1. Development and study of Glass Resistive Plate Chambers Satyanarayana Bheesette Roll number: 04412701 Supervisors Prof Raghava Varma, IIT Bombay Prof Naba Mondal, TIFR Mumbai

2. Satyanarayana Bheesette Ph.D Credit Seminar November 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

3. Satyanarayana Bheesette Ph.D Credit Seminar November 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 ( e      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.

4. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 4 Proposed INO detector Magnetised iron calorimeter Iron RPC 140 layers RPC dimension: 3m X 2m No of chambers: 11K No of channels: 220K No of TDC channels: 3K 35KTons

5. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 5 Principle of operation of a RPC V-I model Each discharge locally deadens the RPC. The recovery time is approximately

6. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 6 Our prototype designs: Single gap Gas inlet HV terminals Graphite coat Gas outlet Spacer Two versions

7. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 7 Our prototype designs: Double gap Double gap RPC for better detection efficiencies

8. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 8 Jigs for RPC fabrication A glued RPC Resistivity measurement jig A finished small area RPC RPC fabrication jig Glue and dispensers Glass handlers

9. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 9 Gas mixing and flow control unit Gas mixing unit Flow monitor

10. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 10 Schematic of Cosmic ray muon trigger

11. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 11 Cosmic ray muon telescope setup Mounting structure for flexible and precise telescope alignment Paddle alignment detail

12. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 12 Schematic of data acquisition system

13. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 13 Data acquisition system electronics NIM CAMAC

14. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 14 V-I characteristics Small RPC Large RPC

15. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 15 Typical RPC pulse profile RPC pulse Muon trigger

16. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 16 Noise rate and efficiencies

17. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 17 Charge performance

18. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 18 Timing performance

19. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 19 Charge-time linearity

20. Satyanarayana Bheesette Ph.D Credit Seminar November 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 SF 6 instead of Freon preferred

21. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 21 Controlled humidity test Carlo Gustavino et al, LNGS

22. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 22 AFM images of damaged electrodes 2  scans10  scans Damaged electrodes Raw glass ¶ 500nm structures of 100nm thick seen in the images

23. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 23 SEM image of damaged electrode 6  scan 2  scan Damaged electrode Fluorine: 38% Raw glass Fluorine: 4%

24. Satyanarayana Bheesette Ph.D Credit Seminar November 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

25. Backup slides

26. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 26 RPCs of modern designs Multi gap Hybrid RPCMicro RPC 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

27. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 27 Telescope stability monitoring

28. Satyanarayana Bheesette Ph.D Credit Seminar November 2004 28 Preliminary cross-talk measurements Gas MixtureTele window (mm) Cross talk (%) 62:8:30106.8 62:8:30156.7 62:8:30206.2 57:8:35206.5 52:8:40205.9 46:8:46206.3

29. Satyanarayana Bheesette Ph.D Credit Seminar November 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.