Transcript No Slide Title

Performance of a Multigap RPC
prototype for the LHCb
Muon System
E. Polycarpo
On behalf of LHCb MRPC Working Group
CERN/LAPE
28/10/99
V Workshop on RPCs and related
detectors
1
Outline
 Introduction
 Characteristics of the prototype
 Description of the testbeam setup
 Results
 Conclusion
28/10/99
V Workshop on RPCs and related
detectors
2
Introduction: LHCb experiment
Muon Station M2
Angular coverage ~ 10 mrad to 300 mrad
28/10/99
V Workshop on RPCs and related
detectors
3
Introduction : LHCb Muon System
 Provides :
 Muon identification
 L0 trigger
 Requires:
 reasonable momentum resolution
 good time resolution
correct bunch-crossing identification
 good performance at high rate
~ 1.6 -4 kHz/cm2 for 2 -5x1032 cm-2s-1 (q > 150 mrad)
28/10/99
V Workshop on RPCs and related
detectors
4
Characteristics of the MRPC
prototype
Ground plane (copper foil)
Honeycomb
HV plane
(graphite layer)
Readout Strips  1.3 cm wide and 24 cm long (1.5 cm readout pitch)
connected to ASD8-B chip
0.7 mm thick Melamine-Phenolic-Melamine plates
r = 4x 10 12 W cm
Gas mixture :
96 % C2H2F4 / 3%iso-C4H10 / 1%SF6
0.7 mm gas gaps
28/10/99
V Workshop on RPCs and related
detectors
5
Experimental Set-up at CERN
PS and SPS
1.0 cm pitch
T itle:
ps/ps2dprof.eps
Creator:
HIGZ Versi on 1.25/05
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
Hodoscope (8x8)
Scintillator 20x20 cm2
Scintillator 15x15 cm2
MRPC Prototype
28/10/99
V Workshop on RPCs and related
detectors
6
Results - Efficiency at CERN PS
~ 3 GeV/c p - beam
T itle:
ps/rpc 99may1_zoom.eps
Creator:
HIGZ Versi on 1.25/05
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
• Shift of the knee of the plateau:
voltage drop across the plates
•Spill duration : ~ 400 ms
• Relaxation time t ~re0er ~ O (1 s)
 Overestimation of efficiency
at high rates
28/10/99
V Workshop on RPCs and related
detectors
7
Efficiency vs SPS burst time
120 GeV/c p - beam
Two effects :
• rate variation
• relaxation time
28/10/99
V Workshop on RPCs and related
detectors
8
Gamma Irradiation Facility
108 cm
28/10/99
V Workshop on RPCs and related
detectors
9
Measurement of Rate
• Effective rate (ER):
Fit of Dt distribution
T itle:
/afs /cern.c h/user/p/pol ye/latex/rpc99/gdt.eps
Creator:
HIGZ Versi on 1.25/05
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
AF =100
• Photon Rate:
Rg = 740 GBq x 0.85 x 0.5 x (1/4pd2) x eg x 1/AF
• Measured Photon Rate:
R’g = ER (AF) - ER(without source)
•Fit of R’g to Rg :
eg ~ 1/200 ~ #gaps/800
28/10/99
V Workshop on RPCs and related
detectors
10
GIF Rate Capability
T itle:
ps/ratecap1.eps
Creator:
HIGZ Versi on 1.25/05
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
• Efficiency corrected for probability of
spurious hit in the time window of 15 ns
(~ .01 %)
• 97% efficiency at 18 kV for ~ 1.9 kHz/cm2
28/10/99
V Workshop on RPCs and related
detectors
11
Timing Properties
T itle:
gifti prop.eps
Creator:
HIGZ Versi on 1.25/05
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
Time walk: ~ 1 ns/kHz/cm2
Time resolution (sigma of gaussian fit) : 1.5 ns to 1.9 ns
28/10/99
V Workshop on RPCs and related
detectors
12
Cross-talk and Noise
1.2 kHz/cm2
T itle:
/afs /cern.c h/user/p/pol ye/latex/rpc99/cs vs hv25.eps
Creator:
HIGZ Versi on 1.25/05
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
T itle:
/afs /cern.c h/user/p/pol ye/publ ic /burkhard/gifcs izvs
Creator:
HIGZ Versi on 1.25/05
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded i n i t.
Comment:
T his EPS pic ture wi ll pri nt to a
Pos tScri pt printer, but not to
other types of printers.
Cluster size at operating voltages ~ 1.2 strips small cross-talk
High noise rate ~ 60 Hz/cm2
28/10/99
V Workshop on RPCs and related
detectors
13
Summary and Conclusions
 Measurements at three CERN facilities have been
performed, with emphasis on rate capability
 The description of the efficiency drop within the SPS
burst must take into account the significant variation
in the rate.
 In spite of high resistivity of the plates, the chamber
reaches 97 % efficiency for 1.9 kHz/cm2 in GIF
 Small cross-talk (1.2 strips/cluster), but high noise
rate (60 Hz/cm2)
 Timing properties match the LHCb requirements
28/10/99
V Workshop on RPCs and related
detectors
14
Rate capability requirement
 Background estimation in the LHCb muon stations:
PYTHIA as event generator
pathlength/volume as rate definition
1x10-5/cm2/interaction
MARS as simulation package
luminosity up to 5 x 10 32 cm-2s-1
additional safety factor of 2.5
4 kHz/cm2 @ 5 x 10 32 cm-2s-1
28/10/99
V Workshop on RPCs and related
detectors
15
Big Prototype
28/10/99
V Workshop on RPCs and related
detectors
16
Sensitive Area : 1.2x2.2 m2
28/10/99
V Workshop on RPCs and related
detectors
17
MRPC Prototype: 24x24 cm2
28/10/99
V Workshop on RPCs and related
detectors
18