Proto S-1A

Proto S-1A (sometimes known as Proto S-1A/B) was a prototype of S-1 built at PPPL in 1980. Its parts were a scaled down version of the S-1 device, 1/6 of the size of the main device. It was made to demonstrate the viability of the spheromak concept. Proto S-1A had a 15cm major radius and 3cm minor radius flux core which contained a 3-turn poloidal flux coil and a 40-turn toroidal flux coil. The core was covered with a 3mm thick stainless steel enclosure that functioned as a vacuum vessel and helped to symmetrize the induced fields. Discharges were made using hydrogen, helium and argon with pressures around 20 to 50 mTorr. Proto S1-A was able to maintain its fully formed configuration for 12 μs. After Proto S-1A, another prototype was built: Proto S-1C