| 1. |
- Bagni, Tommaso, et al.
(författare)
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Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 34:5, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- A newly designed superconducting magnet of the Canted-Cosine-Theta (CCT) type was developed as a result of a collaboration between Swedish universities (Uppsala and Linneaus) and Swedish industries. This magnet was designed to function as a replacement of the present LHC orbit corrector magnets, which are approaching their end of life due to the radiation load. As a result, the new CCT magnet was developed to be more radiation tolerant and to constitute a one-to-one replacement to the currently installed version, which is a 1 m long 70 mm double aperture dipole magnet. The final magnet, which is currently under construction, will be tested at FREIA laboratory at Uppsala University and generate a magnetic field of 3.3 T and an integrated field of 2.8 Tm at about 85 A. To examine the magnet quench behavior and to identify a suitable quench protection system, the 3D electro-magnetic and thermal behavior of the coil was modeled using the RAT-Raccoon software. Based on the simulation results, a Metrosil varistor was selected to protect the magnet during the test. In this article, we report the results of the numerical analysis. The magnet model is equipped with a spot heater to initialize the quench and the temperature and voltages are monitored during the avalanche effect. The simulated current decay and the hot-spot temperature are analyzed with a focus on the impact of quench-back on the magnet protection.
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| 2. |
- Barna, D., et al.
(författare)
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Test Results of the First Wax-Impregnated Nb-Ti Canted Cosine Theta Septum Magnet “SuShi”
- 2024
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 34:5, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- In the framework of the future circular collider study, a new septum magnet concept (“SuShi”) has been developed, and a prototype was built at Wigner RCP, and tested at the FREIA facility of Uppsala University. The concept uses a canted cosine theta (CCT)-like superconducting magnet and a passive superconducting shield to create a zero-field and high-field region within its aperture. SuShi is the first CCT magnet with both of its winding layers simultaneously impregnated with wax. Details of the construction will be presented, with special emphasis on the wax impregnation procedure which deals with the ∼ 15% contraction of wax upon solidification. The empty magnet (no shield in its aperture) was powered without training to 450 A with a peak field of 3.64 T, corresponding to 80% of the short sample limit of the conductor along the load line. No quench or other anomaly was observed during the entire testing period. A clear onset of quench-back was observed above about 200 A.
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| 3. |
- Galvin, Tom, et al.
(författare)
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Characterisation of SiC Varistor Quench Protection Operating at 4 Kelvin for Use With Superconducting Magnets
- 2023
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 33:5
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) composite high-energy varistors have been demonstrated as a viable alternative to linear resistors as energy extraction devices during an abrupt loss of superconductivity in a magnet, called a quench. These have typically been installed external to the cryostat at ambient temperatures, but for some superconducting magnets it may be beneficial to mount the varistors within the cryostat in vacuum, a gaseous environment, or submerged in liquid cryogens. Varistors are semiconductors and therefore exhibit a temperature-dependent voltage-current relationship, so characterising their behaviour at low temperatures is important to predict their energy extraction behaviour. In this paper we present characterisation data of SiC varistor devices from 4-300 K: voltage-current characteristics, thermal conductivity, specific heat capacity, thermal expansion, and flexural strength. These varistors are a candidate for protection at 1.9 K of the MCBY magnets, currently being built at Uppsala University for CERN.
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| 4. |
- Huang, J., et al.
(författare)
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Pulsed Field Stability and AC Loss of ITER PF Joints by Detailed Quantitative Modeling
- 2023
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 33:8
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Tidskriftsartikel (refereegranskat)abstract
- For fusion tokamaks, such as International Thermonuclear Experimental Reactor (ITER), the magnet systems are based on superconducting cable-in-conduit conductors (CICCs). Due to the limited production length of the CICCs and the necessary electrical and thermal connections, joints are widely used to connect the CICC units within the magnet coils, as well as the electrical and thermal interfaces outside the magnet. The joints dominate the current redistribution in the coils and, thus, are critical for the magnet stability. In this study, an ITER poloidal field coil joint operating in pulsed mode is chosen to study the current nonuniformity and relevant stability issues. An optimized joint design by applying high resistive polyimide layers, called "masks" to actively block the large induced coupling currents, is tested with the numerical code JackPot-AC/DC. The current nonuniformity, power dissipation, and thermal evolution of the joints with different configurations are quantitatively analyzed.
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| 5. |
- Huang, M, et al.
(författare)
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Small scale integrated technology for HTS RSFQ circuits
- 2001
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Ingår i: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223. ; 11:1, s. 558-561
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Tidskriftsartikel (refereegranskat)abstract
- A technology for fabrication of YBCO ramp junctions on a superconducting ground plane Is developed and evaluated. The technology is based on a two-layer, S-I, structure or on a four-layer, S-I-S-I, structure grown in situ with YBCO superconductor and with
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| 6. |
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| 7. |
- Mangiarotti, Franco J., et al.
(författare)
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Test of Short Model and Prototype of the HL-LHC D2 Orbit Corrector Based on CCT Technology
- 2019
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223 .- 1558-2515. ; 29:5
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Tidskriftsartikel (refereegranskat)abstract
- In the frame of the high-luminosity upgrade project for the large hadron collider, new twin aperture beam orbit corrector magnets will be installed near the recombination dipole (D2). These magnets are 2.2 m long canted cosine theta NbTi dipoles, with two independently powered apertures oriented such that their field vectors are perpendicular to each other and to the direction of the beams. A 0.5 m model magnet in single and double aperture configuration and a full-length double aperture prototype were built and tested at CERN. In this paper, the performance of these magnets at 1.9 K in terms of training behavior, quench detection and protection, and other tests is discussed. In addition, the thermal response of the magnet to a hypothetical beam discharge is simulated and analyzed.
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| 8. |
- Mangiarotti, Franco J., et al.
(författare)
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Test of the First Full-Length Prototype of the HL-LHC D2 Orbit Corrector Based on Canted Cosine Theta Technology
- 2020
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223 .- 1558-2515. ; 30:4
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Tidskriftsartikel (refereegranskat)abstract
- In the context of CERN's high-luminosity upgrade project (HL-LHC) for the Large Hadron Collider (LHC), a new double aperture beam orbit corrector magnets will be installed near the recombination dipole (D2). These 2.2 m long NbTi dipoles are built with the canted cosine theta (CCT) technique. The two independently powered apertures are oriented such that their field vectors are perpendicular to each other and to the direction of the beams. A full-length double aperture prototype was built and tested at CERN in the SM18 test facility. Here we present the results of powering tests at 1.9 and 4.5 K: training of each aperture, magnetic field quality and cross-talk effects, quench detection system effectiveness, quench protection performance and quench-back with several energy extraction systems.
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| 9. |
- Mangiarotti, Franco, et al.
(författare)
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Test Results of the CERN HL-LHC Low-beta Quadrupole Short Models MQXFS3c and MQXFS4
- 2019
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223 .- 1558-2515. ; 29:5
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Tidskriftsartikel (refereegranskat)abstract
- For the high luminosity upgrade of the CERN large hadron collider, lower beta* quadrupole magnets based on advanced Nb3Sn conductors will be installed on each side of the ATLAS and compact muon solenoid (CMS) experiment insertion zones. As part of the technological developments needed to achieve the required field gradient of 132.6 T/m within a 150-mm aperture, short length model magnets, named MQXFS, are tested both at the CERN SM18 and Fermilab test facilities. The model magnets rely on two types of Nb3Sn conductors (restack rod process (RRP) and powderin-tube (PIT)) and on an innovative bladders and keys design to provide mechanical support against the Lorentz forces. In 2016 and 2017, the powering tests of the first two models MQXFS3 (RRP) and MQXFS5 (PIT) proved that nominal performance (16.5 kA) could be reached with excellent memory of the quench current after thermal cycle. However both magnets showed a slow training behavior with clear observations of voltage disturbances before the quench. Besides, only MQXFS5 could reach ultimate current (17.9 kA) whereas erratic behavior was observed on MQXFS3 due to conductor local degradation at the head of one of the coils. In 2018, this limiting coil was changed and the applied azimuthal prestress increased. While ultimate current could then be reached, no stable current could be maintained due to identified defect on the outer layer of the new coil. Finally the outcome of the test of the new model MQXFS4, featuring the final RRP conductors that will be used for the series production and variation on the inner layer quench heater designs are here reported in details.
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| 10. |
- Paturi, P., et al.
(författare)
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Dopant Diameter Dependence of J(c)(B) in Doped YBCO Films
- 2016
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Ingår i: IEEE transactions on applied superconductivity (Print). - 1051-8223 .- 1558-2515. ; 26:3
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Tidskriftsartikel (refereegranskat)abstract
- In YBCO films doped with artificial pinning centers, such as BaZrO3 nanorods or BaCeO3 nanodots, the critical current density, J(c)(B vertical bar vertical bar c), is usually described with the form J(c) similar to B-alpha even though the shape of the J(c)(B)-curve does not really allow this. In the field region just above the low field plateau, the shape of the J(c)(B)-curve (in log-log scale) is rounded and not straight as in undoped films. The exponent alpha is found to decrease from 0.5 to around 0.2 in BaZrO3 doped films and to 0.4 in BaCeO3 doped films. The incompatibility with the curved data and the linear fit has lead to publication of alpha-parameters which are not comparable to each other due to different fitting limits. In this paper we show that it is better to use the Dew-Hughes pinning force F-p(B) = F-p0(B / Birr)(p)(1 - B / B-irr)(q) to describe the field dependence, where alpha approximate to 1 - p. We also show that the p and the roundness of the curve depend on the diameter of the pinning centers, but not, e.g., temperature or dopant concentration. This is shown from measurements of differently doped thin YBCO films and from large scale Ginzburg-Landau simulations. The result should have been expected since the diameters of the dopants are roughly the same size as the coherence length and it has been shown earlier that pinning centers much smaller than the coherence length lead to alpha = 0.5 and those much larger lead to alpha = 1.
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