the core. Because this plasma sink is located in confined regions of the plasma, the MARFE acts like a limiter; ions ``recycle'' from the MARFE as neutrals. These characteristics have not been predicted by current models.