心磁图仪系统性能测试方法研究

心磁图仪作为一种新型医疗技术,其临床应用效果显著。为了可靠地检测心磁图仪产品,本文提出了受测者定位精度、磁场-电压转换系数、通道差异率、磁灵敏度、动态范围和系统采样率5项性能指标及其检测方法。这些指标有助于规范心磁图仪产品标准,保证其临床应用安全性和有效性。     

关于动态信号分析仪测量SQUID噪声的讨论

做为最灵敏的磁通－电压传感器超导量子干涉器（ＳＱＵＩＤ）通常用于测量微弱信号,因此,噪声水平是其主要特征指标。目前,ＳＱＵＩＤ的噪声功率谱主要是用ＨＰ公司的动态信号分析仪（Ｄｙｎａｍｉｃ Ｓｉｇｎａｌ Ａｎａｌｙｚｅｒ ３５６６５Ａ或３５６７０Ａ）来测量,仪器的设置不同,所得的测试结果差异很大。本文针对ＳＱＵＩＤ噪声的测试问题,根据实际的经验,对动态信号分析仪的设置进行几点讨论。     

超导量子干涉器及应用

作为灵敏度极高的磁传感器，超导量子干涉器的制作工艺日臻完善，它的应用也愈来愈接近现实。本文简要介绍它的原理及应用。     

低温电流比较仪及其应用

低温电流比较仪是当前国际上最准确的直流电流比例量具 ,其比例准确度能达到 10 -13 以上 ,且能实现任意的比例值 ,在电磁计量基、标准的建立中起重要的作用。     

基于SQUID的磁纳米粒子磁特性测量研究

基于超导量子干涉器件(SQUID)的高灵敏磁通电压转换特性,将探测磁纳米粒子磁特性的线圈的微弱磁信号转换成电压信号输出。设计了包含激励源模块,信号测量模块,人机交互模块的测量系统,并采用标定线圈完成了测量系统的标定,实测数据表明,该系统可用于对磁纳米粒子磁特性的测量,为后续研究适用于生物体内温度测量的方法提供了支持。     

超导量子干涉器件的冷却技术

超导量子干涉器件(SQUID)是应用约瑟夫逊效应发展起来的超导电子器件，是目前低温超导学的前沿学科之一。由于它对电磁讯号有特别高的灵敏度，可用于测量微电流(10^-14A)，微电压(10^16V)及弱磁．低磁化率等，当SQUID用作约瑟夫逊电压标准时，测量精度可达10^-10。     

超导磁分离工业废水处理技术研究

超导高梯度磁分离污水处理是一种新型的污水处理技术.采用超导磁体和经过表面有机改性的铁磁性颗粒为"磁种"与污水中非磁性有害物质絮接,通过强磁场分离COD值降到78 ms/L,污水净化效果良好.讨论了利用等离子体聚合薄膜制备具有强捕捉能力的磁性粒子工艺.     

射频超导量子干涉器探测弱磁场在材料检验上的应用

超导量子干涉器在交变外磁场的作用下其量子干涉效应的宏观尺度上呈现三角波特性曲线，再施于静磁场时特性曲线会移动，并有具有很高灵敏度，据此可探测弱磁场的存在有应用到材料检验上。     

Performance of a 2-hole Y-Ba-Cu-O rf SQUID

A two-hole rf SQUID has been fabricated out of bulk YBCO by drilling two holes and careful erosion of the wall between the holes. Commercial SQUID electronics is inductively coupled to the SQUID through a copper coil glued in one of the holes. Periodic oscillations in V-B characteristic of the SQUID are observed at 77 K. The spectral density of the flux noise in the white noise region is 5·5 × 10⁻⁴Φ₀ / √Hz. The flux noise is frequency-dependent below 200 Hz.     

High-Tc dc-SQUID magnetometer and its application in eddy current non-destructive evaluation

We have fabricated and tested a high-T_c dc-SQUID magnetometer patterned on a YBCO thin film deposited on a SrTiO₃ bicrystal substrate. The measurement of noise spectrum at 77 K showed that the magnetometer has a white noise of 333 fT/Hz^1/2 without superconducting shield, corresponding to a flux sensitivity of 14.5 μΦ₀/Hz^1/2. We constructed a test system for eddy current non-destructive evaluation of conducting aluminum plates by using the magnetometer. Flaws over 10 mm below the surface can be clearly identified. By mapping the magnetic field distribution, we can locate the flaw position. The signals caused by flaw were expanded due to the use of double-D type driving coil with a wider central slit. The experimental results confirmed that this test system could operate in a magnetic unshielded environment.     

A TDMA Hybrid SQUID Multiplexer

We have developed a multiplexed read-out for transition-edge sensors (TES) based on a hybrid time- and frequency-domain basis set, similar to that used in time-division multiple-access (TDMA) mobile phones. The hybrid basis set uses bandwidth more efficiently than microwave frequency-division SQUID multiplexing, making it possible to multiplex more detectors in each output line. The high open-loop bandwidth provided by our SQUID TDMA system also makes it possible to multiplex large arrays of fast, high dynamic range detectors such as fast x-ray calorimeters. In this approach, we embed the second-stage SQUID amplifier of our standard time-division multiplexer in an impedance matching circuit coupled to a broadband cryogenic high electron mobility transistor (HEMT) in a microwave reflectometer configuration. The input signals are flux coupled into the first-stage SQUID amplifiers whose signals are time-division multiplexed into the second-stage SQUID. At room temperature, the signal from the HEMT is mixed down to dc for analysis and further signal processing.      

SQUID与半导体样品的无损检测

随着半导体集成度的不断提高 ,半导体检测技术也不断拓展和更新。SQUID是目前所知的最灵敏的磁场和磁通探测器。本文将介绍一种以SQUID为探头的、非接触式的、半导体材料和器件检测装置。     

Recent Results of a New Microwave SQUID Multiplexer

We present recent results of a prototype microwave SQUID multiplexer containing four SQUIDs coupled to GHz frequency resonant circuits and fed with a single microwave readout line. The system is operating at a readout frequency range of 8–10 GHz. All four SQUIDs share a common DC bias and modulation lines. A new modulation scheme is tested to eliminate the need for individual flux biasing of the SQUIDs, which extends the dynamic range of the readout. In this scheme a common modulation signal is imposed on each SQUID and the received signal is demodulated at one and two times the modulation frequency to maintain sensitivity at any flux state. We also demonstrated a microwave RF bias scheme eliminating the necessity of the DC current bias to the SQUID. Our preliminary performance tests at 4.2 K show that the input noise of the device is ∼5 pA/ .      

SQUID current amplifiers for sub-kelvin operation temperatures

Extremely sensitive current sensors are being developed by integrating input coils on superconducting quantum interference devices (SQUIDs) and optimizing them for being cooled to the mK temperature range. The most important effects for this type of sensors are investigated in this paper. SQUID characteristics were experimentally studied at mK temperatures and in numerical simulations, revealing a crucial hysteretic effect originating from parasitic elements introduced by the integrated coil. Furthermore, the cooling behavior of shunt resistors with attached cooling fins, dominated by the hot-electron effect, was investigated. A numerical model allows to reproduce the experimental data in a good way.     

Cryostats for SQUID magnetometers

A non-metallic and non-magnetic cryostat, with a very low thermal budget and a container type autonomy was developed, to condition SQUID magnetometers whose maximum sensitivity reaches 10^?14$\text{T Hz}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$. This instrumentation uses composite materials, thermal shock and vibration resistant, multilayer thermal radiative insulation, to detect vibrations with thermal equivalent emissivity lower than 10^?3.     

Construction and test of a cryocooler-cooled low-Tc SQUID gradiometer system

A cryocooler-cooled low-Tc SQUID gradiometer system was designed and constructed. It is based on a 4 K GM-cooler that is positioned several meters from the measuring head containing the SQUID sensors. The cooling power is transported by means of a circulating helium flow. Thus, there are three main components: the cooler vessel, the measuring head and the connecting flow-line.In stable operation, the SQUID and gradiometric pick-up loop are about 4.3 K. The overall heat loads to the cooler 1st and 2nd stages are estimated at 17 W and 0.3 W, respectively. The overall system noise was about 10 fT/√Hz although a number of peaks were observed in the spectrum. As an example, an adult heart beat was recorded.     

A planar thin-film SQUID of high inductive coupling constant

An inductive coupling dc-SQUID has been developed which is a thin-film structure containing an input coil, a SQUID proper and a groundplane. The SQUID parameters are sensitive to the thicknesses of insulating layers between these components. The SQUID can provide a high coupling constant between the input coil and SQUID loop.     

Design and characteristics of HTSC SQUID magnetometer with a sensitivity of 10−13 THz−1/2

The results are presented of the experimental studies on forming weak links in yttrium ceramics by scribing and high-voltage discharge. The energy resolution of SQUIDs and the magnetic field sensitivity of magnetometers produced according to these methods were 6×10⁻²⁸ J/Hz and 10⁻²⁸ J/Hz, 5×10⁻¹³ T/Hz^1/2 and 2·5×10⁻¹³ T/Hz^1/2, respectively. Different designs of HTSC interferometers sensitive to the external magnetic field variation are described. The factors affecting the sensitivity of r.f. HTSC SQUID-magnetometers are considered.