Investigation of the complex dynamics and regime control in Pierce diode with the delay feedback

In this paper the dynamics of Pierce diode with overcritical current under the influence of delay feedback is investigated. The system without feedback demonstrates complex behaviour including chaotic regimes. The possibility of oscillation regime control depending on the delay feedback parameter values is shown. Also the paper describes construction of a finite-dimensional model of electron beam behaviour, which is based on the Galerkin approximation by linear modes expansion. The dynamics of the model is close to the one given by the distributed model.Comment: 18 pages, 6 figures, published in Int. J. Electronics. 91, 1 (2004) 1-1

Remote Detection of Radioactive Material using High-Power Pulsed Electromagnetic Radiation

Remote detection of radioactive materials is impossible when the measurement location is far from the radioactive source such that the leakage of high-energy photons or electrons from the source cannot be measured. Current technologies are less effective in this respect because they only allow the detection at distances to which the high-energy photons or electrons can reach the detector. Here we demonstrate an experimental method for remote detection of radioactive materials by inducing plasma breakdown with the high-power pulsed electromagnetic waves. Measurements of the plasma formation time and its dispersion lead to enhanced detection sensitivity compared to the theoretically predicted one based only on the plasma on and off phenomena. We show that lower power of the incident electromagnetic wave is sufficient for plasma breakdown in atmospheric-pressure air and the elimination of the statistical distribution is possible in the presence of radioactive material.ope

EXPERIMENTAL-STUDY OF EFFICIENCY OPTIMIZATION IN A 3-CAVITY GYROKLYSTRON AMPLIFIER

An experimental study quantifying the effects of both penultimate cavity tuning and magnetic field profiling on the saturated efficiency of a three-cavity gyroklystron amplifier has been performed at a frequency of 4.5 GHz. As predicted by theory, it is observed that the penultimate cavity detuning in the gyroklystron is in the opposite direction from a conventional klystron for enhanced efficiency operation. This is a result of the opposite energy dependence of the bunching mechanism for the two interactions. Magnetic field profiling has also been shown to have a very strong effect on the amplifier efficiency, both through beam loading effects in detuning the penultimate cavity and through enhanced energy extraction in the output cavity. The measured efficiency of the gyroklystron is observed to improve from 5% to 21% by profiling the magnetic field along the device, and then from 21% to 29% by penultimate cavity detuning with an optimized magnetic field profile. Comparison with theory shows reasonable agreement.X118sciescopu

PHASE-STABILITY OF GYROKLYSTRON AMPLIFIER

Expressions are derived for RF phase stability in conventional klystrons and gyroklystrons. Phase noise is found to depend on electron energy in a completely different way for the two types of devices due to the inherent differences in gun dynamics and interaction mechanisms. In general, phase stability is better in gyroklystron operating at voltage less-than-or-equal-to 100 kV, while klystrons have somewhat better phase stability at higher operating voltage. An experimental study of phase stability in a four-cavity, 7.5-kV conventional klystron and in a three-cavity, 30-kV gyroklystron confirmed theoretical predictions. Phase sensitivity in the conventional klystron was 13-degrees per percent change in voltage, and in the gyroklystron was 4-degrees per percent change in voltage. The magnitude and frequency of the measured phase jitter was well correlated with the droop and ripple on the beam voltage. Phase sensitivity to other parameters such as input power, magnetic field strength, and input frequency were also studied experimentally.X1111sciescopu