交流约瑟夫森电压合成装置的研究

设计制作了一套交流约瑟夫森电压合成装置(JAWS),能够驱动1 V SINIS型可编程约瑟夫森结阵合成峰值1.2 V、 200 Hz以下频率的交流量子电压。实验结果表明,该装置能够合成200 Hz以下频率的交流量子电压,且合成60 Hz交流电压的不确定度优于5×10^-6,为进一步开展我国首个交流量子电压基准的研究工作奠定了基础。     

交流量子电压标准研究综述

相比于传统的实物电压标准,基于约瑟夫森效应建立的交流量子电压标准,具有复现性好、稳定性高和不确定度低等优点。从物理原理、存在问题以及应用价值等角度出发,梳理、归纳先后发展起来的可编程约瑟夫森电压标准和脉冲驱动的交流约瑟夫森电压标准,并比较这两种量子电压标准的计量性能,介绍我国构建交流量子电压标准的现状及进展。     

约瑟夫森电压标准的国际比对

不同国家的六个计量实验室用齐纳二极管作为传递电压标准进行了电压标准的国际。比对结果在测量不确定度内是吻合的，它仅受齐纳稳定性的限制。对于１．１０８Ｖ的输出而言，数据与线性回归拟合具有０．０４７μＶ的残余标准偏差。从而有可能据此证实西班牙ＴＰＹＣＥＡ新１Ｖ约瑟夫森电压标准的性能。     

基于约瑟夫森量子电压的交流功率测量系统及方法研究

基于约瑟夫森量子电压标准设计了交流功率差分测量系统。通过分析差分采样系统的误差分布及误差传递函数,提出换向差分测量方法,减小了差分采样系统的增益误差,提高了电压幅值测量准确度;通过分析衰减系数η,证明了采用换向差分测量较容易实现10-7量级电压幅值测量。通过评估差分采样系统零相位,结果证明了差分采样系统具有较好的相位测量稳定性。分析了交流功率差分测量系统的不确定度分量,评估了功率因数为1.0,0.5 L和0.5 C时的功率测量不确定度,通过与国家交流功率基准装置进行实验比对,证明了基于约瑟夫森量子电压交流功率测量系统不确定度评估的合理性。     

1V及10V约瑟夫森结阵电压标准

为建立国家法定电压基准,中国计量科学研究院(NIM)对1-V和10-V约瑟夫森串联结阵电压标准进行了研究。其中结阵分别是由德国的PTB,日本的ETL,美国的NIST和韩国的KRISS提供的。采用的微波源是一个锁定到10MH_z频率标准上的高稳定高功率的85GH_z的G_aA_s耿氏管振荡器。所获得的1_v和10-V电压的总不确定度分别是9E-9和6E-9。     

10V约瑟夫森结阵电压基准

在 1V约瑟夫森结阵电压基准的基础上 ,10 V约瑟夫森结阵电压基准于 1999年底在中国计量科学研究院量子部电压实验室建立。其校准电压在 0 .1V～ 10 V范围内连续可调。校准固态电压标准 10 V输出值的合成不确定度为 5.4× 10 -9(1σ)     

我国的1V及10V约瑟夫森量子电压基准装置

文章描述了我国量子电压基准的建立、发展、现状和所取得的成果,以及与国际计量局进行基准关键比对的情况。     

交流功率标准构建原理及发展趋势综述

交流功率标准作为电能计量最重要的溯源源头,对确保电能贸易结算的公平公正具有基础支撑作用。对目前构建高精度交流功率标准的常用方法以及功率量值溯源的链路进行了阐述。通过分析基于交流功率标准的电能表校准过程的误差来源,确立了主要的测量不确定度分量。针对现有交流功率标准存在的局限性,以及新型电力系统对电能计量提出的新需求,展望了电能计量标准未来的发展趋势。     

1V脉冲驱动型交流量子电压源研究

脉冲驱动型交流量子电压标准ACJVS通过高速脉冲序列驱动约瑟夫森结阵芯片的方式实现宽频带交流量子电压的合成,相比于可编程型交流量子电压标准PJVS,具有免台阶切换、频谱纯净、频带宽等优点。搭建的系统主要包括8位高速脉冲码型发生器、微波放大器、直流阻断、约瑟夫森结阵芯片等。通过驱动包含4个子阵列,每个子阵列含12810个约瑟夫森结的结阵芯片,并结合4通道联合低频补偿的方式,成功产生了1V有效值的脉冲驱动型交流量子电压,为进一步建立交流量子电压基准打下了坚实的基础。最后,展望了脉冲驱动型交流量子电压在量子阻抗桥、交流量子功率源、交流量子功率表方面的应用价值。     

Correction of Systematic Errors Due to the Voltage Leads in an AC Josephson Voltage Standard

The National Institute of Standards and Technology (NIST) has recently reported the first application of a quantum ac Josephson voltage standard for the calibration of thermal transfer standards in the 1- to 10-kHz frequency range. This paper describes preliminary work on extending its frequency calibration range up to 100 kHz by correcting the systematic errors due to voltage leads. A ground loop created by the dc blocks, which is a previously unaccounted source of high-frequency systematic error, has been identified, and its effects are partially mitigated.      

Progress Toward a 1 V Pulse-Driven AC Josephson Voltage Standard

We present a new record root mean square (rms) output voltage of 275 mV, which is a 25% improvement over the maximum that is achieved with previous ac Josephson voltage standard (ACJVS) circuits. We demonstrate the operating margins for these circuits and use them to measure the harmonic distortion of a commercial digitizer. Having exceeded the threshold of 125 mV rms for a single array of Josephson junctions, we propose and discuss the features of an eight-array circuit that is capable of achieving 1 V rms. We investigate the use of a resistive divider to extend the ACJVS voltage accuracy to higher voltages. By the use of a switched-input measurement technique, an integrating sampling digital voltmeter, a resistive voltage divider, and ACJVS synthesized sine waves as reference voltages, we characterize the stability of a commercial calibration source for a few voltages up to 2.7 V.      

An AC Josephson Voltage Standard for AC–DC Transfer-Standard Measurements

We describe the traceability chain of length measurements at Centre for Metrology and Accreditation (MIKES) from atomic clocks to the lasers of primary interferometers. Crucial part of the traceability chain, an optical frequency comb generator linking optical frequencies to atomic clocks, is described in detail. The frequency comb generator is used in frequency calibrations of iodine-stabilized lasers, which are operated in compliance with the recommendations of the practical realization of the definition of the meter. Measured absolute frequencies of iodine-stabilized lasers, time records of the measurements, and the respective Allan deviations demonstrate the solid performance of the MIKES laser frequency standards. The results are in good agreement with the recommended values, as well as with the independent characterizations of the measured lasers     

Precision Differential Sampling Measurements of Low-Frequency Synthesized Sine Waves With an AC Programmable Josephson Voltage Standard

We have developed a precision technique to measure sine-wave sources with the use of a quantum-accurate ac programmable Josephson voltage standard. This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high-purity and low-frequency (a few hundred hertz or less) sine-wave voltages. We have performed a variety of measurements to evaluate this differential technique. After averaging, the uncertainty obtained in the determination of the amplitude of a 1.2 V sine wave at 50 Hz is 0.3 $muhbox{V/V}$ (type A). Finally, we propose a dual-waveform approach for measuring two precision sine waves with the use of a single Josephson system. Currently, the National Institute of Standards and Technology (NIST) is developing a new calibration system for electrical power measurements based on this technique.      

Systematic-Error Signals in the AC Josephson Voltage Standard: Measurement and Reduction

We investigate the dominant frequency-dependent systematic-error signals (SESs) in the AC Josephson voltage standard. We describe our error measurement technique and a number of methods to reduce the errors. Most importantly, we found that a small change in on-chip wiring significantly reduces the SES, improves SES measurement stability, and enables a suitable bias correction method. We show that direct analog-to-digital converter measurements of the SES of two on-chip Josephson arrays are in very good agreement with errors inferred from AC-DC transfer standard measurements. Finally, we demonstrate that the reduction of the SES using these techniques greatly improves the agreement between the AC-DC differences of the two arrays as well as the absolute AC voltage accuracy.     

Recent NPL Work on the AC Josephson Effect as a Voltage Standard

The experimental equipment and procedure used in the latest National Physical Laboratory (NPL) ac Josephson effect determinations of 2e/h are described. The most recent value, obtained in April 1972, is 483 594.00 (±0.10) GHZ/VNPL and this, together with earlier results, provides information concerning the stability of the NPL maintained voltage standard over the past two years. To obtain a further increase in precision, new equipment is being developed for the measurements in which the resistive divider and null detector are maintained at cryogenic temperatures.     

AC–DC Transfer Standard Measurements and Generalized Compensation With the AC Josephson Voltage Standard

We present AC-DC transfer standard measurements using the National Institute of Standards and Technology's pulse-driven AC Josephson voltage standard source. We have investigated the frequency dependence for several output voltages up to 200 mV for frequencies from 2.5 to 100 kHz. We found that, as the frequency increases, the ac-dc differences for the two arrays on the same chip do not agree. We explored this deviation in ac-dc difference for the two arrays by investigating different configurations of the probe cabling and wiring, chip carriers, and on-chip circuit design. We found that the circuit design produced the greatest improvement, particularly at the highest frequency (100 kHz), where the deviation in ac-dc difference was reduced by more than 60%. In this paper, we also demonstrate tenfold higher output voltages and improved operating margins for arbitrary (nonsinusoidal) waveforms. These enhancements were accomplished by implementing a more general current bias to the arrays having the same harmonic content as that of the synthesized arbitrary waveform.     

Direct comparison between the NIST 10 V Conventional Josephson Voltage Standard and 2.5 V Programmable Josephson Voltage Standard

In the present paper, the intercomparison results of the NIST 10 V Conventional Josephson Voltage Standard (NIST10) and 2.5 V Programmable Josephson Voltage Standard (PJVS) Systems have been discussed. The two systems were directly intercompared at 1.018 V and 2.511 V from September 2006 to February 2007. The differences between the two systems (i.e. NIST10 — PJVS) at 1.018 V and 2.511 V were 0.21 nV and −0.95 nV respectively. The intercomparison results reveal that the noise of digital voltmeter (DVM) affects the measurement results significantly. Even with DVM of the same model, their noise rejection capability may be different when accuracy of a few nanovolt (nV) is required, although for Zener reference standard measurement, it is sufficient because the measurement uncertainty is dominated by the noise and non-linear drift of Zener reference standard.     

Coupling of Josephson Radiation to Voltage Standard Arrays

We coupled the radiation emitted by arrays of Josephson junctions oscillators to detector arrays of small Josephson junctions. The number of junctions in the detector array ranges up to 1536, which is typical for a 1V standard array operation. Evidence is presented that both uniform coupling of the emitted radiation over all the small junctions arrays and coherent emission of the Josephson oscillators can be achieved. PACS numbers: 74.50. + r, 74.40. + k.