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Muon Chambers Summary Data

  • Number of MWPC: 1368; of 3-GEM: 24 (Station M1, Region R1)
  • Four gap chambers in Stations M2-M5. Two gap in M1 (R2-R4).
  • Gas gap: 5 mm
  • Wire: Gold-plated Tungsten, 30 mm dia.
  • Wire spacing: 2 mm
  • Wire length: 250 to 310 mm
  • Wire mechanical tension: 60 gf
  • Total number of wires: ~ 3 Million
  • Gas mixture: Ar/CO2/CF4 (40:50:10)
  • Gas gain: G ≈ 105
  • Charge/mip: ≈ 0.8 pC @ HV ≈ 2.7 kV
  • Field on wires: 262 kV/cm, on cathodes 6.2 kV/cm
  • Gain uniformity: ≤ 30%
  • Gap efficiency: ≥ 95% in 20 ns window ( st ≈ 3.9 ns)
  • Rate/channel: max 2 MHz in M1, < 0.6 MHz M2-M5
  • Max. operating voltage: 3 kV

Typical efficiency plateau for two gaps in OR (double-gap)

Typical performances for wire-readout chambers

HV plateau of two double-gaps

Uniformity @ 2550 V 12 fC threshold

Threshold scan @ 2600 V

The relationship ε = f(Gain/Thr) is well verified (Note: gain doubles for +100 V.)

Status of MWPC production



Panel Quality

All panels are individually measured for thickness and warp.
The measurement is performed manually or automatically (for chamber types M1 R3/R4, M2 R3/R4, M3 R4, M4 R3/R4, M5 R2/R4). A quality score from 0 to 10 assigned to each panel: it must be >= 6 for acceptance.

The figure below shows the data sheet for automatic measurements Quality score for 417 panels. 95% are accepted in this plot
Panels are checked again at the production site to spot possible problems (e.g. "bubbles") before gluing
Contactperson: Carlo Forti

MWPC Database

Chamber test database

Contactperson: Alessio Sarti

Test results (dressing and cosmics)

Noise plots (lab and pit)
Chamber production overview for the various production sites

Detector Tests

      Final Source and Cosmic Rays Test before installation (July 2006)

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2003-07 LHCb