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Space Charge Compensation and Electron Cloud Effects in Modern Dottorato di Ricerca in Fisica degli Acceleratori Ciclo XXVIII Space Charge Compensation and Electron Cloud Effects in Modern High Intensity Proton Accelerators Thesis advisor Candidate Prof. Luigi Palumbo Roberto Salemme Supervisors Dr. Dirk Vandeplassche (SCK•CEN) Dr. Vincent Baglin (CERN) October 2016 Copyright ©2016 Roberto Salemme All rights reserved Preface The present work deals with two of the numerous challenges of modern and future particle accel- erators targeting high intensity proton beams: the beam dynamics of low energy intense beams in linear accelerators, which is influenced by space charge, and the beam induced multipacting causing the so called electron cloud in high energy circular accelerators. These themes have been the subject of my privileged involvement with two projects at the forefront of accelerator science and technology in the years 2013-2016. Space charge and its compensation was at the basis of the design of the Low Energy front-end of the Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) accelerator project, which I joined in the period 2013-2014 in quality of Accelerator System Engineer at the Studiecentrum voor Kernenergie - Centre d'Etude´ de l'´energie Nuclaire (SCK•CEN), based in Mol and Louvain-la-Neuve, Belgium. The study of electron cloud effects and their mitigation comes from the involvement (since 2014) in the High Luminosity upgrade project of the Large Hadron Collider (LHC), in quality of Research Fellow of the Euro- pean Organization for Nuclear Research (CERN) and in charge of the COLD bore EXperiment (COLDEX), in Meyrin, Switzerland. The realization of this work is essentially based in the trust, encouragement and support of the people surrounding the professional and personal course of my doctoral undertaking, which was equally important, if not superior, to my dedication. I acknowledge the faithful guidance of Prof. Luigi Palumbo, an extraordinary person who combines the passion for his work with the generous aperture and altruism toward his students. I particularly owe him the proposal and successful completion of this work. I thank Prof. P. Bagnaia and Prof. R. Faccini, coordinators of the PhD programme in Accelerator Physics at Sapienza University of Rome during the cycle XXVIII, for their guidance and patience in dealing with the assignments and deadlines of this PhD. I warmly acknowledge the supervision of Dr. Dirk Vandeplassche, Head of the Accelerator Design and Tests (ADT) Unit at SCK•CEN, with whom I had the privilege to work with, not only for his professional leadership and for sharing his profound knowledge in an incredible extent of fields of accelerator science and technology, but also for his constructive and friendly approach in everyday life. I equally thank Dr. Luis Medeiros Rom~ao,MYRRHA Linear Accelerator R&D man- ager, who constantly and trustfully provided support and motivation to my work at SCK•CEN, in combination with an exceptional human relationship. I would like to thank Dr. H. A. Abderrahim, head of the MYRRHA project and Deputy Director General of SCK•CEN, who welcomed me in the MYRRHA project under his direction. I am grate to Dr. M. Loiselet and the whole Centre de Ressources du Cyclotron of the Universit´eCatholique de Louvain, for hosting and providing assistance to the RFQ@UCL programme, of which I have been technically responsible. I acknowl- edge the fruitful collaboration and friendly support of many of the collaborators to the MYRRHA project with whom I was delighted to work, in particular J.-L. Biarrotte (CNRS-IN2P3/IPNO), F. Bouly, M. Baylac, D. Bondoux (LPSC - UniversitˇeGrenoble-Alpes, CNRS/IN2P3), D. Uriot (CEA-DSM/IRFU/SACM), D. Mader, H. Podlech (IAP Frankfurt), J.-P. Carneiro (FNAL), R. Modic (Cosylab), X. Donzel, G. Gaubert (Pantechnik), F. Davin (UCL/CRC). A warm thank you to F. Belloni, A. Ottonello, D. Bisogni (SCK•CEN) for the nice time spent in Mol. I express sincere gratitude to Dr. Vincent Baglin, former leader of the LHC Beam Vacuum (LBV) section and now at the head of the Vacuum Studies and Measurements (VSM) section, while coordinator of the Work Package (WP) 12 - Vacuum & Beam Screen - in the HL-LHC project, for his guidance as supervisor at CERN. From him I inherited the COLD bore EXperiment, which he led in the 1997-2005 period. I owe most of the knowledge in the field of electron cloud and 4 cryogenic vacuum systems to his guide and experience, which boasts participation to the design, construction, commissioning and operation of the LHC vacuum system. I equally thank him for sharing with me his scientific and diligent approach to the field of the experimentation, in which he has shown me the talent of mixing rigorousness and never-ending curiosity. I am particularly indebted to Dr. Giuseppe Bregliozzi, now leader of the Beam Vacuum Operation (BVO) section, who has been in charge for the recommissioning of the COLD bore EXperiment in 2013-2014. I received the COLD bore EXperiment from his hands in great shape, and it is mostly thanks to his commitment and expertise that the experiment is so successful and fruitful since 2014. I am grateful and honoured of the encouragement of Dr. Paolo Chiggiato, head of the Vacuum, Surfaces and Coatings group at CERN. His keen passion in sharing his unique and profound knowledge in the field of vacuum science and technology is truly exemplar. I am grateful for the constant, friendly, support of Dr. R. Kersevan and Dr. M. Taborelli, from whom I often profited of expert advice and genuine interest. I am indebted to Dr. R. Cimino (INFN/LNF) for sharing with me his infinite knowledge in surface science and electron cloud. A special thank you to A. Marraffa, with whom I really had a great time once arrived at CERN. I would like to acknowledge the competent and professional support of a incredible number of colleagues at CERN, especially from the groups TE/VSC, TE/CRG, BE/OP, BE/ABP, TE/EPC, EN/ICE, EN/MME and from the consortium AL40-30, who, thanks for their true commitment, have allowed me to get out most of the results presented in this Thesis. I would like to specifically acknowledge the help of B. Jenninger and A. Gutierrez, who have put their best experience and competence in assisting me in the endless hours on the field of the Super Proton Synchrotron accelerator. I am indebted to G. Iadarola for his assistance with the pyECLOUD code. A special thanks to the guys of BE/OP/SPS with whom I spent several nights in the CERN Control Centre (CCC) during the beam runtime. This work is the resume of an authentic success which was possible thanks to all these people. On a equal footing, I wish to express my sincere and respectful gratitude to my family and friends, which have upheld my soul ensuring a strong sustain to my growth. A particular dedication goes to my beloved father and mother, Antonio and Manuela, who have made me the person I am today. Besides this dissertation, I had the honour of producing the following scientific production (in chronological order): 1. R. Salemme, L. Medeiros Rom~ao,D. Vandeplassche, J.-P. Carneiro, J.-L. Biarrotte, M. Baylac, D. Uriot, H. Podlech, \The R&D@UCL program in support of the MYRRHA lin- ear accelerator", Proceedings of Technology and Components of Accelerator-Driven Sys- tems (TCADS-2), OECD Nuclear Energy Agency, Second International Workshop - Nantes, France, May 2013 2. J.-P. Carneiro, L. Medeiros Rom~ao,R. Salemme, D. Vandeplassche, J.-L. Biarrotte, F. Bouly, D. Uriot, \Approach of a failure analysis for the MYRRHA linac", Proceedings of Technology and Components of Accelerator-Driven Systems (TCADS-2), OECD Nuclear Energy Agency, Second International Workshop - Nantes, France, May 2013 3. R. Salemme, L. Medeiros Rom~ao,D. Vandeplassche, \The MYRRHA linear accelerator R&D program", Proceedings of AccApp 2013, Eleventh International Topical Meeting on Nuclear Applications of Accelerators - Bruges, Belgium, August 2013 4. D. Vandeplassche, L. Medeiros Rom~ao,R. Salemme, J.-L. Biarrotte, F. Bouly, J.-P. Carneiro, \Toward a virtual accelerator control system for the MYRRHA LINAC", 5th International Particle Accelerator Conference (IPAC'14) - Dresden, Germany, June 2014 5. R. Modic, G. Pajor, K. Zagar, L. Medeiros Rom~ao,R. Salemme, D. Vandeplassche \Control system design considerations for MYRRHA ADS", 5th International Particle Accelerator Conference (IPAC'14) - Dresden, Germany, June 2014 6. R. Salemme, L. Medeiros Rom~ao,D. Vandeplassche, D. Uriot, J.-L. Biarrotte, M. Baylac, D. Bondoux, F. Bouly, J.-M. De Conto, E. Froidefond, \Design progress of the MYRRHA low energy beam line", 27th Linear Accelerator Conference (LINAC14) - Geneva, Switzerland, September 2014 5 7. R. Salemme, V. Baglin, F. Bellorini, G. Bregliozzi, K. Brodzinski, P. Chiggiato, P. Costa Pinto, P. Gomes, A. Gutierrez, V. Inglese, B. Jenninger, R. Kersevan, E. Michel, M. Pezzetti, B. Rio, A. Sapountzis, \Recommissioning of the COLDEX experiment at CERN", 6th Inter- national Particle Accelerator Conference (IPAC'15) - Richmond, Virginia, USA, May 2015 8. R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan, \Amorphous carbon coat- ings at cryogenic temperatures with LHC type beams: first results with the COLDEX exper- iment", 6th International Particle Accelerator Conference (IPAC'15) - Richmond, Virginia, USA, May 2015 9. R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan, \Vacuum performance of amorphous carbon coating at cryogenic temperature with presence of proton beams", 7th International Particle Accelerator Conference (IPAC'16)
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