Report to CGPM Consultative Committee for Electricity and Magnetism (CCEM) Dr Barry Inglis

1. Report to CGPM Consultative Committee for Electricity and Magnetism (CCEM) Dr Barry Inglis President of CCEM 15 November 2007

2. Overview • Key activities • Working Groups • Redefinition of Units – the CCEM position • Scientific developments in E&M • Strategic planning • BIPM Electricity Section work program

3. Working Groups • WGLF – Low Frequency • GTRF – WG on RF and Microwave • WGkg – Electrical Methods for monitoring the kg • WGACQHR – AC Quantised Hall resistance • WGRMO – collaboration with RMOs • WGSP – strategic planning • WGSI – redefinition of units

4. Redefinition of Units – the CCEM Position • That the SI be changed by adopting fixed values of e and h • That the ampere be defined in terms of the flow rate of elementary charges. • For example: • “The ampere is the electrical current equivalent to the flow of exactly 1/(1.602 176 53 1019) elementary charges per second.” • That no decision be taken until there is adequate agreement between independent experiments on the determination of h.

5. Main areas of scientific development in E&M • Programmable Josephson arrays • Calculable capacitors • Single Electron Tunnelling devices - Closure of the ‘quantum metrology triangle’ • Characterisation of non-sinusoidal/distorted waveforms • Watt balances • Terahertz measurement standards

6. Strategic Planning – priority areas • Remote calibration • E&M measurements in medicine, human body • Nanotechnology: nanomagnetics, spin electronics, EM metrology in nanostructures • Terahertz measurement, imaging – security • Single electronics and photonics • Quantum voltage generation and measurement • Quantum computing – qubits • Nano/bio- electronics • SI traceable HF and THz EM measurements.

7. BIPM Electricity Section

8. BIPM Electricity Section Work Program

9. Watt Balance Balancing weight against electromagnetic force to determining the kilogram in terms of electrical units and hence fundamental constants through the Josephson effect and QHE The BIPM Watt balance is based on a novel approach to determine both current and induced voltage simultaneously

10. BIPM watt balance counterweight To the balance 3 beams at 120° with associated flexures electrostatic expander 100 g test mass optics for position determination coil magnet 21

11. Calculable Capacitor • Links electrical and mechanical units • Increased accuracy of electrical measurements • Increased accuracy of fundamental constants • The BIPM – NMIA calculable capacitor aims to increase the accuracy by at least a factor of two

12. New Calculable Cross Capacitor The figure shows the new calculable capacitor in partial cross-section. The areas highlighted in green are the main electrodes. The upper and lower guard electrodes are also shown.

13. Model Cross Capacitor Several aspects of the design of a calculable cross capacitor must be determined experimentally. The arrangement shown is for determining the effect of twist from one end to the other of the electrode system, so that the tolerance on this twist may be specified to meet the uncertainty limit for this effect.

14. Measurement of Bar Geometry This is a purpose-built instrument for measuring the geometry of the bars for the new calculable cross capacitors. The bars are required to be true cylinders to within 100 nanometres over 80% of their length. The instrument is capable of better than 10 nanometres.

15. Ensemble of 128 Profiles of the Bar Surface