Energy flux to the TEXTOR limiters during disruptions
Rapidly changing heat fluxes deposited on the limiter blades were observed during disruptions by infrared (IR) scanners. Several new features of the power flux to the plasma facing surfaces during a disruption were found. The disruptive heat flux occurs on three different time-scales. The fastest ones are for heat bursts with a duration of less than or equal to 0.1 ms; several of these bursts form a thermal quench of about one millisecond duration, and some of these thermal quenches may occur during the current decay phase. Power flux densities of the order of 50 MW/m2 were observed during a burst. The spatial extent of the area on which this power is deposited during a burst is larger than or equal to the size of half an ALT-II blade, i.e. about 1 m in the toroidal direction. Simultaneous measurements with two cameras showed that the correlation length of a single burst is smaller than half the toroidal circumference, probably of the order of half a blade or a full blade length. This is consistent with plasma islands of low mode number. The typical heat deposition patterns at the limiter blades for normal discharges are preserved during a disruption. The magnetic structure near the plasma surface therefore cannot be destroyed completely during the thermal quench. The power flux follows the field lines. However, the power e-folding length is about a factor of two to three times larger than under normal discharge conditions.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 32 (1992) No. 6, pp. 915-926
Record Number: 199211072 / Last updated on: 1994-11-29
Original language: en
Available languages: en