Electronic high-temperature radio frequency superconducting quantum interference device gradiometers for unshielded environment (original) (raw)
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Superconducting quantum interference device instruments and applications
Review of Scientific Instruments, 2006
Superconducting quantum interference devices ͑SQUIDs͒ have been a key factor in the development and commercialization of ultrasensitive electric and magnetic measurement systems. In many cases, SQUID instrumentation offers the ability to make measurements where no other methodology is possible. We review the main aspects of designing, fabricating, and operating a number of SQUID measurement systems. While this article is not intended to be an exhaustive review on the principles of SQUID sensors and the underlying concepts behind the Josephson effect, a qualitative description of the operating principles of SQUID sensors and the properties of materials used to fabricate SQUID sensors is presented. The difference between low and high temperature SQUIDs and their suitability for specific applications is discussed. Although SQUID electronics have the capability to operate well above 1 MHz, most applications tend to be at lower frequencies. Specific examples of input circuits and detection coil configuration for different applications and environments, along with expected performance, are described. In particular, anticipated signal strength, magnetic field environment ͑applied field and external noise͒, and cryogenic requirements are discussed. Finally, a variety of applications with specific examples in the areas of electromagnetic, material property, nondestructive test and evaluation, and geophysical and biomedical measurements are reviewed.
Noise properties of high-temperature superconducting dc-SQUID gradiometers
Physica C: Superconductivity, 2007
We have developed different types of superconducting magnetic field sensors based on high temperature superconducting (HTS) thin films. Here, we describe the fabrication of single layer dc-SQUID gradiometers with bicrystal Josephson junctions for operation in a flipchip configuration to improve sensor performance. High-quality thin films are known to be essential in achieving suitable electrical properties in these superconducting devices. The influence of sample processing on sensor performance is discussed. The most important parameter for practical applications is the field gradient resolution of the investigated dc-SQUID sensors. To determine this parameter for different gradiometer layouts we measured their noise properties in unshielded as well as magnetically or electrically shielded environments.
High-Tc superconducting detector for highly-sensitive microwave magnetometry
Applied Physics Letters
We have fabricated arrays of High-T c Superconducting Quantum Interference Devices (SQUIDs) with randomly distributed loop sizes as sensitive detectors for Radio Frequency (RF) waves. These subwavelength size devices known as Superconducting Quantum Interference Filters (SQIFs) detect the magnetic component of the electromagnetic field. We used a scalable ion irradiation technique to pattern the circuits and engineer the Josephson junctions needed to make SQUIDs. Here, we report on a 300 SQUID series array with the loop area ranging from 6 to 60 lm 2 , folded in a meander line covering a 3.5 mm  120 lm substrate area, made out of a 150 nm thick YBa 2 Cu 3 O 7 film. Operating at a temperature of T ¼ 66 K in an unshielded magnetic environment under low DC bias current (I ¼ 60 lA) and a DC magnetic field (B ¼ 3 lT), this SQIF can detect a magnetic field of a few picoteslas at a frequency of 1.125 GHz, which corresponds to a sensitivity of a few hundreds of fT= ffiffiffiffiffiffi Hz p and shows a linear response over 7 decades in RF power. This work is a promising approach for the realization of low dissipative subwavelength gigahertz magnetometers.
Performance of asymmetric superconducting quantum interference devices
Physica C: Superconductivity, 2002
Low T c superconducting quantum interference devices with asymmetric shunt resistances (SQUIDARs) have been numerically and experimentally investigated. Numerical simulations show that the flux to voltage transfer coefficient V U and magnetic flux noise S U are strongly dependent on both the asymmetry parameter q and damping parameter c ¼ R=R d , where R and R d are the SQUID normal resistance and damping resistance, respectively. For small c values, SQUIDARs show larger V U and smaller S U than symmetric devices. Asymmetric SQUIDs can then improve the performance of standard sensors in most of the magnetometric applications. By increasing c, V U several times larger than that of symmetric SQUIDs can be achieved. Therefore, it is possible to couple SQUIDAR magnetometers to an external preamplifier without the need of an external circuit, simplifying the read-out electronics. Experimental values of the magnetic field sensitivity of 6-7 fT/Hz 1=2 have been so far obtained. These results, already suitable for biomagnetic applications, can be further improved by properly optimizing the device parameters. Ó
High-T$_c$ superconducting antenna for highly-sensitive microwave magnetometry
arXiv (Cornell University), 2019
We have fabricated arrays of High-T$_c$ Superconducting Quantum Interference Devices (SQUIDs) with randomly distributed loop sizes as sensitive antennas for Radio-Frequency (RF) waves. These sub-wavelength size devices known as Superconducting Quantum Interference Filters (SQIFs) detect the magnetic component of the electromagnetic field. We use a scalable ion irradiation technique to pattern the circuits and engineer the Josephson junctions needed to make SQUIDs. Here we report on a 300 SQUIDs series array with loops area ranging from 666 to 60mum260\ \mu m^{2}60mum2, folded in a meander line covering a 3.5mmtimes8mm3.5\ mm\times 8\ mm3.5mmtimes8mm substrate area, made out of a 150150150-nm-thick mathrmYBa2mathrmCu3mathrmO_7\mathrm{YBa}_2\mathrm{Cu}_3\mathrm{O}_7mathrmYBa_2mathrmCu_3mathrmO_7 film. Operating at a temperature T=66KT=66\ KT=66K in a un-shielded magnetic environment, under low DC bias current ($I=60\ \mu A$) and DC magnetic field ($B=3\ \mu T$), this SQIF can detect a magnetic field of a few pTpTpT at a frequency of 1.125GHz1.125\ GHz1.125GHz, which corresponds to a sensitivity of a few hundreds of fT/sqrtHzfT/\sqrt{Hz}fT/sqrtHz, and shows linear response over 7 decades in RF power. This work is a promising approach for the realization of low dissipative sub-wavelength GHz magnetometers.
Journal of Applied Physics, 2000
We measured the amplitude-frequency characteristics of radio frequency superconducting quantum interference devices ͑rf SQUIDs͒ over a temperature range between 65 and 79 K. Using the expressions derived from the recently developed rf SQUID theory, valid also at large thermal fluctuations, we determined from these data the basic parameters of high-transition-temperature superconductor ͑HTS͒ rf SQUIDs. These parameters were: ͑a͒ the high-frequency coupling coefficient between the rf SQUID and the tank circuit resonator, k, ͑b͒ the SQUIDs hysteretic parameter, , ͑c͒ the critical current of the Josephson junction, I c , ͑d͒ its normal resistance, R n , and ͑e͒ its noise parameter, ⌫. We found a good agreement with the values of (I c) and R n determined directly after destructively opening the SQUID loop. In accordance with the theoretical predictions, our experimental results show that at large thermal fluctuation levels (TХ77 K), rf SQUIDs with large loop inductance operate in nonhysteretic mode up to  values exceeding 3. Furthermore, we have shown that the optimal energy sensitivity is attained in the nonhysteretic mode at a value of  distinctly higher than 1. A quantitative comparison of white noise predicted by the theory with that obtained from the experiment showed a reasonable agreement. We also discussed the contribution of the phase information to the SQUID's signal and noise at optimum operation conditions, when a mixer was used as a signal detector.
Superconducting Quantum Interference Filters as RF Amplifiers
IEEE Transactions on Applied Superconductivity, 2007
We propose Superconducting Quantum Interference Filters (SQIFs) as high sensitive magnetic field detectors. The SQIF is made of high critical temperature grain boundary Josephson junctions, and it is surrounded by an on chip superconducting pickup loop which enhances the magnetic field sensitivity of about 10 times with respect to the same SQIF without pickup loop. The devices are operated in Stirling microcoolers, at a temperature of about 70 K. In the presence of an applied magnetic field , SQIFs show the typical magnetic field dependent voltage response (), which is sharp delta-like dip in the vicinity of zero magnetic field. When the SQIF is cooled with magnetic shield, and then the shield is removed, the presence of the ambient magnetic field induces a shift of the dip position from 0 0 to a value 1 , which is about the average value of the Earth magnetic field, at our latitude. The low hysteresis observed in the sequence of experiments makes SQIFs suitable for high precision measurements of the absolute magnetic field. Typical magnetic flux noise spectra of SQIFs show a white noise level of about 0.6 T Hz. Comparative measurements of the direct spectra with the spectra measured by using noise reduction techniques reveal a significant decrease of the 1 noise levels. The experimental results are discussed in view of potential applications of high critical temperature SQIFs in magnetometry.
2009
Superconducting Quantum Interference Devices (SQUIDs) can have excellent spin sensitivity depending on their magnetic flux noise, pick-up loop diameter, and distance from the sample. We report a family of scanning SQUID susceptometers with terraced tips that position the pick-up loops 300 nm from the sample. The 600 nm - 2 um pickup loops, defined by focused ion beam, are integrated into a 12-layer optical lithography process allowing flux-locked feedback, in situ background subtraction and optimized flux noise. These features enable a sensitivity of ~70 electron spins per root Hertz at 4K.
Applied Physics Letters, 2015
A very promising direction to improve the sensitivity of magnetometers based on superconducting quantum interference devices (SQUIDs) is to build a series-array of N non-interacting SQUIDs operating flux-coherently, because in this case their voltage modulation depth, DV, linearly scales with N whereas the white flux noise S U 1/2 decreases as 1/N 1/2. Here, we report the realization of both these improvements in an advanced layout of very large SQUID arrays made of YBa 2 Cu 3 O 7. Specially designed with large area narrow flux focusers for increased field sensitivity and improved flux-coherency, our arrays have extremely low values for S U 1/2 between (0.25 and 0.44) lU 0 /Hz 1/2 for temperatures in the range (77-83) K. In this respect, they outperform niobium/aluminium trilayer technology-based single-SQUIDs operating at 4.2 K. Moreover, with values for DV and transimpedance in the range of (10-17) mV and (0.3-2.5) kX, respectively, a direct connection to a low-noise room temperature amplifier is allowed, while matching for such readout is simplified and the available bandwidth is greatly increased. These landmark performances suggest such series SQUID arrays are ideal candidates to replace single-SQUIDs operating at 4.2 K in many applications. V