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Development of high Tc SQUID magnetometer system for biological application

生物应用高Tc SQUID磁力计系统的开发

基本信息

批准号：
10650412
负责人：
ENPUKU Keiji
金额：
$ 2.5万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650412/
关键词：
SQUID magnetometer high Tc superconductor 30-degree bicrystal junction 1 f noise flux trapping flux dam pickup coil magnetocardiogram SQUID 磁気センサジョセフソン接合バイクリスタル基板 yf雑音トンネル効果

项目摘要

In this research, we developed high Tc SQUID magnetometer system for biological application. First, we developed high performance SQUID utilizing bicrystal junctions with 30-degree misorientation angles. with 30-degree bicrystal junction, we can routinely obtain the voltage modulation depth △V>20μV and the flux noise SィイD2ΦィエD2ィイD11/2ィエD1<12μΦィイD2oィエD2/HzィイD11/2ィエD1 at T=77 K. Transport and noise properties of the bicrystal junctions are also clarified.Next, the so-called direct-coupled magnetometer is fabricated. When we use a conventional pickup coil with wide line-width, we observed high 1/f noise. It is shown that the 1/f noise comes from the hopping of the flux trapped in the pickup coil. In order to avoid the flux trapping, we develop a new type of the pickup coil. The pickup coil consists of 4 parallel loop with narrow line-width and involves the so-called flux dam. With this pickup coil, we can significantly reduce the 1/f noise. The flux noise is reduced to SィイD2ΦィエD2ィイD11/2ィエD1=23 μΦィイD2oィエD2/HzィイD11/2ィエD1 at f=1 Hz. This value is only 2.3 times higher than the white noise of SィイD2ΦィエD2ィイD11/2ィエD1=10μΦィイD1oィエD1/HzィイD11/2ィエD1.In the present magnetometer, the size of the pickup coil is 6 mm by 3 mm, and the effective area of the magnetometer is AィイD2effィエD2=0.12 mmィイD12ィエD1. This means that the magnetic noise of the magnetometer is SィイD2BィエD2ィイD11/2ィエD1=SィイD2ΦィエD2ィイD11/2ィエD1/AィイD2effィエD2=460 fT/HzィイD11/2ィエD1 at f=1 Hz, and SィイD2BィエD2ィイD11/2ィエD1=175 fT/HzィイD11/2ィエD1 in the white noise region. If we use a large pickup coil with 10 mm by 10 mm size, the effective area will be AィイD2effィエD2=0.4 mmィイD12ィエD1. In this case, we can expect SィイD2BィエD2ィイD11/2ィエD1=138 fT/HzィイD11/2ィエD1 at f=1 Hz, and SィイD2BィエD2ィイD11/2ィエD1=52 fT/HzィイD11/2ィエD1 in the white noise region. This sensitivity will be enough for the application to the magnetocardiogram.

在本研究中，我们开发了一套生物应用的高温超导SQUID磁强计系统。首先，我们开发了高性能的SQUID利用双晶体结与30度取向角。用30 °双晶结，在T=77 K时，可常规地获得电压调制深度△V>20μV和磁通噪声S_（？）D_（？）同时也阐明了双晶结的输运和噪声特性。接下来，我们制作了所谓的直接耦合磁强计。当我们使用一个传统的拾取线圈与宽线宽，我们观察到高1/f噪声。结果表明，1/f噪声来源于拾取线圈中捕获的磁通的跳跃。为了避免磁通俘获，我们研制了一种新型的拾波线圈。拾波线圈由4个窄线宽的平行回路组成，并涉及所谓的磁通坝。有了这个拾波线圈，我们可以显著降低1/f噪声。在f=1 Hz时，磁通噪声降低到S D2Φ D2 Φ D11/2 Φ D1=23 μΦ D2 Φ D2/Hz Φ D11/2 Φ D1。该值仅比S μ D2Φ φ D2 φ D11/2 φ D1=10μΦ D1 φ D1/Hz φ D11/2 φ D1的白色噪声高2.3倍。在本磁力仪中，拾波线圈的尺寸为6 mm × 3 mm，磁力仪的有效面积为A μ D2 eff φ D2=0.12 mm φ D12 φ D1。这意味着磁力计的磁噪声为S D2 B D2 D11/2 D1=S D2Φ D2 D11/2 D1/A D2 eff D2=460 fT/Hz D11/2 D1（f=1 Hz），S D2 B D2 D11/2 D1=175 fT/Hz D11/2 D1（白色噪声区域）。如果我们使用10 mm × 10 mm的大拾波线圈，则有效面积将为A D2 eff D2=0.4 mm D12 D1。在这种情况下，我们可以预期在f=1 Hz时S D2 B D2 D11/2 D1=138 fT/Hz D11/2 D1，在白色噪声区域中S D2 B D2 D11/2 D1=52 fT/Hz D11/2 D1。这种灵敏度将足以应用于心磁图。