Electromagnetic Pulse Duration Research Articles

Temporal and Spectral Characterization of Electromagnetic Pulse Emitted From Nanosecond Pulsed Laser Produced Aluminum Plasma

The electromagnetic pulse (EMP) emitted from the plasma produced by interaction of 5-ns pulsed Nd:YAG ( $\lambda =532$ nm) laser with the aluminum target was measured. The laser irradiance at the target was varied in the range of $3.12\times 10^{9} - 4.56\times 10^{10}$ W/cm2 and its influence on the temporal and spectral parameters of the EMP was investigated. The EMP starts well after the termination of laser pulse and the duration of EMP is up to several hundred nanoseconds. The EMP start time was found to decrease from approximately 150 to 60 ns with the rise of laser irradiance. The rise time of EMP (~50 ns) does not seem to vary with the laser irradiance. The signal consists of several resonance peaks in the frequency bin of 20–200 MHz, whose intensity also depends on the laser irradiance. The observed dependence of EMP intensity on the laser irradiance and frequency of fundamental-mode emission is compared with the theoretical predictions. The considerable delayed emission of EMP indicates that its origin can be related to the macroscopic charge separation phenomena during the plasma expansion.

Resonant electron-positron pair photoproduction on a nucleus in a pulsed light field

The resonant photoproduction of an electron-positron pair on a nucleus in the field of a pulsed light wave is studied theoretically. The approximation where the electromagnetic pulse duration is much longer than the characteristic time of wave oscillations is considered. The interaction of the electron and positron with the Coulomb potential of the nucleus is considered in the Born approximation. An analytical expression for the resonant differential cross section is derived for the range of moderately strong external fields. This cross section contains a resonant peak whose height and width are determined by the external pulsed wave characteristics. The resonant cross section for pair photoproduction on a nucleus in a pulsed laser field can exceed the corresponding cross section for pair photoproduction on a nucleus in the absence of an external field by an order of magnitude.

Generation of ultrashort pulse based ом the superradiance of isolated electron bunch

The radiation of spatially—localised electron ensembles with the infinite lifetime of particles is considered as the classical analogy of superradiation effect. The results of theoretical and experimental investigation are presented for different kinds of superradiance: cyclotron, cherenkov, undulator. First the microwave superradiation effect pulses of indicated types were registrated. The electromagnetic pulse duration were between 300-800 ps. The maximum power level about several megawatts was achieved under cherenkov radiation in dielectric waveguide, while the maximum stability and reproducibility of radiated pulses were observed when the electron bunch passed through the corrugated waveguide.