The generation of electromagnetic fields in the radiofrequency (RF) cavities is the important long-studied issue in the accelerator physics and technology. The effective acceleration of electrons emitted from a cathode requires high electrical field gradients. This determines an amount of energy dissipated upon RF cavity walls. To avoid large energy losses, and particularly over-heating, which might lead to a large temperature rise, a film with an uniform and defects-free surface and characteristics, corresponding to the bulk superconductor, eg pure niobium, must be obtained.In technical research activities concerning the construction of large linear accelerators, particular attention was paid to the possibility of depositing thin super-conducting layers. Originally, the magnetron sputtering has been proposed as a well established deposition technique. Unfortunately, some unwanted features of the layers deposited with this technique, appeared to be impossible to overcome, eg the Q0 factor degradation, insufficient film quality and purity. This paper reports on the development achieved in the ultra high vacuum cathodic-arc deposition technique [1-2]. The so-called linear-and planar-arc devices are described together with appropriate micro-droplets filters. The efficiency of the filtered deposition has been analyzed by performing model calculations and experiments. The structure and superconducting properties of the deposited Nb-films have been studied.
1 Jan 2007
Volume: 6 Pages: 23-25
Synchrotron Radiation in Natural Science