ITEP Beam Chambers P.Gorbunov (U. of Toronto and ITEP, Moscow)

CBT EC2 Planning meeting CERN 112-Nov-2003 P.Gorbunov

ITEP Beam ChambersP.Gorbunov (U. of Toronto and ITEP, Moscow)

Features: • X-Y MWPCs with cathode DL r/o• working area: 120×120 mm2

• gas: Ar-CO2 (80:20); HV: 2.25 kV• detection efficiency ≈ 100%• accuracy: 120 – 200 μ• readout channels: 6 (analog) • availability: 4 (currently in H6) • built in 2002

• Successfully used in Fcal TB2003 and OPERA’2002 (nuclear emulsion)


Technical features Two identical chambers (X- and Y-) in common housing Anode planes: 25 wires, 20 μ, 6 mm spacing Cathode planes: 31 wires, 100 μ, 4 mm spacing, ┴ to anodes Anode-to-anode: 26 mm Calibration pulser signals can be injected to cathode wires 7,16 or 25

(3000 pulser events at start of each run) Lumped delay line with 10 ns cells More on the design and comparison with MC simulation:

cern.ch/atlas-fcaltb/Memos/Hardware/BPB/BPC_Note1-2003.pdf cern.ch/atlas-fcaltb/Memos/Hardware/BPC/ITEP_BPC_design_Rus.doc

(in Russian) Real rate limit: ~30 kHz No multitrack measurement (rejection only)


Readout electronics

CC.

W#16

L

W25

L

discrete delay line

G=?kOhm

50

.W16 W31

5.6k

.C

G=?kOhm

TDC

calibration signals

.C

. .

G=-0.2

.

left channel

.L

W7

Shaper

W#25

G=0.8

L

ADC

.L .

Discriminator

fromanodewires

50ns

from cathode wires

5.6k

.C

W1

right channel

amplifier

G=?kOhm

W#7

. L

5.6k

L Rw7 w16 w25calibrationpulses

10 ns±1%

TDC

ADC

X ≈ GX ( tL – GRLtR - t0 )

Analog constant-fraction shaping (to reduce time-walk) : front-end

TDC LeCroy 2228A (11 bit, 250 ps) ADC LeCroy 2249A Extternal NIM discriminators LeCroy 623 Custom calibration pulser

4 mm

D


ITEP BPCs in H6 beam line• two “stations” of 2 BPCs: near & far • an auxiliary mid-station with 4 “old” BPCs (300 μ resolution) • advantages of arranging BPCs in pairs:

• better space resolution (<100 μ, important for the near

station!)• δ-electron rejection (see below) • easier cabling

Zbeam

X Y X Y X YX Y

CH#1 CH#2 CH#3 CH#4

27000mm 100mm

Y

ZX

27 m2.2 m

B9 1.6 m

cryostat

“old” ITEP BPCs

X Y X Y


Space resolution has been studied in dedicated test

beam measurements, confirmed in H6: σ = 110-200 μ, depending on the hit position.

σ is ~constant across the measurement direction (across anodes) and deteriorates towards the edge cathode wires

MC shows that the tails of dX >1 mm are due to δ-electrons

The cut |dX|<1 mm has ε=97% (|dX|<0.5 mm: ε=95%) and largely eliminates δ-electrons

x

σX (mm)

0.1

0.2

dX (meas-pred), mm


BPC calibration Internal calibration (GX, to) – with an external pulser, at start of run GRL and G adjustment, mutial alignment of all chambers: with beam tracks For most of the BPCs, the calibration drift during FCal TB runs was negligible.

Exeptions: ch. 1 and one case of a faulty TDC

Bad TDC

to (Y1)

to (Y5)

GX (Y1)


>1 track Can rely on external counters… trust but

verify! tR + tL for single tracks has a lower limit

= Σ line delay Anode signal amplitude

Summary ITEP BPCs: new beam chambers, designed for high-accuracy

measurements No visible ageing effects robust, easy to maintain and read-out

Multi-track rejection


BPC resolution: H6 datadX=X(1)-X(2), 30x40 mm2 dY=X(5)-X(6), 60x60 mm2

σ56≈190 μ

X

X

Y

Y

σ12≈150 μ


7.5mm

D C B A X

YImpact point prediction

Fcal1

Y, cmX, cm

Fcal

-1 re

spon

se, A

DC

cou

nts

ITEP Beam Chambers P.Gorbunov (U. of Toronto and ITEP, Moscow)

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