| 1. |
- Arpaia, Riccardo, 1985, et al.
(author)
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Improved Nanopatterning for YBCO Nanowires Approaching the Depairing Current
- 2013
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In: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 23:3
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Journal article (peer-reviewed)abstract
- An improved nanopatterning procedure has been developed to obtain YBa2Cu3O7-x nanowires with cross-sections as small as 50 x 50 nm(2), protected by an Au capping layer. To probe the effective role of the Au protecting layer, we have measured the current-voltage characteristics and the resistive transition in temperature of the nanowires. Critical current densities up to 108 A/cm(2) have been achieved at T = 4.2 K, approaching the theoretical depairing current limit. The resistance, measured as a function of temperature close to T-c, has been fitted with a thermal activated phase slip model, including the effect of the gold layer. The extracted values of the superconducting coherence length and of the London penetration depth give current densities consistent with the measured ones. These results cannot be achieved with nanowires without the Au capping layer.
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| 2. |
- Arzeo, Marco, 1986, et al.
(author)
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Microwave losses in YBCO coplanar waveguide resonators at low power and millikelvin range
- 2015
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In: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3
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Journal article (peer-reviewed)abstract
- We have investigated the temperature dependence of microwave losses in the low-power limit and millikelvin temperature range of a thin-film YBa2Cu3O7-x (YBCO) λ/2 coplanar waveguide resonator patterned on a (La0.3Sr0.7) (Al0.65Ta0.35)O3 (LSAT) substrate covered by a CeO2 seed layer. The unloaded quality factor is mainly governed by the surface resistance of the YBCO film and the dielectric losses caused by resonant absorption due to a bath of two-level fluctuators in the dielectrics. The value of the unloaded quality factor at 20 mK and low power, i.e., Q0∼2000, allows for the realization of YBCO microwave quantum circuits implementing biepitaxial grain-boundary Josephson junctions.
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| 3. |
- Baghdadi, Reza, 1984, et al.
(author)
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Toward YBa2Cu3O7-δ nanoscale structures for hybrid devices
- 2015
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In: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3
-
Journal article (peer-reviewed)abstract
- An ex situ ozone annealing has been applied both on YBa2Cu3O7-d (YBCO) films and nanowires. From the investigation on bare films, by measuring the superconducting resistive transition in temperature and the X-ray diffraction pattern, we have observed that the ozonation can be a powerful tool to oxygenate the YBCO structure. To probe the effective role of this reactive annealing on nanostructures, we have fabricated nanowires with widths down to 100 nm, covered by a 20-nm-thick Au layer. We have compared the critical current density and the broadening of the resistance transition measured before and after the ozone treatment, concluding that the ozone is instrumental in recovering very high quality superconducting properties inside the nanostructures, which were degraded by the oxygen out-diffusion occurring during the nanopatterning.
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| 4. |
- Bagni, Tommaso, et al.
(author)
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Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
-
In: 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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Journal article (peer-reviewed)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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| 5. |
- Bagni, T., et al.
(author)
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Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
-
In: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 34:5
-
Journal article (peer-reviewed)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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| 6. |
- Barna, D., et al.
(author)
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Test Results of the First Wax-Impregnated Nb-Ti Canted Cosine Theta Septum Magnet “SuShi”
- 2024
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In: 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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Journal article (peer-reviewed)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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| 7. |
- Bevilacqua, Stella, 1981, et al.
(author)
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MgB2 Hot-Electron Bolometer Mixers at Terahertz Frequencies
- 2015
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In: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3, s. 2301104-
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Journal article (peer-reviewed)abstract
- In this paper, we compare the performance of MgB2 Hot-Electron Bolometer Mixers operating at Local Oscillator frequencies of 0.6 and 1.63 THz. The minimum noise temperatures that were obtained are 700 and 1150 K for 0.6 and 1.63 THz, respectively. The receiver noise bandwidth is of the order of 2.2-3 GHz for 10-nm-thick HEB devices with a Tc of 8.5 K. Sub-micrometer size HEBs were also fabricated with no degradation of the initial film quality when a 20-nm MgB2 film with a Tc of 22 K was used. In the direct detection mode, the maximum voltage responsivity is in the range of 1-2 kV/W at 1.63 THz and the optimal bias current is around 1/4-1/3 of the Ic at 4.2 K.
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| 8. |
- Bevilacqua, Stella, 1981, et al.
(author)
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Wideband MgB2 Hot-Electron Bolometer Mixers: IF Impedance Characterisation and Modeling
- 2016
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In: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 26:3, s. 2300105-
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Journal article (peer-reviewed)abstract
- In this paper we present a method for low signal S11 parameter vector measurements of a cryogenic device in the microwave frequency range. In particular, the intermediate frequency (IF) impedance of MgB2 Hot-electron Bolometer (HEB) mixers was investigated over a frequency range of 100 MHz to 10 GHz. A new cryogenic calibration technique, which employs the HEB as a calibration kitandrequires two consecutive thermal cycles, was developed for this purpose.The real part of measured IF impedance showed a strong correlationwith the differential resistance (dV/dI) obtained from the dc I-V curves while the imaginary partwas capacitive for almost the entire frequency range.
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| 9. |
- Born, D., et al.
(author)
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CaBaCuO ultrathin films and junctions
- 2007
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In: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 17:2/3, s. 3581-3584
-
Journal article (peer-reviewed)abstract
- We investigated transport properties of ultrathin CaBaCuO (CBCO) bridges, focusing on vortex dynamics, and Josephson bicrystal junctions. The CBCO films used are composed of a stacking sequence of two structural subunits having different functions, namely a Ba-based charge reservoir (CR) block and a Ca-based infinite layer (IL) superconducting block. SQUID microscopy investigations of these films provide Pearl lengths A more than the bridge widths. Measuring current-voltage characteristics we found evidence that at high temperatures the vortices are thermally activated at the edge of the bridge and pushed in, causing dissipation and a power-law dependence of the voltage from the current. At lower temperatures, the experimental curves change their shape. We compared these data with the predicted behavior for vortex quantum tunneling and we found very good agreement. Moreover, we have realized Josephson junctions composed of only a few superconducting CuO2 planes. The CBCO films used in these experiments are only 8 nm thick and have six superconducting CUO2 planes. The simple structure of the GB allows a reliable estimation of the coupling along the ab planes of the CuO2. We calculate for 24 degrees symmetric and asymmetric cases a critical current density per plane of about (1-3) kA/cm(2).
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| 10. |
- Branny, Artur, et al.
(author)
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X-Ray Induced Secondary Particle Counting With Thin NbTiN Nanowire Superconducting Detector
- 2021
-
In: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 31:4
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Journal article (peer-reviewed)abstract
- We characterized the performance of abiased superconducting nanowire to detect X-ray photons. The device, made of a 10 nm thin NbTiN film and fabricated on a dielectric substrate (SiO2, Nb3O5) detected 1000 times larger signal than anticipated from direct X-ray absorption. We attributed this effect to X-ray induced generation of secondary particles in the substrate. The enhancement corresponds to an increase in the flux by the factor of 3.6, relative to a state-of-the-art commercial X-ray silicon drift detector. The detector exhibited 8.25 ns temporal recovery time and 82 ps timing resolution, measured using optical photons. Our results emphasize the importance of the substrate in superconducting X-ray single photon detectors.
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