The KLOE-2 cylindrical GEM inner tracker: Detector operation, calibration and performance

KLOE-2 at the ee DAφNE φ-factory is the main experiment of the INFN Frascati National Laboratories (LNF) and is the first high-energy experiment using the GEM technology with a cylindrical geometry, a novel idea that was developed at LNF exploiting the kapton properties to build a light and compact tracking system. Four concentric cylindrical triple-GEM detectors, for a total material budget below 2% of the radiation length X, are inserted around the interaction region and before the inner wall of the pre-existing KLOE Drift Chamber, at distances from 130 mm to 205 mm. For this project, state-of-the-art solutions have been expressly developed or tuned: single-mask GEM etching, multi-layer XV patterned readout circuit, PEEK spacer grid, GASTONE front-end board, a custom 64-channel ASIC with digital output, and the Global Interface Board for data collection, with a configurable FPGA architecture and Gigabit Ethernet. The dedicated XV strips patterned readout allows space coordinates to be reconstructed. Alignment and calibration of a cylindrical GEM detector was never done before and represents one of the challenging activities of the experiment. During 2015 both KLOE-2 and DAPHNE successfully demonstrated the feasibility of a long term acquisition program with the first data taking campaign, started in November 2014 and ended in July 2015 with 1 fb integrated luminosity. The second new data taking campaign started in September 2015 and KLOE-2 is presently taking data. The Inner Tracker detector operation, calibration and performance will be presented. Preliminary results obtained with cosmic-ray muons and Bhabha scattering events are within expectations for the Inner Tracker resolution.