An electromagnet coil comprising Litz wire windings and power leads without break or interruption is cooled by a perfluorinated liquid by sensible and phase change heat transfer in a closed system. The electromagnet coil may be housed in a pentagonal or hexagonal pressure vessel to allow high packing densities in an array or helmet configuration. The helmet is then lowered over a human cranium for transcranial electromagnetic stimulation. The Litz wire windings reduce the power and voltages required for operation, yet allow production of over 2 T of accurately directed magnetic pulses for direct nerve or neuron stimulation. The perfluorinated liquid maintains the temperature of the helmet to less than 35-40.degree. C., ensuring a comfortable temperature device for a human test subject. A utility cable connects the helmet to an external cooling unit and an external power supply.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Contract No. DE-AC52-06NA25396 awarded by the U.S. Department of Energy. The Government has certain rights in this invention.