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ECFA meeting muon theme3. Novel Gaseous Detectors and Technology R&D. M. Abbrescia (CMS), P . Iengo (ATLAS), D. Pinci ( LHCb ). General considerations.

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novel gaseous detectors and technology r d

ECFA meeting muon theme3

NovelGaseousDetectors and TechnologyR&D

M. Abbrescia (CMS), P. Iengo (ATLAS), D. Pinci (LHCb)

general considerations
  • All detectors foreseen for post-LS3 with the aim of restore redundancy or increase coverage should stand a rate capability higher then the present
    • Because installed in high-ηregions
    • From 1 kHz/cm2 5-10 kHz/cm2

RPC rate capability

  • In addition we could be willing to improve also:
    • Time resolution – from o(1 ns)  o(100 ps)
    • Spatial resolution – from o(1 cm)  o(1-0.1 mm)
  • Given requirement on rate capability, choice of the technology will be driven by the physics case:
    • plus robustness, cost, easiness of construction, etc.
  • For instance, o(100 ps) would push us toward RPC multigaps solutions
the technology gas electron multipliers
The technology: Gas Electron Multipliers

Developedby F. Sauli in 1997

Eachfoil (perforatedwithholes) is a 50 µm kaptonwithcoppercoatedsides (5 µm )

Typicalholedimensions: Diameter 70 µm, pitch 140 µm

  • Electron multiplicationtakesplacewhentraversing the holes in the kaptonfoils
  • Manyfoils can be put in cascadetoachieve O(104) multiplicationfactors
  • Maincharacteristics:
  • Excellent rate capability: up to 105/cm2
  • Gas mixture: Ar/CO2/CF4 – notflammable
  • Largeareas ~1 m x 2m with industrial processes (costeffective)
  • Long termoperation in COMPASS, TOTEM and LHCb
detector performance
Detector performance
  • Verygoodtimeresolution
    • Dependingcritically on the gas mixture
    • Long R&D on gas (and otherissues)
  • Excellentspatialresolution
  • Full efficiency at 104overallgain

A new VFAT3 baFEelectronicsbeingdevopedtofully profit fromallthesecaracteristics

σt=4 ns

Gain = 104

σs = 150 µm

the gem project ge1 1
The GEM project: GE1/1

After LHC LS1 the |η|< 1.6 endcapregionwillbecoveredwith 4 layersofCSCs and RPCs; the |η|>1.6 region (mostcritical) willhaveCSCsonly!

  • Restore redundancy in muon system for robust tracking and triggering
  • Improve L1 and HLT muon momentum resolution to reduce or maintain global muon trigger rate
  • Ensure ~ 100% trigger efficiency in high PU environment
and beyond r d on glass rpc
And beyond…R&D on glass RPC
  • New “low” resisitivity (1010Ωcm) glassusedfor high rate RPC
  • RPC rate capabilitydependslinearly on electroderesistivity
  • Smootherelectrodesurfaces reduces the intrinsicnoise
  • Improvedelectronicscharacterizedbylowerthresholds and higheramplification
  • Single and multi-gapconfigurations under study

Readout pads

(1cm x 1cm)

Mylar layer (50μ)

PCB interconnect

Readout ASIC

(Hardroc2, 1.6mm)

PCB (1.2mm)+ASICs(1.7 mm)

PCB support (polycarbonate)

Gas gap(1.2mm)

Cathode glass (1.1mm)

+ resistivecoating

Mylar (175μ)

Ceramic ball spacer

Glass fiber frame (≈1.2mm)

  • Excellent performance at localizedbeamtests
    • Rate capability ~ 30 kHz/cm2 (multi-gap)
    • Timeresolution 20-30 ps
needs for new technologies
Needs for new technologies
  • Operationat the HL-LHC willbeverydemanding for the muon detectors
  • Alreadyafter LS2 the present muon spectrometerneeds an upgrade in the innerwheels
    • Degradation of the MDT performance in terms of efficiency and resolution
    • Level1 muon trigger dominated by fakes in the endcap
  • A number of R&D programmes on high-rategaseous detectors have been carried out
    • Small-stripThin Gap Chambers (sTGC)
    • Micromegas (MM)
    • Small Monitored Drift Tube (sMDT)
    • Multi-gapResistive Plate Chambers (mRPC)

Selected for the ATLAS New Small Wheel

  • NSW detector requirements
    • Spatial resolution O(100um) single plane
    • Time resolution <10ns for BC identification
    • Angularresolution 1mrad for trigger decision (vertex pointing)
    • Rate capability > 14kHz/cm2
    • High efficiency (>98%)
    • Goodageing performance
    • Double trackresolution (d ~few mm)
  • Technologyimprovements:
    • In large detectors, resistive cathode reduces the operating voltage.
    • Go from present TGC resistivity (1 MΩ/cm²) to 100 KΩ/cm² and reduce gap between strips to cathode (transparency prop. to RC).
  • Good performance athigh rate

Detector efficiency vs impact angle

Position resolution vs impact angle

  • ATLAS NSW: first large system based on MM
  • Technologybreakthroug:
    • Resistivestrips for sparkimmunities
    • Construction and operationathigh rate of large-area (few m2) detectors possible
    • Bulk technique replaced by ‘floatingmesh’ configuration
    • Good spatial resolutionalso for inclinedtracksthanks to uTPCoperation mode

Spark protection system

Test with neutron flux 106 Hz/cm2

Non-resistive MM

Resistive MM


Position resolution vs impact angle

ti, xi

Yhalf(2.5 mm)



  • 15 mm diameter tubes
    • Max drift time 185 ns
    • Occupancyscaleswith max drift time and tube cross section: 6.5% at 3x1034 cm-2s-1
    • Gain loss due to space charge effectscales ~r2
    • Good spatial resolutionindipendent on track incidence angle
    • Standard Al tubes, construction procedureswellunder control to equip large area

Efficiency vs counting rate

Spaceresolution vs distance from the wire






r d needed