Nondestructive testing of niobium sheets for superconducting resonators

• Published in: IEEE transactions on applied superconductivity 2003-06, Vol.13 (2), p.239-244
• Main Authors: Muck, M., Welzel, C., Farr, A., Schloz, F., Singer, W.
• Format: Article
• Language: English
• Subjects: Applied sciences; Circuit properties; Electric, optical and optoelectronic circuits; Electrical engineering. Electrical power engineering; Electromagnets; Electronics; Exact sciences and technology; Fabrication; Linear particle accelerator; Magnetic materials; Materials testing; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Niobium; Nondestructive testing; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sheet materials; SQUIDs; Superconducting devices; Superconducting materials; System testing; Testing, measurement, noise and reliability; Various equipment and components
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2003.813694

We have developed a LTS SQUID system for eddy-current testing of niobium sheets used to fabricate superconducting resonators for particle accelerators. Since the fabrication of superconducting resonators from planar niobium sheets is very costly, a measurement procedure is required which can test the niobium sheets before the resonator is made. Our system can detect relevant surface damage or inclusions of foreign material having a volume of as small as 10/sup -12/ m/sup 3/ in a test sample made from high-purity niobium. Due to the relatively high frequency of the eddy currents of up to 100 kHz, the system-although employing a magnetometer-can be operated in an unshielded environment. The SQUID readout uses 4 MHz AC-flux modulation; a peak-to-peak dynamic range of 15 fluxquanta is obtained at 100 kHz.