TURBULENT FLUCTUATIONS AND CONFINEMENT IN JET
High frequency fluctuations are observed in JET by edge magnetic probes and arrays of visible radiation detectors even in the absence of Mirnov activity (typical frequency sim1 kHz); cross-correlation techniques are applied in order to study the broad-band activity. Magnetic fluctuations (btheta) in the range 1-20 kHz are strongly correlated along a direction parallel to the edge magnetic field lines with a substantial fraction of them (30-60%) having low wave numbers (mleq, n sim1). Fluctuations in visible radiation coming from the edge are detected by soft X-ray diodes (without absorptive foil) up to sim100 kHz: correlation analysis indicates the presence of rather high m numbers (m sim10-100) with a correlation time tau"rm c" sim20 mus. This type of activity is also seen by the magnetic probes and a good correlation between the two diagnostics is observed. The edge magnetic r.m.s. level is continuously monitored with eight hardware filters over the 5-60 kHz frequency range. Database analysis of additionally heated discharges shows a proportionality between b"theta"rm N"" = bthetacdot B"rm T"/Btheta and the inverse energy confinement time (tau"rm E""-i").
Bibliographic Reference: REPORT JET-P(87)-26, 1987, AVAILABILITY: JET, ABINGDON, UK
Record Number: 1989126067700 / Last updated on: 1989-05-01
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