Tunable Electrically Small Conical Folded Dipole Antenna Used as a Mesoband High-Power Microwave Source
High-power microwave (HPM) moderate-band (MB) sources combine simple design concepts seen in ultrawideband (UWB) sources, but with longer pulses to produces higher energy spectral densities. These factors allow the designs to be more compact and less complicated than many narrowband HPM sources. In this letter, we will demonstrate from both simulation and experimental results the operation of a electrically small, tunable, self-resonant, mesoband source utilizing a conical folded dipole antenna as the energy storage and radiating element. The system is based on a previous design for an HPM folded helix antenna that has a resonant frequency of 46 MHz and is charged to 70 kV. The design presented here utilizes a tunable capacitance that allows the resonant frequency to be tuned between 52 and 87 MHz with ka =0.58 at the lowest resonant frequency.
A Scalable High-Power Microwave Source Based on Coherent Stimulated Emission
Future moderate-band (MB) high-power microwave sources will take advantage of having a small size and a low cost. However, the output power of existing designs is limited by the dc voltage supply. To tackle this issue, this article proposes a novel scalable high-power microwave source based on the concept of coherent stimulated emission. The proposed microwave source consists of an antenna array, in which the two arms of each dipole antenna are connected with a fast-rise time switch and charged by a dc voltage source. Each antenna unit is triggered by the incoming wave radiated from the previous unit and then oscillates and correspondingly produces a new electromagnetic wave to trigger the next one. Both simulations and experiments show that the output waves of multiple antenna units are in phase, and the output power is accordingly enhanced. Compared with the existing MB high-power microwave sources, the proposed microwave source is able to significantly boost the maximum output power by applying more automatically triggered antenna units, featuring strong scalability and less limitation by the dc voltage supply.
Impact of Nuclear Data Uncertainties on Transmutation of Actinides in Accelerator-Driven Assemblies
Abstract The potential impact of nuclear data uncertainties on a large number of performance parameters of reactor cores dedicated to the transmutation of radioactive wastes is discussed. An uncertainty analysis has been performed based on sensitivity theory, which underlines the cross sections, the energy range, and the isotopes that are responsible for the most significant uncertainties. To provide guidelines on priorities for new evaluations or validation experiments, required accuracies on specific nuclear data have been derived, accounting for target accuracies on major design parameters. The required accuracies (mostly in the energy region below 20 MeV), in particular for minor actinide data, are of the same order of magnitude of the achieved accuracies on major actinides. Specific requirements also concern the improvement of minor actinide data related to decay heat and effective delayed-neutron fraction assessment.