Publications de Boris Stepanov

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Two kinds of anomaly, observed in the Volt-Ampere Characteristic (VAC) of large NbTi cable-in-conduit conductors (CICC) are discussed. In one case, the wavy behavior of the VAC close to the current sharing range is explained with oscillations of the coolin ...

A Nb3Sn based, React&Wind flat cable, named RW2, was developed in the past three years at the Swiss Plasma Center in the scope of the EUROfusion conceptual studies for DEMO. The test results presented earlier proved an excellent DC performance, but large e ...

Within the framework of the R&D studies for the International Thermonuclear Experimental Reactor (ITER) project, the first full size NbTi conductor sample was fabricated industrially and tested in the SULTAN facility (Villigen, Switzerland). This sample (PF-FSJS), which is relevant to the poloidal field coils of ITER, is composed of two parallel straight bars of conductor, connected at the bottom through a joint designed according to the CEA twin-box concept. The two conductor legs are identical except for

The Japan Atomic Energy Agency (JAEA) developed ITER TF Nb3Sn conductors that fulfill ITER requirements and has commenced fabricating the conductors to be used in the ITER TF coils. As a qualification of conductor fabrication, two full-size conductor sampl ...

An imbalance in the transport current among the strands of a Cable-in-Conduit conductors (CICC) can be associated with the change of their performance. In order to understand and improve the performance of CICC's, it is essential to study the current imbalance. This paper focuses on the study of the current imbalance in two short samples of the SeCRETS (Segregated Cooper Ratio Experiment on Transient Stability) conductors subjected to a cyclic load in the SULTAN facility. The self field around the conductor

An R&D program at CRPP investigates the design of large size Nb3Sn conductors, with the aim to improve the effectiveness and hence the cost of large size, force flow conductors. A design based on a solder filled flat cable, by react wind method, is selecte ...

The index n of the voltage-current characteristic of large superconductors is a crucial parameter to assess the allowed range for coil operation. In the tests of the Insert coils at the CSMC as well as in the short sample test in the SULTAN facility, it is observed that the index n dramatically decreases from the Nb3Sn strands extracted from cable-in-conduit provide the evidence of a permanent performance drop in the strands, likely due to the transverse load accumulation at the strand crossovers in the cab

Within the R&D 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 ...

The toroidal Field Conductor Insert (TFCI) coil was tested at 46 kA in the 13 T background magnetic field generated by the Central Solenoid Model Coil. The single layer TFCI coil uses a Nb3Sn cable-in-conduit conductor in a Titanium jacket. The object of this work is to verify the data self-consistency, and to apply a thermal, hydraulic and electrical simulation to derive the strand performance in the cable. We present the results of the analysis in support of the interpretation of a subset of current shari

Current reconstruction in cable-in-conduit conductors (CICC) cables is a crucial issue to determine cables performance in working conditions, and must be performed using inverse problem approaches as direct measurement is not feasible. The current distribu ...

The Poloidal Field (PF) coils of the International Thermonuclear Experimental Reactor (ITER) are designed using of NbTi cable-in-conduit conductors carrying a current up to 45 kA. Each PF coil consists of several modules Wound in double pancakes. Joints co ...

Two Nb3Sn cable-in-conduit conductors have been manufactured with identical non-Cu cross sections and the stabilizer either included in the Nb3Sn composite or partly segregated as copper wires. The two conductors are series connected and wound as a bifilar, single layer solenoid! assembled in the high field bore (11 T) of the SULTAN test facility. Beside the De: and AC losses characterization, the key tests include stability under pulsed transversal field (dB/dt up to 180 T/s), at DC operating current up to

An evolution of the contact resistances (R-c) of two full-size ITER (International Thermonuclear Experimental Reactor) cable-in-conduit conductors (CICC) aimed for the Poloidal Field Conductor Insert (PFCI) was studied in the Twente Cryogenic Press. The co ...

Within the EFDA technology program, CRPP designed and prepared a short length of full size Nb3Sn developmental conductor to be tested in the SULTAN test facility. Nb3Sn strand with a higher specification and low Cu:non-Cu ratio was supplied by Outokumpu. Half of the produced wire length has been Cr-plated half was left bare. Subsequently, two Ti-jacketed cable-in-conduit conductors based on a braid as the first stage, have been manufactured by VNIIKP. After reaction heat treatment, the annular space of the

Methods have been developed to study the distribution of the transport current among the strand bundles of cable-in-conduit conductors (CICC) by using self-field measurements with Hall probe arrays. The unbalance in the transport current is mainly caused b ...

In the frame of the conceptual design studies for the Toroidal Field (TF) coils of DEMO, a solution based on a layer-wound magnet, rectangular-shaped Cable-in-Conduit conductors and W&R manufacturing approach, is being developed. The feasibility and perfor ...

A. parametric study of the ac loss behavior and the stability of 3 NbTi subsize cable-in-conduit conductors has been performed in the SULTAN test facility. Two of the conductors are distinguished only by the SnAg and the Ni coating of the strands. The effective transverse resistance in the SnAg conductor is considerably. lower than that found for the conductor with Ni coated strands. Hence, the coupling loss in the SnAg coated conductor is considerably higher than, that in the Ni coated conductor. Cyclic lo

The measurement of the actual thermal strain, epsilon th, in a cable in conduit conductor (CICC) of Nb3Sn is of paramount importance to predict the CICC performance in operation starting from the strand scaling laws for the critical current density J(c)(B, ...

In the scope of the design activities for a 12.5 T dipole magnet, a short length of cable-in-conduit conductor (CICC) with steel jacket was prepared in spring 2005 as a pre-prototype of the high field dipole conductor. The small, rectangular conductor uses ...

Two subsize, Nb3Sn cable-in-conduit conductors, are tested as short samples in the SULTAN test facility. Transverse load is applied by sweeping up and down the operating current in high background field. A serious performance loss of I, and n-factor is observed upon cyclic load, with a drop of the critical current, I-c, larger than 30%. The results are critically discussed and compared to similar findings from the literature. The impact of the cyclic load on the Nb3Sn CICC performance must be carefully eval

Boris Stepanov

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Anomalies on V-I characteristic of NbTi cable-in-conduit conductors

A New Cabled Stabilizer for the Nb3Sn React&Wind DEMO Conductor Prototype

Test results on the first 50 kA NbTi full size sample for the International Thermonuclear Experimental Reactor

Test Result of a Full-Size Nb3Sn Conductor Developed for the ITER TF Coils

Self field measurements by hall sensors on the SeCRETS short sample CICC's subjected to cyclic load

Test results of a large size, forced flow Nb3Sn conductor, based on a design alternative to the cable-in-conduit

The voltage/current characteristic (n index) of the cable-in-conduit conductors for fusion

DC performances of ITER NbTi conductors: Models vs. measurements

Analysis and interpretation of Tcs tests of the ITER Toroidal Field Conductor Insert

DC and transient current distribution analysis from self-field measurements on ITER PFIS conductor

A low cost joint for the ITER PF coils, design and test results

Test results of SeCRETS, a stability experiment about segregated copper in CICC

Effect of cyclic loading and conductor layout on contact resistance of full-size ITER PFCI conductors

An alternative CICC design aimed at understanding critical performance issues in Nb3Sn conductors for ITER

Reconstruction of current unbalance in full-size ITER NbTiCICC by self-field measurements

Design and Characterization of the Interlayer Joint Between Low-Field Nb3Sn Conductors of a Layer Wound DEMO TF Coil

Parametric studies of subsize NbTi cable-in-conduit superconductors for ITER-FEAT

In situ Tc measurements of cable in conduit conductors via an inductive method

Test results of a small size CICC with advanced Nb3Sn strands

Performance evolution of Nb3Sn cable-in-conduit conductors under cyclic load