Explosively driven pulsed power sources seek to use the large energy density of high explosives to their advantage with respect to device size and volume. Generally, the energy density of high explosives is many orders of magnitude larger when compared to conventional systems that rely on capacitive, inductive, or mechanical energy storage. One such explosively driven power source is the magnetic flux compression generator that can produce a large current (up to a few 100 Mega ampere) on a microsecond time scale. All flux compression generator operation starts from a small seed magnetic field, and especially helical generators provide a potentially large amplification to very large magnetic field or current amplitudes. However, performance is limited due to various flux loss mechanisms that can lead to a severe loss in energy, so that sometimes only very little amplification is experimentally observed. At best, for a good design, the maximum achievable gain for a generator will be restricted due to limits imposed by the laws of physics. Fundamentals of high explosives, magnetic flux compression generator principles with an emphasis on the helical generator, as well as limiting physical mechanisms will be addressed in this seminar.