Shield

The shield reduces the neutron flux reaching the vacuum vessel, TF coils and beyond. This minimises the radiological impact of the neutrons, and their heating of the TF coils which, if superconducting, need to remain at liquid helium temperatures. As with the blanket the energy deposited in the coolant may or may not be used to produce electricity, depending on the value of the switch iprimshld. The shield coolant fraction by volume is set via the input parameter vfshld.

The inboard and outboard shield thicknesses (shldith and shldoth, respectively) may be used as iteration variables.