A novel idea for an ultra-light cylindrical GEM based vertex detector
Abstract
An ultra-light cylindrical triple-GEM detector for vertex purposes is being developed. The cathode, the three GEMs and the anode are five concentric cylinders, obtained winding parallelogram-shaped foils, with a resulting helicoidal junction overlap (<3 mm wide). The result is a wholly cylindrical GEM, almost free of dead-zones and without support frames inside the active area, fruitfully usable as a vertex detector. The detetector is also extremely light: considering that the material used is mainly kapton, and the possibility to reduce the copper layer thickness to 2μm, a single tracking layer can have a material budget as low as 0.2% of X0. The readout of the detector is performed with large stereo angle U-V strip layers: one directly realized on the anode electrode, and the other onto the bottom side of the third GEM foil. Considering a large stereo angle of about 40 degrees and a strip pitch of 400μm, the spatial resolutions achievable are σrφ∼σz∼200 μm. In order to avoid ambiguity in the position reconstruction the right strips crossing angle, corresponding to the winding angle, must be tgθ = L/πR (where L is the lenght of the vertex detector and R its radius). The mechanical assembly of one single layer is described and preliminary results obtained with an Ar/CO2 = 70/30 gas mixture are discussed.
- Publication:
-
APS Division of Nuclear Physics Meeting Abstracts
- Pub Date:
- October 2006
- Bibcode:
- 2006APS..DNP.BD004D