THE JET SOFT X-RAY DIODE ARRAY DIAGNOSTIC
The arrays of silicon diodes recently installed on JET measure the plasma soft X-ray emission with high temporal and spatial resolution, allowing mhd effects to be investigated. The diagnostic consists of two "pinhole" cameras which view the same toroidal cross-section in orthogonal directions. A data acquisition system based upon three cascaded digital filters can convert the 200 KHz detector signal ADC output to lower sampling rates of 10, 1 and 0.1 KHz. Initially, studies have concentrated on the sawtooth collapse. By means of a trigger system data on the sawtooth crash have regularly been recorded at a sampling frequency of 200 KHz. Using tomographic reconstruction techniques, the soft X-ray emissivity cross-section during the crash has been reconstructed. First results during ICRF heating show no precursor activity prior to the sawtooth collapse, whilst during the crash the hot central plasma is displaced off axis by about 30 cms on a timescale of 50-200 musec, after which a hollow soft X-ray profile forms.
Bibliographic Reference: WRITE TO THE PUBLICATIONS OFFICER, JET JOINT UNDERTAKING, ABINGDON, OXON, OX14 3EA (UK), MENTIONING REPORT JET-P(86)16, 1986
Record Number: 1989125014000 / Last updated on: 1987-02-01
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