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1 - Nuclear Sciences and Applications - IAEA

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<strong>IAEA</strong>-CN-50/A-VI-3-1 357<br />

10 12<br />

No. chord<br />

FIG. 4. Measured line integrated emissivity distributions using different Al absorber foils for stable<br />

tokamak discharge. The curves are normalized to the peak values. The tokamak centre lies between<br />

chords 6 <strong>and</strong> 7; chords I <strong>and</strong> 12 are displaced 5 cm from the centre.<br />

t[ms)<br />

ttms]<br />

FIG. 5. Measured soft X-ray signals for silicon <strong>and</strong> MCP detectors of a tokamak discharge with<br />

periodic disruptions.<br />

thinner absorber foils but can be observed even for 3 (im foil. The silicon detector<br />

soft X-ray measurements showed these flashes only in some special cases with small<br />

amplitude. For 0 <strong>and</strong> 0.7 jtm foils, the signals much more resemble the bolometric<br />

total radiation signals than the silicon detector signals. This shows that a significant<br />

part of the total radiated power comes in the low energy range during disruptions.<br />

This is illustrated in Fig. 5.<br />

The time resolution of the MCP soft X-ray diagnostics has been estimated on<br />

the basis of the measured photon statistics. In the given geometry, this turned out<br />

to be a few ps. Placing the MCP detector closer to the plasma time resolution of 1 (is<br />

could be obtained. During the first experiments, 25-30 kHz disruption precursor<br />

oscillations were measured.

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