CSC Test Beam Data Analysis Alexander Khodinov and Valeri Tcherniatine

Outline  Cathode Strip Chambers in ALTAS  CSC Principle of Operation  CSC Beam Test Layout at X5 (stand alone experiment, CERN)  CSC position resolution and inefficiency

ATLAS Cathode Strip Chambers CSC Electronics:  24,576 Precision Channels (X)  6,144 Transverse Channels (Y)  256 – 96 channel ASM1 (X) Boards  64 – 96 channel ASM1 (Y) Boards  160 – 192 channel ASM2 Boards 2x16 chambers

ATLAS Muon Spectrometer  =2.7

Principle of Operation  Determine muon position by interpolating the charge on 3 to 5 adjacent strips using ratio algorithm:  Precision (x-) strip pitch ~ 5mm  Measure Q 1, Q 2, Q 3 … with signal/noise=150/1  to get  x ~  m. Human hire diameter ~100  m.  Second set of y-strips measure transverse coordinate to ~ 1 cm.  Position accuracy unaffected by gas gain or drift time variations. S = d = 2.50 mm W = mm 0.8Ar+0.2CO 2

Beam test setup layout at X5 high radiation facility P  =120 GeV/C Lead absorbers of different thicknesses were used to vary the background flux intensity. ←

On-line event viewer by M. Schernau

Signal shape and fitting The bipolar function was used to fit the signal: z = (t-t 0 )/  n=12 - the parameter of amplifier integration, t 0 - signal start position  - signal width signal has been digitized at 20(40)MHz Clock time distance between time slices 50(25)ns pedestal extracted

Beam profile distributions

Landau distribution Charge induced in ADC counts: Q = Q max +Q right +Q left

Position resolution and inefficiency Inefficiency: Position resolution in 2 nd and 3 rd gaps defined as (two chambers involved), where  - width of the Gaussian fit of    over ±0.3mm

CSC one layer resolution and inefficiency as a function of background radiation rate Run 99 Run04

Summary stand alone test beam at X5  During the beam test the chamber + electronics at 20 MHz clock showed the expected performance.  One layer inefficiency is found to be 5% without radiation and 24% at the maximal expected LHC background rate (safety factor of 5) 4.2 kHz/cm 2  No calibration used. The results can be considered as conservative estimates (not worse then) for efficiency and resolution.