RUNAWAY TRANSPORT STUDIES IN THE TJ-I TOKAMAK

The runaway diffusion coefficient, D(r), for the TJ-I tokamak has been deduced using two different methods: in the first, D(r) is obtained u sing a steady state approach for values of the runaway confinement tim e tau(r) deduced from hard X ray (HXR) bremsstrahlung spectra; in the second, D(r) is deduced from sawtooth oscillations of HXR flux, and fr om the soft X ray intensity, recorded simultaneously. Data have been t aken in a scan with the toroidal magnetic field B(T). Averaged values obtained for D(r) = 5-10 m2.s-1, decreasing with B(T), are in both cas es consistent. Assuming that magnetic turbulence is responsible for th eir transport, from D(r) an averaged value of b/B(T), the magnetic flu ctuations level, can be deduced. The thermal conductivity coefficient chi(e), obtained using other diagnostics in TJ-I, is compared with D(r ). The results are in good agreement with those obtained in TJ-I using probes, spectroscopic methods, power balance analysis and a coupled a nalysis for temperature and density pulses.