Comparison of the Josephson voltage standards of VNIIM and PTB

Comparisons of the 1 V Josephson array voltage standard (JAVS) of the “D.I. Mendeleyev Institute for Metrology” (VNIIM), Russia, with that of the Physikalisch-Technische Bundesanstalt (PTB), Germany, were carried out in St. Petersburg in June 1999. The results of the direct comparison agree within an overall standard uncertainty of less than 1 nV. The results also show that direct comparisons are useful for detecting voltage offsets of a few parts in 10¹⁰. The reason for a small voltage offset in an SIS array was investigated at zero voltage level     

Voltage ratio technique used with the national RF standardattenuation measuring equipment at the PTB

With a new measuring system, the attenuation range of the national RF standard attenuation measuring equipment at the Physikalisch-Technische Bundesanstalt (PTB), Germany, has been extended to 60 db in the waveguide bands R 220 and R 320. Most of the system is automated to shorten the calibration and measurement time. The total uncertainty of measurement is estimated to be 0.0027 dB per 10 dB attenuation     

The AC Josephson Effect Monitoring of the Unit of EMF in Canada

The experimental program outlined is directed toward the utilization of the ac Josephson effect to maintain surveillance of the unit of EMF in Canada. Preliminary results indicate a weighted mean value of 2e/h = 483 593.0 ± 0.2 (0.4 ppm) GHz/VNRc(73) which is, at present, not precise enough to detect the small drifts normally encountered in the mean value of the standard cell group upon which VNRC is based.     

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.     

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.     

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

The NIST 10 V Compact Josephson Voltage Standard (CJVS) and 2.5 V Programmable Josephson Voltage Standard (PJVS) were directly compared at 1.018 V and 2.511 V in February 2007. The difference between the two systems at 1.018 V (CJVS — PJVS) was −0.09 nV with an expanded uncertainty of 4.72 nV or a relative uncertainty of 4.64×10⁻⁹ at the 95 % confidence level where as the difference between the two systems at 2.511 V was 0.00 nV with an expanded uncertainty of 4.04 nV or a relative uncertainty of 1.61×10⁻⁹ at the 95 % confidence level. These intercomparison results demonstrated the satisfactory performance of the CJVS system handling minor trapped flux in the array and the effectiveness of the “NISTVolt software” to manage step jumps in the measurements.     

Operation of NIST Josephson Array Voltage Standards

This paper begins with a brief discussion of the physical principles and history of Josephson effect voltage standards. The main body of the paper deals with the practical details of the array design, cryoprobe construction, bias source requirements, adjustment of the system for optimum performance, calibration algorithms, and an assessment of error sources for the NIST-developed Josephson array standard.     

First Direct Comparison of a Cryocooler-Based Josephson Voltage Standard System at 10 V

A commercially available and fully automated 10-V Josephson voltage standard system with a liquid helium free cooling has been developed as a result of the cooperation between the Institute of Photonic Technology and Supracon AG, both in Jena, Germany. The system operates with an array of 19 700 superconductor–insulator–superconductor Josephson tunnel junctions installed in a pulse tube cooler. A stable operation is achieved by the proper integration of the voltage standard circuit to the cold stage of the cryocooler. Different operation setups are discussed. A direct comparison of a cryocooler-based Josephson voltage standard system versus a liquid-helium-based system was performed at a voltage level of 10 V. We obtained a voltage difference of 1.3 nV with a total combined uncertainty of 2 nV. This corresponds to a relative uncertainty of $2 times 10^{-10}$.      

The Proposed Ampere Experiment at the PTB

The ampere may be realized by combining the results of two different NMR experiments. In contrast to the well-known methods, we describe here a novel approach whereby the first-order influence of the geometrical dimensions of the coils is eliminated by using one coil for weighing and for producing a magnetic flux density to which that of the low-field experiment is related.     

Determination of the SI Volt at the PTB

Work on an electrostatic measuring system for the determination of the SI volt and the conversion factor KV at the PTB is reported. The system consists of a so-called voltage balance and a generator for the dc measuring voltage. There is a need for the development of such a device with an uncertainty below 1 part in 106 because measurements with existing voltage balances, and results obtained by other methods show discrepancies of several parts in 106. In order to reduce the uncertainty and to simplify the apparatus a special measuring method was developed. The voltage/force transducer of the PTB voltage balance is formed from two coaxial cylindrical electrodes and the generated force is substituted for the force of gravity on a weight of 2 g. The electrode voltage is composed of a constant part of 10186 V, derived in a 1000-fold stepup from 10 standard cells, and a much smaller variable part used for balancing the scale beam by means of a control loop. Taking the root sum of squares the total relative uncertainty of the SI volt and of KV is expected to be less than 4 parts in 107.     

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.     

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.      

Microwave-Induced Constant Voltage Steps at Series Arrays of Josephson Tunnel Junctions with Near-Zero Current Bias

Microwave-induced, constant-voltage steps in the current-voltage characteristics of Josephson tunnel junctions are used as a reference voltage in cryogenic voltage standards. This relatively low reference voltage of a few millivolts could be increased by using series arrays of tunnel junctions instead of a single junction. Series arrays consisting of 2, 6, 14, and 54 tunnel junctions were tested at a frequency of 70 GHz. The use of this relatively high frequency and of lead-alloy base electrodes allows zero crossing steps of up to 34 mV to be observed for an array with only 54 junctions when irradiated by an RF power of 32 mW. The measurements were performed at 4.2 K.     

Determination of stray light at the PTB goniophotometer facility

For improved luminous flux measurements, the Physikalisch-Technische Bundesanstalt (PTB) was equipped with a new robotic goniophotometer. In order to characterize this instrument, to reduce the combined measurement uncertainty, and to determine the respective uncertainty components, the influence of stray light on the measurement results was investigated. Considering the specific structure of the robotic goniophotometer, stray light was measured on-line by means of a purpose-built “back-looking” photometer. By this means, the influence of the luminous intensity distribution of each individual light source with regard to its stray light could be considered. Before the first experimental application, the invented procedure was tested by means of calculations using mathematical models. In this paper, the mathematical model for the calculation of stray light in the goniophotometer room is presented together with the calculation results and the results of the first measurements. The achieved results indicate that the recommended stray light measurements can decrease the total relative standard measurement uncertainty of luminous flux measurements down to 2 × 10⁻³.     

交流约瑟夫森电压标准系统的介绍

本文介绍了交流约瑟夫森电压标准系统的性能。该系统是一种新型的交流量子电压计量装置,用于校准常用的直流和交流电压标准。通过测试几个福禄克5700A系列校准器,其电压为10V,频率是1k Hz了解到该系统在工业环境中的性能和操作方法。交流电压标准的测量不确定度小于1×10-6     

A Vacuum Infrared Standard Radiation Thermometer at the PTB

A thermal infrared radiation thermometer was jointly developed by the Physikalisch-Technische Bundesanstalt and Raytek GmbH for temperature measurements from − 150°C to 170°C under vacuum. The radiation thermometer is a purpose-built instrument to be operated with the PTB reduced-background infrared calibration facility. The instrument is a stand-alone system with an airtight housing that allows operation inside a vacuum chamber, attached to a vacuum chamber, and in air. The radiation thermometer will serve to calibrate thermal radiation sources, i.e., blackbody radiators, by comparing their radiance temperature to that of a variable-temperature reference blackbody inside the reduced-background calibration facility. Furthermore, since it can be operated under vacuum and in air, the instrument also allows the water- and ammonia-heat-pipe reference blackbodies of the PTB low-temperature calibration facility operated in air to be compared with the variable-temperature blackbody operated under vacuum. Finally, provided that sufficient long-term stability is achieved, the instrument shall be used as a transfer radiation thermometer to carry and compare the temperature scale of PTB by means of radiation thermometry to remote-sensing calibration facilities outside PTB. The mechanical, optical, and electrical designs of the instrument are reported. Results of investigations on the temperature resolution, size-of-source effect, and the reference function are given. The heat-pipe blackbodies operating in air are compared to the variable-temperature blackbody operated under vacuum by using the vacuum radiation thermometer. References to commercial products are provided for identification purposes only and constitute neither endorsement nor representation that the item identified is the best available for the stated purpose.     

PTB低温温标复现方法概述

本文介绍了PTB密封式三相点容器复现低温温标的方法,其中包括对样品静态、动态温度测量误差的分析,热阻、比热的计算以及三相点温度值的确定.     

Online imaging of initial DNA damages at the PTB microbeam

In an inter-disciplinary collaboration of Physikalisch-Technische Bundesanstalt (PTB), German Collection of Microorganisms and Cell Cultures (DSMZ) and Heinrich-Heine University, live-cell imaging has been established at the charged-particle microbeam facility of PTB. Candidate genes participating in DNA strand-break repair pathways such as PARP-1, MRE11, MSH2, MDC1 and p53BP1 have been modified to generate fluorescent fusion proteins. Using multi-cistronic expression vectors, stable genomic integration was achieved in HT-1080 fibroblasts. The aim of this study is to characterise and use these highly reliable cell lines for studying initial steps of DNA damage responses and kinetics of repair after microbeam irradiation with high- and low-linear energy transfer (LET) particles in living cells at physiological conditions.     

Voltage locking of dissimilar Josephson junctions in a resonant cavity

Effects of voltage locking in an array of dissimilar Josephson junctions via resonator coupling are investigated. Explicit conditions are given for N junctions connected in series to form a coherent array by using a common bias current. Problems due to losses in the connecting pads between junctions are studied.Research supported in part by the National Science Foundation.