This award aims to improve the pulse length of pulsed thermionic electron sources by an order of magnitude. The improved sources will allow more intense interrogation of targets by MeV gamma rays. The project addresses a key issue of electron sources.
This project will combine efforts related to optics, accelerator physics, materials and surface science, and the use of the relevant advanced instrumentation needed by the scientists and engineers. Education of students, including high school students, and their introduction into the nuclear science and engineering career opportunities is an integral part of this project
The research conducted under this grant has as its objective the stabilization of the surface temperature of the thermionic cathodes used as the source of the electron beams for critical applications in laser operation, high energy physics, etc. The temperature of the emitting surfaces of the thermionic cathodes used in these systems typically increases with time leading to the uncontrolled growth of the emitted current. This growth in current has restricted the application of these otherwise high performance and cost effective cathodes to devices that can be operated on a pulsed basis for short time intervals over which the growth in current is small. In this research, we carefully measured the temporal and spatial variations in the cathode surface temperature during one of these pulses to assess the feasibility of the means available to stabilize cathode surface temperature. In the next phase of the project, we will pre-heat the cathode surface using a short laser pulse to reach operating temperature at the start of the pulse, and relying on the heat input normally experienced during the pulse to maintain the surface at a constant temperature. The detailed measurements of cathode surface temperature performed during this research are consistent with the requirements for implementation of this approach. Tests of the proposed surface temperature stabilization technique will be undertaken in the next phase of the research.
