Transcript Development and study of Glass Resistive Plate Chambers

Results from development of
Glass RPCs for INO detector
B.Satyanarayana
(For INO Collaboration)
TIFR, Mumbai
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Plan of the presentation
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Introduction
Principle of operation of a glass RPC
Overview of the field
Our prototype designs and fabrication
RPC gas mixtures and gas system
Cosmic ray muon telescope
Data acquisition system
Preliminary results
RPC aging problem
Future work plan
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
2
Introduction
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Neutrinos are one of the fundamental particles of matter.
Electrically neutral and were initially thought to be mass less.
Three types or flavors (ne,nm,nt) of neutrinos known.
Recent evidence indicates that neutrinos have mass and also
experience mixing among these flavors.
Neutrino oscillations can explain the discrepancy between theory
and observations about its flux; can be used to estimate its mass.
Pioneering experiments at the KGF underground laboratories.
Formation of Indian Neutrino Observatory (INO) collaboration.
Feasibility studies for setting up of a neutrino experiment in India
is in progress.
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Proposed INO detector
Magnetised iron
calorimeter
 RPC dimension: 3m X 2m
 No of chambers: 11K
 No of channels: 220K
RPC
Iron
140 layers
 No of TDC channels: 3K
35KTons
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Principle of operation of a RPC
V-I model
Two 2mm thick float glasses
Separated by 2mm spacers
2mm thick spacer
Pickup strips
Each discharge locally deadens the RPC.
The recovery time is approximately
  l    A 
t  RC   
  
 A  l 
t ( x 1010 ) x 4 x (8.85x 10-12 )  2 s
Glass plates
Graphite coating on the outer surfaces of glasses
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Our prototype designs: Single gap
Gas
inlet
Two versions
Spacer
Graphite
coat
Gas
outlet
HV terminals
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Our prototype designs: Double gap
Double gap RPC for better
detection efficiencies
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Jigs for RPC fabrication
Glass
handlers
Resistivity
measurement
jig
Glue and
dispensers
RPC
fabrication
jig
A finished
small area
RPC
A glued
RPC
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Gas mixing and flow control unit
Flow monitor
Gas mixing unit
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Schematic of Cosmic ray muon trigger
m
P1
Glass RPC under test
P2
P3
P5
P4
P6
Muon Trigger = P1  P2  P3  P4  P5  P6
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Cosmic ray muon telescope setup
Mounting structure for flexible
and precise telescope alignment
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Paddle alignment detail
Nov 29 - Dec 3, 2004
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Schematic of data acquisition system
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Data acquisition system electronics
NIM
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
CAMAC
Nov 29 - Dec 3, 2004
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V-I characteristics
Small RPC
Large RPC
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Typical RPC pulse profile
RPC pulse
Muon trigger
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Noise rate and efficiencies
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Charge performance
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Timing performance
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Charge-time linearity
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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RPC aging problem
 Drop in efficiency,
increase in noise rate and
chamber current seen
after a few weeks of
continuous operation
 Reports in the literature
(Monolith, Belle etc)
 Moister contamination in
Freon gas, the culprit?
 Use of SF6 instead of
Freon preferred
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Controlled humidity test
Carlo Gustavino et al, LNGS
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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AFM images of damaged electrodes
2m scans
Damaged
electrodes
10m scans
Raw
glass
Damaged
electrodes
Raw
glass
¶ 500nm structures of 100nm thick seen in the images
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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SEM image of damaged electrode
6m scan
Damaged electrode
Fluorine: 38%
2m scan
Raw glass
Fluorine: 4%
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Future work plan
 Systematic study of RPC stability problem
 Fabrication of more large area RPCs and studies
 Detailed studies on timing, spatial resolution, cross-talk
 Optimization of detector gas composition
 INO prototype detector; needs about 16 large area RPCs
 Performance studies of prototype detector; comparison
of results with those from simulation studies
 RPC Parameter inputs for electronics and data
acquisition system design
 Full pledged RPC device simulations
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Backup slides
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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RPCs of modern designs
Hybrid RPC
Micro RPC
Multi gap
Applications in HEP research
 Cosmic ray experiments: EAS-Top, Cover-Plastex, Argo, Auger
 Accelerator based experiments: Belle, Babar, Star, Harp
 Future experiments: Alice, ATLAS, CMS, LHCb
 Medical applications etc
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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Telescope stability monitoring
280000
Telescope paddel rates
260000
240000
220000
P1
P2
200000
P3
180000
P4
160000
140000
120000
100000
1
2
3
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8
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10
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Time, Hours
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
27
Preliminary cross-talk measurements
Gas Mixture Tele window
Cross talk (%)
(mm)
62:8:30
10
6.8
62:8:30
15
6.7
62:8:30
20
6.2
57:8:35
20
6.5
52:8:40
20
5.9
46:8:46
20
6.3
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
28
Recovery of a damaged RPC
 Purging with pure Argon
at high flow rate.
 Bubbling pure Argon
through pure ethyl
alcohol.
 Bubbling pure Argon
through 3% Ammonia
solution for 24 hours with
high voltage off.
 Recovers efficiency and
brings down noise rate.
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata,
Nov 29 - Dec 3, 2004
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