A cusp electron gun for millimeter wave gyrodevices

The experimental results of a thermionic cusp electron gun, to drive millimeter and submillimeter wave harmonic gyrodevices, are reported in this paper. Using a "smooth" magnetic field reversal formed by two coils this gun generated an annular-shaped, axis-encircling electron beam with 1.5 A current, and an adjustable velocity ratio alpha of up to 1.56 at a beam voltage of 40 kV. The beam cross-sectional shape and transported beam current were measured by a witness plate technique and Faraday cup, respectively. These measured results were found to be in excellent agreement with the simulated results using the three-dimensional code MAGIC

Cognitive Information Processing

Contains reports on four research projects.National Science Foundation (Grant G-16526)National Institutes of Health (Grant MH-04737-03)National Aeronautics and Space Administration (Grant NsG-496

Multilayer microwave windows for wideband gyro-amplifiers

This paper presents the design and measurement of a HE11 mode multilayer window for a W-band gyro-amplifier. The window acts to seal the vacuum inside the amplifier whilst coupling out microwave power with minimal reflection and absorption. The Gaussian-like HE11 mode is used in order to achieve the lowest reflection through the window. Operating over 90-100 GHz the simulated reflection of this window is better than -30 dB. The design, simulation and microwave measurement of the window is presented

Development of a new laser Doppler velocimeter for the Ames High Reynolds Channel No. 2

A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. 2 is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to position the laser beams in the channel flow. Techniques used to seed the flow with 0.5-micron-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy

A cusp electron gun for millimeter wave gyro-devices

A thermionic cusp electron gun has been designed, numerically optimized and experimentally measured and is presented. A 40 kV, 1.5 A annular axis-encircling electron beam has been simulated to generate a beam with low velocity and alpha spreads. The electron gun performance has been verified through experiments. Based on the measured results further improvement and optimization of the cusp gun for high frequency operation were carried out and the results will be presented

Demonstration of efficient beam-wave interaction for a MW-level 48 GHz gyroklystron amplifier

The development of high-frequency RF linear accelerators (linacs) requires the consideration of several technological challenges, such as electron bunch linearization. Presented in this paper is the design of the interaction circuit for a 48 GHz MW-level three-cavity gyroklystron amplifier, appropriate for application as a millimeter wave power source in a fourth harmonic linearizing system for an X-band linac. The output cavity is operated at the cylindrical TE0,2,1 mode, while the input and buncher cavities are operated at the TE0,1,1 mode. The interaction circuit has been designed using a combination of analytical calculations and particle-in-cell simulations. The optimized gyroklystron is shown, through simulation, to deliver an output power of up to 2.3 MW with a gain of 36 dB and an efficiency of 44% at 48 GHz, when driven by a 140 kV, 37 A electron beam. The   support   of   the   STFC   UK (Cockcroft Institute Core GrantR160525-1) is gratefully acknowledged. This  work  is  supported  by European Union (EU) Horizon 2020 Project  “CompactLight” 2017-2021. “CompactLight”  grant code: 777431-XLS. Published data March 2020, under Self-archiving / 'green' OA

Latest development of a W-band Gyro-TWA based on a helically corrugated interaction region

Latest development and experimental study of a W-band gyro-TWA with a helically corrugated waveguide and a cusp electron gun are presented. With an input seed signal from an 1.5 W, 90-96 GHz solid state source a gain of 27 dB was measured from the experiment. The bandwidth of the gyro-TWA was measured to be at least 5 GH

Characteristics of Tobacco Users in the Lumber Industry

Cessation interventions for adult smokeless tobacco users may benefit from an improved understanding of the demographic, psychosocial, and tobacco-dependence characteristics of this group. In the current study, 143 employees of the Pacific Lumber Company were interviewed and completed questionnaires about their tobacco use product preference (smokeless tobacco only, cigarettes only, both, and former user), demographic, psychosocial, and tobacco-dependence characteristics. Results of a multivariate discriminant analysis revealed that smokeless-tobacco-only users were younger and reported in engaging in more exercise than did the other three groups; however, they also reported greater dependence on tobacco than did smokers. Formal cessation clinics similar to those that are being used effectively with smokers, and which are age appropriate, may be an effective treatment for adult smokeless tobacco users