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Title Testing of Nb Sheets on a SQUID NDE System with Large Scale x/y Table for Use in Industrial Enviroment
Type Poster materials / surface effects
Abstract The reachable field strength in superconducting resonators used in particle accelerators is limited by surface defects or inclusions of unwanted elements. Inclusions of some 100 mum in diameter can significantly reduce the reachable field strength. Since the manufacturing of Nb resonators is very expensive, the Nb sheets must be checked prior to production of the resonator tubes on such defects. We have constructed a system for non-destructive inspection of niobium sheets, based on eddy current measurements. To receive the neccessary detection sensitivity, a SQUID sensor for measuring the local eddy current density is used. The system works in a non-shielded enviroment. Within test sheets supplied from DESY tantalum inclusions with diameters of approximately 100 mum could be confidentially detected. With a sheet size of about 300x300mm**2 and a line width of 1mm a scan of one sheet lasts about 15 min, because of the SQUIDs low noise the sheets can be scanned with up to 100mm/s scanning speed. Because of the high sensitivity of the SQUID detector it is not only possible to detect very small defects within sheets but also to gather a detailed image of the found defects, so it is easier to categorize the results than with an inspection of lower resolution and sensitivity. The software written for the project allows it to group different measurements on the same sample and catalogizes the measured results. During the project, different measurement equipments were build up, some with stationary SQUID systems, other with stationary sample holder. In all cases it was possible to operate the SQUID, even if a setup with stationary SQUID are often easer to work with, since gradients in the local field in such a case are no problem for the dynamic range of the magnetic field sensor.

List of authors...

Principle author first.

Last (Family) Name First Name (Initials only) Affiliation or Organization (abbreviations if possible)
Farr A. wsk Mess- und Datentechnik GmbH, Hanau
Schoelz F. wsk Mess- und Datentechnik GmbH, Hanau
Reuss J. wsk Mess- und Datentechnik GmbH, Hanau
Mueck M. Inst. of Applied Physics University of Giessen
Welzel C. Inst. of Applied Physics University of Giessen



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