| The transport of runaway electrons is studied as a means of understanding the physical mechanisms responsible for anomalous electron heat transport. The confinement time of the runaway electrons is measured by a variety of experiments on the Princeton Large Torus (PLT) and the Poloidal Divertor Experiment (PDX). Measurements made in different energy ranges show the confinement time being 2-6 msecs between 0.4-1.0 MeV (10-30% of the thermal confinement time), and increasing to 50-100 msecs or greater between 8-22 MeV. The confinement time increases with bulk plasma density, and with toroidal field at low densities. Experiments include determination of the electron spectrum from the amount of photonuclear activation of a stainless steel limiter, and of the runaway electron scrape-off thickness measured from the angular distribution of that activation. The ratio of electrodisintegration to photo-neutron production, and the time dependence of those emissions, are related to transport coefficients. Thick target bremsstrahlung is measured between 1-8 MeV on PDX and 0.4-1.0 MeV on PLT, determining both equilibrium spectra and time dependence of the count rates. The measurements on PLT are made with a new 10 MHz counting rate pulse height system, which allows energy resolved measurements of time varying fluxes due to auxiliary heating and intense gas puffing, as well as observation of inverted hard X-ray sawteeth correlated with the minor internal sawtooth disruption. The dependence on plasma parameters of the time to peak of these hard X-ray events is measured and related to runaway electron confinement. Observations are made of fluctuations of the runaway electron flux to the limiter. Extending up to 100 kHz frequencies, the fluctuations are correlated with measurements of microwave scattering due to density fluctuations in the plasma, both in the shape of the frequency power spectrum and in the time dependence of the magnitude of the signals. Modulation of the runaway electron flux by in-out motions of the plasma is studied as a measure of transport coefficients. Several of the experiments are modeled by a 2-dimensional (energy and radius) runaway electron diffusion transport code, which includes both Flux Corrected Transport techniques to handle the steep energy gradients, and emission cross sections and detector responses to predict actual experimental observations. The measurements of the thesis, as well as results of previous experiments reviewed in the literature, are consistent with the existence of electromagnetic turbulence leading to a v(,(PARLL)) dependent scaling of the confinement time at low energies (< 1.0 MeV), and drift orbit averaging of the turbulence which increases the confinement at higher energies (> 1.0 MeV). |
