Stability test results on the aluminum stabilized superconductor for the helical coils of LHD

Stability tests have been carried out on short samples of the aluminum/copp er stabilized composite-type superconductors developed and used for the poo l-cooled helical coils of the Large Helical Device. The waveform of the lon gitudinal voltage initiated by resistive heaters shows a short-time rise be fore reaching a final value, which seems to correspond to the diffusion pro cess of transport current into the pure aluminum stabilizer. The propagatio n velocity has a finite value even for the transport current being lower th an the recovery current, and it differs depending on the direction with res pect to the transport current.