QUALITY CONTROL AND PURIFICATION HEAT TREATMENT OF NIOBIUM FOR TTF

Eddy current scanning with improved apparatus mainly is applied for quality control of Nb sheets. About 500 sheets for third series of TTF cavities were tested. Some irregularities were detected. Supplementary nondestructive analysis was carried out by Neutron Activation, X-ray Fluorescence and Large Chamber Scanning Electron Microscope. A SQUID Gradiometer system, developed at F.I.T. Messtechnik was applied for diagnostic in Nb sheets and a 9 cell cavity. Its extremely high sensitivity allows to find distributed in-homogeneity. A series of purification heat treatments of Nb from different suppliers was done. The RRR measurement, traction test, hardness measurement and microstructure analysis have shown, that marked change of properties starts at temperatures above 1000iC. The penetration of Ti into Nb during purification heat treatment is discussed. The thickness of the Ti layer is about 10 µm and its penetration depth by boundary diffusion is about 100µm. The routine-RRR control of all cavities was made nondestructively. The collected data show that accelerating voltage tends to increase with RRR. QUALITY CONTROL OF NB SHEETS FOR TTF