Location and characterization of electrical leakage paths and turn to turn shorts in TFTR toroidal field coils

The authors describe the methods used at PPPL (Princeton Plasma Physics Laboratory) to: (1) locate and characterize multiple electrical leakage paths in the insulation of the TFTR (Tokamak Fusion Test Reactor) toroidal field (TF) coils; and (2) determine if turn to turn shorts exist in the coils. The electrical leakage test was first used in May of 1991 to locate a single leakage path of 15 MΩ in TF coil No. 3. The test was again used to locate a single leakage path of 1 MΩ in TF coil No. 18 on September 3, 1991. In theory, leakages as high as 75 MΩ can be located and characterized using this method. The turn to turn test consists of individual tests on each TF coil and a signature test to determine if changes have taken place since the last test. The turn to turn portion of the test was performed on the TFTR TF coils in April of 1991. The signature test was performed in July of 1991. Tests have shown that turn to turn shorts as high as 40 mΩ (500 times the 80 μΩ resistance of a single turn) can be located using this method. The hardware designed and built to support both tests and the test results are also described