Conductor and joint testing for the BPX central solenoid

The central solenoids for the Burning Plasma Experiment (BPX) will experience a thermal and mechanical cyclic loading. A series of tensile, fatigue, crack growth, resistivity and joint component tests is currently underway on high-performance (HP) C17510 and on high-strength (HS) C17510 beryllium copper alloys. The fatigue tests were performed under strain control with various ratios of minimum to maximum strain. Compact tension specimens and full-width single edge notch specimens with cracks growing along the transverse and longitudinal orientation were tested. The current inner and outer joint concepts are also shown. The fatigue crack initiation results for the HS beryllium copper show that the central solenoid coils of BPX meet the design criteria (factor of two on stress at the design life and a factor of 20 on life at the design stress). The HS beryllium copper exhibited in orientation-dependent fatigue crack growth behavior, and the preliminary crack growth data for the HP beryllium copper show this same behavior. The crack growth data analysis of HS beryllium copper shows that PF1 meets a factor of three on life but not the factor of four in the design criteria for a largest undetected corner crack of 1 mm