GEM DETECTORS Gas Electron Multiplier BatEl Pinchasik Technion

GEM DETECTORS Gas Electron Multiplier Bat-El Pinchasik, Technion Israel

GEM detectors main element Terminals GEM foil 10 cm of s n io Mill les! ho Kapton (polyimide) copper-clad on both sides

CO 2+ Argon E D O H T GEM CA DRIFT REGION INDUCTION REGION E D O AN Tracking, segmentation Triggering Etc. .

Field lines Electrons follow the field lines Drift field GEM foil Induction field 500 volts 50μm In the holes: high density of field lines Electrons gain energy!

Simulation: CATHODE Ions Electron-Ion pair Drift field Top GEM Bottom Electrons are shared between bottom GEM and anode Induction field Gain of the detector ANODE

Advantages Detector Area Cost Rate covered (per area) capability by a detector Aging process GEM detector $$ Low aging Wire chamber $ Gain loss and discharges increase Silicon detectors Noise and leakage current increase

72µm 40µm • First invented in 1998 • Double conical geometry • Used already in several experiments Re ce nt d • Easy to produce • larger detectors • low cost per area copper 98. 9µm kapton copper 42. 5µm ev el o pm en t!

Glance from above Standard GEM Internal & External diameter 140 µm Conical GEM- Top Conical GEM-Bottom Larger diameter 140 µm smaller diameter

See the difference Large conical GEM foil 60 cm 10 X 10 cm

CO 2+ Argon E D O H T CA Drift field Induction field Voltage over the GEM AN E D O Anode current

Drift field scan GEM voltage: 500 volts E induction: 3 (kv/cm) I anode (normalized) conycal conical 1 standard 0. 8 plateau 0. 6 Recombination Electrons end up in Top GEM 0. 4 0. 2 0 E drift (Volts/cm) 0 1000 2000 3000 4000 5000

Gain vs. GEM voltage Integration over distance Gain Townsend coefficient α Field & gas properties Gain of the detector Log scale standard conical 500 E induction: 3 kv/cm E drift: 2 kv/cm 50 5 300 350 400 450 500 550 600 Gem voltage (volt) 650

Induction scan Electrons distribution I anode (normalized) 1. 1 conical standard 0. 9 0. 7 More electrons get to the anode 0. 5 Higher signal Increasing induction field 0. 3 0. 1 0 1000 2000 3000 4000 5000 6000 E induction 7000 (volt/cm)

Conclusions Results • Conical GEM has similar performance as standard GEM • Low cost • Larger area Advantages • Easy to fabricate • Conical GEM is an attractive candidate to future LHC upgrades Conclusion

Current applications LHC B TOTEM COMPASS LHCB muon And the future?