In SCGs with high response excitation, superconducting
wire for pulse is used. In this case, quick change of field current is essential, then, magnetic shield is of no
use. In case of cold damper, the material for the shield
has high electric conductivity. In case of high response
excitation, high electric conductivity is of no use, then
material of low conductivity which is cooled directly by
gaseous helium (heat exchanger is not used) is used.