Power Exhaust Research Articles

Divertor of the European DEMO: Engineering and technologies for power exhaust

In a power plant scale fusion reactor, a huge amount of thermal power produced by the fusion reaction and external heating must be exhausted through the narrow area of the divertor targets. The targets must withstand the intense bombardment of the diverted particles where high heat fluxes are generated and erosion takes place on the surface. A considerable amount of volumetric nuclear heating power must also be exhausted. To cope with such an unprecedented power exhaust challenge, a highly efficient cooling capacity is required. Furthermore, the divertor must fulfill other critical functions such as nuclear shielding and channeling (and compression) of exhaust gas for pumping. Assuring the structural integrity of the neutron-irradiated (thus embrittled) components is a crucial prerequisite for a reliable operation over the lifetime. Safety, maintainability, availability, waste and costs are another points of consideration.In late 2020, the Pre-Conceptual Design activities to develop the divertor of the European demonstration fusion reactor were officially concluded. On this occasion, the baseline design and the key technology options were identified and verified by the project team (EUROfusion Work Package Divertor) based on seven years of R&D efforts and endorsed by Gate Review Panel.In this paper, an overview of the load specifications, brief descriptions of the design and the highlights of the technology R&D work are presented together with the further work still needed.

DSMC simulations of neutral gas flow in the DTT particle exhaust system

Divertor Tokamak Test Facility (DTT) is a new European superconducting tokamak, currently under final design, addressed to investigate alternative power exhaust solutions for DEMO. Although the divertor system is not finalized yet, the machine and port geometry set limitations on the divertor pumping system operational space. A numerical study of neutral gas dynamics in the divertor region is performed based on the DSMC method by applying the DIVGAS code. The study includes both single-null (SN) and double-null (DN) divertor configurations. For both configurations, the SolEdge2D–EIRENE plasma simulations have been performed for a deuterium plasma with neon seeding and the extracted information about the neutral particles on the predefined interfaces is imposed as incoming boundary conditions for DIVGAS simulations. In the SN case, two plasma puffing scenarios and three candidate pumping port arrangements have been considered. The divertor dome influence on the pumped fluxes can reach 50%. An increase of the capture coefficient six times leads to a decrease in the pressure at the pumping openings by a factor of about 4.5–7. The influence of the size of the lower vertical opening has been studied showing that the enlarged vertical port may establish as the main pumping opening. In the DN case, when the pumping is performed from both lower and upper divertor the overall pumped fluxes at the upper divertor are always higher than the corresponding ones for the lower divertor by a factor of 2–2.5, mainly due to the difference in the pumping areas. In both SN and DN cases, the neutrals outflux toward the X-point dominates the particle transport in the private flux region. The operational space provided by this first assessment is relatively stable against modified classical divertor geometries and allows a more thorough assessment of the pumping technology of the DTT fusion device in the future.

Experimental Studies and Theoretical Modelling of Diesel Engine Running on Biodiesels from South African Sunflower and Canola Oils

Abstract The attributes of cost-effectiveness, reliability, consistency and better understanding, have made researchers prefer studying engine characteristics of IC engines fuelled with alternative fuels/diesel blends with computer simulation compared to conventional experimental study. For the first time, the study attempted to simulate combustion, performance, and emission characteristics of biodiesels from Canola and Sunflower oil domiciled in South Africa. The properties of biodiesel vary from one region to another depending on the local properties of the feedstock used for its production. In this study, a computer model-based C++ was used to evaluate the performance characteristics of biodiesel fuels produced from local South African sunflower and canola oil feedstocks. The developed model was validated using experimental results. The performance characteristics of biodiesel and biodiesel-diesel blends from these oils were tested in a Mercedes Benz OM 364A turbocharged four-stroke, four-cylinder direct ignition industrial diesel engine. Results show similar combustion characteristics for all the tested samples. Diesel shows a higher brake power and higher exhaust gas temperature than all the tested fuel samples. The brake thermal efficiency increases with the amount of biodiesel in the biodiesel-diesel blends. Biodiesel and its diesel blends show higher specific fuel consumption than diesel. In terms of emissions, nitrogen oxide emission was higher for biodiesel and its blends with diesel compared with diesel while smoke emission from biodiesel and its diesel blends was lower compared with diesel.

Modeling and Predicting Heavy-Duty Vehicle Engine-Out and Tailpipe Nitrogen Oxide (NO x ) Emissions Using Deep Learning.

As emissions regulations for transportation become stricter, it is increasingly important to develop accurate nitrogen oxide (NOx) emissions models for heavy-duty vehicles. However, estimation of transient NOx emissions using physics-based models is challenging due to its highly dynamic nature, which arises from the complex interactions between power demand, engine operation, and exhaust aftertreatment efficiency. As an alternative to physics-based models, a multi-dimensional data-driven approach is proposed as a framework to estimate NOx emissions across an extensive set of representative engine and exhaust aftertreatment system operating conditions. This paper employs Deep Neural Networks (DNN) to develop two models, an engine-out NOx and a tailpipe NOx model, to predict heavy-duty vehicle NOx emissions. The DNN models were developed using variables that are available from On-board Diagnostics from two datasets, an engine dynamometer and a chassis dynamometer dataset. Results from trained DNN models using the engine dynamometer dataset showed that the proposed approach can predict NOx emissions with high accuracy, where R2 scores are higher than 0.99 for both engine-out and tailpipe NOx models on cold/hot Federal Test Procedure (FTP) and Ramped Mode Cycle (RMC) data. Similarly, the engine-out and tailpipe NOx models using the chassis dynamometer dataset achieved R2 scores of 0.97 and 0.93, respectively. All models developed in this study have a mean absolute error percentage of approximately 1% relative to maximum NOx in the datasets, which is comparable to that of physical NOx emissions measurement analyzers. The input feature importance studies conducted in this work indicate that high accuracy DNN models (R2 = 0.92–0.95) could be developed by utilizing minimal significant engine and aftertreatment inputs. This study also demonstrates that DNN NOx emissions models can be very effective tools for fault detection in Selective Catalytic Reduction (SCR) systems.

Optimizing Composite Materials as Cathodic Catalysts for Microbial Fuel Cells to Improve Exhaust Isopropanol Removal and Power Generation

Optimizing Composite Materials as Cathodic Catalysts for Microbial Fuel Cells to Improve Exhaust Isopropanol Removal and Power Generation

Impact of neutral gas puffing on the divertor power exhaust and particle control in GAMMA 10/PDX by the LINDA‐KNMC code

AbstractThis paper numerically investigates the impact of neutral gas puffing on the divertor power exhaust and particle control in GAMMA 10/PDX applying the plasma fluid code LINDA and the kinetic neutral code KMNC. The LINDA code is applied to GAMMA 10/PDX plasmas for understanding the physics of detachment and energy loss processes. The LINDA code is coupled with a Monte–Carlo neutral code for describing the hydrogen (H and H2) neutral particles. The plasma ion temperature (Ti) is reduced towards the target plate with the increment of H2 Gas‐Puff rate. This paper also numerically investigates the impact of recombination processes on the detached formation. The ionization, charge–exchange, and recombination of H have been included as a particle and an energy sink and source parts of the fluid equations. The reaction rate coefficient of molecular activated recombination (MAR) has been recently introduced in the LINDA code. In this paper, we study numerically the effect of MAR on the detached plasma. The MAR plays a dominant role in making the detached plasma. The simulation clarified that H neutral particles injection can effectively generate the detached plasma by enhancing the plasma‐neutral collisions processes.

Role of soluble nano-catalyst and blends for improved combustion performance and reduced greenhouse gas emissions in internal combustion engines

Biofuels were getting an enormous attention to be used as fuel for diesel engines. This paper examines the effect of addition of nanoparticles in biofuel on diesel engines. The biofuel used for conducting tests was canola oil. Corn oil was mixed with titanium dioxide (TiO2) at different proportions as 25 ppm, 50 ppm, 75 ppm and 100 ppm. These nanoparticles mixed with biofuel and diesel. The nanoparticles were dispersed with biodiesel at the concentration of B10T25 (10% cornoil + 90% diesel + TiO225), B10T50, B10T75, B10T100, B20T25, B20T50, B20T75, and B20T100 and plain biodiesel are B10 and B20. All tests were carried at different speeds 1800 rpm, 2000 rpm, 2200 rpm, 2400 rpm, 2600 rpm and 2800 rpm. Performance and emission characteristics were estimated for all fuel blends. Results were compared to each other to characterize the fuel blend quality. The addition of titania with biofuel increased the performance qualities such as brake thermal efficiency (BTE), exhaust gas temperature (EGT), Torque and Power. Further this combination reduced the Greenhouse gas emissions such as CO, CO2, and UHC. The specific fuel consumption (SFC) was also reduced and proved to be the better alternative to existing fossil fuel. However, the emission of NOx was increased.

NOMA resource allocation method in IoV based on prioritized DQN-DDPG network

To meet the demands of massive connections in the Internet-of-vehicle communications, non-orthogonal multiple access (NOMA) is utilized in the local wireless networks. In NOMA technique, various optimization methods have been proposed to provide optimal resource allocation, but they are limited by computational complexity. Recently, the deep reinforcement learning network is utilized for resource optimization in NOMA system, where a uniform sampled experience replay algorithm is used to reduce the correlation between samples. However, the uniform sampling ignores the importance of sample. To this point, this paper proposes a joint prioritized DQN user grouping and DDPG power allocation algorithm to maximize the system sum rate. At the user grouping stage, a prioritized sampling method based on TD-error (temporal-difference error) is proposed. At the power allocation stage, to deal with the problem that DQN cannot process continuous tasks and needs to quantify power into discrete form, a DDPG network is utilized. Simulation results show that the proposed algorithm with prioritized sampling can increase the learning rate and perform a more stable training process. Compared with the previous DQN algorithm, the proposed method improves the sum rate of the system by 2% and reaches 94% and 93% of the exhaustive search algorithm and optimal iterative power optimization algorithm, respectively. Although the sum rate is improved by only 2%, the computational complexity is reduced by 43% and 64% compared to the exhaustive search algorithm and the optimal iterative power optimization algorithm, respectively.

Development of an integrated core–edge scenario using the super H-mode

An optimized pedestal regime called the super-H (SH) mode is leveraged to couple a fusion relevant core plasma with a high density scrape-off layer appropriate for realistic reactor power exhaust solutions. Recent DIII-D experiments have expanded the operating space of the SH regime using advanced control algorithms and investigated optimization of impurity seeding, deuterium gas puffing, and 3D magnetic perturbations. Simultaneous real-time control of the pedestal density and radiated power with in-vessel coils and nitrogen seeding enable optimal coupled divertor and pedestal conditions. Four case studies are analysed with varied levels of radiated power in the divertor volume ranging from 0 (no seeding) to 8.5 MW radiated from carbon and nitrogen emission. Plasmas with a 4.5 MW radiated power target establish a radiative mantle, leading to divertor temperatures of ∼16 eV while maintaining SH-mode, and with only marginal impact on the pedestal and core performance. Increased levels of N2 seeding with a 7.5 MW radiated power target facilitate detachment onset and divertor temperatures <5 eV, with no degradation in stored energy and the operational point remaining inside the SH-mode channel for . Finally, a 8.5 MW radiated power target leads to partial detachment, which is so far associated with the loss of access to SH-mode pedestal conditions.

Power exhaust concepts and divertor designs for Japanese and European DEMO fusion reactors

Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan–Europe broader approach DEMO design activity (BA DDA). Common critical issues are the large power exhaust and its fraction in the main plasma and divertor by the radiative cooling (P rad tot/P heat ⩾ 0.8). Different exhaust concepts in the main plasma and divertor have been developed for Japanese (JA) and European (EU) DEMOs. JA proposed a conventional closed divertor geometry to challenge large P sep/R p handling of 30–35 MW m−1 in order to maintain the radiation fraction in the main plasma at the ITER-level (f rad main = P rad main/P heat ∼ 0.4) and higher plasma performance. EU challenged both increasing f rad main to ∼0.65 and handling the ITER-level P sep/R p in the open divertor geometry. Power exhaust simulations have been performed by SONIC (JA) and SOLPS5.1 (EU) with corresponding P sep = 250–300 MW and 150–200 MW, respectively. Both results showed that large divertor radiation fraction (P rad div/P sep ⩾ 0.8) was required to reduce both peak q target (⩽10 MW m−2) and T e,i div. In addition, the JA divertor performance with EU-reference P sep of 150 MW showed benefit of the closed geometry to reduce the peak q target and T e,i div near the separatrix, and to produce the partial detachment. Integrated designs of the water cooled divertor target, cassette and coolant pipe routing have been developed in both EU and JA, based on the tungsten (W) monoblock concept with Cu-alloy pipe. For year-long operation, DEMO-specific risks such as radiation embrittlement of Cu-interlayers and Cu-alloy cooling pipe were recognized, and both foresee higher water temperature (130 °C–200 °C) compared to that for ITER. At the same time, several improved technologies of high heat flux components have been developed in EU, and different heat sink design, i.e. Cu-alloy cooling pipes for targets and RAFM steel ones for the baffle, dome and cassette, was proposed in JA. The two approaches provide important case-studies of the DEMO divertor, and will significantly contribute to both DEMO designs.

Modeling and Integrated Optimization of Power Split and Exhaust Thermal Management on Diesel Hybrid Electric Vehicles

To simultaneously achieve high fuel efficiency and low emissions in a diesel hybrid electric vehicle (DHEV), it is necessary to optimize not only power split but also exhaust thermal management for emission aftertreatment systems. However, how to coordinate the power split and the exhaust thermal management to balance fuel economy improvement and emissions reduction remains a formidable challenge. In this paper, a hierarchical model predictive control (MPC) framework is proposed to coordinate the power split and the exhaust thermal management. The method consists of two parts: a fuel and thermal optimized controller (FTOC) combining the rule-based and the optimization-based methods for power split simultaneously considering fuel consumption and exhaust temperature, and a fuel post-injection thermal controller (FPTC) for exhaust thermal management with a separate fuel injection system added to the exhaust pipe. Additionally, preview information about the road grade is introduced to improve the power split by a fuel and thermal on slope forecast optimized controller (FTSFOC). Simulation results show that the hierarchical method (FTOC + FPTC) can reach the optimal exhaust temperature nearly 40 s earlier, and its total fuel consumption is also reduced by 8.9%, as compared to the sequential method under a world light test cycle (WLTC) driving cycle. Moreover, the total fuel consumption of the FTSFOC is reduced by 5.2%, as compared to the fuel and thermal on sensor-information optimized controller (FTSOC) working with real-time road grade information.

Performance Estimation of a Wireless Sensor Network with a Mobile Sink Moving in Different Trajectories at Different Velocities

Background: Throughout the past few years, numerous Medium Access Control (MAC) protocols, routing protocols, node deployment mechanisms and duty cycle variation schemes have been designed for achieving high throughput, low delay and jitter, and long network lifetime in Wireless Sensor Networks (WSNs). In a WSN with static sink, voluminous sensors transmit their sensed data to the sink node. The coordinators mutually present in the range of sensors and sink have to forward a number of packets, which cause rapid depletion of their battery. These coordinators become dead too early resulting in the breakage of the communication channel and formation of energy holes. However, to save energy with a static sink, the duty cycle should be short. A mobile sink is a better option than a static sink if the duty cycle is long, as it balances energy consumption among the sensors. It is well observed that the mobile sink is capable of acquiring homogeneous energy depletion leading to stretched lifetime enhancing network performance. Methods: The vital benefaction of this paper is to present a simulation-based analysis of the network performance with a mobile sink having different trajectories of path traversed at different velocities. The intent is to find out the most appropriate and efficient trajectory and a particular velocity for a specific WSN with 100 nodes. The terrain area of the network is 210×210 m2 with the communication range of 20 m. The routing, network and MAC protocols implemented are Ad hoc On-Demand Distance Vector (AODV), Internet Protocol version 4 (IPv4) and Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 respectively. This paper has evaluated and analyzed the influence of lawn mower, elliptical and circular trajectories of a mobile sink moving at different velocities of 0.5, 1 and 2 m/s. The optimum performance is achieved at the velocity of 2 m/s for a circular trajectory of the mobile sink. It is observed that performance has significantly varied with the variation of trajectories and velocities. The notion of precise utilization of sink mobility improves the performance than a static sink. It is equally important to determine the most effective mechanism to implement mobile sinks and to find out the most appropriate scheme out of them. Results: The attainment parameters just as total messages received, average end to end delay (seconds), jitter (seconds), throughput (bits per second), number of packets dropped, number of packets dropped due to channel access failure, residual battery (mAh) and network lifetime (hours) for different trajectories such as lawn mower, elliptical and circular at different speeds of 0.5, 1 and 2 m/s of the sink node are evaluated and compared. The simulation results present that the circular trajectory and the velocity of 2 m/s have provided optimum performance. Conclusion: The objective was to precisely analyze and evaluate the influence of different trajectories of a mobile sink moving at different velocities in a WSN of 100 nodes to determine the most effective and appropriate trajectory and velocity to optimize the attainments. The intent is to uniform the power exhaustion amidst the sensors. The purpose was to gain the attention of researchers of this field to significantly contribute to novel research.

Thermal-hydraulic modelling and analysis of ITER tungsten divertor monoblock

• A mathematical model has been developed to investigate the thermal-hydraulic performance of ITER tungsten divertor monoblock. • The model predicts the thermal response of the divertor structural materials and coolant tube. • The model accounts for the melting, vaporization, and solidification of the upper layer of the divertor facing plasma. • The model is verified against a previous calculation in the literature for DEMO divertor at an incident surface heat flux of 10 MW/m 2 . • The model is used to simulate the divertor materials response subjected to a VDE. The divertor is a fundamental component of fusion power plants, being primarily responsible for power exhaust and impurity removal via guided plasma exhaust. Due to its position and functions, the divertor has to sustain very high heat flux arising from the plasma (up to 20 MW/m 2 ), while experiencing an intense nuclear deposited power, which could jeopardize its structure and limit its lifetime. Therefore, attention has to be paid to the thermal–hydraulic design of its cooling system. In this work a mathematical model has been developed to investigate the steady state and transient thermal–hydraulic performance of ITER tungsten divertor monoblock. The model predicts the thermal response of the divertor structural materials and coolant tube. The coolant tube is divided into specified axial regions and the divertor plate is divided into specified radial zones, and then a two-dimensional heat conduction calculation is performed to predict the temperature distribution for both steady and transient states. A two-dimensional numerical finite difference technique is adapted in Cartesian coordinate system where the implicit scheme is used for transient calculation. The model also accounts for the melting, vaporization, and re-solidification of the upper layer of the divertor facing plasma. The selected heat transfer correlations cover all possible operating conditions of ITER under both normal and off-normal situations. The model is verified against a previous calculation in the literature for DEMO divertor at an incident surface heat flux of 10 MW/m 2 . The model is then used to predict the steady state thermal behaviour of the divertor under incident surface heat fluxes ranges from 2 to 20 MW/m 2 for a bare cooling tube and cooling tube with swirl-tape insertion. It calculates the maximum tube surface heat flux and the minimum critical heat flux ratio for all cases as well. The model is also used to simulate the divertor materials response subjected to high heat flux during a vertical displacement event (VDE) where 60 MJ/m 2 plasma energy is deposited over 500 ms.

High-performance ECRH at W7-X: experience and perspectives

The second operation phase of W7-X (OP1.2) showed the potential of exclusively electron cyclotron resonance heating (ECRH)-sustained plasma operations in stellarators. Employing multi-pass ECRH scenario in the second harmonic O-mode (O2-ECRH), stationary densities of up to 1.4 × 1020 m−3 could be achieved. This scenario also made stationary divertor detachment possible, which is a reactor-relevant scenario for power and particle exhaust. At high densities and with sufficiently high density gradients for an improved ion confinement, the coupling between the electrons and ions was strong enough to bring the ion temperature to values above 3 keV and to the neoclassical limit for some magnetic configurations, thus enabling to test the W7-X neoclassical optimization. The planned enhancement of the ECRH performance will enable to advance towards reactor-relevant beta values and to investigate their stability and confinement of fast particles, which is a priority goal of W7-X.

Thermal-hydraulic analysis of the DTT CS and PF pulsed coil performance during AC operation

The EU DEMO fusion reactor, now entering in its conceptual design phase, will have to tackle several challenges, such as the long plasma pulse duration and the exhaust of very high heat fluxes from the plasma. The Divertor Tokamak Test (DTT) facility, a compact superconducting tokamak under construction at ENEA Frascati, will address the power exhaust problem in DEMO by testing several DEMO-relevant divertor solutions and operation scenarios.The DTT superconducting coils are the subject of the analyses presented here: as the tokamak must be very flexible to face different plasma scenarios, the design of the magnet system must be proven to be robust. In particular, the thermal-hydraulic performance of the coils operated in pulsed mode, namely the Central Solenoid (CS) and the Poloidal Field (PF) coils, will be analyzed. The CS is composed of 6 modules, layer-wound with Nb3Sn Cable-in-Conduit Conductors (CICCs), while the PF coils are pancake-wound. The two PF coils closest to the machine axis are wound using Nb3Sn CICCs, while the others adopt NbTi CICCs. All the coils are cooled by supercritical He (SHe) in forced flow.The pulsed operation of these coils induces AC losses, eroding their temperature margin: a detailed thermal-hydraulic model of the DTT pulsed coils is developed here using the 4C code. The model is then applied to the simulation of the two reference plasma scenarios, a single null and a double null, computing the minimum temperature margin. Different cooling options (single- or double-pancake) are investigated for the PF coils, while the sensitivity to the coupling time constant value is assessed for the CS.

Requirements and interface management for the divertor system design and integration in the Divertor Tokamak Test (DTT) facility

The construction of a Divertor Tokamak Test (DTT) facility is fully included in the European effort towards the realization of fusion energy with the aim of studying possible alternative solutions, with respect to the ITER research program, to tackle the problem of power exhaust. This means that the machine must be compatible with different possibilities for the divertor cassette design and the plasma scenario. The design of first “reference” divertor is largely based on the ITER-like divertor, but in the future other solutions are going to be tested, including liquid metal divertors. To provide a justification basis for the design of the reference cassette and guidelines for the future experimentations it is fundamental to define the requirements of this power exhaust system, in particular the heat flux compatibility and the interfaces with the surrounding interacting systems of the tokamak (the water cooling pipes, the divertor magnetic coils, the divertor diagnostics, etc.). This work shows how the divertor system can be included in a wider Requirement Management procedure that has been defined for DTT highlighting the relevant interface parameters. Additionally, a data analysis tool has been developed to provide an interactive visualization of requirements traceability to directly show the impact of changes in the divertor on the design and operations of the machine and viceversa. In this way, during future studies on alternative design divertors or plasma scenarios, the limiting constraints on both sides can be easily individuated and traced to their motivation, and possibly discussed.

Design and Implementation of a Low Power Consumption of ASK, FSK PSK, and QSK Modulators Based on FPAA Technology

Wireless communication techniques have become more popular due to their characteristics. These systems adopt the digital modification application, which provides more information for transmission and compatibility with digital data services as well as high information security and quality improvement. Digital wave signal-based communication techniques such as PSK, FSK, ASK, and QPSK considered among the most significant digital modulation techniques. These technologies are a crucial part of digital communication systems. Digital communication devices designed by FPAAs can provide multiple communication without arranging new devices and can support new within seconds. FPAA is extremely easy to reconfigure and program concerning FPGA or DSP-based applications. This article offers real-time implementation of ASK, FSK PSK, and QPSK modulator techniques with low power consumption ”Žbased on the ”Žcapability for dynamic reprogramming of the FPAA AN231E04 device ”ŽAnadigm. FPAA techniques provide growing application and high pliability in the implementation of analog circuits. The measurements achieved from the proposed modulated circuits show that the form and properties of the theoretical outcomes agree perfectly with the practical outcomes. FPAA techniques provide growing application and high pliability in the implementation of analog circuits for minimizing the time of design and testing. Another feature is the minimum power exhaustion (165 mw) due to the switched capacitor method used by the FPAA Chip, which gives a high accuracy process.

CFD Analyses for the Upgrade Divertor System of KSTAR

The Korea Superconducting Tokamak Advanced Research (KSTAR) device, constructed in 2008, is a world-class superconducting tokamak fusion research device for the development of fusion energy. The expected heating power goal has been set to 12 MW by using an additional heating system, i.e., the second neutral beam injection (NBI) system NBI-2. As the heating power increases, resistance to high heat flux and cooling capacity at the divertor should be improved to exhaust power in the scrape-off-layer domain. Therefore, an upgrade of the divertor system for KSTAR was launched in 2019, and the upgrade divertor will be installed by 2022. The peak heat flux on the divertor target in steady-state operation is set to 10 MW/m2, and the ITER-like divertor type, the water-cooled tungsten monoblock, has been applied. The upgrade KSTAR divertor system comprises 64 cassette divertor modules. A divertor module consists of the inner target, the central target, the outer target, and the cassette body with supports to connect each part. In this study, thermal analyses were carried out to confirm the design’s thermal robustness for a whole divertor module. The temperature distribution and pressure drop were calculated by computational fluid dynamics analyses. Based on the response surface optimization method, the optimized tungsten monoblock design was derived. The optimized monoblock design showed that all materials, tungsten, Cu, and CuCrZr, comprising the divertor target, are operated within their allowable temperature windows. For the global divertor model applying the optimized monoblock design, steady-state and transient analyses were carried out for heat fluxes of 10 and 20 MW/m2. At 10 MW/m2, all composing materials were operated within the allowable temperature, while the maximum temperatures of tungsten, Cu, and CuCrZr exceeded the allowable temperature range of 20 MW/m2. However, the results were acceptable since the temperatures are sufficiently lower than the melting temperatures, and the slow transient case occurs quickly.

The Role of Fatigue in Return to Sport Testing Following Anterior Cruciate Ligament Reconstruction.

BackgroundFatigue may play a role in anterior cruciate ligament (ACL) injury, but has not been incorporated into objective test batteries for return to sport decisions following ACL reconstruction (ACLR) surgery. The effect of fatigue on muscle function and performance following surgery and rehabilitation has been poorly studied.Purpose/HypothesisThe purpose of this study was to assess the effect of fatigue on performance of various hop tests used in clinical rehabilitation settings by examining LSI scores. The authors hypothesized that participants will have worse limb symmetry index scores following the fatigue protocol and that the operative limb (ACLR) will have a greater decline in function than the non-operative limb (CON).Study DesignCross-Sectional Study.MethodsParticipants (n=21 [Male = 15, Female = 6]; AGE = 24.6 ± 9.3) were at least six months post ACLR and in rehabilitation. Testing was performed over two separate sessions in either a non-fatigued (NFS) or fatigued state (FS). In the FS, individuals performed a series of exercises to exhaust muscular endurance, strength, and power systems, after which they performed as battery of seven hop tests (single hop for distance, triple hop for distance, crossover hop for distance, 6-meter timed hop, lateral rotation hop for distance, medial rotation hop for distance, and vertical jump for height). A 2(limb) x 2(time) ANOVA was used to compare limbs between each state.ResultsDifferences between limbs (CON vs ACLR) were observed for all hop tests in the NFS whereby the ACLR limb was observed to have reduced performance (↓5.4-9.1%, p <0.05). When tested in the FS, significant differences in performance between limbs remained for only the crossover (↓4.9%), medial rotation (↓7.1%), lateral rotation (↓5.5%), and vertical hop (↓10.0%)(p<0.05). When comparing the NFS and FS states, only the CON limb was observed to have significant decreases in performance of the Triple Hop (↓7.4%), Crossover (↓8.7%), and Lateral Rotation (↓5.2%)(p<0.05).ConclusionsFollowing ACL reconstruction, there appears to be a greater loss in jump performance in the CON limb in the FS. These findings suggest it may be crucial to consider and assess the endurance of both limbs rather than just the ACLR limb when determining readiness for return to play.Level of EvidenceLevel 3

Design status of the Vacuum Vessel of DTT facility

The Divertor Tokamak Test (DTT) facility is an experimental facility under design and construction at ENEA C.R. Frascati. The aim of DTT is to investigate the power exhaust problem in a tokamak, providing possible alternative divertor solutions, with respect the conventional one, which can be extrapolated to DEMO fusion reactor. One of the main components of DTT facility is the Vacuum Vessel (VV), which has the function of providing an enclosed, vacuum environment for the plasma, acting also as a first confinement barrier. Starting from geometrical constraints, imposed by the desired plasma scenario and the configuration needed for the magnetic coils, the conceptual design of the VV was developed and dedicated research activities were carried out to verify design choices. A multiphysical approach was adopted with the aim of identifying a feasible and reliable solution for the VV, taking into account functional and design requirements, relevant aspects and issues. In particular, to assess and to optimize the VV design, fluid-dynamic, thermal and structural analyses were carried out, which are presented in the paper, as well as the progresses of the design.