Design, simulation and experiment of a cusp electron beam for millimeter wave gyro-devices

The design, simulation and experiment of a thermionic cusp electron gun that is to be used for millimeter wave generation will be presented. A cusp gun uses a non-adiabatic magnetic field reversal to obtain azimuthal motion on an electron beam resulting in an annular shaped, axis-encircling beam. The cusp gun was designed to generate a beam of 1.5A at 40kV with an adjustable velocity ratio of up to 3.0. The beam had a simulated axial velocity spread of 7.4% and alpha spread of 10.1%. The beam had an averaged radius of 0.35mm and beam thickness of 0.05mm which is ideal to drive sub-mm wave gyro-devices under investigation

The M33 Synoptic Stellar Survey. II. Mira Variables

We present the discovery of 1847 Mira candidates in the Local Group galaxy M33 using a novel semi-parametric periodogram technique coupled with a Random Forest classifier. The algorithms were applied to ~2.4x10^5 I-band light curves previously obtained by the M33 Synoptic Stellar Survey. We derive preliminary Period-Luminosity relations at optical, near- & mid-infrared wavelengths and compare them to the corresponding relations in the Large Magellanic Cloud.Comment: Includes small corrections to match the published versio

Optimization of a triode-type cusp electron gun for a W-band gyro-TWA

A triode-type cusp electron gun was optimized through numerical simulations for a W-band gyrotron traveling wave amplifier. An additional electrode in front of the cathode could switch the electron beam on and off instantly when its electric potential is properly biased. An optimal electron beam of current 1.7 A and velocity ratio (alpha) of 1.12 with an alpha spread of ~10.7% was achieved when the triode gun was operated at 40 kV

Bandwidth study of the microwave reflectors with rectangular corrugations

The mode-selective microwave reflector with periodic rectangular corrugations in the inner surface of a circular metallic waveguide is studied in this paper. The relations between the bandwidth and reflection coefficient for different numbers of corrugation sections were studied through a global optimization method. Two types of reflectors were investigated. One does not consider the phase response and the other does. Both types of broadband reflectors operating at W-band were machined and measured to verify the numerical simulations

Vapor copper : a potential wood preservative

This study seeks to determine the feasibility of utilizing one vaporizable copper compound - bis-[1- (dimethylamino)-2-propanolato] copper(II) (Cu(DMAP)₂ as a potential wood preservative. The synthesis of Cu(DMAP)₂ was conducted in accordance with a method developed by Buhro and Dingman, Washington University, St. Louis, Missouri. The yields of Cu(DMAP)₂ synthesis were about 58%. Preservative treatment of oriented strand board(OSB) using Cu(DMAP)₂ applied in the vapor phase was investigated. Under optimum conditions complete penetration of OSB was achieved. In addition, commercial levels of copper retentions was obtained. Treatment time and temperature has a major influence on copper retention and penetration. The leachability test of Cu(DMAP)2 was performed using a modification of AWPA Standard E-11 and results told us that Cu(DMAP)₂ and ammoniacal copper sulfate (ACS) had similar leaching behavior. The efficacy of Cu(DMAP)₂ as a preservative was assessed using soil block test and compared to ACS and chromated copper arsenate (CCA). Cu(DMAP)₂ was slightly more effective than ACS at low retention in leached samples, but it was slightly less effective than either ACS or CCA at higher retentions

Wide-band HE11 mode terahertz wave windows for gyro-amplifiers

Broadband HE11 mode output windows, based on the multilayer concept, are studied for high power gyro-amplifiers operating in the low terahertz region. As the wave power in the hybrid HE11 mode is concentrated in the center of the circular waveguide, smaller reflection and better coupling to the fundamental free space Gaussian mode can be achieved for the windows. Two windows are designed for optimized performance through simulations for operation in two frequency ranges of 360– 400 GHz and 90–100 GHz. The simulated performance, practical constraints in realization and manufacturing methods of the 90–100 GHz window is discussed. This window was constructed and microwave properties measured showing a lower than -27 dB reflection. This result agrees with simulation data which validates the simulation methodology and effectiveness of the design

Measurement of a W-band output launcher system for a broadband gyro-TWA

An output system for a W-band (90-100 GHz) gyrotron-traveling wave amplifier is designed, simulated, measured and the results are presented. This is an updated system based on a previous design and the output shows more favorable properties for the amplifiers intended application, as a millimetre wave source in a cloud sensing radar. A greater than -30 dB reflection was measured over the frequency range and high Gaussian content obtained

A pillbox window with impedance matching sections for a W-band gyro-TWA

A mode-matching method was developed to design a pillbox-type millimeter wave window for a W-band gyrotron traveling wave amplifier. With additional impedance matching sections, the pillbox window was able to achieve -40 dB reflection over a 10% frequency bandwidth. The manufactured pillbox window achieved a maximum reflection of -15 dB. The reasons for the difference between the simulated and measured reflections were investigated

Investigation on the optimal magnetic field of a cusp electron gun for a W-band gyro-TWA

High efficiency and broadband operation of a gyrotron traveling wave amplifier (gyro-TWA) requires a high-quality electron beam with low-velocity spreads. The beam velocity spreads are mainly due to the differences of the electric and magnetic fields that the electrons withstand the electron gun. This paper investigates the possibility to decouple the design of electron gun geometry and the magnet system while still achieving optimal results, through a case study of designing a cusp electron gun for a W-band gyro-TWA. A global multiple-objective optimization routing was used to optimize the electron gun geometry for different predefined magnetic field profiles individually. Their results were compared and the properties of the required magnetic field profile are summarized