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Design and Optimization of RSFQ Based Digital SQUID for High Sensitive Measurement of Widely Varying Magnetic Fields

Foroughi, Farshad | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47479 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Fardmanesh, Mehdi
  7. Abstract:
  8. Analog SQUIDs have limited slew rate and dynamic range and these problems make it hard to operate SQUID systems in unshielded applications like Bio-magnetic imaging and NDE. Recently by combining analog SQUIDs and RSFQ Logic, new class of magnetic sensors are introduced. These sensors have an acceptable sensitivity and very high dynamic range. On the other hand these sensors, Which are called Digital SQUIDs, can be directly connected to digital signal processing stages. In This work, for first time, a digital SQUID completely based on i-directional RSFQ was designed and optimized. using Bi-directional RSFQ, one can significantly simplify the digital SQUID circuit design and therefore fabrication of the designed chip is also more feasible. In comparison with the other published designs, our design is simpler and is completely based on superconducting digital circuits.on the other hand, the proposed circuit is the first practical circuit based on bi-directional RSFQ. Bi-Directional RSFQ logic has a great potential to be used in ultra low power consumption circuits. In order to fabricate the designed circuit in HTS technology, a special sputtering system for HTS film deposition, was developed and manufactured. After optimization of sputtering system and sputtering parameters, a high quality HTS thin film was obtained. Benefiting from the high quality deposited thin film, Josephson junctions were fabricated. Fabrication of the HTS Josephson junctions is the first step for complex circuit fabrication. Josephson behavior in junctions was verified by fabrication of analog SQUIDs
  9. Keywords:
  10. Sputtering ; Superconducting Quantum Interference Device (SQUID) ; Deposition ; Digital SQUID ; Rapid Single Flux Quantum (RSFQ)

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