1997 Fiscal Year Final Research Report Summary
Development of High T_C SQUID Magnetometer Systm
| Project/Area Number |
08650496
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
計測・制御工学
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
ENPUKU Keiji Kyushu Univ., ISEE,Dept.of Electronic Device, Associaee Prof., 大学院・システム情報科学研究科, 助教授 (20150493)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Keiji Kyushu Univ., ISEE,Prof., 大学院・システム情報科学研究科, 教授 (80108670)
KISU Takanobu Kyushu Univ., ISEE,Associate Prof., 大学院・システム情報科学研究科, 助教授 (00221911)
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| Project Period (FY) |
1996 – 1997
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| Keywords | SQUID magnetometer / High Tc superconductor / Josephson junction / Bicrystal junction / 30 degre misorientation angle / l / f noise / Directly-coupled magnetometer |
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| Research Abstract |
In this project, we have developed superconducting quantum interference device (SQUID) using high T_C supercnductors. First, we clarify requirements for the development of high performance SQUID magnctometer. We show that the critical ctqrrentI_O and the resistance R of the Josephsonjunction should be I_O=20muA and R=10 OMEGAat T=77K,and the SQUID inductance shouldbe L=50-I50pH.When these requiremts are satisfied, we can expect high prformance magnetometer with magnetic fild resolution of B_n=20 fT/Hz^</2>.
In order to satisfy these requirements, we have developedd Josephson junctions fabricated on SrTiO_3 bicrystal substrates. Optimum value of the misorientation angle of the bicrystal substrate has been found be 30 dbgrees. Using the 30 degree substrate, we have succeeded, for the first time, in rcalizing the Josephson jucticn with I_o=20 muA and R=10 OMEGA. We have also shovm tnt the pcrformance of the SQUID operating at T=77K is significantly improved in this case. The performance obtained from the 30 degree bicrystal junction is cxtremely good when compared to the conventional SQUIDs.
The so- called directly-couled SQUID magnetometer has been also developed, where pickup coil snd 100-pH SQUID are integrated on 1cmx1cm SrTiO_3 substrate. The magutic field rcsolution of the magnetometer was measured to be B_nn=30 fT/Hz^</2n>fT/Hz^<1/2>, which is close to the dcsign value. This value is the lowestvalue rcprted so far in the directly-coupled SQUID magnetometer, and is enough for the meauresment of magnetocardiogram.
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