Colin G. Whyte

Bio: Colin G. Whyte is an academic researcher from University of Strathclyde. The author has contributed to research in topics: Microwave & Beam (structure). The author has an hindex of 28, co-authored 176 publications receiving 2553 citations. Previous affiliations of Colin G. Whyte include Cockcroft Institute & University of Glasgow.

Gyrotron traveling wave amplifier with a helical interaction waveguide

Abstract: A new microwave system in the form of a cylindrical waveguide with a helical corrugation of the inner surface is proposed for a gyrotron traveling wave tube (gyro-TWT). The corrugation radically changes the wave dispersion in the region of small axial wave numbers. This allows significant reduction in the sensitivity of the amplifier to the electron velocity spread and an increase in its frequency bandwidth. An X-band gyro-TWT operating at the second cyclotron harmonic with a 200-keV, 25-A electron beam produced an output power of 1 MW, corresponding to a gain of 23 dB and an efficiency of 20%.

High-gain wide-band gyrotron traveling wave amplifier with a helically corrugated waveguide

Abstract: First bandwidth measurements of a novel gyrotron amplifier are presented The coupling between the second harmonic cyclotron mode of a gyrating electron beam and the radiation field occurred in the region of near infinite phase velocity over a broad bandwidth by using a cylindrical waveguide with a helical corrugation on its internal surface With a beam energy of 185 keV, the amplifier achieved a maximum output power of 11 MW, saturated gain of 37 dB, linear gain of 47 dB, saturated bandwidth of 84 to 104 GHz ( $21%$ relative bandwidth), and an efficiency of $29%$, in good agreement with theory

A cusp electron gun for millimeter wave gyrodevices

Abstract: 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 α 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.

Helically corrugated waveguide gyrotron traveling wave amplifier using a thermionic cathode electron gun

Abstract: Experimental operation of a gyrotron traveling wave amplifier with a helically corrugated waveguide using a thermionic cathode electron gun is presented. The coupling between the second harmonic cyclotron mode of the gyrating electron beam and the radiation occurred in the region of near infinite phase velocity over a broad frequency band. With an axis-encircling electron beam of pitch factor of ∼1.2, energy of 185keV, and current of 6.0A, the amplifier achieved an output power of 220kW, saturated gain of 24dB, saturated bandwidth of 8.4to10.4GHz, and an interaction efficiency of 20%.

Gyro-BWO experiments using a helical interaction waveguide

Abstract: A helically corrugated waveguide was used for a gyrotron backward-wave oscillator (gyro-BWO) experiment. A thermionic cathode was used to produce an electron beam of 90-215 keV in energy, 2-3 A in current, and pitch alpha of up to 1.6. The oscillator achieved high-efficiency frequency-tunable operation. At a fixed beam voltage of 185 kV and a current of 2 A, the output frequency was tuned by adjusting the magnetic field in the interaction cavity. A maximum power of 62 kW and a 3-dB frequency-tuning band of 8.0-9.5 GHz (17% relative tuning range) with a maximum electronic efficiency of 16.5% were measured. In addition, the interaction frequency could be tuned by varying the electron beam energy. At a fixed cavity magnetic field of 0.195 T, the output frequency and power from the gyro-BWO were measured as a function of tuning electron beam energy while the beam current was maintained at 2.5 A. A 3-dB relative frequency tuning range of 8% was measured when the electron beam voltage was changed from 215 to 110 kV.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

The electron cyclotron maser

Abstract: The electron cyclotron maser (ECM) is based on a stimulated cyclotron emission process involving energetic electrons in gyrational motion. It constitutes a cornerstone of relativistic electronics, a discipline that has emerged from our understanding and utilization of relativistic effects for the generation of coherent radiation from free electrons. Over a span of four decades, the ECM has undergone a remarkably successful evolution from basic research to device implementation while continuously being enriched by new physical insights. By delivering unprecedented power levels, ECM-based devices have occupied a unique position in the millimeter and submillimeter regions of the electromagnetic spectrum, and find use in numerous applications such as fusion plasma heating, advanced radars, industrial processing, materials characterization, particle acceleration, and tracking of space objects. This article presents a comprehensive review of the fundamental principles of the ECM and their embodiment in practical devices.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

Abstract: Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

Proof of Concept

Abstract: The previous part discusses the GI/BSI/DFKI Protection Profile which constitutes after the implementation of the identified improvements as the proposed evaluation methodology for remote electronic voting systems. The result can now be applied to available systems. Currently, there is no system that has been evaluated against the GI/BSI/DFKI Protection Profile or even against the improved version.

北京大学濮祖荫教授被推选为国际著名期刊Journal of Geophysical Research——Space Physics的主编

Abstract: 北京大学地球与空间科学学院濮祖荫教授被美国地球物理学会任命为Journal of Geophysical Research（Space Physics）的新一届亚洲与太平洋区域主编，任期为4年（2006-2009）．