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Abstract

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").

Additional information

Authors: MALACARNE M, JET JOINT UNDERTAKING, ABINGDON, UK;DUPERREX P A JET JOINT UNDERTAKING, ABINGDON, UK, JET JOINT UNDERTAKING, ABINGDON, UK
Bibliographic Reference: REPORT JET-P(87)-26, 1987, AVAILABILITY: JET, ABINGDON, UK
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