Titanium nitride insulation for the deflector of superconducting cyclotrons

At the Istituto Nazionale di Fisica Nucleare-Laboratorio Nazionale del Sud of Catania (Italy) during the last years a research program has been carried out to improve the performance of the superconducting cyclotron electrostatic deflectors. In this kind of accelerator beam extraction is realized by means of two electrostatic deflectors generating a 140 kV/cm maximum electric field in a small gap (6 to 8 mm). These devices have to work in presence of a high magnetic field (/spl les/5 T), strongly affecting their performance from the electrostatic point of view. This is mainly the focusing of the electrons emitted by the cathode for field effect. The physical characteristics of the cathode surface influence the electrostatic behavior especially in terms of work function and resistivity. Moreover, the mechanical properties of the surface have to be studied in order to evaluate the effects of high power beam dissipation on the cathode during the extraction process in the accelerator, also influencing the electrostatic performance. Looking to these constraints, a detailed study of the TiN (titanium nitride) features for this application has been carried out. Considering the electrical and mechanical properties, TiN seems to be a material suitable for this application. Electrostatic tests carried out in a deflector simulator confirm that TiN should represent an attractive solution. The results obtained with a surface characterization based on different physical analysis methods are presented.