Electronic Instrumentation STUDY OF FLOW AND CONTROL OF GAS MIXTURE FOR THE RESISTIVE PLATE CHAMBER (RPC) PERFORMANCE IN CLOSED LOOP SYSTEM A THESIS SUBMITTED FOR FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF Doctor of Philosophy By KALMANI SURESH DEVENDRAPPA Under the guidance of Dr. P. V. Hunagund Professor of Electronics FACULTY OF SCIENCE & TECHNOLOGY DEPARTMENT OF POST GRADUATE STUDIES & RESEARCH IN APPLIED ELECTRONICS, GULBARGA UNIVERSITY, KALABURAGI-585 106, KARNATAKA, INDIA April, 2018 ii Declaration I hereby declare that, the research work presented in the thesis entitled “STUDY OF FLOW AND CONTROL OF GAS MIXTURE FOR THE RESISTIVE PLATE CHAMBER (RPC) PERFORMANCE IN CLOSED LOOP SYSTEM” has been carried out by me, under the supervision of Dr. P. V. Hunagund, Professor, Department of Applied Electronics, Gulbarga University, Kalaburagi for the award of the degree of Doctor of Philosophy. Further, the results presented in this thesis have not been submitted in any University or Institute for the award of any other degree. Date: Kalmani Suresh Devendrappa Place: Kalaburagi (Research student) iii Declaration I declare that this written submission represents our ideas in my own words and where others’ ideas or words have been included, I have adequately cited and ref- erenced the original sources. I also declare that I have adhered to all principles of aca- demic honesty and integrity and have not misrepresented or fabricated or falsified any idea/data/fact/source in my submission. I understand that any violation of the above will be cause for disciplinary action by the Institute / University and can also evoke penal action from the sources which have thus not been properly cited or from whom proper permission has not been taken when needed. Place: Date: Kalmani Suresh Devendrappa (Research student) iv Acknowledgements I wish to place on record my deep sense of gratitude to my research guide Dr. P. V. Hunagund, Department of PG studies and Research in Applied Electronics, Kalaburagi for his initiative, motivation, constant encouragement, meticulous care, co-operation, guidance and valuable suggestions at all stages of my research work to bring out my investigations of research work in thesis form. The remarks and sugges- tions made by him throughout this work were very resourceful. My mentor Prof. Naba K. Mondal Former INO Project Director, TIFR Mumbai, is a lot more than just that to me. I have enjoyed working with him for the last 33 years in building several front-ranking high energy physics experiments. I am immensely inspired by his enthusiasm and encouragement in pursuing the research work. I would like to thank Profusely TIFR Director Prof. Sandeep Tribedi, Former Di- rector, Dean NSF, INO Project Director and the Former Chairperson of DHEP; Prof. Mustansir Barma, Prof. E. V. Sampathkumaran, Prof. Vivek Datar and Prof. B.S. Acharaya, respectively for permitting me to make use of the laboratory facilities at TIFR, Mumbai, for my higher studies. I am extremely grateful to Dr. S. R. Niranjana, Vice-Chancellor, Dr. E.T. Puttaiah, Former Vice-chancellor, Dr Dayanand Agsar, Registrar, Gulbarga University, Kala- burgi for their administrative help. I would like to thank and place on record, the Founder Professor and Chairman, Dean, Faculty of science, Member Syndicate, Late Dr. H.V. Ganganna who was my mentor at Post graduation. Moreover, I am very thankful to Mrs. Sudha Ganganna for her encouraging words to pursuing my higher studies leading to Ph.D. v I am thankful to Dr. R. L. Raibagkar, Professor and Chairman, Prof. S. N. Mulgi, and Prof. Pradeep M. Hadalgi; for their help, co-operation and valuable suggestions in completing my research work. I am extremely thankful to Dr. (Mrs.) Vani R.M, Professor and Head, Department of University Science and Instrumentation Center (USIC) for her fruitful discussions and encouragement throughout my research work. I wish to acknowledge for many useful discussions, with late Avinash Joshi (M/s Alpha Pneumatics, Mumbai), my guru on gas systems. I am also grateful to the authorities of Tata Institute of Fundamental Research, Mumbai and the Gulbarga University, Gulbarga, for providing me with all the facili- ties required for carrying out this research work. I am indebted to Prof. Sudeshna Banerjee, Prof. Gobinda Mujamdar, Prof. Shashi Dugad , Dr. Satyanarayana Bheesette, Dr. Sudeb. Bhattacharya, Dr. G. Rajasekaran, Dr. Y. P. Viyogi, Dr. Deepak Samuel, Dr. G. K. Padmashree, Dr. M. V. N. Murthy for their valuable suggestions and encouragement with the present work. I had opportunities to interact with many experts in the field. I wish to thank Prof. Rinaldo Santanico (INFN Roma), Dr. Archana Sharma (CERN), R. Guida, F. Hahn, Prof. Yoshio Hayashi and Prof. Saburao Kawakami (Osaka City University), Prof A. B. Pandit (ICT) and Rushikesh Shinde (VJTI). It is a pleasure to acknowledge Ravindra Ragunath Shinde, Piyush Verma, Man- dar Saraf, Pathaleswar, V Pavan Kumar and Manas Bhuyan for their immense help. A sincere vote of thanks to my TIFR, department colleagues, Professors; Shashi Dugad, Sunil Gupta, Tariq Aziz, Atul Gurtu, K. Sudhakar, Kajari Mazumdar, as well as S. R. Chendvankar, M. R. Patil and P. K. Mohanty for their help and encourage- ment throughout the period of this research work. vi I wish to thank the INO Electronics R&D Team Members Suresh Upadhya, K. C. Ravindran, Venkatesam Reddy, Nagaraj Panyam, Dipankar Sil, Yuvaraj E, N. Si- varamkrishana, Sarika Bhide, Shekhar Lahamge, Shobha Rao, B. K. Nagesh, and S. R. Joshi for their immense timely support and co-operation. I am thankful to timely technical help by Dinesh B. Ganure, Research student and thanks to Smt. Umadevi and late. Shri. Hanumant Doddamani, Department of Applied Electronics, Gulbarga University, for their ministerial support and co-operation. My sincere gratitude to the INO students, Suryanaraya Mondal, Peturaj and Apoorva Bhat, for their constructive suggestions on occasions of discussions, assis- tance on setting up the experiments. I would like to thank Santosh Chavan, Vishal Asgolkar, Ganesh Ghodake and Darshana Koli, who provided an admirable technical assistance in carrying out the experiments and also thank the DHEP, Department administrative staff namely Vidhya Lotankar and Minal Rane. I owe most of my accomplishments including this one, to my wife Smt. Kalpana and daughters; Ar. Rochan and Dr. Rasika. Due to my self-commitment towards end- less work, most often, I could not honor even the family commitments and end up be- ing a guilty witness to their endless patience and silent sacrifices. Last but not the least; I am very much grateful to those people whose names have not been mentioned here, but who have helped me directly or indirectly for the com- pletion of my research work. Kalmani Suresh Devendrappa vii Preface The India-based Neutrino Observatory (INO) collaboration plans to construct a large 50 K ton magnetized Iron tracking CALorimeters (ICAL) in the Bodhi hills, in the state of Tamil Nadu in an underground cavern. The key goal of this observatory is to detect, identify and evaluate the properties of omnipresent cosmic particles called Neutrinos. This giant particle experiment will use active large number (28,800) of gas based detectors called as Resistive Plate Chamber (RPC) of size (1.85 × 1.9) m2 each, filled with gas mixture media within which all action takes place during an event. The performance of the calorimeter relates to performance of individual detectors and in- cludes parameters such as efficiency of detection, sensitivity of measurement, opera- tional life of the individual detector. The other peripheral requirements like gas con- sumption, pollution caused by gas leaks and the DAQ system are of prime importance and are, in a way, connected with the overall performance. The numbers of RPCs in the ICAL experiment are 28,800; each has 128 channels (64 X-side and 64 Y-side) readout. Therefore DAQ has to process about 3.7 million channels on the arrival of predefined trigger criteria. The total quantity of mixed gas in the ICAL calorimeter RPCs is about 200 M3. The RPC use a gas mixture consisting of R134a (C2H2F4), I-butane (iC4H10) and Sul- phur Hexafluoride (SF6) in ratio of 95:4.5:0.5 respectively and the mixed gas is a non–flammable and are relative expensive. To maintain the detector performance and efficiency, the gas mixture is required to flow through the RPCs continuously, main- tains the composition of the gas mixture and applied HV as per the characteristics of each RPC. The flow rate parameter is to be optimized for a proto-type detector taking into the RPC performance tests. As the number of RPCs are large in number, letting viii the gas into atmosphere will contributes significantly to pollution and global warming and moreover the gas is expensive therefore it is mandatory to reuse the gas in the closed loop mode. In addition there will be logistic problems of taking this huge quan- tity of gas in and out of the underground experiment (cavern below 1 KM approxi- mately). A proto-type, PLC (Programmable Logic Controller –Siemens make) based Closed Loop gas recirculation System (CLS) is designed, which supports 12 RPCs stack of size (1.85 × 1.9) m2 each. This system is in operation for the last 4.5 years and several factor related to the changes in the periodic atmospheric pressure changes are addressed and the system is successfully functioning satisfactorily. The performance of the RPCs depend on environmental conditions (such as at- mospheric pressure, ambient temperature, humidity ), flow rate of gas mixture into the RPCs, quality of gas , the RPC input gas pressure, uniform resistivity of conductive coating on one surface of each glass, gap thickness etc. The purity of gas studies indi- cates a correlation between RPC performance and the quality of the gas mixture.