| 1. |
- Arpaia, Riccardo, 1985, et al.
(författare)
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Improved Nanopatterning for YBCO Nanowires Approaching the Depairing Current
- 2013
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 23:3
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Microwave losses in YBCO coplanar waveguide resonators at low power and millikelvin range
- 2015
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3
-
Tidskriftsartikel (refereegranskat)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.
(författare)
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Toward YBa2Cu3O7-δ nanoscale structures for hybrid devices
- 2015
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3
-
Tidskriftsartikel (refereegranskat)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.
(författare)
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Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 34:5, s. 1-5
-
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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| 5. |
- Bagni, T., 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
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 34:5
-
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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| 6. |
- 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
-
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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| 7. |
- Batson, Emma K., et al.
(författare)
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Effects of Helium Ion Exposure on the Single-Photon Sensitivity of MgB $_{2}$ and NbN Detectors
- 2024
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Improving the scalability, reproducibility, and operating temperature of superconducting nanowire single photon detectors (SNSPDs) has been a major research goal since the devices were first proposed. The recent innovation of helium-ion irradiation as a post-processing technique for SNSPDs could enable high detection efficiencies to be more easily reproducible, but is still poorly understood. Additionally, fabricating detectors at micron-wide scales from high-T$_{\mathrm{C}}$ materials could improve scalability and operating temperature, respectively. At the same time, fabrication of successful devices in wide wires and from higher-T$_{\mathrm{C}}$ materials like magnesium diboride has proven challenging. In this work, we compare helium ion irradiation in niobium nitride and magnesium diboride detectors with different material stacks in order to better understand the mechanics of irradiation and practical implications of encapsulating layers on effective dose. We examine the effects of experimental effective dose tests and compare these results to the damage per ion predicted by simulations in corresponding material stacks. In both materials, irradiation results in an increase in count rate, though for niobium nitride this increase has not fully saturated even at the highest tested dose of $2.6\times 10^{17}$ ions/cm$^{2}$, while for resist-encapsulated magnesium diboride even the lowest tested dose of $1\times 10^{15}$ ions/cm$^{2}$ appears higher than optimal. Our results demonstrate the general applicability of helium ion irradiation to vastly different devices and material stacks, albeit with differing optimal doses, and show the reproducibility and effectiveness of this post-processing technique in significantly improving SNSPD efficiency.
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| 8. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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MgB2 Hot-Electron Bolometer Mixers at Terahertz Frequencies
- 2015
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3, s. 2301104-
-
Tidskriftsartikel (refereegranskat)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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| 9. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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Wideband MgB2 Hot-Electron Bolometer Mixers: IF Impedance Characterisation and Modeling
- 2016
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 26:3, s. 2300105-
-
Tidskriftsartikel (refereegranskat)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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| 10. |
- Born, D., et al.
(författare)
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CaBaCuO ultrathin films and junctions
- 2007
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 17:2/3, s. 3581-3584
-
Tidskriftsartikel (refereegranskat)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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| 11. |
- Branny, Artur, et al.
(författare)
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X-Ray Induced Secondary Particle Counting With Thin NbTiN Nanowire Superconducting Detector
- 2021
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 31:4
-
Tidskriftsartikel (refereegranskat)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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| 12. |
- Casalbuoni, Sara, et al.
(författare)
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COLDDIAG: A Cold Vacuum Chamber for Diagnostics
- 2011
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1051-8223. ; 21:3, s. 2300-2303
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Tidskriftsartikel (refereegranskat)abstract
- One of the still open issues for the development of superconducting insertion devices is the understanding of the heat load induced by the beam passage. With the aim of measuring the beam heat load to a cold bore and in order to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. We plan to have access with the same set-up to a number of different diagnostics, so we are implementing: i) retarding field analysers to measure the electron flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. COLDDIAG is built to fit in a short straight section at ANKA, but we are proposing its installation in different synchrotron light sources with different energies and beam characteristics. A first installation in DIAMOND is planned in June 2011. Here we describe the technical design report of this device and the planned measurements with beam.
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| 13. |
- Cayado, Pablo, et al.
(författare)
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Improved Performance of CSD-Grown Y1-xGdxBa2Cu3O7-BaHfO3 Nanocomposite Films on Ni5W Substrates
- 2020
-
Ingår i: IEEE transactions on applied superconductivity (Print). - 1051-8223 .- 1558-2515. ; 30:4
-
Tidskriftsartikel (refereegranskat)abstract
- Y1-xGdxBa2Cu3O7-BaHfO3 (YGBCO-BHO) nanocomposite films containing 12 mol% BHO nanoparticles and different amounts of Gd,x, were grown by Chemical Solution Deposition (CSD) on Ni5W substrates in order to investigate the impact of the rare-earth stoichiometry on the structure and superconducting properties of these films. For Gd contentsx>0.5, epitaxial YGBCO-BHO films with an approximate thickness of 270 nm self-field critical current density Jc at 77 K∼1,5 MA/cm² were obtained. The field dependence of the critical current density Jc (B) shows a much larger accommodation field and lower exponents α in Jc∼B−α values compared to pristine YBCO films. This is both due to the high amount of individual nanoparticles in the matrix as observed in TEM images and thehigher critical temperatures Tc. The results show that the CSD is a potential candidate for the preparation of REBCO films in long-length coated conductors.
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| 14. |
- Chukharkin Leonidovich, Maxim, 1980, et al.
(författare)
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Improvement of Ultra-Low Field Magnetic Resonance Recordings With a Multilayer Flux-Transformer-Based High-T-C SQUID Magnetometer
- 2013
-
Ingår i: Ieee Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 23:3
-
Tidskriftsartikel (refereegranskat)abstract
- We have developed a multilayer flux-transformer-based high-T-C SQUID (flip-chip) magnetometer that improves signal-to-noise-ratios (SNR) in ultra-low field magnetic resonance (ulf-MR) recordings of protons in water. Direct ulf-MR-based benchmarking of the flip-chip versus a standard planar high-T-C SQUID magnetometer resulted in improvement of the SNR by a factor of 2. This gain is attributable to the improved transformation coefficient (1.9 vs 5.3 nT/Phi(0)) that increased the signal available to the flip-chip sensor and to the lower noise at the measurement frequency (15 vs 25 fT/Hz(1/2) at 4 kHz). The improved SNR can lead to better spectroscopic resolution, lower imaging times, and higher resolution in ulf-MR imaging systems based on high-T-C SQUID technology. The experimental details of the sensors, calibration, and ulf-MR benchmarking are presented in this report.
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| 15. |
- Constantinian, K. Y., et al.
(författare)
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Spin-Triplet Superconducting Current in Metal-Oxide Heterostructures With Composite Ferromagnetic Interlayer
- 2016
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 26:3
-
Tidskriftsartikel (refereegranskat)abstract
- Superconducting heterostructures fabricated from oxide superconductor YBa2Cu2O7-delta and a composite ferromagnet La0.7Sr0.3MnO3/SrRuO3 interlayer and Au/Nb counter electrode were studied experimentally. Superconducting current was observed at magnetic field H raised up to 2000 Oe, which is greater than saturation magnetic field of manganite La0.7Sr0.3MnO3 (of order 100 Oe) and greater by a few orders than the value of magnetic field corresponding to penetration of one magnetic flux quantum. Microwave measurements of integer and half-integer Shapiro steps in conditions when relatively low external magnetic fieldH < 30 Oe was applied showed that the second harmonic in the current-phase relation of superconducting current becomes as big as the first harmonic. Fourier analysis of I-C(H) dependence allows extracting the components of fractional periods in I-C(H) function that also confirms a deviation from the sinusoidal current-phase relation. The obtained experimental data are explained by theoretical models that predict a huge enhancement of the second harmonic of the spin-triplet component in the superconducting current. The current-phase relation could be controlled by an external magnetic field, changing the directions of magnetization in the composite bilayer ferromagnet, which is inserted between two spin-singlet superconductors.
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| 16. |
- de Graaf, Sebastian Erik, 1986, et al.
(författare)
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Accurate Real-Time Monitoring of Quality Factor and Center Frequency of Superconducting Resonators
- 2014
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 24:6
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we track both center frequency and quality factor of a superconducting microwave resonator with very high precision using a modified Pound-Drever-Hall frequency locking scheme. The quality factor measurements can be done with high enough bandwidth to study different processes in a superconducting resonator in real time. With this added functionality, the frequency readout remains unaffected, with typical accuracy around 10-30 Hz/root Hz, whereas the cavity loss rate can be determined to within 0.1% on a millisecond time scale (34 dB/root Hz). As we demonstrate, this can be particularly useful for electron spin resonance measurements, where we achieve a minimum number of detectable spins coupled to the resonator N = 5 . 10(5) spins/root Hz, based on quality factor measurements. It also enables the study of fast dynamic processes, for example, vortex dynamics, in these devices on a short time scale.
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| 17. |
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| 18. |
- galletti, luca, 1986, et al.
(författare)
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High-Transparency Al/Bi2Te3 Double-Barrier Heterostructures
- 2017
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 27:4
-
Tidskriftsartikel (refereegranskat)abstract
- We have fabricated highly transparent Al/Bi2Te3/Al superconductor/normal metal/superconductor double-barrier heterostructures. Transport measurements reveal the presence of multiple Andreev reflections related to two distinct energy gaps that we identify as the induced superconducting gap in the two electrodes. The realization of high-transparency Josephson junctions with topological insulators is an important step towards the study of topological superconductivity and Majorana fermions.
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| 19. |
- 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
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 33:5
-
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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| 20. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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HTS/ferroelectric devices for microwave applications
- 1997
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 7:2, s. 2458 - 2461
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Tidskriftsartikel (refereegranskat)abstract
- High Temperature Superconducting (HTS, e.g. YBCO) microwave devices based on bulk or thin film ferroelectrics (e.g. Strontium Titanate-STO) are studied theoretically and experimentally. YBCO/STO/YBCO parallel-plate resonators and based on bulk single crystal STO are for electrically tunable high power filters, phase shifters and other devices in the frequency band 0.5-2.0 GHz of advanced microwave communication systems. Thin film YBCO/STO Inter-digital Capacitors (IDC), Coplanar Waveguides (CPW) phase shifters/delay lines are also designed and studied experimentally for low microwave power applications. Modelling problems of these devices and microwave losses in ferroelectrics are also discussed
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| 21. |
- Grivel, Jean-Claude, et al.
(författare)
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Effect of platinum group metal doping in magnesium diboride wires
- 2016
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 26:3
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of some platinum group metals (PGM = Rh, Pd, and Pt) on the microstructure and critical current density of Cu/Nb-sheathed MgB2 wires has been studied using Mg1-x PGM(x)B(2) powders with low doping levels. It was found that Pt and Pd do not enter the MgB2 lattice and have only limited influence on T-c. In contrast, some Rh can be substituted and induces a decrease of T-c. Secondary phases are formed when the solubility limit is exceeded, but they have different morphologies depending on the dopant. For some of these PGM elements, flux pinning improvements have been observed at low fields. The results are discussed in comparison with previous investigations using other transition metals for doping on the Mg site.
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| 22. |
- Gunbina, A. A., et al.
(författare)
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A 90 GHz SINIS detector with 2 GHz readout
- 2021
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 31:5
-
Tidskriftsartikel (refereegranskat)abstract
- A superconductor-insulator-normal metal-insulator-superconductor (SINIS) detector integrated in a planar 90 GHz band twin-slot antenna with a 2 GHz superconducting resonator readout was fabricated and experimentally studied. In order to achieve high pixel count, the traditional dc readout of the SINIS detector is replaced by NbN coplanar 13.850 mm long superconducting resonator. SINIS detectors have traditionally dc Junction Field Effect Transistor (JFET) room-temperature readout. Such readout requires individual wiring for each pixel, while the microwave readout is far less cluttered as only one coaxial line is needed for hundreds of devices. Such readout operates similar to frequency domain multiplexing (FDM) for microwave kinetic inductance detectors (MKID). The planar twin slot antenna has two parallel slots in a metal ground plane which are excited coherently by short sections of a coplanar waveguide (CPW) line with a SINIS detector at the center. One section of the CPW is extended past the slot in a long superconducting section which functions as a quarter wavelength resonator. This resonator is short circuited to the ground plane at the far end, with the expected open circuited end terminated by the SINIS detector in the antenna. We measured the response of sample to black body radiation temperatures 6 K and 9 K. The corresponding dynamic resistance maximum drops from 50 k down to 30 k. An RF readout channel comprising a coplanar coupler and a coplanar resonator has a resonant frequency of 1.8 GHz. Unloaded Q factor (without incoming irradiation) is 200. The signal spectral characteristics and the response to the black body radiation have shown design values as expected.
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| 23. |
- Gutierrez, Martí, 1993, et al.
(författare)
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A chip-based superconducting magnetic trap for levitating superconducting microparticles
- 2022
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 32:4
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetically-levitated superconducting microparticles have been recently proposed as a promising platform for performing quantum experiments with particles in the picogram regime. Here, we demonstrate the superconducting technology to achieve chip-based magnetic levitation of superconducting microparticles. We simulate and fabricate a chip-based magnetic trap capable of levitating superconducting particles with diameters from 0.5m to 200m. The trap consists of two stacked silicon chips, each patterned with a planar multi-winding superconducting coil made of niobium. The two coils generate a magnetic field resembling a quadrupole near the trap center, in which we demonstrate trapping of a spherical 50m diameter SnPb microparticle at temperatures of 4K and 40mK.
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| 24. |
- Hashimoto, T., et al.
(författare)
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Beamline test of a transition-edge-sensor spectrometer in preparation for kaonic-atom measurements
- 2017
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1051-8223. ; 27:4
-
Tidskriftsartikel (refereegranskat)abstract
- We are developing a new technique to apply transition-edge sensors (TESs) to X-ray spectroscopy of exotic atoms, especially of kaonic atoms. To demonstrate the feasibility of this pioneering project, performance of a TES-based X-ray detector was evaluated in pion- and kaon-beam environments at particle accelerators.We successfully observed X-rays from pionic-carbon atoms with a resolution as good as 7 eV FWHM at 6 keV. Also at a kaon beamline, we confirmed that the TES spectrometer will be able to achieve our resolution goal, 6 eV, in our first scientific campaign to measure X-rays from kaonic-helium atoms.
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| 25. |
- Haugen, O., et al.
(författare)
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High resolution thermal imaging of hotspots in superconducting films
- 2007
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 17:2/3, s. 3215-3218
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal imaging of hotspots in bridge structures of YbaCuO thin films is presented with micrometer resolution. Hotspots formed by passing transport currents are observed using a method based on the temperature dependence in the photoluminescence of a polymer thin film deposited on the superconductor. The hotspots are self maintained and have hysteretic behavior. An external magnetic field changes their behavior. The temperature distribution over the bridge and in its vicinity can be observed with a resolution better than 0.1 K. Also details of the experimental method will be reported.
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| 26. |
- Huang, J., et al.
(författare)
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Pulsed Field Stability and AC Loss of ITER PF Joints by Detailed Quantitative Modeling
- 2023
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 33:8
-
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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| 27. |
- Huang, MQ, et al.
(författare)
-
Small Scale Integrated Technology for HTS RSFQ Circuits
- 2001
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223. ; 11:1, s. 558-
-
Tidskriftsartikel (refereegranskat)
|
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| 28. |
- Huang, M, et al.
(författare)
-
Small scale integrated technology for HTS RSFQ circuits
- 2001
-
Ingår i: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223. ; 11:1, s. 558-561
-
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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| 29. |
- Högberg, Björn, et al.
(författare)
-
Novel in-situ fabricated Josephson Junctions: tyrilayer on a substrate slope
- 2003
-
Ingår i: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY ASC. - 1051-8223. ; 13:2, part 1, s. 794-796
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a high-temperature superconductor (HTS) Josephson junction geometry using only in situ interfaces and with the current flowing in the – plane of the HTS. The trilayer on a substrate slope (TOSS) junction is a HTS-barrier-HTS structure deposited in situ on top of a pre-etched slope in the substrate. We present initial results on the fabrication and testing of YBa2Cu3O7 TOSS junctions with a Ga-doped PrBa2Cu3O7 barrier. These devices display resistively shunted junction like – characteristics with characteristic voltages up to 5 mV at 4.2 K. The TOSS junction concept is of interest for fundamental studies of interfaces in HTS and can also be applied to an integrated circuit technology.
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| 30. |
- Khosropanah, Pourya, 1971, et al.
(författare)
-
Analysis of NbN Hot Electron Bolometer Receiver Noise Temperatures Above 2 THz With a Quantum Noise Model
- 2009
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 19:3, s. 274-277
-
Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes our receiver noise temperature data of NbN HEB mixers obtained at a number of local oscillator frequencies between 1.9 to 4.3 THz in order to verify the role of quantum noise. The experimental data show that the receiver noise temperature increases roughly linearly with frequency. At 4.3 THz, we measured a receiver noise temperature of 1300 K, which is about 6 times (hf/k B) . The noise data at different frequencies are compared to a prediction of a noise model including the contribution of quantum noise and making use of a hot-spot model for mixing. We draw a preliminary conclusion that at 4.3 THz roughly 30% of the receiver noise temperature can be ascribed to the quantum noise. However, more dedicated measurements are required in order to further support the quantum noise model for HEB mixers.
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| 31. |
- Krause, Sascha, 1989, et al.
(författare)
-
Ambient temperature growth of mono- and polycrystalline NbN nanofilms and their surface and composition analysis
- 2016
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 26:3
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the studies of high-quality 5 nmthin NbN films deposited by means of reactive DC magnetronsputtering at room temperature. The deposition withoutsubstrate heating offers major advantages from a processingpoint of view and motivates the extensive composition- andsurface characterization and comparison of the present filmswith high quality films grown at elevated temperatures.Monocrystalline NbN films have been epitaxially grown ontohexagonal GaN buffer-layers (0002) and show a distinct, lowdefect interface as confirmed by High-Resolution TEM. Thecritical temperature Tc of films on the GaN buffer-layer reached10.4 K. Furthermore, a poly-crystalline structure was observedon films grown onto Si (100) substrates, exhibiting a Tc of 8.1 Kalbeit a narrow transition from the normal to thesuperconducting state. X-ray photoelectron spectroscopy andreflected electron energy loss spectroscopy verified that thecomposition of NbN was identical irrespectively of appliedsubstrate heating. Moreover, the native oxide layer at the surfaceof NbN has been identified as NbO2 and thus, is in contrast to theNb2O5, usually claimed to be formed at the surface of Nb whenexposed to air. These findings are of significance since it wasproven the possibility of growing epitaxial NbN onto GaN bufferlayer in the absence of high temperatures hence paving the wayto employ NbN in more advanced fabrication processes involvinga higher degree of complexity. The eased integration andemployment of lift-off techniques could, in particular, lead toimproved performance of cryogenic ultra-sensitive terahertzelectronics.
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| 32. |
- Kuzmin, Leonid, 1946, et al.
(författare)
-
Multifrequency Seashell Slot Antenna With Cold-Electron Bolometers for Cosmology Space Missions
- 2016
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 26:3
-
Tidskriftsartikel (refereegranskat)abstract
- A novel type of the "seashell" multichroic polarized antenna is proposed for cosmology space missions. The polarized slot antennas are arranged in the compact form of a seashell with individual slots for each frequency and each polarization. Such an arrangement gives a unique opportunity for independent adjusting individual parameters of slots with microstrip lines (MSLs) and bolometers. For each frequency band, the seashell antenna contains two pairs of orthogonal slots for each polarization connected by MSLs with a bolometer in the middle for in-phase operation. To fit slots in the lambda/2 area for the best beam shape, lumped capacitances in the form of the H-slot were introduced. Ellipticity of a beam was improved to the level of better than 1%. The seashell antenna gives a unique opportunity to select the needed bandwidth using two options. The first option is the frequency selection by resonance properties of slots with MSLs and resistive cold-electron bolometer (CEB). The second option is the frequency selection by resonant CEB with an internal nanofilter organized by a kinetic inductance of the NbN superconducting nanostrip and a capacitance of the nanoscale superconductor-insulator-normal tunnel junction.
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| 33. |
- Kuzmin, Leonid, 1946, et al.
(författare)
-
Optimization of the cold-electron bolometer and a cascade quasiparticle amplifier in the voltage-biased mode
- 2022
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 32:4
-
Tidskriftsartikel (refereegranskat)abstract
- An optimized concept of the Cold-Electron Bolometer (CEB) with Superconductor-Insulator-Normal (SIN) Tunnel Junction and Andreev SN contact for voltage-bias mode has been developed. The responsivity of this design is much better than the widespread concept of the CEB with two SIN tunnel junctions for the current-biased mode (SINIS structure) due to degradation of responsivity by a factor of two in voltage-bias (VB) mode. Besides that, for the realization of the CEB with the same capacitance, we need twice larger junctions that lead to four times larger area and volume of the absorber. As a result, the NEP of one SIN junction CEB is half that of two SIN junction CEB. A novel concept of the quasiparticle cascade amplifier (QCA) based on harvesting the waste energy of relaxed quasiparticles without any additional voltage bias has been developed. The distinguish feature of the cascade principle is utilizing the same dc voltage as used for CEB. The cascade principle of signal amplification proved to be possible due to the conversion of electrons to holes in the second absorber. The amplifier is based on the optimized CEB with one SIN junction and one SN contact. The coefficient of power amplification of the incoming signal to the potential energy of hot quasiparticles is huge and can achieve a level of 140 at the optimal bias point. The coefficient of power amplification of the QCA can reach a value of 30 and more to overcome the noise of the SQUID amplifier. For a power load of 6 pW, the total NEP of the CEB is decreased to the level of pho-ton noise NEP, down to 0.7*NEPphot.
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| 34. |
- Kuzmin, Leonid, 1946, et al.
(författare)
-
Realization of the resonant cold-electron bolometer with a kinetic inductance nanofilter for multichroic pixels
- 2018
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 28:4
-
Tidskriftsartikel (refereegranskat)abstract
- A novel type of the resonant cold-electron bolometer (RCEB) has been realized for multichroic pixels. The internal resonance is organized by a kinetic inductance of the NbN superconducting nanostrip and a capacitance of the superconductor-insulator-normal (SIN) tunnel junctions. The basic idea of a multichroic system is to combine a wideband antenna and narrow-band RCEBs. We used a single Lambda slot with two RCEBs for 75 and 105 GHz, placed in the middle. Each RCEB included two SIN junctions with absorber connected to NbN kinetic inductance of 420 and 240 pH. SIN junctions had capacitances of 11 and 8 fF. Wave impedance of the slot antenna was near 15 Ω and resistance of the absorber was matched to this value. Matching of antenna with an external system was done by placing Si lens on the back side of a Si substrate. RF testing was done at 300 mK irradiating this chip by sweep generator from 60 to 120 GHz. The response curves showed clear resonances at 75 and 105 GHz with quality factor of 10 and 7. Kinetic inductance value was estimated at the level of 35 pH/sq. These experiments confirmed that the RCEB can be effectively used to create multiband elements.
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| 35. |
- Kuzmin, Leonid, 1946, et al.
(författare)
-
Single Photon Counter Based on a Josephson Junction at 14 GHz for Searching Galactic Axions
- 2018
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 28:7
-
Tidskriftsartikel (refereegranskat)abstract
- Axions and axion-like particles appear in well-motivated extensions of the standard model of particle physics and may be the solution to the long-standing puzzle of the dark matter in our Universe. Several new experiments are foreseen in the next decade searching them in a wide range of the parameter space. In the mass region from few to several tens of microelectronvolt, detector sensitivity will be limited by the standard quantum limit of linear amplifiers and a new class of single microwave-photon detector will be needed. We have developed a single photon counter based on the voltage switching of an underdamped Josephson junction that is coupled to a coplanar waveguide. By measuring the switching voltage, we can register single photons at 14 GHz with the rate less than 1 photon per 3000 s.
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| 36. |
- Lonardo, F., et al.
(författare)
-
Influence of the Heat Treatment on the Layer JC of Internal-Sn Nb3Sn Wires With Internally Oxidized Nanoparticles
- 2024
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 34:5
-
Tidskriftsartikel (refereegranskat)abstract
- We evaluated various heat treatments (HT) for maximizing the Nb 3 Sn layer thickness while retaining a refined grain microstructure in low filament count internal-Sn Nb 3 Sn Rod-In-Tube wires with internally oxidized nanoparticles. These wires were manufactured in our laboratory using SnO 2 as oxygen source and Nb alloys containing Ta and Zr or Hf. By reacting the wires at 650 °C for 200 hours we obtained relatively thin reaction layers but high layer critical current densities (layer J C ) of ∼3000 A/mm 2 for Hf-containing wires and ∼2700 A/mm 2 for Zr-containing wires, both at 4.2 K and 16 T. Notably, both of these values are over the layer J C threshold of 2500 A/mm 2 , which is estimated to be necessary for attaining the corresponding Future Circular Collider (FCC) target non-Cu J C of 1500 A/mm 2 . Following this heat treatment, the fine-grained Nb 3 Sn area occupies only ∼35% of the filament area for Hf-containing wires and ∼20% for Zr-containing wires. After heat treatments with a reaction step at 700 °C these values increase to 70–80% and ∼60%, respectively, with only a minor increase of the grain size. However, we observed a noticeable decrease in the layer J C for these HT. Magnetic measurements show that the high J C wires exhibit a point defect contribution from precipitates to the pinning force, which is missing in wires with depressed J C values. The higher heat treatment temperatures may have caused excessive coarsening of the oxide precipitates, to sizes unsuitable for flux pinning. Reaction heat treatment temperatures in the range of 650 °C to 700 °C and durations between 50 and 200 hours may provide a better compromise between the Nb 3 Sn layer thickness, its grain size and nanoparticle size.
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| 37. |
- Mangiarotti, Franco J., et al.
(författare)
-
Test of Short Model and Prototype of the HL-LHC D2 Orbit Corrector Based on CCT Technology
- 2019
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223 .- 1558-2515. ; 29:5
-
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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| 38. |
- Mangiarotti, Franco J., et al.
(författare)
-
Test of the First Full-Length Prototype of the HL-LHC D2 Orbit Corrector Based on Canted Cosine Theta Technology
- 2020
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223 .- 1558-2515. ; 30:4
-
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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| 39. |
- Mangiarotti, Franco, et al.
(författare)
-
Test Results of the CERN HL-LHC Low-beta Quadrupole Short Models MQXFS3c and MQXFS4
- 2019
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1051-8223 .- 1558-2515. ; 29:5
-
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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| 40. |
- Nawaz, Shahid, 1978, et al.
(författare)
-
Transport Properties of YBCO Nanowires
- 2011
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 21:3, s. 164-167
-
Tidskriftsartikel (refereegranskat)abstract
- We have carried out transport studies of YBa2Cu3O7-x (YBCO) nanowires. By exposing nanowires with microwaves, we see that short wires which have a flux-flow like current-voltage characteristic (IVC) clearly manifest current steps in the IVC (Shapiro steps). On the contrary, the longer wires exhibiting a resistively and capacitively shunted junction (RCSJ) model like current-voltage characteristic do not feature any Shapiro steps. The second case can be explained by taking into consideration the longer wire lengths where the wires loose coherency of flux flow due to inhomogeneity along the wire.
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| 41. |
- Nilsson, P A, et al.
(författare)
-
Planarized patterning of Y-Ba-Cu-O thin films for multilayer technology
- 1995
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 5, s. 1653-1656
-
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)
-
Broadband MgB2 Hot-Electron Bolometer THz Mixers operating up to 20K
- 2017
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 27:4
-
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)
-
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
-
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)
-
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.
|
|
| 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.
|
|
| 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)
-
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)
-
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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- Rossi, L., et al.
(författare)
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A European Collaboration to Investigate Superconducting Magnets for Next Generation Heavy Ion Therapy
- 2022
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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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