Measured currents in JET limiters during disruptions

Structures mounted inside a tokamakmust be able to withstand the electromagnetic forces which arise during disruptions of the plasma. This paper reports on halocurrent measurements in the JET tokamakduring disruptions. A toroidallydistributed array of current sensing tiles reveal that in many disruptions a high degree of toroidaluniformity exists. However in exceptional disruptions the halocurrent measured at different toroidalpositions varies by more than a factor of 2. This latter class of disruption has been observed to result in an asymmetric displacement of the vacuum vessel. The total halocurrent is estimated to be up to 15% of the initial plasma current. The halocurrent width for a particular disruption is estimated to be 8 cm.