Methodical study of BMN GEM detectors A Maksymchuk

Methodical study of BM@N GEM detectors A. Maksymchuk, E. Kulish on behalf of BM@N Collaboration BM@N experiment is aimed to study core-core collisions in extreme conditions. High intensity of interactions and large multiplicity of charged particles in each event cause special requirements to detectors: high spatial and time resolution, radiation loadings up to 106/sm 2. As soon as triple GEM posses all above-mentioned characteristics, they were chosen as the main track detector. Integration of GEM detectors into the experimental setup structure and study of their characteristics is a task of great importance. JINR GEM 1632 x 450 chamber HV 00 strips DAQ system +150 strips Right R/O board Left R/O board 450 GEM detector configuration 150 779. 9 (inner zone) R 40 420. 1 400 1632 3 mm T 1 2. 5 mm T 2 2 mm GEM 3 0. 16 0. 8 Drift gap GEM 2 GEM 1 Anode 0. 6 8 Induction gap 1. 5 mm GEM optimization for Ar(70)/CO 2(30) and Ar(90)/Isobutane(10) gas mixtures This optimization was made to choose correct parameters of electric field values in GEM gas gaps and, as a consequence, HV divider parameters Working point Working range HV divider working point Drift gap field optimization Transfer 1 gap field optimization Induction gap field optimization Working range HV divider working point Transfer 2 gap field optimization Transfer 1 gap field optimization HV divider working point Transfer 2 gap field optimization GEM gas gain measurements Fe 55 cathode Efficiency Experimental scheme Gem 1 Gem 2 Gem 3 anode Amplitude distribution, Ar(70)/CO 2(30), Fe 55 discr. Trigger Efficiency plateau is reached when signal amplitude/threshold = 17 ADC GEM gas gain for Ar(70)/CO 2(30) and Ar(90)/Isobutane(10) gas mixtures GEM assembly at CERN Workshop GEM upgrade in JINR clean room Conclusion: Seven GEM chambers main characteristics were studied. All these modules, front-end and readout electronics were successfully integrated into BM@N experimental setup structure. Two GEM 1632 cm × 450 cm chambers are the biggest GEM detectors in the world for today.