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.     

杂散光对紫外、可见分光光度计测量结果的影响及检定方法

影响紫外、可见分光光度计测量误差的因素很多,杂散光是误差主要来源之一。本文分析杂散光对该仪器测量结果准确性的影响,介绍杂散光的检定方法,以及减小杂散光的措施。     

Dielectric-Constant Gas-Thermometry Measuring System for the Determination of the Boltzmann Constant at PTB

Dielectric-constant gas thermometry is being further developed at PTB to measure thermodynamic temperature and the Boltzmann constant k at the triple point of water. Due to the small electric susceptibility of gases, the targeted relative uncertainty of k of the order of 2 ppm can be achieved only if gas pressures up to 7 MPa and special 10 pF capacitors for the susceptibility measurements, including very large multi-ring toroidal cross capacitors, are used. This required development of a huge measuring system having a large heat capacity. Since the temperature measurement must be traceable to the triple point of water at a level of the order of 0.1 mK, a corresponding stability and homogeneity of the thermal conditions has to be realized. The design of the system and data characterizing its thermal parameters is described. The experimental results are compared with estimations based both on simple models and finite-element calculations.     

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.     

浅谈分光光度法中的杂散光

文章通过杂散光对分光光度计准确度影响的理论分析,提出了其消除措施。     

Simple spectral stray light correction method for array spectroradiometers

A simple, practical method has been developed to correct a spectroradiometer's response for measurement errors arising from the instrument's spectral stray light. By characterizing the instrument's response to a set of monochromatic laser sources that cover the instrument's spectral range, one obtains a spectral stray light signal distribution matrix that quantifies the magnitude of the spectral stray light signal within the instrument. By use of these data, a spectral stray light correction matrix is derived and the instrument's response can be corrected with a simple matrix multiplication. The method has been implemented and validated with a commercial CCD-array spectrograph. Spectral stray light errors after the correction was applied were reduced by 1-2 orders of magnitude to a level of approximately 10(-5) for a broadband source measurement, equivalent to less than one count of the 15-bit-resolution instrument. This method is fast enough to be integrated into an instrument's software to perform real-time corrections with minimal effect on acquisition speed. Using instruments that have been corrected for spectral stray light, we expect significant reductions in overall measurement uncertainties in many applications in which spectrometers are commonly used, including radiometry, colorimetry, photometry, and biotechnology.     

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.     

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.     

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.     

Maintaining the Unit of Voltage at PTB via the Josephson Effect

In Section I a report on high precision voltage comparisons between the mean EMF of the former PTB voltage standard (consisting of a group of 39 saturated Weston cells) and the Josephson reference voltage is presented. The experiments were carried out with a total uncertainty (1 ?) of 4 parts in 108. The measured rate of change of the mean EMF during a 1?year period was - 1.3 X 10-7 V per year. This voltage stability is sufficient to maintain the unit of voltage by this group of standard cells for several months until a new comparison with the Josephson reference voltage becomes necessary. Due to the effects of thermal EMF's in the millivolt circuit of the measuring system used at present, the Josephson reference voltage (?3 mV) is only stable during a short time. In Section II a prototype cryogenic voltage standard developed at PTB is described. By immersing the main measurement components into the superfluid liquid helium bath, a long term voltage stability can be achieved. These components include the cryogenic resistive divider, consisting of a new copper alloy, and the SQUID null detector. The resistance ratio of the cryogenic resistive divider of 320:1 is determined by a ten-decade inductive voltage comparator operating at 84 Hz. The effects of power dissipation introduce only errors of second order because the currents in the calibration mode and the measurement mode are the same.     

支撑光学制造的几何量计量技术(英文)

几何量计量技术大量应用于光学制造业以检测零件质量和控制生产过程,是光学制造业的核心技术,涉及微纳米结构的几何量计量以及平面、球面、非球面、直纹曲面及自由曲面的面形计量.本文综述了德国联邦物理技术研究院支撑光学制造的部分计量技术.介绍了一种测量范围为25 mm×25 mm×5 mm的计量型大范围原子力显微镜(AFM),可灵活多样地测量各种微纳结构.介绍了一种新颖的AFM探针(ACP),可实现微纳结构侧壁形貌的直接、无损测量.介绍了一种应用Flared AFM探针的真三维AFM及其用于减少针尖磨损的矢量探测技术,可应用于各种纳米结构的真三维测量.介绍了可用于平面和中等曲面面形绝对测量的两种方法:差分型激光束偏转法和可溯源多路传感器法(TMS).讨论了面形测量中存在的挑战性难题.介绍了可用于面形测量的高精度三坐标测量机.     

Radiation Thermometry and Emissivity Measurements Under Vacuum at the PTB

A new experimental facility was realized at the PTB for reduced-background radiation thermometry under vacuum. This facility serves three purposes: (i) providing traceable calibration of space-based infrared remote-sensing experiments in terms of radiation temperature from  −173 °C to 430 °C and spectral radiance; (ii) meeting the demand of industry to perform radiation thermometric measurements under vacuum conditions; and (iii) performing spectral emissivity measurements in the range from 0 °C to 430 °C without atmospheric interferences. The general concept of the reduced background calibration facility is to connect a source chamber with a detector chamber via a liquid nitrogen-cooled beamline. Translation and alignment units in the source and detector chambers enable the facility to compare and calibrate different sources and detectors under vacuum. In addition to the source chamber, a liquid nitrogen-cooled reference blackbody and an indium fixed-point blackbody radiator are connected to the cooled beamline on the radiation side. The radiation from the various sources is measured with a vacuum infrared standard radiation thermometer (VIRST) and is also imaged on a vacuum Fourier-transform infrared spectrometer (FTIR) to allow for spectrally resolved measurements of blackbodies and emissivity samples. Determination of the directional spectral emissivity will be performed in the temperature range from 0 °C to 430 °C for angles from 0° to ±70° with respect to normal incidence in the wavelength range from 1 μm to 1,000 μm. 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.     

Recent Progress of the 2e/h Measurement at PTB

In this paper, an experimental setup is described with which the stability of the PTB voltage standard, consisting of a group of International Weston cells, can be monitored with a total uncertainty (1?) of 4 parts in 108 by means of the ac Josephson effect. The measured quotient of the fundamental constants 2e/h is given by 2e/h = (483 593.606 ± 0.020) GHZ/VPTB, May 1972.     

Real-time radiography at the NECTAR facility

A feasibility study has shown that real-time radiography using fission neutrons is possible at the NECTAR facility, when using an improved detection system for fast variations (Bücherl et al., 2009 [1]).Continuing this study, real-time measurements of slowly varying processes like the water uptake in medium sized trunks (diameter about 12 cm) and of slow periodic processes (e.g. a slowly rotating iron disk) are investigated successfully using the existing detection system.