Design of JT-60SA Magnets and Associated Experimental Validations

Coupling losses induced in cable-in-conduit conductors (CICC) when subject to a time-varying magnetic field are a major issue commonly encountered in large fusion tokamaks (e.g., JT-60SA, ITER, DEMO). The knowledge of these losses is crucial to determine the stability of CICC but is yet difficult to achieve analytically (thus in a short computation time) given the specific and complex architecture of these conductors although numerical solutions such as THELMA and JACKPOT already exist. In an attempt to ease the resolution of this problem, we have previously presented a theoretical generic study of a group of elements twisted together (representing a cabling stage of a CICC) and derived the analytical expression of its coupling losses. We have now extended this study to a two cabling stage conductor by establishing an analytical model to calculate its coupling losses as function of its effective features. In a second part, we compare our results to these of THELMA and JACKPOT on geometries representing ITER CS and JT-60SA TF conductors. Finally, we have set up a specific algorithm to reconstruct strand trajectories from X-ray images and have extracted the effective geometrical parameters of a JT-60SA TF conductor. Our next objective is then to extract its effective electrical parameters from interstrand resistivity measurements to be able to compare the coupling losses predicted by our analytical model with those measured within the SULTAN facility.

Section: Parameters Extracted From X-ray Tomographymentioning

confidence: 80%

Development of a New Generic Analytical Modeling of AC Coupling Losses in Cable-in-Conduit Conductors

Louzguiti¹,

Zani²,

Ciazynski³

et al. 2018

“…As a result optimized features for NbTi and Cu strand were agreed between F4E and FEC while the activity framework was modified accordingly. As a result the final NbTi strand specifications were agreed to ensure an increased temperature margin with respect to the initial one [3] by about 0.1 K. The final specifications can be seen in next section (Table I).…”

Section: A General Overviewmentioning

confidence: 98%

“…After successive optimization along the past few years [2] and a recent definition of general specifications [3] which were used for the call for tender issued by F4E, a NbTi strand baseline design was proposed by FEC. In the very early stages of production activity, a conceptual optimization was led by F4E to put in place a risk mitigation strategy.…”

Section: A General Overviewmentioning

confidence: 99%

Starting EU Production of Strand and Conductor for JT-60SA Toroidal Field Coils

Zani¹,

Barabaschi²,

Peyrot³

2012

Self Cite

Included in the Broader Approach (BA) treaty, the JT-60SA project foresees to upgrade the existing JT-60U tokamak by substituting superconducting magnets to the present resistive magnets system. For this, a bilateral EU-JA procurement agreement drives EU, represented by Fusion for Energy (F4E) entity, to procure in-kind the totality of the 18 JT-60SA Toroidal Field (TF) Coils. Being almost the totality of the in-kind procurement of F4E for JT-60SA, the TF conductor manufacture monitoring is directly held by F4E, finalized by a delivery of components to collaborative EU institutes (CEA and ENEA) for its transformation into TF coils [1].The organization of TF conductor procurement lies on two contract placed in December 2010 by F4E to industrial operators for strand manufacture on one side and cabling-jacketing transformation on the other side. After a general overview the present paper describes the different steps reached up to the present state of fabrication achievement. The status of the ongoing manufacture and the foreseen next steps targeted in the near future will also be mentioned.

“…In particular, the design of fusion magnets, usually based on Cable-in-Conduit conductors, and the requirement of the minimum temperature margin, translates into a requirement for the basic NbTi wires of minimum superconducting performances at relatively high magnetic field and temperature, typically in the range to 6 T, to 6.5 K [1]- [6]. As already shown and discussed [7]- [9], the prediction of strand performances in this range, can hardly be inferred from simple tests at, for example, liquid helium temperature.…”

mentioning

confidence: 99%

Test Results of a NbTi Wire for the ITER Poloidal Field Magnets: A Validation of the 2-Pinning Components Model

Muzzi

Marzi

Zignani

et al. 2011

Self Cite

A two-components model has been recently developed, for describing the normalized bulk pinning force curves and the critical current density of NbTi strands over a wider B-T range with respect to conventional single-component models. The model was previously successfully applied to data collected on several NbTi commercial strands, with different size, Cu:nonCu ratio, filament diameter and layout, thus confirming the presence of two different pinning mechanisms in conventionally processed NbTi wires. For a further validation, we have extensively tested a strand recently produced by the Chinese Company Western Superconducting Technologies for the ITER Poloidal Field (PF) magnets PF2 to PF5, and applied the model to these data. In order to take into account the observed non-scaling with temperature of the reduced pinning force curves, the model has been updated, including the observed difference in the temperature dependences of the two components contributing to the overall bulk pinning force. The importance of testing wires over very wide temperature ranges is evidenced, and the good agreement between experimental and fit results validate the proposed formulation, which can be regarded as a reliable tool for the description of NbTi performances, to be used in the design of superconducting magnets. From the phenomenological point of view, it is shown that at low temperatures, the two pinning mechanisms contribute to the bulk pinning force, resulting in a pinning force peaking at a reduced field . As the temperature increases, the pinning force peak moves to lower fields, indicating that the low field component pinning mechanism becomes dominant.