A novel idea for an ultra-light cylindrical GEM based vertex detector

We present a novel idea for an ultra-light cylindrical triple-GEM detector for vertexing purposes. Exploiting the combination of the straw tube and vacuum bag techniques we successfully built the five perfect cylindrical structures needed to realize one vertex detector layer. All cylindrical components, the cathode, the three GEM foils and the anode readout are made of thin kapton foils. The final result is a very light detector (0.2% of X 0 per layer) practically free of dead zones inside the active area. We report on the experience of winding the kapton foil up in order to realize the cylindrical structure, which represents the basic element of such a vertex detector.