Effective Critical Electric Field for Runaway-Electron Generation

• In this Letter we investigate factors that influence the effective critical electric field for runaway-electrongeneration in plasmas. We present numerical solutions of the kinetic equation and discuss the implications forthe threshold electric field. We show that the effective electric field necessary for significant runaway-electronformation often is higher than previously calculated due to both (1) extremely strong dependence of primarygeneration on temperature, and (2) synchrotron radiation losses. We also address the effective critical field inthe context of a transition from runaway growth to decay. We find agreement with recent experiments, but showthat the observation of an elevated effective critical field can mainly be attributed to changes in the momentum-space distribution of runaways, and only to a lesser extent to a de facto change in the critical field.

Subject headings

NATURVETENSKAP  -- Fysik -- Fusion, plasma och rymdfysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Fusion, Plasma and Space Physics (hsv//eng)

Publication and Content Type

art (subject category)

ref (subject category)