Development of a 30-kA cable-in-conduit conductor for pulsed poloidal coils

This paper describes designed parameters of a 30-kA cable-in-conduit conductor (JF-30), and the test results of stability margin measured by using a triplex in a conduit. Cross sectional size of JF-30 is 35mm × 35mm and 567 NbTi-Cu-CuNi strands are in a stainless steel conduit whose thickness is 2 mm. Void fraction is 33 % and the designed stability margin is 270 mJ/cc at 5 atm and 7 T. Stability test by a triplex showed a favorable margin, a few hundreds of mJ at 7 T even without helium flow. In addition, the stability was strongly increased when helium flow up to 0.2 g/s was applied. At around 3 atm, we found that the stability margin was mere than 2 J/cc which exceeded the present heater capacity. This resulted in an extension of current range, in which the sample is stable, up to 150 to 200 % when compared to the case without helium flow.