Abrupt reduction of core electron heat transport in response to edge cooling on the Large Helical Device

Abstract

Cold pulse inversion in a helical plasma is observed in the Large Helical Device (LHD) and thus the strong non-local effects are evident in the helical device as well as in tokamaks. A hydrogen pellet or tracer encapsulated solid pellet is injected into the edge of the LHD plasmas. A significant rise of the electron temperature is observed in the central region in response to the edge cooling. Transient analysis indicates a heat flux jump despite the absence of a change in the local temperature gradient. The non-local temperature rise takes place in the low density and high temperature regime just as predicted by the TFTR scaling.