Speaker
Michele Caponero
(Istituto Nazionale Fisica Nucleare Frascati (IT))
Description
Fibre Gragg Grating (FBG) sensors were used to develop a distributed structural sensing system devoted to assess and validate the mounting procedure of the Gas Electron Multiplier (GEM) films of the GE1/1 chambers of the Compact Muon Solenoid (CMS) experiment at LHC. The large (1m by 0.5m) GEM films must be mechanically stretched to optimal mechanical tension to assure flatness. FBG technology was adopted in consideration of the stringent requirements of lightness asked for the sensing system to be deployed on thin GEM foils to be monitored, and to several advantages compared to non-optical sensors, such as radiation hardness, long term reliability, precision, accuracy. FBGs are optical strain gauges embedded in the core of an optical fibre. Quasi-punctual sensing occurs at the FBG position and the signal is delivered to the acquisition unit through the fibre length. Multiple FBGs can be placed in-series along one optical fibre. For this work we deployed a custom array of FBGs placed in-series along an optical fibre and installed on the surface of the GEM foil. A full size GE1/1 chamber was instrumented, installing one array of FBGs on each of its three GEM foils. Experimental measurements were done to correlate parameters such as flatness of GEM foil, distributed strain of GEM foils, tensioning applied on GEM foil border by mounting brackets. Preliminary results will be presented and discussed.
Author
Michele Caponero
(Istituto Nazionale Fisica Nucleare Frascati (IT))
