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M Breschi,
A Devred,
M Casali,
D Bessette,
M C Jewell,
N Mitchell,
I Pong, A Vostner,
P Bruzzone,
B Stepanov,
T Boutboul,
N Martovetsky,
K Kim,
Y Takahashi,
V Tronza,
Wu Yu
[show abstract]
[hide abstract]
ABSTRACT: The performance of the toroidal field (TF) magnet conductors for the ITER machine are qualified by a short full-size sample (4 m) current sharing temperature (Tcs) test in the SULTAN facility at CRPP in Villigen, Switzerland, using the operating current of 68 kA and the design peak field of 11.8 T. Several samples, including at least one from each of the six ITER Domestic Agencies participating in TF conductor fabrication (China, European Union, Japan, Russia, South Korea and the United States), have been qualified by the ITER Organization after achieving Tcs values of 6.0–6.9 K, after 700–1000 electromagnetic cycles. These Tcs values exceed the ITER specification and enabled the industrial production of these long-lead items for the ITER tokamak to begin in each Domestic Agency. Some of these samples did not pass the qualification test. In this paper, we summarize the performance of the qualified samples, analyze the effect of strand performance on conductor performance, and discuss the details of the test results.
Superconductor Science and Technology 06/2012; 25(9):095004. · 2.66 Impact Factor
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L. Reccia,
S. Turtu,
G.M. Polli,
L. Affinito,
F. Maierna,
A. della Corte,
P. Decool,
A. Torre,
H. Cloez, A. Vostner,
A. Devred,
D. Bessette,
T. Boutboul
[show abstract]
[hide abstract]
ABSTRACT: The ITER Conductor Procurement Arrangement requires that all the conductors have to be qualified before the production phase. The objects of the work here presented are the Poloidal Field Coils conductors, specifically the PF1/6 and the PF2 conductors. The realization of the samples comprised the jacketing, the compaction and the straightening of the CICC, together with the design and manufacturing of the bottom hairpin box and the upper termination. The instrumentation and the related jacket machining completed the preparation of the samples. The samples have been assembled according to the specification defined by ITER and have been shipped to SULTAN facility. This paper describes all the activities performed during the preparation, the features of the samples and all the related issues.
IEEE Transactions on Appiled Superconductivity 07/2011; · 1.04 Impact Factor
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A. Di Zenobio,
A. della Corte,
L. Muzzi,
S. Turtu,
A. Bragagni,
A. Tanguenza,
D. Valori,
A. Baldini,
D. Bessette,
A. Devred, A. Vostner
[show abstract]
[hide abstract]
ABSTRACT: In the framework of the final design activities related to the ITER Toroidal Field (TF) coils, following the very good results obtained during the TF Prototype Conductors measurement campaign, Fusion For Energy, the European Domestic Agency for ITER, has launched the conductor performance qualification phase in order to confirm the final ITER TF conductor design. Six conductor lengths have been cabled by different strand types coming from different producers: LUVATA Pori, Oxford Instruments Superconducting Technology (OST), ALSTOM (for two different strand layouts) and European Advanced Superconductors (EAS) (for two different strand layouts). ENEA has been in charge of performing QA and monitoring activity during the conductor production at LUVATA Fornaci di Barga and TRATOS Cavi, and to make visual/destructive tests over some spare lengths of the samples in order to have a detailed characterization of the produced conductors. The conductor unit lengths have been successfully manufactured and all the different work phases are here described, along with a discussion of the encountered problems and the adopted solutions. Five samples have been successfully tested in the SULTAN facility during 2009.
IEEE Transactions on Appiled Superconductivity 07/2010; · 1.04 Impact Factor
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M.C. Jewell,
T. Boutboul,
L.-R. Oberli,
Fang Liu,
Yu Wu, A. Vostner,
T. Isono,
Y. Takahashi,
Soo-Hyeon Park,
A. Shikov,
A. Vorobieva,
N. Martovetsky,
K. Seo,
D. Bessette,
A. Devred
[show abstract]
[hide abstract]
ABSTRACT: The world-wide procurement of Nb<sub>3</sub>Sn and NbTi for the ITER superconducting magnet systems will involve eight to ten strand suppliers from six Domestic Agencies (DAs) on three continents. To ensure accurate and consistent measurement of the physical and superconducting properties of the composite strand, a strand test facility benchmarking effort was initiated in August 2008. The objectives of this effort are to assess and improve the superconducting strand test and sample preparation technologies at each DA and supplier, in preparation for the more than ten thousand samples that will be tested during ITER procurement. The present benchmarking includes tests for critical current (I<sub>c</sub>), n-index, hysteresis loss (Q<sub>hys</sub>), residual resistivity ratio (RRR), strand diameter, Cu fraction, twist pitch, twist direction, and metal plating thickness (Cr or Ni). Nineteen participants from six parties (China, EU, Japan, South Korea, Russia, and the United States) have participated in the benchmarking. This round, conducted with a bronze-route Nb<sub>3</sub>Sn strand, involved samples prepared by a common laboratory (CERN) and sent out to the participants ("IO-prepared samples") and also samples prepared by each individual participant ("self-prepared samples"). I<sub>c</sub> samples prepared and measured by CERN were found to have an average I<sub>c</sub> of 188.7 A and a standard deviation of 1.8 A (1.0%), while those same set of samples measured by all the participating labs in round-robin fashion were found to have a standard deviation of 2.1 A. Self-prepared samples had an average I<sub>c</sub> of 188.1 A, and showed a lab-to-lab standard deviation of 3.5 A. The results demonstrate significant progress in the world-wide capability to accurately and reproducibly measure Nba<sub>3</sub>Sn critical current over the past decade. Future benchmarking efforts will include an annual cross-check of supplier and DA facilities, and also a round of internal t-
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in Nb<sub>3</sub>Sn samples to assess each contributor's sample-preparation techniques. A separate round of NbTi benchmarking is also envisioned.
IEEE Transactions on Appiled Superconductivity 07/2010; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In the scope of the qualification tests of the ITER TF conductors, four samples for the SULTAN facility have been prepared, each consisting of two conductor sections manufactured by the US ITER Domestic Agency. The samples are nicknamed USTF1, USTF2, USTF3 and USTF4. The conductor sections used for USTF1 and USTF3, as well as those for USTF2 and USTF4, are identical. The conductor terminations for the samples USTF1 and USTF4 are prepared by the "solder filling" method, where a copper sleeve is swaged on the dismantled conductor before the heat treatment, and the cable space is filled with a soldering alloy by siphon after the heat treatment. In USTF2 and USTF3, the conductor terminations are dismantled after the heat treatment, and the cable ends are dipped into a bath of molten solder. The main test of the conductor characterization in SULTAN is the current sharing temperature (T<sub>cs</sub>) test at 10.78 T background field. The current is raised up to 68 kA current in steps of 10 kA. Then, the coolant temperature is raised in steps of 0.25 K till quench occurs. Early voltage is observed during the current ramp before heating even at relatively low current. Due to the broad voltage-temperature (V-T) transition, the early voltage causes an uncertainty in the assessment of the conductor performance. The comparison of the test result of USTF1 vs. USTF3 and USTF2 vs. USTF4 enables to clarify the impact of the termination preparation procedure on the early voltage. In the case the early voltage is caused by non-uniform current distribution and high inter-strand resistance at the joints, the V-T behavior should be clearly different. In this paper, the joint preparation procedures are described, and the impact of the joint preparation on the conductor performance is discussed.
IEEE Transactions on Appiled Superconductivity 07/2010; · 1.04 Impact Factor
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D. Bessette,
L. Bottura,
A. Devred,
N. Mitchell,
K. Okuno,
Y. Nunoya,
C. Sborchia,
Y. Takahashi,
A. Verweij, A. Vostner,
R. Zanino,
E. Zapretilina
[show abstract]
[hide abstract]
ABSTRACT: In this paper we report the main test results obtained on the Poloidal Field Conductor Insert coil (PFI) for the International Thermonuclear Experimental Reactor (ITER), built jointly by the EU and RF ITER parties, recently installed and tested in the CS Model Coil facility, at JAEA-Naka. During the test we (a) verified the DC and AC operating margin of the NbTi Cable-in-Conduit Conductor in conditions representative of the operation of the ITER PF coils, (b) measured the intermediate conductor joint resistance, margin and loss, and (c) measured the AC loss of the conductor and its changes once subjected to a significant number of Lorentz force cycles. We compare the results obtained to expectations from strand and cable characterization, which were studied extensively earlier. We finally discuss the implications for the ITER PF system.
IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor
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[show abstract]
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ABSTRACT: The performance degradation under electro-magnetic, transverse load has grown to a key issue for the design of Nb<sub>3</sub>Sn cable-in-conduit conductors (CICC). Beside the tolerance to bending strain of the basic Nb<sub>3</sub>Sn strand and the void fraction of the CICC, a relevant parameter is thought to be the cable pattern. A sequence of ldquolongrdquo twist pitches in the early stages of a multi-stage cable is credited to mitigate the performance degradation compared to ldquoshortrdquo pitches. To assess quantitatively the effect of long/short pitches maintaining constant all other conductor parameters, a short length of four stages CICC is prepared, where the first half length has long pitches (83/140/192 mm) in the first three cable stages and the second half length has short pitches (34/95/139 mm). The last stage pitch is 213 mm for both lengths. The cable is made of Cr plated copper and Nb<sub>3</sub>Sn strands with a diameter of 0.81 mm. The conductor is assembled into a SULTAN hairpin sample where the two branches have respectively long and short pitches. The DC performance, AC loss and pressure drop are measured in both conductor sections and compared to former conductors with the same design. The results are reported and the balance of advantages and drawbacks of long vs. short pitches is discussed.
IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor
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[show abstract]
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ABSTRACT: The aim of this paper is to present an up to date review of the current status on the superconducting dipole magnet EDIPO, scheduled to be operational at CRPP-PSI (Switzerland) in mid-2010. This saddle-shaped magnet is being built in Europe by a close collaboration among EURATOM, European Associations (CRPP, ENEA) and European Industries (BNG, LUVATA). Detailed analyses (3D electromagnetic, stress-analysis, thermo-hydraulic, etc.) of the coil confirms the soundness of the design chosen for its projected performances (12.5 T in a bore of 100 mm times 150 mm over a length of ~ 1.5 m). The conductors and inter-layer joints have been qualified. The winding line has been set up at BNG and the first dummy double layers are being produced. Impregnation trials and shear tests have been made (and numerically simulated) at room as well as at operating temperature. The installation work at CRPP proceeds with the procurement of the main components (cryostat, transformer, etc.) and the detailed design of the main interface installations (support platform, cryolines etc.).
IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor
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[show abstract]
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ABSTRACT: In the ITER TF Coils reference design the circular conductor is enclosed in the grooves of a stainless steel plate, the so called radial plate. In this paper, we present an alternative solution using a relatively thin walled rectangular conductor without an additional reinforcing structure. We describe the conductor and the layout of the winding pack and analyze the magnetic, thermo-hy-draulic and mechanical behavior of the proposed coil. Then a cost analysis is carried out to estimate the significant saving that can be achieved by the proposed solution.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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ABSTRACT: Following the outcome of the conceptual design phase the EFDA dipole magnet will be made of rectangular cable-in-conduit conductors (CICC) jacketed in 316LN. In order to optimize the required amount of superconductor two different conductor types are used: a high-field (HF) conductor consisting of 144 strands and a low-field (LF) conductor with 108 strands. A high strand with a critical current density (at 4.2 K and 12 T) and an effective filament diameter of was selected. The first series of conductor prototype specimens was tested in summer 2006 but the conductor performances were lower than expected from the pre-prototype tests of 2005 and not fulfilling the design criteria. The conductor layouts were modified to increase the strand support inside the cable and the revised HF conductor design was qualified successfully end of 2006. A current sharing temperature 6 K was found at the dipole operating conditions (12.8 T, 17 kA) confirming the required temperature margin of more than 1 K. The HF conductor qualification process including the design modifications, analysis of the test results and comparison to the expectations are discussed.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Recent studies have shown that the presently considered conductor for the poloidal field coil 6 (PF6) of the ITER machine is being designed at the limit of what the considered NbTi superconductor can deliver. Furthermore tests have shown that the performance of conductor prototypes remained under the specified 1.5 K temperature margin. As a result of these issues, ITER is considering a PF6 coil design using Nb<sub>3</sub>Sn superconductor. We have investigated a PF6 coil design based on Nb<sub>3</sub>Sn superconductor, which at the same time delivers the required temperature margin as well as the higher performance capability at a similar cost as the reference NbTi design. In addition the design analysis presented here discusses performance parameters such as hot spot temperature and quench propagation. Finally we also present possible coil design and manufacturing procedures.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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A. Portone,
W. Baker,
E. Salpietro, A. Vostner,
P. Bruzzone,
F. Cau,
A. della Corte,
A. Di Zenobio,
E. Theisen,
A. Baldini,
P. Testoni,
J. Lucas,
M. Pinilla,
G. Samuelli
[show abstract]
[hide abstract]
ABSTRACT: A 12.5 T superconducting dipole magnet (European DIPOle, EDIPO) has been designed by EFDA and it is now being procured within the framework of the European Fusion Programme in order to be installed in CRPP-PSI. This saddle-shaped magnet is designed to reach 12.5 T in a 100 times 150 mm rectangular bore over a length of about 1.5 m in order to test full size conductor samples that shall be produced during the ITER magnets procurement. The magnet uses Cable In Conduit Conductor (CICC) technology and the cables are made of high Jc (about 2300 A/mm<sup>2</sup> at 4.2 K, 12 T) superconducting strands. In this paper the main magnet parameters are given together with the key supporting electromagnetic, mechanical and thermal analyses. An update on the general status of the procurement of the strand, conductors, dipole magnet and facility is also given together with the key results of the on-going supporting R&D.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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P. Bruzzone,
B. Stepanov,
R. Wesche,
E. Salpietro, A. Vostner,
K. Okuno,
T. Isono,
Y. Takahashi,
Hyoung Chan Kim,
Keeman Kim,
A.K. Shikov,
V.E. Sytnikov
[show abstract]
[hide abstract]
ABSTRACT: 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>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.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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P. Bruzzone,
M. Bagnasco,
M. Calvi,
F. Cau,
D. Ciazynski,
A. della Corte,
A. Di Zenobio,
L. Muzzi,
A. Nijhuis,
E. Salpietro,
L. Savoldi Richard,
S. Turtu, A. Vostner,
R. Wesche,
R. Zanino
[show abstract]
[hide abstract]
ABSTRACT: Four conductor lengths were prepared according to the ITER TF conductor design and assembled into two SULTAN samples. The four lengths are not fully identical, with variations of the strand supplier, void fraction and twist pitch. Lower void fractions improve the strand support and increased twist pitches also lower the strand contact pressure but both tend to increase the AC loss and the lower void fraction also increases the pressure drop so that the mass flow rate in the strand bundle area of the cable is reduced. The assembly procedure of the two samples is described including the destructive investigation on a short conductor section to assess a possible perturbation of the cable-to-jacket slippage during the termination preparation. Based on the DC performance and AC loss results from the test in SULTAN, the impact of the void fraction and twist pitch variations is discussed in view of freezing the ITER conductor design and large series manufacture. A comparison with the former generation of conductors, using similar strands but based on the ITER Model Coil layout, is also carried out. The ITER specifications, in terms of current sharing temperature, are fulfilled by both samples, with outstanding results for the conductor with longer twist pitches.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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U.B. Vetrella,
A. della Corte,
G. De Marzi,
A. Di Zenobio,
L. Muzzi,
L. Reccia,
S. Turtu,
A. Baldini,
P. Bruzzone,
E. Salpietro, A. Vostner
[show abstract]
[hide abstract]
ABSTRACT: The experience gained in the past for the ITER toroidal field model coil conductor and the results obtained so far have led to the definition of an upgraded full size prototype conductor, based on advanced Nb<sub>3</sub>Sn strand, and entirely manufactured in the European Union (EU). Samples for the characterization in the Sultan facility have been prepared by Luvata (Italy) following the conductor layout defined by ITER. ENEA was responsible for conductor fabrication. Since the conductor layout was new, a full size copper dummy conductor has been preventively produced for the setting of the cabling and jacketing tools. Then, a total of four full size superconducting cables have been prepared by using Nb<sub>3</sub>Sn advanced strands produced by Oxford Instruments (OST) and European advanced superconductors (EAS), by internal tin and bronze technology, respectively. The details of manufacturing procedures will be described in this paper.
IEEE Transactions on Appiled Superconductivity 07/2008; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In the cable-in-conduit-conductor (CICC) design of the toroidal field system for the international thermonuclear reactor (ITER) Nb<sub>3</sub>Sn is used as superconductor material. Considering the single strand performance, the crucial characteristic is the strain dependence of the critical current. Within this context, the performance of the CICC under strain is determined by the behaviour of the single strands and additional effects related to the manufacturing process. In the framework of the European fusion technology program a task has been started to investigate single strands as well as sub-size CICC performance using different cable layouts (9, 45 and 180 strands). For this systematic approach, parameters such as the void fraction, the number of pure copper strands, the void fraction or the cabling pattern have been varied. To examine the critical properties in detail, the available test facility, consisting of two experimental setups, is capable to measure the strain dependence in magnetic fields up to 14 T at 4.2 K, by applying an axial load to the samples. Measurements on such sub-size CICC samples are presented and compared to the expected performance.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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P. Bruzzone,
M. Bagnasco,
D. Ciazynski,
A. della Corte,
A. Di Zenobio,
R. Herzog,
Y. Ilyin,
B. Lacroix,
L. Muzzi,
A. Nijhuis,
B. Renard,
E. Salpietro,
L.S. Richard,
B. Stepanov,
S. Turtu, A. Vostner,
R. Wesche,
L. Zani,
R. Zanino
[show abstract]
[hide abstract]
ABSTRACT: Two short length samples have been prepared and tested in SULTAN to benchmark the performance of high current density, advanced Nb<sub>3</sub>Sn strands in the large cable-in-conduit conductors (CICC) for ITER. The cable pattern and jacket layout were identical to the toroidal field model coil conductor (TFMC), tested in 1999. The four conductor sections used strands from OST, EAS, OKSC and OCSI respectively. The Cu:non-Cu ratio was 1 for three of the new strands, compared to 1.5 in the TFMC strand. The conductors with OST and OKSC strands had one Cu wire for two Nb<sub>3</sub>Sn strands, as in TFMC. In the EAS and OCSI conductors, all the 1080 strands in the cable were Nb<sub>3</sub>Sn. A dc test under relevant load conditions and a thermal-hydraulic campaign was carried out in SULTAN. The CICC performance was strongly degraded compared to the strand for all the four conductors. The current sharing temperature at the ITER TF operating conditions (j<sub>op</sub> = 286 A/mm<sup>2</sup>, B = 11.15 T) was lower than requested by ITER.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The effect of transverse loads on strands has been pointed as a possible cause of the difference observed when scaling transport properties of single strands to those of cable-in-conduit conductors. Single multifilamentary strands inside cables are in fact subject to bending strain due to the electromagnetic forces at operating conditions and to the geometrical layout. Here the influence of pure bending strain, applied in combination with a longitudinal strain, on the critical current of advanced strands for ITER has been studied. The tested samples are single strands inserted inside a thin stainless steel jacket and wound on stainless steel barrels. After the heat treatment, a pure bending strain has been applied transferring the wires on different diameter mandrels, using ad-hoc developed and qualified techniques. Transport critical current has been measured on the single strands before and after the steel jacketing, as well as after the additional application of two different values of maximum bending strain: 0.5% and 0.25%. This was the best choice in order to verify experimentally whether the so-called long twist pitch condition can be applied for the selected strands. The distribution of the bending strain over the strand cross-section has been calculated with finite element numerical codes, and the expected critical current degradation in the limiting cases of short and long twist pitch has been computed and compared with experimental data.
IEEE Transactions on Appiled Superconductivity 07/2007; · 1.04 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The tests analysis of the International Thermonuclear Experimental Reactor (ITER) model coils showed lower performances than expected. For that reason, a specific program has been launched in Europe for investigating the influence of bending strain on the transport properties of high-performances Nb3Sn strands inside cable-in-conduit conductors when experiencing significant Lorentz forces. To this purpose, an experimental campaign has been initiated on single Nb3Sn strands jacketed inside a 0.2 mm thick stainless-steel (SS) tube in order to be tested in mechanical ITER Toroidal Field (TF) Coils relevant conditions. In this article we describe in a first part the procedure investigated at CEA to impose a controlled pure bending strain upon jacketed stands and we present the results of the qualification tests carried out in the ENEA facility to assess the reliability of the chosen method. In a second part we propose a new model to simulate the strands behaviour experiencing bending strain together with an initial compressive strain. To understand our results, a key parameter considered is a specific weighting function relying on strand interfilament current redistribution capacity. At the end, this model enables us to explain more reliably the experimental results but also shows discrepancies which requires further improvements and extra refinements
Journal of Physics Conference Series 07/2006; 43(1):759.
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[show abstract]
[hide abstract]
ABSTRACT: For the superconducting magnet system of the International Thermonuclear Experimental Reactor, ITER, 60 current leads for a total current of more than 2500 kA are needed. To reduce the resultant large refrigerator load at 4.5 K, High Temperature Superconductor current leads (HTS-CL) could be used. Therefore, EFDA CSU Garching had launched a development program for a 70 kA HTS-CL demonstrator. The Forschungszentrum Karlsruhe and CRPP developed and built this CL optimized for 50 K Helium operation. In 2004, the CL was successfully tested in the TOSKA facility at the Forschungszentrum Karlsruhe. The very encouraging results lead to testing this CL with 80 K Helium because ITER provides a large 80 K Helium cooling capacity for the thermal shields. At the end of last year, the test could be successfully performed demonstrating that high current capacity current leads can be stably operated at about 80-85 K. Recently, the CL was retested using liquid nitrogen which would be an interesting alternative option. In this paper, the test results for the 80 K He cooling operation as well as for the operation with LN<sub>2</sub> are presented and compared to the results obtained before for nominal conditions
IEEE Transactions on Appiled Superconductivity 07/2006; · 1.04 Impact Factor
