Abstract: The Remote Handling (RH) system of the Italian Divertor Tokamak Test (DTT) facility is undergoing significant advancements, particularly in the design of the Cassette Multifunctional Mover (CMM), the robot devoted at handling both the lateral and central divertor cassettes.This paper presents the design of the Central Cassette End-Effector (CCEE), the RH equipment that will be mounted on the CMM to perform RH operations for the central cassettes. A black box analysis was performed to define the RH operation procedure and elicit a preliminary set of functional requirements. From this set of requirements, tight space constraints due to the port geometry emerged, and also additional actuations of the end-effector were needed to preload the cassette body without stressing the CMM structure. Thus, the V-Model with the Requirement, Functional, Logical, Physical (RFLP) approach in MAGIC Systems of Systems Architect, provided by Dassault Systèmes, was adopted to develop the design from the requirement elicitation to the architecture definition. The defined logical architecture was traced to the physical model in CATIA V6 within the 3DExperience platform. Finally, to verify the fulfillment of the space constraints and the proper functions of the robot actuations in the proposed procedure, a kinematic analysis of the CMM and the CCEE assembly was performed. The results demonstrated the feasibility of the procedure to be validated during the assembly phase planned in 2026 in the DTT Remote Handling Test and Training facility (REMHAT) under construction in Naples, Italy. © 2026 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license. http://creativecommons.

Keywords: Cassette Multifunctional Mover (CMM) | Divertor Tokamak Test (DTT) | Kinematic simulation | Model-Based Systems Engineering (MBSE) | Remote Handling (RH) | V-Model

Abstract: The EU-DEMO is one of the most ambitious projects of EUROfusion, aimed at designing a prototype of a nuclear fusion power plant. In 2025 a new Low-Aspect-Ratio (LAR) configuration has been introduced, replacing the past baseline by changing the aspect ratio (A) of the tokamak from 3.1 to 2.8. The LAR has several benefits from the divertor point of view, the main one is the lower heat load on the plasma facing components (PFCs). The peak heat flux to the divertor during reattachment decreased, with respect to the previous EU-DEMO configuration, by about 45%, from ≈82 MW/m2 to ≈44 MW/m2. This work presents the design of the divertor system in the LAR configuration by adopting System Engineering (SE) approach. Starting from previous baseline, the current design is updated with aim of improving the manufacturing, shielding and structural performances. Using the SE approach, previously implemented features can be transferred and modified in a rational way in the new LAR configuration. New PFCs have been proposed as well as new cooling layout for the cassette body. The inboard vertical target design has been modified based on the results obtained from the previous baseline, aiming to improve the shielding performance and reduce the temperature of the supports in normal operations.

Keywords: Divertor | EU-DEMO | Eurofer97 | Systems engineering | Virtual prototyping

Abstract: The Ion Cyclotron Resonance Heating (ICRH) antenna for the Divertor Tokamak Test (DTT) facility is expected to be not only cantilevered, radially movable and fully cooled, but also remote handled: the additional challenge of the Remote Handling (RH) from the inner of the chamber has been posed. The remote assembly and disassembly will be performed through the HYper Redundant MANipulator (HYRMAN) and clearly require the design of the linking interfaces between the remote handled parts and the components placed behind. But the development of in-vessel Radio Frequency (RF) contacts proved in the past to be very challenging, raising concerns on their long-term reliability. Therefore, the toroidal size of the current straps has been reduced to make them, and the relative RF contacts, directly pass through the Vacuum Vessel equatorial port. Thus, only the leftover geometry of the ICRH antenna frontal part should be remote handled and alternative RH strategies have been analyzed and compared. The selecting criteria have been based on the requirements to be fulfilled like the payload limit of the HYRMAN and the RF performance, and on the subcomponents functions to be guaranteed like the side straps shielding. Furthermore, the choice process has also considered technical reasons such as the number of RH operations and interfaces to robotic arms, the minimum number of cooling circuits and the flexion risk.

Keywords: Divertor Tokamak Test | ICRH antenna | Radio Frequency analyses | Remote Handling

Abstract: In the project development of large fusion machines, the alignment and assembly phases represent an open challenge. Each mechanical component that constitutes the whole machine assembly and fixtures is affected by an intrinsic geometrical variation due to manufacturing and assembly processes. The complexity of the assembly together with the unavoidable geometrical imperfection can affect the expected machine functionalities. In this context, Reverse Engineering activities, aiming at obtaining the as-built of the components, coupled with virtual fitting studies, defining optimum alignment using the real shape of the components, become powerful risk mitigation tools in the assembly phases. This work presents a systematic method, complementary to the methodology currently followed in the ITER project, for the as-built management and for the validation of alignment phases of such a complex assembly. The first phase is to identify the key assembly requirements which drive the alignment of the ITER assembly. Then, the database for the requirement collection is clearly organized following the proper nomenclature rules and its architecture for data collection and analysis is indeed set up.

Keywords: Alignment | As-built Management | Assembly Requirements | ITER tokamak | Requirement Management | Virtual Fitting

Abstract: A structured process is in place to manage the geometrical requirements of the ITER machine and the associated risk. This process involves systematically breaking down geometrical requirements from the project level to system, sub-system until component level. The breakdown at component level feeds the manufacturing phase. A proper management and cascading of those requirements is accomplished to create a solid link between design intents and manufactured component. Clear, reachable and reasonable geometrical requirements must be cascaded to the manufacturers to avoid over-constrains or showstoppers in the lifecycle. Along the manufacturing process, it becomes possible to leverage the as-built geometrical data from the as-manufactured component to feedback reverse engineering process and optimize the subsequent assembly phases of the fusion machine. This paper addresses the complexity of the above-described dimensional risk management approach, detailing each phase of the process, from design through manufacturing to final assembly. © 2025 Elsevier B.

Keywords: Dimensional Risk Management | ITER life cycle | ITER machine | Metrology requirements | Requirements flow down | Requirements management

Abstract: The Vacuum Vessel is one of the main systems of the ITER tokamak. The welded steel, torus-shaped vessel, houses the plasma and acts as a first safety containment barrier. It provides support for In-Vessel components and removes the heat generated during operation by mean of cooling water circulating through its walls. To ensure the functionality of the system, strict geometrical requirements have been defined on several features. The large scale of the component and the complexity of the manufacturing raised the need to develop metrology strategies that improve the awareness of the decision-making processes and minimize the risk of non-compliance of the final product. Virtual Fitting is a technique that enables to find the optimal way of assembling parts together considering their real shapes. By defining requirements to include in the analysis and their priority, an optimum can be found by least square minimization of the as-built data deviation from the nominal reference. The method has been deployed in one of the most critical stages of the Vacuum Vessel production, the assembly of the four poloidal segments composing the final sector. The analysis provided the actors involved several alignment scenarios, from which corrective actions have been derived, in terms of time, cost and quality. Firstly, this paper presents the principles of the Virtual Fitting technique, then the second part focuses on the application of the Vacuum Vessel European Sector #5. © 2025 Elsevier B.

Keywords: Alignment, Assembly | Fusion Technology | ITER tokamak | Vacuum vessel | Virtual fitting

Abstract: This paper describes the design and realisation status of the Ion Cyclotron Range of Frequency (ICRF) system of the Divertor Tokamak Test facility (DTT). DTT requires a large amount of additional heating partially provided by an ICRF system working in the frequency range from 60 to 90 MHz. The system will be modular, with each module aimed at coupling at least 3 MW for 50 s every hour to the DTT reference plasma as well as to contribute to wall cleaning tasks with lower power and higher duty cycle. Compared to existing and planned ICRF plants for tokamaks and stellarators, the radiofrequency system of DTT presents some peculiar features, mostly with reference to the technology of radiofrequency generators and to the mix of challenges the antenna design has to face like geometry decomposition, remote assembly and maintenance. The system design started some years ago and, in the last two years, 50+ collaborators contributed to make advances in its definition and development. Recently the ICRF system of DTT entered its realisation phase, with the issue of the first calls for tender, one of which for the procurement of two radiofrequency sources, while some aspects are still under design.

Keywords: DTT | ICRH | Plasma heating

Abstract: The digital modeling and optimization of production processes in the aerospace sector are crucial endeavor for enhancing operational efficiency and competitiveness. This paper presents the process optimization strategy of an aerospace production line by adopting the discrete event simulation technique. The 3DExperience platform has been chosen as a promising co-simulation tool for the digital model development. The production processes have been digitally modeled, and process flows have been analyzed for achieving a comprehensive line flow balancing optimization identifying critical bottlenecks. Various scenarios have been analyzed and compared enhancing process operational efficiency. Initial results outline significant imbalances in the utilization of workstations, suggesting a lack of efficiency in resource allocation.

Keywords: Aeronautical Components | Assembly Line | Line Flow Balancing | Process Optimization

Abstract: The design of an assistive device for a student with disabilities to enable his inclusion into the University is based on ethical reasons. The device must be personalized starting from a participative and human centered approach. This work presents the design and development phases of a highly functional assistive device which enables a quadriplegic user, who is unable to speak, to autonomously communicate. The starting phase deals with the identification of the user needs, considering the residual mobility of a single arm and the needs of the caregivers. The motion study allows to define the requirements which enable the definition of the system architecture. A modular architecture is chosen, allowing damaged or obsolete parts to be easily replaced extending the useful life of the device, but reducing the resources consumption during the life cycle. Sustainable and recyclable materials are selected using Additive Manufacturing technologies.

Keywords: Human centered design | Inclusive design | Personalized assistive device

Abstract: An overview is presented of the progress since 2021 in the construction and scientific programme preparation of the Divertor Tokamak Test (DTT) facility. Licensing for building construction has been granted at the end of 2021. Licensing for Cat. A radiologic source has been also granted in 2022. The construction of the toroidal field magnet system is progressing. The prototype of the 170 GHz gyrotron has been produced and it is now under test on the FALCON facility. The design of the vacuum vessel, the poloidal field coils and the civil infrastructures has been completed. The shape of the first DTT divertor has been agreed with EUROfusion to test different plasma and exhaust scenarios: single null, double null, X-divertor and negative triangularity plasmas. A detailed research plan is being elaborated with the involvement of the EUROfusion laboratories.

Keywords: divertor | exhaust | plasma scenarios

Abstract: Effective project management methods, tools and working practices shall be applied to facilitate the communication and collaboration among the different institutions involved in the Divertor Tokamak Test (DTT) project. This paper deals with the definition of the configuration management platform architecture enabling technical integration of the DTT system. The first step consists in the identification of main requirements the platform should satisfy, considering the multidisciplinary domains and the geographically dispersed working teams characterizing the nuclear fusion sector and the maturity level of the specific project. Main characteristics of the most advanced Product Lifecycle Management (PLM) tools are identified, their limits and benefits are evaluated, and the suitable PLM platform is selected, satisfying the DTT project needs. The definition of the architecture of the configuration management platform for the DTT project aims at implementing the DTT assembly model in a unique environment able to exchange models and data even developed outside the platform ensuring the congruence of the design, the traceability of design changes and the adoption of a proper Systems Engineering approach.

Keywords: CAD management | Configuration management | DTT facility | PLM platform | Systems engineering | Technical integration

Abstract: The Product Lifecycle Management (PLM) systems lead the development of a product or a system from the early concept design until the end of the life allowing the knowledge management step by step. Among these systems, the 3DExperience platform adopts a Model Based Systems Engineering (MBSE) approach and allows to implement each phase of the design in a single co-simulation environment. This platform has been chosen for the development of the Divertor Tokamak Test (DTT) facility. The DTT tokamak, under construction at ENEA site in Frascati, has the main aim to contribute to the development of a reliable solution for power exhaust in a reactor, one of the major issues in the roadmap towards the realization of a nuclear fusion power plant. The divertor is one of the most challenging systems whose requirements coming from different physics and interfaces shall be balanced. The fixation system is the interface between the vacuum vessel and the divertor cassette body whose concept design has been carried out in a PLM system. This paper deals specifically with the application of the Requirement, Functional, Logical, Physical (RFLP) approach to the DTT divertor fixation system from the requirement elicitation and definition until the preliminary physical design, implementing each phase in the 3DExperience platform.

Keywords: Divertor Fixation System | DTT | MBSE | Requirements Management | RFLP

Abstract: The Divertor Tokamak Test (DTT) facility needs a large amount of heating power to study the problem of power exhaust in reactor-relevant conditions. Among the additional heating systems, the ion cyclotron resonance heating (ICRH) is characterized by radio frequency (RF) components based on standard technology and well-assessed solutions due to the tight schedule of the DTT construction. Considering the harsh fusion operating conditions, the ICRH antenna design involves different and interacting physical fields to be managed by the systems engineering (SE) approach. Therefore, following step by step this methodology, the design started with the definition of the main requirements of the whole system. Then, the main functions have been identified with the aim to define the logical architecture of the whole antenna structure. In the end, a preliminary 3-D parametric model of the ICRH antenna with its subsystems has been developed adopting a top-down modeling approach in the CATIA V5 environment provided by Dassault Systemes. Key aspects of the 3-D model are the clear definition of the position in the available space of all subsystems and of their interfaces, and its parametrization. They allow to quickly implement the modifications required by the multiple iterations between the geometrical modeling environment and several multiphysics simulation environments to check the compliance with mechanical, electrical, thermofluid dynamics, and remote handling requirements.

Keywords: 3-D parametric modeling | Antenna accessories | Antenna feeds | Antennas | ion cyclotron resonance heating (ICRH) antenna | Loaded antennas | Plasmas | Radio frequency | Solid modeling | systems engineering (SE) | virtual prototyping

Abstract: Systems Engineering allows to address the design of complex systems from the early stage until the end of its lifetime with the aim to realize successful systems. The intrinsic complexity of tokamak design requires to adopt Systems Engineering guidelines to write correctly and efficiently a large set of system requirements. Well-formed requirements would make efficient and consistent the downstream design, integration, and verification of a system. The process of requirements definition, conformed to Guide to System Requirements Definition recommended in fusion field, is far from simple and fast. The requirements definition phase encourages the early identification of issues that can be acted in the life cycle. This paper firstly highlights a new procedure to include requirements of a tokamak component in the requirement management tool of the whole system. This work identifies engineering requirements and constraints and describes their impact on the selection of the design principles of the EU-DEMO divertor system. The new identified procedure is developed using a participative approach involving experts belonging to different working groups.

Keywords: DEMO divertor | Requirements management | Systems engineering

Abstract: This research focuses on the requirements management phase in the conceptual stage following a Systems Engineering approach. The development of a parametric associative master model is useful to implement requirements and available knowledge in the CAD model. The vertical decomposition from higher level requirements to lower level requirements is carried out. The decomposition of design parameters follows the mapping process according to Axiomatic Design principles. The functional requirements and design parameters relations enable to develop the parametric associative master model. Modifications related to requirements can be automatically propagated to the down-stream geometries, maintaining the relationships among geometrical features in the following design steps to choose the optimal candidate. The case study deals with the mechanical design of nuclear fusion devices focusing on the improvement of the concept design of neutron shielding plates, a divertor subsystem added to satisfy a high level requirement about divertor shielding performances on vacuum vessel. Among several variants, a few feasible configurations are generated.

Keywords: DEMO | Divertor | Nuclear fusion engineering | Requirements management | Systems Engineering