Sn Strands Research Articles

A $\hbox{Nb}_{3}\hbox{Sn}$-Based, Model Superconducting Helical Undulator Fabricated Using a Wind and React Process

A model helical undulator 250 mm in length, with a period of 14 mm, was designed, fabricated and tested. The helical coil was wound with multifilamentary, internal-Sn type Nba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand. The 0.7 mm OD strand was insulated with S-glass, wound onto the former, and reacted, after which the coil underwent vacuum epoxy impregnation. The beam aperture was 7 mm, the winding bore diameter was 8 mm, and the OD of the complete winding was 18 mm. The helical poles were made from 1016 low carbon steel, and projected slightly above the coil pack, with an OD of 19.06 mm. The coil I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and the magnetic field in the bore were measured at 4.2 K in a liquid helium bath. The bore field was also measured as a function of position along the length of the undulator.

${\rm Nb}_{3}{\rm Sn}$ Strand Characterization for the Nijmegen 45 T Hybrid Magnet

The Nijmegen 45 T hybrid magnet will consist of an inner resistive 33 T resistive magnet and a superconducting 12 T outsert magnet. In the present conceptual design of the layer-wound outsert, the conductor is a Nb3Sn-Cu Cable-In-Conduit Conductor (CICC) with a stainless steel conduit, operating at 4.5 K by a forced flow of supercritical helium. At nominal magnetic field, the operating current is 12.3 kA. The outsert magnet design comprises 3 types of CICC design assuming a void fraction of 29 % and a temperature margin above 1.5 K. The design requires for 0.81 mm diameter Nb3 Sn strands a minimum copper fraction of 50% and a minimum equivalent critical current at 12 T, 4.2 K, ? = 0% of 590 A. A candidate strand considered is a Powder-In-Tube type of NbaSn conductor with 114 filaments and a copper fraction of 55 %. To predict the cable performance in terms of critical current, stability and AC loss under operational conditions to the best of present scaling capabilities, knowledge of the behavior of the critical current Ic(B, T, ?axial), magnetization M(B, dB/dt), stress-strain relation at 300 and 4.5 K and finally Ic as a function of periodic bending and temperature is required. These essential properties, as measured at the University of Twente employing the TiAIV Ic barrel, the PacMan and Tarsis strain devices as well as the integrating magnetometer, are presented and discussed.

Numerical simulation of critical current performance in Nb3Sn strand subjected to periodic bending deformation

AbstractIn the ITER Engineering Design Activity (EDA), four NB3Sn model coils were developed and successfully tested. However, it was revealed that the critical current of the conductor degraded with the increase of electromagnetic force. One of the explanations of this phenomenon is a strand bending caused by enormous electromagnetic force. The authors therefore developed a simulation code using the distributed circuit model to investigate dependency of the critical current performance on the periodic bending deformation. The simulation results were in good agreement with the experiments. The dependence of the critical current on the periodic transverse load, temperature, periodic load pitch, thickness of Ta barrier which prevents Cu stabilizer from being contaminated by Sn, twist pitch of the strand, and RRR of the bronze matrix was investigated using the developed code. The results showed that the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that the shorter cabling pitch and the larger bending stiffness prevent the critical current degradation. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 7–15, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20923

Test Results of the Third Japanese SULTAN Sample

Many full size conductors for the ITER TF coils have been tested at the SULTAN test facility in Switzerland for conductor qualification. JAEA tested two samples and two kinds of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands were evaluated through the tests. Now another sample named JATF3 has been tested, which uses two other kinds of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands. The strands satisfy the critical current density J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> requirement, but results of the conductor test were lower than our expectation. After the test, JAEA has been investigating the reason by X-ray CT scan and destructive inspection, and has found a possible reason.

Researches of Structure Formation Peculiarities in the Internal-Tin ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Strands

Addition of manganese in elements of matrix for internal-tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands has been investigated. Two types of multifilamentary strands with distributed source of tin, 1.8 wt.% Mn in elements of matrix before reaction heat treatment and 1 wt.% Mn in matrix after reaction, have been fabricated by internal-tin method. One of the produced strands had reinforced stabilizer from CuNb nanocomposite alloy. The increase of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn layer growth rate in superconductors filaments of manganese doped strands was determined. Microstructures of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn filaments after reaction heat treatment were investigated by SEM and TEM microscopes. The critical current density in magnetic fields up to 20 T, hysteresis losses, critical temperature and mechanical characteristics were measured. The increase of critical current density in internal-tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands with manganese doped matrix and the formation of fine microstructure Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn layers was revealed.

Quench Performance of a 4-m Long ${\rm Nb}_{3}{\rm Sn}$ Shell-Type Dipole Coil

Fermilab has finished the first phase of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn technology scale up by testing 2-m and 4-m long shell-type dipole coils in a dasiamagnetic mirrorpsila configuration. The 2-m long coil, made of Powder-in-Tube (PIT) Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand, reached its short sample limit at a field level of 10 T. The 4-m long coil, made of advanced Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand based on the Restack Rod Process (RRP) of 108/127 design, has been recently fabricated and tested. Coil test results at 4.5 K and 2.2 K are reported and discussed.

$J_{C}(B,T,\varepsilon)$ Parameterization for the ITER ${\rm Nb}_{3}{\rm Sn}$ Production

A number of models for the critical surface of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn, and in general A15 superconductors, have been developed in the past years. This paper compares the most common parameterizations using consistent notation. Although the parameterizations appear dissimilar at first sight, they are in reality all based on a fit of the normalized pinning force vs. the reduced field, and have similar scalings for the critical field and critical temperature based on a Unified Scaling Law. In this paper we take the various parameterizations as a basis for a generic scaling proposed for the characterization and production follow-up of the ITER Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands. The accuracy of the scaling is estimated using the fitting residuals on various sets of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> (B,T,epsiv) data available in literature. We discuss the results, and give our view of the work towards a unified, practical parameterization.

Heat Treatment Optimization Studies on PIT ${\rm Nb}_{3}{\rm Sn}$ Strand for the NED Project

For the Next European Dipole (NED) program, a Powder-In-Tube (PIT) strand was successfully developed by SMI. This high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand presents a non-copper critical current density of ~ 2500 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 12 T applied field and 4.2 K and a filament diameter around 50 mum. Extensive heat treatment optimization studies were performed in order to maximize both critical current and RRR, with a plateau temperature down to 625degC and duration up to 400 hours. It appears that a critical current enhancement of ~ 10% can be achieved for a reaction schedule of 320 hours at 625degC with non-copper critical current density respectively exceeding 2700 and 1500 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 12 and 15 T (4.2 K). Thanks to this modified heat treatment, this strand completely fulfills the NED stringent specification.

A Variable Temperature Walters Spiral Probe for the Critical Current Measurement of Superconducting Strands

We have developed a probe for the critical current measurements of low temperature superconducting strands at various field, temperature and strain. A 30 cm-long strand sample is soldered on a Walters spiral made of beryllium copper alloy and compressive or tensile axial strain can be applied up to 0.7%. Temperature control ability was tested using a MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wire up to 30 K. Three cernox sensors are attached on a spiral adjacent to the strand and the temperature of the spiral is controlled within plusmn50 mK of target temperature during the critical current measurement up to 80 A. Extensive critical current measurements have been carried out for an internal-tin processed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand. It was found that the measured field, temperature and strain dependence of the critical current for the internal-tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand is in agreement with the recent scaling law based on strong coupling theory of superconductivity.

Stability of ${\rm Nb}_{3}{\rm Sn}$ Superconducting Wires: The Role of the Normal Matrix

The stability of superconducting wires is a crucial issue in the design and operation of reliable superconducting magnets. High current density magnets, such as those presently developed for future accelerator projects, may be subject to premature quenches due to local releases of energy. In this paper we study the results of stability experiments that have been performed using a single mode Diode Laser with an optical fiber to illuminate the superconducting strand surface and trigger fast quenches. The development and propagation of laser-induced quenches have been measured on Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands in LHe bath by means of three voltage taps. This paper deals with the numerical analysis of the experimental results. A coupled electric and thermal model has been developed to study the quench propagation. The experimental evidence of a different qualitative behavior of the voltage traces recorded on strands with respect to NbTi strands is explained by means of a more detailed physical model of strands, that takes into account electrical and thermal transverse resistances.

Case Study of a 20 T-$\phi$400 mm Room Temperature Bore Superconducting Outsert for a 45 T Hybrid Magnet

The High Field Laboratory for Superconducting Materials (HFLSM) and the Tsukuba Magnet Laboratory (TML) conducted in collaboration a case study on development of a 50 T-class hybrid magnet. To construct a high magnetic field magnet with compact and energy-saving design as well as with easy operation and maintenance, one has to develop high-strength NbSn strand cables, with maximized superconducting characteristics and which can withstand a large electromagnetic force over 500 MPa. For this purpose, the HFLSM has proposed and investigated the effect of repeated bending treatment (pre bending) on NbSn strands internally reinforced with CuNb stabilizer leading to significant enhancement of the critical current density. In this report we present our results on application of the pre bending effect to the development of high-strength strand cables. The designed prebent-strand cables are composed of three CuNb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands (3 times Phi =1.73 mm) and four stainless steel strands ( 4 times Phi =1.73 mm). High-strength CuNb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand cables have shown a stress limit of 552 MPa at 0.4% strain, and a critical current of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> =1000 A at 18.5 T and 2.0 K. For such high-strength strand cables, a 20 T superconducting magnet with a room temperature bore (Phi =400 mm) consisting of five layers made of CuNb/NbSn and two layers of NbTi was designed. The coil parameters are: inner diameter Phi = 440 mm, outer diameter Phi = 1332 mm, coil height 1321 mm, inductance 350 H and magnetic stored energy 144 MJ at 908 A of the operation current. Winding of the coil was experimentally successfully simulated using dummy 3 + 4 strands cable composed of three Cu strands and 4 stainless steel strands with a similar design to the 3 + 4 strands superconducting cable presented above. The 20 T superconducting coil will be used as a 20 T outsert for a 25 T water-cooled resistive insert to obtain a 45 T hybrid magnet.

Review of the Results of the ITER Toroidal Field Conductor R&amp;#x00026;D and Qualification

An R&D program is being carried out in view of the qualification of the Toroidal Field (TF) coil conductor. It consists of an extensive characterization of several Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand candidates, the cabling of those strands into prototype TF conductors with various combinations of twist pitch and void fraction and the measurement of the performance of conductor short samples in representative condition of transport current, magnetic field and temperature. Industries and laboratories are involved worldwide in this R&D program which is expected to provide the basis to finalize the TF conductor design. The Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands proposed by each of the six Participant Teams involved in the procurement of the TF conductor will then be qualified in the final cable configuration by the successful test of a short sample in the Sultan facility. The status and the first results of the R&D program are presented together with the qualification plan.

Effects of Cr Diffusion on $RRR$ Values of Cr-Plated Nb$_{3}$Sn Strands Fabricated by Internal-Tin Process

Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands which will be used for the ITER TF coils should be chrome plated thickness of 1.8 mum to reduce AC loss and improve the thermal stability of cable. During heat treatment, the RRR value can be affected by Cr diffusion. In this work, the effect of Cr diffusion was systematically studied, using the KSTAR and ITER candidate strands. For the KSTAR strand, the Cu/non-Cu ratio was systematically varied from 1.53 to 0.69 by chemical etching whereas the samples were heat treated by the same schedule. For the ITER candidate strand, on the other hand, the Cu/non-Cu ratio was fixed to the specification value of 1.0, and the variation of the RRR value was studied with respect to the heat treatment schedule, especially the retention time of the 650degC plateau was varied from 100 to 200 hours. It was also compared with the Cr diffusion distance obtained from EPMA (electron probe microanalysis). We found that the RRR value of the ITER candidate strand becomes lower than the ITER requirement of 100, if the heat treatment at 650degC is longer than 200 hours. The RRR can be reached up to 161 when the duration of 650degC plateau is reduced to 100 hours, while satisfying all other ITER requirements including the critical current density.

Results of a New Generation of ITER TF Conductor Samples in SULTAN

A new generation of ITER TF conductor samples has been assembled and tested in SULTAN in 2007 following a common procedure agreed among the ITER parties. The test results of six SULTAN samples, made of twelve conductor sections manufactured in Europe, Japan, Korea and Russia, are reported here. The conductor layout reflects the ITER TF conductor design, with minor differences for the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand characteristics, void fraction and twist pitch. The object of the test is a straight comparison with the ITER requirement of 5.7 K current sharing temperature at 68 kA current and 11.3 T field. A broad range of behavior is observed.

Magnetization, RRR and Stability of ${\rm Nb}_{3}{\rm Sn}$ Strands With High Sub-Element Number

The magnetization and low field stability were measured on a series of high current-density Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands with 54 to 198 sub-elements taken from accelerator magnet development programs. The effective filament size, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d_eff </i> ,, as determined from the width of the magnetization loop at low field and the extrapolation of the transport critical current from high field, was very close to the sub-element diameter determined by the strand geometry. Self-field corrections were vital for obtaining this agreement; without them, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d_eff </i> was overestimated by ~25%. While all strands, even those with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d_eff </i> as small as 35 mum, exhibited flux-jumps at low field in magnetization measurements, smaller sub-elements produced smaller flux-jump magnitude and a smaller range of field over which flux jumps occurred, suggesting stability improved with decreasing <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d_eff. </i> . However, good combinations of the residual resistivity ratio <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RRR</i> and the critical current density became increasingly difficult to obtain by varying the reaction heat treatment as the sub-element number increased. Further analyses of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RRR </i> data indicate that tin contamination of the copper stabilizer is underway even before any Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn is formed in strands with high numbers of sub-elements.

Critical-Current Measurements on ITER ${\hbox{Nb}}_{3}{\hbox{Sn}}$ Strands: Effect of Temperature

Transport critical-current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) measurements were made on commercial multifilamentary Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands at temperatures (T) from 4 to 17 K and magnetic fields (H) from 0 to 14 T. Samples investigated were taken from the stage 1 pre-production strand for the central solenoid of the International Thermonuclear Experimental Reactor (ITER) project. Specimens were mounted on a three-turn Ti-6Al-4V (percent by mass) mandrel, which was a shorter version of the standard ITER critical-current mandrel. The measurements covered the range of critical currents from less than 0.1 A to over 700 A. To verify the accuracy of the variable-temperature measurements, we compared critical-current values obtained on a specimen that was immersed in liquid helium at 5 K to those measured on the same specimen in flowing helium gas at the same temperature. This comparison indicated that specimen temperature was controlled to within 60 mK during the measurements. The critical-current data presented include electric-field versus temperature (E-T) characteristics, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (T) at constant H, and extrapolated effective upper critical field as a function of temperature. These data are part of what is needed for the ITER strand characterization.

Analysis of DC Properties and Current Distribution in TFAS ITER Conductor Samples Using High ${\rm J}_{\rm C}$${\rm Nb}_{3}{\rm Sn}$ Advanced Strands

Two full-size conductor samples using advanced Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands were tested in the SULTAN facility in 2005-2006 within (I,B,T) ranges close to the ITER operating conditions (B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> ~ 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> 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 subcables (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 subcables. 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.

Spatial Periodic Bending and Critical Current of Bronze and PIT ${\rm Nb}_{3}{\rm Sn}$ Strands in a Steel Tube

We measured the influence of spatial periodic bending on the critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands that were tightly swaged in a steel tube, imposing a compressive strain, in attempt to simulate the conditions representative for an ITER (international thermonuclear experimental reactor) cable in conduit conductor (CICC). The huge electromagnetic transverse force causes both transverse compressive strain in the strand crossover contacts and bending strain on top of the strain induced by the differential thermal contraction of the various conductor components. For a CICC with stainless steel or Incoloy conduit, the effect of the thermal cool-down strain on the reduction in performance due to periodic bending strain is unknown. We performed periodic bending tests in the TARSIS facility (test arrangement for strain influence on strands) on three samples. The degradation of the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> due to bending appears to be much more severe for a strand swaged in a stainless steel tube than straightforward simulated by available models assuming simply axial strain dependency. It is confirmed by AC loss measurements that the extra degradation can not be attributed to a change in matrix transverse resistivity, possibly affecting the current transfer length, so we believe this is related to the three-dimensional strain state of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn layer.

Development of Rutherford-Type Cables for High Field Accelerator Magnets at Fermilab

Fermilab's cabling facility has been upgraded to a maximum capability of 42 strands. This facility is being used to study the effect of cabling on the performance of the various strands, and for the development and fabrication of cables in support of the ongoing magnet R&D programs. Rutherford cables of various geometries, packing factors, with and without a stainless steel core, were fabricated out of Cu alloys, NbTi, Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al, and various Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands. The parameters of the upgraded cabling machine and results of cable R&D efforts at Fermilab are reported.

Scaling of the $E(J)$ Characteristics in the ITER Type ${\rm Nb}_{3}{\rm Sn}$ Strands in Relation to the Applied Strain and Magnetic Field

Voltage- current characteristics VCC(epsiv, B, 4.2 K) have been measured in the range of the applied axial tensile strain (epsiv) from 0% to 0.93% at magnetic fields 10 T and 12 T for ITER type bronze processed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand and for similar strand with enhanced mechanical strength in which part of stabilizing copper was replaced by high strength high conductivity microcomposite Cu-Nb material. The results of description of the electric field-current density characteristics E(J,epsiv,B,4.2 K) are presented. To describe experimental database E( J) versus strain and magnetic field the relation is used containing four fitting parameters. Three parameters,namely: C, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (0) and B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c2</sub> (0, epsiv) describe. Additional parameter characterizes the smoothness of E( J). Good agreement of experiment and calculation has been obtained.