3. Characteristics of the coils

As described in section 2, the specifications for the LCT test coils were chosen to ensure that all coils were (1) compatible with the intended six-coil test array and (2) readily adaptable to meet the envisioned demands of TF coils in a tokamak fusion reactor. To encourage exploration of the various design options, the specifications intentionally allowed each design team as much freedom of choice as possible consistent with the foregoing considerations. As it turned out, the principal options were indeed represented among the six coils.All design teams accepted the judgment that the requirement of 8.0 T at the winding could be achieved by using a NbTi superconductor cooled with helium at 3.8–4.2 K. Not surprisingly, each team chose to use this material rather than the potentially more capable but definitely more difficult Nb3Sn. However, in its proposal to DOE, the WH/Airco team had stressed that either material could be used in its cable-in-conduit type conductor. To explore the problems of Nb3Sn conductor and winding, DOE therefore directed the WH/Airco team to use this material and to proceed with the necessary additional development required for commercial production.With regard to the mode of helium cooling, the teams were evenly divided, with three choosing PB cooling and three choosing forced flow. These and other design choices are evident in the coil features listed in table 3.1.