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 Q1, Q2, Q3… with signal/noise=150/1 to get x ~ 60-80 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 = 5.308 mm

0.8Ar+0.2CO2

)(max

max

max right

left

QQ

QQfxx

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-t0)/n=12 - the parameter of amplifier integration,t0 - signal start position- signal width

signal has been digitized at 20(40)MHz Clocktime distance between time slices 50(25)ns

pedestal extracted

Beam profile distributions

Landau distribution

Charge induced in ADC counts:Q = Qmax+Qright+Qleft

Position resolution and inefficiency

][308.5 31

3223

41

mmxx

xx

TOTEV

EV

N

mmN )5.0(11 23

21

Inefficiency:

Position resolution in 2nd and 3rd gaps defined as (two chambers involved), where

- width of the Gaussian fit of over ±0.3mm

rdnd 32

2

1

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/cm2

No calibration used. The results can be considered as conservative estimates (not worse then) for efficiency and resolution.