SBIR-STTR Award

A novel high power millimeter/microwave source is proposed in which two interpenetrating streams of electrons, flowing through a backgroundplasma in a static magnetic field are used to generate a hot-electronplasma that is confined in a mirror-like magnetic field in the form of a folded-cusp magnetic configuration. Energy stored in the anisotropic, hot-electron plasma is then used to amplify unstable plasma waves to large amplitude by selective deactivation of mechanisms that stabilize the hot-electron plasma during the energy accumulation phase when the density of hot electrons is rapidly increased through the beam-plasma interactions. The phase i program will yield a design for an experimental device capable of verifying the key aspects of this novel source concept, as well as a theoretical framework for interpreting the empirical phase ii results produced by the experimental device and extrapolating those results to evaluate the suitability of the proposed source to meet the requirements of various high power microwave and millimeter wave defense and industrial applications.

Results achieved in Phase I of this project strongly support the feasibility of producing high-power pulses of microwave radiation from an inherently rugged and compact device in which one or more pairs of oppositely-directed, co-linear, steady-state energetic electron beams interacting with a background plasma are used to generate an anisotropic, high-beta, hot-electron plasma that is confined in a magnetic-mirror configuration. The hot-electron plasma efficiently stores a fraction of the electron-beam energy through preferential absorption of the electromagnetic wave generated by a three-wave process in which pairs of large amplitude electrostatic waves driven by the beam-plasma instabilities interact to create bursts of electromagnetic radiation at twice the upper hybrid frequency. The energy stored in the hot-electron plasma is converted into pulses of microwave radiation by amplification of whistler waves that can be launched from external sources for amplifier operation or generated spontaneously for oscillator operation. The Phase II program proposed here employs the existing amphed experimental facility at AMPC to demonstrate efficient hot-electron plasma storage of the energy of one pair of steadystate electron beams, and controlled transformation of a substantial fraction of that energy into pulses microwave radiation in a form suitable for effective handling. The critical properties of the hot-electron plasmas will be characterized experimentally and controlled for optimum performance with supplemental electron cyclotron heating as well as adiabatic magnetic compression.