Progress on Nb3Sn and V3Si at LNL

In the framework of the research for a valid alternative to Nb for RF applications, Nb3Sn and V3Si have been investigated at LNL. The chosen technique to obtain Nb3Sn is based on the molten Tin diffusion method and it has been progressively modified to improve the samples superconducting properties (Tc and ?Tc) and to eliminate Sn traces on the Nb3Sn surface. Our "Hybrid process" seems to be the most promising (Tc = 16,8 K and ?Tc = 0,16 K, no residual Sn traces on the sample surface, no Sn rich phases). The present point is to test the obtained material RF properties: the best recipe used for samples has been applied to coat a 6 GHz Nb cavity. At the same time we are going to study different techniques to achieve Nb3Sn good superconducting cavities. One of them is the so called mechanical plating. Secondly we are going to study the multilayer technique: the first attempt gave a superconducting deposition with Tc = 17,9 K and ?Tc =.0,02 (four contacts measurement). The V3Si intermetallic compound has been obtained using the thermal diffusion of Silicon into Vanadium: bulk V is heat treated in a SiH4 atmosphere for several hours and then annealed in vacuum. The samples superconducting properties are encouraging (Tc 15,5 K and ?Tc 0,2 K). To check the material RF performances we prepared a V3Si 6 GHz cavity (sylanized for 4h at 850°C with p(SiH4) = 5x10-3 mbar): it has been measured several times after a heating treatment in vacuum progressively longer (6h, 12h, 36h, 84h at 850°C). At the moment, we are trying to use plasma during the silanization process to avoid the hydrogen presence into the growing films. The first V3Si coating grown has Tc = 15,7 K and ?Tc = 0,22 K: this result is already comparable to what we had with the "traditional" technique.