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We have made experiments of explosive-driven flux compression generators for large current production. When an initial current is small (6.9 kA), the maximum output current reached up to 3.2 MA and a current profile agreed well with a result of numerical simulation. It is, however, found that there exists a tendency of decreasing an amplification factor as increasing the initial current from 22 to 56 kA. As a result, the maximum current was not able to exceed a limit value, about 5 MA, independent of the initial current.
To reduce the current density, an end part of the generator was modified; a diameter of an inductive load was enlarged and an armature and a stator were changed into cone shapes to be connected with the load. This generator produced the maximum current of 8.0 MA when the initial current was 52 kA. An estimation of a surface temperature rise of a copper conductor which is caused by Joule's dissipation of a pulsed current was done taking into consideration the magnetic diffusion and the thermal conduction. The result shows that the temperature of the copper surface reaches its melting point when the surface current density is 41 MA/m. This corresponds to the total armature current of 4.9 MA.