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Energy loss from high-energy electrons that pass through a transmission window causes an increase in window temperature. A technique to cool transmission windows that utilizes water under high pressure flowing in capillary ducts is presented. A model for fluid flow in ducts quantifies fluid pressure, water temperature, convective rate, and vapor pressure as a function of distance into a capillary duct subject to uniform heating.The results quantify a design to prevent vapor formation in a capillary duct and provide a limit on net power dissipation. An example quantifies the design of a 5-cm-diameter window that would support 30 mA/cmz continuously at a beam energy of 500 keV.We have received a Phase 1 SBIR contract from the U. S. Navy to develop a plasma stealth antenna. The concept is to use plasma discharge tubes as antenna elements. When the tubes are energized, they become conductors and can transmit and receive radio signals. When they are de-energized, they revert to nonconducting elements (in present tests, glass tubes), and do not reflect probing radio signals. The reflection problem is most acute for probing signals near the resonant frequency of the antenna, which produces a large reflection cross section. A second feature of the plasma antenna, is that it can be reconfigured during operation, by selectively energizing only some of the elements. It can therefore be "steered" electronically. This cannot be done with metal conductor antennas. A third feature of the plasma antenna, is that it can be turned off rapidly, reducing ringing on . pulse transmission.Preliminary tests before receiving the SBIR successfully demonstrated both the operation of the antenna in transmission and reception, and the stealth features on a Navy test range in San Diego. The tubes used in that demonstration were modified neon sign discharge tubes filled with helium, neon, argon, and a neon-argon mixture. More detailed experiments are under way to explore such topics as optimizing the system with respect to antenna-feeder coupling, radiation-pattern peaking, and signal-to-noise ratio.The excitation of a static ( w = 0 ) magnetic field mode in a plasma has been theorized for close to 30 years, but has never been observed experimentally. This mode has also been referred to alternatively as the "picket fence" or "free streaming" mode, reflecting the fact that it is supported by steady state current loops with alternating sense of direction ( k * 0 ) in the plasma. We present PIC simulations and preliminary experimental results of work being done at USC and UCLA to measure the free streaming mode when a moving gaslplasma boundary (e.g., created by a short laser pulse) moves either through a static electric field (e.g., an electric wiggler) or an incident electromagnetic wave. Comparisons of the experimental and simulations results with analytical results are also presented.

We are studying chemical neutralization and surface decontamination using atmospheric plasma discharges. The plasma can be generated using either DC, AC or pulsed discharges. The electrodes which generate the plasma consist of a ground plane and an array of pins. The array is constructed so that various gases, like argon or helium, can be flowed past the pins where the discharge is initiated. Results indicate that the atmospheric plasma is effective in sterilizing surfaces with biological contaminants like E-coli and bacillus. Exposure times of less than four minutes in an air plasma result in a decrease in live colony counts by six orders of magnitude. Results on neutralization of chemical warfare agent simulants will also be presented. The decomposition chemistry, by-product formation, and electrical energy consumption of the system will be discussed. Standard characterization techniques for determining composition of the processed gaseous and liquid effluents, like gas chromatography and mass spectroscopy, are being utilized.

We have produced a one-atmosphere DC glow discharge plasma with a density (so far) of 1011 km3. The basic discovery is twofold: First, we have found a theorem that shows that any complex AC geometry containing materials of varying dielectric constant can be replaced by a DC system containing materials of varying electrical conductivity. The geometries of the electric field lines are identical, as long as the varying permittivity in the AC system is matched by the varying conductivity in the DC system: Second, we have found a suitable electrode material for the DC case that replaces the dielectriccoated metal electrodes for the AC case. This new electrode material is inexpensive and robust This new material is presently proprietary (A patent is pending.), but is to be discussed at ICOPS. In addition, we intend to present photographs of the apparatus in operation, as well as samples of the new electrode material. system are that it is less expensive and more efficient, as no RF power supply is necessary. Actually, 60 Hz line power can also be used, and a simple neon sign transformer suffices for experimental work. This plasma can be used for chemical and biological decontamination, as well as surface modification. AbstractNon-equilibrium plasmas have been shown to be excellent sterilization agents [