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Plasma-produced electrons have been trapped for long periods of time in orbits around a positively charged wire. Since the frequency of rotation of each electron increases if it loses kinetic energy and sinks into the positive-potential well, phase bunching resulting in intense microwave emission can be easily excited.PACS 52.25.Ps, 52.35.Fp, 52.55.Mg The basic advantages of this electrostatic microwave emitter over magnetically confined electron devices is that theoretically by use of readily available voltages and wire sizes, it can operate at free-space wavelengths down to at least 0.1 mm. However, limits in available magnetic field strength restrict conventional magnetic-field devices to wavelengths above 1.0 mm. In addition, since the orbit frequency is a function of electron energy, relativistic electrons are not required for operation.The basic concept of trapping plasma-produced electrons in orbit around a wire is not new. The first publication which appeared on the subject was by McClure 1 in 1963. Other papers concerned the trapping of electrons around grid wires in Evapor-Ion vacuum pumps, 2 and the Orbitron ion gauges. 3 ' 4 Based on this earlier work, we propose the name "Orbitron" microwave source 5 for our device. The basic idea that the device could be used as a high-frequency maser grew out of plasma-wave and maser studies in our laboratory, and a previous device in which an electric field was used to distort electron orbits in a magnetically confined electron cloud was successfully operated. 6 The basic principle of operation of any maser is that electrons oscillate in a system in which the electrons both are confined for a long time and in which the electron frequency varies with energy. Electrons interacting with the noise field in a microwave cavity gain or lose energy, experience a frequency shift, drift in phase, and after some latent period, "phase bunch" and release a coherent burst of radiation. In a conventional atomic maser, the frequency variation with energy is apparent from the differently spaced quantum levels. In a free-electron maser using electrons trapped in a uniform magnetic field, the frequency is independent of energy, and maser action cannot occur. However, maser action can occur if the electrons are made relativistic, so that the relativistic change of mass with energy produces a frequency shift with changing electron energy. 7 In our maser, electrons are trapped radially by a balance between the electric field and centrifugal force. Axially, the electrons are trapped by a carefully designed fringing field. 1 This good trapping produces a mean free path of many meters, and results in our obtaining a sufficiently long "latent period" to permit phase bunching to occur. Previous work with electrons orbiting electrostatically used a quite different physical arrangement: an electron gun, an electron collector, and a singlepass electron beam. 8 Our mathematical model is that of a group of electrons, produced from a glow discharge, each in a circular orbit with an initial an...

Large volume, atmospheric pressure, low-temperature plasmas have been shown to be effective biological and chemical decontamination devices [1]- [3].However, most of the discharges use RF power sources capable of generating high voltages at relatively high kequencies. Such sources are not only expensive, but they radiate power which can potentially affect sensitive electronics located in their surroundings. In order to solve these cost and technical drawbacks, Alexeff, Laroussi, and co-workers [4] introduced the Resistive Barrier Discharge (RBD) which uses either DC or quasi-DC (60 Hz) sources. With an input power less than 1 kW, and helium as a carrier gas, the RBD is capable ofgenerating a few liters of low-temperature plasma, at atmospheric pressure.Recent work by Laroussi, Dobbs, and co-workers has demonstrated that the plasma generated by the RBD decreases viability (estimated by cultural techniques) of bacteria. In this paper, in addition to reporting on the germicidal potential of the

The Orbitron MASER is a device which can be used to produce millimeter and submillimeter radiation. Frequencies up to 1 THz have been observed. It can be operated in a pulsed mode or in a steady state mode, using a hot cathode.In recent experiments we have used the entire outer wall of the device as a hot cathode. We have also been using the device as a fast opening switch.