[en] Various tests, either on full-size joint samples or on model coils confirmed that current distribution may play a crucial role in the electrical behaviour of CICC in operating conditions. In order to evaluate its influence, CEA developed a code (ENSIC) the main feature of which is a CICC electrical model including a discrete resistive network associated with superconducting lengths. Longitudinal and transverse resistances are also modeled, representing either joint or conductor. In our paper we will present the comparison of experimental results with ENSIC calculations for one International Thermonuclear Experimental Reactor (ITER) sample prototype relevant to poloidal field (PF) coils: the PF-full-size joint sample (PF-FSJS). In this purpose, the current distribution has been measured thanks to a segmented Rogowski coils system. Current distribution effects on the basic characteristics (T_CS, n-value etc) of the cable compared to single strand will be discussed. This study aims at putting light on the global strand state in a conductor and is also useful to evaluate some intrinsic parameters hardly measurable (effective interpetal transverse contact resistance for example) allowing further application in coils

[en] Using the SULTAN test facility the d.c. behaviour of three subsize NbTi cable-in-conduit (CIC) conductors has been studied. The d.c. performance of the cables is compared with the critical currents and the current sharing temperatures expected from the strand data. As a basis for this comparison the critical current of the NbTi strands has been measured in the temperature range of 4.2-6.5 K in magnetic fields of up to 7.5 T. The d.c. performance of the NbTi subsize conductors has been found to be not significantly affected by cyclic loading. Taking into consideration the self field of the conductor the cable critical current and the current sharing temperature are in agreement with the strand data

[en] The ITER toroidal field coil system generates a toroidal field in the plasma region of an intensity of 5.7 T. During operation the toroidal field coils experience an electromagnetic load toward the machine axis. This load is resisted by the central structure. The in-plane hoop forces of the coils are carried by a winding pack and case. This paper concentrates on a calculation of the local stress distribution in the insulation, conductor jacket, and steel structure in the most highly stressed region of the winding pack

[en] In the framework of the conductor optimisation task (CONDOPT) five NbTi subsize cable-in-conduit conductors with parametric variations were fabricated. The DC performance of these conductors tested in the SULTAN test facility [IEEE Trans. Appl. Supercond. 12 (2002) 520] and the strand properties including the voltage-current characteristic, are compared. The results clearly indicate that the current carrying capacity of the conductors is considerably reduced due to the self-field. In conductors with a hindered interstrand current sharing, the critical current has been found to be even below the predicted value at the peak field, suggesting an uneven current distribution among the strands

[en] Within the research program on the International Thermonuclear Experimental Reactor (ITER) Poloidal Field (PF) coils, a full size conductor sample was tested in the SULTAN facility (CRPP Villigen, Switzerland). This sample is composed of two straight ITER-like cable-in-conduit conductors, using the same NbTi strand. The two conductors are identical except for one leg makes use of a cable containing steel wraps around the main sub-cables as in the ITER design, while the other has no wraps inside. The paper presents conductor DC tests results compared to predictions given by various models developed within ITER-associated laboratories. These models aim to predict the DC behaviour of the cable from the experimental performances of the single strand. They have to explain the observed voltage-current (V-I) or voltage-temperature (V-T) characteristics, including the thermal runaways. The lower experimental performances compared to all expectations have shown the necessity to revise the models and to introduce a possible uneven current distribution among the strands of the cables. (authors)

[en] The US Domestic Agency is one of six parties supplying TF cable-in-conduit conductors (CICCs) for ITER. Previous tests have shown that measured performance of the TF CICCs can be much lower than expected from the strand properties at the projected uniaxial strain and that the cabling pattern may also be an important factor. Worst of all, voltage signals well below the expected critical surface could not be reliably interpreted or canceled, making test results very suspect. The TFUS1 sample was prepared to achieve multiple goals: (1) to ensure uniform current distribution and to eliminate parasitic voltage signals by improving joints, (2) to explore the potential benefits of a different cabling pattern for better support of strain-sensitive strands, and (3) to explore the source of voltage development in the cable through the use of innovative penetrating diagnostics. Test results of the first US-made samples are presented and discussed

[en] The ITER poloidal field (PF) coil system consists of a central solenoid coil and seven ring coils. The PF coils must provide the magnetic fields to confine the plasma and control its position during the various phase of operation including plasma initiation, ramp-up, burn and shut-down. They contribute the magnetic flux change to ramp up the plasma current and a part of the flux change to maintain it. This paper describes the requirements and the conceptual design for the seven outer PF coils

[en] During the first test campaign of the 60 kA HTS cable prototypes in the EDIPO test facility, the feasibility of a novel HTS fusion cable concept proposed at the EPFL Swiss Plasma Center (SPC) was successfully demonstrated. While the measured DC performance of the prototypes at magnetic fields from 8 T to 12 T and for currents from 30 kA to 70 kA was close to the expected one, an initial electromagnetic cycling test (1000 cycles) revealed progressive degradation of the performance in both the SuperPower and SuperOx conductors. Aiming to understand the reasons for the degradation, additional cycling (1000 cycles) and warm up-cool down tests were performed during the second test campaign. I_c performance degradation of the SuperOx conductor reached ∼20% after about 2000 cycles, which was reason to continue with a visual inspection of the conductor and further tests at 77 K. AC tests were carried out at 0 and 2 T background fields without transport current and at 10 T/50 kA operating conditions. Results obtained in DC and AC tests of the second test campaign are presented and compared with appropriate data published recently. Concluding the first iteration of the HTS cable development program at SPC, a summary and recommendations for the next activity within the HTS fusion cable project are also reported. (paper)

[en] Coated conductors could be promising materials for the fabrication of the large magnet systems of future fusion devices. Two prototype conductors (flat cables in steel conduits), each about 2 m long, were manufactured using coated conductor tapes (4 mm wide) from Super Power and SuperOx, with a total tape length of 1.6 km. Each flat cable is assembled from 20 strands, each strand consisting of a stack of 16 tapes surrounded by two half circular copper profiles, twisted and soldered. The tapes were measured at 12 T and 4.2 K and the results of the measurements were used for the assessment of the conductor electromagnetic properties at low temperature and high field. The two conductors were assembled together in a sample that was tested in the European Dipole (EDIPO) facility. The current sharing temperatures of the two conductors were measured at background fields from 8 T up to 12 T and for currents from 30 kA up to 70 kA: the measured values are within a few percent of the values expected from the measurements on tapes (short samples). After electromagnetic cycling, T _c_s at 12 T and 50 kA decreased from about 12 K to 11 K (about 10%), corresponding to less than 3% of I _c. (paper)

[en] Two full-size conductor samples using advanced Nb₃Sn strands were tested in the SULTAN facility in 2005-2006 within (I,B,T) ranges close to the ITER operating conditions (B_MAX ∼ 12 T, T ∼ 5 K). Each sample includes two conductor legs, connected together by a twin-box joint in their lower part. The conductor design is the same for the four legs, similar to that of the ITER Toroidal Field Model Coil, but each leg uses specific strands newly developed and industrially produced to reach higher J_c performances than in previous samples. In addition to classical voltage taps and temperature sensors, the sample instrumentation included Hall probe (HP) heads positioned so as to discriminate current distribution between conductor main sub-cables (petals). In a first simple approach, we analyse the results supposing that the conductor drives a uniform current among strands. The model is mainly based on geometrical considerations associated with a global approach on strand mechanical behavior. In a second part, we model the conductor in a more realistic way with different currents shared between main sub-cables. Taking into account various geometrical aspects (spiral trajectories, precise self-field maps...) the current in all petals are reconstructed with help of HP's signals, expected to experience self-field from CICC's. The mechanical aspects are also tentatively considered (electromagnetic load, bending strain...). Global results for both samples are shown, and possible inaccuracies due to geometrical parameters (petals positioning) are discussed. Those data are then injected into a Matlab program for electrical and geometrical CICC modeling (derived from the previous ENSIC code from CEA) and compared with dedicated experimental runs. Results are finally commented on the basis of overall consistency with HP's signals. (authors)