Appearance of a diva

[ptb]  On 10 April 2008, a new, isotopically pure silicon sphere will arrive at the Physikalisch Technische Bundesanstalt (PTB) from the final station of its production process in Australia. Thus, the Avogadro Project for the new definition of the kilogram - coordinated by the PTB - is entering its final stage: The scientists expect the 28Si sphere to provide the crucial breakthrough for the determination of the Avogadro constant, i.e. the number of particles in a mole amount of substance. When using the previous spheres made of a silicon-isotope mix, it was not possible to achieve the required accuracy. With its unique purity, its uniform structure, the extremely smooth surface, and not least its price, the new sphere is identical to a diva and has only one single equivalent worldwide: a twin which travels to Japan for comparison measurements. We dedicate to the production of the sphere its own fascinating story (only German).

PTB Contact: (untill 09.04.2008 only via email)
Dr. Peter Becker, Department 4.3 Quantum Optics and Unit of Length,
phone (0531) 592 - 4300, E-Mail: peter.becker@ptb.de

Dr. Arnold Nicolaus, Working Group 5.41 Interferometry on Spheres,
phone (0531) 592 - 5410, E-Mail: arnord.nicolaus@ptb.de