Mechanical performance characterization of the insulation strap of the ITER PF coil tail

Highlights: • Thermal contraction from 300 to 77 K of the tail strap of ITER PF coils was measured. • The elastic modulus of the strap was measured at 77 K. • Fatigue performance of the strap at 77 K was verified in the working condition. - Abstract: International Thermonuclear Experimental Reactor (ITER) is a full superconducting coil tokamak. The strap composed of fiber glass composite materials is an important component of Poloidal Field (PF) coil tail. The main function of the strap is to maintain the electrical isolation and mechanical connection between the last turn and the last but one turn. The thermal contraction of the strap shall be measured to assess the mismatch between the strap and adjacent conductor while the coil is cooled down, and further, in order to balance the thermal stresses, pretension on the strap is needed while the elastic modulus of the full-size strap shall also be measured. In addition, the fatigue performance of the strap shall be examined in consideration of the cyclic electromagnetic load on the tail in the tokamak operation condition. In this paper, the thermal contraction test, the elastic modulus test and the fatigue test on the full-size strap for ITER PF coils were carried out. The test results show that the thermal contraction from 300 K to 77 K is 0.19% and the elastic modules is about 60 GPa at 77 K. The fatigue results indicate that the strap can meet the requirement of ITER and can be utilized to the practical applications.