ITER Research Articles

An Improved Calculation Method of Coil Offset on the Large-Caliber Magnetic Field Immunity Testing System for ITER

The magnetic field immunity testing system is important equipment for ITER (International Thermonuclear Experimental Reactor), which is mainly used for electromagnetic compatibility tests in strong magnetic field environments. The test system is mainly composed of coil structure. In this paper, the influence of coil offset on the magnetic field performance of the system is studied. There are 18 degrees of freedom offsets of position and angle on the X, Y and Z axes of the coil, and different offsets have different effects on the magnetic field performance. The different offset combinations of a single coil and two coils are discussed, and various distributions of magnetic field performance are calculated. Then, according to the law, the calculation method is improved, and a reasonable and effective method is selected to calculate the maximum allowable offset of simultaneous position and angle migration under the premise of extremely many variables. In the paper, the influence of spatial multi degree of freedom coil offset error on magnetic field uniformity is studied, the relationship between multivariable allowable offset and magnetic field error accuracy is analyzed, and the allowable offset under different installation errors is determined. This provides a theoretical basis for actual installation.

Determination of expression level of AP1S1, CDK9, FIGF and HDAC11 genes in bladder tumors for aggressive phenotype characterization

Bladder cancer holds a steady 10th place among oncological diseases. Follow-up and timely diagnosis of recurrence and progression of bladder cancer are still based on regular but outdated cystoscopy followed by cytological examination. To reduce the number of cystoscopy procedures, new and reliable biomarkers for predicting tumor behavior must be developed. The aim of this study was to confirm our previous results that demonstrated overexpression of AP1S1, CDK9, FIGF and HDAC11 in muscle-invasive bladder cancer. The project management was performed using iterative flexible project work (Flexible Methodology for Innovative Projects in Scientific Organizations, FMIPSO). Gene expression analysis of the AP1S1, CDK9, FIGF and HDAC11 genes was evaluated in 39 newly collected non-invasive and muscle-invasive bladder tumors. Differential gene expression was calculated using the ΔΔCt method with GPDH as a housekeeping gene. The 4,0-fold change in gene expression was used as a cutoff to determine up- or down-regulation compared to the negative control. Our results demonstrate the involvement of the FIGF, CDK9 and HDAC11 in tumor progression and their potential use as candidate biomarkers to characterize invasive tumor phenotype and muscle progression, as well as potentially reduce the number of cystoscopies. We used FMIPSO to be able to achieve the results at the optimum level of efficiency and control of the project with all possible constraints in scientific organizations.

Direct phase determination in protein crystallography using iterative projection algorithms

Direct phase determination in protein crystallography using iterative projection algorithms

The impact of interest: an emergent model of interest development in the early years

ABSTRACT The literature defines curiosity and interest, but it is not clear how interest can be generated, where interest is positioned in the learning process, and what the impact of interest is on cognitive and emotional development. This paper reports on a three-year, iterative design-based research project involving three separate cohorts totalling 57 early learners in an early learning setting in Southern Queensland, Australia. The young learners aged 4–5 years, engaged in an enrichment program that extended over a two-week period for each of 15 topics. Insights were gained on how young children developed interested in a topic. An emergent model of authentic interest was developed, showing how interest is situated centrally in the learning process. It also shows how interest raised awareness, exploration, and new knowledge, creating a cycle of repeated engagement with the topic, thereby enhancing cognitive and emotional development.

Nuclear scoping analysis of ITER bioshield top lid toward its preliminary design review

During ITER operations, electronics located in the crane hall, which is above the tokamak, will be exposed to neutron and photon fields from both the plasma and the activated water. To protect the electronics, the implementation of dedicated shielding on the crane hall platform and the bioshield top lid is required. The design demands optimisation attending to constructability, weight limits, and radiation shielding requirements. This work evaluates eight shielding configurations by assessment of the neutron flux and dose accumulated over 4700 h of operation at 500 MW for electronics protection. This corresponds to a neutron wall load of 0.3 MW a/m² as specified in the ITER Project Specification. An intermediate-source approach has been followed with SRC-UNED, considering all relevant radiation sources while minimising the computational time required. Results were presented at the top lid Conceptual Design Review aiming to support decision-making. Further optimisation has since been performed to reach a top lid proposal for its Preliminary Design Review. All outcomes show that radiation levels above the north and south crane hall platforms are compatible with the critical electronics requirements.

Modeling of toroidal momentum transport induced by neoclassical toroidal viscosity torque for ITER scenarios

Neoclassical toroidal viscosity (NTV) torque caused by resonant magnetic perturbation (RMP) and the induced toroidal momentum transport are investigated for International Thermonuclear Experimental Reactor (ITER) scenarios through numerical modeling. The NTV torque is calculated using the NTVTOK code including the bounce-drift resonant effect, and the toroidal rotation evolution is modeled by solving a toroidal momentum transport equation that couples momentum source (NTV torque) and the momentum diffusion effect. The variation of RMP coil phasing (defined as toroidal phase difference between different rows of RMP coils) results in different types of plasma response and hence different features of NTV torque and toroidal momentum transport. The bounce-drift resonant effect enhances NTV torque and induces more significant toroidal rotation variation than simulations that adopt the bounce-averaged NTV model. With the initial rotation of the ITER design, plasma rotation is braked by NTV torque, but it may be sustained at moderate amplitude due to electron contributions to NTV torque. It is also found that initially static or slowly rotating plasma can be accelerated by NTV torque either toward co- Ip or counter- Ip ( Ip indicates plasma current) direction, indicating that NTV torque can be regarded as a momentum source for plasma with low torque injection; for instance, radio-frequency heated plasma.

Application of the 2D Code Tamic Analyzer Based on the Method of Impedance Analog of the Sestroretskii Electromagnetic Space for Problems of Plasma Diagnostics in Tokamak Fusion Facilities

Applications of the two-dimensional full-wave electromagnetic code Tamic Analyzer, developed by B.V. Sestroretskii to study the limiting possibilities of diagnostics of reflectometry in tokamak plasma. It is shown that by comparing experimental reflectometry data with calculations using this code, it is possible to determine the structure of density fluctuations in a tokamak, but the experimental radial correlation lengths can be significantly overestimated. Simulation using the Taimic Anylyser code made it possible to determine the limiting level of density fluctuations at which it is possible to measure the plasma density profile and observe Alfven fluctuations in the International Experimental Thermonuclear Reactor of the tokamak type (ITER) under construction. Possible ways to increase the speed and counting field of the code are considered.

Vacuum Brazing and Performance Evaluation of T2 Copper Block and 316L Stainless Steel Tube

The International Thermonuclear Experiment Reactor (ITER) Thermal shield (TS) serves as a cryogenic heat exchanger to maintain the thermal stability of the ITER superconducting magnet coil, which is critical to the control of the plasma during the operation of the ITER device. The TS is composed of long-length 316L stainless steel (SS) and copper as brazed joints. In this case, a feasible fabrication design for the CCS TS is presented, accomplished by three kinds of joining processes (vacuum brazing, friction stir weld, and TIG weld). In the reliable fabrication design, the brazing quality of the as-brazed long-distance 316L SS and copper joints plays a critical role in the thermal conductivity performance of the ITER thermal shield. Therefore, a high-quality vacuum brazing process of long-length SS/Cu joints applied in a low-temperature superconductor magnet system was first studied. The macro metallography analysis demonstrates the braze ratio of the samples is 100%, and no crack or defect is observed in the samples. The microstructural characterization reveals the brazing seams are composed of silver-based Ag-rich eutectic. The micro-shear test indicates that the shear strength of the 316L tube and copper joint is 205 MPa, with the fracture position located on the copper side; this zone will be the most vulnerable zone of the joints. In addition, the SEM results illustrated that the shear fracture morphology displayed a ductile fracture feature. The test results demonstrated that the highly precise depth drilling employed in this paper ensured a good control of the brazing clearance, resulting in a 100% braze ratio for the long-length SS/Cu joints. Therefore, it can be concluded that the brazing process can be applied in the ITER TS for the good thermal conductivity performance of long-length SS/Cu-brazing joints.

Efficient Overdetermined Independent Vector Analysis Based on Iterative Projection with Adjustment

In this paper, a computationally efficient optimization algorithm for independent vector analysis (IVA) is proposed to accelerate iterative convergence speed and enhance the overdetermined convolutive blind speech separation performance. An iterative projection with adjustment (IPA) is investigated to estimate the unmixing matrix for OverIVA. The IPA algorithm jointly executes the iterative projection (IP) algorithm and the iterative source steering (ISS) algorithm to jointly update one row and one column of the mixing matrix, which can perform computationally-efficient blind source separation. It is achieved by updating one demixing filter and jointly adjusting all the other sources along its current direction. Motivated by its technology superiorities, this paper proposes a modified algorithm for the OverIVA, fully exploiting the computational efficiency of IPA optimization scheme. Experimental results corroborate the proposed OverIVA-IPA algorithm converges faster and performs better than the existing state-of-the-arts algorithms.

The BRI as an Iterative Project: Influencing the Politics of Conflict-Affected States and Being Shaped by the Risks of Fragile Settings

ABSTRACT This article examines the impact of the BRI on the peace processes of conflict-affected states (CAS) bordering China, namely Nepal and Myanmar. It underscores the need to assess the impact of the BRI as an iterative process: where the BRI impacts the political economy of host CAS; but also how contextual specificities of the CAS, undertaking a peace process, are reshaping the delivery of the BRI. Here, the article first outlines that the BRI is not only physically transforming host CAS through infrastructure and connectivity but also influencing the core agenda of the peace processes, notably federalism, through the uneven distribution of benefits of infrastructural development. Second, the challenges of working in the complex settings of CAS, with fragmented state authority, and political uncertainty have also brought significant changes in the delivery of the BRI and Chinese diplomacy broadly.

Iterative List Patterned Reed-Muller Projection Detection-Based Packetized Unsourced Massive Random Access.

In this paper, we consider a slot-controlled coded compressed sensing protocol for unsourced massive random access (URA) that concatenates a shared patterned Reed-Muller (PRM) inner codebook to an outer error-correction code. Due to the limitations of the geometry-based decoding algorithm in single-sequence settings and due to the message interference that may result in decreased decoding performance under multi-sequence circumstances, a list PRM projection algorithm and an iterative list PRM projection algorithm are proposed to supplant the signal detector associated with the inner PRM sequences in this paper. In detail, we first propose an enhanced path-saving algorithm, called list PRM projection detection, for use in single-user scenarios that maintains multiple candidates during the first few layers so as to remedy the risk of spreading errors. On this basis, we further propose an iterative list PRM projection algorithm for use in multi-user scenarios. The vectors for PRM codes and channel coefficients are jointly detected in an iterative manner, which offers significant improvements regarding the convergence rate for signal recovery. Furthermore, the performances of the proposed algorithms are analyzed mathematically, and we verify that the theoretical simulations are consistent with the numerical simulations. Finally, we concatenate the inner PRM codes that employ iterative list detection in two practical error-correction outer codes. According to the simulation results, we conclude that the packetized URA with the proposed iterative list projection detection works better than benchmarks in terms of the number of active users it can support in each slot and the amount of energy needed per bit to meet an expected error probability.

Subspace recursive Fermi-operator expansion strategies for large-scale DFT eigenvalue problems on HPC architectures.

Quantum mechanical calculations for material modeling using Kohn-Sham density functional theory (DFT) involve the solution of a nonlinear eigenvalue problem for N smallest eigenvector-eigenvalue pairs, with N proportional to the number of electrons in the material system. These calculations are computationally demanding and have asymptotic cubic scaling complexity with the number of electrons. Large-scale matrix eigenvalue problems arising from the discretization of the Kohn-Sham DFT equations employing a systematically convergent basis traditionally rely on iterative orthogonal projection methods, which are shown to be computationally efficient and scalable on massively parallel computing architectures. However, as the size of the material system increases, these methods are known to incur dominant computational costs through the Rayleigh-Ritz projection step of the discretized Kohn-Sham Hamiltonian matrix and the subsequent subspace diagonalization of the projected matrix. This work explores the potential of polynomial expansion approaches based on recursive Fermi-operator expansion as an alternative to the subspace diagonalization of the projected Hamiltonian matrix to reduce the computational cost. Subsequently, we perform a detailed comparison of various recursive polynomial expansion approaches to the traditional approach of explicit diagonalization on both multi-node central processing unit and graphics processing unit architectures and assess their relative performance in terms of accuracy, computational efficiency, scaling behavior, and energy efficiency.

The long-term creep behavior and damage mechanism of RAFM steel for fusion reactors

The reduced-activation ferritic-martensitic (RAFM) steel serves as the structural material for the blanket of the International Thermonuclear Experimental Reactor (ITER) and future fusion reactors. In order to achieve a design lifetime of 2–3 years for the blanket in the fusion reactor, it is imperative to thoroughly understand the long-term (>20,000 h) creep behavior of RAFM steel. In this regard, the present study investigated the long-term creep damage mechanism of RAFM steel under creep periods greater than 20 000 h. The results indicated that the creep exponent decreases as the creep rupture time increases from several thousand hours to more than 20,000 h. The microstructure analysis revealed that dislocation slip was effectively pinned by the precipitates in the long-term creep process. Additionally, the M23C6 and Laves phase played a critical role in inhibiting interfacial slip and preventing lath coarsening. However, a few micron-scale M23C6 and Laves phases led to the formation of cavities in the boundary. These cavities subsequently polymerized and aggravated into cracks, ultimately becoming the primary mechanism for the long-term creep fracture.

Strategies for Real-Time Simulation of Central Solenoid ITER Power Supply Digital Twin

The International Thermonuclear Experimental Reactor (ITER) is a cutting-edge project that aims to develop a sustainable energy source by harnessing the power of nuclear fusion. One of the key challenges in the development of the ITER is the complex electrical grid that is required to support its operations. To address this challenge, a digital twin (DT) of the Central Solenoid (CS) Converter Power Supply grid has to be developed, and real-time simulation strategies have been proposed to monitor and study the performance of the ITER grid. Real-time simulation strategies allow for continuous feedback on the performance of the grid, enabling the quick identification and resolution of issues. However, it is not always possible to perform real-time simulation easily in a real-time simulator; therefore, specific strategies have to be implemented in the DT. This paper focuses on decoupling lines and explicit partitioning as solutions to allow the real-time simulation of the CS Converter Power Supply grid with two converter units (CUs), as required by the ITER Organization (IO). As will be shown later in this article, the proposed approach is progressive and applicable to a more complex grid with multiple CUs. The results concerning the proposed strategies will be analyzed and discussed in terms of real-time performance.

Formation of the hot tail seeds for runaway electron generation during disruptions with lower hybrid waves in the HL-2A tokamak

The hot tail generation is expected to be the dominant mechanism for the runaway electron (RE) seed formation during disruptions, especially in large devices with high electron temperature such as international thermonuclear experimental reactor. This issue has been studied in the HL-2A tokamak by using the superthermal electrons produced by lower hybrid waves (LHWs), which can adjust the hot tail distribution. It was observed that RE generation was significantly enhanced during disruptions with LHWs. The measurements show that the multitudinous superthermal electrons with energy of 40–60 keV created by LHWs greatly transform the landscape of hot tail distribution. The tail electrons can be directly converted into REs under the acceleration of the high toroidal electric field during disruptions. Runaway current plateaus are more likely to be formed than in normal disruptions without LHWs. However, some abnormal phenomena have also been observed, that is, RE generation was not enhanced and no runaway current plateau was formed during some disruptions with LHWs. It is found that this is attributed to the complete loss of RE seeds caused by strong magnetic fluctuations, which prevents the generation of REs during disruptions. This may provide a way to avoid the generation of REs during disruptions by actively exciting magnetic fluctuations.

IFMIF-DONES Y LA ENERGÍA DE FUSIÓN

Fusion is a safe, sustainable and massive energy source whose profitable exploitation is a huge technological challenge. Over the past seventy years, numerous investigations and major experiments have brought us close enough to a viable solution to now have a well-defined roadmap, supported by two big experiments that will confirm, on the one hand, how fusion energy production should be optimized (ITER project) and, on the other hand, which materials are suitable for use in the most critical areas of future fusion reactors (IFMIF-DONES project). This article aims to convey the magnitude and the challenges faced by the latter.

Project managers' ability to explore and exploit predictive and iterative best practices

Purpose Project managers face decisions every day and those decisions result in an “either or” situation. This is also true when it comes to the choice of a project management approach, i.e. predictive versus iterative. A case is made in this article that project managers should be ambidextrous and apply practices that are beneficial to the project, irrespective of the origin of the practices.Design/methodology/approach This study is based on a questionnaire focussing on six themes. The results of 290 projects were analysed using ANOVA and boxplots to test for skewness and variances.Findings Based on the analysis of 117 practices, most of these projects could be classified as either hybrid or iterative projects. The results indicate that irrespective of the classification of the projects or the industry, projects are managed using a hybrid approach, with a tendency to incorporate more iterative practices than predictive practices.Originality/value This article contributes to the current debate on which approach is the best given certain circumstances.

Fast Fluid Simulation via Dynamic Multi-Scale Gridding

Recent works on learning-based frameworks for Lagrangian (i.e., particle-based) fluid simulation, though bypassing iterative pressure projection via efficient convolution operators, are still time-consuming due to excessive amount of particles. To address this challenge, we propose a dynamic multi-scale gridding method to reduce the magnitude of elements that have to be processed, by observing repeated particle motion patterns within certain consistent regions. Specifically, we hierarchically generate multi-scale micelles in Euclidean space by grouping particles that share similar motion patterns/characteristics based on super-light motion and scale estimation modules. With little internal motion variation, each micelle is modeled as a single rigid body with convolution only applied to a single representative particle. In addition, a distance-based interpolation is conducted to propagate relative motion message among micelles. With our efficient design, the network produces high visual fidelity fluid simulations with the inference time to be only 4.24 ms/frame (with 6K fluid particles), hence enables real-time human-computer interaction and animation. Experimental results on multiple datasets show that our work achieves great simulation acceleration with negligible prediction error increase.

Robust and Fast Measure of Information via Low-Rank Representation

The matrix-based Rényi's entropy allows us to directly quantify information measures from given data, without explicit estimation of the underlying probability distribution. This intriguing property makes it widely applied in statistical inference and machine learning tasks. However, this information theoretical quantity is not robust against noise in the data, and is computationally prohibitive in large-scale applications. To address these issues, we propose a novel measure of information, termed low-rank matrix-based Rényi's entropy, based on low-rank representations of infinitely divisible kernel matrices. The proposed entropy functional inherits the specialty of of the original definition to directly quantify information from data, but enjoys additional advantages including robustness and effective calculation. Specifically, our low-rank variant is more sensitive to informative perturbations induced by changes in underlying distributions, while being insensitive to uninformative ones caused by noises. Moreover, low-rank Rényi's entropy can be efficiently approximated by random projection and Lanczos iteration techniques, reducing the overall complexity from O(n³) to O(n²s) or even O(ns²), where n is the number of data samples and s ≪ n. We conduct large-scale experiments to evaluate the effectiveness of this new information measure, demonstrating superior results compared to matrix-based Rényi's entropy in terms of both performance and computational efficiency.

Distributed load restoration for interdependent transmission-distribution-gas systems considering pipeline gas storage capacity

Recent electricity systems have witnessed many power outage events, and the interrupted loads must be restored as soon as possible to reduce the enormous outage losses. However, the ever-increasing interdependencies of the transmission, distribution, and gas systems cause the restoration behaviors of a system to inevitably influence the others, which brings about new impacts on the load restoration decisions. Moreover, the different velocities of power and gas flows cause additional complexities in making load restoration decisions for the whole system. To address these problems, this paper proposes a new load restoration scheme coordinating transmission, distribution, and gas systems. Firstly, to respect the information privacy of individual energy subsystems, a distributed load restoration coordination structure is proposed with the interactions of different energy systems and corresponding load restoration models considering pipeline gas storage capacity caused by slow gas flow dynamics. Based on the distributed restoration coordination structure and considering that discrete variables in load restoration models hinder the efficient calculation, a projection function-based adaptive alternating direction method of multipliers is then proposed with iterative relaxation and projection of discrete variables. Finally, simulation results in the T118-D33-N56 test system and a real-world system in China demonstrate that coordination of transmission, distribution, and gas systems and considering pipeline gas storage capacity can shorten the load restoration time. The proposed solution method also shows good computational performance.