  We have searched for microsecond-timescale broadband emission from a sample
of eighteen millisecond pulsars. Our study places strong limits on such
emission from several millisecond pulsars and shows that it is only present in
a small subset of millisecond pulsars. Giant pulses of up to 64 times the mean
pulse energy were detected from PSR J1823-3021A in the globular cluster NGC
6624. In contrast to the giant pulses of PSR B1937+21, nearly all of the giant
pulses from PSR J1823-3021A were distributed within the trailing half of the
main-pulse component of the integrated pulse profile. The fact that no giant
pulses were observed on the leading side of the main-pulse component suggests
that giant pulses are preferentially emitted closer to the last open field line
than ordinary emission. The correlation between giant pulse emissivity and
spin-down luminosity in millisecond pulsars suggests that the high period
derivative of PSR J1823-3021A is intrinsic and is not just an artifact of its
acceleration in the gravitational potential of NGC 6624.
