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Gas Electron Multiplier

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Presentation on theme: "Gas Electron Multiplier"— Presentation transcript:

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

2 GEM detectors main element
GEM foil Terminals 10 cm Kapton (polyimide) copper-clad on both sides Millions of holes!

3 GAS ATMOSPHERE CO2+ Argon GEM CATHODE ANODE DRIFT REGION
INDUCTION REGION segmentation Tracking, Triggering Etc..

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

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

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

7 Standard GEM Conical GEM First invented in 1998
Double conical geometry Used already in several experiments Conical GEM 42.5µm 98.9µm copper kapton Recent development! Easy to produce larger detectors low cost per area

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

9 Does a conical GEM have the same characteristics?
See the difference Large conical GEM foil 60 cm 10 X 10 cm Does a conical GEM have the same characteristics?

10 GAS ATMOSPHERE CO2+ Argon CATHODE Voltage over the GEM ANODE
Drift field ANODE Induction field Anode current

11 Electrons end up in Top GEM
Drift field scan GEM voltage: 500 volts E induction: 3 (kv/cm) plateau Recombination Electrons end up in Top GEM

12 Integration over distance
Gain vs. GEM voltage Gain Integration over distance Townsend coefficient Field & gas properties α Gain of the detector Log scale E induction: 3kv/cm E drift: 2 kv/cm Gem voltage (volt)

13 Electrons distribution
Induction scan Electrons distribution I anode (normalized) Increasing induction field More electrons get to the anode Higher signal E induction (volt/cm)

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

15 Current applications COMPASS TOTEM LHCB LHCB muon And the future?


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