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A Silicon Sphere Transfer Ceremony & Workshop

To measure the mass (kilogram) accurately traceable to the Planck constant h, NML is adopting the technique of X-ray Crystal Density (XRCD) method.  We work with PTB, Germany to set up a mass measurement system and a combined XRF XPS system for mass determination and dissemination of the 28Si-enriched sphere.  The XRF and XPS measurement data is used to determine the mass of the surface layer of the 28Si-sphere.  PTB provides consultants and technical supports to NML when designing, building and launching the combined XRF XPS system.

On 24th October 2018, NML hosted a Silicon Sphere Transfer Ceremony & Workshop on Revision of the SI to unveil the highly enriched 28Si-sphere of the nominal mass of 1 kg as the mass standard.  Prof. Joachim Ullrich, President of PTB, attended the ceremony and Dr. Frank Haertig, Head of Mechanics and Acoustics Division of PTB, delivered a talk on “Introduction of XRCD kg realization and new progress on redefinition" to the public.

Dr. Tzeng-Yow Lin, General Director of NML, stated that with the new SI, the 1 kg standard based on the platinum-iridium alloy cylinder, the international prototype kilogram (IPK), would be relegated to a secondary standard.  NML’s acquisition of the 28Si-sphere would maintain the highest measurement standards and ensure that our kilogram standard will be directly traceable to the Planck constant h, realized and maintained by our own.  Dr. Lin continued, the implementation of the revised SI would provide quality assurance and traceability and therefore underpin the trade and hi-tech research that require world-class measurement standards.  

President of PTB, Prof. Ullrich noted that PTB is pleased to embark on an exciting journey together with NML in disseminating the mass standard in the revised SI.  According to Dr. Ullrich’s view, NML will have the in-house capability to not only contribute its kilogram realization result to the international key comparison database, but also provide mass calibration service across a large range of the mass scale.  He believes that NML will play an important role in providing the critical traceability to the revised SI in the long-term and become a lighthouse in the Asian region for disseminating the mass standard.

  • Last Updated:2020/08/07
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