You were presented with a Life Achievement Award. What does this Award represent for you?
The International Cryogenic Materials Commission (ICMC) brings together more than one thousand researchers working on superconductors and cryogenic materials, who meet every year, alternatively in the USA or in other parts of the world, e.g. Europe or Asia. The prize is awarded every two years. The last two recipients were Prof. David Larbalestier, USA (2008) and Prof. Kyoji Tachikawa, Japan (2006), both well known within the scientific community.
It was awarded to you for the quality of your research, innovation and as acknowledgement of your reputation worldwide. Can you tell us more?
The study of the physical properties of superconducting materials and their metallurgy for improving their performance in view of industrial applications has been the main subject of my career. At the end of the 70s, I contributed to the study of several high temperature phase diagrams, e.g. Nb-Al, Nb-Ga et Nb-Ge and Nb-Sn, the latest one being the basis of superconducting wires in actual nuclear magnetic resonance systems, at magnetic fields up to 23.5 T. Concerning the innovations, I would like to mention the thermal analysis for levitating materials (avoiding the reaction with the crucible at T > 2’000°C), or the use of HIP (high isostatic pressure) for the preparation of homogeneous materials with components with high vapour pressure, such as Nb3Sn or PbMo6S8 (Chevrel phases). A constant effort in my work was concentrated on the enhancement of the critical current density in wires or tapes based on Chevrel phases, Bi-2223 and Nb3Sn. For my work in the area of Nb3Sn, I received the IEEE Award (Institute of Electric and Electronic Engineering) in 2005. The latest innovation, performed within the Group of Applied Physics at the University of Geneva is a new device allowing for the first time the densification of industrial lengths of wires based on MgB2, at pressures as high as ≤1.5 GPa.
It has to be noted that MgB2 can only be prepared by powder metallurgy: since it is expected that any newly discovered superconducting compound will have to be treated by powder metallurgy, the present densification technique is expected to be important for the future.
You developed the group of applied superconductivity at the University of Geneva. How did it start and where is the group today?
In 1990, I set up a new group of applied superconductivity within the Department of Condensed Matter Physics (DPMC) and the Group of Applied Physics (GAP). Thanks to the funding received from the National Science Foundation (NSF), the Commission for Technology and Innovation (CTI), from various industrial collaborations and finally by MANEP, it was possible to build up a laboratory which became in the meantime the largest one in Europe for the development of superconducting wires.
Have you been able to develop contacts with industry?
My work in Geneva has always been performed in close collaboration with industry. Firstly with Rolex, for which my group developed a new type of paramagnetic spiral based on NbZr, being particularly insensitive to changes in temperature. These spirals contribute to an even higher precision and are today part of the production process. For Charmilles, we developed new wires for speeding up the process of cutting by means of EDM machines. For 15 years, we have been collaborating very closely with the manufacturer Bruker BioSpin (Fällanden, ZH), the world leader in high field nuclear magnetic resonance (NMR) systems. We have contributed to the improvement of critical current densities of superconducting Nb3Sn wires used in these systems.
What are your current projects?
At the University of Geneva, I will continue to collaborate with my successor, Dr. Carmine Senatore, to further develop our new method for densifying superconducting wires, based on MgB2, but also on other materials (2 patents submitted). This new type of deformation will lead to markedly lower production costs.
Where do you see superconductivity 100 years from now?
There is no doubt that the search for new superconductors with even higher transition temperatures will continue in view of new applications in the field of energy and electronics. Given the unexpectedly large number of new superconductors discovered in the last 20 years with transition temperatures well above 40K, it expected that new materials will be found with transition temperatures coming always closer to room temperature, allowing developments considered impossible today.