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

Progress in the area of MHD stability and disruptions, since the publication of the 1999 ITER Physics Basis document (1999 Nucl. Fusion 39 2137-2664), is reviewed. Recent theoretical and experimental research has made important advances in both understanding and control of MHD stability in tokamak plasmas. Sawteeth are anticipated in the ITER baseline ELMy H-mode scenario, but the tools exist to avoid or control them through localized current drive or fast ion generation. Active control of other MHD instabilities will most likely be also required in ITER. Extrapolation from existing experiments indicates that stabilization of neoclassical tearing modes by highly localized feedback-controlled current drive should be possible in ITER. Resistive wall modes are a key issue for advanced scenarios, but again, existing experiments indicate that these modes can be stabilized by a combination of plasma rotation and direct feedback control with non-axisymmetric coils. Reduction of error fields is a requirement for avoiding non-rotating magnetic island formation and for maintaining plasma rotation to help stabilize resistive wall modes. Recent experiments have shown the feasibility of reducing error fields to an acceptable level by means of non-axisymmetric coils, possibly controlled by feedback. The MHD stability limits associated with advanced scenarios are becoming well understood theoretically, and can be extended by tailoring of the pressure and current density profiles as well as by other techniques mentioned here. There have been significant advances also in the control of disruptions, most notably by injection of massive quantities of gas, leading to reduced halo current fractions and a larger fraction of the total thermal and magnetic energy dissipated by radiation. These advances in disruption control are supported by the development of means to predict impending disruption, most notably using neural networks. In addition to these advances in means to control or ameliorate the consequences of MHD instabilities, there has been significant progress in improving physics understanding and modelling. This progress has been in areas including the mechanisms governing NTM growth and seeding, in understanding the damping controlling RWM stability and in modelling RWM feedback schemes. For disruptions there has been continued progress on the instability mechanisms that underlie various classes of disruption, on the detailed modelling of halo currents and forces and in refining predictions of quench rates and disruption power loads. Overall the studies reviewed in this chapter demonstrate that MHD instabilities can be controlled, avoided or ameliorated to the extent that they should not compromise ITER operation, though they will necessarily impose a range of constraints.

https://iopscience.iop.org/article/10.1088/0029-5515/47/6/S03/pdf

Chapter 3: MHD stability, operational limits and disruptions

The understanding and predictive capability of transport physics and plasma confinement is reviewed from the perspective of achieving reactor-scale burning plasmas in the ITER tokamak, for both core and edge plasma regions. Very considerable progress has been made in understanding, controlling and predicting tokamak transport across a wide variety of plasma conditions and regimes since the publication of the ITER Physics Basis (IPB) document (1999 Nucl. Fusion 39 2137-2664). Major areas of progress considered here follow. (1) Substantial improvement in the physics content, capability and reliability of transport simulation and modelling codes, leading to much increased theory/experiment interaction as these codes are increasingly used to interpret and predict experiment. (2) Remarkable progress has been made in developing and understanding regimes of improved core confinement. Internal transport barriers and other forms of reduced core transport are now routinely obtained in all the leading tokamak devices worldwide. (3) The importance of controlling the H-mode edge pedestal is now generally recognized. Substantial progress has been made in extending high confinement H-mode operation to the Greenwald density, the demonstration of Type I ELM mitigation and control techniques and systematic explanation of Type I ELM stability. Theory-based predictive capability has also shown progress by integrating the plasma and neutral transport with MHD stability. (4) Transport projections to ITER are now made using three complementary approaches: empirical or global scaling, theory-based transport modelling and dimensionless parameter scaling (previously, empirical scaling was the dominant approach). For the ITER base case or the reference scenario of conventional ELMy H-mode operation, all three techniques predict that ITER will have sufficient confinement to meet its design target of Q = 10 operation, within similar uncertainties.

https://iopscience.iop.org/article/10.1088/0029-5515/47/6/S02/pdf

Chapter 2: Plasma confinement and transport

1 The Equations of Gas Dynamics 2 Magnetoplasma Dynamics 3 Waves in Magnetoplasmas 4 Magnetoplasma Stability 5 Transport in Magnetoplasmas 6 Extensions of Theory Bibliography Index

Physics of plasmas

The advantages of nuclear fusion as an energy source and research progress in this area are summarized. The current state of the art is described. Laser fusion, inertial confinement fusion, and magnetic fusion (the tokamak) are explained, the latter in some detail. Remaining problems and planned future reactors are considered. They are the Compact Ignition Tokamak (CIT), the International Thermonuclear Experimental Reactor (ITER), and a US design called TIBER II. The design of the latter is shown. >

http://ieeexplore.ieee.org/iel1/45/1370/00031587.pdf

Nuclear fusion

Introduction Continuous wavelet transform using analytical wavelets have been used in analysing transient signals from fusion devices for quite some time [1]. Instantaneous frequencies, amplitudes and mode numbers have been calculated by these methods with a reasonably good time resolution often based on only one or two signals [1, 2]. This paper presents wavelet based methods for detecting short-lived plasma eigenmodes and determining their spatial structure by synthesizing information from several signals. Wavelet minimum coherence The wavelet minimum coherence method is the generalization of the ordinary wavelet coherence [3], and can safely detect low amplitude coherent modes at the expense of only a small loss in temporal resolution by synthetising information of all available signals. Wavelet coherence is calculated by the formula:

/pdf/a-wavelet-based-method-for-detecting-transient-plasma-waves-2sjj7yuf1e.pdf

A wavelet based method for detecting transient plasma waves and determining their spatial structure

Studies of fast MHD events in ASDEX-U suggest that stochastization plays an important role in these processes. In spite of the short time duration and small region of stochastization, it can lead to strong changes in plasma confinement. Main reason for such influence is a strong mixing of the magnetic field lines which destroy magnetic surfaces and strongly increase radial transport. In this paper three such phenomena are discussed: frequently interrupted regime of neoclassical tearing mode (FIR-NTM), minor disruption due to interaction of the (2,1) and (3,1) tearing modes and sawtooth crash. The role of stochastization of magnetic field lines is analyzed by applying the mapping technique to trace the field lines of toroidally confined plasma. The sawtooth crash dynamics is also studied by means of spectral analysis and reconstruction of phase trajectories using delay coordinates which are standard techniques for stochastic systems and have been employed for identification of the transition to chaos in different physical systems.

http://www-pub.iaea.org/MTCD/Meetings/FEC2008/ex_p9-10.pdf

The role of stochastization in fast MHD phenomena on ASDEX Upgrade

The transient power load on plasma facing components caused by edge localised modes (ELMs) in H-mode plasmas can be critically high for large size toroidal machines like ITER, therefore it is of high importance to develop methods to mitigate this effect. Pellet ELM pacemaking - the injection of frequent small and shallow penetrating cryogenic pellets - has been found to be a promising mitigation technique. Pellets injected into ELMy H-mode plasmas have been found to be able to trigger prompt ELMs. To be able to predict the capability of the pellet ELM triggering in future toroidal machines and to optimise the ELM pacemaking tool the understanding of the trigger mechanism is indispensable.

/pdf/investigation-of-pellet-driven-plasma-perturbations-for-elm-1e55j47e6j.pdf

Investigation of pellet-driven plasma perturbations for ELM triggering studies

There is a long history of the use of continuous linear time-frequency transforms in the analysis of transients detected in fusion plasma devices [1]. Despite the fact that numerous alternative methods of time-frequency analysis were proposed during the years, Fourier transform based solutions are still the standard method to approach transient wave-like phenomena. The reason for this continued popularity is that these linear time-frequency transforms do not produce any disturbing interference patterns between the time-frequency atoms, eigenfunctions of linear and quasi-linear theories [2]. This paper concentrates on continuous transforms that are time-shift invariant, thus ideal for the analysis of transient signals (for example: chirps, sawtooth, ELMs, EPMs, etc.). The two well-known types of continuous linear time-frequency transforms, namely the short-time Fourier transform and the continuous wavelet transform with analytical wavelets, differ mainly in their invariance properties, which determines their optimal field of use. Uncertainty estimation of transform values and derived quantities, like energy density distributions and phases, is also addressed. Finally, the paper presents some advanced methods based on the time-frequency transforms that have been implemented in the recently developed NTI Wavelet Tools package with practical fusion plasma applications. A mode number determination routine is a main feature, for an application on sawtooth crash analysis see [3]. It is based on fitting mode phases, and now it also provides the uncertainty of the estimated values. Time-frequency coherence and transfer functions are introduced briefly, and time-frequency bicoherence is discussed concentrating on consequences of the invariance properties of the transforms used.

/pdf/continuous-linear-time-frequency-transforms-in-the-analysis-1iww48h5ea.pdf

Continuous linear time-frequency transforms in the analysis of fusion plasma transients

https://iopscience.iop.org/article/10.1088/1741-4326/ab0f82/pdf

V. Igochine

Papers

A wavelet based method for detecting transient plasma waves and determining their spatial structure

The role of stochastization in fast MHD phenomena on ASDEX Upgrade

Investigation of pellet-driven plasma perturbations for ELM triggering studies

Continuous linear time-frequency transforms in the analysis of fusion plasma transients

Impact of n = 1 field on the non-axisymmetric magnetic perturbations associated with the edge localized mode crashes in the ASDEX Upgrade tokamak