V. N. Khorev

Magnetic flux density standard for geomagnetometers

A high-precision standard has been established to create a dc magnetic field in the expanded geomagnetic range 10 µT to 110 µT. Over this range the systematic standard uncertainty of the total magnetic field is (0.003 − 0.03) nT, with a random standard deviation of 0.002 nT, inside a sphere 10 cm in diameter. The uncertainty of the magnetic-field direction is 1 second of arc. A new type of three-component coil system, with an enlarged working space and an advanced potassium magnetic-field stabilizer, has been designed. The standard is intended for the calibration of high-precision geomagnetometers.

Precise standard system for low dc magnetic field reproduction

A standard system for low magnetic fields has been developed at the Korea Research Institute of Standards and Science. The system consists of a precision solenoid, He–Cs atomic magnetic resonance magnetometer, and apparatus for three-axis compensation of the Earth’s magnetic field. The variations of the Earth’s magnetic field are automatically compensated within 0.1 nT/h by a Cs atomic magnetic resonance field controller. The solenoid reproduces a dc field that is uniform at better than 3×10−7 within ±2 cm around the center. The experimentally measured coil constant and temperature coefficient of the solenoid are 1.231 0596×10−3 T/A (25 °C) and 3.8×10−7/°C, respectively. The standard serves for the calibration of magnetometers and uniform field coils, and also supports experiments related to research in magnetic fields in the range of (0.02–1.2) mT with (2–10)×10−6 uncertainty.

A high-precision system for direct current reproduction based on atomic magnetic resonance in helium-4

At the D. I. Mendeleyev Institute for Metrology (VNIIM) a high-precision system using helium-4 atomic magnetic resonance has been realized for the automatic reproduction and maintenance of direct current in the range 0.1 A to 1.0 A. A random standard uncertainty of 2 × 10-8 was obtained for stabilization at 1 A, with a non-linearity of less than 2 × 10-7 in the frequency-to-current conversion factor. The conversion factor was determined experimentally through the gyromagnetic ratio of helium-4 atoms and the calculable coil constant of a high-precision solenoid. The technique was used to determine the gyromagnetic ratio of the proton and for the accurate reproduction of the tesla using the calculable solenoid.

International comparisons to establish the traceability in the global network of geomagnetic observatories to SI units

The international comparisons in the field of earth-level dc magnetic flux density measurements with the participation of six National Metrology Institutes (NMIs) and four geomagnetic observatories (GMOs) have been carried out in 2013 and 2014 under the auspices of the Regional Metrology Organization Asia Pacific Metrology Programme (APMP). The obtained expanded uncertainty (k = 2) of the weighted mean value of correction values does not exceed 0.1 nT in the range of 20 μT to 100 μT, which was one of the main aims of this comparison. VNIIM (D I Mendeleyev Institute for Metrology) was the pilot laboratory for this comparison registered in the Key Comparison Data Base (KCDB) under index APMP.EM-S14. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Standard measuring system for calibration of magnetic flux density gradiometers

A standard measuring system (setup) has been developed at VNIIM to be used for the calibration of magnetic flux density gradient (MFDG) coils, sensors and magnetic gradiometers (MG). This measurement standard is based on the calculable quartz coil used for the reproduction of gradient which is uniform in a specified working space. It also includes measuring equipment to compare coils, gradiometers and differential measuring transducers. Theoretical and experimental aspects of the problem are discussed. The developed standard system allows calibrating MFDG coils with an uncertainty of 0.1 % within the range from 0.005 to 0.5 T/m.

Magnetic flux density standard for low magnetic field at KRISS

The low magnetic field standard system contains a precision solenoid, Cs-He precision magnetometer, and 3-component compensation of the Earths magnetic field (EMF). The solenoid produces a standard field which is uniform at better than 0.3 ppm within /spl plusmn/2 cm of the center. The EMF is automatically compensated to 0.1 nT. The standard serves the calibration of magnetometers in the range below 1 mT with 1 nT resolution.

High stabilization of DC-current source on the basis of atomic magnetic resonance in helium-4 [for proton gyromagnetic ratio measurement]

An atomic magnetic resonance based current source has been developed for a new measurement of the proton gyromagnetic ratio in low field. The high-stability current source is realized by the application of more precise magnetic-field-to-frequency converter. We used the method of /sup 4/He metastable spin polarization through optical pumping of Cs atoms, and also a newly designed two-layer solenoid for the purpose. The drift of current is less than 0.1 ppm/h and its random standard deviation is 0.05 ppm.

Development of the Standards Base in the Field of Measurements of Magnetic Induction and Magnetic Flux

The functional capabilities of State Primary Standard GET 12–2011 of the units of magnetic induction, magnetic flux, magnetic moment, and gradient of magnetic induction are investigated for the purpose of expanding the range of measurements in the transmission of the unit of magnetic induction into the area of measurements of strong and weak magnetic fields as well as in the transmission of the unit of magnetic flux by instruments for measuring the parameters of magnetically soft materials.

Reproduction of four base magnetic units in the unified standard of VNIIM

The described measurement standard is developed on the basis of modern magnetic measuring techniques to substitute three standards operated earlier at VNIIM. In the unified measuring system the standard reproduces four base units of magnetic quantities, as well as the ratios of these units to the ampere: magnetic flux density (MFD) - T, magnetic flux (MF) -Wb, magnetic moment - Am2 and MFD gradient - T/m. It allows realizing modern calibration system for magnetic measuring and reproducing instruments.

Metrological researces of proton and optical pumping geomagnetometers

The results of calibration of proton, cesium, potassium and helium-cesium scalar magnetometers in the range 20-100 muT are discussed. The calibration made it possible to apply corrections to reduce the uncertainty of measurements. Experimental data were obtained using a standard calibration system designed in the D.I. Mendeleyev Metrology Institute (VNIIM).