Generation of E × B flow shear by finite orbit width effects from heat sources in tokamaks

We present a possible mechanism for the generation of strong E × B flow shear relevant to internal transport barrier formation in tokamak plasmas. From gyrokinetic calculations, we show that strong E × B flow shear can be generated by finite orbit width (FOW) effects associated with a non-uniform heat source and is sufficient to lead to transport barrier formation in the core region with a moderate power level. Two FOW effects inducing neoclassical polarization are shown to be responsible for this: 1) the radial drift of particle orbit center due to the variation of the heat source within orbit width and 2) the non-uniformly evolved orbit width by the non-uniform heating.

Túrázók a Pilis és a Visegrádi-hegység területén: a megközelítés problémája - Hiking in the Pilis and Visegrád Hills: the problem of access

A természetjárás növekvő népszerűségét a Covid19-járvány világszerte felerősítette. Legnagyobb mértékben az úgynevezett egynapos, zömében a nagyvárosokhoz közeli desztinációk látogatottsága és így terhelése nőtt meg, illetve megemelkedett a személygépkocsival megtett utazások aránya is. A Pilisi Bioszféra Rezervátum területén végzett, látogatószámlálással egybekötött kérdőíves felmérés eredményei alapján kimutatható többek között, hogy az ismertebb helyszínek esetében nem számít a jó tömegközlekedési összeköttetés, sokan választják az autót. A saját gépkocsival érkezők növekvő aránya egyrészt a természeti értékek károsodásához, másrészt a helybeliekkel kapcsolatos konfliktusokhoz vezet. A felerősödő problémák szükségessé teszik a látogatómenedzsment-eszközök átgondolását, a desztináció megközelíthetőségének és belső közlekedési rendszerének a felülvizsgálatát, valamint a természeti értékek és helyi közösségek érdekeit előtérbe helyező mobilitástervezést. The growing popularity of hiking has been boosted by the Covid19 epidemic worldwide. The largest increases in visitor numbers and thus pollution have been in the so-called one-day destinations, mostly in the peri-urban areas, and travel by car has also increased. The results of a questionnaire survey in the Pilis Biosphere Reserve, which included a visitor census, show, among other things, that good public transport connections are not an important factor for the more well-known sites, and that many people choose to travel by car. The increasing proportion of visitors arriving by private car leads to both damage to natural assets and conflicts with locals. These growing problems call for a rethink of visitor management tools, a review of the destination’s accessibility and internal transport system, comprising overall mobility planning which prioritises the interests of natural assets and local communities.

Progress of HL-2A experiments and HL-2M program

Since the last IAEA Fusion Energy Conference in 2018, significant progress of the experimental program of HL-2A has been achieved on developing advanced plasma physics, edge localized mode (ELM) control physics and technology. Optimization of plasma confinement has been performed. In particular, high-N H-mode plasmas exhibiting an internal transport barrier have been obtained (normalized plasma pressure N reached up to 3). Injection of impurity improved the plasma confinement. ELM control using resonance magnetic perturbation (RMP) or impurity injection has been achieved in a wide parameter regime, including Types I and III. In addition, the impurity seeding with supersonic molecular beam injection (SMBI) or laser blow-off (LBO) techniques has been successfully applied to actively control the plasma confinement and instabilities, as well as the plasma disruption with the aid of disruption prediction. Disruption prediction algorithms based on deep learning are developed. A prediction accuracy of 96.8% can be reached by assembling convolutional neural network (CNN). Furthermore, transport resulted from a wide variety of phenomena such as energetic particles and magnetic islands have been investigated. In parallel with the HL-2A experiments, the HL-2M mega-ampere class tokamak was commissioned in 2020 with its first plasma. Key features and capabilities of HL-2M are briefly presented.

The ITB dynamics controlled by internal kink modes on HL-2A tokamak

The active control of internal transport barriers (ITBs) is an important issue to achieve high performance plasma in a fusion reactor. A critical challenge of ITB control is to increase the ITB position. The ITBs with internal kink modes (IKMs), such as fishbone instability and long-live mode (LLM) with mode number of m/n = 1/1 are frequently observed on HL-2A tokamak in neutral beam heated discharges. The correlation of fishbone instability/LLM with ITBs is analyzed in order to extend the ITB radius. It has been revealed that fishbone instability and LLM are often excited after the ITB formation. Therefore, fishbone instability and LLM play no role in triggering ITBs on HL-2A tokamak. On the other hand, they may slow down the outward radial expansion and then shrink the foot position of ITB, and damp the gradient growth of ion temperature and rotation velocity. Since the perturbation of LLM is weaker than that of fishbone instability, the shrinking effect of ITB foot and braking effect on gradient growth are slighter than those of fishbone instability. Compared with the LLM, fishbone instability routinely appears in plasmas with lower density, higher heating power and lower plasma current. In addition, large ITBs without IKMs are also discussed on HL-2A tokamak. The large ITB is the largest one, the fishbone ITB is the strongest one and the LLM ITB is the widest one in three ITBs, where the ‘large’, ‘strong’ and ‘wide’ qualifications correspond to ITB position ρITB, the normalized temperature gradient R/LT, and its width W/a. Therefore, the large ITB position may be obtained if the IKMs are effectively controlled in a tokamak.

Simulation modelling of material handling using AGV

Modern production systems are mainly characterized by, among others, the use of automated transport systems. One of the components of such transport systems are automated guided vehicles (AGV). These vehicles are primarily used in the material handling due to their greater efficiency, flexibility and lower operating costs. The main aim of the article is to present the possibility of using simulation modelling in the analysis of internal transport operations using automated guided vehicles.