Analysis of the Thermal-Hydraulic Effects of a Plasma Disruption on the DTT TF Magnets

The Divertor Tokamak Test (DTT) facility, a fully superconducting nuclear fusion reactor being built in Italy, will contribute to address the power exhaust problem in EU DEMO perspective. A lot of flexibility of operation will be demanded to the machine, which should be capable to tackle also severe transients such as plasma disruptions. In this work, the 4C thermal-hydraulic code is used to compute the temperature margin during a plasma disruption, using as input the heat generated into the Toroidal Field coil casing and transferred to the winding pack, and the possibility that this leads to a quench of the magnet is studied. The results of the analysis will give important feedbacks for the design of the quench protection system, e.g., avoiding to trigger a fast current discharge right after the disruption, as well as for the machine operation, e.g., assessing the required re-cooling time of the magnets after a disruption

Frequency response analysis of a toroidal field coil of the divertor tokamak test facility

The magnet system of the Divertor Tokamak Test (DTT) facility is mainly made up with superconducting coils. During the operation of the DTT machine, high voltages will appear across each Toroidal Field Coil (TFC) when fast current will ramp down; the reason why, a reliable electrical insulation is required for the operation of the TFC system. With the aim of checking the correct sizing and implementation of the electrical insulation, different DC and AC electrical tests will be performed during all the coil manufacturing process. Among these, the impedance spectrum test, or rather the complex impedance measurement over several decades of frequency range, can be used to analyze the frequency response of the coil. The variations of the resonance frequency (f0), during its electrical acceptance test, can be useful to make predictions about the detectability of internal failure conditions in a coil. This paper focuses on analysis of the frequency response of a TFC, using a numerical simulation approach. The goal is to assess the impedance spectrum of a TFC within a fixed frequency band by a frequency-dependent lumped network. Starting from the TFC layout, a WP with the casing has been modeled by a complex network of lumped parameters in Ansys 2021/R2 environment. The data (amplitude and phase angle vs frequency) obtained have been used to study the f0 variation during the different manufacturing stage of the WP. This model will be able to make predictions about the detectability of internal short-circuit in a TFC

DTT - Divertor Tokamak Test facility: A testbed for DEMO

The effective treatment of the heat and power exhaust is a critical issue in the road map to the realization of the fusion energy. In order to provide possible, reliable, well assessed and on-time answers to DEMO, the Divertor Tokamak Test facility (DTT) has been conceived and projected to be carried out and operated within the European strategy in fusion technology. This paper, based on the invited plenary talk at the 31st virtual SOFT Conference 2020, provides an overview of the DTT scientific proposal, which is deeply illustrated in the 2019 DTT Interim Design Report

DTT - Divertor Tokamak Test facility - Interim Design Report

The “Divertor Tokamak Test facility, DTT” is a milestone along the international program aimed at demonstrating – in the second half of this century – the feasibility of obtaining to commercial electricity from controlled thermonuclear fusion. DTT is a Tokamak conceived and designed in Italy with a broad international vision. The construction will be carried out in the ENEA Frascati site, mainly supported by national funds, complemented by EUROfusion and European incentive schemes for innovative investments. The project team includes more than 180 high-standard researchers from ENEA, CREATE, CNR, INFN, RFX and various universities. The volume, entitled DTT Interim Design Report (“Green Book” from the colour of the cover), briefly describes the status of the project, the planning of the design future activities and its organizational structure. The publication of the Green Book also provides an occasion for thorough discussions in the fusion community and a broad international collaboration on the DTT challenge

Test of the MF-CICC Conductor Designed for the 12-T Outsert Coil of the HFML 45-T Hybrid Magnet

A 45-T hybrid magnet is being built at the High Field Magnet Laboratory of the Radboud University in Nijmegen, The Netherlands. The hybrid magnet consists of a 12-T cable-in- conduit-conductor (CICC) Nb 3Sn superconducting outsert and a 33-T resistive insert magnet. To verify the CICC design, a thorough testing has been completed in the SULTAN facility at Swiss Plasma Center, EPFL in Villigen (Switzerland) for the medium- grade conductor of the outsert. In two test campaigns, the dc cable performance (current-sharing temperature, critical current), the ac loss, and the conductor's performance stability during cyclic loading and after one warmup and cooldown cycle have been investigated. Two different cable layouts were tested - one with a very short twist pitch (STP) and the second one with a long twist pitch (LTP) cabling pattern. As both conductors were made of the same Nb 3Sn strand and underwent the same heat treatment and sample preparation procedure, the effect of the twist pitch on the ac loss and on the dc performance with respect to cyclic loading could be reliably evaluated. The test results show that both cable layouts are actually very robust. The cable could withstand 2000 load cycles and the warmup and cooldown cycle without any significant degradation of the dc performance, and even the overloading at BI product (field multiplied by current) approximately two times larger than those foreseen during magnet operation did not lead to a big performance change. Small differences between the STP and LTP options have been observed, indicating that the STP conductor withstands high electromagnetic loads better than the LTP one. © 2002-2011 IEEE

Cable-in-conduit conductors: lessons from the recent past for future developments with low and high temperature superconductors

We review progress in the design of high field superconducting cable-in-conduit conductors (CICCs) for fusion applications, with special attention to the results of recent key experiments, leading to the state-of-the-art CICC technology: the ITER Toroidal Field and Central Solenoid programs, the EFDA Dipole conductor development program, the NHFML Hybrid Magnet project, the EU-TF Alt conductor demonstration, and the CRPP React & Wind flat cable test. For these projects, the main CICC design driver was the mitigation of Nb3Sn conductor performance degradation with electro-magnetic loading cycles. This was achieved by proper choice of cable layout and of conductor geometry, depending on the specific operating conditions and project requirements. In all cases, the necessity to limit cable movements inside the conductor jacket was identified to be of crucial importance. The main aspects of CICC manufacture are also discussed here, at least for what is the experience gained by the authors in both CICC jacketing and cabling processes. Finally, the state of the art of high-temperature superconducting (HTS) cables is discussed: at present, this technology is still in its infancy, but it is highly likely that major technological improvements could eventually lead to a widespread use of HTS CICCs. © 2015 IOP Publishing Ltd