Rutherford-type Cables Research Articles

FFT-Based Approach for the Mechanical Analysis of Superconducting Rutherford-Type Cables

Low-temperature superconductors are widely used in high field accelerator magnets, mostly within Rutherford type cables. We have proposed the “CoCaSCOPE” approach in order to build a numerical model of impregnated low-temperature Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting Rutherford-type cables dedicated to mechanical computation. Here the strand structure is described as a bi-metallic material: a copper core, a superconducting bundle region and an outer copper ring. In this paper, we explore the use of the distributed solver AMITEX_FFTP based on Fast Fourier Transform (FFT). The main interest of this method is to reduce the simulation time. This approach is investigated for structures with linear material behavior in this paper. This work compares the results from the FFT approach (using AMITEX) and from the 3D Finite Elements approach (using Cast3M). In this way, we can demonstrate the higher performances of FFT-based solving method compared to the finite elements method for multi-scale structure such as Rutherford-type cables in terms of computation time. With this approach, we can reduce the computation time or, alternatively, increase the size of our models in order to analyze the behavior of a macroscale model under mechanical solicitation.

Onset of Mechanical Degradation due to Transverse Compressive Stress in Nb3Sn Rutherford-Type Cables

In the framework of the High Field Magnets program at CERN, lower limits of degradative mechanical loads on reacted and impregnated Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford-type cables are being studied with the goal of optimizing the pre-stress applied at room temperature on the accelerator magnets. Coils are loaded during assembly, for instance when transverse load is applied by using a collaring press or the bladder and key technique. Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn is susceptible to transverse compressive stress, which is the loading condition investigated for this study. The purpose of this work is to identify the maximum pressure that can be applied, at room temperature, to reacted cables without generating cracks in the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn subelements and to quantify the crack propagation with increasing pressure. Metallographic techniques are used to examine the onset and evolution of damage in the transverse planes of impregnated double-stacked Rutherford-type cable specimens with increasing stress. The damage pattern observed at subelement, strand and cable levels is described. Two reaction heat treatment cycles are analyzed.

Minimum Quench Energy of Nb3Sn Wires With High Specific Heat Tape

A major problem of state-of-the-art Nb$_3$Sn accelerator magnets is their long training due to thermo-mechanical perturbations. Increasing the specific heat, $C_p$, of the Rutherford cable would reduce and/or eliminate training by limiting the coils temperature rise. This paper studies feasibility of increasing the $C_p$ of Rutherford-type cables by using thin composite Cu/$Gd_2$O$_3$ and Cu/$Gd_2$O$_2$S tapes produced by Hyper Tech Research, Inc. The tape can be either wrapped around the cable, placed on the cable wide faces under the insulation, and/or inserted as a core. Wire samples outfitted with these high-$C_p$ ribbons, or tapes, were prepared and tested at FNAL for their Minimum Quench Energy (MQE). At 90%I$_c$ and 15 T, the average gain of MQE of the Nb$_3$Sn wire soldered to the Cu/$Gd_2$O$_2$S 55 micrometer thick ribbon was 2.5, and further increased at larger transport currents.

On the effect of strand damage on the operating margin of a Nb3Sn Rutherford cable

Degradation of performance in superconducting magnets can be a major concern when a brittle material like Nb3Sn is employed. Indeed, degradation can significantly alter the transport properties of a cable if, e.g. an excessive stress is applied during coil and magnet manufacturing. In this paper, we study the limiting case of a strand in a Rutherford type cable that, at a given location, does not carry any current. We refer to such strand simplistically as the ‘broken strand’, regardless of the actual cause disrupting the current carrying capability. To this aim, a model was developed using the code THEA, to describe the electric and thermal properties of the Rutherford cable of the HL-LHC 11 T dipole magnet. First, we studied the current distribution in the cable, considering a uniform current in each strand at the boundaries, namely with single strands behaving as current generators, or zero-resistance joints, namely equipotential boundaries. We concluded that the two adjacent strands to the broken strand play the most significant role in the distribution of current out of the broken strand. A similar situation was found when a strand of the cable suddenly goes normal, i.e. it quenches. We then derived the characteristic times and lengths for the current redistribution in the case of an instantaneous strand breakage. We describe in detail the procedure to extract such quantities from the simulation results, and we demonstrate a good agreement between the numerically derived characteristic times and the analytical calculation from a previous theoretical work. The results of this study help to shed light on the repercussions of degradation in brittle materials such as Nb3Sn. This subject is indeed crucial for the next generation of accelerator coils and magnets for high-energy physics projects.

Width-bending characteristic of REBCO HTS tape and flat-tape Rutherford-type cabling

The width-bending behaviors for a rare earth barium copper oxide (REBCO) high-temperature superconducting (HTS) tape have been investigated. It has been found experimentally that the width-bending strain of a Yttrium Barium Copper Oxide (YBCO) tape does not degrade the critical current as much as is expected from the axial strain. The critical current is not directly affected by the width-bending strain but by the axial strain, which the width-bending strain generates by the Poisson effect. Since Poisson’s ratio is about 0.3, the axial strain effective on the critical current is about 30% of the width-bending strain. Therefore, the width-bending strain of even 1.5% degrades the critical current by only 15% if the REBCO layer side is bent inward. However, the critical current degraded by more than 70% when the REBCO layer is outward. The width-bending effects on the critical current have been further examined, considering Poisson’s ratio changes and the neutral plane shift of the REBCO tape substrate. Those changes would occur when the material yields due to severe width-bending. Based on the width-bending of REBCO tapes, flat-tape Rutherford-type cabling is discussed. A REBCO Rutherford-type cable can provide various advantages, especially for narrow-tape cabling. The flat-tape Rutherford-type cable has better characteristics against an electromagnetic transverse Lorentz force. Furthermore, the tape length of the cable can be approximately the same as the cable length allowing for excellent tape usage. REBCO Rutherford-type cabling will be a promising high-current, high-field cabling method using thin substrate REBCO tapes. It will be useful for AC ramp-field and pulse-field applications with low AC losses and low shield currents. It notes that the filaments in the cable are symmetrically distributed in parallel. Therefore, each filament’s inductance is uniform, and a uniform current distribution among the filaments can be obtained.

Test of Superconducting Wires and Rutherford Cables With High Specific Heat

High-field accelerator magnets made of state-of-the-art Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford cables demonstrate relatively long trainings due to sudden heat depositions originated by thermo-mechanical perturbations in the magnet coils. Coil sensitivity to these perturbations can be reduced by increasing the specific heat, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> , of major coil components - strands, or whole cable, or epoxy. The R&D on all these three approaches is in progress. This paper studies feasibility of increasing the C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> of Rutherford-type cables by using a thin composite Cu/Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> tape. The tape can be either wrapped around the cable, placed on the cable wide faces under the insulation, and/or inserted as a core. Cu/Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> ribbons with ~30% of Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> powder and two different thicknesses were produced by Hyper Tech Research, Inc. Wire and cable samples outfitted with these high-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p </sub> ribbons, or tapes, were prepared and tested at FNAL for the Minimum Quench Energy (MQE). At 80%I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , the MQE gain average over the tested magnetic field range of the NbTi cable with high-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p </sub> tape on both sides was ~1.3. The MQEgain average of the NbTi wire wrapped with the high-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p </sub> ribbon was 3.1.

Investigation on I C Degradation of MgB2 Rutherford Cables by Deformation During Cabling Process

MgB2 superconductors are promising candidates for application to devices such as Superconducting Magnetic Energy Storage, and generators. To apply MgB2 conductors to such devices, the current capacity of a conductor must be in the kilo-ampere range. Meanwhile, because the current capacity of a MgB2 conductor is typically approximately 100 A at 5 T and 4.2 K, multiple stranded cables are required. One candidate is the Rutherford-type cable. During the fabrication of Rutherford cables, strands are deformed by large bending strains at edge corners and indented at flat parts from the pressure of roller dies to maintain the cable shape. It is important to understand how critical current degrades during the fabrication of Rutherford-type cables. To optimize the strand transposition length, three types of Rutherford cables were fabricated and the critical current degradation depending on bending and indented strains was measured. Moreover, to investigate the degradation, inner structures of the strands were observed using micro-focused X-ray computed tomography and an electron probe micro analyzer.

Mechanical Behavior Laws for Multiscale Numerical Model of Nb3Sn Conductors

Low-temperature superconductors are widely used in high field magnets, mostly within Rutherford-type cables. Cables are multiscale composite structures including strands composed of superconducting filaments twisted in a metallic matrix. Mechanical effects at the filament scale affect magnetic performance, especially with strain-sensitive superconductors such as Nb3Sn. During operation, the conductor is subject to a complex combination of axial and transverse loads. It is thus necessary to build 3-D models at the cable scale. Previous work has presented a numerical approach for 3-D Finite-Elements (FE) modeling of Rutherford cables at the scale of the strand considered bi-metallic. In this paper, representative behavior laws for the different components of the strand model are identified, based on experimental results. Copper is modeled with a non-linear elastic-plastic behavior accounting for isotropic and kinematic hardenings. Homogenization of the superconducting filamentary area is carried out numerically using a FE representative volume element. Underlying parameters are identified from microstructural characterization and tensile tests on superconducting strands using an optimization routine. The strand model is compared to monotonic and cyclic tensile tests performed on Nb3Sn strand manufactured with the Powder-In-Tube method.

3-D Mechanical Finite Element Analysis of Impregnated Rutherford Cable Stacks

Low-temperature superconductors are widely used in high field accelerator magnets, mostly within Rutherford-type cables. Cables are multiscale composite structures including strands composed of superconducting filaments twisted in a metallic matrix. The magnet performance is driven by mechanical effects at the filament scale, especially with strain-sensitive superconductors such as Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn. During operation, the conductor is subject to a complex combination of axial and transverse loads. It is thus necessary to build three-dimensional (3-D) models at the cable scale. An approach to get the mechanical model of an impregnated low-temperature superconducting Rutherford-type cable is presented. The process of the 3-D geometrical reconstruction of the cable, up to the scale of the strand, is described. Techniques to model and mesh the impregnation matrix are presented. The strand model is simplified by a bi-metallic description comprising a homogeneous superconducting filamentary region between the copper core and the copper outer layer. The geometrical reconstruction of cable stacks is finally demonstrated, under several configurations. In the second part of this paper, sensitivity analyses to model parameters such as cable compaction, cable configuration, and matrix stiffness are discussed.

Effect of Applied Compressive Stress and Impregnation Material on Internal Strain and Stress State in Nb3Sn Rutherford Cable Stacks

The Nb3Sn superconductor in accelerator magnets must resist high mechanical stresses. In order to better understand the effect of the coil impregnation system on the stresses exerted on the strain-sensitive Nb3Sn superconductor, we have measured the elastic strain evolution in the conductor constituents under externally applied loads. For this purpose, a dedicated load frame that enables rotation of the sample load axis with respect to the neutron scattering geometry was installed in the Stress-Spec beamline at the neutron source Heinz Maier-Leibnitz FRM II. The Nb3Sn- and Cu-loading strains were measured in situ by neutron diffraction under monotonic and cyclic compressive loading. So-called ten-stack samples composed of Nb3Sn Rutherford type cables with different impregnation and coil blocks extracted from an 11 T dipole short model coil were investigated.

Superconducting Detector Magnets Baseline Designs for Particle Physics Experiments at the Future Circular Collider

In early 2014 a design study started at CERN for a Future Circular Collider. A new tunnel with a circumference of about 100 km for the collider magnets is foreseen as well as new general-purpose particle detectors to probe electron-positron (e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ), electron-hadron (eh), and hadron-hadron (hh) collisions, housed in large underground caverns. In the last four years baseline designs for the various detector magnets were developed. For the FCC-ee detector two magnet variants were defined: a 7.6-m bore and 7.9-m-long classical 2 T solenoid with 600 MJ stored energy, surrounding the calorimeters, and also a very challenging 4-m bore, 6-m-long, some 100-mm-thick ultrathin and radiation transparent 2 T solenoid with a stored energy of some 170 MJ, that surrounds only the inner tracker of the detectors. For the FCC-eh detector, the detector solenoid is combined with forward and backward dipole magnets required to guide the electron beam in and out of the collision point. This detector requires a 3.5 T solenoid, 2.6-m free bore and 9.2-m length with about 230 MJ of stored energy. Most demanding is the FCC-hh detector with a 14 GJ stored energy magnet system comprising three series connected solenoids, requiring 4 T in the main solenoid with 10-m free bore and a length of 20 m, in line with two 3.2 T forward solenoids with 5.1-m free bore and 4-m length. A quite challenging series of detector magnets is proposed, that needs to be further engineered in the coming years. The superconductor technology though is essentially the same in all the solenoids proposed: conductors comprising Rutherford type cables made of NbTi/Cu strands, stabilized by nickel doped pure aluminum and structurally reinforced with a high yield strength aluminum alloy. The cold masses are conduction cooled through helium cooling pipes welded to their outer support cylinder. The designs of the various baseline magnets as well as their engineering are presented.

Direct measurement of Nb3Sn filament loading strain and stress in accelerator magnet coil segments

We have directly measured, for the first time, the Nb3Sn and Cu loading strains and stresses in 11 T dipole coil segments upon compressive loading using neutron diffraction. For this purpose a load frame that enables rotation of the sample load axis with respect to the neutron scattering geometry was installed in the Stress-Spec beamline at the Heinz Maier-Leibnitz FRM II neutron source. The neutron diffraction data suggests that the magnet coil wound of Rutherford type cables can be considered as a fibre reinforced composite material. In the axial load direction the load is mainly carried by the Nb3Sn filaments and the composite stiffness can be estimated by the rule of mixtures assuming iso-strain conditions in all composite constituents. Under transverse compression the fully annealed Cu provides an isotropic pressure around the Nb3Sn filaments. The transverse load stresses in the Cu and Nb3Sn are similar, indicating iso-stress behaviour of the coil constituents under transverse compression. The broadening of the Nb3Sn diffraction peaks above critical stress values indicates reversible and irreversible Nb3Sn loading stress effects.

Phased Array Ultrasonic Nondestructive Tests of Soldered Current-Carrying Bus-Bar Splices of Superconducting Magnets

The main magnets of the Large Hadron Collider are powered by 13-kA superconducting bus-bars. The bus-bars from these magnets are electrically connected by the so-called splices, which are assembled by inductive soldering of the Rutherford-type cables and the copper profiles of the stabilizer. The quality of the soldering is of uttermost importance. Therefore, the electrical continuity of the splice in its normal conducting state has to be accurately controlled. The Phased Array Ultrasonic testing technique has been applied for the quality control of the soldered joints between the Large Hadron Collider 13-kA superconducting bus-bars. This technique consists in analyzing the internal structure of the pieces by studying the behavior of the ultrasonic propagation through the material. The results of this inspection, performed on different samples (joints), showed various types of soldering defects; which proves the potential of this type of nondestructive quality control technique. Other quality control methods, based on pulsed currents, eddy-currents and X-rays have been assessed to verify the results. The information obtained within the test has been evaluated and used for benchmarking.

A Numerical Approach for the Mechanical Analysis of Superconducting Rutherford-Type Cables Using Bimetallic Description

Low-temperature superconductors are widely used in high-field magnets, mostly within Rutherford-type cables. The run for higher fields leads to greater forces on the conductor, which is pushed closer to its mechanical limit. Managing the higher strain and stress levels on the conductor supposes to perform simulation at the strand level, especially with strain-sensitive superconductors such as Nb3Sn. Three-dimensional models are necessary because inside of a magnet, the conductor is subject to a complex combination of axial and transverse loads. Superconducting cables are anisotropic composite structures that can comprise superconducting strands, insulation materials, stabilizing parts, porosities, etc. They have a multiscale architecture, the performance at the magnet scale being driven by the filament scale. This paper proposes a numerical approach for 3-D finite-element (FE) modeling of Rutherford cables, at the scale of the strand. The 3-D mesh of two reference cables is built with a simplified cable forming model. The accuracy of this geometrical model is assessed by comparing sections of the simulated mesh with tomographic data, using relevant criteria and specific geometry analysis tools. In this approach, the strand is considered as bimetallic, with a copper core, a superconducting bundle ring, and an outer copper ring. After mechanical 3-D FE computation on this bimetallic mesh, the strain/stress state on the local compounds of the strand (including Nb3Sn filaments) is obtained by strain projection. The strain/stress state on the Nb3Sn filaments can be used to estimate the cable current transport capability, thanks to the existing scaling laws.

Design and Evaluation of Joint Resistance in SSC Rutherford-Type Cable Splices for Torus Magnet for the Jefferson Lab 12-GeV Upgrade

The Hall B 3.6-T superconducting torus magnet is being designed and built as part of the Jefferson Lab 12-GeV upgrade. The magnet consists of six trapezoidal coils connected in series, with an operating current of 3770 A. The magnet and the joints (or splices) connecting the coils are all conduction cooled by supercritical 4.6-K helium. This paper studies the design and manufacturing process of the splices made between two SSC Rutherford-type cables and discusses the tests performed to evaluate the performance of the splices under varying incident magnetic fields.

Usage of Cold Spraying of High-Heat-Capacity Coatings for the Increase of Low- &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$T_{c}$&lt;/tex-math&gt; &lt;/inline-formula&gt; Superconductors Stability

The thermal stability of NbTi Rutherford-type cables was improved with cold spray technology, namely, by depositing high-heat-capacity coatings onto the surface of the superconductors. Two short samples of identical NbTi Rutherford-type cables with different metallic/ceramic coatings were prepared and tested. The spray particles were deposited onto the cables made of eight monofilamentary NbTi/Cu wires via supersonic velocity impact. The temperature of the process is much lower than the melting point of the sprayed material. The doped sample contained 1 vol.% of large-heat-capacity substance (LHCS) Gd2O3, whereas the comparison sample did not contain any LHCS. The average heat capacity of the doped sample at 4.2 K was increased more than two times. During the tests, both samples at LHe temperature were subjected to short (∼1 ms) electromagnetic disturbances in the transverse constant magnetic field. It was found that the minimum quench energies for the sample with Gd2O3 were 1.4–1.5 times higher than that for the comparison cable without LHCS. The described method is very promising for the stabilization of dense massive windings where the direct heat transfer to the LHe is hampered and the superconductor operates in almost adiabatic conditions.

Internal Strain Measurement for a &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;$\hbox{Nb}_{3}\hbox{Sn}$&lt;/tex-math&gt;&lt;/inline-formula&gt; Rutherford Cable Using Neutron Diffraction

A Rutherford-type cable is one of candidate conductors for a large-scale or high-field superconducting magnet. It is important to evaluate the internal strain state of strand consisting of a cabling conductor to understand the strain dependence of superconducting properties. Internal lattice strains under a tensile load for Nb-rod-processed Nb 3 Sn Rutherford cable with and without the prebending treatment were measured directly by neutron diffraction at room and low temperatures. Stress-lattice strain curves of Nb 3 Sn were obtained, and it was found that the internal lattice strain is smaller than the strain measured on the cable surface by an extensometer above 100 to 150 MPa. It is important to evaluate not only the strain on the cable surface but also the internal strain of a strand in cabling conductors.

Performance of the Short Model Coils Wound With the CERN 11-T Nb&lt;sub&gt;3&lt;/sub&gt;Sn Conductor

The short model coil (SMC) dipole magnet has been designed and constructed in the framework of the European project EuCARD as a test bed for Nb 3 Sn magnet R&D in terms of coil fabrication technology and testing of Rutherford-type cables. Two pairs of racetrack coils were successfully tested in 2012, obtaining 12.5 T in the winding at 1.9 K, thus demonstrating SMC as a valid magnet design for conductor tests. These successful results prompted a new test campaign of SMC using the cable of the 11-T dipole project. The size of this cable is such that only one double pancake can be accommodated in the mechanical structure. During the latest tests using the 11-T cable, a new record field of 13.5 T was achieved, confirming the excellent capability of SMC to qualify a conductor, providing precise information of the stability and general cable performance, and to test insulation techniques, instrumentation systems, and coil fabrication processes. This paper describes the challenges of this new assembly, indicating novelties in the fabrication technology and reports on the measurements and the performance of SMC using CERN's 11-T-dipole-type conductor.

Test Results of a Nb&lt;sub&gt;3&lt;/sub&gt;Al/Nb&lt;sub&gt;3&lt;/sub&gt;Sn Subscale Magnet for Accelerator Application

The High Energy Accelerator Research Organization (KEK) has been developing a Nb3Al and Nb3Sn subscale magnet to establish the technology for a high-field accelerator magnet. The development goals are a feasibility demonstration for a Nb3Al cable and the technology acquisition of magnet fabrication with Nb3Al superconductors. KEK developed two double-pancake racetrack coils with Rutherford-type cables composed of 28 Nb3Al wires processed by rapid heating, quenching, and transformation in collaboration with the National Institute for Materials Science and the Fermi National Accelerator Laboratory. The magnet was fabricated to efficiently generate a high magnetic field in a minimum-gap common-coil configuration with two Nb3Al coils sandwiched between two Nb3Sn coils produced by the Lawrence Berkeley National Laboratory. A shell-based structure and a “bladder and key” technique have been used for adjusting coil prestress during both the magnet assembly and the cool down. In the first excitation test of the magnet at 4.5 K performed in June 2014, the highest quench current of the Nb3Sn coil, i.e., 9667 A, was reached at 40 A/s corresponding to 9.0 T in the Nb3Sn coil and 8.2 T in the Nb3Al coil. The quench characteristics of the magnet were studied.

A Structured Approach to Analyze the Influence of Channel Dimensions on Heat Extraction via Superfluid Helium

For the luminosity upgrade of the LHC at CERN, the final focusing quadrupole magnets will be exposed to an increased energy deposition in their coil windings. To have a higher heat transfer rate between cable and superfluid helium bath, the cable insulation has been subject of many studies. Improved cable insulation designs, making use of several layers of Kapton tape wound around Rutherford type cables, allow helium to penetrate via micro-channels, which are left open between adjacent Kapton tape sections. To better understand the thermal behaviour at operating temperatures below and some degrees above the helium lambda transition, besides experimental work, several numerical models have been developed to study the influence of the cable insulation. Here we present a new numerical model based on an earlier presented FEM model, which makes use of coupling variables such that the user can easily and quickly change the parameters of interest, giving the possibility to analyse new ideas effectively.