Power Exhaust Research Articles

Towards Integrated Target–SOL–Core Plasma Simulations for Fusion Devices with Liquid Metal Targets

Self-healing liquid metal divertors (LMDs) based on the Capillary Porous Structure (CPS) concept are currently being considered among the possible solutions to the power exhaust problem in future fusion reactors. Indeed, the passive replenishment of the plasma-facing surface by capillary forces and the self-shielding of the target via vapor emission can potentially improve the divertor lifetime and its resilience to transient loads. On the other hand, the LMD target erosion can be significant due to evaporation and thermal sputtering, on top of physical sputtering, possibly leading to unacceptable core plasma dilution/power losses (for a low-Z/high-Z metal such as Li and Sn, respectively). For this reason, it is necessary to assess whether an LMD is compatible with an European DEMO (EU-DEMO) plasma scenario. This requires a self-consistent model of the impurity emission from the target, the plasma in both the scrape-off layer (SOL) and the core regions and the transport of impurities therein. In this paper, an an integrated modelling approach is proposed, which is based on SOLPS-ITER and includes its coupling with a target erosion model written in FreeFem++ and a core plasma model (ASTRA/STRAHL). An application of the coupled SOL-target model to simulate experiments performed in the Magnum-PSI linear plasma device with a CPS target filled with Li is also included to provide a first demonstration of the capabilities of the approach. Results are promising, being in good agreement (within a few degrees) with the measured target temperature distribution. In perspective, the modelling framework presented here will be applied to the EU-DEMO with an Sn divertor.

Combustion characteristics and performance of a Wankel engine for unmanned aerial vehicles at various altitudes

This study investigates the effects of altitude on the combustion, emissions, and performance of a Wankel engine for unmanned aerial vehicles (UAVs). The main motivation behind the presented study is to contribute to the Wankel engine designs used as a power source in UAVs by revealing the operating conditions at various altitudes. For these purposes, a gasoline fueled Wankel engine was simulated at sea level conditions for different equivalence ratios and results were validated with their experimental counterparts. Then, CFD simulations were carried out at various altitudes (6000 ft, 10,000 ft, and 15,000 ft). The simulation results show that decreasing ambient air temperature, and pressure at higher altitudes reduces the fresh charge density, hence combustion efficiency and heat release rate (HRR). As a result, the performance characteristics such as the indicated mean effective pressure (IMEP), the indicated torque, and indicated power decrease and exhaust emissions increase. For 6000 rpm, IMEP decreases by 39.11%, 53.79%, and 69.22%, and the indicated power reduces by 35.51%, 52.47%, and 65.05% at the altitudes of 6000 ft, 10,000 ft, and 15,000 ft, respectively, compared to those obtained at the sea level conditions. As for exhaust emissions, CO and CO2 are lowest at sea level conditions and increase with altitude.

Performance characteristics and exhaust emissions of a single-cylinder diesel engine for different fuels: Experimental investigation and artificial intelligence network

In the current work, as the first phase, the main emphasis deals with the experimental study of the performance characteristics (effective power Peff and exhaust gas temperature Texh) and exhaust emissions (including CO, CO2, HC, and NOx) of a 4-stroke single-cylinder diesel (SCD) engine. The data are extracted from the engine tested for two inlet air temperatures (Tair), and three coolant temperatures (Tcoolant) at five different speeds (nm). To make the investigations even more comprehensive, all the tests are repeated for three different fuels including diesel (D100), diesel–kerosene blend (D95K5), and diesel–water blend (D90W10). In the second phase, an artificial intelligence network (AIN) is trained for expanding the outputs of the experiments. Analyzing the experiments’ outputs revealed that increasing Tair leads to three significant improvements including: reduction of emissions, shortening the ignition delay, and prevention of the quenching phenomenon. This is while, Tcoolant has a slight effect. Also, results illustrated that the superiority of D90W10 over the two other investigated fuels in the improvement of engine performance and exhaust emissions. So that, almost 1.67% and 0.97% more power is available on average using by D90W10 blend compared to the D100 fuel and D95K5 blend, respectively. The findings of the AIN showed that the developed model is capable to estimate the engine performance and diesel exhaust emissions (DEE) with a correlation coefficient of 0.99921, 0.99952, 0.93959, 0.96980, 0.95826, and 0.99746 for Peff, Texh, CO, CO2, HC, and NOx, respectively.

Preliminary Electromagnetic and Structural Analyses of the Conductors and Clamps of the DTT Current Feeders

The Divertor Tokamak Test facility (DTT) is being constructed in the Research Centre of ENEA Frascati. This nuclear fusion device is devoted to tackle the power exhaust issue in the view of future fusion power plant. The conceptual design and the performances of the DTT superconducting magnet feeders, with NbTi cables, are evaluated based on coupled electromagnetic and structural analyses. We here present a preliminary structural assessment of the feeder clamps. We have considered the self-field condition and the higher force per unit length on feeder paths as evaluated from a 3D EM simulation. The stress state is evaluated by means of a 2D model with plane stress with thickness formulation. Further, the bolt dimension and class, together with the distance between two clamps, is provided in both self-field and maximum force per unit length conditions.

Development of compact tokamak fusion reactor use cases to inform future transport studies

The OMFIT STEP (Meneghini et al., Nucl. Fusion, vol. 10, 2020, p. 1088) workflow has been used to develop inductive and steady-state H-mode core plasma scenario use cases for a $B_0 = 8 \, {\rm T}$ , $R_0 = 4 \, {\rm m}$ machine to help guide and inform future higher-fidelity studies of core transport and confinement in compact tokamak reactors. Both use cases are designed to produce 200 MW or more of net electric power in an up-down symmetric plasma with minor radius $a = 1.4 \, {\rm m}$ , elongation $\kappa = 2.0$ , triangularity $\delta = 0.5$ and effective charge $Z_{{\rm eff}} \simeq 2$ . Additional considerations based on the need for compatibility of the core with reactor-relevant power exhaust solutions and external actuators were used to guide and constrain the use case development. An extensive characterization of core transport in both scenarios is presented, the most important feature of which is the extreme sensitivity of the results to the quantitative stiffness level of the transport model used as well as the predicted critical gradients. This sensitivity is shown to arise from different levels of transport stiffness exhibited by the models, combined with the gyroBohm-normalized fluxes of the predictions being an order of magnitude larger than other H-mode plasmas. Additionally, it is shown that although heating in both plasmas is predominantly to the electrons and collisionality is low, the plasmas remain sufficiently well coupled for the ions to carry a significant fraction of the thermal transport. As neoclassical transport is negligible in these conditions, this situation inherently requires long-wavelength ion gyroradius-scale turbulence to be the dominant transport mechanism in both plasmas. These results are combined with other basic considerations to propose a simple heuristic model of transport in reactor-relevant plasmas, along with simple metrics to quantify coupling and core transport properties across burning and non-burning plasmas.

The development of a zero-dimensional collisional-radiative model for interpreting plasma emission in low temperature divertor plasmas in tokamaks

Collisional-radiative models are commonly used to analyse atomic and molecular processes in low temperature plasmas by determining the distribution functions of excited states as functions of various plasma parameters. This paper outlines the improvements to a zero-dimensional collisional-radiative model, developed at Keio University, for purposes relevant to the analysis of emission measurements in low temperature hydrogen plasmas. The extension of this 0D model centres on the inclusion of additional molecular species and reactions, a calculation of emission intensity in order to directly compare with experimental work, and the addition of a simple wall model to allow for a deeper understanding of recycling of atoms and molecules in low temperature plasmas close to plasma facing components in fusion machines. Results from the improved model are then compared with both an existing CR model for benchmarking and experimental emission spectroscopy data from an inductively-coupled plasma device at the University of Liverpool. These results show how the developments to the model have increased the relevance to experimental plasmas, such as those in the power exhaust regions of fusion machines, with the ratio of the Hβ/Hα line intensities outputted from the improved CR model mirroring more closely the emission measured experimentally in the ICP device.

Closed corner divertor with B × ∇B away from the divertor: a promising divertor scenario for tokamak power exhaust

A major challenge facing the steady-state operation of tokamak fusion reactors is to develop a viable divertor solution with order-of-magnitude increase in power handling capability as compared with present experience. A recently developed divertor concept for this end has been tested recently on EAST tokamak through combining the effects of a closed divertor corner and E × B drifts. The E × B drifts in the divertor move particles towards the outer divertor corner area in the scrape-off layer for B × ∇B directed away from the divertor, which can significantly enhance the particle concentration there, facilitating divertor detachment. In recent EAST experiments, the effects have been demonstrated where the lowest electron temperature at the divertor plate is obtained with strike point located close to the corner in the horizontal target and with B × ∇B away from the divertor. These experimental results are in reasonable agreement with SOLPS-ITER simulations including drift effects, suggesting that the new divertor concept potentially provides a promising divertor solution for long-pulse operations of future tokamak fusion reactors with much higher power fluxes.

Analysis and expansion of the quasi-continuous exhaust (QCE) regime in ASDEX Upgrade

The quasi-continuous exhaust (QCE) regime, formerly known as either type-II ELM or small ELM regime is studied in ASDEX Upgrade. The regime is a natural type-I ELM-free H-mode. The operational space of QCE discharges in ASDEX Upgrade with respect to their separatrix conditions and their power exhaust capabilities are presented. A significant broadening of the power fall-off length is observed, correlating to an increased separatrix density and pressure. Moreover, the possible reactor relevance of this regime is demonstrated by expanding the operational space to low edge safety factor and demonstrating the benign tungsten impurity behaviour. A discharge without any type-I ELM from start to end reaching a partially detached divertor at high normalised energy confinement time is presented.

Recent progress of plasma exhaust concepts and divertor designs for tokamak DEMO reactors

The power exhaust concept and an appropriate divertor design are common critical issues for tokamak DEMO design activities which have been carried out in Europe, Japan, China, Korea and the USA. Conventional divertor concepts and power exhaust studies for recent DEMO designs (Pfusion = 1 – 2 GW, Rp = 7 – 9 m) are reviewed from the viewpoints of the plasma physics issues and the divertor engineering design. Radiative cooling is a common approach for the power fusion scenario. Requirements on the main plasma radiation fraction (fradmain = Pradmain/Pheat) and the plasma performance constrain the divertor design concept. Different challenges contribute to optimizing the future DEMO designs: for example, (i) increasing the main plasma radiation fraction for ITER-level Psep/Rp designs and simplifying the divertor geometry, and (ii) extending ITER divertor geometry with increasing divertor radiation (Praddiv) for larger Psep/Rp ≥ 25MWm−1 designs. Power exhaust simulations with large Psep = 150 – 300 MW have been performed using integrated divertor codes considering an ITER-based divertor geometry with longer leg length (1.6 – 1.7 m), as in a common baseline design. Geometry effects (ITER like geometry or more open one without baffle) on the plasma detachment profile and the required divertor radiation fraction (fraddiv = Praddiv/Psep) were key aspects of these studies. All simulations showed that the divertor plasma detachment were extended widely across the target plate with a reduction in the peak heat load of qtarget ≤ 10 MWm−2 for the large fraddiv = 0.7 – 0.8, while the peak qtarget location and value were noticeably different in the partially detached divertor. Simulation results also demonstrated that radial diffusion coefficients of the heat and particle fluxes were critical parameters for DEMO divertor design, and that effects of plasma drifts on outboard-enhanced asymmetry of the heat flux, suggested the need for longer divertor leg to ensure the existence of a detached divertor operation with qtarget ≤ 10 MWm−2.Integrated design of the water cooled divertor target, cassette body (CB) and cooling pipe routing has been developed for each DEMO concept, based on the ITER-like tungsten monoblock (W-MB) with Cu-alloy cooling pipes. Engineering design adequate under higher neutron irradiation condition was required. Therefore, inlet coolant temperature (Tcool) was increased. In current designs, it still shows a large potential variation between 70 °C and 200 °C. The influence of thermal softening on the Cu-alloy (CuCrZr) pipe was fostered near the strike-point when the high qtarget of ∼10 MWm−2 was studied. Improved technologies for high heat flux components based on the ITER W-MB unit have been developed for EU-DEMO. Different coolant conditions (low- and high-Tcool) were provided for Cu-alloy and reduced activation ferritic martensitic (RAFM) steel heat sink units, respectively. The high-Tcool coolant was also considered for the CB and supporting structures. Appropriate conditions for the high-Tcool coolant, i.e. 180 °C/ 5 MPa (EU-DEMO) and 290 °C/ 15 MPa (JA-DEMO, CFETR and K-DEMO), will be determined in the future optimizations of the divertor and DEMO design.

Aminoprocalcitonin protects against hippocampal neuronal death via preserving oxidative phosphorylation in refractory status epilepticus

Refractory status epilepticus (RSE) is a neurological emergency where sustaining seizure causes severe neuronal death. Currently, there is no available neuroprotectant effective in RSE. Aminoprocalcitonin (NPCT) is a conserved peptide cleaved from procalcitonin, but its distribution and function in the brain remain enigmatic. Survival of neurons relies on sufficient energy supply. Recently, we found that NPCT was extensively distributed in the brain and had potent modulations on neuronal oxidative phosphorylation (OXPHOS), suggesting that NPCT might be involved in neuronal death by regulating energy status. In the present study, combining biochemical and histological methods, high-throughput RNA-sequence, Seahorse XFe analyser, an array of mitochondria function assays, and behavior-electroencephalogram (EEG) monitoring, we investigated the roles and translational values of NPCT in neuronal death after RSE. We found that NPCT was extensively distributed throughout gray matters in rat brain while RSE triggered NPCT overexpression in hippocampal CA3 pyramidal neurons. High-throughput RNA-sequence demonstrated that the influences of NPCT on primary hippocampal neurons were enriched in OXPHOS. Further function assays verified that NPCT facilitated ATP production, enhanced the activities of mitochondrial respiratory chain complexes I, IV, V, and increased neuronal maximal respiration capacity. NPCT exerted multiple neurotrophic effects including facilitating synaptogenesis, neuritogenesis, spinogenesis, and suppression of caspase-3. A polyclonal NPCT immunoneutralization antibody was developed to antagonize NPCT. In the in vitro 0-Mg2+ seizure model, immunoneutralization of NPCT caused more neuronal death, while exogenous NPCT supplementation, though did not reverse death outcomes, preserved mitochondrial membrane potential. In rat RSE model, both peripheral and intracerebroventricular immunoneutralization of NPCT exacerbated hippocampal neuronal death and peripheral immunoneutralization increased mortality. Intracerebroventricular immunoneutralization of NPCT further led to more serious hippocampal ATP depletion, and significant EEG power exhaustion. We conclude that NPCT is a neuropeptide regulating neuronal OXPHOS. During RSE, NPCT was overexpressed to protect hippocampal neuronal survival via facilitating energy supply.

Demonstration of Power Exhaust Control by Impurity Seeding in the Island Divertor at Wendelstein 7-X

Demonstration of Power Exhaust Control by Impurity Seeding in the Island Divertor at Wendelstein 7-X

Thermodynamic modeling and control of hybrid solar-fossil fuel power generation and storage system

Hybrid solar-fossil fuel power generation and storage (HSFF-PGS) is an innovative technology characterized by renewable and conventional hybrid energy utilization and thermochemical energy storage. The HSFF-PGS system has prominent advantages in improving the solar energy grade and storing thermal energy with a high energy density. However, investigations on its dynamic characteristics and real-time control are inadequate, which hinders the development of the system’s automation level to some degree. To deal with this issue, first, in this paper a dynamic model that includes the thermal inertia and reaction kinetics is constructed. Simulations under the nominal conditions show that the net solar utilization efficiency and energy savings ratio can reach 48.28% and 34.5%. Second, the design/off-design working condition properties are presented and the dynamic characteristics, such as nonlinearity and coupling, are explored to identify the control difficulties. The calculation results show that the relative gain array value ranges from 1 to 5 and the Vinnicombe gap is greater than 0.4 under most working conditions. Based on the dynamic analysis results, distributed active disturbance rejection control (ADRC) strategies for power generation and exhaust temperature regulation are developed. Then, the control performances of the proposed distributed ADRC and the conventional proportional integral derivative (PID) control are compared under nominal working conditions and typical-day scenarios. The control performance indexes are improved by 66.7% on average. Thus, the distributed ADRC is confirmed to be a better control method and has a good potential for dynamic operation of the HFSS-PGS system.

Conceptual design of the DTT ECRH quasi-optical transmission line

The Divertor Tokamak Test (DTT) facility is being realised in Frascati, Italy for the study of the power exhaust issues in view of DEMO tokamak. A multi-MW Electron Cyclotron Resonance Heating (ECRH) system is foreseen with a first set of 16 gyrotrons at 1 MW and 170 GHz available for the first stage of operation; additional 16 gyrotrons with power from 1 MW to 1.2 MW are foreseen in a later stage for a total of up to 33.6 MW of ECRH at plasma. ECRH system itself is part of the 45 MW of external additional heating coupled to the plasma, provided also by Ion Cyclotron Resonance Heating and Neutral Beam Injection. The Transmission Line (TL) is fully quasi-optical, between 84 m and 138 m long and will transfer power up to 1.5 MW per beam from the building hosting the ECRH sources to the Torus Hall. The main section runs in a straight elevated corridor at a few meters above the ground level. In order to have low power losses and a simpler and manageable system, the long TL run is made by four quasi-optical Multi-Beam (MB) lines each transmitting 8 beams via shared mirrors, similar to the W7-X Stellarator TL. The system is thus organised in “clusters” each one made of the 8 gyrotron sources and the respective transmission line and launchers. Avoidance of losses in air and microwave leaks is assured by a vacuum enclosure of the whole line with the use of metallic gaskets. Single-Beam (SB) transmission lines are foreseen at the beginning and end of the MB line, to cover the distance from the gyrotron to a beam-combining mirror and from a splitting mirror to the launcher. The optical design has to cope with space constraints in the building and inherent conversion losses at the reflection on metallic mirrors, whose number was minimised. First evaluations with the electromagnetic modeling tool GRASP and first concepts for the MB mirror cooling are reported.

Improved deoxygenation beads for trickle bed-based microbial fuel cells to increase isopropanol and styrene-containing exhaust gas removal efficiency and power production

This study is the first to use a trickle-bed microbial fuel cell (TB-MFC) to treat both hydrophilic (isopropyl alcohol) and hydrophobic (styrene) pollutants. During the operation of the TB-MFC, the microorganisms continue to convert pollutants into electrons, improving the removal of hydrophilic and hydrophobic pollutants, and generating electricity. To enhance the growth of electricity-generating bacteria, a novel deoxygenated packing material (DPM) that removes oxygen from the exhaust gas was applied to the TB-MFC. The TB-MFC reached maximum pollutant removal and power generation at a total carbon concentration of 2.20 g/m3, an empty bed residence time of 60 s and a concentration ratio of 1: 1 of isopropanol and styrene. The mean elimination capacity of isopropanol and styrene were 81.5 ± 0.20 g/m3/h and 54.2 ± 0.26 g/m3/h, respectively, and the maximum voltage outputs and power density were 450 mV and 426 mW/m3. A microbial community analysis revealed that the electricity-generating bacteria were mostly Clostridium, Aeromonas, Acinetobacter and Kosakonia. Most of the isopropanol-degrading bacteria (Xanthobacter, Beijerinckia) and styrene-degrading bacteria (Chryseobacterium, Cloacibacterium) were in the TB-MFC. The findings indicate that TB-MFC is capable of generating electricity and treating both hydrophilic and hydrophobic pollutants simultaneously. The improved DPM can be used in the TB-MFC to reduce the concentration of oxygen in industrial emissions and accelerate the growth of electricity-generating bacteria, with the goal of achieving high pollutant removal and electricity generation.

Compact Radiative Divertor Experiments at ASDEX Upgrade and Their Consequences for a Reactor.

We present a novel concept to tackle the power exhaust challenge of a magnetically confined fusion plasma. It relies on the prior establishment of an X-point radiator that dissipates a large fraction of the exhaust power before it reaches the divertor targets. Despite the spatial proximity of the magnetic X point to the confinement region, this singularity is far away from the hot fusion plasma in magnetic coordinates and therefore allows the coexistence of a cold and dense plasma with a high potential to radiate. In the compact radiative divertor (CRD) the target plates are placed close to this magnetic X point. We here report on high performance experiments in the ASDEX Upgrade tokamak that indicate the feasibility of this concept. Despite the shallow (projected) field line incidence angles of the order of θ_{⊥}=0.2°, no hot spots were observed on the target surface monitored by an IR camera, even at a maximum heating power of P_{heat}=15 MW. And even with the X point located exactly on the target surface and without density or impurity feedback control, the discharge remains stable, the confinement good (H_{98,y2}=1), hot spots absent, and the divertor in a detached state. In addition to its technical simplicity, the CRD scales beneficially to reactor-scale plasmas that would benefit from an increased volume of the confined plasma, more space for breeding blankets, smaller poloidal field coil currents, and-potentially-an increased vertical stability.

Addressing the carbon and nitrogen impurity screening issue on HL-2M snowflake minus and conventional divertor using SOLPS

This paper demonstrates the benefits of the HL-2M SF (snowflake) minus divertor on power exhaust and impurity screening compared with the LSN (lower single null) conventional divertor using SOLPS 5.0 code package. In order to estimate the effectiveness of the impurity screening capability in the HL-2M SF minus divertor, we analyze the impurity transport behavior with intrinsic carbon impurities (P sol = 4 MW) and external injected nitrogen impurities (P sol = 6 MW) in the LSN and SF minus divertors. The simulation results reveal that an input power of and electron density of on the outer mid-plane can induce a nearly 80% pressure drop in the SOL (scrape-off layer) flux tube, representing the transition of the detachment regime in the SF minus divertor. For the higher power operation with P sol = 6 MW, a nitrogen gas puffing rate at is sufficient to exhaust excessive energy and facilitate detachment in the SF minus divertor. However, a higher gas puffing rate is necessary for the LSN divertor, indicating an improved power exhaust capability in the SF minus divertor. Furthermore, the maximum effective charge () in the SF minus divertor SOL region is nearly 1.45 versus 3.5 in the LSN case with P sol = 4 MW. The maximum in the SF minus divertor SOL region is below 2.4, versus 5.5 in the LSN case with the same impurity gas puffing rate when . Moreover, the impurity ions accumulate in the divertor region in the SF minus case, which demonstrates the effectiveness of the impurity screening capability in the HL-2M SF minus divertor. We find that the higher ionized state impurity ions contribute to the increase of and determine the impurity level upstream. On the one hand, the detached divertor regime has the benefit of suppressing the impurity particles ionizing to a higher ionized state. On the other hand, the ionization rate distribution and the poloidal velocity influenced by the friction and thermal forces determine the impurity transport behavior.

Divertor optimisation and power handling in spherical tokamak reactors

A key aspect in the design of a spherical tokamak reactor is the optimisation of the plasma equilibrium, together with a compatible divertor configuration, and the corresponding poloidal field system. This is a complex multi-disciplinary problem, integrating plasma physics and engineering in order to satisfy a multitude of often conflicting requirements and constraints. The equilibrium design process employed in this work takes into account the reference plasma operating scenario, the power exhaust solution, and the engineering limits.Managing the heat exhaust proves to be one of the most challenging issues in a compact device such as the UKAEA STEP reactor. With a smaller major radius, the available target area over which the scrape-off layer heat load must be deposited is relatively small as compared to conventional aspect ratio devices. Consequently, alternative and advanced divertor concepts need to be considered, having significant implications for the whole reactor design. Here we address the inner divertor power handling challenges. With very limited inboard space, and the small radius of the inner strike point, the associated heat loads are likely to exceed the power handling capacity of standard divertors (SD). An alternative divertor configuration approaching an X-divertor (XD), created by inducing a secondary X-point near the inner strike point, is compared with an SD configuration optimised for the maximal connection length and maximal poloidal flux expansion. The inner X-divertor, simultaneously achieving strong poloidal flux expansion, increased connection length and higher divertor volume, proved to be advantageous in reducing target heat loads and favouring detachment. Amongst a number of viable exhaust solutions considered, the inner-X divertor is indeed emerging as a promising candidate.

Design of Quadruple Offset Butterfly Valve Used in Power Plants

The elliptical disc is a specific characteristic of a triple offset butterfly valve (TOBV), but the structure of the elliptical disc leads to a non-uniform distribution of contact at the closing position with non-uniform wear. On the other hand, the continuous processing of elliptical sections to finish the entire disc contour is expensive compared to the processing of a circular section. In the present study, to improve the above disadvantages of an elliptical disc, an elliptic cone function was established to describe the quadruple butterfly valve (QOBV) disc shape, which has a circular section disc. In addition, some designs of a fixed thickness (7 mm) laminated seal for good sealing were proved. Sealing performance simulations were carried out using the thermal–structural coupling analysis. The best design of the QOBV showed that the maximum contact pressure was 37.2% lower than the TOBV using the seven-way laminated seal layers (thickness of A240–316 stainless and graphite was 1.3 mm and 0.6 mm, respectively). Compared to TOBV, the QOBV disc operation during the opening and closing process was faster and smoother. The disc can be applied widely to various industrial fields, engine exhaust systems, and turbine and power plants under severe environments.

Magnetic control of DTT alternative plasma configurations

One of the main challenges concerning next generation tokamaks (such as DEMO) will be the development of a heat and power exhaust system able to withstand the large loads expected in the divertor region. A dedicated Divertor Tokamak Test (DTT) facility has been proposed in the EUROfusion Roadmap, with the aim of testing unconventional solutions, such as advanced magnetic configurations and liquid metal divertors. Magnetic control of alternative plasma configurations, such as the X-Divertor, will play a key role in the solution of the heat exhaust and yet can be a challenging point, due to increased sensitivity introduced by secondary x-points. To overcome the complications introduced by secondary x-points in advanced plasma shapes, magnetic control in DTT is achieved by resolving to the eXtreme Shape Controller, in order to control both the plasma shape and the secondary x-point position.

Analysis of edge transport in L-mode negative triangularity TCV discharges

One of the major problems for future tokamak devices are ELMs (Edge Localized Modes) as they can lead to large, uncontrolled heat fluxes at the machine targets. For this reason, different techniques and alternative magnetic configurations are under study to mitigate or avoid these phenomena. One of the most promising among these studies is the Negative Triangularity (NT) configuration, which exhibits a global confinement comparable with H-Mode operation and, staying in L-mode, could enable an easier power exhaust dissipation due to a possible bigger heat flux decay length with respect to the conventional Positive triangularity (PT) H-mode. In this work, the fluid code SOLEDGE2D-EIRENE is used to study edge transport. Studies are made on discharges performed in the TCV device (Tokamak à configuration variable), which can create a variety of different plasma geometries thanks to 16 independently powered poloidal field coils and its open vacuum vessel. In order to understand if and how power and particle exhaust in NT differs with respect to those of the PT shape, four discharges in single null magnetic divertor configuration with fixed lower triangularity (δbot=+0.5) but with different upper triangularity (from δup=-0.28 to δup=+0.45) have been modelled. All of them are ohmically heated, L-mode deuterium plasmas, and in the high recycling regime. Moreover, these discharges were previously used in [4] to measure the heat flux decay length by IRT (Infrared Thermography), allowing us to make comparisons with modelling results.