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Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2023
One of the more challenging problems in cooling superconductors with cryocoolers is that of reducing the associated vibration and EMI caused by the motor and other moving parts. The problem is most serious with SQUID devices because of their extreme sensitivity to magnetic fields and to vibration in the earth's magnetic field. Thus, we concentrate this section on these applications. In the case of power applications of superconductors, the major concerns are efficiency, cost, reliability, and how to distribute the cold from a cold head to a large superconducting device. In that case, the cryocooler is often used to liquefy the boiloff from a cryogenic bath in which the superconductor is immersed.
SQUIDs
Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2022
The two main versions of the SQUID are the dc SQUID and the rf SQUID. The dc SQUID consists of a superconducting loop interrupted by two overdamped junctions, and the mean voltage averaged over the Josephson oscillations represents the output signal. The rf SQUID has only one junction in the loop that is coupled to a resonant LC circuit. The LC circuit (with forced voltage oscillations caused by an external rf current source) applies to the one-junction loop rf magnetic flux biasing, which is fundamental to the device operation. The output signal is the mean amplitude (averaged over intrinsic or transient processes) of the forced voltage oscillations across the resonant circuit. In both cases the output is a periodic function of the magnetic flux applied to the loop with period Φ0. Apart from the two basic configurations for the SQUID, there are also some modified versions, for example, the relaxation oscillation SQUID (Adelerhof et al., 1994; Drung, 1995) and the bi-SQUID (Kornev et al., 2009).
Magnetic Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The SQUID device may be configured as a magnetometer (a scientific instrument used to measure the strength and/or direction of the magnetic field) to detect incredibly small magnetic fields. A superconducting pick-up coil couples the SQUID to the ambient magnetic field. If a constant biasing current is maintained in the SQUID device, the measured voltage oscillates with the changes in phase at the two junctions, which depends upon the change in the magnetic flux.
Review of Candidate Techniques for Material Accountancy Measurements in Electrochemical Separations Facilities
Published in Nuclear Technology, 2020
Jamie B. Coble, Steven E. Skutnik, S. Nathan Gilliam, Michael P. Cooper
In contrast to traditional calorimetry measurements, which quantify material inventories via measurement of induced voltages from the Seebeck effect, microcalorimetry methods rely upon transition-edge sensors (TESs) operating within the superconduction regime.36 These cryogenically cooled detectors can quantify single-photon heating by measuring the small increases in resistance within the TESs. This in turn produces electrothermal feedbacks that are measured by a superconducting quantum interface device (known as SQUID) ammeter capable of measuring the minute perturbations in the magnetic field.34,36 In effect, microcalorimetry is designed to measure temperature changes due to interactions at the individual photon level and as such exhibits exceptional energy resolution (on the order of electron volts).33,34,36 As a result, microcalorimetry is able to resolve X-ray features such as doublets from the K transition that are indiscernible using traditional high-purity germanium (HPGe) gamma spectroscopy.
Structural, electrical and magnetic properties of Sr1-xBixTiO3-δ ceramics
Published in Philosophical Magazine Letters, 2020
Ceramic samples of Sr1-xBixTiO3, with x = 0.10, 0.20 and 0.30 have been prepared using a solid-state method. Stoichiometric amounts of TiO2 (Sigma Aldrich, ≥ 99.9%), SrCO3 (Sigma Aldrich, ≥ 99.9%), and Bi2O3 (Acros Organics ≥ 99.9%) were used. To compensate any losses of Bi content, 5% excess was used. The same steps of sample preparation as mentioned in Ref. [9] have been performed. The powder was mixed, pelletised and calcined at 1100°C for 2 h in an alumina crucible in air. Then, the pellets were ground well, pressed and sintered around 1400°C in air for 2 h, followed by annealing at the same temperature using 98% Ar and 2% H2 gases. XRD studies at room temperature were undertaken using a Stoe X-ray diffractometer with Cu-Kα radiation (λ = 1.5406 Å). The dc resistivity was measured using the four-probe method in an Oxford cryostat. The magnetic measurements were done using a superconducting quantum interference device (SQUID).
Study of the critical current density and the thermodynamic critical field in deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor
Published in Phase Transitions, 2018
Youssef Ait Ahmed, Ahmed Tirbiyine, Ahmed Taoufik, Hassan El Ouaddi, Habiba El Hamidi, Abdelhalim Hafid, Abdelaziz Labrag, Hassan Chaib
The sample cooling process was as follows: In the slow cooling rate, we cooled the sample from 160 to 90 K at a rate of about 2 K/min, and from 90 to 70 K with a cooling rate of 0.1 K/min, then kept it at this temperature for 20 h. The sample was directly cooled to 2 K at a cooling rate of 5 K/min. The average rate was 10 K/min. In rapid cooling conditions, the sample was immersed directly in the dewar at 2 K. Our work focused in this study on the slow cooling rate. The magnetic measurements were done with a Quantum Design SQUID (Superconducting Quantum Interference Device). The magnetic hysteresis cycles M (H) (0 < H < 1000 Oe) were typically measured between 2 and 15 K.