Upgrade of a UHV Furnace for 1700 C Heat Treatment and Processing of Niobium Samples

In 2005 a high temperature vacuum furnace was put into operation at the Institute for Nuclear Physics at the Technische Universität Darmstadt. It has been designed for firing pure Niobium at temperatures of up to 1870 °C. Until now several Nb cavities have been heat treated at 850 °C with a proven record of success [1]. The current focus of research in improving the superconductive characteristics of accelerator cavities is on new materials such as Nb3Sn or NbN or on the doping of Nb surfaces with nitrogen, so called N2-Doping [2]. The surface preparations generally take place at temperatures of not more than 1000 °C. To study phenomena that occur at higher temperatures, like the formation of δ-phase NbN at 1300 to 1700 °C, we refurbished the UHV furnace and equipped it with state-of-the-art infrastructure. The vacuum system was updated as well as a new power interlock was applied due to a failure of the previous system. We designed a new annealing pot and planned its construction; the dimensioning of an appropriate sample holder is