Influence of Indentation on the Critical Current of Nb3Sn Strands

AbstractThe Japan Atomic Energy Agency (JAEA) is procuring Central Solenoid (CS) conductorsfor all modules forITER. The superconducting properties of the Nb3Sn CS conductors will have to sustain 60,000 electromagnetic (EM) cycles. The current sharing temperatures (Tcs) were stable with EM cycles in short twist pitch conductors.However, the short twist pitch and tight cabling increases indented strands at the contact point between strands before heat treatment. The results of Ic measurement on artificially indented Nb3Sn strands indicate that Ic was almost constant within a critical depth of the indentations

Influence of Sulfur Content on Penetration Depth in TIG Welding for High Manganese Stainless Steels

TIG welding of high manganese stainless steels was conducted with different sulfur contents of 5 and 20 ppm. The penetration depth of the welding bead clearly increased even when the sulfur content of the sample was only very slightly increased from 5 to 20 ppm. In situ observation of the surface of the molten pool revealed that the increase in penetration depth of the welding bead could be attributed to an elevation of the average temperature at the center of the molten pool from 2070 to 2200 K due to the generation of an inward fluid flow in the pool. The results of precise measurements of the surface tension of molten high manganese stainless steels using the electromagnetic levitation (EML) technique, thoroughly explained that the inward flow in the molten pool of the sample containing a sulfur content of 20 ppm was induced by Marangoni convection driven by the boomerang shape temperature dependence of the surface tension of the molten sample. The experimental results of the variations in the temperature distribution and the fluid flow direction in the molten pool depending on the sulfur content were reproduced well by a numerical calculation considering the four dominant driving forces of plasma jet, buoyancy, electromagnetic forces, and Marangoni convection, which indicated that the fluid flow direction was dominantly controlled by Marangoni convection

Minimum Quench Energy Evaluation of ITER Toroidal Field Conductor Using an Inductive

To keep a stable operation of the ITER Toroidal Field (TF) coil without quenching, it is necessary to know the threshold of allowable external heating energy, which is called minimum quench energy (MQE), of the TF conductor during the operation in ITER. To evaluate the MQE, a series of conductor heating tests has been performed during the TF Insert (TFI) test campaign. TFI is a single layer about 9-turn solenoid wound from ITER TF conductor. The coil diameter is 1.44 m and the conductor length is around 40 m. TFI is force-cooled by supercritical helium inside the TF conductor. For the TFI, 68 kA current had been applied under 10.8 T background field as rated operation condition. During its operation, the conductor was inductively heated by an inductive heating coil. Through the test, MQE of the TFI has been obtained