N. Bretz et al., DENSITY-FLUCTUATIONS ASSOCIATED WITH LIMITER H-MODES ON TFTR, Plasma physics and controlled fusion, 36(7), 1994, pp. 10000141-10000146
Edge density fluctuations have been observed with microwave scattering
in limiter H-mode plasmas on TFTR. The primary feature of these fluct
uations is a strong average frequency shift in the electron diamagneti
c drift direction corresponding to poloidal velocities of 1-3x10(6) cm
/s and an inward radial electric field of 60 kV/m. The rotation begins
to increase at the Halpha drop and rises to a steady state in 5 to 50
ms. well before ELMs begin. ELMS modulate the rotation feature, elimi
nating it for the duration of the ELM. After the ELM, the rotation fea
ture resumes its pre-ELM value in about 0.1 ms. Short duration (0.01 m
s) precursor bursts propagating in the ion diamagnetic direction are o
bserved to precede the ELM event by approximately 0.5 ms.