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Sawtooth oscillations in tokamaks frequently lead to the redistribution of energetic ions, mainly on passing orbits, causing their expulsion from the core. This paper discusses the first measurements of the interaction of fast ions and sawteeth in the Large Helical Device. The crashes were caused by the plasma current induced by Electron Cyclotron Current Drive and Neutral Beam Current Drive. Despite these crashes, there was no detectable redistribution effect on fast ions in either the core or at the edge of the plasma.

The anomalous transport of a high temperature plasma in the region of stochastic magnetic field is studied. Toroidal plasmas, such as tokamak's, are considered. Using the kinetic equation for plasma particles in the stochastic magnetic field, the plasma transport matrix in the stochastic region is formulated. A quasilinear approximation for the diffusivity of the magnetic field line D_M is used. The shifted Maxwellian which includes the mean velocity and the self-consistent electric potential is assumed. By use of this transport matrix the radial electric field formation, which is generated by ambipolar condition, and the associated temperature distribution in the stochastic region is obtained. The temperature distribution in the stochastic region becomes flat because of the rapid temperature diffusion. The radial electric field is formed in the stochastic region and its magnitude is found to depend on the value of D_M, and on the conditions of the heat fluxes and temperature gradients of electrons and ions in the nonstochastic region.

The sawtooth instability is known for inducing transport and loss of energetic particles (EPs), and for generating seed magnetic islands that can trigger tearing modes. Both effects degrade the overall plasma performance. Several theories and numerical models have been previously developed to quantify the expected EP transport caused by sawteeth, with various degrees of sophistication to differentiate the response of EPs at different energies and on different orbits (e.g. passing vs. trapped), although the analysis is frequently limited to a single time slice during a tokamak discharge. This work describes the development and initial benchmark of a framework that enables a reduced model for EP transport by sawteeth retaining the full EP phase-space information. The model, implemented in the ORBIT hamiltonian particle-following code, can be used either as a standalone post-processor taking input data from codes such as TRANSP, or as a pre-processor to compute transport coefficients that can be fed back to TRANSP for time-dependent simulations including the effects of sawteeth on EPs. The advantage of the latter approach is that the evolution of the EP distribution can be simulated quantitatively for sawtoothing discharges, thus enabling a more accurate modeling of sources, sinks and overall transport properties of EP and thermal plasma species for comprehensive physics studies that require detailed information of the fast-ion distribution function and its evolution over time.

The aim of this study is to examine the public preferences for urban riparian corridors in arid ‎regions, by testing to what extent people are willing to trade-off unmaintained ecological ‎landscape for aesthetics offered by specific micro and ‎macro environmental factors. Landscape ‎design reflects ecological and aesthetic values, and trade-offs are often made ‎between the two in ‎‎practice. In arid regions, water scarcity means riparian corridors are the ‎richest landscape ‎typology and the only ‎blue-green links for hundreds of miles. Pressure from ‎urbanization and ‎lack of eco-literacy contribute to negative ‎feedback loops which present dire ‎challenges for ‎migrating avifauna and regional wildlife. Regarding natural ‎resources and ‎biodiversity, where ‎multiple deliverable ‎ecosystem services rely on the quality and health of that ‎‎ecosystem, riparian ‎systems with high biomass are more desirable. Although this can be ‎achieved with low or no ‎‎maintenance riparian buffers, these unmaintained ecological landscapes ‎play an intrinsic role in ‎sustaining the ‎global ecosystem services and are important for the survival of the inhabitants ‎‎(avifauna). Ecological ‎landscapes are often subjected to trade-offs with aesthetic ‎landscapes that ‎include micro and ‎macro environmental factors such as manicured landscapes. It is accepted that ‎‎there is a ‎preference for aesthetics in landscape design; however, it is unclear how laypeople ‎prioritize ‎aesthetics ‎over different ecological factors in landscape scenes. This study uses a ‎Discrete Choice ‎Experiment (DCE) to elicit the ‎preferences of current or pretendant residents of ‎Jeddah City, Saudi Arabia for multiple landscape scenes. The method ‎combines ecological ‎landscape characteristics adopted from ‎the QBR index that are found in the study area in Jeddah ‎and aesthetic ‎characteristics, such as micro and macro environmental factors that are commonly ‎suggested in landscape design projects adapted from rel

The effect of the sawtooth instability on the confinement of fast ions on MAST, and the impact it has on the neutron emission, has been studied in detail using the TRANSP/NUBEAM codes coupled to a full orbit following code. The sawtooth models in TRANSP/NUBEAM indicate that, on MAST, passing and trapped fast ions are redistributed in approximately equal number and on a level that is consistent with the observations. It has not been possible to discriminate between the different sawtooth models since their predictions are all compatible with the neutron camera observations. Full orbit calculations of the fast ion motion have been used to estimate the characteristic time scales and energy thresholds that according to theoretical predictions govern the fast ions redistribution: no energy threshold for the redistribution for either passing and trapped fast ions was found. The characteristic times have, however, frequencies that are comparable with the frequencies of a m = 1, n = 1 perturbation and its harmonics with toroidal mode numbers n = 2, ..., 4, suggesting that on spherical tokamaks, in addition to the classical sawtooth-induced transport mechanisms of fast ions by attachment to the evolving perturbation and the associated E x B drift, a resonance mechanism between the m = 1 perturbation and the fast ions orbits might be at play., Correction in: PLASMA PHYSICS AND CONTROLLED FUSION, Volume: 61, Issue: 12, Article Number: 129501, DOI: 10.1088/1361-6587/ab503d

A motional Stark effect (MSE) diagnostic has recently been installed in the KSTAR tokamak. A difficulty faced at KSTAR and common to other MSE diagnostics is calibration of the system for absolute measurements. In this report we present our novel calibration routine and discuss first results, evaluating the evolution of the the central safety factor during sawtooth instabilities. The calibration scheme ensures that the bandpass filters typically used in MSE systems are aligned correctly and identifies and removes systematic offsets present in the measurement. This is verified by comparing the reconstructed safety factor profile against various discharges where the locations of rational q surfaces have been obtained from MHD markers. The calibration is applied to analyse the evolution of q 0 in a shot where the sawteeth are stabilized by neutral beam injection. Within the analysed sawtooth periods q 0 drops below unity during the quiescent phase and relaxes close to or slightly above unity at the sawtooth crash. This finding is in line with the classical Kadomtsev model of full magnetic reconnection and earlier findings at JET.

A novel technique for sawteeth control in tokamak plasmas using ion-cyclotron resonance heating (ICRH) has been developed in the JET-ILW tokamak. Unlike previous ICRH methods, that explored the destabilization of the internal kink mode when the radio-frequency (RF) wave absorption was placed near the q = 1 surface, the technique presented here consists of stabilizing the sawteeth as fast as possible by applying the ICRH power centrally and subsequently induce a sawtooth crash by switching it off at the appropriate instant. The validation of this method in JET-ILW L-mode discharges, including preliminary tests in H-mode plasmas, is presented., For complete list of authors see http://dx.doi.org/10.1088/1741-4326/aa53b6

In the non-linear phase of a sawtooth, the complete reconnection of field lines around the q = 1 flux surface often occurs resulting in a radial displacement of the plasma core. A complete time-dependent electromagnetic model of this type of reconnection has been developed and implemented in the EBdyna-go code. This contribution aims at studying the behaviour of ions, both impurity and fast particles, in the pattern of reconnecting field lines during sawtoothing plasma experiments in the ASDEX Upgrade tokamak by using the newly developed numerical framework. Simulations of full reconnection with tungsten impurity that include the centrifugal force are achieved and recover the soft x-ray measurements. Based on this full-reconnection description of the sawtooth, a simple tool dedicated to estimate the duration of the reconnection is introduced. This work then studies the redistribution of fast ions during several experimentally observed sawteeth. In some cases of sawteeth at ASDEX Upgrade, full reconnection is not always observed or expected so the code gives an upper estimate of the actual experimental redistribution. The results of detailed simulations of the crashes are compared with measurements from various diagnostics such as collective Thomson scattering and fast-ion D-alpha (FIDA) spectroscopy, including FIDA tomography. A convincing qualitative agreement is found in different parts of velocity space.

Control of the time between sawtooth crashes, necessary for ITER and DEMO, requires real-time detection of the moment of the sawtooth crash. In this paper, estimation of sawtooth crash times is demonstrated using the model-based interacting multiple model (IMM) estimator, based on simplified models for the sawtooth crash. In contrast to previous detectors, this detector uses the spatial extent of the sawtooth crash as detection characteristic. The IMM estimator is tuned and applied to multiple ECE channels at once. A model for the sawtooth crash is introduced, which is used in the IMM algorithm. The IMM algorithm is applied to seven datasets from the ASDEX Upgrade tokamak. Five crash models with different mixing radii are used. All sawtooth crashes that have been identified beforehand by visual inspection of the data, are detected by the algorithm. A few additional detections are made, which upon closer inspection are seen to be sawtooth crashes, which show a partial reconnection. A closer inspection of the detected normal crashes shows that about 42% are not well fitted by any of the full reconnection models and show some characteristics of a partial reconnection. In some case, the measurement time is during the sawtooth crashes, which also results in an incorrect estimate of the mixing radius. For data provided at a sampling rate of 1 kHz, the run time of the IMM estimator is below 1 ms, thereby fulfilling real-time requirements.

Fast-ion transport caused by the combination of MHD and a mock-up test-blanket module (TBM) coil is measured in the DIII-D tokamak. The primary diagnostic is an infrared camera that measures the heat flux on the tiles surrounding the coil. The combined effects of the TBM and four other potential sources of transport are studied: neoclassical tearing modes, Alfn eigenmodes, sawteeth, and applied resonant magnetic perturbation fields for the control of edge localized modes. A definitive synergistic effect is observed at sawtooth crashes where, in the presence of the TBM, the localized heat flux at a burst increases from 0.36 ± 0.27 to 2.6 ±0.5 MW m-2.

Civil Engineering and Geosciences

The study area contains large undeveloped mineral resources, part of which can be identified as reserves and part as marginal or submarginal resources. The principal resources that are known, in estimated order of decreasing potential value are Mo, Zn, Ag, Pb, fluorite, Sb and Cd. Ni, U, Th, rare earths and Ti are potential coproducts of possible future mining of placer gold deposits. Smaller amounts of Cu, Sn, W, Bi, Hg, Se, and Te are present. Four large deposits contain the major part of the total resources. The investigation included an aeromagnetic survey, reconnaissance geologic mapping, extensive sampling, studies of known mineral deposits and mining claims, and detailed geochemical and geophysical studies of five areas considered favourable for further mineral exploration., The study area contains large undeveloped mineral resources, part of which can be identified as reserves and part as marginal or submarginal resources. The principal resources that are known, in estimated order of decreasing potential value are Mo, Zn, Ag, Pb, fluorite, Sb and Cd. Ni, U, Th, rare earths and Ti are potential coproducts of possible future mining of placer gold deposits. Smaller amounts of Cu, Sn, W, Bi, Hg, Se, and Te are present. Four large deposits contain the major part of the total resources. The investigation included an aeromagnetic survey, reconnaissance geologic mapping, extensive sampling, studies of known mineral deposits and mining claims, and detailed geochemical and geophysical studies of five areas considered favourable for further mineral exploration.