Critical to all Exploding Foil Initiator or "slapper" systems is
the bridge-barrel--flyer combination, which needs to be optimized for
each application and fire set. The best way to do this is with
optical diagnostics. Parameters desired are the flyer position,
shape, and velocity versus time as a function of charge voltage and
discharge current. Multifraine microphotography of a flyer moving down
a barrel is one solution but poses several problems, one of which is
the insufficient depth of field of the optics system. If most of the
length of the "infinite" diameter barrel is removed and the flyer is
viewed from the side, then its axis of movement will remain in focus,
displacement versus time will be recorded, and its shape inferred.
Bridge burst may also be photographed to guarantee against shorting
and attain maximum performance.
The flyer event takes place in about 80 nsec. , necessitating a
100 million frame per second camera for 8 frames. Kerr cell cameras
are seldom used but provide superior spatial resolution to electronic
image convertors, are more rugged and much less expensive. Laser
microphotography is more conmion. After a review of the principles of
Kerr cells, two multiframe Kerr cell cameras will be described. Using
a nitrogen laser pumped dye system as backlight, the Kerr cameras may
photograph nonluminescent objects. Minus the Kerr cells the multifranie
optics and laser may be used in a Cranz - Schardin mode.