Intense (several hundreds of kilowatts) subnanosecond coherent microwa
ve radiation - cyclotron superradiance of an electron swarm moving in
a uniform magnetic held - was recorded. The maximum power of the radia
tion was observed under group synchronization conditions, when the tra
nslational velocity of the swarm is equal to the group velocity of the
waves in the waveguide channel. (C) 1996 American Institute of Physic
s.