基于量子自然基准的新型电流计量技术研究

在现代军事计量中，电磁计量直接影响国防建设质量和武器技战水平。现有电学计量体系中，基于约瑟夫森效应和量子化霍尔效应的量子电压和量子电阻的基准装置已经完成建设并已投入应用，然而基于量子效应的电流基准仍处于探索阶段。本论文基于高灵敏度原子磁力仪技术提出一种新型电流计量技术，可将电流间接溯源至约瑟夫森效应、量子化霍尔效应和拉莫尔进动效应三种量子自然基准。该技术有潜力用于建设电流计量基准装置和研制基于量子自然基准的新型电流比较仪。具体阐述了电流计量及量值传递方案的物理思想和实施过程，并通过相关实验验证了方案的可行性。     

非十进大功率电阻的测量

本文叙述了用电流比较仪电桥测量非十进大功率电阻的原理、电桥参数的选择、电路连线方法及测量步骤等,从而扩展了电流比较仪电桥的使用范围。     

中国计量科学研究院建成的量子化霍尔电阻标准

国际计量委员会推荐 ,1990年 1月 1日起在世界范围内启用量子化霍尔电阻标准代替使用了几十年的电阻实物基准。中国计量科学研究院经过十几年的努力 ,于 2 0 0 3年建成了量子化霍尔电阻标准。自主研制了能满足实际量值传递工作要求的量子化霍尔器件 ,并建成了高精度的低温电流比较仪 ,以把量子化霍尔电阻量值传递到日常检定工作中使用的十进位电阻。课题成果中有多项独创性的成就。目前所建量子化霍尔电阻标准的不确定度为 10 -10 量级 ,达到国际领先水平。     

《中国计量》杂志（电子版）订单

国际计量委员会推荐,1990年1月1日起在世界范围内,启用量子化霍尔电阻标准代替电阻实物基准。中国计量科学研究院经过十几年的努力,在2003年建成了量子化霍尔电阻标准装置,并于2004年通过了鉴定。课题组自主研制了能满足实际量值传递工作要求的量子化霍尔器件,并建成了高精度的低温电流比较仪,以把量子化霍尔电阻量值传递到日常检定工作中使用的十进制电阻。课题成果中有多项独创性的成就。目前所建量子化霍尔电阻标准的不确定度达到10-10量级,跃居国际领先水平。     

中国的量子化霍尔电阻标准

国际计量委员会推荐,1990年1月1日起在世界范围内,启用量子化霍尔电阻标准代替电阻实物基准.中国计量科学研究院经过十几年的努力,在2003年建成了量子化霍尔电阻标准装置,并于2004年通过了鉴定.课题组自主研制了能满足实际量值传递工作要求的量子化霍尔器件,并建成了高精度的低温电流比较仪,以把量子化霍尔电阻量值传递到日常检定工作中使用的十进制电阻.课题成果中有多项独创性的成就.目前所建量子化霍尔电阻标准的不确定度达到10-10量级,跃居国际领先水平.     

中国计量科学研究院建成的量子化霍尔电阻标准

国际计量委员会推荐，1990年1月1日起在世界范围内启用量子化霍尔电阻标准代替使用了几十年的电阻实物基准。中国计量科学研究院经过十几年的努力，于2003年建成了量子化霍尔电阻标准。自主研制了能满足实际量值传递工作要求的量子化霍尔器件，并建成了高精度的低温电流比较仪，以把量子化霍尔电阻量值传递到日常检定工作中使用的十进位电阻。课题成果中有多项独创性的成就。目前所建量子化霍尔电阻标准的不确定度为10^-10量级，达到国际领先水平。     

中国计量科学研究院建成量子化霍尔电阻标准

国际计量委员会推荐，1990年1月1日起在世界范围内启用量子化霍尔电阻标准代替使用了几十年的电阻实物基准。中国计量科学研究院经过十几年的努力，在2003年建成了量子化霍尔电阻标准。课题组自主研制了能满足实际量值传递工作要求的量子化霍尔器件，并建成了高精度的低温电流比较仪，以把量子化霍尔电阻量值传递到日常检定工作中使用的十进电阻值。课题成果中有多项独创性的成就。目前所建量子化霍尔电阻标准的不确定度为10^-10量级，达到国际领先水平。     

大功率直流模拟电阻校准方法研究

正本文基于标准源表法开展模拟电阻的校准研究,针对大功率直流模拟电阻输入电流范围宽、可实现低至微欧级电阻的模拟等特点,研究提升电流测量准确度,直流小电压的测量验证等,从而提升直流模拟电阻的校准能力。一、直流模拟电阻器校准原理大功率直流模拟电阻的源表法校准原理如图1所示,被测模拟电阻器的电流输入端与直流电流比较仪一次电流端串联,     

量子化霍尔电阻国家标准的研究

中国计量科学研究院在2003年建成了量子化霍尔电阻标准装置。成功研制了系统的核心器件—量子化霍尔器件。并通过对低温电流比较仪系统及运行过程的研究,发现了氦气气压波动引起的冻结磁通蠕动导致的附加噪声是限制系统不确定度的主要原因。进而提出了一种新型的气压滤波器,消除了这些干扰因素。还改进了电路动态特性,改善了前馈补偿环节,把匝数比提高了8倍,信噪比也因而提高了8倍。完成的量子化霍尔电阻标准装置的综合不确定度为2.4×10-10(k=1)。     

QJ55KZ型直流比较仪电桥测量标准电阻的一种简便方法

<正>QJ55KZ型直流比较仪电桥测量标准电阻的方法属于过渡传递法。现对该方法进行详细介绍,并针对该特定方法介绍一种简便方法。一、QJ55KZ型直流比较仪电桥测量标准电阻的测量原理直流比较仪是一种绕组的回形变压器,由两个不同的电流源分别给标准电阻RS和被检电阻RX供电,当两个电阻上的压降大小相等、方向相反时,测出两个电流之比,由检流计G指示出它们电压相等时的平衡     

石墨烯在量子霍尔电阻中的应用

基于砷化镓的量子霍尔电阻自然基准需要在约1.5K的温度条件下运行,存在成本高和操作复杂等诸多问题。随着石墨烯材料独特电性能的发现,因其可以在约4.2K的温度复现量子霍尔效应而成为制作量子霍尔电阻的理想材料。各国专家围绕石墨烯在电学计量领域的应用开展了大量的工作,取得了可喜的进展。对当前石墨烯在量子霍尔电阻中应用的进展和存在的问题进行了总结,并对未来的发展进行了展望。     

A precise measurement of QHR at NIM [quantized Hall resistance]

Equipment for precise measurement of the quantized Hall resistance (QHR) at the National Institute of Metrology (NIM), Beijing, China, is described. The essential parts in this equipment are a resistance comparator of one-to-one ratio with a comparison uncertainty of 3×10^-8 and two specially designed resistor networks used for determining of the ratio between 12906.4035 Ω of QHR at i=2 and 10 kΩ or 1 kΩ. The transfer procedure from QHR to 10 kΩ or 1 kΩ can be completed easily with this equipment by a few one-to-one comparisons with a total uncertainty of 5×10^-8     

An AC-bridge for low-frequency measurements of the quantized Hallresistance

A simple circuit which makes possible the use of a resistance-ratio bridge based on a cryogenic current comparator (CCC) with both AC and DC is described. The different sources of uncertainty associated with the use of AC in a CCC bridge are discussed. It is shown that they should have an effect which does not exceed a few parts in 10 ⁹ of the resistance-ratio being measured, if the frequency is limited to a few hertz. This analysis is confirmed by experimental results of resistance-ratio measurements between the quantized Hall resistance (QHR) and a 100 Ω resistance standard carried out at DC, 1, 2, and 4 Hz. These measurements are, to the author's knowledge, the first accurate DC measurements of the QHR. They demonstrate that the quantization of the Hall resistance, observed with AC and for the frequency range studied here, remains complete to within a few parts in 10⁹ or better     

Comparison of the quantized Hall resistance and ohm NRC

A report is given of the progress towards the establishment of a quantized Hall resistance (QHR) measurement system suitable for maintaining the NRC (National Research Center of Canada) representation of the ohm. A system using a cryogenic current comparator bridge is described and compared to the previously reported 15 T, 20-mK potentiometric system. General problems concerning the use of the quantized Hall resistance to realize a representation of the ohm are discussed     

Degradation of GaAs/AlGaAs Quantized Hall Resistors With Alloyed AuGe/Ni Contacts

Careful testing over a period of 6 years of a number of GaAs/AlGaAs quantized Hall resistors (QHR) made with alloyed AuGe/Ni contacts, both with and without passivating silicon nitride coatings, has resulted in the identification of important mechanisms responsible for degradation in the performance of the devices as resistance standards. Covering the contacts with a film, such as a low-temperature silicon nitride, that is impervious to humidity and other contaminants in the atmosphere prevents the contacts from degrading. The devices coated with silicon nitride used in this study, however, showed the effects of a conducting path in parallel with the 2-dimensional electron gas (2-DEG) at temperatures above 1.1 K which interferes with their use as resistance standards. Several possible causes of this parallel conduction are evaluated. On the basis of this work, two methods are proposed for protecting QHR devices with alloyed AuGe/Ni contacts from degradation: the heterostructure can be left unpassivated, but the alloyed contacts can be completely covered with a very thick (> 3 μm) coating of gold; or the GaAs cap layer can be carefully etched away after alloying the contacts and prior to depositing a passivating silicon nitride coating over the entire sample. Of the two, the latter is more challenging to effect, but preferable because both the contacts and the heterostructure are protected from corrosion and oxidation.     

Accuracy of measurements of the quantized Hall resistivity by adirect current comparator type potentiometer: calibration using aJosephson potentiometer

The accuracy of measurements of the quantized Hall resistivity (QHR) by a direct-current-comparator (DCC)-type potentiometer is estimated based on a linearity calibration of the potentiometer using a Josephson potentiometer. The power coefficient contribution to the nonlinearity of the DCC potentiometer was found to be 0.15±0.02 p.p.m./(100 mV)² at 18.5±0.5°C in 1985 and 0.21±0.03 p.p.m./(100 mV)² at 20.5±0.5°C in 1988. The possibility of accurate measurements of the ratio QHR/R _STD with uncertainties less than 0.05 p.p.m. by the DCC potentiometer is discussed     

Leakage current detection in cryogenic current comparator bridges

Several tests have been developed to locate leakage currents in cryogenic current comparator (CCC) resistance ratio bridges used at NIST to measure ratios of 1000 Ω/100 Ω, 6453.2 Ω/100 Ω, and 10 kΩ/100 Ω. The major advantage of the tests is that they can be performed in situ using the sensitivity of the CCC bridge. These test procedures have been used to reduce the leakage error uncertainty of CCC ratio measurements, linking working standards to the quantized Hall resistance (QHR) and to the NIST calculable capacitor experiment. CCC bridges require that the current which passes through a standard resistor must equal the current through the appropriate CCC winding to very high precision. This can be difficult to verify at or below 1 pA because a large number of possible leakage paths exist. Errors due to six important leakage current paths are given, and the calculated changes in the resistance ratio are compared with measurements made with a controlled leakage resistance in a 100 Ω/1 Ω CCC bridge     

当代计量科学发展的新趋势

回顾了计量科学在日常生活和科学研究方面的重要性,指出以实物计量基准建立的计量单位制存在的问题.分析了以基本物理常数(真空光速值c0,元电荷e,普朗克常数h,波尔兹曼常数kB和阿伏加德罗常数NA)和原子的物理特性(约瑟夫森效应和量子霍尔效应)进行计量基本单位量子化研究的重要性和紧迫性.介绍了长度、质量、电学量、温度和时间等计量基本单位量子化研究的新趋势.简单介绍了欧盟计量科学研究计划新动向.