| 61. |
- Stornaiuolo, D, et al.
(författare)
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Sub-Micron YBa2Cu3O7-x Biepitaxial Junctions
- 2009
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 19:3, s. 174-177
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Tidskriftsartikel (refereegranskat)abstract
- We report on the fabrication and properties of sub-micron YBa2Cu3O7-x off-axis biepitaxial junctions. The vision behind this work is to set up a reliable nanotechnology processing to improve junctions' performances and reproducibility through the reduction of their size. We will illustrate the fabrication procedure employed and show the results obtained on samples where the transport parameters were tuned in a predictable way. Also, proofs of a clean barrier structure with few facets and low disorder were obtained.
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| 62. |
- Svechnikov, S., et al.
(författare)
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Spiral antenna nbn hot-electron bolometer mixer at submm requencies
- 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. 3395-3398
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the phonon-cooled hot-electron bolometer (HEB) as a quasioptical mixer based on a spiral antenna designed for the 0.3-1 THz frequency band and fabricated on sapphire and high resistivity silicon substrates. HEB devices were produced from superconducting 3.5-5 nm thick NbN films with a critical temperature 10-12 K and a critical current density of approximately 10/sup 7/ A/cm/sup 2/ at 4.2 K. For these devices we reached a DSB receiver noise temperature below 1500 K, a total conversion loss of L/sub t/=16 dB in the 500-700 GHz frequency range, an IF bandwidth of 3-4 GHz and an optimal LO absorbed power of /spl sime/4 /spl mu/W. We experimentally analyzed various contributions to the conversion loss and obtained an RF coupling factor of about 5 dB, internal mixer loss of 10 dB and IF mismatch of 1 dB.
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| 63. |
- Tarasov, Mikhail, et al.
(författare)
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Arrays of Annular Antennas With SINIS Bolometers
- 2020
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 30:3
-
Tidskriftsartikel (refereegranskat)abstract
- For improving the dynamic range and sensitivity at high power load, we have integrated superconductor-insulator-normal metal-insulator-superconductor (SINIS) bolometers with a frequency selective surface (FSS)-based distributed absorber formed by a series and parallel array consisting of 25 annular antenna elements, each containing two SINIS bolometers. By using a design with 50 bolometers, we reduce incident power load on each bolometer, increase sensitivity and saturation power which is important for ground-based and balloon-borne telescopes with high background power loads. Our main detector pixel is optimized for a frequency band centered at 345GHz. The detectors are matched to incoming telescope beam by a back-to-back horn with a back reflector. Such a configuration improves both the efficiency and the bandwidth of the receiver. Measured voltage responsivity approaches 210(9) VW with an amplifier-limited voltage noise of 20nVHz(12), which corresponds to a NEP 10(-17) WHz(12). The linear voltage response for incoming power is observed for absorbed power of about 5 pW. The current responsivity for parallel array is 210(4) AW and the shot noise limited intrinsic noise equivalent power is NEP 510(-18)WHz(12). The noise equivalent temperature difference is NETD 100 KHz(12) at 2.7-K background radiation temperature.
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| 64. |
- Tarasov, Michael, et al.
(författare)
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Non-Thermal Absorption and Quantum Efficiency of SINIS Bolometer
- 2021
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 31:5
-
Tidskriftsartikel (refereegranskat)abstract
- We study mechanisms of absorption in two essentially different types of superconductor-insulator-normal metal-insulator-superconductor (SINIS) bolometers with absorber directly placed on Si wafer and with absorber suspended above the substrate. The figure of merit for quantum photon absorption is quantum efficiency equal to the number of detected electrons for one photon. The efficiency of absorption is dramatically dependent on phonon losses to substrate and electrodes, and electron energy losses to electrodes through tunnel junctions. The maximum quantum efficiency can approach n = hf/kT = 160 at f = 350 GHz T = 0.1 K, and current responsivity dI/dP = e/kT in quantum gain bolometer case, contrary to photon counter mode with quantum efficiency of n = 1 and responsivity dI/dP = e/hf. In experiments, we approach intrinsic quantum efficiency up to n = 80 electrons per photon in bolometer with suspended absorber, contrary to quantum efficiency of about one for absorber on the substrate. In the case of suspended Cu and Pd absorber, Kapitsa resistance protect from power leak to Al electrodes.
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| 65. |
- Tarasov, Mikhail, 1954, et al.
(författare)
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Optical Response of a Cold-Electron Bolometer Array Integrated in a 345-GHz Cross-Slot Antenna
- 2011
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 21:6, s. 3635-3639
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Tidskriftsartikel (refereegranskat)abstract
- Two series/parallel arrays of ten cold-electronbolometers with superconductor–insulator–normal tunnel junctionswere integrated in orthogonal ports of a cross-slot antenna.To increase the dynamic range of the receiver, all single bolometersin an array are connected in parallel for the microwavesignal by capacitive coupling. To increase the output response,bolometers are connected in series for dc bias. With the measuredvoltage-to-temperature response of 8.8 μV/mK, absorbervolume of 0.08 μm3, and output noise of about 10 nV/Hz1/2,we estimated the dark electrical noise equivalent power (NEP)as NEP = 6∗ 10−18 W/Hz1/2. The optical response down toNEP = 2∗ 10−17 W/Hz1/2 was measured using a hot/cold loadas a radiation source and a sample temperature down to 100 mK.The fluctuation sensitivity to the radiation source temperature is1.3 ∗ 10−4 K/Hz1/2. A dynamic range over 43 dB was measuredusing a backward-wave oscillator, a variable polarization gridattenuator, and cold filters/attenuators.
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| 66. |
- Tarasov, Mikhail, 1954, et al.
(författare)
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Power Load and Temperature Dependence of Cold-Electron Bolometer Optical Response at 350 GHz
- 2014
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 24:6, s. 1-
-
Tidskriftsartikel (refereegranskat)abstract
- Cold-electron bolometers (CEBs) integrated with twin-slot antennas have been designed and fabricated. Optical response was measured at bath temperatures of 0.06 to 3 K using blackbody radiation source at temperatures of 3 to 15 K. The responsivity of 0.3 * 10(9) V/W was measured at 2.7-K blackbody temperature that is close to the temperature of the cosmic microwave background. Optical measurements indicate quasi-optical coupling efficiency of up to 60% at low phonon temperature and low signal level. Estimations for bolometer responsivity were made for practical range of bath temperatures and blackbody radiation temperatures. The estimated ultimate dark responsivity at 100-mK bath temperature can approach S-V = 10(10) V/W and reduces down to 1.1 * 10(8) V/W at 300 mK for a device with absorber volume of 5 * 10(-20) m(3).
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| 67. |
- Tolkacheva, Elena, 1980, et al.
(författare)
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Influence of the Bias Supply Lines on the Performace of RSFQ Circuits
- 2005
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 15:2, s. 276-279
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Tidskriftsartikel (refereegranskat)abstract
- Two effects of the bias supply line on the performanceof RSFQ circuits have been studied: inductive coupling between the bias supply line and circuit inductances; effect of the mirrored current in the ground plane. The following results of the study are presented: 3D calculations and experimental measurements of inductivecoupling between parallel and perpendicular microstripsin presence of one and two ground planes; calculated margins dependence on the external magnetic field in RSFQ cell. Bias current density extraction method has been developed and implemented in RSFQ circuit design flow.
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| 68. |
- Trabaldo, Edoardo, 1990, et al.
(författare)
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Noise Properties of YBCO Nanostructures
- 2017
-
Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 27:4
-
Tidskriftsartikel (refereegranskat)abstract
- Voltage noise measurements on close to optimally doped YBa2Cu3O7-delta nanostructures have been performed. The measured resistance noise at temperature T = 96 K (above critical temperature T-C = 85 K) shows a quadratic dependence on the bias current, e.g., the voltage power spectral density S-V alpha V-2. Moreover, the normalized voltage noise S-V/V-2 is inversely proportional to the device volume. This is a clear indication that the noise is the result of an ensemble of independent resistive fluctuators, evenly distributed within the sample volume. For our structures, we obtain a product S-V/V-2 x Vol. = const. approximate to 6 x 10-(33) m(3)/Hz resulting in a Hooge's parameter 3.4 x 10(-4), which is among the lowest reported in literature. At lower temperature, T = 2 K (well below TC) the total voltage fluctuations are given by the combined effect of critical current fluctuations and resistance fluctuations. For the critical current noise, we obtain a product S-I/IC2 x Vol. = const. approximate to 6x10(-32) m(3)/Hz. The larger value of the relative critical current noise is most probably due to the fact that the critical current is determined by edge effects whereas the resistance is given by the total volume of the device.
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| 69. |
- Trabaldo, Edoardo, 1990, et al.
(författare)
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SQUID magnetometer based on Grooved Dayem nanobridges and a flux transformer
- 2020
-
Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 30:7
-
Tidskriftsartikel (refereegranskat)abstract
- We report noise measurements performed on a superconducting quantum interference devices (SQUID) magnetometer implementing YBa2Cu3O7-δ grooved Dayem nanobridges as weak links. The magnetometer is realized by coupling the SQUID to a flux transformer with a two-level coupling scheme using a flip-chip approach to improve the effective area of the SQUID. The measured magnetic flux noise of the SQUID is as low as 10 μ Φ0/√Hz, which corresponds to an equivalent magnetic field white noise of 60 fT/√Hz above 100 Hz at T=77 K.
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| 70. |
- Wallén, Erik
(författare)
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Quench analysis of a superconducting magnet with 98 coils connected in series
- 2003
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1051-8223. ; 13:4, s. 3845-3855
-
Tidskriftsartikel (refereegranskat)abstract
- A novel insertion device for electron storage rings called the MAX-Wiggler has been constructed at MAX-lab. The MAX-Wiggler is a cold bore superconducting wiggler magnet with 47 3.5-T poles and. a period length of 61 mm aimed for the production of X-rays at the 1.5-GeV electron storage ring MAX-II at MAX-lab. The MAX-Wiggler consists of 98 racetrack coils connected in series in the superconducting magnet and the total stored magnetic energy at the nominal maximum field strength of 3.5 T is 48 U. This paper describes the quench analysis of the magnet. Several protection schemes have,been evaluated, such as an external dump resistor and safety switch or subdivision of the series of coils into sections with shunt resistors or silicon diodes in parallel to each group of coils in a section. It has been found that the most suitable protection scheme, in order to prevent the superconducting coils from getting overheated, is subdivision with a shunt path containing silicon diodes operating at liquid helium temperatures. The MAX-Wiggler has been commissioned and it has survived the quenches occurring during the initial training of the superconducting coils.
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