Partners and International Organizations
(English)
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NMi Nederlands Meetinstituut (NL), PTB Physikalisch-Technische Bundesanstalt (D), NPL National Physical Laboratory (UK), LCIE Laboratoire Central des Industries Electrique (F), SP Swedish National Testing and Research Institute (S), Chalmers University of Technology, Gothenburg (S)
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Abstract
(English)
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The trend in electrical metrology is to base the primary standards for the electrical units on quantum phenomena. This approach was very successfully put into practice with the Jo-sephson effect for the voltage and with the quantum Hall effect for the resistance. The pro-gress made in the nanotechnologies allows for the fabrication of devices that can accurately manipulate electrons one at a time: this research area is called SET for single electron tun-nelling. One can envision several applications of SET in metrology, like a quantum current standard, a capacitance standard, and extremely sensitive electrometers. The COUNT pro-ject was focused on the last two applications. Within this project, METAS was involved in the realisation of a primary quantum capacitance standard. The idea is to load - electron by elec-tron - a cryogenic capacitor using an electron pump. Then the voltage across the capacitor is measured with a Josephson voltage standard. The capacitance is given by the charge to voltage ratio. The expected uncertainty of such a standard is expected to be a few parts in 107.
METAS contributed to the project as follows:
- The experimental set-up needed for the realisation of the quantum capacitance standard was developed and realised. The set-up comprises a tuneable cryogenic capacitor, a sample holder including a set of two cryo-switches, needed to switch between the differ-ent modes of the experiment, and a custom modified dilution cryostat. The cryo-switches were also made available to other partners in the consortium.
- Single electron pumps fabricated at the Physikalisch-Technische Bundesanstalt (PTB) were integrated into the experimental set-up at METAS and characterised. The I-V char-acteristics of the pumps showed the expected plateaux of constant current , where e is the electron charge and f the pumping frequency. First attempts to quantify the pumping mode accuracy were undertaken.
In conclusion, this project was very successful for our institute, the targets have essentially been achieved. A new quantum capacitance standard was constructed and tested. In a close future, once the last experimental problems will be solved, this set-up will be used to main-tain the unit of capacitance, leading to a strong improvement in the electrical measurement capabilities at METAS.
Publications, presentations:
- F. Overney, B. Jeanneret, M. Furlan, A tunable vacuum-gap cryogenic coaxial capacitor', IEEE Trans. Instrum. Meas., IM- 49, 1326, 2000.
- C. Hof, B. Jeanneret, A. Eichenberger, F. Overney and S. Lothkov, 'First step towards a quantum capacitance standard at METAS', Paper submitted to IEEE Trans. Instrum. Meas., and contribu-tion to the Conference on Precision Electromagnetic Measurements (CPEM), June 2002, Ottawa CA.
- H.E. van den Brom et al., 'Counting electrons one by one - Overview of a joint European research project', contribution to the Conference on Precision Electromagnetic Measurements (CPEM), June 2002, Ottawa CA.
- C. Hof, 'Einzel-Elektronen Metrologie am METAS', seminar at METAS on Nov 13, 2002.
- C. Hof, 'Progress Report on the Quantum Primary Standard of Capacitance at METAS', talk at the final COUNT meeting on Nov 20, 2002. METAS, Bern.
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