Abstract: A method and counter for reducing the background counting rate in gas-filled alpha particle counters wherein the counter is constructed in such a manner as to exaggerate the differences in the features in preamplifier pulses generated by collecting the charges in ionization tracks produced by alpha particles emanating from different regions within the counter and then using pulse feature analysis to recognize these differences and so discriminate between different regions of emanation. Thus alpha particles emitted from the sample can then be counted while those emitted from the counter components can be rejected, resulting in very low background counting rates even from large samples. In one embodiment, a multi-wire ionization chamber, different electric fields are created in different regions of the counter and the resultant difference in electron velocities during charge collection allow alpha particles from the sample and counter backwall to be distinguished.
August 23, 2001
Date of Patent:
May 4, 2004
William K. Warburton, John Wahl, Michael Momayezi
Abstract: The invention is directed to the reduction of an electron beam transport problem during microwave generation in plasma-assisted microwave sources. A small, e.g., <200 gauss, secondary magnetic field is positioned in association with a slow-wave structure (SWS) of the sources to reduce the radial divergence of electron bunches in the sources' electron beams. The secondary magnetic field exerts radial forces on diverging electrons to supplement radial forces of a primary magnetic field and radial forces of an electrostatic field. The primary magnetic field is generated by electron movement in the electron beam and the electrostatic field is generated by ions which are created as the electron beam transits an ionizable gas in the plasma-assisted source. The addition of the secondary magnetic field can be implemented with a coil that is positioned to direct at least a portion of its magnetic field through a passage of the SWS.
Abstract: Plasma wave tubes are disclosed having waveguide injection systems configured for injection of an RF signal to prebunch the electron beam of the tube and thereby control the frequency of an RF output signal. Preferred embodiments of the injection system include a plurality of rectangular waveguides arranged radially about a cylindrical waveguide member and joined to it for communication with its interior. Plasma wave tubes (140) are also disclosed that utilize the injection system as a collector (44C) to couple an RF output signal from the tube.
Abstract: A body of dense plasma is established within a short drift tube of a klysn amplifier between input and output resonator cavities thereof to support current modulation of microwave energy by interaction with an electron beam propagated through the drift tube. The plasma is confined to a column radially spaced from the electron beam for two-stream interaction enabling enhancement of current modulation under simultaneous high-power and high frequency operation.
May 20, 1993
Date of Patent:
January 31, 1995
The United States of America as represented by the Secretary of the Navy
Abstract: A high voltage power supply having energy storage, charging and switching elements and using an interruptible switch as the switching element for efficient, compact and safe operation. In a specific embodiment, the interruptible switch is implemented with at least one cold cathode grid-controlled, crossed field plasma switch and associated control circuit. The charging element is a Marx bank which can be capacitive or inductive. Embodiments with a single master-slave control arrangement, a pulse-forming network providing high voltage regulation, an inductive implementation with a plurality of switching elements in a single envelope with the cathode of at least one switching element being the anode of the next switching element are disclosed. A current amplifier and voltage regulator implemented with a cold cathode grid-controlled, crossed field plasma switch having a cathode, an anode and a control grid therebetween are disclosed.