楊鴻昌臺灣大學：物理研究所陳智城Chen, Ji-ChengJi-ChengChen2007-11-262018-06-282007-11-262018-06-282006http://ntur.lib.ntu.edu.tw//handle/246246/54561The superconducting quantum interference device (SQUID) is one of the important applications of high-TC superconductors. Since the high sensitivity to magnetic fields, the SQUID magnetometers have been used in many researches on weak field detections. They have been widely used in non-destructive evaluation (NDE), scanning SQUID microscope (SSM), magnetocardiology (MCG), magnetoencephalography (MEG), and low field nuclear magnetic resonance (NMR). Most of the high-TC SQUID magnetometers in use are dc SQUIDs. The dc SQUID has two Josephson junctions in a superconducting ring. In an rf SQUID, there is only one Josephson junction. The signal of the rf SQUID is read out by a copper loop inductively coupled to the SQUID through a LC resonant circuit. A great improvement of high-TC rf SQUIDs was done by Zhang et al. in Jülich Research Center, Germany. They have developed many kinds of high-TC rf SQUIDs. The flux concentrator further improves the effective area of the magnetometer. The noise level can be as lower as that of high-TC dc SQUIDs. Recently, they used a substrate resonator which cause the SQUID more stable and to be set up more simply. In this work, I try to study the noise characteristics of the high-TC rf SQUID magnetometers. A new designed rf SQUID magnetometer is developed. The principle of rf SQUID and the development of high-TC rf SQUID magnetometer are introduced in chapter 1 The preparations of the flux concentrator and the rf SQUID are in chapter 2. Measuring procedures including the resonant frequency, the effective area and the noise spectral density are also in this chapter. Chapter 3 shows variations of the effective area and resonant frequency due to changing the size of the superconducting flux concentrator. The flux noise of the high-TC rf SQUID magnetometer is resonant-frequency-dependent. The experiment results are fitted by Chesca’s formula. In chapter 4, we developed a new design which is called an integrated rf SQUID magnetometer. The rf SQUID is fabricated directly onto the SrTiO3 substrate resonator. The same concept is used to design a integrated 1st order planar gradiometer in chapter 5.Chapter 1 Introduction 1 1.1 principle of rf SQUID 1.1.1 Flux relation of the SQUID loop 1.1.2 SQUID readout and LC resonant circuit 1.1.3 Flux-locked-loop and SQUID output 1.2 development of HTS rf SQUID magnetometer 1.2.1 First generation 1.2.2 Second generation 1.2.3 Third generation 1.2.4 SQUID with substrate resonator Chapter 2 Experiment 13 2.1 SQUID fabrication 1.1.1 Thin film deposition 1.1.2 Photolithography and etching 1.1.3 Bicrystalline substrate 2.2. Resonant frequency 2.2.1 Resonator 2.2.2 Network analyzer 2.3 Read-out of the rf SQUID 2.3.1 Set-up 2.3.2 SQUID electronics 2.3.3 Test mode output and V-Φ curve 2.3.4 Adjustment of the working point 2.4 Effective area 2.4.1 Field noise and effective area 2.4.2 Helmholtz coil 2.4.3 Estimation of effective area 2.5 Noise spectral density 2.5.1 Spectrum analyzer 2.5.2 Magnetic shielding Chapter 3 rf SQUID magnetometer coupled to substrate resonator 32 3.1 Basic idea 3.1.1 Substrate resonator 3.1.2 Washer-type flux concentrator 3.1.3 Flux noise and resonant frequency 3.1.4 Optimization of flux concentrator 3.2 Flux concentrator and effective area 3.2.1 rf SQUID magnetometer coupled to tank circuit 3.2.2 rf SQUID magnetometer coupled to substrate resonator 3.3 Resonant frequency of the substrate resonator 3.4 Noise performance Chapter 4 rf SQUID magnetometer integrated on substrate resonator 51 4.1 Basic idea 4.2 Results 4.2.1 Resonant frequency 4.2.2 Voltage-flux curve and effective area 4.2.3 Noise spectral density 4.3 Discussion Chapter 5 rf SQUID gradiometer integrated on substrate resonator 60 5.1 Concept of planar gradiometer 5.1.1 Introduction to gradiometer 5.1.2 rf double-hole gradiometer 5.2 Uniform field gradient 5.3 The first design of integrated gradiometer 5.3.1 Layout of the gradiometer 5.3.2 Results and discussion 5.4 The second design of integrated gradiometer 5.4.1 Layout of the gradiometer 5.4.2 Results and discussion Chapter 6 Conclusion 77 Reference 7911760361 bytesapplication/pdfen-US超導量子干涉元件磁量計superconductorrf SQUIDmagnetometerthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/54561/1/ntu-95-D90222007-1.pdf