Limits on the field of ohmic heating solenoids, applied to a Tokamak TNS
Abstract
If the ohmic heating solenoid for the TNS or other large Tokamak is an ungraded cryostable superconducting solenoid, with NbTi at 4.2 K as the superconductor, then the smallest outer diameter is not achieved at the highest attainable field. There is a lower optimum field which minimizes the outer diameter for a given voltsecond requirement. At higher fields the mean diameter decreases; but the high fields require more superconductor, more copper stabilizer, more stainless steel for support, and more liquid helium coolant. For the GAANL design for TNS, the optimum field is 7.55 T and the minimum outside diameter for the solenoid is 2.15 m. If, on the other hand, the solenoid is graded, with more NbTi, copper, and stainless steel on the inner turns where the field is higher, then the voltseconds can always be increased, for a given outer diameter, by adding more turns at a higher field inside until either the critical field is reached or the solenoid bore is filled.
 Publication:

Presented at 7th Symp. on Fusion Res. Proj
 Pub Date:
 1977
 Bibcode:
 1977frp..symp...25T
 Keywords:

 Field Strength;
 Ohmic Dissipation;
 Resistance Heating;
 Solenoids;
 Tokamak Devices;
 Computer Programs;
 Eddy Currents;
 Superconductors;
 Toroidal Plasmas;
 SolidState Physics