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Handbook of High Temperature Superconductor Electronics Part 8

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Tham khảo tài liệu 'handbook of high temperature superconductor electronics part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 7 High-Temperature RF SQUIDS V. I. Shnyrkov Institute for Low Temperature Physics and Engineering Academy of Sciences Kharkov Ukraine 7.1 INTRODUCTION Superconducting quantum interference devices SQUIDs are extraordinarily sensitive detectors of magnetic flux variations. These devices have numerous applications as sensors in a wide range of experiments in the fields of physics geology medicine biology and industry. The progress in technology and in understanding the origin of the noise in low-transition-temperature Tc SQUIDs brought a dramatic improvement in the resolution of electrical and magnetic measurements. Many rather new and nonstandard applications of SQUIDs have been reviewed in detail see reviews and contributions in Refs. 1 and 2. The discovery of high-Tc oxide superconductors by Bednorz and Muller 3 quickly made apparent that macroscopic quantum phenomena may be very useful for a number of electronic applications. High-Tc materials have opened new possibilities by increasing the operating temperature of superconducting instruments and sensors. The High-Tc SQUID was the first superconducting electronic circuit employing Josephson junction cooled by liquid nitrogen. The development of superconducting magnetometers operating at 77 K holds promise of expanding the useful range of application of these devices to include remote operation in the field Copyright 2003 by Marcel Dekker Inc. All Rights Reserved. and space where the availability of liquid helium as a cryogen may be limited by some factors 4 . In addition the wider range of operation temperature may permit measurement on room-temperature samples such as living tissue 5 nondestructive material evaluation with Joule-Thomson cryocooler in industry 6 and routine checks of moving samples with greater sensitivity 7 high-Tc SQUID microscopy 8 and convenience due to nitrogen cooling. However oxide superconductors have introduced some completely new problems. Because of the extremely short coherence length