Device for normal phase detection in a toroidal-field superconducting coil of the ''Tokamak-15'' device

Specifications are formulated and a structural diagram is described of the normal phase detection device (NPDD) developed for the Tokamak-15 protection system. Besides the protection functions in the NPDD of the T-15 tokamak device, the possibility of cut-off or decrease in the feeding current in the toroidal field superconducting coil (TFSC) specified, if the normal phase (NP) propagates slowly along the coil or exists in the limited ranges. The NPDD is based on determining the voltage across the ohmic resistance of the TFSC sections converted to the normal state. In that case the protection system performs two functions. The first one is to detect the NP at a high NPDD sensitivity, while attempting to restore the superconductivity by changing the TFSC current regime. The second function to exercise a protective power lead out from the TFSC when the current changed has not lead to a NP ''collapse '' and reached the level permissible by heating. The NPDD of the T-15 device provides detection of a NP signal in the protective extraction mode at the 100-500 mV level, in the control mode - at 2-50 mV at +-0.5 V noise voltage. The detection time is chosen within the 0.01-0.5 s range depending on the noise duration; high voltage decoupling is up to 3 kV. The availability of a back-up channel and an emergency protection channel with a follow-up control of the state of the main NPDD units and appropriate alarm system ensures a hiah system reliability