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# Comments on 2mm MWPC pitch

Comments on 2mm MWPC pitch. W. Riegler, December 2002. Impact on specifications, guard wire and some other parameters. r a : anode wire radius V a : anode wire voltage : ion mobility q: charge per hit R: rate/cm 2 r c =(s/2 ) Exp(h/s) equivalent cathode radius

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## Comments on 2mm MWPC pitch

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1. Comments on 2mmMWPC pitch W. Riegler, December 2002 Impact on specifications, guard wire and some other parameters

2. ra: anode wire radius Va: anode wire voltage : ion mobility q: charge per hit R: rate/cm2 rc=(s/2) Exp(h/s) equivalent cathode radius Ea=Va/(ra ln(rc/ra)) anode wire surface field Ec= Va/(s ln(rc/ra)) cathode surface field t0= ra2 ln(rc/ra)/(2Va) signal tail V=Rsh2q ln(rc/ra)/(4Va0) voltage drop due to space . charge effect Details: LHCb-muon-2000-060

3. Parameters and Specifications for h=2.5mm,ra=15m, s=2(1.5)mm • Ea (Gain105): 262.39kV/cm • Va: 2750V (3150) V 0.87 • Ec: 6.18 (8.24) kV/cm 0.75 • rc: 16.15 (44.86) mm • ln(rc/ra): 6.982 (8.00) 0.87 • t0: 1.50 (1.50) ns 1 • V Voltage drop due to space charge: factor 1.33 larger, negligible • Specs: • When does the wire surface field differ by 1% i.e. the gas gain differ by 20% ? • Gap: 88(75) m 0.85 • single wire X: 130(90) m 0.69 • single wire Y: 310(250) m 0.81 • wire plane Y: 330(300) m 0.91 • No Guard Wire: 301(325), 269(277), 263(266), 262(263), 262.3(262) kV/cm • 200m Guard Wire: 70.4(76.5), 251(249), 260(260), 262(262), …. kV/cm

4. Conclusions With respect to specifications, rate capability, signal tail and guard wire issues the 2mm pitch doesn’t have any drawbacks compared to the 1.5mm pitch.

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