1. 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

2. Plan of the presentation
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

3. Introduction 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

4. Magnetised iron calorimeter
Proposed INO detector
RPC dimension: 3m X 2m
No of chambers: 11K
No of channels: 220K
No of TDC channels: 3K
Magnetised iron calorimeter
140 layers
Iron
RPC
35KTons
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

5. Principle of operation of a RPC
V-I model
Each discharge locally deadens the RPC. The recovery time is approximately
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

6. Our prototype designs: Single gap
Gas inlet
Two versions
Graphite coat
Spacer
Gas outlet
HV terminals
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

7. 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

8. 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

9. 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

10. Schematic of Cosmic ray muon trigger
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

11. Cosmic ray muon telescope setup
Mounting structure for flexible and precise telescope alignment
Paddle alignment detail
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

12. Schematic of data acquisition system
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

13. Data acquisition system electronics
NIM
CAMAC
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

14. V-I characteristics Small RPC Large RPC
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

15. Typical RPC pulse profile
Muon trigger
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

16. Noise rate and efficiencies
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

17. Charge performance
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

18. Timing performance
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

19. Charge-time linearity
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

20. 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

21. Controlled humidity test
Carlo Gustavino et al, LNGS
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

22. AFM images of damaged electrodes
2 scans
10 scans
Damaged electrodes
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

23. SEM image of damaged electrode
6 scan
2 scan
Raw glass Fluorine: 4%
Damaged electrode Fluorine: 38%
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

24. 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

25. Backup slides
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

26. Applications in HEP research
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

27. Telescope stability monitoring
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

28. Preliminary cross-talk measurements
Gas Mixture
Tele window
(mm)
Cross talk (%)
62:8:30 10
6.8 15
6.7 20
6.2
57:8:35
6.5
52:8:40
5.9
46:8:46
6.3
XVI DAE-BRNS High Energy Physics symposium, SINP, Kolkata, Nov 29 - Dec 3, 2004

29. 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