Study of GEM-foil defects with optical scanning system

Deformations can build up in the production stages of the GEM-foils. They can affect the performance of the foils and reduce the lifetime of the detector. With an optical scanning system that we have obtained and developed to improve our quality control system for GEM-detector construction we can locate and study different types of defects on the GEM-foils. We studied standard 100 mm × 100 mm GEM-foils by assembling them as a single-GEM detector with XY-readout and irradiated the areas with defects with X-rays from
⁵⁵
Fe source. In this paper we present the results of these measurements.