Large magnetic fields may be generated by compression of an initial ma
gnetic flux generated over a large area at relatively low magnetic fie
ld into a region of smaller area. Following a discussion of flux compr
ession principles, we discuss megagauss field systems in use at Los Al
amos where chemical explosives are used to compress the flux. Their us
e in some solid state experiments will be discussed briefly, including
a planned set of experiments on YBCO to be done jointly with a Russia
n team, whose aim is to determine the low temperature, critical magnet
ic field of YBCO.