| 41. |
- Nilsson, P A, et al.
(författare)
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Planarized patterning of Y-Ba-Cu-O thin films for multilayer technology
- 1995
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 5, s. 1653-1656
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Tidskriftsartikel (refereegranskat)abstract
- Planarized layers of YBa2Cu3O7 (YBCO) were made by etching trenches in SrTiO3 (STO) substrates, laser depositing a YBCO film and mechanically polishing the film down to the substrate surface. These structures exhibited critical temperatures (Tc) of 88 K and a critical-current density (Jc) of 106 A/cm2 at 77 K. The planarized surface was smooth, with a maximum height difference between the YBCO and STO of 20 nm. The surfaces were used as templates for epitaxial growth of multilayer insulators of STO and PrBa2Cu3O7 (PBCO) and top YBCO layers. Complete crossovers, free of superconducting shorts, with Tc of 86 K and critical current density (Jc) of 2×105 A/cm2 were made.
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| 42. |
- Novoselov, Evgenii, 1988, et al.
(författare)
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Broadband MgB2 Hot-Electron Bolometer THz Mixers operating up to 20K
- 2017
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- We discuss performance of submicron size hot-electron bolometer (HEB) mixers made from thin MgB2 superconducting films. With a superconducting transition temperature of 30K, such THz mixers can operate with high sensitivity at temperatures up to 20K. Due to very small dimensions local oscillator (LO) power requirements are rather low. In the intermediate frequency (IF) band of 1-3GHz the double sideband receiver noise temperature is 1600K at 10K operation temperature, 2000K at 15K, 2500-3000K at 20K. The gain bandwidth of such devices is 6GHz and the noise bandwidth is estimated to be 6-8GHz
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| 43. |
- Novoselov, Evgenii, 1988, et al.
(författare)
-
Study of MgB2 ultra-thin films in submicron size bridges
- 2017
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 27:4
-
Tidskriftsartikel (refereegranskat)abstract
- We discuss a custom built hybrid physical chemical vapour deposition (HPCVD) system for MgB2 ultra-thin film deposition: construction, deposition process development, and optimization. Achieved films on SiC substrates have a critical temperature (Tc) ranging from 35K (10nm thick films) to 41K (40nm thick films). The 20nm thick unpatterned film had a room temperature resistivity of 13μΩ·cm, whereas it becomes 50μΩ·cm in sub-micrometer size bridges with a critical current density Jc (4.2K) up to 1.2×10^8A/cm2. The lower value of resistivity corresponds to the higher of both Tc and Jc. The surface roughness, measured with an atomic force microscope (AFM), is approximately 1.5nm.
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| 44. |
- Paturi, P., et al.
(författare)
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Dopant Diameter Dependence of J(c)(B) in Doped YBCO Films
- 2016
-
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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| 45. |
- Pepitone, K., et al.
(författare)
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Design and Fabrication of a Canted-Cosine-Theta Double Aperture Orbit Corrector Dipole for the LHC
- 2023
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515 .- 2378-7074. ; 33:5
-
Tidskriftsartikel (refereegranskat)abstract
- A prototype CCT dipole magnet developed by a collaboration between Swedish universities, Swedish industry and CERN will be tested at Uppsala University. This 1 m long double-aperture magnet can provide a field strength of 3.3 T at 85 A in a 70 mm aperture with an integrated field of 2.8 Tm. It is intended to replace the current LHC orbit corrector magnets which are reaching the end of their expected life due to the radiation load. The new magnet is designed to handle the radiation dose of the upgrade to the high-luminosity LHC, which will deliver about ten times the current radiation dose. It must therefore be more resistant to radiation and meet strict requirements in terms of electrical insulation while matching the original field quality and self-protective capability, mechanical volume, and maximum excitation current. This paper will present the latest of the design and manufacturing work, including the results of simulations of the mechanical field and the mechanical stress. Details of the various tests performed before machining the parts are also presented.
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| 46. |
- Pepitone, Kevin, Dr, 1988-, et al.
(författare)
-
Design and Fabrication of a Canted-Cosine-Theta Double Aperture Orbit Corrector Dipole for the LHC
- 2023
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 33:5
-
Tidskriftsartikel (refereegranskat)abstract
- A prototype CCT dipole magnet developed by a collaboration between Swedish universities, Swedish industry and CERN will be tested at Uppsala University. This 1 m long double-aperture magnet can provide a field strength of 3.3 T at 85 A in a 70 mm aperture with an integrated field of 2.8 Tm. It is intended to replace the current LHC orbit corrector magnets which are reaching the end of their expected life due to the radiation load. The new magnet is designed to handle the radiation dose of the upgrade to the high-luminosity LHC, which will deliver about ten times the current radiation dose. It must therefore be more resistant to radiation and meet strict requirements in terms of electrical insulation while matching the original field quality and self-protective capability, mechanical volume, and maximum excitation current. This paper will present the latest of the design and manufacturing work, including the results of simulations of the mechanical field and the mechanical stress. Details of the various tests performed before machining the parts are also presented.
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| 47. |
- Pepitone, Kevin, Dr, 1988-, et al.
(författare)
-
Design of a Canted-Cosine-Theta Orbit Corrector for the High Luminosity LHC
- 2022
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 32:6
-
Tidskriftsartikel (refereegranskat)abstract
- The High Luminosity LHC requires dipole orbit correctors grouped in double aperture magnet assemblies. They provide a field of 3.1 T at 100 A in an aperture of 70 mm. The current standard design is a classical cosine-theta layout made with ribbon cable. However, the electric insulation of this cable is not radiation-resistant enough to withstand the radiation load expected in the coming years of LHC operation. A new design, based on a cable with polyimide insulator, that can replace the existing orbit correctors, is needed. The challenge is to design a magnet that fits directly into the existing positions and that can operate with the same busbars, passive quench protection, and power supplies. The new orbit corrector design meets high requirements on the field quality while keeping within the same mechanical volume and maximum excitation current. A collaboration of Swedish universities and Swedish industry has been formed for the development and production of a prototype magnet following a concurrent engineering methodology to reduce the time needed to produce a CCT magnet. The magnet has a 1 m long CCT dipole layout consisting of two coils. The superconductor is a commercially available 0.33 mm wire with polyimide insulation in a 6-around-1 cable. The channels in the coil formers, that determine the CCT layout, allow for 2 x 5 cable layers. A total of 70 windings makes that the coil current can be kept below 100 A. We will present the detailed design and preliminary quench simulations.
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| 48. |
- Politano, D., et al.
(författare)
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Technical and Economical Assessment of HTS Cables
- 2001
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223. ; 11:1, s. 2477-2480
-
Tidskriftsartikel (refereegranskat)
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| 49. |
- Prikhna, Tatjana A., et al.
(författare)
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High-pressure synthesized nanostructural MgB2 materials with high performance of superconductivity, suitable for fault current limitation and other applications
- 2011
-
Ingår i: IEEE transactions on applied superconductivity (Print). - 1051-8223 .- 1558-2515. ; 21:3, s. 2694-2697
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Tidskriftsartikel (refereegranskat)abstract
- A variety of samples made via different routes were investigated. Samples are nanostructured (average grain sizes are about 20 nm). The advantage of high-pressure (HP)-manufactured (2 GPa, 800-1050 degrees C, 1 h) MgB2 bulk is the possibility to get almost theoretically dense (1-2% porosity) material with very high critical current densities reaching at 20 K, in 0-1 T j(c) = 1.2 - 1.0 . 10(6) A/cm(2) (with 10% SiC doping) and j(c) = 9.2 - 7.3 10(5) A/cm(2) (without doping). Mechanical properties are also very high: fracture toughness up to 4.4 +/- 0.04 MPa . m(0.5) and 7.6 +/- 2.0 MPa . m(0.5) at 148.8 N load for MgB2 undoped and doped with 10% Ta, respectively. The HP-synthesized material at moderate temperature (2 GPa, 600 degrees C, 1 h) from B with high amount of impurity C (3.15%) and H (0.87%) has j(c) = 10(3) A/cm(2) in 8 T field at 20 K, highest irreversibility fields (at 18.4 K H-irr = 15 T) and upper critical fields (at 22 K H-C2 = 15 T) but 17% porosity. HP materials with stoichiometry near MgB12 can have T-c = 37 K and j(c) = 6 . 10(4) A/cm(2) at 0 T and H-irr = 5 T at 20 K. The spark plasma synthesized (SPS) material (50 MPa, 600-1050 degrees C 1.3 h, without additions), demonstrated at 20 K, in 0-1 T j(c) = 4.5 - 4 10(5) A/cm(2). Dispersed inclusions of higher magnesium borides, which are usually present in MgB2 structure and obviously create new pinning centers can be revealed by Raman spectroscopy (for the first time a spectrum of MgB7 was obtained). Tests of quench behavior, losses on MgB2 rings and material thermal conductivity show promising properties for fault current limiters. Due to high critical fields, the material can be used for magnets.
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| 50. |
- Rossi, L., et al.
(författare)
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A European Collaboration to Investigate Superconducting Magnets for Next Generation Heavy Ion Therapy
- 2022
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 32:4
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Tidskriftsartikel (refereegranskat)abstract
- Next generation ion therapy magnets both for gantry and for accelerator (synchrotron) are under investigation in a recently launched European collaboration that, in the frame of the European H2020 HITRIplus and I.FAST programmes, has obtained some funding for work packages on superconducting magnets. Design and technology of superconducting magnets will be developed for ion therapy synchrotron and -especially- gantry, taking as reference beams of 430 MeV/nucleon ions (C-ions) with 10(10) ions/pulse. The magnets are about 60-90 mm diameter, 4 to 5 T peak field with a field change of about 0.3 T/s and good field quality. The paper will illustrate the organization of the collaboration and the technical program. Various superconductor options (LTS, MgB2 or HTS) and different magnet shapes, like classical CosTheta or innovative Canted CosTheta (CCT), with curved multifunction (dipole and quadrupole), are under evaluation, CCT being the baseline. These studies should provide design inputs for a new superconducting gantry design for existing facilities and, on a longer time scale, for a brand-new hadron therapy centre to be placed in the South East Europe (SEEIIST project).
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