the dynamic behaviour of resistive plate chambers
DESCRIPTION
The dynamic behaviour of Resistive Plate Chambers. Presented by Marcello Abbrescia University and INFN - Bari - Italy. VII Workshop on Resistive Plate Chambers and related detectors. Clermont-Ferrand FRANCE October 20-22, 2003. x sat. Exponential growth. Saturation. . “Drift”. - PowerPoint PPT PresentationTRANSCRIPT
The dynamic behaviour of Resistive Plate Chambers
The dynamic behaviour of Resistive Plate Chambers
Presented by
Marcello Abbrescia University and INFN - Bari - Italy
VII Workshop on Resistive Plate Chambers and related detectors
Clermont-Ferrand FRANCEOctober 20-22, 2003
The story up to nowThe story up to now
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
satsat
wxx
we
ind xg
xgVMeMnV
g
qq sat
10
0
Exponential growth Drift
Exponential growthxsat
Saturation
“Drift”
Many quantities in the formula above are themselves stochastic variables.
The induced charge is the “convolution” of all these variables.A Monte Carlo rather elaborated
When saturation does not playWhen saturation does not play
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
Gap: 2 mm
Gap: 9 mm
Charge Spectra shape: these are the most fundamental information you can get
1
Rqqind
Comparison between Monte-Carlo predictions and experimental data
Freon rich mixture
Argon rich mixture
: primary cluster density (from 3 to 5 cl/mm): 1st Townsend “effective” coefficient
...and when saturation becomes important...and when saturation becomes important
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
HV=9.2 kV
SimulationExperiment
Experimental data from Camarri et al., NIM A 414 (1998) 317-324
Gas mixture: C2H2F4/C4H10 97/3 + SF6 2%Input for simulation: Colucci et al., NIM A 425 (1999) 84-91
This is not a fit!
...and when saturation becomes important...and when saturation becomes important
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
HV=9.4 kV
SimulationExperiment
Experimental data from Camarri et al., NIM A 414 (1998) 317-324
Gas mixture: C2H2F4/C4H10 97/3 + SF6 2%Input for simulation: Colucci et al., NIM A 425 (1999) 84-91
This is not a fit!
...and when saturation becomes important...and when saturation becomes important
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
HV=9.5 kV
SimulationExperiment
Experimental data from Camarri et al., NIM A 414 (1998) 317-324
Gas mixture: C2H2F4/C4H10 97/3 + SF6 2%Input for simulation: Colucci et al., NIM A 425 (1999) 84-91
Inefficiency peak Saturation
broad peak
This is not a fit!
...and when saturation becomes important...and when saturation becomes important
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
HV=9.7 kV
SimulationExperiment
Experimental data from Camarri et al., NIM A 414 (1998) 317-324
Gas mixture: C2H2F4/C4H10 97/3 + SF6 2%Input for simulation: Colucci et al., NIM A 425 (1999) 84-91
Inefficiency peak
Saturation broad peak
This is not a fit!
...and when saturation becomes important...and when saturation becomes important
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
HV=9.9 kV
SimulationExperiment
Experimental data from Camarri et al., NIM A 414 (1998) 317-324
Gas mixture: C2H2F4/C4H10 97/3 + SF6 2%Input for simulation: Colucci et al., NIM A 425 (1999) 84-91
Inefficiency peak
Saturation broad peak
This is not a fit!
...and when saturation becomes important...and when saturation becomes important
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
HV=10.1 kV
SimulationExperiment
Experimental data from Camarri et al., NIM A 414 (1998) 317-324
Gas mixture: C2H2F4/C4H10 97/3 + SF6 2%Input for simulation: Colucci et al., NIM A 425 (1999) 84-91
Inefficiency peak
Saturation broad peak
This is not a fit!
The “single cell” modelThe “single cell” model
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
None of the simulations up to now take into account the
role of the bakelite resistivity ... we could be simulating metal or insulating electrodes
g
bCCR rbgbb 2222 0
g
bCCR rbgbb 2222 0
Recovery time independent of the cell dimension ...
Cg
RbCb
A few numbers:
typical avalanche radius: 100 mtypical avalanche charge: 1 pCtypical external charge contained in 100 m: 10 pC
What happens in the “single cell”What happens in the “single cell”
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
Applied HV
High HV “at start”
Big pulses
cl
d
n
jj
jtvedind Mneqti
10)(
wEv
t
ext eHVtHV 1)(
=1500 ms
There is a sort of feedback ...
Area of the cell = 1 mm2
5 10 11 cm
=20 Hz
Effective HV vs. rateEffective HV vs. rate
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
Applied HV
10 Hz
13 Hz
20 Hz
The effective HV diminishes and its distribution is broader.
(...until HVeff is too low)
Two consequences:•lower HV at high rate•greater HV variations at high rate
Efficiency vs. rateEfficiency vs. rate
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
From C. Bacci et al., NIM A 352(1995) 552-556
Experiment
Simulation
4 1010 cm
8 1010 cm
Cut-off rate of the experimental efficiency well simulated: slightly higher value of resistivity needed (significant?)
Rate capability dependancesRate capability dependances
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
HV=10100 V
HV=9800 V
HV=9600 V
HV=9200 V
independent of applied voltage
4 1011 cm
1012 cm
8 1010 cm
1011 cm
strongly dependent on resistivityTrue in the “single cell” model only
Cut-off rate
4 1011 cm HV=10100 V
Rate capability in streamer modeRate capability in streamer mode
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
From R. Arnaldi et al., NIM A 456(2000) 73-76
Exp. streamer
Exp. avalanche
Simulation streamer
Streamer charge distribution has been simulated also by “artificially” multiplying by 10 both avalanche charge, and area on the electrodes.
Cut off rate reproduced also in the streamer case.
8 1010 cm
Efficiency rate dependance different.
Efficiency vs. HV and rateEfficiency vs. HV and rate
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
Data from G. Aielli et al., NIM A 478(2002) 271-276
Simulation
Experimental
~ 1.5 kHz/cm2
~ 2 Hz/cm2 Very good agreement
At high rate the shape of the simulated efficiency curve seem to change and differ from the experimental one.
1ln
1
1 A
qg thr
e
g
MnVqA we
0
Time resolutionTime resolution
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
Data from C. Bacci et al., NIM A 352(1995) 552-556
0.2 kHz/cm2
=0.9 ns 1 kHz/cm2
=1.2 ns 4 kHz/cm2
=1.6 ns
Simulated Experimental
General behaviour well reproduced ... Simulated time resolutions slightly less than experimental.
1. Systematics on drift velocity2. “Instrumental” effects not reproducedPossible Reasons
Time delay and resolution vs. rateTime delay and resolution vs. rate
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
Experimental (arbitary zero)
Simulation (absolute scale) Experimental Simulation
Time Delay Time resolution
4 ns3.8 ns
The absolute scale of the simulation refers to the passage of the ionising particle.
75.1
2/
2/
2.0
4
cmkHzt
cmkHzt
77.1
2/
2/
2.0
4
cmkHzt
cmkHzt
The future: The multi cell modelThe future: The multi cell model
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
The area of the inefficiency cell increases as the bakelite surface resistivity decreases.
vol
sup
“large” “small”vol
sup
avalanche
“Surface” coupling resistors
Cg
RbCb
Rs,b
The net results is that the current flows not only in the “central” cell, but also in the neighbouring ones.
ConclusionsConclusions
RPC 2003 Clermont-Ferrand October 20th, 2003RPC 2003 Clermont-Ferrand October 20th, 2003
Marcello Abbrescia - University of BariMarcello Abbrescia - University of Bari
Even the single cell model reproduces well the efficiency and time resolution vs. rate.
The role of resistivity and collected charge seems to be clear.
Charge spectra are well understood.
Slight differences remain, both for the “static” and the “dynamic” case ... could be due to• uncertainty in gas (and other) parameters.• possible refinements of the model.
It is the first time the role of resistivity is taken into account in simulation of Resistive Plate Chambers ... The model of the dry water becomes wet.