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

Phd by thesis

Recent research and development has been incredibly successful at advancing the capabilities for vacuum electronic device (VED) sources of powerful terahertz (THz) and near-THz coherent radiation, both CW or average and pulsed. Currently, the VED source portfolio covers over 12 orders of magnitude in power (mW-to-GW) and two orders of magnitude in frequency (from ; 10 THz). Further advances are still possible and anticipated. They will be enabled by improved understanding of fundamental beam-wave interactions, electromagnetic mode competition and mode control, along with research and development of new materials, fabrication methods, cathodes, electron beam alignment and focusing, magnet technologies, THz metrology and advanced, broadband output radiation coupling techniques.

Vacuum Electronic High Power Terahertz Sources

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.

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The electron cyclotron maser

This article reviews the state-of-the-art in high-power microwave source research. It begins with a discussion of the concepts involved in coherent microwave generation. The main varieties of microwave tubes are classified into three groups, according to the fundamental radiation mechanism involved: Cherenkov, transition, or bremsstrahlung radiation. This is followed by a brief discussion of some of the technical fundamentals of high-power microwave sources, including power supplies and electron guns. Finally, the history and recent developments of both high-peak power and high-average power sources are reviewed in the context of four main areas of application: (1) plasma resonance heating and current drive; (2) rf acceleration of charged particles; (3) radar and communications systems; and (4) high-peak power sources for weapons-effect simulation and exploratory development.

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Review of high-power microwave source research

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Plasma Physics and Controlled Fusion Conference: Focussing on Tokamak Research

Methods for realization of two-wave gyro-oscillators with frequency multiplication provided in a single operating cavity are proposed. A possibility for realization of a moderately-relativistic (250 keV) THz gyro-multiplier operating at 5-6 cyclotron harmonic with the output power of about 1 kW, as well as of an analogous weakly-relativistic (80 keV) CW device with the output power of 1 W, is demonstrated.

High-harmonic gyrodevices with frequency multiplication

A new scheme of quasi-optical HE11 mode exciter is presented. It consists of a smooth rectangular horn, dielectric focusing lens and output waveguide section. The main advantages of the converter are frequency broad band operation and simple design. Results of measurements of converter parameters performed at millimeter waves agree well with the design parameters: total conversion efficiency exceeds 96% in the frequency band of 20%.

Efficient Broad Band HE11 Mode Exciter

The use of the two-wave co-generation is proposed as a way to decrease the effective Q-factor of the operating near-cutoff wave of the gyrotron. In this two-wave regime, the operating wave represents a “hot” wave mode formed by two partial “cold” modes (near-cutoff and far-from-cutoff ones) coupled on the electron beam. It is shown that the use of this regime can provide a significant decrease of the Ohmic losses in low-relativistic high-harmonic gyrotrons operating in the THz frequency range.

Two-wave regime of operation of the high-harmonic gyrotron

Presently, Ka-band ultrashort pulse (USP) generator is under development at Institute of Applied Physics RAS. Based on a time-domain model and direct PIC simulations we demonstrate that a periodic train of ultrashort microwave pulses can be generated in an electron oscillator consisting of a helically corrugated gyro-TWT and a saturable absorber based on cyclotron resonance interaction of radiation with an initially rectilinear electron beam. The gyro-TWT operates at the second cyclotron harmonic while in the absorber interaction at the fundamental harmonic should be realized. According to simulations with parameters of existing Ka-band gyro-TWT, the peak power of generated pulses with a duration of 200 ps and repletion frequency 1 GHz is about 400 kW.

Development of Ultrashort Pulse Generators based on Helical Gyro-TWT with Saturable Cyclotron Resonance Absorber in the Feedback Loop

For the upper ECW launcher on ITER, the use of a “remote steering antenna” based on the imaging properties of rectangular waveguides is planned. To characterise launchers of this type, low-power experiments on a 4-side corrugated square waveguide with a scanning mirror at the input of the waveguide were performed in the frequency range of 140 to 160 GHz. It is shown, that elliptical polarisation needed for ECCD can be transmitted without depolarisation. The usable steering range of the antenna is at least -10” < cp 5 +lo”. Experiments with the scanning plane in the diagonal of the square waveguide led to a negligible increase the scanning range, and lobes in the upward and downward direction are detected at larger scanning angles. Mitre bends can be integrated into the waveguide without prohibitive extra loss, which is demonstrated by far-field measurements. Detailed calorimetric measurements for this set up confirm this statement for the polarisation perpendicular to the scanning plane, whereas extra loss is measured for the parallel polarisation. Results are discussed and are compared to theory.

G. G. Denisov

Papers

High-harmonic gyrodevices with frequency multiplication

Efficient Broad Band HE11 Mode Exciter

Two-wave regime of operation of the high-harmonic gyrotron

Development of Ultrashort Pulse Generators based on Helical Gyro-TWT with Saturable Cyclotron Resonance Absorber in the Feedback Loop

Performance of a remote steering antenna for ECRH/ECCD applications using 4-Wall corrugated square wave-guide