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)
CBT EC2 Planning meeting CERN 212-Nov-2003 P.Gorbunov
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)
CBT EC2 Planning meeting CERN 312-Nov-2003 P.Gorbunov
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
CBT EC2 Planning meeting CERN 412-Nov-2003 P.Gorbunov
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
CBT EC2 Planning meeting CERN 512-Nov-2003 P.Gorbunov
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
CBT EC2 Planning meeting CERN 612-Nov-2003 P.Gorbunov
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)
CBT EC2 Planning meeting CERN 712-Nov-2003 P.Gorbunov
>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
CBT EC2 Planning meeting CERN 812-Nov-2003 P.Gorbunov
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
CBT EC2 Planning meeting CERN 912-Nov-2003 P.Gorbunov
7.5mm
D C B A X
YImpact point prediction
Fcal1
Y, cmX, cm
Fcal
-1 re
spon
se, A
DC
cou
nts
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